SU-F-T-669: Commissioning of An Electronic Brachytherapy System for Targeted Mouse Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Culberson, W; Micka, J; Carchman, E

Purpose: The aim of this study was to commission the Xoft Axxent™ electronic brachytherapy (eBT) source and 10 mm diameter surface applicator with NIST traceability for targeted irradiations of mouse anal carcinomas. Methods: The Xoft Axxent™ electronic brachytherapy (eBT) and 10 mm diameter surface applicator was chosen by the collaborating physician as a radiation delivery mechanism for mouse anal carcinomas. The target dose was 2 Gy at a depth of 3 mm in tissue to be delivered in a single fraction. To implement an accurate and reliable irradiation plan, the system was commissioned by first determining the eBT source outputmore » and corresponding dose rate at a depth of 3 mm in tissue. This was determined through parallel-plate ion chamber measurements and published conversion factors. Well-type ionization chamber measurements were used to determine a transfer coefficient, which correlates the measured dose rate at 3 mm to the NIST-traceable quantity, air-kerma rate at 50 cm in air, for eBT sources. By correlating these two quantities, daily monitoring in the well chamber becomes an accurate and efficient quality assurance technique. Once the dose-rate was determined, a treatment recipe was developed and confirmed with chamber measurements to deliver the requested dose. Radiochromic film was used to verify the dose distribution across the field. Results: Dose rates at 3 mm depth in tissue were determined for two different Xoft Axxent™ sources and correlated with NIST-traceable well-type ionization chamber measurements. Unique transfer coefficients were determined for each source and the treatment recipe was validated by measurements. Film profiles showed a uniform dose distribution across the field. Conclusion: A Xoft Axxent™ eBT system was successfully commissioned for use in the irradiation of mouse rectal tumors. Dose rates in tissue were determined as well as other pertinent parameters to ensure accurate delivery of dose to the target region.« less

A comparison study on various low energy sources in interstitial prostate brachytherapy

PubMed Central

Bakhshabadi, Mahdi; Ghorbani, Mahdi; Knaup, Courtney; Meigooni, Ali S.

2016-01-01

Purpose Low energy sources are routinely used in prostate brachytherapy. 125I is one of the most commonly used sources. Low energy 131Cs source was introduced recently as a brachytherapy source. The aim of this study is to compare dose distributions of 125I, 103Pd, and 131Cs sources in interstitial brachytherapy of prostate. Material and methods ProstaSeed 125I brachytherapy source was simulated using MCNPX Monte Carlo code. Additionally, two hypothetical sources of 103Pd and 131Cs were simulated with the same geometry as the ProstaSeed 125I source, while having their specific emitted gamma spectra. These brachytherapy sources were simulated with distribution of forty-eight seeds in a phantom including prostate. The prostate was considered as a sphere with radius of 1.5 cm. Absolute and relative dose rates were obtained in various distances from the source along the transverse and longitudinal axes inside and outside the tumor. Furthermore, isodose curves were plotted around the sources. Results Analyzing the initial dose profiles for various sources indicated that with the same time duration and air kerma strength, 131Cs delivers higher dose to tumor. However, relative dose rate inside the tumor is higher and outside the tumor is lower for the 103Pd source. Conclusions The higher initial absolute dose in cGy/(h.U) of 131Cs brachytherapy source is an advantage of this source over the others. The higher relative dose inside the tumor and lower relative dose outside the tumor for the 103Pd source are advantages of this later brachytherapy source. Based on the total dose the 125I source has advantage over the others due to its longer half-life. PMID:26985200

A comparison study on various low energy sources in interstitial prostate brachytherapy.

PubMed

Bakhshabadi, Mahdi; Ghorbani, Mahdi; Khosroabadi, Mohsen; Knaup, Courtney; Meigooni, Ali S

2016-02-01

Low energy sources are routinely used in prostate brachytherapy. (125)I is one of the most commonly used sources. Low energy (131)Cs source was introduced recently as a brachytherapy source. The aim of this study is to compare dose distributions of (125)I, (103)Pd, and (131)Cs sources in interstitial brachytherapy of prostate. ProstaSeed (125)I brachytherapy source was simulated using MCNPX Monte Carlo code. Additionally, two hypothetical sources of (103)Pd and (131)Cs were simulated with the same geometry as the ProstaSeed (125)I source, while having their specific emitted gamma spectra. These brachytherapy sources were simulated with distribution of forty-eight seeds in a phantom including prostate. The prostate was considered as a sphere with radius of 1.5 cm. Absolute and relative dose rates were obtained in various distances from the source along the transverse and longitudinal axes inside and outside the tumor. Furthermore, isodose curves were plotted around the sources. Analyzing the initial dose profiles for various sources indicated that with the same time duration and air kerma strength, (131)Cs delivers higher dose to tumor. However, relative dose rate inside the tumor is higher and outside the tumor is lower for the (103)Pd source. The higher initial absolute dose in cGy/(h.U) of (131)Cs brachytherapy source is an advantage of this source over the others. The higher relative dose inside the tumor and lower relative dose outside the tumor for the (103)Pd source are advantages of this later brachytherapy source. Based on the total dose the (125)I source has advantage over the others due to its longer half-life.

Monte Carlo dosimetric characterization of the Flexisource Co-60 high-dose-rate brachytherapy source using PENELOPE.

PubMed

Almansa, Julio F; Guerrero, Rafael; Torres, Javier; Lallena, Antonio M

60 Co sources have been commercialized as an alternative to 192 Ir sources for high-dose-rate (HDR) brachytherapy. One of them is the Flexisource Co-60 HDR source manufactured by Elekta. The only available dosimetric characterization of this source is that of Vijande et al. [J Contemp Brachytherapy 2012; 4:34-44], whose results were not included in the AAPM/ESTRO consensus document. In that work, the dosimetric quantities were calculated as averages of the results obtained with the Geant4 and PENELOPE Monte Carlo (MC) codes, though for other sources, significant differences have been quoted between the values obtained with these two codes. The aim of this work is to perform the dosimetric characterization of the Flexisource Co-60 HDR source using PENELOPE. The MC simulation code PENELOPE (v. 2014) has been used. Following the recommendations of the AAPM/ESTRO report, the radial dose function, the anisotropy function, the air-kerma strength, the dose rate constant, and the absorbed dose rate in water have been calculated. The results we have obtained exceed those of Vijande et al. In particular, the absorbed dose rate constant is ∼0.85% larger. A similar difference is also found in the other dosimetric quantities. The effect of the electrons emitted in the decay of 60 Co, usually neglected in this kind of simulations, is significant up to the distances of 0.25 cm from the source. The systematic and significant differences we have found between PENELOPE results and the average values found by Vijande et al. point out that the dosimetric characterizations carried out with the various MC codes should be provided independently. Copyright © 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Radiation Parameters of High Dose Rate Iridium -192 Sources

NASA Astrophysics Data System (ADS)

Podgorsak, Matthew B.

A lack of physical data for high dose rate (HDR) Ir-192 sources has necessitated the use of basic radiation parameters measured with low dose rate (LDR) Ir-192 seeds and ribbons in HDR dosimetry calculations. A rigorous examination of the radiation parameters of several HDR Ir-192 sources has shown that this extension of physical data from LDR to HDR Ir-192 may be inaccurate. Uncertainty in any of the basic radiation parameters used in dosimetry calculations compromises the accuracy of the calculated dose distribution and the subsequent dose delivery. Dose errors of up to 0.3%, 6%, and 2% can result from the use of currently accepted values for the half-life, exposure rate constant, and dose buildup effect, respectively. Since an accuracy of 5% in the delivered dose is essential to prevent severe complications or tumor regrowth, the use of basic physical constants with uncertainties approaching 6% is unacceptable. A systematic evaluation of the pertinent radiation parameters contributes to a reduction in the overall uncertainty in HDR Ir-192 dose delivery. Moreover, the results of the studies described in this thesis contribute significantly to the establishment of standardized numerical values to be used in HDR Ir-192 dosimetry calculations.

Radiation response of industrial materials: Dose-rate and morphology implications

NASA Astrophysics Data System (ADS)

Berejka, Anthony J.

2007-08-01

Industrial uses of ionizing radiation mostly rely upon high current, high dose-rate (100 kGy/s) electron beam (EB) accelerators. To a lesser extent, industry uses low dose-rate (2.8 × 10-3 kGy/s) radioactive Cobalt-60 as a gamma source, generally for some rather specific purposes, as medical device sterilization and the treatment of food and foodstuffs. There are nearly nine times as many (∼1400) high current EB units in commercial operation than gamma sources (∼160). However, gamma sources can be easily scaled-down so that much research on materials effects is conducted using gamma radiation. Likewise, laboratories are more likely to have very low beam current and consequently low dose-rate accelerators such as Van de Graaff generators and linear accelerators. With the advent of very high current EB accelerators, X-ray processing has become an industrially viable option. With X-rays from high power sources, dose-rates can be modulated based upon accelerator power and the attenuation of the X-ray by the distance of the material from the X-ray target. Dose and dose-rate dependence has been found to be of consequence in several commercial applications which can employ the use of ionizing radiation. The combination of dose and dose-rate dependence of the polymerization and crosslinking of wood impregnants and of fiber composite matrix materials can yield more economically viable results which have promising commercial potential. Monomer and oligomer structure also play an important role in attaining these desirable results. The influence of morphology is shown on the radiation response of olefin polymers, such as ethylene, propylene and isobutylene polymers and their copolymers. Both controlled morphology and controlled dose-rate have commercial consequences. These are also impacted both by the adroit selection of materials and through the possible use of X-ray processing.

Dosimetric characterization and output verification for conical brachytherapy surface applicators. Part I. Electronic brachytherapy source

PubMed Central

Fulkerson, Regina K.; Micka, John A.; DeWerd, Larry A.

2014-01-01

Purpose: Historically, treatment of malignant surface lesions has been achieved with linear accelerator based electron beams or superficial x-ray beams. Recent developments in the field of brachytherapy now allow for the treatment of surface lesions with specialized conical applicators placed directly on the lesion. Applicators are available for use with high dose rate (HDR) 192Ir sources, as well as electronic brachytherapy sources. Part I of this paper will discuss the applicators used with electronic brachytherapy sources; Part II will discuss those used with HDR 192Ir sources. Although the use of these applicators has gained in popularity, the dosimetric characteristics including depth dose and surface dose distributions have not been independently verified. Additionally, there is no recognized method of output verification for quality assurance procedures with applicators like these. Existing dosimetry protocols available from the AAPM bookend the cross-over characteristics of a traditional brachytherapy source (as described by Task Group 43) being implemented as a low-energy superficial x-ray beam (as described by Task Group 61) as observed with the surface applicators of interest. Methods: This work aims to create a cohesive method of output verification that can be used to determine the dose at the treatment surface as part of a quality assurance/commissioning process for surface applicators used with HDR electronic brachytherapy sources (Part I) and 192Ir sources (Part II). Air-kerma rate measurements for the electronic brachytherapy sources were completed with an Attix Free-Air Chamber, as well as several models of small-volume ionization chambers to obtain an air-kerma rate at the treatment surface for each applicator. Correction factors were calculated using MCNP5 and EGSnrc Monte Carlo codes in order to determine an applicator-specific absorbed dose to water at the treatment surface from the measured air-kerma rate. Additionally, relative dose measurements of the surface dose distributions and characteristic depth dose curves were completed in-phantom. Results: Theoretical dose distributions and depth dose curves were generated for each applicator and agreed well with the measured values. A method of output verification was created that allows users to determine the applicator-specific dose to water at the treatment surface based on a measured air-kerma rate. Conclusions: The novel output verification methods described in this work will reduce uncertainties in dose delivery for treatments with these kinds of surface applicators, ultimately improving patient care. PMID:24506635

Conditioning of the 4 Curies Radium-226 Sealed Radiation Source in Thailand

DOE Office of Scientific and Technical Information (OSTI.GOV)

Punnachaiya, M.; Sawangsri, T.; Wanabongse, P.

This paper describes the conditioning of the 4 curies Radium-226 (Ra-226) sealed radiation source using as a teletherapy unit for cancer treatment in Thailand. The conditioning was under the International Atomic Energy Agency (IAEA) supervision and budgetary supports, comprised of 6 operational steps: the surface dose rate and actual dimension of radium unit measurements, the appropriate lead shielding design with IAEA approval, confirmation of radioactive contamination before conditioning (smear test and radon gas leakage test), transfer of radium source unit into the designed shielding, confirmation of radioactive contamination and dose rate measurement after conditioning, and transportation of Ra-226 conditioning wastemore » package to OAP interim waste storage. The Ra-226 unit was taken out of OAP temporary waste storage for the surface dose rate and the actual dimension measurements behind the 12 inches thick heavy concrete shielding. The maximum measured surface dose rate was 70 R/hr. The special lead container was designed according to its surface dose rate along the source unit which the maximum permissible dose limit for surface dose rate of waste package after conditioning at 2 mSv/hr was applied. The IAEA approved container had total weight of 2.4 ton. After the confirmation of radioactive contamination, Ra-226 source unit was transferred and loaded in the designed lead shielding within 2 minutes. The results of smear test before and after conditioning including radon gas leakage test revealed that there was no radioactive contamination. After conditioning, the surface dose rate measured on the top, bottom were 15,10 mR/hr and varied from 6 - 50 mR/hr around lead container. The Ra-226 conditioning waste package was safely transported to store in OAP interim waste storage. Total working time including the time consumed for radon gas leakage test was 3.5 hours. The total radiation dose received by 16 operators, were ranged from 1 - 69.84 {mu}Sv and the operational team completed the conditioning safely within the effective dose limit for occupational exposure of 50 mSv/year (200 {mu}Sv/day). (authors)« less

Impact of the vaginal applicator and dummy pellets on the dosimetry parameters of Cs-137 brachytherapy source.

PubMed

Sina, Sedigheh; Faghihi, Reza; Meigooni, Ali S; Mehdizadeh, Simin; Mosleh Shirazi, M Amin; Zehtabian, Mehdi

2011-05-19

In this study, dose rate distribution around a spherical 137Cs pellet source, from a low-dose-rate (LDR) Selectron remote afterloading system used in gynecological brachytherapy, has been determined using experimental and Monte Carlo simulation techniques. Monte Carlo simulations were performed using MCNP4C code, for a single pellet source in water medium and Plexiglas, and measurements were performed in Plexiglas phantom material using LiF TLD chips. Absolute dose rate distribution and the dosimetric parameters, such as dose rate constant, radial dose functions, and anisotropy functions, were obtained for a single pellet source. In order to investigate the effect of the applicator and surrounding pellets on dosimetric parameters of the source, the simulations were repeated for six different arrangements with a single active source and five non-active pellets inside central metallic tubing of a vaginal cylindrical applicator. In commercial treatment planning systems (TPS), the attenuation effects of the applicator and inactive spacers on total dose are neglected. The results indicate that this effect could lead to overestimation of the calculated F(r,θ), by up to 7% along the longitudinal axis of the applicator, especially beyond the applicator tip. According to the results obtained in this study, in a real situation in treatment of patients using cylindrical vaginal applicator and using several active pellets, there will be a large discrepancy between the result of superposition and Monte Carlo simulations.

Analysis of Potassium in Bricks--Determining the Dose Rate from {sup 40}K for Thermoluminescence Dating

DOE Office of Scientific and Technical Information (OSTI.GOV)

Musilek, Ladislav; Polach, Tomas; Trojek, Tomas

2008-08-07

Thermoluminescence (TL) dating is based on accumulating the natural radiation dose in the material of a dated artefact (brick, pottery, etc.), and comparing the dose accumulated during the lifetime of the object with the dose rate within the sample collected for TL measurement. Determining the dose rate from natural radionuclides in materials is one of the most important and most difficult parts of the technique. The most important radionuclides present are usually nuclides of the uranium and thorium decay series and {sup 40}K. An analysis of the total potassium concentration enables us to determine the {sup 40}K content effectively, andmore » from this it is possible to calculate the dose rate originating from this radiation source. X-ray fluorescence (XRF) analysis can be used to determine the potassium concentration in bricks rapidly and efficiently. The procedure for analysing potassium, examples of results of dose rate calculation and possible sources of error are described here.« less

A generic high-dose rate {sup 192}Ir brachytherapy source for evaluation of model-based dose calculations beyond the TG-43 formalism

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ballester, Facundo, E-mail: Facundo.Ballester@uv.es; Carlsson Tedgren, Åsa; Granero, Domingo

Purpose: In order to facilitate a smooth transition for brachytherapy dose calculations from the American Association of Physicists in Medicine (AAPM) Task Group No. 43 (TG-43) formalism to model-based dose calculation algorithms (MBDCAs), treatment planning systems (TPSs) using a MBDCA require a set of well-defined test case plans characterized by Monte Carlo (MC) methods. This also permits direct dose comparison to TG-43 reference data. Such test case plans should be made available for use in the software commissioning process performed by clinical end users. To this end, a hypothetical, generic high-dose rate (HDR) {sup 192}Ir source and a virtual watermore » phantom were designed, which can be imported into a TPS. Methods: A hypothetical, generic HDR {sup 192}Ir source was designed based on commercially available sources as well as a virtual, cubic water phantom that can be imported into any TPS in DICOM format. The dose distribution of the generic {sup 192}Ir source when placed at the center of the cubic phantom, and away from the center under altered scatter conditions, was evaluated using two commercial MBDCAs [Oncentra{sup ®} Brachy with advanced collapsed-cone engine (ACE) and BrachyVision ACUROS{sup TM}]. Dose comparisons were performed using state-of-the-art MC codes for radiation transport, including ALGEBRA, BrachyDose, GEANT4, MCNP5, MCNP6, and PENELOPE2008. The methodologies adhered to recommendations in the AAPM TG-229 report on high-energy brachytherapy source dosimetry. TG-43 dosimetry parameters, an along-away dose-rate table, and primary and scatter separated (PSS) data were obtained. The virtual water phantom of (201){sup 3} voxels (1 mm sides) was used to evaluate the calculated dose distributions. Two test case plans involving a single position of the generic HDR {sup 192}Ir source in this phantom were prepared: (i) source centered in the phantom and (ii) source displaced 7 cm laterally from the center. Datasets were independently produced by different investigators. MC results were then compared against dose calculated using TG-43 and MBDCA methods. Results: TG-43 and PSS datasets were generated for the generic source, the PSS data for use with the ACE algorithm. The dose-rate constant values obtained from seven MC simulations, performed independently using different codes, were in excellent agreement, yielding an average of 1.1109 ± 0.0004 cGy/(h U) (k = 1, Type A uncertainty). MC calculated dose-rate distributions for the two plans were also found to be in excellent agreement, with differences within type A uncertainties. Differences between commercial MBDCA and MC results were test, position, and calculation parameter dependent. On average, however, these differences were within 1% for ACUROS and 2% for ACE at clinically relevant distances. Conclusions: A hypothetical, generic HDR {sup 192}Ir source was designed and implemented in two commercially available TPSs employing different MBDCAs. Reference dose distributions for this source were benchmarked and used for the evaluation of MBDCA calculations employing a virtual, cubic water phantom in the form of a CT DICOM image series. The implementation of a generic source of identical design in all TPSs using MBDCAs is an important step toward supporting univocal commissioning procedures and direct comparisons between TPSs.« less

Limitations of current dosimetry for intracavitary accelerated partial breast irradiation with high dose rate iridium-192 and electronic brachytherapy sources

NASA Astrophysics Data System (ADS)

Raffi, Julie A.

Intracavitary accelerated partial breast irradiation (APBI) is a method of treating early stage breast cancer using a high dose rate (HDR) brachytherapy source positioned within the lumpectomy cavity. An expandable applicator stretches the surrounding tissue into a roughly spherical or elliptical shape and the dose is prescribed to 1 cm beyond the edge of the cavity. Currently, dosimetry for these treatments is most often performed using the American Association of Physicists in Medicine Task Group No. 43 (TG-43) formalism. The TG-43 dose-rate equation determines the dose delivered to a homogeneous water medium by scaling the measured source strength with standardized parameters that describe the radial and angular features of the dose distribution. Since TG-43 parameters for each source model are measured or calculated in a homogeneous water medium, the dosimetric effects of the patient's dimensions and composition are not accounted for. Therefore, the accuracy of TG-43 calculations for intracavitary APBI is limited by the presence of inhomogeneities in and around the target volume. Specifically, the breast is smaller than the phantoms used to determine TG-43 parameters and is surrounded by air, ribs, and lung tissue. Also, the composition of the breast tissue itself can affect the dose distribution. This dissertation is focused on investigating the limitations of TG-43 dosimetry for intracavitary APBI for two HDR brachytherapy sources: the VariSource TM VS2000 192Ir source and the AxxentRTM miniature x-ray source. The dose for various conditions was determined using thermoluminescent dosimeters (TLDs) and Monte Carlo (MC) calculations. Accurate measurements and calculations were achieved through the implementation of new measurement and simulation techniques and a novel breast phantom was developed to enable anthropomorphic phantom measurements. Measured and calculated doses for phantom and patient geometries were compared with TG-43 calculated doses to illustrate the limitations of TG-43 dosimetry for intracavitary APBI. TG-43 dose calculations overestimate the dose for regions approaching the lung and breast surface and underestimate the dose for regions in and beyond less-attenuating media such as lung tissue, and for lower energies, breast tissue as well.

Revision of the dosimetric parameters of the CSM11 LDR Cs-137 source.

PubMed

Otal, Antonio; Martínez-Fernández, Juan Manuel; Granero, Domingo

2011-03-01

The clinical use of brachytherapy sources requires the existence of dosimetric data with enough of quality for the proper application of treatments in clinical practice. It has been found that the published data for the low dose rate CSM11 Cs-137 source lacks of smoothness in some regions because the data are too noisy. The purpose of this study was to calculate the dosimetric data for this source in order to provide quality dosimetric improvement of the existing dosimetric data of Ballester et al . [1]. In order to obtain the dose rate distributions Monte Carlo simulations were done using the GEANT4 code. A spherical phantom 40 cm in radius with the Cs-137 source located at the centre of the phantom was used. The results from Monte Carlo simulations were applied to derive AAPM Task Group 43 dosimetric parameters: anisotropy function, radial dose function, air kerma strength and dose rate constant. The dose rate constant obtained was 1.094 ± 0.002 cGy h -1 U -1 . The new calculated data agrees within experimental uncertainties with the existing data of Ballester et al . but without the statistical noise of that study. The obtained data presently fulfills all the requirements of the TG-43U1 update and thus it can be used in clinical practice.

SU-E-T-413: Examining Acquisition Rate for Using MatriXX Ion Chamber Array to Measure HDR Brachytherapy Treatments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagar, M; Bhagwat, M; O’Farrell, D

2015-06-15

Purpose: There are unique obstacles to implementing the MatriXX ionchamber array as a QA tool in Brachytherapy given that the device is designed for use in the MV energy range. One of the challenges we investigate is the affect of acquisition rates on dose measurement accuracy for HDR treatment plans. Methods: A treatment plan was optimized in Oncentra Brachy TPS to deliver a planar dose to a 5×5cm region at 10mm depth. The applicator was affixed to the surface of the MatriXX array. The plan was delivered multiple times using a Nucleatron HDR afterloader with a 2.9Ci Ir192 source. Formore » each measurement the sampling rate of the MatriXX movie mode was varied (30ms and 500ms). This experiment was repeated with identical parameters, following a source exchange, with an 11.2Ci Ir192 source. Finally, a single snap measurement was acquired. Analysis was preformed to evaluate the fidelity of the dose delivery for each iteration of the experiment. Evaluation was based on the comparison between the measured and TPS predicted dose. Results: Higher sample rates induce a greater discrepancy between the predicted and measured dose. Delivering the plan using a lower activity source also produced greater discrepancy in the measurement due to the increased delivery time. Analyzing the single snap measurement showed little difference from the 500ms integral dose measurement. Conclusion: The advantage of using movie mode for HDR treatment delivery QA is the ability for real time source tracking in addition to dose measurement. Our analysis indicates that 500ms is an optimal frame rate.« less

Dose rate in brachytherapy using after-loading machine: pulsed or high-dose rate?

PubMed

Hannoun-Lévi, J-M; Peiffert, D

2014-10-01

Since February 2014, it is no longer possible to use low-dose rate 192 iridium wires due to the end of industrial production of IRF1 and IRF2 sources. The Brachytherapy Group of the French society of radiation oncology (GC-SFRO) has recommended switching from iridium wires to after-loading machines. Two types of after-loading machines are currently available, based on the dose rate used: pulsed-dose rate or high-dose rate. In this article, we propose a comparative analysis between pulsed-dose rate and high-dose rate brachytherapy, based on biological, technological, organizational and financial considerations. Copyright © 2014 Société française de radiothérapie oncologique (SFRO). Published by Elsevier SAS. All rights reserved.

SU-G-201-06: Directional Low-Dose Rate Brachytherapy: Determination of the TG-43 Dose-Rate Constant Analog for a New Pd-103 Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aima, M; Culberson, W; Hammer, C

Purpose: The aim of this work is to determine the TG-43 dose-rate constant analog for a new directional low-dose rate brachytherapy source based on experimental methods and comparison to Monte Carlo simulations. The CivaSheet™ is a new commercially available planar source array comprised of a variable number of discrete directional source elements called “CivaDots”. Given the directional nature and non-conventional design of the source, modifications to the AAPM TG-43 protocol for dosimetry are required. As a result, various parameters of the TG-43 dosimetric formalism have to be adapted to accommodate this source. This work focuses on the dose-rate constant analogmore » determination for a CivaDot. Methods: Dose to water measurements of the CivaDot were performed in a polymethyl methacrylate phantom (20×20×12 cm{sup 3}) using thermoluminescent dosimeters (TLDs) and Gafchromic EBT3 film. The source was placed in the center of the phantom, and nine TLD micro-cubes were irradiated along its central axis at a distance of 1 cm. For the film measurements, the TLDs were substituted by a (3×3) cm{sup 2} EBT3 film. Primary air-kerma strength measurements of the source were performed using a variable-aperture free-air chamber. Finally, the source was modeled using the Monte Carlo N-Particle Transport Code 6. Results: Dose-rate constant analog observed for a total of eight CivaDots using TLDs and five CivaDots using EBT3 film was within ±7.0% and ±2.9% of the Monte Carlo predicted value respectively. The average difference observed was −4.8% and −0.1% with a standard deviation of 1.7% and 2.1% for the TLD and the film measurements respectively, which are both within the comparison uncertainty. Conclusion: A preliminary investigation to determine the doserate constant analog for a CivaDot was conducted successfully with good agreement between experimental and Monte Carlo based methods. This work will aid in the eventual realization of a clinically-viable dosimetric framework for the CivaSheet. This work was partially supported by NCI contract (HHSN261201200052C) through CivaTech Oncology Inc.« less

Comparison of the hypothetical 57Co brachytherapy source with the 192Ir source

PubMed Central

Toossi, Mohammad Taghi Bahreyni; Rostami, Atefeh; Khosroabadi, Mohsen; Khademi, Sara; Knaup, Courtney

2016-01-01

Aim of the study The 57Co radioisotope has recently been proposed as a hypothetical brachytherapy source due to its high specific activity, appropriate half-life (272 days) and medium energy photons (114.17 keV on average). In this study, Task Group No. 43 dosimetric parameters were calculated and reported for a hypothetical 57Co source. Material and methods A hypothetical 57Co source was simulated in MCNPX, consisting of an active cylinder with 3.5 mm length and 0.6 mm radius encapsulated in a stainless steel capsule. Three photon energies were utilized (136 keV [10.68%], 122 keV [85.60%], 14 keV [9.16%]) for the 57Co source. Air kerma strength, dose rate constant, radial dose function, anisotropy function, and isodose curves for the source were calculated and compared to the corresponding data for a 192Ir source. Results The results are presented as tables and figures. Air kerma strength per 1 mCi activity for the 57Co source was 0.46 cGyh–1 cm 2 mCi–1. The dose rate constant for the 57Co source was determined to be 1.215 cGyh–1U–1. The radial dose function for the 57Co source has an increasing trend due to multiple scattering of low energy photons. The anisotropy function for the 57Co source at various distances from the source is more isotropic than the 192Ir source. Conclusions The 57Co source has advantages over 192Ir due to its lower energy photons, longer half-life, higher dose rate constant and more isotropic anisotropic function. However, the 192Ir source has a higher initial air kerma strength and more uniform radial dose function. These properties make 57Co a suitable source for use in brachytherapy applications. PMID:27688731

Recommended de minimis radiation dose rates for Canada. Report No. INFO-0355

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1990-01-01

A de minimis dose or dose rate as used in this report represents a level of risk which is generally accepted as being of no significance to an individual, or in the case of a population, of no significance to society. The report describes the risk of biological effects from radiation; radiation from natural and man-made sources; normal incidences of cancer and genetic defects; initiatives by other agencies in the U.S., the U.K. and internationally; the importance of collective dose and dose rate; assigning values to the de minimis dose rates; and application of the de minimis dose rates.

Source position verification and dosimetry in HDR brachytherapy using an EPID.

PubMed

Smith, R L; Taylor, M L; McDermott, L N; Haworth, A; Millar, J L; Franich, R D

2013-11-01

Accurate treatment delivery in high dose rate (HDR) brachytherapy requires correct source dwell positions and dwell times to be administered relative to each other and to the surrounding anatomy. Treatment delivery inaccuracies predominantly occur for two reasons: (i) anatomical movement or (ii) as a result of human errors that are usually related to incorrect implementation of the planned treatment. Electronic portal imaging devices (EPIDs) were originally developed for patient position verification in external beam radiotherapy and their application has been extended to provide dosimetric information. The authors have characterized the response of an EPID for use with an (192)Ir brachytherapy source to demonstrate its use as a verification device, providing both source position and dosimetric information. Characterization of the EPID response using an (192)Ir brachytherapy source included investigations of reproducibility, linearity with dose rate, photon energy dependence, and charge build-up effects associated with exposure time and image acquisition time. Source position resolution in three dimensions was determined. To illustrate treatment verification, a simple treatment plan was delivered to a phantom and the measured EPID dose distribution compared with the planned dose. The mean absolute source position error in the plane parallel to the EPID, for dwells measured at 50, 100, and 150 mm source to detector distances (SDD), was determined to be 0.26 mm. The resolution of the z coordinate (perpendicular distance from detector plane) is SDD dependent with 95% confidence intervals of ± 0.1, ± 0.5, and ± 2.0 mm at SDDs of 50, 100, and 150 mm, respectively. The response of the EPID is highly linear to dose rate. The EPID exhibits an over-response to low energy incident photons and this nonlinearity is incorporated into the dose calibration procedure. A distance (spectral) dependent dose rate calibration procedure has been developed. The difference between measured and planned dose is less than 2% for 98.0% of pixels in a two-dimensional plane at an SDD of 100 mm. Our application of EPID dosimetry to HDR brachytherapy provides a quality assurance measure of the geometrical distribution of the delivered dose as well as the source positions, which is not possible with any current HDR brachytherapy verification system.

SU-F-19A-05: Experimental and Monte Carlo Characterization of the 1 Cm CivaString 103Pd Brachytherapy Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reed, J; Micka, J; Culberson, W

Purpose: To determine the in-air azimuthal anisotropy and in-water dose distribution for the 1 cm length of the CivaString {sup 103}Pd brachytherapy source through measurements and Monte Carlo (MC) simulations. American Association of Physicists in Medicine Task Group No. 43 (TG-43) dosimetry parameters were also determined for this source. Methods: The in-air azimuthal anisotropy of the source was measured with a NaI scintillation detector and simulated with the MCNP5 radiation transport code. Measured and simulated results were normalized to their respective mean values and compared. The TG-43 dose-rate constant, line-source radial dose function, and 2D anisotropy function for this sourcemore » were determined from LiF:Mg,Ti thermoluminescent dosimeter (TLD) measurements and MC simulations. The impact of {sup 103}Pd well-loading variability on the in-water dose distribution was investigated using MC simulations by comparing the dose distribution for a source model with four wells of equal strength to that for a source model with strengths increased by 1% for two of the four wells. Results: NaI scintillation detector measurements and MC simulations of the in-air azimuthal anisotropy showed that ≥95% of the normalized data were within 1.2% of the mean value. TLD measurements and MC simulations of the TG-43 dose-rate constant, line-source radial dose function, and 2D anisotropy function agreed to within the experimental TLD uncertainties (k=2). MC simulations showed that a 1% variability in {sup 103}Pd well-loading resulted in changes of <0.1%, <0.1%, and <0.3% in the TG-43 dose-rate constant, radial dose distribution, and polar dose distribution, respectively. Conclusion: The CivaString source has a high degree of azimuthal symmetry as indicated by the NaI scintillation detector measurements and MC simulations of the in-air azimuthal anisotropy. TG-43 dosimetry parameters for this source were determined from TLD measurements and MC simulations. {sup 103}Pd well-loading variability results in minimal variations in the in-water dose distribution according to MC simulations. This work was partially supported by CivaTech Oncology, Inc. through an educational grant for Joshua Reed, John Micka, Wesley Culberson, and Larry DeWerd and through research support for Mark Rivard.« less

Development of a high sensitivity pinhole type gamma camera using semiconductors for low dose rate fields

NASA Astrophysics Data System (ADS)

Ueno, Yuichiro; Takahashi, Isao; Ishitsu, Takafumi; Tadokoro, Takahiro; Okada, Koichi; Nagumo, Yasushi; Fujishima, Yasutake; Yoshida, Akira; Umegaki, Kikuo

2018-06-01

We developed a pinhole type gamma camera, using a compact detector module of a pixelated CdTe semiconductor, which has suitable sensitivity and quantitative accuracy for low dose rate fields. In order to improve the sensitivity of the pinhole type semiconductor gamma camera, we adopted three methods: a signal processing method to set the discriminating level lower, a high sensitivity pinhole collimator and a smoothing image filter that improves the efficiency of the source identification. We tested basic performances of the developed gamma camera and carefully examined effects of the three methods. From the sensitivity test, we found that the effective sensitivity was about 21 times higher than that of the gamma camera for high dose rate fields which we had previously developed. We confirmed that the gamma camera had sufficient sensitivity and high quantitative accuracy; for example, a weak hot spot (0.9 μSv/h) around a tree root could be detected within 45 min in a low dose rate field test, and errors of measured dose rates with point sources were less than 7% in a dose rate accuracy test.

Effects of breast-air and breast-lung interfaces on the dose rate at the planning target volume of a MammoSite catheter for Yb-169 and Ir-192 HDR sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cazeca, Mario J.; Medich, David C.; Munro, John J. III

2010-08-15

Purpose: To study the effects of the breast-air and breast-lung interfaces on the absorbed dose within the planning target volume (PTV) of a MammoSite balloon dose delivery system as well as the effect of contrast material on the dose rate in the PTV. Methods: The Monte Carlo MCNP5 code was used to simulate dose rate in the PTV of a 2 cm radius MammoSite balloon dose delivery system. The simulations were carried out using an average female chest phantom (AFCP) and a semi-infinite water phantom for both Yb-169 and Ir-192 high dose rate sources for brachytherapy application. Gastrografin was introducedmore » at varying concentrations to study the effect of contrast material on the dose rate in the PTV. Results: The effect of the density of the materials surrounding the MammoSite balloon containing 0% contrast material on the calculated dose rate at different radial distances in the PTV was demonstrated. Within the PTV, the ratio of the calculated dose rate for the AFCP and the semi-infinite water phantom for the point closest to the breast-air interface (90 deg.) is less than that for the point closest to the breast-lung interface (270 deg.) by 11.4% and 4% for the HDR sources of Yb-169 and Ir-192, respectively. When contrast material was introduced into the 2 cm radius MammoSite balloon at varying concentrations, (5%, 10%, 15%, and 20%), the dose rate in the AFCP at 3.0 cm radial distance at 90 deg. was decreased by as much as 14.8% and 6.2% for Yb-169 and Ir-192, respectively, when compared to that of the semi-infinite water phantom with contrast concentrations of 5%, 10%, 15%, and 20%, respectively. Conclusions: Commercially available software used to calculate dose rate in the PTV of a MammoSite balloon needs to account for patient anatomy and density of surrounding materials in the dosimetry analyses in order to avoid patient underdose.« less

Using RADFET for the real-time measurement of gamma radiation dose rate

NASA Astrophysics Data System (ADS)

Andjelković, Marko S.; Ristić, Goran S.; Jakšić, Aleksandar B.

2015-02-01

RADFETs (RADiation sensitive Field Effect Transistors) are integrating ionizing radiation dosimeters operating on the principle of conversion of radiation-induced threshold voltage shift into absorbed dose. However, one of the major drawbacks of RADFETs is the inability to provide the information on the dose rate in real-time using the conventional absorbed dose measurement technique. The real-time monitoring of dose rate and absorbed dose can be achieved with the current mode dosimeters such as PN and PIN diodes/photodiodes, but these dosimeters have some limitations as absorbed dose meters and hence they are often not a suitable replacement for RADFETs. In that sense, this paper investigates the possibility of using the RADFET as a real-time dose rate meter so that it could be applied for simultaneous online measurement of the dose rate and absorbed dose. A RADFET sample, manufactured by Tyndall National Institute, Cork, Ireland, was tested as a dose rate meter under gamma irradiation from a Co-60 source. The RADFET was configured as a PN junction, such that the drain, gate and source terminals were grounded, while the radiation-induced current was measured at the bulk terminal, whereby the bulk was successively biased with 0 , 10 , 20  and 30 V. In zero-bias mode the radiation-induced current was unstable, but in the biased mode the current response was stable for the investigated dose rates from 0.65  to 32.1 Gy h-1 and up to the total absorbed dose of 25 Gy. The current increased with the dose rate in accordance with the power law, whereas the sensitivity of the current read-out was linear with respect to the applied bias voltage. Comparison with previously analyzed PIN photodiodes has shown that the investigated RADFET is competitive with PIN photodiodes as a gamma radiation dose rate meter and therefore has the potential to be employed for the real-time monitoring of the dose rate and absorbed dose.

Improved neutron activation prediction code system development

NASA Technical Reports Server (NTRS)

Saqui, R. M.

1971-01-01

Two integrated neutron activation prediction code systems have been developed by modifying and integrating existing computer programs to perform the necessary computations to determine neutron induced activation gamma ray doses and dose rates in complex geometries. Each of the two systems is comprised of three computational modules. The first program module computes the spatial and energy distribution of the neutron flux from an input source and prepares input data for the second program which performs the reaction rate, decay chain and activation gamma source calculations. A third module then accepts input prepared by the second program to compute the cumulative gamma doses and/or dose rates at specified detector locations in complex, three-dimensional geometries.

Assessment of neutron dosemeters around standard sources and nuclear fissile objects.

PubMed

Raimondi, N; Tournier, B; Groetz, J E; Piot, J; Riebler, E; Crovisier, P; Chambaudet, A; Cabanné, N

2002-01-01

In order to evaluate the neutron doses around nuclear fissile objects, a comparative study has been made on several neutron dosemeters: bubble dosemeters, etched-track detectors (CR-39) and 3He-filled proportional counters used as dose-rate meters. The measurements were made on the ambient and the personal dose equivalents H*(10) and Hp(10). Results showed that several bubble dosemeters should have been used due to a low reproducibility in the measurements. A strong correlation with the neutron energy was also found, with about a 30% underestimation of Hp(10) for neutrons from the PuBe source, and about a 9% overestimation for neutrons from the 252Cf source. Measurements of the nuclear fissile objects were made using the CR-39 and the dose-rate meters. The CR-39 led to an underestimation of 30% with respect to the neutron dose-rate meter measurements. In addition, the MCNP calculation code was used in the different configurations.

Directional interstitial brachytherapy from simulation to application

NASA Astrophysics Data System (ADS)

Lin, Liyong

Organs at risk (OAR) are sometimes adjacent to or embedded in or overlap with the clinical target volume (CTV) to be treated. The purpose of this PhD study is to develop directionally low energy gamma-emitting interstitial brachytherapy sources. These sources can be applied between OAR to selectively reduce hot spots in the OARs and normal tissues. The reduction of dose over undesired regions can expand patient eligibility or reduce toxicities for the treatment by conventional interstitial brachytherapy. This study covers the development of a directional source from design optimization to construction of the first prototype source. The Monte Carlo code MCNP was used to simulate the radiation transport for the designs of directional sources. We have made a special construction kit to assemble radioactive and gold-shield components precisely into D-shaped titanium containers of the first directional source. Directional sources have a similar dose distribution as conventional sources on the treated side but greatly reduced dose on the shielded side, with a sharp dose gradient between them. A three-dimensional dose deposition kernel for the 125I directional source has been calculated. Treatment plans can use both directional and conventional 125I sources at the same source strength for low-dose-rate (LDR) implants to optimize the dose distributions. For prostate tumors, directional 125I LDR brachytherapy can potentially reduce genitourinary and gastrointestinal toxicities and improve potency preservation for low risk patients. The combination of better dose distribution of directional implants and better therapeutic ratio between tumor response and late reactions enables a novel temporary LDR treatment, as opposed to permanent or high-dose-rate (HDR) brachytherapy for the intermediate risk T2b and high risk T2c tumors. Supplemental external-beam treatments can be shortened with a better brachytherapy boost for T3 tumors. In conclusion, we have successfully finished the design optimization and construction of the first prototype directional source. Potential clinical applications and potential benefits of directional sources have been shown for prostate and breast tumors.

Determination of the gamma-ray skyshine dose contribution in a Loss Of Shielding accident

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dennis, M.L.; Weiner, R.F.; Osborn, D.M.

2007-07-01

The goal of this research is to determine the gamma-ray dose contribution from skyshine. In a transportation accident involving the loss of lead gamma shielding, first responders to the accident will be exposed to both direct gamma radiation streaming from the exposed spent nuclear fuel and atmospherically reflected gamma radiation. The reflected radiation is referred to as skyshine and should contribute minimally to the overall dose; however, when there is minimal shielding above the exposed source, skyshine at large distances from the source must be considered. The program SKYDOSE developed by Shultis and Faw evaluates the gamma-ray skyshine dose frommore » a point, isotropic, polyenergetic, gamma-photon source. Assuming an infinite black wall shielding all direct radiation, the model assumes a first responder is located at varying distances from the wall. Skyshine doses are calculated both through SKYDOSE's integral line-beam method and an approximate approach prescribed by the National Council of Radiation Protection and Measurements. Initial results from SKYDOSE indicate nearly equivalent dose rates from either direct or skyshine radiation at nine meters from the wall, which seemed unusual and not readily explained. NCRP methodology, however, yields skyshine dose rates which are drastically smaller than direct dose rates at the same distance. Further investigation using the program MicroSkyshine{sup R}, which allows a variety of source configurations, suggests skyshine contributes minimally to dose in a loss-of-shielding accident. (authors)« less

Comparison of monoenergetic photon organ dose rate coefficients for stylized and voxel phantoms submerged in air

DOE PAGES

Bellamy, Michael B.; Hiller, Mauritius M.; Dewji, Shaheen A.; ...

2016-02-01

As part of a broader effort to calculate effective dose rate coefficients for external exposure to photons and electrons emitted by radionuclides distributed in air, soil or water, age-specific stylized phantoms have been employed to determine dose coefficients relating dose rate to organs and tissues in the body. In this article, dose rate coefficients computed using the International Commission on Radiological Protection reference adult male voxel phantom are compared with values computed using the Oak Ridge National Laboratory adult male stylized phantom in an air submersion exposure geometry. Monte Carlo calculations for both phantoms were performed for monoenergetic source photonsmore » in the range of 30 keV to 5 MeV. Furthermore, these calculations largely result in differences under 10 % for photon energies above 50 keV, and it can be expected that both models show comparable results for the environmental sources of radionuclides.« less

Comparison of monoenergetic photon organ dose rate coefficients for stylized and voxel phantoms submerged in air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bellamy, Michael B.; Hiller, Mauritius M.; Dewji, Shaheen A.

As part of a broader effort to calculate effective dose rate coefficients for external exposure to photons and electrons emitted by radionuclides distributed in air, soil or water, age-specific stylized phantoms have been employed to determine dose coefficients relating dose rate to organs and tissues in the body. In this article, dose rate coefficients computed using the International Commission on Radiological Protection reference adult male voxel phantom are compared with values computed using the Oak Ridge National Laboratory adult male stylized phantom in an air submersion exposure geometry. Monte Carlo calculations for both phantoms were performed for monoenergetic source photonsmore » in the range of 30 keV to 5 MeV. Furthermore, these calculations largely result in differences under 10 % for photon energies above 50 keV, and it can be expected that both models show comparable results for the environmental sources of radionuclides.« less

Application of a color scanner for 60Co high dose rate brachytherapy dosimetry with EBT radiochromic film

PubMed Central

Ghorbani, Mahdi; Toossi, Mohammad Taghi Bahreyni; Mowlavi, Ali Asghar; Roodi, Shahram Bayani; Meigooni, Ali Soleimani

2012-01-01

Background. The aim of this study is to evaluate the performance of a color scanner as a radiochromic film reader in two dimensional dosimetry around a high dose rate brachytherapy source. Materials and methods A Microtek ScanMaker 1000XL film scanner was utilized for the measurement of dose distribution around a high dose rate GZP6 60Co brachytherapy source with GafChromic® EBT radiochromic films. In these investigations, the non-uniformity of the film and scanner response, combined, as well as the films sensitivity to scanner’s light source was evaluated using multiple samples of films, prior to the source dosimetry. The results of these measurements were compared with the Monte Carlo simulated data using MCNPX code. In addition, isodose curves acquired by radiochromic films and Monte Carlo simulation were compared with those provided by the GZP6 treatment planning system. Results Scanning of samples of uniformly irradiated films demonstrated approximately 2.85% and 4.97% nonuniformity of the response, respectively in the longitudinal and transverse directions of the film. Our findings have also indicated that the film response is not affected by the exposure to the scanner’s light source, particularly in multiple scanning of film. The results of radiochromic film measurements are in good agreement with the Monte Carlo calculations (4%) and the corresponding dose values presented by the GZP6 treatment planning system (5%). Conclusions The results of these investigations indicate that the Microtek ScanMaker 1000XL color scanner in conjunction with GafChromic EBT film is a reliable system for dosimetric evaluation of a high dose rate brachytherapy source. PMID:23411947

AN ESTIMATION OF THE EXPOSURE OF THE POPULATION OF ISRAEL TO NATURAL SOURCES OF IONIZING RADIATION.

PubMed

Epstein, L; Koch, J; Riemer, T; Haquin, G; Orion, I

2017-11-01

The radiation dose to the population of Israel due to exposure to natural sources of ionizing radiation was assessed. The main contributor to the dose is radon that accounts for 60% of the exposure to natural sources. The dose due to radon inhalation was assessed by combining the results of a radon survey in single-family houses with the results of a survey in apartments in multi-storey buildings. The average annual dose due to radon inhalation was found to be 1.2 mSv. The dose rate due to exposure to cosmic radiation was assessed using a code that calculates the dose rate at different heights above sea level, taking into account the solar cycle. The annual dose was calculated based on the fraction of time spent indoors and the attenuation provided by buildings and was found to be 0.2 mSv. The annual dose due to external exposure to the terrestrial radionuclides was similarly assessed. The indoor dose rate was calculated using a model that takes into account the concentrations of the natural radionuclides in building materials, the density and the thickness of the walls. The dose rate outdoors was calculated based on the concentrations of the natural radionuclides in different geological units in Israel as measured in an aerial survey and measurements above ground. The annual dose was found to be 0.2 mSv. Doses due to internal exposure other than exposure to radon were also calculated and were found to be 0.4 mSv. The overall annual exposure of the population of Israel to natural sources of ionizing radiation is therefore 2 mSv and ranges between 1.7 and 2.7 mSv. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Physics-aspects of dose accuracy in high dose rate (HDR) brachytherapy: source dosimetry, treatment planning, equipment performance and in vivo verification techniques

PubMed Central

Bradley, David; Nisbet, Andrew

2012-01-01

This study provides a review of recent publications on the physics-aspects of dosimetric accuracy in high dose rate (HDR) brachytherapy. The discussion of accuracy is primarily concerned with uncertainties, but methods to improve dose conformation to the prescribed intended dose distribution are also noted. The main aim of the paper is to review current practical techniques and methods employed for HDR brachytherapy dosimetry. This includes work on the determination of dose rate fields around brachytherapy sources, the capability of treatment planning systems, the performance of treatment units and methods to verify dose delivery. This work highlights the determinants of accuracy in HDR dosimetry and treatment delivery and presents a selection of papers, focusing on articles from the last five years, to reflect active areas of research and development. Apart from Monte Carlo modelling of source dosimetry, there is no clear consensus on the optimum techniques to be used to assure dosimetric accuracy through all the processes involved in HDR brachytherapy treatment. With the exception of the ESTRO mailed dosimetry service, there is little dosimetric audit activity reported in the literature, when compared with external beam radiotherapy verification. PMID:23349649

Physics-aspects of dose accuracy in high dose rate (HDR) brachytherapy: source dosimetry, treatment planning, equipment performance and in vivo verification techniques.

PubMed

Palmer, Antony; Bradley, David; Nisbet, Andrew

2012-06-01

This study provides a review of recent publications on the physics-aspects of dosimetric accuracy in high dose rate (HDR) brachytherapy. The discussion of accuracy is primarily concerned with uncertainties, but methods to improve dose conformation to the prescribed intended dose distribution are also noted. The main aim of the paper is to review current practical techniques and methods employed for HDR brachytherapy dosimetry. This includes work on the determination of dose rate fields around brachytherapy sources, the capability of treatment planning systems, the performance of treatment units and methods to verify dose delivery. This work highlights the determinants of accuracy in HDR dosimetry and treatment delivery and presents a selection of papers, focusing on articles from the last five years, to reflect active areas of research and development. Apart from Monte Carlo modelling of source dosimetry, there is no clear consensus on the optimum techniques to be used to assure dosimetric accuracy through all the processes involved in HDR brachytherapy treatment. With the exception of the ESTRO mailed dosimetry service, there is little dosimetric audit activity reported in the literature, when compared with external beam radiotherapy verification.

Dose-rate effects on the radiation-induced oxidation of electric cable used in nuclear power plants

NASA Astrophysics Data System (ADS)

Reynolds, A. B.; Bell, R. M.; Bryson, N. M. N.; Doyle, T. E.; Hall, M. B.; Mason, L. R.; Quintric, L.; Terwilliger, P. L.

1995-01-01

Dose-rate effects were measured for typical ethylene propylene rubber (EPR) and crosslinked polyethylene (XLPE) electric cable used in nuclear power plants. The radiation source was the 60Co Irradiation Facility at the University of Virginia. Dose rates were varied from 5 Gy/h to 2500 Gy/h. It was found that there is little or no dose-rate effect at low doses for four of the five EPR cable products tested from 2500 Gy/h down to dose rates of 5 Gy/h but perhaps a small dose-rate effect at high doses for dose rates above 340 Gy/h. A small dose-rate exists for the fifth EPR above 340 Gy/h at all doses. A dose-rate effect exists above 40 Gy/h for two of the three XLPE cable products tested, but there is no dose-rate for these XLPE's between 40 Gy/h and 5 Gy/h. These results indicate that the dose-rate effects observed are due to oxygen diffusion effects during heterogeneous aging and suggest that there is no dose-rate effect for either EPR or XLPE during homogeneous aging.

On determining dose rate constants spectroscopically.

PubMed

Rodriguez, M; Rogers, D W O

2013-01-01

To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of (125)I and (103)Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089-6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated (125)I and (103)Pd sources. Spectra generated by 14 (125)I and 6 (103)Pd seeds were calculated in vacuo at 10 cm from the source in a 2.7 × 2.7 × 0.05 cm(3) voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the (125)I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for (103)Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were ≤0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. The ratio of the intensity of the 31 keV line relative to that of the main peak in (125)I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The (103)Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when calculated with the TG-43U1 rather than the NNDC(2000) initial spectrum. The measured values from three different investigations are in much better agreement with the calculations using the NCRP Report 58 and NNDC(2000) initial spectra with average discrepancies of 0.9% and 1.7% for the (125)I and (103)Pd seeds, respectively. However, there are no differences in the calculated TG-43U1 brachytherapy parameters using either initial spectrum in both cases. Similarly, there were no differences outside the statistical uncertainties of 0.1% or 0.2%, in the average energy, air kerma/history, dose rate/history, and dose rate constant when calculated using either the full photon spectrum or the main-peaks-only spectrum. Our calculated dose rate constants based on using the calculated on-axis spectrum and a line or dual-point source model are in excellent agreement (0.5% on average) with the values of Chen and Nath, verifying the accuracy of their more approximate method of going from the spectrum to the dose rate constant. However, the dose rate constants based on full seed models differ by between +4.6% and -1.5% from those based on the line or dual-point source approximations. These results suggest that the main value of spectroscopic measurements is to verify full Monte Carlo models of the seeds by comparison to the calculated spectra.

Dosimetric investigation of LDR brachytherapy ¹⁹²Ir wires by Monte Carlo and TPS calculations.

PubMed

Bozkurt, Ahmet; Acun, Hediye; Kemikler, Gonul

2013-01-01

The aim of this study was to investigate the dose rate distribution around (192)Ir wires used as radioactive sources in low-dose-rate brachytherapy applications. Monte Carlo modeling of a 0.3-mm diameter source and its surrounding water medium was performed for five different wire lengths (1-5 cm) using the MCNP software package. The computed dose rates per unit of air kerma at distances from 0.1 up to 10 cm away from the source were first verified with literature data sets. Then, the simulation results were compared with the calculations from the XiO CMS commercial treatment planning system. The study results were found to be in concordance with the treatment planning system calculations except for the shorter wires at close distances.

Dosimetric study of GZP6 60 Co high dose rate brachytherapy source.

PubMed

Lei, Qin; Xu, Anjian; Gou, Chengjun; Wen, Yumei; He, Donglin; Wu, Junxiang; Hou, Qing; Wu, Zhangwen

2018-05-28

The purpose of this study was to obtain dosimetric parameters of GZP6 60 Co brachytherapy source number 3. The Geant4 MC code has been used to obtain the dose rate distribution following the American Association of Physicists in Medicine (AAPM) TG-43U1 dosimetric formalism. In the simulation, the source was centered in a 50 cm radius water phantom. The cylindrical ring voxels were 0.1 mm thick for r ≤ 1 cm, 0.5 mm for 1 cm < r ≤ 5 cm, and 1 mm for r > 5 cm. The kerma-dose approximation was performed for r > 0.75 cm to increase the simulation efficiency. Based on the numerical results, the dosimetric datasets were obtained. These results were compared with the available data of the similar 60 Co high dose rate sources and the detailed dosimetric characterization was discussed. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

Reference air kerma rate calibration system for high dose rate Ir-192 brachytherapy sources in Taiwan

NASA Astrophysics Data System (ADS)

Chu, Wei-Han; Yuan, Ming-Chen; Lee, Jeng-Hung; Lin, Yi-Chun

2017-11-01

Ir-192 sources are widely used in brachytherapy and the number of treatments is around seven thousand for the use of the high dose rate (HDR) Ir-192 brachytherapy source per year in Taiwan. Due to its physical half-life of 73.8 days, the source should be replaced four times per year to maintain the HDR treatment mode (DDEP, 2005; Coursey et al., 1992). When doing this work, it must perform the source dose trace to assure the dose accuracy. To establish the primary measurement standard of reference air kerma rate(RAKR) for the HDR Ir-192 brachytherapy sources in Taiwan, the Institute of Nuclear Energy Research (INER) fabricated a dual spherical graphite-walled cavity ionization chambers system to directly measure the RAKR of the Ir-192 brachytherapy source. In this system, the ion-charge was accumulated by the two ionization chambers and after correction for the ion recombination, temperature, atmosphere pressure, room scattering, graphite-wall attenuation, air attenuation, source decay, stem effect, and so on. The RAKR of the Ir-192 source was obtained in the ambient conditions of 22 °C and one atmosphere. The measurement uncertainty of the system was around 0.92% in 96% confidence level (k=2.0). To verify the accuracy of the result, the source calibration comparison has been made at the National Radiation Standard Laboratory (NRSL) of INER and Physikalisch-Technische Bundesanstalt (PTB, Germany) in 2015. The ratio of the measurement results between INER and PTB, INER/PTB, was 0.998±0.027 (k=2) which showed good consistency and the performance of the system was verified.

A quality assurance device for measuring afterloader performance and transit dose for nasobiliary high-dose-rate brachytherapy.

PubMed

Deufel, Christopher L; Mullins, John P; Zakhary, Mark J

2018-05-17

Nasobiliary high-dose-rate (HDR) brachytherapy has emerged as an effective tool to boost the radiation dose for patients with unresectable perihilar cholangiocarcinoma. This work describes a quality assurance (QA) tool for measuring the HDR afterloader's performance, including the transit dose, when the source wire travels through a tortuous nasobiliary catheter path. The nasobiliary QA device was designed to mimic the anatomical path of a nasobiliary catheter, including the nasal, stomach, duodenum, and bile duct loops. Two of these loops, the duodenum and bile duct loops, have adjustable radii of curvature, resulting in the ability to maximize stress on the source wire in transit. The device was used to measure the performance over time for the HDR afterloader and the differences between intraluminal catheter lots. An upper limit on the transit dose was also measured using radiochromic film and compared with a simple theoretical model. The QA device was capable of detecting performance variations among nasobiliary catheter lots and following radioactive source replacement. The transit dose from a nasobiliary treatment increased by up to one order of magnitude when the source wire encountered higher than normal friction. Three distinct travel speeds of the source wire were observed: 5.2, 17.4, and 54.7 cm/s. The maximum transit dose was 0.3 Gy at a radial distance of 5 mm from a 40.3 kU 192 Ir source. The source wire encounters substantially greater friction when it navigates through the nasobiliary brachytherapy catheter. A QA tool that mimics the nasal, stomach, duodenum, and bile duct loops may be used to evaluate transit dose and the afterloader's performance over time. Copyright © 2018 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Rectal Dose and Source Strength of the High-Dose-Rate Iridium-192 Both Affect Late Rectal Bleeding After Intracavitary Radiation Therapy for Uterine Cervical Carcinoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Isohashi, Fumiaki, E-mail: isohashi@radonc.med.osaka-u.ac.j; Yoshioka, Yasuo; Koizumi, Masahiko

2010-07-01

Purpose: The purpose of this study was to reconfirm our previous findings that the rectal dose and source strength both affect late rectal bleeding after high-dose-rate intracavitary brachytherapy (HDR-ICBT), by using a rectal dose calculated in accordance with the definitions of the International Commission on Radiation Units and Measurements Report 38 (ICRU{sub RP}) or of dose-volume histogram (DVH) parameters by the Groupe Europeen de Curietherapie of the European Society for Therapeutic Radiology and Oncology. Methods and Materials: Sixty-two patients who underwent HDR-ICBT and were followed up for 1 year or more were studied. The rectal dose for ICBT was calculatedmore » by using the ICRP{sub RP} based on orthogonal radiographs or the DVH parameters based on computed tomography (CT). The total dose was calculated as the biologically equivalent dose expressed in 2-Gy fractions (EQD{sub 2}). The relationship between averaged source strength or the EQD{sub 2} and late rectal bleeding was then analyzed. Results: When patients were divided into four groups according to rectal EQD{sub 2} ({>=} or =} or <2.4 cGy.m{sup 2}.h{sup -1}), the group with both a high EQD{sub 2} and a high source strength showed a significantly greater probability of rectal bleeding for ICRU{sub RP}, D{sub 2cc}, and D{sub 1cc}. The patients with a median rectal dose above the threshold level did not show a greater frequency of rectal bleeding unless the source strength exceeded 2.4 cGy.m{sup 2}.h{sup -1}. Conclusions: Our results obtained with data based on ICRU{sub RP} and CT-based DVH parameters indicate that rectal dose and source strength both affect rectal bleeding after HDR-ICBT.« less

Organ Dose-Rate Calculations for Small Mammals at Maralinga, the Nevada Test Site, Hanford and Fukushima: A Comparison of Ellipsoidal and Voxelized Dosimetric Methodologies.

PubMed

Caffrey, Emily A; Johansen, Mathew P; Higley, Kathryn A

2015-10-01

Radiological dosimetry for nonhuman biota typically relies on calculations that utilize the Monte Carlo simulations of simple, ellipsoidal geometries with internal radioactivity distributed homogeneously throughout. In this manner it is quick and easy to estimate whole-body dose rates to biota. Voxel models are detailed anatomical phantoms that were first used for calculating radiation dose to humans, which are now being extended to nonhuman biota dose calculations. However, if simple ellipsoidal models provide conservative dose-rate estimates, then the additional labor involved in creating voxel models may be unnecessary for most scenarios. Here we show that the ellipsoidal method provides conservative estimates of organ dose rates to small mammals. Organ dose rates were calculated for environmental source terms from Maralinga, the Nevada Test Site, Hanford and Fukushima using both the ellipsoidal and voxel techniques, and in all cases the ellipsoidal method yielded more conservative dose rates by factors of 1.2-1.4 for photons and 5.3 for beta particles. Dose rates for alpha-emitting radionuclides are identical for each method as full energy absorption in source tissue is assumed. The voxel procedure includes contributions to dose from organ-to-organ irradiation (shown here to comprise 2-50% of total dose from photons and 0-93% of total dose from beta particles) that is not specifically quantified in the ellipsoidal approach. Overall, the voxel models provide robust dosimetry for the nonhuman mammals considered in this study, and though the level of detail is likely extraneous to demonstrating regulatory compliance today, voxel models may nevertheless be advantageous in resolving ongoing questions regarding the effects of ionizing radiation on wildlife.

Digital holographic interferometry: a novel optical calorimetry technique for radiation dosimetry.

PubMed

Cavan, Alicia; Meyer, Juergen

2014-02-01

To develop and demonstrate the proof-of-principle of a novel optical calorimetry method to determine radiation absorbed dose in a transparent medium. The calorimetric property of water is measured during irradiation by means of an interferometer, which detects temperature-induced changes in the refractive index that can be mathematically related to absorbed dose. The proposed method uses a technique called digital holographic interferometry (DHI), which comprises an optical laser interferometer setup and consecutive physical reconstruction of the recorded wave fronts by means of the Fresnel transform. This paper describes the conceptual framework and provides the mathematical basis for DHI dosimetry. Dose distributions from a high dose rate Brachytherapy source were measured by a prototype optical setup to demonstrate the feasibility of the approach. The developed DHI dosimeter successfully determined absorbed dose distributions in water in the region adjacent to a high dose rate Brachytherapy source. A temperature change of 0.0381 K across a distance of 6.8 mm near the source was measured, corresponding to a dose of 159.3 Gy. The standard deviation in a typical measurement set was ± 3.45 Gy (corresponding to an uncertainty in the temperature value of ± 8.3 × 10(-4) K). The relative dose fall off was in agreement with treatment planning system modeled data. First results with a prototype optical setup and a Brachytherapy source demonstrate the proof-of-principle of the approach. The prototype achieves high spatial resolution of approximately 3 × 10(-4) m. The general approach is fundamentally independent of the radiation type and energy. The sensitivity range determined indicates that the method is predominantly suitable for high dose rate applications. Further work is required to determine absolute dose in all three dimensions.

PWR Facility Dose Modeling Using MCNP5 and the CADIS/ADVANTG Variance-Reduction Methodology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blakeman, Edward D; Peplow, Douglas E.; Wagner, John C

2007-09-01

The feasibility of modeling a pressurized-water-reactor (PWR) facility and calculating dose rates at all locations within the containment and adjoining structures using MCNP5 with mesh tallies is presented. Calculations of dose rates resulting from neutron and photon sources from the reactor (operating and shut down for various periods) and the spent fuel pool, as well as for the photon source from the primary coolant loop, were all of interest. Identification of the PWR facility, development of the MCNP-based model and automation of the run process, calculation of the various sources, and development of methods for visually examining mesh tally filesmore » and extracting dose rates were all a significant part of the project. Advanced variance reduction, which was required because of the size of the model and the large amount of shielding, was performed via the CADIS/ADVANTG approach. This methodology uses an automatically generated three-dimensional discrete ordinates model to calculate adjoint fluxes from which MCNP weight windows and source bias parameters are generated. Investigative calculations were performed using a simple block model and a simplified full-scale model of the PWR containment, in which the adjoint source was placed in various regions. In general, it was shown that placement of the adjoint source on the periphery of the model provided adequate results for regions reasonably close to the source (e.g., within the containment structure for the reactor source). A modification to the CADIS/ADVANTG methodology was also studied in which a global adjoint source is weighted by the reciprocal of the dose response calculated by an earlier forward discrete ordinates calculation. This method showed improved results over those using the standard CADIS/ADVANTG approach, and its further investigation is recommended for future efforts.« less

New (125)I brachytherapy source IsoSeed I25.S17plus: Monte Carlo dosimetry simulation and comparison to sources of similar design.

PubMed

Pantelis, Evaggelos; Papagiannis, Panagiotis; Anagnostopoulos, Giorgos; Baltas, Dimos

2013-12-01

To determine the relative dose rate distribution around the new (125)I brachytherapy source IsoSeed I25.S17plus and report results in a form suitable for clinical use. Results for the new source are also compared to corresponding results for other commercially available (125)I sources of similar design. Monte Carlo simulations were performed using the MCNP5 v.1.6 general purpose code. The model of the new source was prepared from information provided by the manufacturer and verified by imaging a sample of ten non-radioactive sources. Corresponding simulations were also performed for the 6711 (125)I brachytherapy source, using updated geometric information presented recently in the literature. The uncertainty of the dose distribution around the new source, as well as the dosimetric quantities derived from it according to the Task Group 43 formalism, were determined from the standard error of the mean of simulations for a sample of fifty source models. These source models were prepared by randomly selecting values of geometric parameters from uniform distributions defined by manufacturer stated tolerances. Results are presented in the form of the quantities defined in the update of the Task Group 43 report, as well as a relative dose rate table in Cartesian coordinates. The dose rate distribution of the new source is comparable to that of sources of similar design (IsoSeed I25.S17, Oncoseed 6711, SelectSeed 130.002, Advantage IAI-125A, I-Seed AgX100, Thinseed 9011). Noticeable differences were observed only for the IsoSeed I25.S06 and Best 2301 sources.

Design and characterization of a new high-dose-rate brachytherapy Valencia applicator for larger skin lesions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Candela-Juan, C., E-mail: ccanjuan@gmail.com; Niatsetski, Y.; Laarse, R. van der

Purpose: The aims of this study were (i) to design a new high-dose-rate (HDR) brachytherapy applicator for treating surface lesions with planning target volumes larger than 3 cm in diameter and up to 5 cm in size, using the microSelectron-HDR or Flexitron afterloader (Elekta Brachytherapy) with a {sup 192}Ir source; (ii) to calculate by means of the Monte Carlo (MC) method the dose distribution for the new applicator when it is placed against a water phantom; and (iii) to validate experimentally the dose distributions in water. Methods: The PENELOPE2008 MC code was used to optimize dwell positions and dwell times.more » Next, the dose distribution in a water phantom and the leakage dose distribution around the applicator were calculated. Finally, MC data were validated experimentally for a {sup 192}Ir mHDR-v2 source by measuring (i) dose distributions with radiochromic EBT3 films (ISP); (ii) percentage depth–dose (PDD) curve with the parallel-plate ionization chamber Advanced Markus (PTW); and (iii) absolute dose rate with EBT3 films and the PinPoint T31016 (PTW) ionization chamber. Results: The new applicator is made of tungsten alloy (Densimet) and consists of a set of interchangeable collimators. Three catheters are used to allocate the source at prefixed dwell positions with preset weights to produce a homogenous dose distribution at the typical prescription depth of 3 mm in water. The same plan is used for all available collimators. PDD, absolute dose rate per unit of air kerma strength, and off-axis profiles in a cylindrical water phantom are reported. These data can be used for treatment planning. Leakage around the applicator was also scored. The dose distributions, PDD, and absolute dose rate calculated agree within experimental uncertainties with the doses measured: differences of MC data with chamber measurements are up to 0.8% and with radiochromic films are up to 3.5%. Conclusions: The new applicator and the dosimetric data provided here will be a valuable tool in clinical practice, making treatment of large skin lesions simpler, faster, and safer. Also the dose to surrounding healthy tissues is minimal.« less

Dosimetric characterization of a new directional low-dose rate brachytherapy source.

PubMed

Aima, Manik; DeWerd, Larry A; Mitch, Michael G; Hammer, Clifford G; Culberson, Wesley S

2018-05-24

CivaTech Oncology Inc. (Durham, NC) has developed a novel low-dose rate (LDR) brachytherapy source called the CivaSheet. TM The source is a planar array of discrete elements ("CivaDots") which are directional in nature. The CivaDot geometry and design are considerably different than conventional LDR cylindrically symmetric sources. Thus, a thorough investigation is required to ascertain the dosimetric characteristics of the source. This work investigates the repeatability and reproducibility of a primary source strength standard for the CivaDot and characterizes the CivaDot dose distribution by performing in-phantom measurements and Monte Carlo (MC) simulations. Existing dosimetric formalisms were adapted to accommodate a directional source, and other distinguishing characteristics including the presence of gold shield x-ray fluorescence were addressed in this investigation. Primary air-kerma strength (S K ) measurements of the CivaDots were performed using two free-air chambers namely, the Variable-Aperture Free-Air Chamber (VAFAC) at the University of Wisconsin Medical Radiation Research Center (UWMRRC) and the National Institute of Standards and Technology (NIST) Wide-Angle Free-Air Chamber (WAFAC). An intercomparison of the two free-air chamber measurements was performed along with a comparison of the different assumed CivaDot energy spectra and associated correction factors. Dose distribution measurements of the source were performed in a custom polymethylmethacrylate (PMMA) phantom using Gafchromic TM EBT3 film and thermoluminescent dosimeter (TLD) microcubes. Monte Carlo simulations of the source and the measurement setup were performed using MCNP6 radiation transport code. The CivaDot S K was determined using the two free-air chambers for eight sources with an agreement of better than 1.1% for all sources. The NIST measured CivaDot energy spectrum intensity peaks were within 1.8% of the MC-predicted spectrum intensity peaks. The difference in the net source-specific correction factor determined for the CivaDot free-air chamber measurements for the NIST WAFAC and UW VAFAC was 0.7%. The dose-rate constant analog was determined to be 0.555 cGy h -1 U -1 . The average difference observed in the estimated CivaDot dose-rate constant analog using measurements and MCNP6-predicted value (0.558 cGy h -1 U -1 ) was 0.6% ± 2.3% for eight CivaDot sources using EBT3 film, and -2.6% ± 1.7% using TLD microcube measurements. The CivaDot two-dimensional dose-to-water distribution measured in phantom was compared to the corresponding MC predictions at six depths. The observed difference using a pixel-by-pixel subtraction map of the measured and the predicted dose-to-water distribution was generally within 2-3%, with maximum differences up to 5% of the dose prescribed at the depth of 1 cm. Primary S K measurements of the CivaDot demonstrated good repeatability and reproducibility of the free-air chamber measurements. Measurements of the CivaDot dose distribution using the EBT3 film stack phantom and its subsequent comparison to Monte Carlo-predicted dose distributions were encouraging, given the overall uncertainties. This work will aid in the eventual realization of a clinically viable dosimetric framework for the CivaSheet based on the CivaDot dose distribution. © 2018 American Association of Physicists in Medicine.

The dose distribution of low dose rate Cs-137 in intracavitary brachytherapy: comparison of Monte Carlo simulation, treatment planning calculation and polymer gel measurement

NASA Astrophysics Data System (ADS)

Fragoso, M.; Love, P. A.; Verhaegen, F.; Nalder, C.; Bidmead, A. M.; Leach, M.; Webb, S.

2004-12-01

In this study, the dose distribution delivered by low dose rate Cs-137 brachytherapy sources was investigated using Monte Carlo (MC) techniques and polymer gel dosimetry. The results obtained were compared with a commercial treatment planning system (TPS). The 20 mm and the 30 mm diameter Selectron vaginal applicator set (Nucletron) were used for this study. A homogeneous and a heterogeneous—with an air cavity—polymer gel phantom was used to measure the dose distribution from these sources. The same geometrical set-up was used for the MC calculations. Beyond the applicator tip, differences in dose as large as 20% were found between the MC and TPS. This is attributed to the presence of stainless steel in the applicator and source set, which are not considered by the TPS calculations. Beyond the air cavity, differences in dose of around 5% were noted, due to the TPS assuming a homogeneous water medium. The polymer gel results were in good agreement with the MC calculations for all the cases investigated.

Comparison of the uncertainties of several European low-dose calibration facilities

NASA Astrophysics Data System (ADS)

Dombrowski, H.; Cornejo Díaz, N. A.; Toni, M. P.; Mihelic, M.; Röttger, A.

2018-04-01

The typical uncertainty of a low-dose rate calibration of a detector, which is calibrated in a dedicated secondary national calibration laboratory, is investigated, including measurements in the photon field of metrology institutes. Calibrations at low ambient dose equivalent rates (at the level of the natural ambient radiation) are needed when environmental radiation monitors are to be characterised. The uncertainties of calibration measurements in conventional irradiation facilities above ground are compared with those obtained in a low-dose rate irradiation facility located deep underground. Four laboratories quantitatively evaluated the uncertainties of their calibration facilities, in particular for calibrations at low dose rates (250 nSv/h and 1 μSv/h). For the first time, typical uncertainties of European calibration facilities are documented in a comparison and the main sources of uncertainty are revealed. All sources of uncertainties are analysed, including the irradiation geometry, scattering, deviations of real spectra from standardised spectra, etc. As a fundamental metrological consequence, no instrument calibrated in such a facility can have a lower total uncertainty in subsequent measurements. For the first time, the need to perform calibrations at very low dose rates (< 100 nSv/h) deep underground is underpinned on the basis of quantitative data.

Impact of the Revised 10 CFR 835 on the Neutron Dose Rates at LLNL

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radev, R

2009-01-13

In June 2007, 10 CFR 835 [1] was revised to include new radiation weighting factors for neutrons, updated dosimetric models, and dose terms consistent with the newer ICRP recommendations. A significant aspect of the revised 10 CFR 835 is the adoption of the recommendations outlined in ICRP-60 [2]. The recommended new quantities demand a review of much of the basic data used in protection against exposure to sources of ionizing radiation. The International Commission on Radiation Units and Measurements has defined a number of quantities for use in personnel and area monitoring [3,4,5] including the ambient dose equivalent H*(d) tomore » be used for area monitoring and instrument calibrations. These quantities are used in ICRP-60 and ICRP-74. This report deals only with the changes in the ambient dose equivalent and ambient dose rate equivalent for neutrons as a result of the implementation of the revised 10 CFR 835. In the report, the terms neutron dose and neutron dose rate will be used for convenience for ambient neutron dose and ambient neutron dose rate unless otherwise stated. This report provides a qualitative and quantitative estimate of how much the neutron dose rates at LLNL will change with the implementation of the revised 10 CFR 835. Neutron spectra and dose rates from selected locations at the LLNL were measured with a high resolution spectroscopic neutron dose rate system (ROSPEC) as well as with a standard neutron rem meter (a.k.a., a remball). The spectra obtained at these locations compare well with the spectra from the Radiation Calibration Laboratory's (RCL) bare californium source that is currently used to calibrate neutron dose rate instruments. The measurements obtained from the high resolution neutron spectrometer and dose meter ROSPEC and the NRD dose meter compare within the range of {+-}25%. When the new radiation weighting factors are adopted with the implementation of the revised 10 CFR 835, the measured dose rates will increase by up to 22%. The health physicists should consider this increase for any areas that have dose rates near a posting limit, such as near the 100 mrem/hr for a high radiation area, as this increase in measured dose rate may result in some changes to postings and consequent radiological controls.« less

New era of electronic brachytherapy

PubMed Central

Ramachandran, Prabhakar

2017-01-01

Traditional brachytherapy refers to the placement of radioactive sources on or inside the cancer tissues. Based on the type of sources, brachytherapy can be classified as radionuclide and electronic brachytherapy. Electronic brachytherapy uses miniaturized X-ray sources instead of radionuclides to deliver high doses of radiation. The advantages of electronic brachytherapy include low dose to organs at risk, reduced dose to treating staff, no leakage radiation in off state, less shielding, and no radioactive waste. Most of these systems operate between 50 and 100 kVp and are widely used in the treatment of skin cancer. Intrabeam, Xoft and Papillon systems are also used in the treatment of intra-operative radiotherapy to breast in addition to other treatment sites. The rapid fall-off in the dose due to its low energy is a highly desirable property in brachytherapy and results in a reduced dose to the surrounding normal tissues compared to the Ir-192 source. The Xoft Axxent brachytherapy system uses a 2.25 mm miniaturized X-ray tube and the source almost mimics the high dose rate Ir-192 source in terms of dose rate and it is the only electronic brachytherapy system specifically used in the treatment of cervical cancers. One of the limiting factors that impede the use of electronic brachytherapy for interstitial application is the source dimension. However, it is highly anticipated that the design of miniaturized X-ray tube closer to the dimension of an Ir-192 wire is not too far away, and the new era of electronic brachytherapy has just begun. PMID:28529679

Surface applicator calibration and commissioning of an electronic brachytherapy system for nonmelanoma skin cancer treatment.

PubMed

Rong, Yi; Welsh, James S

2010-10-01

The Xoft Axxent x-ray source has been used for treating nonmelanoma skin cancer since the surface applicators became clinically available in 2009. The authors report comprehensive calibration procedures for the electronic brachytherapy (eBx) system with the surface applicators. The Xoft miniature tube (model S700) generates 50 kVp low-energy x rays. The new surface applicators are available in four sizes of 10, 20, 35, and 50 mm in diameter. The authors' tests include measurements of dose rate, air-gap factor, output stability, depth dose verification, beam flatness and symmetry, and treatment planning with patient specific cutout factors. The TG-61 in-air method was used as a guideline for acquiring nominal dose-rate output at the skin surface. A soft x-ray parallel-plate chamber (PTW T34013) and electrometer was used for the output commissioning. GafChromic EBT films were used for testing the properties of the treatment fields with the skin applicators. Solid water slabs were used to verify the depth dose and cutout factors. Patients with basal cell or squamous cell carcinoma were treated with eBx using a calibrated Xoft system with the low-energy x-ray source and the skin applicators. The average nominal dose-rate output at the skin surface for the 35 mm applicator is 1.35 Gy/min with +/- 5% variation for 16 sources. The dose-rate output and stability (within +/- 5% variation) were also measured for the remaining three applicators. For the same source, the output variation is within 2%. The effective source-surface distance was calculated based on the air-gap measurements for four applicator sizes. The field flatness and symmetry are well within 5%. Percentage depth dose in water was provided by factory measurements and can be verified using solid water slabs. Treatment duration was calculated based on the nominal dose rate, the prescription fraction size, the depth dose percentage, and the cutout factor. The output factor needs to be measured for each case with varying shapes of cutouts. Together with TG-61, the authors' methodology provides comprehensive calibration procedures for medical physicists for using the Xoft eBx system and skin applicators for nonmelanoma skin cancer treatments.

The Fukushima releases: an inverse modelling approach to assess the source term by using gamma dose rate observations

NASA Astrophysics Data System (ADS)

Saunier, Olivier; Mathieu, Anne; Didier, Damien; Tombette, Marilyne; Quélo, Denis; Winiarek, Victor; Bocquet, Marc

2013-04-01

The Chernobyl nuclear accident and more recently the Fukushima accident highlighted that the largest source of error on consequences assessment is the source term estimation including the time evolution of the release rate and its distribution between radioisotopes. Inverse modelling methods have proved to be efficient to assess the source term due to accidental situation (Gudiksen, 1989, Krysta and Bocquet, 2007, Stohl et al 2011, Winiarek et al 2012). These methods combine environmental measurements and atmospheric dispersion models. They have been recently applied to the Fukushima accident. Most existing approaches are designed to use air sampling measurements (Winiarek et al, 2012) and some of them use also deposition measurements (Stohl et al, 2012, Winiarek et al, 2013). During the Fukushima accident, such measurements are far less numerous and not as well distributed within Japan than the dose rate measurements. To efficiently document the evolution of the contamination, gamma dose rate measurements were numerous, well distributed within Japan and they offered a high temporal frequency. However, dose rate data are not as easy to use as air sampling measurements and until now they were not used in inverse modelling approach. Indeed, dose rate data results from all the gamma emitters present in the ground and in the atmosphere in the vicinity of the receptor. They do not allow one to determine the isotopic composition or to distinguish the plume contribution from wet deposition. The presented approach proposes a way to use dose rate measurement in inverse modeling approach without the need of a-priori information on emissions. The method proved to be efficient and reliable when applied on the Fukushima accident. The emissions for the 8 main isotopes Xe-133, Cs-134, Cs-136, Cs-137, Ba-137m, I-131, I-132 and Te-132 have been assessed. The Daiichi power plant events (such as ventings, explosions…) known to have caused atmospheric releases are well identified in the retrieved source term, except for unit 3 explosion where no measurement was available. The comparisons between the simulations of atmospheric dispersion and deposition of the retrieved source term show a good agreement with environmental observations. Moreover, an important outcome of this study is that the method proved to be perfectly suited to crisis management and should contribute to improve our response in case of a nuclear accident.

Sci-Thur PM – Brachytherapy 04: Commissioning and Implementation of a Cobalt-60 High Dose Rate Brachytherapy Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dysart, Jonathan

An Eckert & Ziegler Bebig Co0.A86 cobalt 60 high dose rate (HDR) brachytherapy source was commissioned for clinical use. Long-lived Co-60 HDR sources offer potential logistical and economic advantages over Ir-192 sources, and should be considered for low to medium workload brachytherapy departments where modest increases in treatment times are not a factor. In optimized plans, the Co-60 source provides a similar dose distribution to Ir-192 despite the difference in radiation energy. By switching to Co-60, source exchange frequency can be reduced by a factor of 20, resulting in overall financial savings of more than 50% compared to Ir-192 sources.more » In addition, a reduction in Physicist QA workload of roughly 200 hours over the 5 year life of the Co-60 source is also expected. These benefits should be considered against the modest increases in average treatment time compared to those of Ir-192 sources, as well as the centre-specific needs for operating room shielding modification.« less

Effect of tissue composition on dose distribution in brachytherapy with various photon emitting sources

PubMed Central

Ghorbani, Mahdi; Salahshour, Fateme; Haghparast, Abbas; Knaup, Courtney

2014-01-01

Purpose The aim of this study is to compare the dose in various soft tissues in brachytherapy with photon emitting sources. Material and methods 103Pd, 125I, 169Yb, 192Ir brachytherapy sources were simulated with MCNPX Monte Carlo code, and their dose rate constant and radial dose function were compared with the published data. A spherical phantom with 50 cm radius was simulated and the dose at various radial distances in adipose tissue, breast tissue, 4-component soft tissue, brain (grey/white matter), muscle (skeletal), lung tissue, blood (whole), 9-component soft tissue, and water were calculated. The absolute dose and relative dose difference with respect to 9-component soft tissue was obtained for various materials, sources, and distances. Results There was good agreement between the dosimetric parameters of the sources and the published data. Adipose tissue, breast tissue, 4-component soft tissue, and water showed the greatest difference in dose relative to the dose to the 9-component soft tissue. The other soft tissues showed lower dose differences. The dose difference was also higher for 103Pd source than for 125I, 169Yb, and 192Ir sources. Furthermore, greater distances from the source had higher relative dose differences and the effect can be justified due to the change in photon spectrum (softening or hardening) as photons traverse the phantom material. Conclusions The ignorance of soft tissue characteristics (density, composition, etc.) by treatment planning systems incorporates a significant error in dose delivery to the patient in brachytherapy with photon sources. The error depends on the type of soft tissue, brachytherapy source, as well as the distance from the source. PMID:24790623

On determining dose rate constants spectroscopically

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rodriguez, M.; Rogers, D. W. O.

2013-01-15

Purpose: To investigate several aspects of the Chen and Nath spectroscopic method of determining the dose rate constants of {sup 125}I and {sup 103}Pd seeds [Z. Chen and R. Nath, Phys. Med. Biol. 55, 6089-6104 (2010)] including the accuracy of using a line or dual-point source approximation as done in their method, and the accuracy of ignoring the effects of the scattered photons in the spectra. Additionally, the authors investigate the accuracy of the literature's many different spectra for bare, i.e., unencapsulated {sup 125}I and {sup 103}Pd sources. Methods: Spectra generated by 14 {sup 125}I and 6 {sup 103}Pd seedsmore » were calculated in vacuo at 10 cm from the source in a 2.7 Multiplication-Sign 2.7 Multiplication-Sign 0.05 cm{sup 3} voxel using the EGSnrc BrachyDose Monte Carlo code. Calculated spectra used the initial photon spectra recommended by AAPM's TG-43U1 and NCRP (National Council of Radiation Protection and Measurements) Report 58 for the {sup 125}I seeds, or TG-43U1 and NNDC(2000) (National Nuclear Data Center, 2000) for {sup 103}Pd seeds. The emitted spectra were treated as coming from a line or dual-point source in a Monte Carlo simulation to calculate the dose rate constant. The TG-43U1 definition of the dose rate constant was used. These calculations were performed using the full spectrum including scattered photons or using only the main peaks in the spectrum as done experimentally. Statistical uncertainties on the air kerma/history and the dose rate/history were Less-Than-Or-Slanted-Equal-To 0.2%. The dose rate constants were also calculated using Monte Carlo simulations of the full seed model. Results: The ratio of the intensity of the 31 keV line relative to that of the main peak in {sup 125}I spectra is, on average, 6.8% higher when calculated with the NCRP Report 58 initial spectrum vs that calculated with TG-43U1 initial spectrum. The {sup 103}Pd spectra exhibit an average 6.2% decrease in the 22.9 keV line relative to the main peak when calculated with the TG-43U1 rather than the NNDC(2000) initial spectrum. The measured values from three different investigations are in much better agreement with the calculations using the NCRP Report 58 and NNDC(2000) initial spectra with average discrepancies of 0.9% and 1.7% for the {sup 125}I and {sup 103}Pd seeds, respectively. However, there are no differences in the calculated TG-43U1 brachytherapy parameters using either initial spectrum in both cases. Similarly, there were no differences outside the statistical uncertainties of 0.1% or 0.2%, in the average energy, air kerma/history, dose rate/history, and dose rate constant when calculated using either the full photon spectrum or the main-peaks-only spectrum. Conclusions: Our calculated dose rate constants based on using the calculated on-axis spectrum and a line or dual-point source model are in excellent agreement (0.5% on average) with the values of Chen and Nath, verifying the accuracy of their more approximate method of going from the spectrum to the dose rate constant. However, the dose rate constants based on full seed models differ by between +4.6% and -1.5% from those based on the line or dual-point source approximations. These results suggest that the main value of spectroscopic measurements is to verify full Monte Carlo models of the seeds by comparison to the calculated spectra.« less

Air kerma and absorbed dose standards for reference dosimetry in brachytherapy

PubMed Central

2014-01-01

This article reviews recent developments in primary standards for the calibration of brachytherapy sources, with an emphasis on the currently most common photon-emitting radionuclides. The introduction discusses the need for reference dosimetry in brachytherapy in general. The following section focuses on the three main quantities, i.e. reference air kerma rate, air kerma strength and absorbed dose rate to water, which are currently used for the specification of brachytherapy photon sources and which can be realized with primary standards from first principles. An overview of different air kerma and absorbed dose standards, which have been independently developed by various national metrology institutes over the past two decades, is given in the next two sections. Other dosimetry techniques for brachytherapy will also be discussed. The review closes with an outlook on a possible transition from air kerma to absorbed dose to water-based calibrations for brachytherapy sources in the future. PMID:24814696

A systematic evaluation of the dose-rate constant determined by photon spectrometry for 21 different models of low-energy photon-emitting brachytherapy sources.

PubMed

Chen, Zhe Jay; Nath, Ravinder

2010-10-21

The aim of this study was to perform a systematic comparison of the dose-rate constant (Λ) determined by the photon spectrometry technique (PST) with the consensus value ((CON)Λ) recommended by the American Association of Physicists in Medicine (AAPM) for 21 low-energy photon-emitting interstitial brachytherapy sources. A total of 63 interstitial brachytherapy sources (21 different models with 3 sources per model) containing either (125)I (14 models), (103)Pd (6 models) or (131)Cs (1 model) were included in this study. A PST described by Chen and Nath (2007 Med. Phys. 34 1412-30) was used to determine the dose-rate constant ((PST)Λ) for each source model. Source-dependent variations in (PST)Λ were analyzed systematically against the spectral characteristics of the emitted photons and the consensus values recommended by the AAPM brachytherapy subcommittee. The values of (PST)Λ for the encapsulated sources of (103)Pd, (125)I and (131)Cs varied from 0.661 to 0.678 cGyh(-1) U(-1), 0.959 to 1.024 cGyh(-1)U(-1) and 1.066 to 1.073 cGyh(-1)U(-1), respectively. The relative variation in (PST)Λ among the six (103)Pd source models, caused by variations in photon attenuation and in spatial distributions of radioactivity among the source models, was less than 3%. Greater variations in (PST)Λ were observed among the 14 (125)I source models; the maximum relative difference was over 6%. These variations were caused primarily by the presence of silver in some (125)I source models and, to a lesser degree, by the variations in photon attenuation and in spatial distribution of radioactivity among the source models. The presence of silver generates additional fluorescent x-rays with lower photon energies which caused the (PST)Λ value to vary from 0.959 to 1.019 cGyh(-1)U(-1) depending on the amount of silver used by a given source model. For those (125)I sources that contain no silver, their (PST)Λ was less variable and had values within 1% of 1.024 cGyh(-1)U(-1). For the 16 source models that currently have an AAPM recommended (CON)Λ value, the agreement between (PST)Λ and (CON)Λ was less than 2% for 15 models and was 2.6% for 1 (103)Pd source model. Excellent agreement between (PST)Λ and (CON)Λ was observed for all source models that currently have an AAPM recommended consensus dose-rate constant value. These results demonstrate that the PST is an accurate and robust technique for the determination of the dose-rate constant for low-energy brachytherapy sources.

Design and dosimetric characteristics of a new endocavitary contact radiotherapy system using an electronic brachytherapy source.

PubMed

Richardson, Susan; Garcia-Ramirez, Jose; Lu, Wei; Myerson, Robert J; Parikh, Parag

2012-11-01

To present design aspects and acceptance tests performed for clinical implementation of electronic brachytherapy treatment of early stage rectal adenocarcinoma. A dosimetric comparison is made between the historically used Philips RT-50 unit and the newly developed Axxent(®) Model S700 electronic brachytherapy source manufactured by Xoft (iCad, Inc.). Two proctoscope cones were manufactured by ElectroSurgical Instruments (ESI). Two custom surface applicators were manufactured by Xoft and were designed to fit and interlock with the proctoscope cones from ESI. Dose rates, half value layers (HVL), and percentage depth dose (PDD) measurements were made with the Xoft system and compared to historical RT-50 data. A description of the patient treatment approach and exposure rates during the procedure is also provided. The electronic brachytherapy system has a lower surface dose rate than the RT-50. The dose rate to water on the surface from the Xoft system is approximately 2.1 Gy∕min while the RT-50 is 10-12 Gy∕min. However, treatment times with Xoft are still reasonable. The HVLs and PDDs between the two systems were comparable resulting in similar doses to the target and to regions beyond the target. The exposure rate levels around a patient treatment were acceptable. The standard uncertainty in the dose rate to water on the surface is approximately ±5.2%. The Philips RT-50 unit is an out-of-date radiotherapy machine that is no longer manufactured with limited replacement parts. The use of a custom-designed proctoscope and Xoft surface applicators allows delivery of a well-established treatment with the ease of a modern radiotherapy device. While the dose rate is lower with the use of Xoft, the treatment times are still reasonable. Additionally, personnel may stand farther away from the Xoft radiation source, thus potentially reducing radiation exposure to the operator and other personnel.

Fieldable computer system for determining gamma-ray pulse-height distributions, flux spectra, and dose rates from Little Boy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Moss, C.E.; Lucas, M.C.; Tisinger, E.W.

1984-01-01

Our system consists of a LeCroy 3500 data acquisition system with a built-in CAMAC crate and eight bismuth-germanate detectors 7.62 cm in diameter and 7.62 cm long. Gamma-ray pulse-height distributions are acquired simultaneously for up to eight positions. The system was very carefully calibrated and characterized from 0.1 to 8.3 MeV using gamma-ray spectra from a variety of radioactive sources. By fitting the pulse-height distributions from the sources with a function containing 17 parameters, we determined theoretical repsonse functions. We use these response functions to unfold the distributions to obtain flux spectra. A flux-to-dose-rate conversion curve based on the workmore » of Dimbylow and Francis is then used to obtain dose rates. Direct use of measured spectra and flux-to-dose-rate curves to obtain dose rates avoids the errors that can arise from spectrum dependence in simple gamma-ray dosimeter instruments. We present some gamma-ray doses for the Little Boy assembly operated at low power. These results can be used to determine the exposures of the Hiroshima survivors and thus aid in the establishment of radation exposure limits for the nuclear industry.« less

An analysis of MCNP cross-sections and tally methods for low-energy photon emitters.

PubMed

Demarco, John J; Wallace, Robert E; Boedeker, Kirsten

2002-04-21

Monte Carlo calculations are frequently used to analyse a variety of radiological science applications using low-energy (10-1000 keV) photon sources. This study seeks to create a low-energy benchmark for the MCNP Monte Carlo code by simulating the absolute dose rate in water and the air-kerma rate for monoenergetic point sources with energies between 10 keV and 1 MeV. The analysis compares four cross-section datasets as well as the tally method for collision kerma versus absorbed dose. The total photon attenuation coefficient cross-section for low atomic number elements has changed significantly as cross-section data have changed between 1967 and 1989. Differences of up to 10% are observed in the photoelectric cross-section for water at 30 keV between the standard MCNP cross-section dataset (DLC-200) and the most recent XCOM/NIST tabulation. At 30 keV, the absolute dose rate in water at 1.0 cm from the source increases by 7.8% after replacing the DLC-200 photoelectric cross-sections for water with those from the XCOM/NIST tabulation. The differences in the absolute dose rate are analysed when calculated with either the MCNP absorbed dose tally or the collision kerma tally. Significant differences between the collision kerma tally and the absorbed dose tally can occur when using the DLC-200 attenuation coefficients in conjunction with a modern tabulation of mass energy-absorption coefficients.

Early effects comparison of X-rays delivered at high-dose-rate pulses by a plasma focus device and at low dose rate on human tumour cells.

PubMed

Virelli, A; Zironi, I; Pasi, F; Ceccolini, E; Nano, R; Facoetti, A; Gavoçi, E; Fiore, M R; Rocchi, F; Mostacci, D; Cucchi, G; Castellani, G; Sumini, M; Orecchia, R

2015-09-01

A comparative study has been performed on the effects of high-dose-rate (DR) X-ray beams produced by a plasma focus device (PFMA-3), to exploit its potential medical applications (e.g. radiotherapy), and low-DR X-ray beams produced by a conventional source (XRT). Experiments have been performed at 0.5 and 2 Gy doses on a human glioblastoma cell line (T98G). Cell proliferation rate and potassium outward currents (IK) have been investigated by time lapse imaging and patch clamp recordings. The results showed that PFMA-3 irradiation has a greater capability to reduce the proliferation rate activity with respect to XRT, while it does not affect IK of T98G cells at any of the dose levels tested. XRT irradiation significantly reduces the mean IK amplitude of T98G cells only at 0.5 Gy. This work confirms that the DR, and therefore the source of radiation, is crucial for the planning and optimisation of radiotherapy applications. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Benchmarking of MCNP for calculating dose rates at an interim storage facility for nuclear waste.

PubMed

Heuel-Fabianek, Burkhard; Hille, Ralf

2005-01-01

During the operation of research facilities at Research Centre Jülich, Germany, nuclear waste is stored in drums and other vessels in an interim storage building on-site, which has a concrete shielding at the side walls. Owing to the lack of a well-defined source, measured gamma spectra were unfolded to determine the photon flux on the surface of the containers. The dose rate simulation, including the effects of skyshine, using the Monte Carlo transport code MCNP is compared with the measured dosimetric data at some locations in the vicinity of the interim storage building. The MCNP data for direct radiation confirm the data calculated using a point-kernel method. However, a comparison of the modelled dose rates for direct radiation and skyshine with the measured data demonstrate the need for a more precise definition of the source. Both the measured and the modelled dose rates verified the fact that the legal limits (<1 mSv a(-1)) are met in the area outside the perimeter fence of the storage building to which members of the public have access. Using container surface data (gamma spectra) to define the source may be a useful tool for practical calculations and additionally for benchmarking of computer codes if the discussed critical aspects with respect to the source can be addressed adequately.

Comparison Between Prospectively Electrocardiogram-Gated High-Pitch Mode and Retrospectively Electrocardiogram-Gated Mode for Dual-Source CT Coronary Angiography.

PubMed

Koplay, Mustafa; Celik, Mahmut; Avcı, Ahmet; Erdogan, Hasan; Demir, Kenan; Sivri, Mesut; Nayman, Alaaddin

2015-01-01

We aimed to report the image quality, relationship between heart rate and image quality, amount of contrast agent given to the patients and radiation doses in coronary CT angiography (CTA) obtained by using high-pitch prospectively ECG-gated "Flash Spiral" technique (method A) or retrospectively ECG-gated technique (method B) using 128×2-slice dual-source CT. A total of 110 patients who were evaluated with method A and method B technique with a 128×2-detector dual-source CT device were included in the study. Patients were divided into three groups based on their heart rates during the procedure, and a relationship between heart rate and image quality were evaluated. The relationship between heart rate, gender and radiation dose received by the patients was compared. A total of 1760 segments were evaluated in terms of image quality. Comparison of the relationship between heart rate and image quality revealed a significant difference between heart rate <60 beats/min group and >75 beats/min group whereas <60 beats/min and 60-75 beats/min groups did not differ significantly. The average effective dose for coronary CTA was calculated as 1.11 mSv (0.47-2.01 mSv) for method A and 8.22 mSv (2.19-12.88 mSv) for method B. Method A provided high quality images with doses as low as <1 mSv in selected patients who have low heart rates with a high negative predictive value to rule out coronary artery disease. Although method B increases the amount of effective dose, it provides high diagnostic quality images for patients who have a high heart rate and arrhythmia which makes it is difficult to obtain images.

Dosimetric characterization of the M−15 high‐dose‐rate Iridium−192 brachytherapy source using the AAPM and ESTRO formalism

PubMed Central

Thanh, Minh‐Tri Ho; Munro, John J.

2015-01-01

The Source Production & Equipment Co. (SPEC) model M−15 is a new Iridium−192 brachytherapy source model intended for use as a temporary high‐dose‐rate (HDR) brachytherapy source for the Nucletron microSelectron Classic afterloading system. The purpose of this study is to characterize this HDR source for clinical application by obtaining a complete set of Monte Carlo calculated dosimetric parameters for the M‐15, as recommended by AAPM and ESTRO, for isotopes with average energies greater than 50 keV. This was accomplished by using the MCNP6 Monte Carlo code to simulate the resulting source dosimetry at various points within a pseudoinfinite water phantom. These dosimetric values next were converted into the AAPM and ESTRO dosimetry parameters and the respective statistical uncertainty in each parameter also calculated and presented. The M−15 source was modeled in an MCNP6 Monte Carlo environment using the physical source specifications provided by the manufacturer. Iridium−192 photons were uniformly generated inside the iridium core of the model M−15 with photon and secondary electron transport replicated using photoatomic cross‐sectional tables supplied with MCNP6. Simulations were performed for both water and air/vacuum computer models with a total of 4×109 sources photon history for each simulation and the in‐air photon spectrum filtered to remove low‐energy photons below δ=10%keV. Dosimetric data, including D(r,θ),gL(r),F(r,θ),Φan(r), and φ¯an, and their statistical uncertainty were calculated from the output of an MCNP model consisting of an M−15 source placed at the center of a spherical water phantom of 100 cm diameter. The air kerma strength in free space, SK, and dose rate constant, Λ, also was computed from a MCNP model with M−15 Iridium−192 source, was centered at the origin of an evacuated phantom in which a critical volume containing air at STP was added 100 cm from the source center. The reference dose rate, D˙(r0,θ0)≡D˙(1cm,π/2), is found to be 4.038±0.064 cGy mCi−1 h−1. The air kerma strength, SK, is reported to be 3.632±0.086 cGy cm2 mCi−1 g−1, and the dose rate constant, Λ, is calculated to be 1.112±0.029 cGy h−1 U−1. The normalized dose rate, radial dose function, and anisotropy function with their uncertainties were computed and are represented in both tabular and graphical format in the report. A dosimetric study was performed of the new M−15 Iridium−192 HDR brachytherapy source using the MCNP6 radiation transport code. Dosimetric parameters, including the dose‐rate constant, radial dose function, and anisotropy function, were calculated in accordance with the updated AAPM and ESTRO dosimetric parameters for brachytherapy sources of average energy greater than 50 keV. These data therefore may be applied toward the development of a treatment planning program and for clinical use of the source. PACS numbers: 87.56.bg, 87.53.Jw PMID:26103489

Three-dimensional dosimetric considerations from different point A definitions in cervical cancer low-dose-rate brachytherapy

PubMed Central

Chen, Ting; Kim, Leonard H.; Nelson, Carl; Gabel, Molly; Narra, Venkat; Haffty, Bruce; Yue, Ning J.

2013-01-01

Purpose To investigate the dosimetric difference due to the different point A definitions in cervical cancer low-dose-rate (LDR) intracavitary brachytherapy. Material and methods Twenty CT-based LDR brachytherapy plans of 11 cervical patients were retrospectively reviewed. Two plans with point As following the modified Manchester system which defines point A being 2 cm superior to the cervical os along the tandem and 2 cm lateral (Aos), and the American Brachytherapy Society (ABS) guideline definition in which the point A is 2 cm superior to the vaginal fornices instead of os (Aovoid) were generated. Using the same source strength, two plans prescribed the same dose to Aos and Aovoid. Dosimetric differences between plans including point A dose rate, treatment volume encompassed by the prescription isodose line (TV), and dose rate of 2 cc of the rectum and bladder to the prescription dose were measured. Results On average Aovoid was 8.9 mm superior to Aos along the tandem direction with a standard deviation of 5.4 mm. With the same source strength and arrangement, Aos dose rate was 19% higher than Aovoid dose rate. The average TV(Aovoid) was 118.0 cc, which was 30% more than the average TV(Aos) of 93.0 cc. D2cc/D(Aprescribe) increased from 51% to 60% for rectum, and increased from 89% and 106% for bladder, if the prescription point changed from Aos to Aovoid. Conclusions Different point A definitions lead to significant dose differences. Careful consideration should be given when changing practice from one point A definition to another, to ensure dosimetric and clinical equivalency from the previous clinical experiences. PMID:24474971

Estimation of neutron dose equivalent at the mezzanine of the Advanced Light Source and the laboratory boundary using the ORNL program MORSE.

PubMed

Sun, R K

1990-12-01

To investigate the radiation effect of neutrons near the Advanced Light Source (ALS) at Lawrence Berkeley Laboratory (LBL) with respect to the neutron dose equivalents in nearby occupied areas and at the site boundary, the neutron transport code MORSE, from Oak Ridge National Laboratory (ORNL), was used. These dose equivalents result from both skyshine neutrons transported by air scattering and direct neutrons penetrating the shielding. The ALS neutron sources are a 50-MeV linear accelerator and its transfer line, a 1.5-GeV booster, a beam extraction line, and a 1.9-GeV storage ring. The most conservative total occupational-dose-equivalent rate in the center of the ALS mezzanine, 39 m from the ALS center, was found to be 1.14 X 10(-3) Sv y-1 per 2000-h "occupational" year, and the total environmental-dose-equivalent rate at the ALS boundary, 125 m from the ALS center, was found to be 3.02 X 10(-4) Sv y-1 per 8760-h calendar year. More realistic dose-equivalent rates, using the nominal (expected) storage-ring current, were calculated to be 1.0 X 10(-4) Sv y-1 and 2.65 X 10(-5) Sv y-1 occupational year and calendar year, respectively, which are much lower than the DOE reporting levels.

SU-F-T-15: Evaluation of 192Ir, 60Co and 169Yb Sources for High Dose Rate Prostate Brachytherapy Inverse Planning Using An Interior Point Constraint Generation Algorithm

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mok Tsze Chung, E; Aleman, D; Safigholi, H

Purpose: The effectiveness of using a combination of three sources, {sup 60}Co, {sup 192}Ir and {sup 169}Yb, is analyzed. Different combinations are compared against a single {sup 192}Ir source on prostate cancer cases. A novel inverse planning interior point algorithm is developed in-house to generate the treatment plans. Methods: Thirteen prostate cancer patients are separated into two groups: Group A includes eight patients with the prostate as target volume, while group B consists of four patients with a boost nodule inside the prostate that is assigned 150% of the prescription dose. The mean target volume is 35.7±9.3cc and 30.6±8.5cc formore » groups A and B, respectively. All patients are treated with each source individually, then with paired sources, and finally with all three sources. To compare the results, boost volume V150 and D90, urethra Dmax and D10, and rectum Dmax and V80 are evaluated. For fair comparison, all plans are normalized to a uniform V100=100. Results: Overall, double- and triple-source plans were better than single-source plans. The triple-source plans resulted in an average decrease of 21.7% and 1.5% in urethra Dmax and D10, respectively, and 8.0% and 0.8% in rectum Dmax and V80, respectively, for group A. For group B, boost volume V150 and D90 increased by 4.7% and 3.0%, respectively, while keeping similar dose delivered to the urethra and rectum. {sup 60}Co and {sup 192}Ir produced better plans than their counterparts in the double-source category, whereas {sup 60}Co produced more favorable results than the remaining individual sources. Conclusion: This study demonstrates the potential advantage of using a combination of two or three sources, reflected in dose reduction to organs-at-risk and more conformal dose to the target. three sources, reflected in dose reduction to organs-at-risk and more conformal dose to the target. Our results show that {sup 60}Co, {sup 192}Ir and {sup 169}Yb produce the best plans when used simultaneously and can thus be an alternative to {sup 192}Ir-only in high-dose-rate prostate brachytherapy.« less

Monte Carlo Determination of Dosimetric Parameters of a New (125)I Brachytherapy Source According to AAPM TG-43 (U1) Protocol.

PubMed

Baghani, Hamid Reza; Lohrabian, Vahid; Aghamiri, Mahmoud Reza; Robatjazi, Mostafa

2016-03-01

(125)I is one of the important sources frequently used in brachytherapy. Up to now, several different commercial models of this source type have been introduced to the clinical radiation oncology applications. Recently, a new source model, IrSeed-125, has been added to this list. The aim of the present study is to determine the dosimetric parameters of this new source model based on the recommendations of TG-43 (U1) protocol using Monte Carlo simulation. The dosimetric characteristics of Ir-125 including dose rate constant, radial dose function, 2D anisotropy function and 1D anisotropy function were determined inside liquid water using MCNPX code and compared to those of other commercially available iodine sources. The dose rate constant of this new source was found to be 0.983+0.015 cGyh-1U-1 that was in good agreement with the TLD measured data (0.965 cGyh-1U-1). The 1D anisotropy function at 3, 5, and 7 cm radial distances were obtained as 0.954, 0.953 and 0.959, respectively. The results of this study showed that the dosimetric characteristics of this new brachytherapy source are comparable with those of other commercially available sources. Furthermore, the simulated parameters were in accordance with the previously measured ones. Therefore, the Monte Carlo calculated dosimetric parameters could be employed to obtain the dose distribution around this new brachytherapy source based on TG-43 (U1) protocol.

SU-E-T-284: Revisiting Reference Dosimetry for the Model S700 Axxent 50 KV{sub p} Electronic Brachytherapy Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiatt, JR; Rivard, MJ

2014-06-01

Purpose: The model S700 Axxent electronic brachytherapy source by Xoft was characterized in 2006 by Rivard et al. The source design was modified in 2006 to include a plastic centering insert at the source tip to more accurately position the anode. The objectives of the current study were to establish an accurate Monte Carlo source model for simulation purposes, to dosimetrically characterize the new source and obtain its TG-43 brachytherapy dosimetry parameters, and to determine dose differences between the source with and without the centering insert. Methods: Design information from dissected sources and vendor-supplied CAD drawings were used to devisemore » the source model for radiation transport simulations of dose distributions in a water phantom. Collision kerma was estimated as a function of radial distance, r, and polar angle, θ, for determination of reference TG-43 dosimetry parameters. Simulations were run for 10{sup 10} histories, resulting in statistical uncertainties on the transverse plane of 0.03% at r=1 cm and 0.08% at r=10 cm. Results: The dose rate distribution the transverse plane did not change beyond 2% between the 2006 model and the current study. While differences exceeding 15% were observed near the source distal tip, these diminished to within 2% for r>1.5 cm. Differences exceeding a factor of two were observed near θ=150° and in contact with the source, but diminished to within 20% at r=10 cm. Conclusions: Changes in source design influenced the overall dose rate and distribution by more than 2% over a third of the available solid angle external from the source. For clinical applications using balloons or applicators with tissue located within 5 cm from the source, dose differences exceeding 2% were observed only for θ>110°. This study carefully examined the current source geometry and presents a modern reference TG-43 dosimetry dataset for the model S700 source.« less

TU-D-201-07: Severity Indication in High Dose Rate Brachytherapy Emergency Response Procedure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, K; Rustad, F

Purpose: Understanding the corresponding dose to different staff during the High Dose Rate (HDR) Brachytherapy emergency response procedure could help to develop a strategy in efficiency and effective action. In this study, the variation and risk analysis methodology was developed to simulation the HDR emergency response procedure based on severity indicator. Methods: A GammaMedplus iX HDR unit from Varian Medical System was used for this simulation. The emergency response procedure was decomposed based on risk management methods. Severity indexes were used to identify the impact of a risk occurrence on the step including dose to patient and dose to operationmore » staff by varying the time, HDR source activity, distance from the source to patient and staff and the actions. These actions in 7 steps were to press the interrupt button, press emergency shutoff switch, press emergency button on the afterloader keypad, turn emergency hand-crank, remove applicator from the patient, disconnect transfer tube and move afterloader from the patient, and execute emergency surgical recovery. Results: Given the accumulated time in second at the assumed 7 steps were 15, 5, 30, 15, 180, 120, 1800, and the dose rate of HDR source is 10 Ci, the accumulated dose in cGy to patient at 1cm distance were 188, 250, 625, 813, 3063, 4563 and 27063, and the accumulated exposure in rem to operator at outside the vault, 1m and 10cm distance were 0.0, 0.0, 0.1, 0.1, 22.6, 37.6 and 262.6. The variation was determined by the operators in action at different time and distance from the HDR source. Conclusion: The time and dose were estimated for a HDR unit emergency response procedure. It provided information in making optimal decision during the emergency procedure. Further investigation would be to optimize and standardize the responses for other emergency procedure by time-spatial-dose severity function.« less

SU-G-201-17: Verification of Dose Distributions From High-Dose-Rate Brachytherapy Ir-192 Source Using a Multiple-Array-Diode-Detector (MapCheck2)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harpool, K; De La Fuente Herman, T; Ahmad, S

Purpose: To investigate quantitatively the accuracy of dose distributions for the Ir-192 high-dose-rate (HDR) brachytherapy source calculated by the Brachytherapy-Planning system (BPS) and measured using a multiple-array-diode-detector in a heterogeneous medium. Methods: A two-dimensional diode-array-detector system (MapCheck2) was scanned with a catheter and the CT-images were loaded into the Varian-Brachytherapy-Planning which uses TG-43-formalism for dose calculation. Treatment plans were calculated for different combinations of one dwell-position and varying irradiation times and different-dwell positions and fixed irradiation time with the source placed 12mm from the diode-array plane. The calculated dose distributions were compared to the measured doses with MapCheck2 delivered bymore » an Ir-192-source from a Nucletron-Microselectron-V2-remote-after-loader. The linearity of MapCheck2 was tested for a range of dwell-times (2–600 seconds). The angular effect was tested with 30 seconds irradiation delivered to the central-diode and then moving the source away in increments of 10mm. Results: Large differences were found between calculated and measured dose distributions. These differences are mainly due to absence of heterogeneity in the dose calculation and diode-artifacts in the measurements. The dose differences between measured and calculated due to heterogeneity ranged from 5%–12% depending on the position of the source relative to the diodes in MapCheck2 and different heterogeneities in the beam path. The linearity test of the diode-detector showed 3.98%, 2.61%, and 2.27% over-response at short irradiation times of 2, 5, and 10 seconds, respectively, and within 2% for 20 to 600 seconds (p-value=0.05) which depends strongly on MapCheck2 noise. The angular dependency was more pronounced at acute angles ranging up to 34% at 5.7 degrees. Conclusion: Large deviations between measured and calculated dose distributions for HDR-brachytherapy with Ir-192 may be improved when considering medium heterogeneity and dose-artifact of the diodes. This study demonstrates that multiple-array-diode-detectors provide practical and accurate dosimeter to verify doses delivered from the brachytherapy Ir-192-source.« less

Interstitial rotating shield brachytherapy for prostate cancer.

PubMed

Adams, Quentin E; Xu, Jinghzu; Breitbach, Elizabeth K; Li, Xing; Enger, Shirin A; Rockey, William R; Kim, Yusung; Wu, Xiaodong; Flynn, Ryan T

2014-05-01

To present a novel needle, catheter, and radiation source system for interstitial rotating shield brachytherapy (I-RSBT) of the prostate. I-RSBT is a promising technique for reducing urethra, rectum, and bladder dose relative to conventional interstitial high-dose-rate brachytherapy (HDR-BT). A wire-mounted 62 GBq(153)Gd source is proposed with an encapsulated diameter of 0.59 mm, active diameter of 0.44 mm, and active length of 10 mm. A concept model I-RSBT needle/catheter pair was constructed using concentric 50 and 75 μm thick nickel-titanium alloy (nitinol) tubes. The needle is 16-gauge (1.651 mm) in outer diameter and the catheter contains a 535 μm thick platinum shield. I-RSBT and conventional HDR-BT treatment plans for a prostate cancer patient were generated based on Monte Carlo dose calculations. In order to minimize urethral dose, urethral dose gradient volumes within 0-5 mm of the urethra surface were allowed to receive doses less than the prescribed dose of 100%. The platinum shield reduced the dose rate on the shielded side of the source at 1 cm off-axis to 6.4% of the dose rate on the unshielded side. For the case considered, for the same minimum dose to the hottest 98% of the clinical target volume (D(98%)), I-RSBT reduced urethral D(0.1cc) below that of conventional HDR-BT by 29%, 33%, 38%, and 44% for urethral dose gradient volumes within 0, 1, 3, and 5 mm of the urethra surface, respectively. Percentages are expressed relative to the prescription dose of 100%. For the case considered, for the same urethral dose gradient volumes, rectum D(1cc) was reduced by 7%, 6%, 6%, and 6%, respectively, and bladder D(1cc) was reduced by 4%, 5%, 5%, and 6%, respectively. Treatment time to deliver 20 Gy with I-RSBT was 154 min with ten 62 GBq (153)Gd sources. For the case considered, the proposed(153)Gd-based I-RSBT system has the potential to lower the urethral dose relative to HDR-BT by 29%-44% if the clinician allows a urethral dose gradient volume of 0-5 mm around the urethra to receive a dose below the prescription. A multisource approach is necessary in order to deliver the proposed (153)Gd-based I-RSBT technique in reasonable treatment times.

Performance assessment of the BEBIG MultiSource® high dose rate brachytherapy treatment unit

NASA Astrophysics Data System (ADS)

Palmer, Antony; Mzenda, Bongile

2009-12-01

A comprehensive system characterisation was performed of the Eckert & Ziegler BEBIG GmbH MultiSource® High Dose Rate (HDR) brachytherapy treatment unit with an 192Ir source. The unit is relatively new to the UK market, with the first installation in the country having been made in the summer of 2009. A detailed commissioning programme was devised and is reported including checks of the fundamental parameters of source positioning, dwell timing, transit doses and absolute dosimetry of the source. Well chamber measurements, autoradiography and video camera analysis techniques were all employed. The absolute dosimetry was verified by the National Physical Laboratory, UK, and compared to a measurement based on a calibration from PTB, Germany, and the supplied source certificate, as well as an independent assessment by a visiting UK centre. The use of the 'Krieger' dosimetry phantom has also been evaluated. Users of the BEBIG HDR system should take care to avoid any significant bend in the transfer tube, as this will lead to positioning errors of the source, of up to 1.0 mm for slight bends, 2.0 mm for moderate bends and 5.0 mm for extreme curvature (depending on applicators and transfer tube used) for the situations reported in this study. The reason for these errors and the potential clinical impact are discussed. Users should also note the methodology employed by the system for correction of transit doses, and that no correction is made for the initial and final transit doses. The results of this investigation found that the uncorrected transit doses lead to small errors in the delivered dose at the first dwell position, of up to 2.5 cGy at 2 cm (5.6 cGy at 1 cm) from a 10 Ci source, but the transit dose correction for other dwells was accurate within 0.2 cGy. The unit has been mechanically reliable, and source positioning accuracy and dwell timing have been reproducible, with overall performance similar to other existing HDR equipment. The unit is capable of high quality brachytherapy treatment delivery, taking the above factors into account.

Primary Beam Air Kerma Dependence on Distance from Cargo and People Scanners

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strom, Daniel J.; Cerra, Frank

The distance dependence of air kerma or dose rate of the primary radiation beam is not obvious for security scanners of cargo and people in which there is relative motion between a collimated source and the person or object being imaged. To study this problem, one fixed line source and three moving-source scan-geometry cases are considered, each characterized by radiation emanating perpendicular to an axis. The cases are 1) a stationary line source of radioactive material, e.g., contaminated solution in a pipe; 2) a moving, uncollimated point source of radiation that is shuttered or off when it is stationary; 3)more » a moving, collimated point source of radiation that is shuttered or off when it is stationary; and 4) a translating, narrow “pencil” beam emanating in a flying-spot, raster pattern. Each case is considered for short and long distances compared to the line source length or path traversed by a moving source. The short distance model pertains mostly to dose to objects being scanned and personnel associated with the screening operation. The long distance model pertains mostly to potential dose to bystanders. For radionuclide sources, the number of nuclear transitions that occur a) per unit length of a line source, or b) during the traversal of a point source, is a unifying concept. The “universal source strength” of air kerma rate at a meter from the source can be used to describe x-ray machine or radionuclide sources. For many cargo and people scanners with highly collimated fan or pencil beams, dose varies as the inverse of the distance from the source in the near field and with the inverse square of the distance beyond a critical radius. Ignoring the inverse square dependence and using inverse distance dependence is conservative in the sense of tending to overestimate dose.« less

Primary Beam Air Kerma Dependence on Distance from Cargo and People Scanners.

PubMed

Strom, Daniel J; Cerra, Frank

2016-06-01

The distance dependence of air kerma or dose rate of the primary radiation beam is not obvious for security scanners of cargo and people in which there is relative motion between a collimated source and the person or object being imaged. To study this problem, one fixed line source and three moving-source scan-geometry cases are considered, each characterized by radiation emanating perpendicular to an axis. The cases are 1) a stationary line source of radioactive material, e.g., contaminated solution in a pipe; 2) a moving, uncollimated point source of radiation that is shuttered or off when it is stationary; 3) a moving, collimated point source of radiation that is shuttered or off when it is stationary; and 4) a translating, narrow "pencil" beam emanating in a flying-spot, raster pattern. Each case is considered for short and long distances compared to the line source length or path traversed by a moving source. The short distance model pertains mostly to dose to objects being scanned and personnel associated with the screening operation. The long distance model pertains mostly to potential dose to bystanders. For radionuclide sources, the number of nuclear transitions that occur a) per unit length of a line source or b) during the traversal of a point source is a unifying concept. The "universal source strength" of air kerma rate at 1 m from the source can be used to describe x-ray machine or radionuclide sources. For many cargo and people scanners with highly collimated fan or pencil beams, dose varies as the inverse of the distance from the source in the near field and with the inverse square of the distance beyond a critical radius. Ignoring the inverse square dependence and using inverse distance dependence is conservative in the sense of tending to overestimate dose.

Calibration of Photon Sources for Brachytherapy

NASA Astrophysics Data System (ADS)

Rijnders, Alex

Source calibration has to be considered an essential part of the quality assurance program in a brachytherapy department. Not only it will ensure that the source strength value used for dose calculation agrees within some predetermined limits to the value stated on the source certificate, but also it will ensure traceability to international standards. At present calibration is most often still given in terms of reference air kerma rate, although calibration in terms of absorbed dose to water would be closer to the users interest. It can be expected that in a near future several standard laboratories will be able to offer this latter service, and dosimetry protocols will have to be adapted in this way. In-air measurement using ionization chambers (e.g. a Baldwin—Farmer ionization chamber for 192Ir high dose rate HDR or pulsed dose rate PDR sources) is still considered the method of choice for high energy source calibration, but because of their ease of use and reliability well type chambers are becoming more popular and are nowadays often recommended as the standard equipment. For low energy sources well type chambers are in practice the only equipment available for calibration. Care should be taken that the chamber is calibrated at the standard laboratory for the same source type and model as used in the clinic, and using the same measurement conditions and setup. Several standard laboratories have difficulties to provide these calibration facilities, especially for the low energy seed sources (125I and 103Pd). Should a user not be able to obtain properly calibrated equipment to verify the brachytherapy sources used in his department, then at least for sources that are replaced on a regular basis, a consistency check program should be set up to ensure a minimal level of quality control before these sources are used for patient treatment.

[Developments in brachytherapy].

PubMed

Ikeda, H

1995-09-01

Brachytherapy is one of the ideal methods of radiotherapy because of the concentration of a high dose on the target. Recent developments, including induction of afterloading method, utilization of small-sized high-activity sources such as Iridium-192, and induction of high technology and computerization, have made for shortening of irradiation time and source handling, which has led to easier management of the patient during treatment. Dose distribution at high dose rate (HDR) is at least as good as that of low dose rate (LDR), and selection of fractionation and treatment time assures even greater biological effects on hypoxic tumor cells than LDR. Experience with HDR brachytherapy in uterine cervix cancer using Cobalt-60 during the past 20 years in this country has gradually been evaluated in U.S. and Europe. The indications for HDR treatment have extended to esophagus, bronchus, bile duct, brain, intraoperative placement of source guide, and perineal region using templates, as well as the conventional use for uterus, tongue and so on.

A new treatment planning formalism for catheter-based beta sources used in intravascular brachytherapy.

PubMed

Patel, N S; Chiu-Tsao, S T; Tsao, H S; Harrison, L B

2001-01-01

Intravascular brachytherapy (IVBT) is an emerging modality for the treatment of atherosclerotic lesions in the artery. As part of the refinement in this rapidly evolving modality of treatment, the current simplistic dosimetry approach based on a fixed-point prescription must be challenged by future rigorous dosimetry method employing image-based three-dimensional (3D) treatment planning. The goals of 3D IVBT treatment planning calculations include (1) achieving high accuracy in a slim cylindrical region of interest, (2) accounting for the edge effect around the source ends, and (3) supporting multiple dwell positions. The formalism recommended by Task Group 60 (TG-60) of the American Association of Physicists in Medicine (AAPM) is applicable for gamma sources, as well as short beta sources with lengths less than twice the beta particle range. However, for the elongated beta sources and/or seed trains with lengths greater than twice the beta range, a new formalism is required to handle their distinctly different dose characteristics. Specifically, these characteristics consist of (a) flat isodose curves in the central region, (b) steep dose gradient at the source ends, and (c) exponential dose fall-off in the radial direction. In this paper, we present a novel formalism that evolved from TG-60 in maintaining the dose rate as a product of four key quantities. We propose to employ cylindrical coordinates (R, Z, phi), which are more natural and suitable to the slim cylindrical shape of the volume of interest, as opposed to the spherical coordinate system (r, theta, phi) used in the TG-60 formalism. The four quantities used in this formalism include (1) the distribution factor, H(R, Z), (2) the modulation function, M(R, Z), (3) the transverse dose function, h(R), and (4) the reference dose rate at 2 mm along the perpendicular bisector, D(R0=2 mm, Z0=0). The first three are counterparts of the geometry factor, the anisotropy function and the radial dose function in the TG-60 formalism, respectively. The reference dose rate is identical to that recommended by TG-60. The distribution factor is intended to resemble the dose profile due to the spatial distribution of activity in the elongated beta source, and it is a modified Fermi-Dirac function in mathematical form. The utility of this formalism also includes the slow-varying nature of the modulation function, allowing for more accurate treatment planning calculations based on interpolation. The transverse dose function describes the exponential fall-off of the dose in the radial direction, and an exponential or a polynomial can fit it. Simultaneously, the decoupling nature of these dose-related quantities facilitates image-based 3D treatment planning calculations for long beta sources used in IVBT. The new formalism also supports the dosimetry involving multiple dwell positions required for lesions longer than the source length. An example of the utilization of this formalism is illustrated for a 90Y coil source in a carbon dioxide-filled balloon. The pertinent dosimetric parameters were generated and tabulated for future use.

Determination of spatial dose distribution in UCC treatments with LDR brachytherapy using Monte Carlo methods.

PubMed

Benites-Rengifo, Jorge Luis; Vega-Carrillo, Hector Rene

2018-05-19

Using Monte Carlos methods, with the MCNP5 code, a gynecological phantom and a vaginal cylinder were modeled. The spatial distribution of absorbed dose rates in Uterine Cervical Cancer treatment through low dose rate brachytherapy was determined. A liquid water gynecology computational phantom, including a vaginal cylinder applicator made of Lucite, was designed. The applicator has a linear array of four radioactive sources of Cesium 137. Around the vaginal cylinder, 13 water spherical cells of 0.5 cm-diameter were modeled to calculate absorbed dose emulating the procedure made by the treatment planning system. The gamma-ray fluence distribution was estimated, as well as the absorbed doses resulting approximately symmetrical for cells located at upper and lower of vaginal cylinder. Obtained results allow the use of the radioactive decay law to determine dose rate for Uterine Cervical Cancer using low dose rate brachytherapy. Copyright © 2018 Elsevier Ltd. All rights reserved.

Development and implementation of a remote audit tool for high dose rate (HDR) Ir-192 brachytherapy using optically stimulated luminescence dosimetry

PubMed Central

Casey, Kevin E.; Alvarez, Paola; Kry, Stephen F.; Howell, Rebecca M.; Lawyer, Ann; Followill, David

2013-01-01

Purpose: The aim of this work was to create a mailable phantom with measurement accuracy suitable for Radiological Physics Center (RPC) audits of high dose-rate (HDR) brachytherapy sources at institutions participating in National Cancer Institute-funded cooperative clinical trials. Optically stimulated luminescence dosimeters (OSLDs) were chosen as the dosimeter to be used with the phantom. Methods: The authors designed and built an 8 × 8 × 10 cm3 prototype phantom that had two slots capable of holding Al2O3:C OSLDs (nanoDots; Landauer, Glenwood, IL) and a single channel capable of accepting all 192Ir HDR brachytherapy sources in current clinical use in the United States. The authors irradiated the phantom with Nucletron and Varian 192Ir HDR sources in order to determine correction factors for linearity with dose and the combined effects of irradiation energy and phantom characteristics. The phantom was then sent to eight institutions which volunteered to perform trial remote audits. Results: The linearity correction factor was kL = (−9.43 × 10−5 × dose) + 1.009, where dose is in cGy, which differed from that determined by the RPC for the same batch of dosimeters using 60Co irradiation. Separate block correction factors were determined for current versions of both Nucletron and Varian 192Ir HDR sources and these vendor-specific correction factors differed by almost 2.6%. For the Nucletron source, the correction factor was 1.026 [95% confidence interval (CI) = 1.023–1.028], and for the Varian source, it was 1.000 (95% CI = 0.995–1.005). Variations in lateral source positioning up to 0.8 mm and distal/proximal source positioning up to 10 mm had minimal effect on dose measurement accuracy. The overall dose measurement uncertainty of the system was estimated to be 2.4% and 2.5% for the Nucletron and Varian sources, respectively (95% CI). This uncertainty was sufficient to establish a ±5% acceptance criterion for source strength audits under a formal RPC audit program. Trial audits of four Nucletron sources and four Varian sources revealed an average RPC-to-institution dose ratio of 1.000 (standard deviation = 0.011). Conclusions: The authors have created an OSLD-based 192Ir HDR brachytherapy source remote audit tool which offers sufficient dose measurement accuracy to allow the RPC to establish a remote audit program with a ±5% acceptance criterion. The feasibility of the system has been demonstrated with eight trial audits to date. PMID:24320455

The nonuniformity of antibody distribution in the kidney and its influence on dosimetry.

PubMed

Flynn, Aiden A; Pedley, R Barbara; Green, Alan J; Dearling, Jason L; El-Emir, Ethaar; Boxer, Geoffrey M; Boden, Robert; Begent, Richard H J

2003-02-01

The therapeutic efficacy of radiolabeled antibody fragments can be limited by nephrotoxicity, particularly when the kidney is the major route of extraction from the circulation. Conventional dose estimates in kidney assume uniform dose deposition, but we have shown increased antibody localization in the cortex after glomerular filtration. The purpose of this study was to measure the radioactivity in cortex relative to medulla for a range of antibodies and to assess the validity of the assumption of uniformity of dose deposition in the whole kidney and in the cortex for these antibodies with a range of radionuclides. Storage phosphor plate technology (radioluminography) was used to acquire images of the distributions of a range of antibodies of various sizes, labeled with 125I, in kidney sections. This allowed the calculation of the antibody concentration in the cortex relative to the medulla. Beta-particle point dose kernels were then used to generate the dose-rate distributions from 14C, 131I, 186Re, 32P and 90Y. The correlation between the actual dose-rate distribution and the corresponding distribution calculated assuming uniform antibody distribution throughout the kidney was used to test the validity of estimating dose by assuming uniformity in the kidney and in the cortex. There was a strong inverse relationship between the ratio of the radioactivity in the cortex relative to that in the medulla and the antibody size. The nonuniformity of dose deposition was greatest with the smallest antibody fragments but became more uniform as the range of the emissions from the radionuclide increased. Furthermore, there was a strong correlation between the actual dose-rate distribution and the distribution when assuming a uniform source in the kidney for intact antibodies along with medium- to long-range radionuclides, but there was no correlation for small antibody fragments with any radioisotope or for short-range radionuclides with any antibody. However, when the cortex was separated from the whole kidney, the correlation between the actual dose-rate distribution and the assumed dose-rate distribution, if the source was uniform, increased significantly. During radioimmunotherapy, the extent of nonuniformity of dose deposition in the kidney depends on the properties of the antibody and radionuclide. For dosimetry estimates, the cortex should be taken as a separate source region when the radiopharmaceutical is small enough to be filtered by the glomerulus.

Brachytherapy for Prostate Cancer: A Systematic Review

PubMed Central

Koukourakis, Georgios; Kelekis, Nikolaos; Armonis, Vassilios; Kouloulias, Vassilios

2009-01-01

Low-dose rate brachytherapy has become a mainstream treatment option for men diagnosed with prostate cancer because of excellent long-term treatment outcomes in low-, intermediate-, and high-risk patients. To a great extend due to patient lead advocacy for minimally invasive treatment options, high-quality prostate implants have become widely available in the US, Europe, and Japan. High-dose-rate (HDR) afterloading brachytherapy in the management of localised prostate cancer has practical, physical, and biological advantages over low-dose-rate seed brachytherapy. There are no free live sources used, no risk of source loss, and since the implant is a temporary procedure following discharge no issues with regard to radioprotection use of existing facilities exist. Patients with localized prostate cancer may benefit from high-dose-rate brachytherapy, which may be used alone in certain circumstances or in combination with external-beam radiotherapy in other settings. The purpose of this paper is to present the essentials of brachytherapies techniques along with the most important studies that support their effectiveness in the treatment of prostate cancer. PMID:19730753

Development of a technique and conceptual design of a survey instrument for beta dosimetry in the nuclear power industry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Murphy, R.O.

1986-01-01

Before an employee of the nuclear power industry can be assigned to work in an area with radiation hazards, the total dose rate from all radiation present should be known to determine the risk. As the plants age, the level of maintenance has increased and certain tasks have required the workers to be exposed to intense beta radiation fields. Currently available survey instruments do not accurately assess the beta dose or dose rate in many circumstances due to several factors, including the fluctuation of the response of the detector due to the variation in the energy of the beta particlesmore » comprising the radiation field. This research involved developing a technique for calculating the beta dose rate, using the differential energy spectrum and the fluence rate for the beta particles, the fundamental features of the beta radiation. The energy spectrum was used to determine a spectrum weighted average mass stopping power (SWAMPS). The SWAMPS, when multiplied by the fluence rate, gives the energy deposited per unit mass per second, which is the absorbed dose rate for the beta radiation. Reference sources were developed and calibrated using an extrapolation chamber that had, itself, been calibrated using beta sources at the National Bureau of Standards. Different spectrometry systems were tested for applicability to the SWAMPS technique.« less

SU-F-T-58: Dosimetric Evaluation of Breast Tissue Composition for Electronic Brachytherapy (BET) Source In High Dose Rate Accelerated Partial Breast (APBI) Irradiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Taylor, W; Johnson, D; Ahmad, S

Purpose: To quantitatively evaluate the dosimetric impact of differing breast tissue compositions for electronic brachytherapy source for high dose rate accelerated partial breast irradiation. Methods: A series of Monte Carlo Simulation were created using the GEANT4 toolkit (version 10.0). The breast phantom was modeled as a semi-circle with a radius of 5.0 cm. A water balloon with a radius of 1.5 cm was located in the phantom with the Xoft AxxentTM EBT source placed at center as a point source. A mixed of two tissue types (adipose and glandular tissue) was assigned as the materials for the breast phantom withmore » different weight ratios. The proportionality of glandular and adipose tissue was simulated in four different fashions, 80/20, 70/30, 50/50 and 30/70 respectively. The custom energy spectrum for the 50 kVp XOFT source was provided via the manufacturer and used to generate incident photons. The dose distributions were recorded using a parallel three dimensional mesh with a size of 30 × 30 × 30 cm3 with 1 × 1 × 1 mm3 voxels. The simulated doses absorbed along the transverse axis were normalized at the distance of 1 cm and then compared with the calculations using standard TG-43 formalism. Results: All simulations showed underestimation of dose beyond balloon surface compared to standard TG-43 calculations. The maximum percentage differences within 2 cm distance from balloon surface were found to be 18%, 11%, 10% and 8% for the fat breast (30/70), standard breast (50/50), dense breast (70/30 and 80/20), respectively. Conclusion: The accuracy of dose calculations for low energy EBT source was limited when considering tissue heterogeneous composition. The impact of atomic number on photo-electric effect for lower energy Brachytherapy source is not accounted for and resulting in significant errors in dose calculation.« less

Design and implementation of wireless dose logger network for radiological emergency decision support system.

PubMed

Gopalakrishnan, V; Baskaran, R; Venkatraman, B

2016-08-01

A decision support system (DSS) is implemented in Radiological Safety Division, Indira Gandhi Centre for Atomic Research for providing guidance for emergency decision making in case of an inadvertent nuclear accident. Real time gamma dose rate measurement around the stack is used for estimating the radioactive release rate (source term) by using inverse calculation. Wireless gamma dose logging network is designed, implemented, and installed around the Madras Atomic Power Station reactor stack to continuously acquire the environmental gamma dose rate and the details are presented in the paper. The network uses XBee-Pro wireless modules and PSoC controller for wireless interfacing, and the data are logged at the base station. A LabView based program is developed to receive the data, display it on the Google Map, plot the data over the time scale, and register the data in a file to share with DSS software. The DSS at the base station evaluates the real time source term to assess radiation impact.

Design and implementation of wireless dose logger network for radiological emergency decision support system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gopalakrishnan, V.; Baskaran, R.; Venkatraman, B.

A decision support system (DSS) is implemented in Radiological Safety Division, Indira Gandhi Centre for Atomic Research for providing guidance for emergency decision making in case of an inadvertent nuclear accident. Real time gamma dose rate measurement around the stack is used for estimating the radioactive release rate (source term) by using inverse calculation. Wireless gamma dose logging network is designed, implemented, and installed around the Madras Atomic Power Station reactor stack to continuously acquire the environmental gamma dose rate and the details are presented in the paper. The network uses XBee–Pro wireless modules and PSoC controller for wireless interfacing,more » and the data are logged at the base station. A LabView based program is developed to receive the data, display it on the Google Map, plot the data over the time scale, and register the data in a file to share with DSS software. The DSS at the base station evaluates the real time source term to assess radiation impact.« less

Comparative analysis of radioecological monitoring dosimeters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sobolev, A.I.; Pol`skii, O.G.; Shanin, O.B.

1995-03-01

This paper describes comparative estimates of radiation doses measured by two types of thermoluminescence dosimeters and two types of background radiation radiometers. The dosimetry systems were tested by simultaneously recording background radiation and standard radiation sources at a radioactive waste storage facility. Statistical analysis of the measurement results is summarized. The maximum recorded exposure dose rate for the experiment was 19 microrads per hour. The DTK-2 dosimeter overestimated dose rates by 6 to 43% and the DTU-2 dosimeter underestimated dose rates by 7 to 21%. Both devices are recommended for radioecological monitoring in populated areas. 4 refs., 3 figs., 5more » tabs.« less

Boosting subsurface life: is subseafloor sediment a natural catalyst for radiolytic hydrogen production?

NASA Astrophysics Data System (ADS)

Sauvage, J.; Graham, D.; Spivack, A. J.; Dunlea, A. G.; Murray, R. W.; D'Hondt, S.

2014-12-01

Naturally occurring production of molecular hydrogen (H2) by water radiolysis may be a fundamentally important source of electron donors (energy) for life in subsurface environments where organic matter is scarce. Previous studies with very high gamma radiation rates and wet mineral phases have reported high H2 production relative to production from water radiolysis in the absence of solid phases. Numerical calculations by other previous studies have predicted enhanced H2 production from seawater radiolysis relative to pure water radiolysis, due to the interaction of anions with hydroxyl radicals. Given these reports, the potential catalytic influences of solid and dissolved chemical phases on radiolytic H2 production need to be carefully quantified in order to fully evaluate the role of radiolytic H2 as a microbial energy source. For such quantification, we undertook gamma-irradiation experiments with pure water, deep ocean water and mixtures (slurries, φ = 0.85) of seawater with: North Pacific abyssal clay and calcareous oozes, coastal sediment, zirconium dioxide, and zeolite. We carried out our experiments at the Rhode Island Nuclear Science Center using a 37Cesium source at low dose rates (up to 0.1 Gy/hr). Our results to date include the following. First, the per-dose radiolytic H2 yield of pure water at low dose rates is directly comparable to the per-dose yield at much higher dose rates (ca. 1 kGy/hr); this result indicates that H2 production rate is linearly related to radiation dose rate across four orders of magnitude. Second, there is no statistically significant difference (90% confidence limit) between the radiolytic H2 yield from pure water and that from seawater; this result rules out influence of abundant seawater salts on H2 yield from water radiolysis. Third, H2 production from a mixture of abyssal clay and seawater is 25% higher than the yield from pure water. This enhanced yield is consistent with catalysis of radiolytic H2 production by zeolite.

Application of the MCNP5 code to the Modeling of vaginal and intra-uterine applicators used in intracavitary brachytherapy: a first approach

NASA Astrophysics Data System (ADS)

Gerardy, I.; Rodenas, J.; Van Dycke, M.; Gallardo, S.; Tondeur, F.

2008-02-01

Brachytherapy is a radiotherapy treatment where encapsulated radioactive sources are introduced within a patient. Depending on the technique used, such sources can produce high, medium or low local dose rates. The Monte Carlo method is a powerful tool to simulate sources and devices in order to help physicists in treatment planning. In multiple types of gynaecological cancer, intracavitary brachytherapy (HDR Ir-192 source) is used combined with other therapy treatment to give an additional local dose to the tumour. Different types of applicators are used in order to increase the dose imparted to the tumour and to limit the effect on healthy surrounding tissues. The aim of this work is to model both applicator and HDR source in order to evaluate the dose at a reference point as well as the effect of the materials constituting the applicators on the near field dose. The MCNP5 code based on the Monte Carlo method has been used for the simulation. Dose calculations have been performed with *F8 energy deposition tally, taking into account photons and electrons. Results from simulation have been compared with experimental in-phantom dose measurements. Differences between calculations and measurements are lower than 5%.The importance of the source position has been underlined.

Skyshine radiation from a pressurized water reactor containment dome

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, W.H.

1986-06-01

The radiation dose rates resulting from airborne activities inside a postaccident pressurized water reactor containment are calculated by a discrete ordinates/Monte Carlo combined method. The calculated total dose rates and the skyshine component are presented as a function of distance from the containment at three different elevations for various gamma-ray source energies. The one-dimensional (ANISN code) is used to approximate the skyshine dose rates from the hemisphere dome, and the results are compared favorably to more rigorous results calculated by a three-dimensional Monte Carlo code.

High dose rate 192Ir source calibration: A single institution experience

NASA Astrophysics Data System (ADS)

Abdullah, R.; Abdullah, N. H.; Mohamed, M.; Idris, N. R. N.; Yusoff, A. L.; Chen, S. C.; Zakaria, A.

2017-05-01

Measurement of source strength of new high dose rate (HDR) 192Ir supplied by the manufacturer is part of quality assurance recommended by Radiation Safety Section, Ministry of Health of Malaysia. The source strength is determined in reference air kerma rate (RAKR). The purpose of this study was to evaluate RAKR measurement of 192Ir using well-type ionisation chamber with RAKR stated in the certificate provided by the manufacturer. A retrospective study on 19 MicroSelectron HDR 192Ir Classic from 2001 to 2009 and 12 MicroSelectron HDR 192Ir V2 sources from 2009 to 2016 supplied by manufacturer were compared. From the study, the agreement between measured RAKR and RAKR stated in the certificate by manufacturer for all 32 sources supplied were within ±2.5%. As a conclusion, a threshold level of ±2.5% can be used as suitable indicator to spot problems of the brachytherapy system in Department of Nuclear Medicine Radiotherapy and Oncology, Hospital USM.

Measurements of air dose rates in and around houses in the Fukushima Prefecture in Japan after the Fukushima accident.

PubMed

Matsuda, Norihiro; Mikami, Satoshi; Sato, Tetsuro; Saito, Kimiaki

2017-01-01

Measurements of air dose rates for 192 houses in a less contaminated area (<0.5 μSv h -1 ) of the Fukushima Prefecture in Japan were conducted in both living rooms and/or bedrooms using optically stimulated luminescence (OSL) dosimeters and around the houses via a man-borne survey at intervals of several meters. The relation of the two air dose rates (inside and outside) for each house, including the background from natural radionuclides, was divided into several categories, determined by construction materials (light and heavy) and floor number, with the dose reduction factors being expressed as the ratio of the dose inside to that outside the house. For wooden and lightweight steel houses (classed as light), the dose rates inside and outside the houses showed a positive correlation and linear regression with a slope-intercept form due to the natural background, although the degree of correlation was not very high. The regression coefficient, i.e., the average dose reduction factor, was 0.38 on the first floor and 0.49 on the second floor. It was found that the contribution of natural radiation cannot be neglected when we consider dose reduction factors in less contaminated areas. The reductions in indoor dose rates are observed because a patch of ground under each house is not contaminated (this is the so-called uncontaminated effect) since the shielding capability of light construction materials is typically low. For reinforced steel-framed concrete houses (classed as heavy), the dose rates inside the houses did not show a correlation with those outside the houses due to the substantial shielding capability of these materials. The average indoor dose rates were slightly higher than the arithmetic mean value of the outdoor dose rates from the natural background because concrete acts as a source of natural radionuclides. The characteristics of the uncontaminated effect were clarified through Monte Carlo simulations. It was found that there is a great variation in air dose rates even within one house, depending on the height of the area and its closeness to the outside boundary. Measurements of outdoor dose rates required consideration of local variations depending on the environment surrounding each house. The representative value was obtained from detailed distributions of air dose rates around the house, as measured by a man-borne survey. Therefore, it is imperative to recognize that dose reduction factors fluctuate in response to various factors such as the size and shape of a house, construction materials acting as a shield and as sources, position (including height) within a room, floor number, total number of floors, and surrounding environment. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

Testing Moderating Detection Systems with {sup 252}Cf-Based Reference Neutron Fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hertel, Nolan E.; Sweezy, Jeremy; Sauber, Jeremiah S.

Calibration measurements were carried out on a probe designed to measure ambient dose equivalent in accordance with ICRP Pub 60 recommendations. It consists of a cylindrical {sup 3}He proportional counter surrounded by a 25-cm-diameter spherical polyethylene moderator. Its neutron response is optimized for dose rate measurements of neutrons between thermal energies and 20 MeV. The instrument was used to measure the dose rate in four separate neutron fields: unmoderated {sup 252}Cf, D{sub 2}O-moderated {sup 252}Cf, polyethylene-moderated {sup 252}Cf, and WEP neutron howitzer with {sup 252}Cf at its center. Dose equivalent measurements were performed at source-detector centerline distances from 50 tomore » 200 cm. The ratio of air-scatter- and room-return-corrected ambient dose equivalent rates to ambient dose equivalent rates calculated with the code MCNP are tabulated.« less

Calculated and measured brachytherapy dosimetry parameters in water for the Xoft Axxent X-Ray Source: an electronic brachytherapy source.

PubMed

Rivard, Mark J; Davis, Stephen D; DeWerd, Larry A; Rusch, Thomas W; Axelrod, Steve

2006-11-01

A new x-ray source, the model S700 Axxent X-Ray Source (Source), has been developed by Xoft Inc. for electronic brachytherapy. Unlike brachytherapy sources containing radionuclides, this Source may be turned on and off at will and may be operated at variable currents and voltages to change the dose rate and penetration properties. The in-water dosimetry parameters for this electronic brachytherapy source have been determined from measurements and calculations at 40, 45, and 50 kV settings. Monte Carlo simulations of radiation transport utilized the MCNP5 code and the EPDL97-based mcplib04 cross-section library. Inter-tube consistency was assessed for 20 different Sources, measured with a PTW 34013 ionization chamber. As the Source is intended to be used for a maximum of ten treatment fractions, tube stability was also assessed. Photon spectra were measured using a high-purity germanium (HPGe) detector, and calculated using MCNP. Parameters used in the two-dimensional (2D) brachytherapy dosimetry formalism were determined. While the Source was characterized as a point due to the small anode size, < 1 mm, use of the one-dimensional (1D) brachytherapy dosimetry formalism is not recommended due to polar anisotropy. Consequently, 1D brachytherapy dosimetry parameters were not sought. Calculated point-source model radial dose functions at gP(5) were 0.20, 0.24, and 0.29 for the 40, 45, and 50 kV voltage settings, respectively. For 1

Investigation of natural effective gamma dose rates case study: Ardebil Province in Iran

PubMed Central

2012-01-01

Gamma rays pose enough energy to induce chemical changes that may be biologically important for the normal functioning of body cells. The external exposure of human beings to natural environmental gamma radiation normally exceeds that from all man-made sources combined. In this research natural background gamma dose rates and corresponding annual effective doses were determined for selected cities of Ardebil province. Outdoor gamma dose rates were measured using an Ion Chamber Survey Meter in 105 locations in selected districts. Average absorbed doses for Ardebil, Sar-Ein, Germy, Neer, Shourabil Recreational Lake, and Kosar were determined as 265, 219, 344, 233, 352, and 358 nSv/h, respectively. Although dose rates recorded for Germi and Kosar are comparable with some areas with high natural radiation background, however, the dose rates in other districts are well below the levels reported for such locations. Average annual effective dose due to indoor and outdoor gamma radiation for Ardebil province was estimated as 1.73 (1.35–2.39) mSv, which is on average 2 times higher than the world population weighted average. PMID:23369115

Higher dose rate Gamma Knife radiosurgery may provide earlier and longer-lasting pain relief for patients with trigeminal neuralgia.

PubMed

Lee, John Y K; Sandhu, Sukhmeet; Miller, Denise; Solberg, Timothy; Dorsey, Jay F; Alonso-Basanta, Michelle

2015-10-01

Gamma Knife radiosurgery (GKRS) utilizes cobalt-60 as its radiation source, and thus dose rate varies as the fixed source decays over its half-life of approximately 5.26 years. This natural decay results in increasing treatment times when delivering the same cumulative dose. It is also possible, however, that the biological effective dose may change based on this dose rate even if the total dose is kept constant. Because patients are generally treated in a uniform manner, radiosurgery for trigeminal neuralgia (TN) represents a clinical model whereby biological efficacy can be tested. The authors hypothesized that higher dose rates would result in earlier and more complete pain relief but only if measured with a sensitive pain assessment tool. One hundred thirty-three patients were treated with the Gamma Knife Model 4C unit at a single center by a single neurosurgeon during a single cobalt life cycle from January 2006 to May 2012. All patients were treated with 80 Gy with a single 4-mm isocenter without blocking. Using an output factor of 0.87, dose rates ranged from 1.28 to 2.95 Gy/min. The Brief Pain Inventory (BPI)-Facial was administered before the procedure and at the first follow-up office visit 1 month from the procedure (mean 1.3 months). Phone calls were made to evaluate patients after their procedures as part of a retrospective study. Univariate and multivariate linear regression was performed on several independent variables, including sex, age in deciles, diagnosis, follow-up duration, prior surgery, and dose rate. In the short-term analysis (mean 1.3 months), patients' self-reported pain intensity at its worst was significantly correlated with dose rate on multivariate analysis (p = 0.028). Similarly, patients' self-reported interference with activities of daily living was closely correlated with dose rate on multivariate analysis (p = 0.067). A 1 Gy/min decrease in dose rate resulted in a 17% decrease in pain intensity at its worst and a 22% decrease in pain interference with activities of daily living. In longer-term follow-up (mean 1.9 years), GKRS with higher dose rates (> 2.0 Gy/min; p = 0.007) and older age in deciles (p = 0.012) were associated with a lower likelihood of recurrence of pain. Prior studies investigating the role of dose rate in Gamma Knife radiosurgical ablation for TN have not used validated outcome tools to measure pain preoperatively. Consequently, differences in pain outcomes have been difficult to measure. By administering pain scales both preoperatively as well as postoperatively, the authors have identified statistically significant differences in pain intensity and pain interference with activities of daily living when comparing higher versus lower dose rates. Radiosurgery with a higher dose rate results in more pain relief at the early follow-up evaluation, and it may result in a lower recurrence rate at later follow-up.

Effect of photon energy spectrum on dosimetric parameters of brachytherapy sources.

PubMed

Ghorbani, Mahdi; Mehrpouyan, Mohammad; Davenport, David; Ahmadi Moghaddas, Toktam

2016-06-01

The aim of this study is to quantify the influence of the photon energy spectrum of brachytherapy sources on task group No. 43 (TG-43) dosimetric parameters. Different photon spectra are used for a specific radionuclide in Monte Carlo simulations of brachytherapy sources. MCNPX code was used to simulate 125I, 103Pd, 169Yb, and 192Ir brachytherapy sources. Air kerma strength per activity, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated and isodose curves were plotted for three different photon energy spectra. The references for photon energy spectra were: published papers, Lawrence Berkeley National Laboratory (LBNL), and National Nuclear Data Center (NNDC). The data calculated by these photon energy spectra were compared. Dose rate constant values showed a maximum difference of 24.07% for 103Pd source with different photon energy spectra. Radial dose function values based on different spectra were relatively the same. 2D anisotropy function values showed minor differences in most of distances and angles. There was not any detectable difference between the isodose contours. Dosimetric parameters obtained with different photon spectra were relatively the same, however it is suggested that more accurate and updated photon energy spectra be used in Monte Carlo simulations. This would allow for calculation of reliable dosimetric data for source modeling and calculation in brachytherapy treatment planning systems.

Effect of photon energy spectrum on dosimetric parameters of brachytherapy sources

PubMed Central

Ghorbani, Mahdi; Davenport, David

2016-01-01

Abstract Aim The aim of this study is to quantify the influence of the photon energy spectrum of brachytherapy sources on task group No. 43 (TG-43) dosimetric parameters. Background Different photon spectra are used for a specific radionuclide in Monte Carlo simulations of brachytherapy sources. Materials and methods MCNPX code was used to simulate 125I, 103Pd, 169Yb, and 192Ir brachytherapy sources. Air kerma strength per activity, dose rate constant, radial dose function, and two dimensional (2D) anisotropy functions were calculated and isodose curves were plotted for three different photon energy spectra. The references for photon energy spectra were: published papers, Lawrence Berkeley National Laboratory (LBNL), and National Nuclear Data Center (NNDC). The data calculated by these photon energy spectra were compared. Results Dose rate constant values showed a maximum difference of 24.07% for 103Pd source with different photon energy spectra. Radial dose function values based on different spectra were relatively the same. 2D anisotropy function values showed minor differences in most of distances and angles. There was not any detectable difference between the isodose contours. Conclusions Dosimetric parameters obtained with different photon spectra were relatively the same, however it is suggested that more accurate and updated photon energy spectra be used in Monte Carlo simulations. This would allow for calculation of reliable dosimetric data for source modeling and calculation in brachytherapy treatment planning systems. PMID:27247558

SU-F-T-33: Air-Kerma Strength and Dose Rate Constant by the Full Monte Carlo Simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsuji, S; Oita, M; Narihiro, N

2016-06-15

Purpose: In general, the air-kerma strength (Sk) has been determined by the energy weighting the photon energy fluence and the corresponding mass-energy absorption coefficient or mass-energy transfer coefficient. Kerma is an acronym for kinetic energy released per unit mass, defined as the sum of the initial kinetic energies of all the charged particles. Monte Carlo (MC) simulations can investigate the kinetic energy of the charged particles after photo interactions and sum the energy. The Sk of {sup 192}Ir source is obtained in the full MC simulation and finally the dose rate constant Λ is determine. Methods: MC simulations were performedmore » using EGS5 with the microSelectron HDR v2 type of {sup 192}Ir source. The air-kerma rate obtained to sum the electron kinetic energy after photoelectric absorption or Compton scattering for transverse-axis distance from 1 to 120 cm with a 10 m diameter air phantom. Absorbed dose in water is simulated with a 30 cm diameter water phantom. The transport cut-off energy is 10 keV and primary photons from the source need two hundred and forty billion in the air-kerma rate and thirty billion in absorbed dose in water. Results: Sk is multiplied by the square of the distance in air-kerma rate and determined by fitting a linear function. The result of Sk is (2.7039±0.0085)*10-{sup −11} µGy m{sup 2} Bq{sup −1} s{sup −1}. Absorbed dose rate in water at 1 cm transverse-axis distance D(r{sub 0}, θ{sub 0}) is (3.0114±0.0015)*10{sup −11} cGy Bq{sup −1} s{sup −1}. Conclusion: From the results, dose rate constant Λ of the microSelectron HDR v2 type of {sup 192}Ir source is (1.1137±0.0035) cGy h{sup −1} U{sup −1} by the full MC simulations. The consensus value conΛ is (1.109±0.012) cGy h{sup −1} U{sup −1}. The result value is consistent with the consensus data conΛ.« less

SU-F-T-670: From the OR to the Radiobiology Lab: The Journey of a Small X-Ray Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lehmann, J; The University of Sydney, Sydney, NSW; The University of Newcastle, Newcastle, NSW

Purpose: Irradiation of small animal tumor models within laboratories is vital to radiobiological experiments. Often the animals are not able to be brought back into the lab after being taken out for irradiation. Cell biology laboratories benefit from irradiation capability available around the clock without regard to patient load in an associated radiotherapy clinic. Commercial systems are available, but bulky and expensive. Methods: An intraoperative kV irradiation system (IntraBeam™) designed to deliver spherical dose distributions to surgical cavities has been repurposed for the irradiation of cell plates and small laboratory animals. An applicator has been altered to allow for simple,more » open fields. Special collimators are being developed. BEAMnrc Monte Carlo simulations with the “NRC swept BEAM” source model have been performed to characterize the dose distributions, to develop optimal collimators and as basis for dose prescription. Measurements with radiochromic film and with an ionization chamber were performed to characterize the beam and to validate the simulations. Results: Using its highest setting (50 kV and 40 µA) the x-ray unit is capable of delivering dose rates over 1 Gy/min homogeneously to standard cell plates even without an optimized collimator. Smaller areas (tumors in animals) can be irradiated with significantly higher dose rates (> 20 Gy/min) depending on distance of the source to the tumor. The HVL was found to be 0.21 mm Al which means the shielding requirements for the device are easily achievable in the lab. Conclusion: A mobile irradiation facility is feasible. It will allow easier access to radiation for radiobiology experiments. The modified system is versatile in that for cell plates homogenous irradiations can be achieved through distance from the source, while for high dose rate small field irradiations the source can be brought in close proximity to the target.« less

Radiological Source Terms for Tank Farms Safety Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

COWLEY, W.L.

2000-06-27

This document provides Unit Liter Dose factors, atmospheric dispersion coefficients, breathing rates and instructions for using and customizing these factors for use in calculating radiological doses for accident analyses in the Hanford Tank Farms.

Comparison of organ doses for patients undergoing balloon brachytherapy of the breast with HDR 192Ir or electronic sources using Monte Carlo simulations in a heterogeneous human phantom1

PubMed Central

Mille, Matthew M.; Xu, X. George; Rivard, Mark J.

2010-01-01

Purpose: Accelerated partial breast irradiation via interstitial balloon brachytherapy is a fast and effective treatment method for certain early stage breast cancers. The radiation can be delivered using a conventional high-dose rate (HDR) 192Ir gamma-emitting source or a novel electronic brachytherapy (eBx) source which uses lower energy x rays that do not penetrate as far within the patient. A previous study [A. Dickler, M. C. Kirk, N. Seif, K. Griem, K. Dowlatshahi, D. Francescatti, and R. A. Abrams, “A dosimetric comparison of MammoSite high-dose-rate brachytherapy and Xoft Axxent electronic brachytherapy,” Brachytherapy 6, 164–168 (2007)] showed that the target dose is similar for HDR 192Ir and eBx. This study compares these sources based on the dose received by healthy organs and tissues away from the treatment site. Methods: A virtual patient with left breast cancer was represented by a whole-body, tissue-heterogeneous female voxel phantom. Monte Carlo methods were used to calculate the dose to healthy organs in a virtual patient undergoing balloon brachytherapy of the left breast with HDR 192Ir or eBx sources. The dose-volume histograms for a few organs which received large doses were also calculated. Additional simulations were performed with all tissues in the phantom defined as water to study the effect of tissue inhomogeneities. Results: For both HDR 192Ir and eBx, the largest mean organ doses were received by the ribs, thymus gland, left lung, heart, and sternum which were close to the brachytherapy source in the left breast. eBx yielded mean healthy organ doses that were more than a factor of ∼1.4 smaller than for HDR 192Ir for all organs considered, except for the three closest ribs. Excluding these ribs, the average and median dose-reduction factors were ∼28 and ∼11, respectively. The volume distribution of doses in nearby soft tissue organs that were outside the PTV were also improved with eBx. However, the maximum dose to the closest rib with the eBx source was 5.4 times greater than that of the HDR 192Ir source. The ratio of tissue-to-water maximum rib dose for the eBx source was ∼5. Conclusions: The results of this study indicate that eBx may offer lower toxicity to most healthy tissues, except nearby bone. TG-43 methods have a tendency to underestimate dose to bone, especially the ribs. Clinical studies evaluating the negative health effects caused by irradiating healthy organs are needed so that physicians can better understand when HDR 192Ir or eBx might best benefit a patient. PMID:20229875

Absorbed dose calculations in a brachytherapy pelvic phantom using the Monte Carlo method

PubMed Central

Rodríguez, Miguel L.; deAlmeida, Carlos E.

2002-01-01

Monte Carlo calculations of the absorbed dose at various points of a brachytherapy anthropomorphic phantom are presented. The phantom walls and internal structures are made of polymethylmethacrylate and its external shape was taken from a female Alderson phantom. A complete Fletcher‐Green type applicator with the uterine tandem was fixed at the bottom of the phantom reproducing a typical geometrical configuration as that attained in a gynecological brachytherapy treatment. The dose rate produced by an array of five 137Cs CDC‐J type sources placed in the applicator colpostats and the uterine tandem was evaluated by Monte Carlo simulations using the code penelope at three points: point A, the rectum, and the bladder. The influence of the applicator in the dose rate was evaluated by comparing Monte Carlo simulations of the sources alone and the sources inserted in the applicator. Differences up to 56% in the dose may be observed for the two cases in the planes including the rectum and bladder. The results show a reduction of the dose of 15.6%, 14.0%, and 5.6% in the rectum, bladder, and point A respectively, when the applicator wall and shieldings are considered. PACS number(s): 87.53Jw, 87.53.Wz, 87.53.Vb, 87.66.Xa PMID:12383048

Interstitial rotating shield brachytherapy for prostate cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adams, Quentin E., E-mail: quentin-adams@uiowa.edu; Xu, Jinghzu; Breitbach, Elizabeth K.

Purpose: To present a novel needle, catheter, and radiation source system for interstitial rotating shield brachytherapy (I-RSBT) of the prostate. I-RSBT is a promising technique for reducing urethra, rectum, and bladder dose relative to conventional interstitial high-dose-rate brachytherapy (HDR-BT). Methods: A wire-mounted 62 GBq{sup 153}Gd source is proposed with an encapsulated diameter of 0.59 mm, active diameter of 0.44 mm, and active length of 10 mm. A concept model I-RSBT needle/catheter pair was constructed using concentric 50 and 75 μm thick nickel-titanium alloy (nitinol) tubes. The needle is 16-gauge (1.651 mm) in outer diameter and the catheter contains a 535more » μm thick platinum shield. I-RSBT and conventional HDR-BT treatment plans for a prostate cancer patient were generated based on Monte Carlo dose calculations. In order to minimize urethral dose, urethral dose gradient volumes within 0–5 mm of the urethra surface were allowed to receive doses less than the prescribed dose of 100%. Results: The platinum shield reduced the dose rate on the shielded side of the source at 1 cm off-axis to 6.4% of the dose rate on the unshielded side. For the case considered, for the same minimum dose to the hottest 98% of the clinical target volume (D{sub 98%}), I-RSBT reduced urethral D{sub 0.1cc} below that of conventional HDR-BT by 29%, 33%, 38%, and 44% for urethral dose gradient volumes within 0, 1, 3, and 5 mm of the urethra surface, respectively. Percentages are expressed relative to the prescription dose of 100%. For the case considered, for the same urethral dose gradient volumes, rectum D{sub 1cc} was reduced by 7%, 6%, 6%, and 6%, respectively, and bladder D{sub 1cc} was reduced by 4%, 5%, 5%, and 6%, respectively. Treatment time to deliver 20 Gy with I-RSBT was 154 min with ten 62 GBq {sup 153}Gd sources. Conclusions: For the case considered, the proposed{sup 153}Gd-based I-RSBT system has the potential to lower the urethral dose relative to HDR-BT by 29%–44% if the clinician allows a urethral dose gradient volume of 0–5 mm around the urethra to receive a dose below the prescription. A multisource approach is necessary in order to deliver the proposed {sup 153}Gd-based I-RSBT technique in reasonable treatment times.« less

Radiation protocols determine acute graft-versus-host disease incidence after allogeneic bone marrow transplantation in murine models.

PubMed

Schwarte, Sebastian; Bremer, Michael; Fruehauf, Joerg; Sorge, Yanina; Skubich, Susanne; Hoffmann, Matthias W

2007-09-01

Effects of radiation sources used for total body irradiation (TBI) on Graft-versus-Host Disease (GvHD) induction were examined. In a T cell receptor (TCR) transgenic mouse model, single fraction TBI was performed with different radiation devices ((60)Cobalt; (137)Cesium; 6 MV linear accelerator), dose rates (0.85; 1.5; 2.9; 5 Gy/min) and total doses before allogeneic bone marrow transplantation (BMT). Recipients were observed for 120 days. Different tissues were examined histologically. Acute GvHD was induced by a dose rate of 0.85 Gy/min ((60)Cobalt) and a total dose of 9 Gy and injection of 5 x 10(5) lymph node cells plus 5 x 10(6) bone marrow cells. Similar results were obtained using 6 MV linear accelerator- (linac-) photons with a dose rate of 1.5 Gy/min and 0.85 Gy/min, a total dose of 9.5 Gy and injection of same cell numbers. TBI with (137)Cesium (dose rate: 2.5 Gy/min) did not lead reproducibly to lethal acute GvHD. Experimental TBI in murine models may induce different immunological responses, depending on total energy, total single dose and dose rate. GvHD might also be induced by TBI with low dose rates.

Effect of Ion Flux (Dose Rate) in Source-Drain Extension Ion Implantation for 10-nm Node FinFET and Beyond on 300/450mm Platforms

NASA Astrophysics Data System (ADS)

Shen, Ming-Yi

The improvement of wafer equipment productivity has been a continuous effort of the semiconductor industry. Higher productivity implies lower product price, which economically drives more demand from the market. This is desired by the semiconductor manufacturing industry. By raising the ion beam current of the ion implanter for 300/450mm platforms, it is possible to increase the throughput of the ion implanter. The resulting dose rate can be comparable to the performance of conventional ion implanters or higher, depending on beam current and beam size. Thus, effects caused by higher dose rate must be investigated further. One of the major applications of ion implantation (I/I) is source-drain extension (SDE) I/I for the silicon FinFET device. This study investigated the dose rate effects on the material properties and device performance of the 10-nm node silicon FinFET. In order to gain better understanding of the dose rate effects, the dose rate study is based on Synopsys Technology CAD (TCAD) process and device simulations that are calibrated and validated using available structural silicon fin samples. We have successfully shown that the kinetic monte carlo (KMC) I/I simulation can precisely model both the silicon amorphization and the arsenic distribution in the fin by comparing the KMC simulation results with TEM images. The results of the KMC I/I simulation show that at high dose rate more activated arsenic dopants were in the source-drain extension (SDE) region. This finding matches with the increased silicon amorphization caused by the high dose-rate I/I, given that the arsenic atoms could be more easily activated by the solid phase epitaxial regrowth process. This increased silicon amorphization led to not only higher arsenic activation near the spacer edge, but also less arsenic atoms straggling into the channel. Hence, it is possible to improve the throughput of the ion implanter when the dopants are implanted at high dose rate if the same doping level with a lower wafer dose can be achieved. In addition, the leakage current might also be reduced due to less undesired dopants in the channel. However, the twin defects from the problematic Si{111} recrystallization is well-known to cause excessive leakage current to the FinFET. This drawback can offset the benefits of the high dose rate I/I mentioned above. This work produced the first attempt at simulating the electrical impact of twin defects on advanced-node (10 nm) FinFET device performance. It was found that the high dose-rate I/I causes more twin defects in the silicon fin, and the physical locations of these defects were close to the channel. The defects undesirably induced trap-assisted band-to-band tunneling near the drain, which increased the leakage current. This issue could be mitigated by using asymmetrical gate overlap/underlap design or thicker spacer for SDE I/I so that the twin defects are not located in the depletion region near the drain.

Space-Time Dependent Transport, Activation, and Dose Rates for Radioactivated Fluids.

NASA Astrophysics Data System (ADS)

Gavazza, Sergio

Two methods are developed to calculate the space - and time-dependent mass transport of radionuclides, their production and decay, and the associated dose rates generated from the radioactivated fluids flowing through pipes. The work couples space- and time-dependent phenomena, treated as only space- or time-dependent in the open literature. The transport and activation methodology (TAM) is used to numerically calculate space- and time-dependent transport and activation of radionuclides in fluids flowing through pipes exposed to radiation fields, and volumetric radioactive sources created by radionuclide motions. The computer program Radionuclide Activation and Transport in Pipe (RNATPA1) performs the numerical calculations required in TAM. The gamma ray dose methodology (GAM) is used to numerically calculate space- and time-dependent gamma ray dose equivalent rates from the volumetric radioactive sources determined by TAM. The computer program Gamma Ray Dose Equivalent Rate (GRDOSER) performs the numerical calculations required in GAM. The scope of conditions considered by TAM and GAM herein include (a) laminar flow in straight pipe, (b)recirculating flow schemes, (c) time-independent fluid velocity distributions, (d) space-dependent monoenergetic neutron flux distribution, (e) space- and time-dependent activation process of a single parent nuclide and transport and decay of a single daughter radionuclide, and (f) assessment of space- and time-dependent gamma ray dose rates, outside the pipe, generated by the space- and time-dependent source term distributions inside of it. The methodologies, however, can be easily extended to include all the situations of interest for solving the phenomena addressed in this dissertation. A comparison is made from results obtained by the described calculational procedures with analytical expressions. The physics of the problems addressed by the new technique and the increased accuracy versus non -space and time-dependent methods are presented. The value of the methods is also discussed. It has been demonstrated that TAM and GAM can be used to enhance the understanding of the space- and time-dependent mass transport of radionuclides, their production and decay, and the associated dose rates related to radioactivated fluids flowing through pipes.

Dosimetric Consistency of Co-60 Teletherapy Unit- a ten years Study.

PubMed

Baba, Misba H; Mohib-Ul-Haq, M; Khan, Aijaz A

2013-01-01

The goal of the Radiation standards and Dosimetry is to ensure that the output of the Teletherapy Unit is within ±2% of the stated one and the output of the treatment dose calculation methods are within ±5%. In the present paper, we studied the dosimetry of Cobalt-60 (Co-60) Teletherapy unit at Sher-I-Kashmir Institute of Medical Sciences (SKIMS) for last 10 years. Radioactivity is the phenomenon of disintegration of unstable nuclides called radionuclides. Among these radionuclides, Cobalt-60, incorporated in Telecobalt Unit, is commonly used in therapeutic treatment of cancer. Cobalt-60 being unstable decays continuously into Ni-60 with half life of 5.27 years thereby resulting in the decrease in its activity, hence dose rate (output). It is, therefore, mandatory to measure the dose rate of the Cobalt-60 source regularly so that the patient receives the same dose every time as prescribed by the radiation oncologist. The under dosage may lead to unsatisfactory treatment of cancer and over dosage may cause radiation hazards. Our study emphasizes the consistency between actual output and output obtained using decay method. The methodology involved in the present study is the calculations of actual dose rate of Co-60 Teletherapy Unit by two techniques i.e. Source to Surface Distance (SSD) and Source to Axis Distance (SAD), used for the External Beam Radiotherapy, of various cancers, using the standard methods. Thereby, a year wise comparison has been made between average actual dosimetric output (dose rate) and the average expected output values (obtained by using decay method for Co-60.). The present study shows that there is a consistency in the average output (dose rate) obtained by the actual dosimetry values and the expected output values obtained using decay method. The values obtained by actual dosimetry are within ±2% of the expected values. The results thus obtained in a year wise comparison of average output by actual dosimetry done regularly as a part of Quality Assurance of the Telecobalt Radiotherapy Unit and its deviation from the expected output data is within the permissible limits. Thus our study shows a trend towards uniformity and a better dose delivery.

TU-AB-201-08: Rotating Shield High Dose Rate Brachytherapy with 153Gd and 75Se Isotopes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Renaud, M; Seuntjens, J; Enger, S

Purpose: To introduce rotating shield brachytherapy (RSBT) for different cancer sites with {sup 153}Gd and {sup 75}Se isotopes. RSBT is a form of intensity modulated brachytherapy, using shielded rotating catheters to provide a better dose distribution in the tumour while protecting healthy tissue. Methods: BrachySource, a Geant4-based Monte Carlo dose planning system was developed for investigation of RSBT with {sup 153}Gd and {sup 75}Se for different cancer sites. Dose distributions from {sup 153}Gd, {sup 75}Se and {sup 192}Ir isotopes were calculated in a 40 cm radius water phantom by using the microSelectron-v2 source model. The source was placed inside amore » cylindrical platinum shield with 1.3 mm diameter. An emission window coinciding with the active core of the source was created by removing half (180°) of the wall of the shield. Relative dose rate distributions of the three isotopes were simulated. As a proof of concept, a breast cancer patient originally treated with Mammosite was re-simulated with unshielded {sup 192}Ir and shielded {sup 153}Gd. Results: The source with the lowest energy, {sup 153}Gd, decreased the dose on the shielded side by 91%, followed by {sup 75}Se and {sup 192}Ir with 36% and 16% reduction at 1 cm from the source. The breast cancer patient simulation showed the ability of shielded {sup 153}Gd to spare the chest wall by a 90% dose reduction when only one emission window angle is considered. In this case, fully covering the PTV would require more delivery angles and the chest wall dose reduction would be less, however, the simulation demonstrates the potential of shielded {sup 153}Gd to selectively isolate organs at risk. Conclusion: Introducing {sup 153}Gd and {sup 75}Se sources combined with RSBT will allow escalation of dose in the target volume while maintaining low doses in radiation sensitive healthy tissue. Tailoring treatments to each individual patient by treating all parts of the tumour without over-irradiation of normal tissues will be possible. The author acknowledges partial support by the CREATE Medical Physics Research Training Network grant of the Natural Sciences and Engineering Research Council (Grant number: 432290), and the Quebec Fonds de recherche Nature et Technologies.« less

Role of step size and max dwell time in anatomy based inverse optimization for prostate implants

PubMed Central

Manikandan, Arjunan; Sarkar, Biplab; Rajendran, Vivek Thirupathur; King, Paul R.; Sresty, N.V. Madhusudhana; Holla, Ragavendra; Kotur, Sachin; Nadendla, Sujatha

2013-01-01

In high dose rate (HDR) brachytherapy, the source dwell times and dwell positions are vital parameters in achieving a desirable implant dose distribution. Inverse treatment planning requires an optimal choice of these parameters to achieve the desired target coverage with the lowest achievable dose to the organs at risk (OAR). This study was designed to evaluate the optimum source step size and maximum source dwell time for prostate brachytherapy implants using an Ir-192 source. In total, one hundred inverse treatment plans were generated for the four patients included in this study. Twenty-five treatment plans were created for each patient by varying the step size and maximum source dwell time during anatomy-based, inverse-planned optimization. Other relevant treatment planning parameters were kept constant, including the dose constraints and source dwell positions. Each plan was evaluated for target coverage, urethral and rectal dose sparing, treatment time, relative target dose homogeneity, and nonuniformity ratio. The plans with 0.5 cm step size were seen to have clinically acceptable tumor coverage, minimal normal structure doses, and minimum treatment time as compared with the other step sizes. The target coverage for this step size is 87% of the prescription dose, while the urethral and maximum rectal doses were 107.3 and 68.7%, respectively. No appreciable difference in plan quality was observed with variation in maximum source dwell time. The step size plays a significant role in plan optimization for prostate implants. Our study supports use of a 0.5 cm step size for prostate implants. PMID:24049323

Study of dose calculation on breast brachytherapy using prism TPS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fendriani, Yoza; Haryanto, Freddy

2015-09-30

PRISM is one of non-commercial Treatment Planning System (TPS) and is developed at the University of Washington. In Indonesia, many cancer hospitals use expensive commercial TPS. This study aims to investigate Prism TPS which been applied to the dose distribution of brachytherapy by taking into account the effect of source position and inhomogeneities. The results will be applicable for clinical Treatment Planning System. Dose calculation has been implemented for water phantom and CT scan images of breast cancer using point source and line source. This study used point source and line source and divided into two cases. On the firstmore » case, Ir-192 seed source is located at the center of treatment volume. On the second case, the source position is gradually changed. The dose calculation of every case performed on a homogeneous and inhomogeneous phantom with dimension 20 × 20 × 20 cm{sup 3}. The inhomogeneous phantom has inhomogeneities volume 2 × 2 × 2 cm{sup 3}. The results of dose calculations using PRISM TPS were compared to literature data. From the calculation of PRISM TPS, dose rates show good agreement with Plato TPS and other study as published by Ramdhani. No deviations greater than ±4% for all case. Dose calculation in inhomogeneous and homogenous cases show similar result. This results indicate that Prism TPS is good in dose calculation of brachytherapy but not sensitive for inhomogeneities. Thus, the dose calculation parameters developed in this study were found to be applicable for clinical treatment planning of brachytherapy.« less

Development and implementation of a remote audit tool for high dose rate (HDR) Ir-192 brachytherapy using optically stimulated luminescence dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Casey, Kevin E.; Kry, Stephen F.; Howell, Rebecca M.

Purpose: The aim of this work was to create a mailable phantom with measurement accuracy suitable for Radiological Physics Center (RPC) audits of high dose-rate (HDR) brachytherapy sources at institutions participating in National Cancer Institute-funded cooperative clinical trials. Optically stimulated luminescence dosimeters (OSLDs) were chosen as the dosimeter to be used with the phantom.Methods: The authors designed and built an 8 × 8 × 10 cm{sup 3} prototype phantom that had two slots capable of holding Al{sub 2}O{sub 3}:C OSLDs (nanoDots; Landauer, Glenwood, IL) and a single channel capable of accepting all {sup 192}Ir HDR brachytherapy sources in current clinicalmore » use in the United States. The authors irradiated the phantom with Nucletron and Varian {sup 192}Ir HDR sources in order to determine correction factors for linearity with dose and the combined effects of irradiation energy and phantom characteristics. The phantom was then sent to eight institutions which volunteered to perform trial remote audits.Results: The linearity correction factor was k{sub L}= (−9.43 × 10{sup −5}× dose) + 1.009, where dose is in cGy, which differed from that determined by the RPC for the same batch of dosimeters using {sup 60}Co irradiation. Separate block correction factors were determined for current versions of both Nucletron and Varian {sup 192}Ir HDR sources and these vendor-specific correction factors differed by almost 2.6%. For the Nucletron source, the correction factor was 1.026 [95% confidence interval (CI) = 1.023–1.028], and for the Varian source, it was 1.000 (95% CI = 0.995–1.005). Variations in lateral source positioning up to 0.8 mm and distal/proximal source positioning up to 10 mm had minimal effect on dose measurement accuracy. The overall dose measurement uncertainty of the system was estimated to be 2.4% and 2.5% for the Nucletron and Varian sources, respectively (95% CI). This uncertainty was sufficient to establish a ±5% acceptance criterion for source strength audits under a formal RPC audit program. Trial audits of four Nucletron sources and four Varian sources revealed an average RPC-to-institution dose ratio of 1.000 (standard deviation = 0.011).Conclusions: The authors have created an OSLD-based {sup 192}Ir HDR brachytherapy source remote audit tool which offers sufficient dose measurement accuracy to allow the RPC to establish a remote audit program with a ±5% acceptance criterion. The feasibility of the system has been demonstrated with eight trial audits to date.« less

SU-G-201-10: Experimental Determination of Modified TG-43 Dosimetry Parameters for the Xoft Axxent® Electronic Brachytherapy Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Simiele, S; Palmer, B; DeWerd, L

Purpose: The establishment of an air kerma rate standard at NIST for the Xoft Axxent{sup ®} electronic brachytherapy source (Axxent{sup ®} source) motivated the establishment of a modified TG-43 dosimetry formalism. This work measures the modified dosimetry parameters for the Axxent{sup ®} source in the absence of a treatment applicator for implementation in Xoft’s treatment planning system. Methods: The dose-rate conversion coefficient (DRCC), radial dose function (RDF) values, and polar anisotropy (PA) were measured using TLD-100 microcubes with NIST-calibrated sources. The DRCC and RDF measurements were performed in liquid water using an annulus of Virtual Water™ designed to align themore » TLDs at the height of the anode at fixed radii from the source. The PA was measured at several distances from the source in a PMMA phantom. MCNP-determined absorbed dose energy dependence correction factors were used to convert from dose to TLD to dose to liquid water for the DRCC, RDF, and PA measurements. The intrinsic energy dependence correction factor from the work of Pike was used. The AKR was determined using a NIST-calibrated HDR1000 Plus well-type ionization chamber. Results: The DRCC was determined to be 8.6 (cGy/hr)/(µGy/min). The radial dose values were determined to be 1.00 (1cm), 0.60 (2cm), 0.42 (3cm), and 0.32 (4cm), with agreement ranging from (5.7% to 10.9%) from the work of Hiatt et al. 2015 and agreement from (2.8% to 6.8%) with internal MCNP simulations. Conclusion: This work presents a complete dataset of modified TG-43 dosimetry parameters for the Axxent{sup ®} source in the absence of an applicator. Prior to this study a DRCC had not been measured for the Axxent{sup ®} source. This data will be used for calculating dose distributions for patients receiving treatment with the Axxent{sup ®} source in Xoft’s breast balloon and vaginal applicators, and for intraoperative radiotherapy. Sources and partial funding for this work were provided by Xoft Inc. (a subsidiary of iCAD). This work was also supported by the Radiological Sciences T32 Training Grant through the University of Wisconsin-Madison Medical Physics department (5T32CA009206-37).« less

Setup and Calibration of SLAC's Peripheral Monitoring Stations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cooper, C.

2004-09-03

The goals of this project were to troubleshoot, repair, calibrate, and establish documentation regarding SLAC's (Stanford Linear Accelerator Center's) PMS (Peripheral Monitoring Station) system. The PMS system consists of seven PMSs that continuously monitor skyshine (neutron and photon) radiation levels in SLAC's environment. Each PMS consists of a boron trifluoride (BF{sub 3}) neutron detector (model RS-P1-0802-104 or NW-G-20-12) and a Geiger Moeller (GM) gamma ray detector (model TGM N107 or LND 719) together with their respective electronics. Electronics for each detector are housed in Nuclear Instrument Modules (NIMs) and are plugged into a NIM bin in the station. All communicationmore » lines from the stations to the Main Control Center (MCC) were tested prior to troubleshooting. To test communication with MCC, a pulse generator (Systron Donner model 100C) was connected to each channel in the PMS and data at MCC was checked for consistency. If MCC displayed no data, the communication cables to MCC or the CAMAC (Computer Automated Measurement and Control) crates were in need of repair. If MCC did display data, then it was known that the communication lines were intact. All electronics from each station were brought into the lab for troubleshooting. Troubleshooting usually consisted of connecting an oscilloscope or scaler (Ortec model 871 or 775) at different points in the circuit of each detector to record simulated pulses produced by a pulse generator; the input and output pulses were compared to establish the location of any problems in the circuit. Once any problems were isolated, repairs were done accordingly. The detectors and electronics were then calibrated in the field using radioactive sources. Calibration is a process that determines the response of the detector. Detector response is defined as the ratio of the number of counts per minute interpreted by the detector to the amount of dose equivalent rate (in mrem per hour, either calculated or measured). Detector response for both detectors is dependent upon the energy of the incident radiation; this trend had to be accounted for in the calibration of the BF{sub 3} detector. Energy dependence did not have to be taken into consideration when calibrating the GM detectors since GM detector response is only dependent on radiation energy below 100 keV; SLAC only produces a spectrum of gamma radiation above 100 keV. For the GM detector, calibration consisted of bringing a {sup 137}Cs source and a NIST-calibrated RADCAL Radiation Monitor Controller (model 9010) out to the field; the absolute dose rate was determined by the RADCAL device while simultaneously irradiating the GM detector to obtain a scaler reading corresponding to counts per minute. Detector response was then calculated. Calibration of the BF{sub 3} detector was done using NIST certified neutron sources of known emission rates and energies. Five neutron sources ({sup 238}PuBe, {sup 238}PuB, {sup 238}PuF4, {sup 238}PuLi and {sup 252}Cf) with different energies were used to account for the energy dependence of the response. The actual neutron dose rate was calculated by date-correcting NIST source data and considering the direct dose rate and scattered dose rate. Once the total dose rate (sum of the direct and scattered dose rates) was known, the response vs. energy curve was plotted. The first station calibrated (PMS6) was calibrated with these five neutron sources; all subsequent stations were calibrated with one neutron source and the energy dependence was assumed to be the same.« less

The Evaluation of the 0.07 and 3 mm Dose Equivalent with a Portable Beta Spectrometer

NASA Astrophysics Data System (ADS)

Hoshi, Katsuya; Yoshida, Tadayoshi; Tsujimura, Norio; Okada, Kazuhiko

Beta spectra of various nuclide species were measured using a commercially available compact spectrometer. The shape of the spectra obtained via the spectrometer was almost similar to that of the theoretical spectra. The beta dose equivalent at any depth was obtained as a product of the measured pulse height spectra and the appropriate conversion coefficients of ICRP Publication 74. The dose rates evaluated from the spectra were comparable with the reference dose rates of standard beta calibration sources. In addition, we were able to determine the dose equivalents with a relative error of indication of 10% without the need for complicated correction.

Energy-based dosimetry of low-energy, photon-emitting brachytherapy sources

NASA Astrophysics Data System (ADS)

Malin, Martha J.

Model-based dose calculation algorithms (MBDCAs) for low-energy, photon-emitting brachytherapy sources have advanced to the point where the algorithms may be used in clinical practice. Before these algorithms can be used, a methodology must be established to verify the accuracy of the source models used by the algorithms. Additionally, the source strength metric for these algorithms must be established. This work explored the feasibility of verifying the source models used by MBDCAs by measuring the differential photon fluence emitted from the encapsulation of the source. The measured fluence could be compared to that modeled by the algorithm to validate the source model. This work examined how the differential photon fluence varied with position and angle of emission from the source, and the resolution that these measurements would require for dose computations to be accurate to within 1.5%. Both the spatial and angular resolution requirements were determined. The techniques used to determine the resolution required for measurements of the differential photon fluence were applied to determine why dose-rate constants determined using a spectroscopic technique disagreed with those computed using Monte Carlo techniques. The discrepancy between the two techniques had been previously published, but the cause of the discrepancy was not known. This work determined the impact that some of the assumptions used by the spectroscopic technique had on the accuracy of the calculation. The assumption of isotropic emission was found to cause the largest discrepancy in the spectroscopic dose-rate constant. Finally, this work improved the instrumentation used to measure the rate at which energy leaves the encapsulation of a brachytherapy source. This quantity is called emitted power (EP), and is presented as a possible source strength metric for MBDCAs. A calorimeter that measured EP was designed and built. The theoretical framework that the calorimeter relied upon to measure EP was established. Four clinically relevant 125I brachytherapy sources were measured with the instrument. The accuracy of the measured EP was compared to an air-kerma strength-derived EP to test the accuracy of the instrument. The instrument was accurate to within 10%, with three out of the four source measurements accurate to within 4%.

Radiological environment within an NPP after a severe nuclear accident

NASA Astrophysics Data System (ADS)

Andgren, Karin; Fritioff, Karin; Buhr, Anna Maria Blixt; Huutoniemi, Tommi

2017-09-01

The radiological environment following a severe nuclear accident can be visualised on building layouts. The direct radiation in an area (or room) can be visualized on the layout by a colouring scheme depending on the dose rate level (for example orange for high gamma dose rate level and purple for an intermediate gamma dose rate level). Following the Fukushima accident, a need for update of these layouts has been identified at the Swedish nuclear power plant of Forsmark. Shielding calculations for areas where access is desired for severe accident management have been performed. Many different sources of radiation together with different types of shielding material contribute to the dose that would be received by a person entering the area. External radiation from radioactivity within e.g. pipes and components is considered and also external radiation from radioactivity in the air (originating from diffuse leakage of the containment atmosphere). Results are presented as dose rates for relevant dose points together with a method for estimating the dose rate levels for each of the rooms of the reactor building.

Dosimetric parameters of three new solid core I‐125 brachytherapy sources

PubMed Central

Solberg, Timothy D.; DeMarco, John J.; Hugo, Geoffrey; Wallace, Robert E.

2002-01-01

Monte Carlo calculations and TLD measurements have been performed for the purpose of characterizing dosimetric properties of new commercially available brachytherapy sources. All sources tested consisted of a solid core, upon which a thin layer of I125 has been adsorbed, encased within a titanium housing. The PharmaSeed BT‐125 source manufactured by Syncor is available in silver or palladium core configurations while the ADVANTAGE source from IsoAid has silver only. Dosimetric properties, including the dose rate constant, radial dose function, and anisotropy characteristics were determined according to the TG‐43 protocol. Additionally, the geometry function was calculated exactly using Monte Carlo and compared with both the point and line source approximations. The 1999 NIST standard was followed in determining air kerma strength. Dose rate constants were calculated to be 0.955±0.005,0.967±0.005, and 0.962±0.005 cGyh−1U−1 for the PharmaSeed BT‐125‐1, BT‐125‐2, and ADVANTAGE sources, respectively. TLD measurements were in excellent agreement with Monte Carlo calculations. Radial dose function, g(r), calculated to a distance of 10 cm, and anisotropy function F(r, θ), calculated for radii from 0.5 to 7.0 cm, were similar among all source configurations. Anisotropy constants, ϕ¯an, were calculated to be 0.941, 0.944, and 0.960 for the three sources, respectively. All dosimetric parameters were found to be in close agreement with previously published data for similar source configurations. The MCNP Monte Carlo code appears to be ideally suited to low energy dosimetry applications. PACS number(s): 87.53.–j PMID:11958652

The Effect of Measurement Area on Modelling UVR Dose to the Inner Canthus

NASA Astrophysics Data System (ADS)

Birt, Benjamin; Cowling, Ian; Coyne, Steve

People are exposed to varying amounts of UVR throughout their life from both natural and artificial light sources. The dose and rate of UVR exposure required for the formation of non-melanoma skin cancers is inconclusive. Certain regions on the face appear to exhibit a high rate of occurrence of Basal Cell Carcinomas (BCCs) in relation to the perceived dose of UVR. One of these regions is the inner canthus located on the medial side of the eye. The inner canthus appears to be well protected from large direct doses of ultraviolet radiation (UVR). Facial features such as eyelids, eye brow ridge, nasal bridge and cheek, combine to limit the solid angle of the field of view of the inner canthus to UVR from overhead sources. To explain the unexpected high rate of BCCs it is hypothesized that a percentage of the radiation incident on the eye is reflected onto the inner canthus. This paper showed that a portion of the radiation incident onto the eye was reflected towards the inner canthus. The percentage increase above the direct dose was only 2% across the whole region. As the detector elements decrease in size it is observed on a cellular level that some of the cells dose increased by 30% when the reflections were considered.

Intriguing radiation signatures at aviation altitudes

NASA Astrophysics Data System (ADS)

Tobiska, W. K.

2017-12-01

The Automated Radiation Measurements for Aerospace Safety (ARMAS) project captures absorbed dose in Si with a fleet of 6 instruments on research aircraft. These dose rates are then converted to an effective dose rate. Over 325 flights since 2013 have captured global radiation at nearly all altitudes and latitudes. The radiation is predominantly caused by atmospheric neutrons and protons from galactic cosmic rays (GCRs). We have not yet obtained dose from solar energetic particle (SEP) events, which are rather rare. On 13 flights we have also measured dose rates that are up to twice the GCR background for approximately a half an hour per event while flying at higher magnetic latitudes near 60 degrees. The timing of the radiation appears to be coincident with periods of mild geomagnetic disturbances while flying above 10 km at L-shells of 3 to 6. The radiation source is best modeled as secondary gamma-ray photons caused by precipitating ultra-relativistic electrons from the outer Van Allen radiation belt originating as loss cone electrons scattered by electromagnetic ion cyclotron (EMIC) waves. We describe the observations and the lines of evidence for this intriguing new radiation source relevant to aviation crew and frequent flyers.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, C A; Clarke, S D; Pozzi, S A

Purpose: To develop an instrument for measuring neutron and photon dose rates from mixed fields with a single device. Methods: Stilbene organic scintillators can be used to detect fast neutrons and photons. Stilbene was used to measure emission from mixed particle sources californium-252 (Cf-252) and plutonium-beryllium (PuBe). Many source detector configurations were used, along with varying amounts of shielding. Collected spectra were analyzed using pulse shape discrimination software, to separate neutron and photon interactions. With a measured light output to energy relationship the pulse height spectrum was converted to energy deposited in the detector. Energy deposited was converted to dosemore » with a variety of standard dose factors, for comparison to current methods. For validation, all measurements and processing was repeated using an EJ-309 liquid scintillator detector. Dose rates were also measured in the same configuration with commercially available dose meters for further validation. Results: Measurements of dose rates will show agreement across all methods. Higher accuracy of pulse shape discrimination at lower energies with stilbene leads to more accurate measurement of neutron and photon deposited dose. In strong fields of mixed particles discrimination can be performed well at a very low energy threshold. This shows accurate dose measurements over a large range of incident particle energy. Conclusion: Stilbene shows promise as a material for dose rate measurements due to its strong ability for separating neutrons and photon pulses and agreement with current methods. A dual particle dose meter would simplify methods which are currently limited to the measurement of only one particle type. Future work will investigate the use of a silicon photomultiplier to reduce the size and required voltage of the assembly, for practical use as a handheld survey meter, room monitor, or phantom installation. Funding From the United States Department of Energy and the National Nuclear Security Administration.« less

MO-AB-BRA-03: Development of Novel Real Time in Vivo EPID Treatment Verification for Brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fonseca, G; Podesta, M; Reniers, B

2016-06-15

Purpose: High Dose Rate (HDR) brachytherapy treatments are employed worldwide to treat a wide variety of cancers. However, in vivo dose verification remains a challenge with no commercial dosimetry system available to verify the treatment dose delivered to the patient. We propose a novel dosimetry system that couples an independent Monte Carlo (MC) simulation platform and an amorphous silicon Electronic Portal Imaging Device (EPID) to provide real time treatment verification. Methods: MC calculations predict the EPID response to the photon fluence emitted by the HDR source by simulating the patient, the source dwell positions and times, and treatment complexities suchmore » as tissue compositions/densities and different applicators. Simulated results are then compared against EPID measurements acquired with ∼0.14s time resolution which allows dose measurements for each dwell position. The EPID has been calibrated using an Ir-192 HDR source and experiments were performed using different phantoms, including tissue equivalent materials (PMMA, lung and bone). A source positioning accuracy of 0.2 mm, without including the afterloader uncertainty, was ensured using a robotic arm moving the source. Results: An EPID can acquire 3D Cartesian source positions and its response varies significantly due to differences in the material composition/density of the irradiated object, allowing detection of changes in patient geometry. The panel time resolution allows dose rate and dwell time measurements. Moreover, predicted EPID images obtained from clinical treatment plans provide anatomical information that can be related to the patient anatomy, mostly bone and air cavities, localizing the source inside of the patient using its anatomy as reference. Conclusion: Results obtained show the feasibility of the proposed dose verification system that is capable to verify all the brachytherapy treatment steps in real time providing data about treatment delivery quality and also applicator/structure motion during or between treatments.« less

Estimation of the Dose and Dose Rate Effectiveness Factor

NASA Technical Reports Server (NTRS)

Chappell, L.; Cucinotta, F. A.

2013-01-01

Current models to estimate radiation risk use the Life Span Study (LSS) cohort that received high doses and high dose rates of radiation. Transferring risks from these high dose rates to the low doses and dose rates received by astronauts in space is a source of uncertainty in our risk calculations. The solid cancer models recommended by BEIR VII [1], UNSCEAR [2], and Preston et al [3] is fitted adequately by a linear dose response model, which implies that low doses and dose rates would be estimated the same as high doses and dose rates. However animal and cell experiments imply there should be curvature in the dose response curve for tumor induction. Furthermore animal experiments that directly compare acute to chronic exposures show lower increases in tumor induction than acute exposures. A dose and dose rate effectiveness factor (DDREF) has been estimated and applied to transfer risks from the high doses and dose rates of the LSS cohort to low doses and dose rates such as from missions in space. The BEIR VII committee [1] combined DDREF estimates using the LSS cohort and animal experiments using Bayesian methods for their recommendation for a DDREF value of 1.5 with uncertainty. We reexamined the animal data considered by BEIR VII and included more animal data and human chromosome aberration data to improve the estimate for DDREF. Several experiments chosen by BEIR VII were deemed inappropriate for application to human risk models of solid cancer risk. Animal tumor experiments performed by Ullrich et al [4], Alpen et al [5], and Grahn et al [6] were analyzed to estimate the DDREF. Human chromosome aberration experiments performed on a sample of astronauts within NASA were also available to estimate the DDREF. The LSS cohort results reported by BEIR VII were combined with the new radiobiology results using Bayesian methods.

Inverse modelling of radionuclide release rates using gamma dose rate observations

NASA Astrophysics Data System (ADS)

Hamburger, Thomas; Stohl, Andreas; von Haustein, Christoph; Thummerer, Severin; Wallner, Christian

2014-05-01

Severe accidents in nuclear power plants such as the historical accident in Chernobyl 1986 or the more recent disaster in the Fukushima Dai-ichi nuclear power plant in 2011 have drastic impacts on the population and environment. The hazardous consequences reach out on a national and continental scale. Environmental measurements and methods to model the transport and dispersion of the released radionuclides serve as a platform to assess the regional impact of nuclear accidents - both, for research purposes and, more important, to determine the immediate threat to the population. However, the assessments of the regional radionuclide activity concentrations and the individual exposure to radiation dose underlie several uncertainties. For example, the accurate model representation of wet and dry deposition. One of the most significant uncertainty, however, results from the estimation of the source term. That is, the time dependent quantification of the released spectrum of radionuclides during the course of the nuclear accident. The quantification of the source terms of severe nuclear accidents may either remain uncertain (e.g. Chernobyl, Devell et al., 1995) or rely on rather rough estimates of released key radionuclides given by the operators. Precise measurements are mostly missing due to practical limitations during the accident. Inverse modelling can be used to realise a feasible estimation of the source term (Davoine and Bocquet, 2007). Existing point measurements of radionuclide activity concentrations are therefore combined with atmospheric transport models. The release rates of radionuclides at the accident site are then obtained by improving the agreement between the modelled and observed concentrations (Stohl et al., 2012). The accuracy of the method and hence of the resulting source term depends amongst others on the availability, reliability and the resolution in time and space of the observations. Radionuclide activity concentrations are observed on a relatively sparse grid and the temporal resolution of available data may be low within the order of hours or a day. Gamma dose rates on the other hand are observed routinely on a much denser grid and higher temporal resolution. Gamma dose rate measurements contain no explicit information on the observed spectrum of radionuclides and have to be interpreted carefully. Nevertheless, they provide valuable information for the inverse evaluation of the source term due to their availability (Saunier et al., 2013). We present a new inversion approach combining an atmospheric dispersion model and observations of radionuclide activity concentrations and gamma dose rates to obtain the source term of radionuclides. We use the Lagrangian particle dispersion model FLEXPART (Stohl et al., 1998; Stohl et al., 2005) to model the atmospheric transport of the released radionuclides. The gamma dose rates are calculated from the modelled activity concentrations. The inversion method uses a Bayesian formulation considering uncertainties for the a priori source term and the observations (Eckhardt et al., 2008). The a priori information on the source term is a first guess. The gamma dose rate observations will be used with inverse modelling to improve this first guess and to retrieve a reliable source term. The details of this method will be presented at the conference. This work is funded by the Bundesamt für Strahlenschutz BfS, Forschungsvorhaben 3612S60026. References Davoine, X. and Bocquet, M., Atmos. Chem. Phys., 7, 1549-1564, 2007. Devell, L., et al., OCDE/GD(96)12, 1995. Eckhardt, S., et al., Atmos. Chem. Phys., 8, 3881-3897, 2008. Saunier, O., et al., Atmos. Chem. Phys., 13, 11403-11421, 2013. Stohl, A., et al., Atmos. Environ., 32, 4245-4264, 1998. Stohl, A., et al., Atmos. Chem. Phys., 5, 2461-2474, 2005. Stohl, A., et al., Atmos. Chem. Phys., 12, 2313-2343, 2012.

Dose and dose rate effects of whole-body gamma-irradiation: II. Hematological variables and cytokines

NASA Technical Reports Server (NTRS)

Gridley, D. S.; Pecaut, M. J.; Miller, G. M.; Moyers, M. F.; Nelson, G. A.

2001-01-01

The goal of part II of this study was to evaluate the effects of gamma-radiation on circulating blood cells, functional characteristics of splenocytes, and cytokine expression after whole-body irradiation at varying total doses and at low- and high-dose-rates (LDR, HDR). Young adult C57BL/6 mice (n = 75) were irradiated with either 1 cGy/min or 80 cGy/min photons from a 60Co source to cumulative doses of 0.5, 1.5, and 3.0 Gy. The animals were euthanized at 4 days post-exposure for in vitro assays. Significant dose- (but not dose-rate-) dependent decreases were observed in erythrocyte and blood leukocyte counts, hemoglobin, hematocrit, lipopolysaccharide (LPS)-induced 3H-thymidine incorporation, and interleukin-2 (IL-2) secretion by activated spleen cells when compared to sham-irradiated controls (p < 0.05). Basal proliferation of leukocytes in the blood and spleen increased significantly with increasing dose (p < 0.05). Significant dose rate effects were observed only in thrombocyte counts. Plasma levels of transforming growth factor-beta 1 (TGF-beta 1) and splenocyte secretion of tumor necrosis factor-alpha (TNF-alpha) were not affected by either the dose or dose rate of radiation. The data demonstrate that the responses of blood and spleen were largely dependent upon the total dose of radiation employed and that an 80-fold difference in the dose rate was not a significant factor in the great majority of measurements.

SKYSHINEIII. Calculating Effects of Structure Design on Neutron Dose Rates in Air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lampley, C.M.; Andrews, C.M.; Wells, M.B.

1988-12-01

SKYSHINE was designed to aid in the evaluation of the effects of structure geometry on the gamma-ray dose rate at given detector positions outside of a building housing gamma-ray sources. The program considers a rectangular structure enclosed by four walls and a roof. Each of the walls and the roof of the building may be subdivided into up to nine different areas, representing different materials or different thicknesses of the same material for those positions of the wall or roof. Basic sets of iron and concrete slab transmission and reflection data for 6.2 MeV gamma-rays are part of the SKYSHINEmore » block data. These data, as well as parametric air transport data for line-beam sources at a number of energies between 0.6 MeV and 6.2 MeV and ranges to 3750 ft, are used to estimate the various components of the gamma-ray dose rate at positions outside of the building. The gamma-ray source is assumed to be a 6.2 MeV point-isotropic source. SKYSHINE-III provides an increase in versatility over the original SKYSHINE code in that it addresses both neutron and gamma-ray point sources. In addition, the emitted radiation may be characterized by an energy emission spectrum defined by the user. A new SKYSHINE data base is also included.« less

AREA MONITORING OF AMBIENT DOSE RATES IN PARTS OF SOUTH-WESTERN NIGERIA USING A GPS-INTEGRATED RADIATION SURVEY METER.

PubMed

Okeyode, I C; Rabiu, J A; Alatise, O O; Makinde, V; Akinboro, F G; Al-Azmi, D; Mustapha, A O

2017-04-01

A radiation monitoring system comprising a Geiger-Muller counter connected to a smart phone via Bluetooth was used for a dose rate survey in some parts of south-western Nigeria. The smart phone has the Geographical Positioning System, which provides the navigation information and saves it along with the dose rate data. A large number of data points was obtained that shows the dose rate distribution within the region. The results show that the ambient dose rates in the region range from 60 to 520 nSv -1 and showed a bias that is attributable to the influence of geology on the ambient radiation dose in the region. The geology influence was demonstrated by superimposing the dose rate plot and the geological map of the area. The potential applications of the device in determining baseline information and in area monitoring, e.g. for lost or abandoned sources, radioactive materials stockpiles, etc., were discussed in the article, particularly against the background of Nigeria's plan to develop its nuclear power program. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Potential radiation control of biofouling bacteria on intake filters

NASA Astrophysics Data System (ADS)

Eichholz, Geoffrey G.; Jones, Cynthia G.; Haynes, Harold E.

The biofouling of filters at deep wells supplying water for industrial and drinking water purposes by various iron- and sulfur-reducing bacteria is a wide-spread problem in the United States and can cause serious economic losses. Among the means of control, steam heating or chemical additives can be applied only intermittently and have their own environmental impact. Preliminary studies have shown that installation of a sealed gamma radiation source may provide an alternative solution. Analysis of a range of water samples from contaminated wells identified many of the samples as rich in barsiderocapsa and barpseudomona bacteria. Static and dynamic experiments on water samples at various does and dose rates have shown that these organisms are relatively radiation-sensitive, with a lethal dose in the range of 200-400Gy (20-40kR). Since the main objective is to restrict growth or deposit of plaque on filters, dose rates of the order of 50-75 Gy/hr would be adequate. Such dose rates could be obtained with relatively weak sources, depending on filter dimensions. A conceptual design for such systems has been proposed.

Evaluation Of Shielding Efficacy Of A Ferrite Containing Ceramic Material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Verst, C.

2015-10-12

The shielding evaluation of the ferrite based Mitsuishi ceramic material has produced for several radiation sources and possible shielding sizes comparative dose attenuation measurements and simulated projections. High resolution gamma spectroscopy provided uncollided and scattered photon spectra at three energies, confirming theoretical estimates of the ceramic’s mass attenuation coefficient, μ/ρ. High level irradiation experiments were performed using Co-60, Cs-137, and Cf-252 sources to measure penetrating dose rates through steel, lead, concrete, and the provided ceramic slabs. The results were used to validate the radiation transport code MCNP6 which was then used to generate dose rate attenuation curves as a functionmore » of shielding material, thickness, and mass for photons and neutrons ranging in energy from 200 keV to 2 MeV.« less

Toward endobronchial Ir-192 high-dose-rate brachytherapy therapeutic optimization

NASA Astrophysics Data System (ADS)

Gay, H. A.; Allison, R. R.; Downie, G. H.; Mota, H. C.; Austerlitz, C.; Jenkins, T.; Sibata, C. H.

2007-06-01

A number of patients with lung cancer receive either palliative or curative high-dose-rate (HDR) endobronchial brachytherapy. Up to a third of patients treated with endobronchial HDR die from hemoptysis. Rather than accept hemoptysis as an expected potential consequence of HDR, we have calculated the radial dose distribution for an Ir-192 HDR source, rigorously examined the dose and prescription points recommended by the American Brachytherapy Society (ABS), and performed a radiobiological-based analysis. The radial dose rate of a commercially available Ir-192 source was calculated with a Monte Carlo simulation. Based on the linear quadratic model, the estimated palliative, curative and blood vessel rupture radii from the center of an Ir-192 source were obtained for the ABS recommendations and a series of customized HDR prescriptions. The estimated radius at risk for blood vessel perforation for the ABS recommendations ranges from 7 to 9 mm. An optimized prescription may in some situations reduce this radius to 4 mm. The estimated blood perforation radius is generally smaller than the palliative radius. Optimized and individualized endobronchial HDR prescriptions are currently feasible based on our current understanding of tumor and normal tissue radiobiology. Individualized prescriptions could minimize complications such as fatal hemoptysis without sacrificing efficacy. Fiducial stents, HDR catheter centering or spacers and the use of CT imaging to better assess the relationship between the catheter and blood vessels promise to be useful strategies for increasing the therapeutic index of this treatment modality. Prospective trials employing treatment optimization algorithms are needed.

A photon spectrometric dose-rate constant determination for the Advantage Pd-103 brachytherapy source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Zhe Jay; Bongiorni, Paul; Nath, Ravinder

Purpose: Although several dosimetric characterizations using Monte Carlo simulation and thermoluminescent dosimetry (TLD) have been reported for the new Advantage Pd-103 source (IsoAid, LLC, Port Richey, FL), no AAPM consensus value has been established for the dosimetric parameters of the source. The aim of this work was to perform an additional dose-rate constant ({Lambda}) determination using a recently established photon spectrometry technique (PST) that is independent of the published TLD and Monte Carlo techniques. Methods: Three Model IAPD-103A Advantage Pd-103 sources were used in this study. The relative photon energy spectrum emitted by each source along the transverse axis wasmore » measured using a high-resolution germanium spectrometer designed for low-energy photons. For each source, the dose-rate constant was determined from its emitted energy spectrum. The PST-determined dose-rate constant ({sub PST}{Lambda}) was then compared to those determined by TLD ({sub TLD}{Lambda}) and Monte Carlo ({sub MC}{Lambda}) techniques. A likely consensus {Lambda} value was estimated as the arithmetic mean of the average {Lambda} values determined by each of three different techniques. Results: The average {sub PST}{Lambda} value for the three Advantage sources was found to be (0.676{+-}0.026) cGyh{sup -1} U{sup -1}. Intersource variation in {sub PST}{Lambda} was less than 0.01%. The {sub PST}{Lambda} was within 2% of the reported {sub MC}{Lambda} values determined by PTRAN, EGSnrc, and MCNP5 codes. It was 3.4% lower than the reported {sub TLD}{Lambda}. A likely consensus {Lambda} value was estimated to be (0.688{+-}0.026) cGyh{sup -1} U{sup -1}, similar to the AAPM consensus values recommended currently for the Theragenics (Buford, GA) Model 200 (0.686{+-}0.033) cGyh{sup -1} U{sup -1}, the NASI (Chatsworth, CA) Model MED3633 (0.688{+-}0.033) cGyh{sup -1} U{sup -1}, and the Best Medical (Springfield, VA) Model 2335 (0.685{+-}0.033) cGyh{sup -1} U{sup -1} {sup 103}Pd sources. Conclusions: An independent {Lambda} determination has been performed for the Advantage Pd-103 source. The {sub PST}{Lambda} obtained in this work provides additional information needed for establishing a more accurate consensus {Lambda} value for the Advantage Pd-103 source.« less

Iodine 125 source in interstitial tumor therapy. Clinical and biological considerations.

PubMed

Kim, J H; Hilaris, B

1975-01-01

Our clinical experience with interstitial tumor therapy is presented in 2 groups of patients: 98 patients with metastatic carcinoma in neck lymph nodes implanted with iodine 125, iridium 192 or radon 222 encapsulated sources, and 105 patients with primary unresectable lung tumors, which were implanted either with radon 222 or iodine 125 seeds. The local tumor control rates with iodine 125, radon 222 and iridium 192 were 78 per cent (38/49), 65 per cent (15/23) and 58 per cent (7/12), while the local complication rates were 17 per cent, 35 per cent and 43 per cent, respectively. An analysis of the tumor control rate as a function of the implanted tumor dose shows that the iodine 125 implants with a delivery of the minimal effective tumor dose of 16,000 rads have a higher therapeutic effect than either radon 222 or iridium 192. The results of the patients with unresectable lung tumors similarly show that the implants with iodine 125 sources are superior to those with radon 222. The advantages could stem from the better spatial dose distribution, and from radiobiologic considerations associated with low dose rates, continous irradiation, and possibly gains in RBE. There present clinical data clearly demonstrate that iodine 125 seeds have a higher therapeutic ratio than radon 222 seeds. There are, in addition, distinct physical advantages making iodine 125 an attractive substitute for radon 222 for the interstitial implantation of malignant tumors.

Simulation of angular and energy distributions of the PTB beta secondary standard.

PubMed

Faw, R E; Simons, G G; Gianakon, T A; Bayouth, J E

1990-09-01

Calculations and measurements have been performed to assess radiation doses delivered by the PTB Secondary Standard that employs 147Pm, 204Tl, and 90Sr:90Y sources in prescribed geometries, and features "beam-flattening" filters to assure uniformity of delivered doses within a 5-cm radius of the axis from source to detector plane. Three-dimensional, coupled, electron-photon Monte Carlo calculations, accounting for transmission through the source encapsulation and backscattering from the source mounting, led to energy spectra and angular distributions of electrons penetrating the source encapsulation that were used in the representation of pseudo sources of electrons for subsequent transport through the atmosphere, filters, and detectors. Calculations were supplemented by measurements made using bare LiF TLD chips on a thick polymethyl methacrylate phantom. Measurements using the 204Tl and 90Sr:90Y sources revealed that, even in the absence of the beam-flattening filters, delivered dose rates were very uniform radially. Dosimeter response functions (TLD:skin dose ratios) were calculated and confirmed experimentally for all three beta-particle sources and for bare LiF TLDs ranging in mass thickness from 10 to 235 mg cm-2.

Radiation protection for an intra-operative X-ray device

PubMed Central

Eaton, D J; Gonzalez, R; Duck, S; Keshtgar, M

2011-01-01

Objectives Therapeutic partial breast irradiation can be delivered intra-operatively using the Intrabeam 50 kVp compact X-ray device. Spherical applicators are added to the source to give an isotropic radiation dose. The low energy of this unit leads to rapid attenuation with distance, but dose rates are much greater than for diagnostic procedures. Methods To investigate the shielding requirements for this unit, attenuation measurements were carried out with manufacturer-provided tungsten–rubber sheets, lead, plasterboard and bricks. A prospective environmental dose rate survey was also conducted in the designated theatre. Results As a result of isotropic geometry, the scattered dose around shielding can be 1% of primary and thus often dominates measured dose rates compared with transmission. The absorbed dose rate of the unshielded source at 1 m was 11.6 mGy h−1 but this was reduced by 95% with the shielding sheets. Measured values for the common shielding materials were similar to reference data for the attenuation of a 50 kVp diagnostic X-ray beam. Two lead screens were constructed to shield operators remaining in the theatre and an air vent into a service corridor. A lead apron would also provide suitable attenuation, although a screen allows greater flexibility for treatment operators. With these measures, staff doses were reduced to negligible quantities. Survey measurements taken during patient treatments confirmed no additional measures were required, but the theatre should be a controlled area and access restricted. Conclusion Results from this study and reference data can be used for planning other facilities. PMID:21304003

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell Feder and Mahmoud Z. Yousef

Neutronics analysis to find nuclear heating rates and personnel dose rates were conducted in support of the integration of diagnostics in to the ITER Upper Port Plugs. Simplified shielding models of the Visible-Infrared diagnostic and of the ECH heating system were incorporated in to the ITER global CAD model. Results for these systems are representative of typical designs with maximum shielding and a small aperture (Vis-IR) and minimal shielding with a large aperture (ECH). The neutronics discrete-ordinates code ATTILA® and SEVERIAN® (the ATTILA parallel processing version) was used. Material properties and the 500 MW D-T volume source were taken frommore » the ITER “Brand Model” MCNP benchmark model. A biased quadrature set equivelant to Sn=32 and a scattering degree of Pn=3 were used along with a 46-neutron and 21-gamma FENDL energy subgrouping. Total nuclear heating (neutron plug gamma heating) in the upper port plugs ranged between 380 and 350 kW for the Vis-IR and ECH cases. The ECH or Large Aperture model exhibited lower total heating but much higher peak volumetric heating on the upper port plug structure. Personnel dose rates are calculated in a three step process involving a neutron-only transport calculation, the generation of activation volume sources at pre-defined time steps and finally gamma transport analyses are run for selected time steps. ANSI-ANS 6.1.1 1977 Flux-to-Dose conversion factors were used. Dose rates were evaluated for 1 full year of 500 MW DT operation which is comprised of 3000 1800-second pulses. After one year the machine is shut down for maintenance and personnel are permitted to access the diagnostic interspace after 2-weeks if dose rates are below 100 μSv/hr. Dose rates in the Visible-IR diagnostic model after one day of shutdown were 130 μSv/hr but fell below the limit to 90 μSv/hr 2-weeks later. The Large Aperture or ECH style shielding model exhibited higher and more persistent dose rates. After 1-day the dose rate was 230 μSv/hr but was still at 120 μSv/hr 4-weeks later. __________________________________________________« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Russell E. Feder and Mahmoud Z. Youssef

Neutronics analysis to find nuclear heating rates and personnel dose rates were conducted in support of the integration of diagnostics in to the ITER Upper Port Plugs. Simplified shielding models of the Visible-Infrared diagnostic and of a large aperture diagnostic were incorporated in to the ITER global CAD model. Results for these systems are representative of typical designs with maximum shielding and a small aperture (Vis-IR) and minimal shielding with a large aperture. The neutronics discrete-ordinates code ATTILA® and SEVERIAN® (the ATTILA parallel processing version) was used. Material properties and the 500 MW D-T volume source were taken from themore » ITER “Brand Model” MCNP benchmark model. A biased quadrature set equivelant to Sn=32 and a scattering degree of Pn=3 were used along with a 46-neutron and 21-gamma FENDL energy subgrouping. Total nuclear heating (neutron plug gamma heating) in the upper port plugs ranged between 380 and 350 kW for the Vis-IR and Large Aperture cases. The Large Aperture model exhibited lower total heating but much higher peak volumetric heating on the upper port plug structure. Personnel dose rates are calculated in a three step process involving a neutron-only transport calculation, the generation of activation volume sources at pre-defined time steps and finally gamma transport analyses are run for selected time steps. ANSI-ANS 6.1.1 1977 Flux-to-Dose conversion factors were used. Dose rates were evaluated for 1 full year of 500 MW DT operation which is comprised of 3000 1800-second pulses. After one year the machine is shut down for maintenance and personnel are permitted to access the diagnostic interspace after 2-weeks if dose rates are below 100 μSv/hr. Dose rates in the Visible-IR diagnostic model after one day of shutdown were 130 μSv/hr but fell below the limit to 90 μSv/hr 2-weeks later. The Large Aperture style shielding model exhibited higher and more persistent dose rates. After 1-day the dose rate was 230 μSv/hr but was still at 120 μSv/hr 4-weeks later.« less

10 CFR 36.2 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-01-01

... radioactive sealed sources for the irradiation of objects or materials and in which radiation dose rates... source and the area subject to irradiation are contained within a device and are not accessible to... supervisor present. Panoramic dry-source-storage irradiator means an irradiator in which the irradiations...

10 CFR 36.2 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-01-01

... radioactive sealed sources for the irradiation of objects or materials and in which radiation dose rates... source and the area subject to irradiation are contained within a device and are not accessible to... supervisor present. Panoramic dry-source-storage irradiator means an irradiator in which the irradiations...

10 CFR 36.2 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-01-01

... radioactive sealed sources for the irradiation of objects or materials and in which radiation dose rates... source and the area subject to irradiation are contained within a device and are not accessible to... supervisor present. Panoramic dry-source-storage irradiator means an irradiator in which the irradiations...

Evaluation of a Proposed Biodegradable 188Re Source for Brachytherapy Application

PubMed Central

Khorshidi, Abdollah; Ahmadinejad, Marjan; Hamed Hosseini, S.

2015-01-01

Abstract This study aimed to evaluate dosimetric characteristics based on Monte Carlo (MC) simulations for a proposed beta emitter bioglass 188Re seed for internal radiotherapy applications. The bioactive glass seed has been developed using the sol-gel technique. The simulations were performed for the seed using MC radiation transport code to investigate the dosimetric factors recommended by the AAPM Task Group 60 (TG-60). Dose distributions due to the beta and photon radiation were predicted at different radial distances surrounding the source. The dose rate in water at the reference point was calculated to be 7.43 ± 0.5 cGy/h/μCi. The dosimetric factors consisting of the reference point dose rate, D(r0,θ0), the radial dose function, g(r), the 2-dimensional anisotropy function, F(r,θ), the 1-dimensional anisotropy function, φan(r), and the R90 quantity were estimated and compared with several available beta-emitting sources. The element 188Re incorporated in bioactive glasses produced by the sol-gel technique provides a suitable solution for producing new materials for seed implants applied to brachytherapy applications in prostate and liver cancers treatment. Dose distribution of 188Re seed was greater isotropic than other commercially attainable encapsulated seeds, since it has no end weld to attenuate radiation. The beta radiation-emitting 188Re source provides high doses of local radiation to the tumor tissue and the short range of the beta particles limit damage to the adjacent normal tissue. PMID:26181543

Spectrum determination and modification of the AFRL Co-60 cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turinetti, J.R.; Kemp, W.T.; Chavez, J.R.

The AFRL Co-60 cell at Phillips Research Site, Kirtland Air Force Base, is a 1500 ft{sup 2} concrete room with a 5200 Ci, as of 18 December 1996, J.L. Shepherd Co-60 source. The source provides high dose rate ionizing radiation up to 12000 rad(Si)/min. The Co-60 cell is used to characterize total-dose gamma effects of microelectronic and photonic devices, circuits, and subsystems. The spectrum of a Co-60 facility includes more than the two photopeaks of gamma ray emission. If there is a large low energy contribution from scattering, dose enhancement might be a problem. It is important to know themore » spectrum of a Co-60 facility and understand how experimental modifications can change that spectrum. The AFRL Co-60 cell spectrum is found to be a clean spectrum with small low energy contributions and dominant Co-60 photopeaks. Experimental modifications to reduce dose enhancement such as the use of a Pb/Al box and even better a Pb/Sn/Cu/Al box are found to decrease the low energy contributions. Experimental modifications to reduce dose rate such as using lead attenuators in front of the experiment and/or raising the source partially are found to significantly alter the spectrum, sometimes creating large low energy contributions.« less

SU-C-16A-04: Dosimetric Validation of a Partially-Shielded Gd-153 Brachytherapy Concept

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, X; Adams, Q; Flynn, R

Purpose: To demonstrate by measurement that using partially shielded Gd-153 sources for rotating-shield brachytherapy (RSBT) is feasible. RSBT is a potentially superior alternative to conventional high-dose-rate brachytherapy and provides the opportunity to dramatically improve tumor dose conformity for the treatment of, for example, prostate cancer. Methods: A custom-built, stainless steel encapsulated 150 mCi Gd-153 capsule with an outer length of 12.8 mm, outer diameter of 2.10 mm, active length of 9.98 mm, and active diameter of 1.53 mm was used. A partially shielded catheter was constructed with a 500 μm platinum shield and a 500 μm aluminum emission window, bothmore » with 180° azimuthal coverage. An acrylic phantom was constructed to measure the dose distributions from the shielded catheter in the transverse plane using Gafchromic EBT3 films. Film calibration curves were generated from 50, 70, and 100 kVp x-ray beams with NIST-traceable air kerma values to account for energy variation. Results: The transmission ratios of platinum to aluminum shielding at 1 cm off-axis are 7.5% and 7.6% for Monte Carlo (MCNP5) predicted and experimental results, respectively. The predicted/measured relative dose rates at 1 cm, 2 cm and 3 cm off-axis through the Al window were 100%/92.9%, 28.6%/27.0% and 13.8%/12.7%, respectively. Through the Pt shield, the predicted/measured relative dose rates were 7.5%/7.1%, 3.8%/3.0% and 2.4%/1.7%, respectively. Conclusion: Using partially-shielded Gd-153 sources for RSBT is a promising approach to improving brachytherapy dose distributions. The next step in making Gd-153 based RSBT a reality is developing a Gd-153 source that is small enough such that the source, shield, and catheter all fit within a 16 gauge needle, which has a 1.65 mm diameter. University of Iowa Research Foundation.« less

Suitability of point kernel dose calculation techniques in brachytherapy treatment planning

PubMed Central

Lakshminarayanan, Thilagam; Subbaiah, K. V.; Thayalan, K.; Kannan, S. E.

2010-01-01

Brachytherapy treatment planning system (TPS) is necessary to estimate the dose to target volume and organ at risk (OAR). TPS is always recommended to account for the effect of tissue, applicator and shielding material heterogeneities exist in applicators. However, most brachytherapy TPS software packages estimate the absorbed dose at a point, taking care of only the contributions of individual sources and the source distribution, neglecting the dose perturbations arising from the applicator design and construction. There are some degrees of uncertainties in dose rate estimations under realistic clinical conditions. In this regard, an attempt is made to explore the suitability of point kernels for brachytherapy dose rate calculations and develop new interactive brachytherapy package, named as BrachyTPS, to suit the clinical conditions. BrachyTPS is an interactive point kernel code package developed to perform independent dose rate calculations by taking into account the effect of these heterogeneities, using two regions build up factors, proposed by Kalos. The primary aim of this study is to validate the developed point kernel code package integrated with treatment planning computational systems against the Monte Carlo (MC) results. In the present work, three brachytherapy applicators commonly used in the treatment of uterine cervical carcinoma, namely (i) Board of Radiation Isotope and Technology (BRIT) low dose rate (LDR) applicator and (ii) Fletcher Green type LDR applicator (iii) Fletcher Williamson high dose rate (HDR) applicator, are studied to test the accuracy of the software. Dose rates computed using the developed code are compared with the relevant results of the MC simulations. Further, attempts are also made to study the dose rate distribution around the commercially available shielded vaginal applicator set (Nucletron). The percentage deviations of BrachyTPS computed dose rate values from the MC results are observed to be within plus/minus 5.5% for BRIT LDR applicator, found to vary from 2.6 to 5.1% for Fletcher green type LDR applicator and are up to −4.7% for Fletcher-Williamson HDR applicator. The isodose distribution plots also show good agreements with the results of previous literatures. The isodose distributions around the shielded vaginal cylinder computed using BrachyTPS code show better agreement (less than two per cent deviation) with MC results in the unshielded region compared to shielded region, where the deviations are observed up to five per cent. The present study implies that the accurate and fast validation of complicated treatment planning calculations is possible with the point kernel code package. PMID:20589118

SU-E-T-467: Monte Carlo Dosimetric Study of the New Flexisource Co-60 High Dose Rate Source.

PubMed

Vijande, J; Granero, D; Perez-Calatayud, J; Ballester, F

2012-06-01

Recently, a new HDR 60Co brachytherapy source, Flexisource Co-60, has been developed (Nucletron B.V.). This study aims to obtain quality dosimetric data for this source for its use in clinical practice as required by AAPM and ESTRO. Penelope2008 and GEANT4 Monte Carlo codes were used to dosimetrically characterize this source. Water composition and mass density was that recommended by AAPM. Due to the high energy of the 60Co, dose for small distances cannot be approximated by collisional kerma. Therefore, we have considered absorbed dose to water for r<0.75 cm and collisional kerma from 0.75 0.8 cm and up to 2% closer to the source. Using Penelope2008 and GEANT4, an average of Î> = 1.085±0.003 cGy/(h U) (with k = 1, Type A uncertainties) was obtained. Dose rate constant, radial dose function and anisotropy functions for the Flexisource Co-60 are compared with published data for other Co-60 sources. Dosimetric data are provided for the new Flexisource Co-60 source not studied previously in the literature. Using the data provided by this study in the treatment planning systems, it can be used in clinical practice. This project has been funded by Nucletron BV. © 2012 American Association of Physicists in Medicine.

On the use of multi-dimensional scaling and electromagnetic tracking in high dose rate brachytherapy

NASA Astrophysics Data System (ADS)

Götz, Th I.; Ermer, M.; Salas-González, D.; Kellermeier, M.; Strnad, V.; Bert, Ch; Hensel, B.; Tomé, A. M.; Lang, E. W.

2017-10-01

High dose rate brachytherapy affords a frequent reassurance of the precise dwell positions of the radiation source. The current investigation proposes a multi-dimensional scaling transformation of both data sets to estimate dwell positions without any external reference. Furthermore, the related distributions of dwell positions are characterized by uni—or bi—modal heavy—tailed distributions. The latter are well represented by α—stable distributions. The newly proposed data analysis provides dwell position deviations with high accuracy, and, furthermore, offers a convenient visualization of the actual shapes of the catheters which guide the radiation source during the treatment.

A quantitative three-dimensional dose attenuation analysis around Fletcher-Suit-Delclos due to stainless steel tube for high-dose-rate brachytherapy by Monte Carlo calculations.

PubMed

Parsai, E Ishmael; Zhang, Zhengdong; Feldmeier, John J

2009-01-01

The commercially available brachytherapy treatment-planning systems today, usually neglects the attenuation effect from stainless steel (SS) tube when Fletcher-Suit-Delclos (FSD) is used in treatment of cervical and endometrial cancers. This could lead to potential inaccuracies in computing dwell times and dose distribution. A more accurate analysis quantifying the level of attenuation for high-dose-rate (HDR) iridium 192 radionuclide ((192)Ir) source is presented through Monte Carlo simulation verified by measurement. In this investigation a general Monte Carlo N-Particles (MCNP) transport code was used to construct a typical geometry of FSD through simulation and compare the doses delivered to point A in Manchester System with and without the SS tubing. A quantitative assessment of inaccuracies in delivered dose vs. the computed dose is presented. In addition, this investigation expanded to examine the attenuation-corrected radial and anisotropy dose functions in a form parallel to the updated AAPM Task Group No. 43 Report (AAPM TG-43) formalism. This will delineate quantitatively the inaccuracies in dose distributions in three-dimensional space. The changes in dose deposition and distribution caused by increased attenuation coefficient resulted from presence of SS are quantified using MCNP Monte Carlo simulations in coupled photon/electron transport. The source geometry was that of the Vari Source wire model VS2000. The FSD was that of the Varian medical system. In this model, the bending angles of tandem and colpostats are 15 degrees and 120 degrees , respectively. We assigned 10 dwell positions to the tandem and 4 dwell positions to right and left colpostats or ovoids to represent a typical treatment case. Typical dose delivered to point A was determined according to Manchester dosimetry system. Based on our computations, the reduction of dose to point A was shown to be at least 3%. So this effect presented by SS-FSD systems on patient dose is of concern.

Real-Time Verification of a High-Dose-Rate Iridium 192 Source Position Using a Modified C-Arm Fluoroscope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nose, Takayuki, E-mail: nose-takayuki@nms.ac.jp; Chatani, Masashi; Otani, Yuki

Purpose: High-dose-rate (HDR) brachytherapy misdeliveries can occur at any institution, and they can cause disastrous results. Even a patient's death has been reported. Misdeliveries could be avoided with real-time verification methods. In 1996, we developed a modified C-arm fluoroscopic verification of an HDR Iridium 192 source position prevent these misdeliveries. This method provided excellent image quality sufficient to detect errors, and it has been in clinical use at our institutions for 20 years. The purpose of the current study is to introduce the mechanisms and validity of our straightforward C-arm fluoroscopic verification method. Methods and Materials: Conventional X-ray fluoroscopic images aremore » degraded by spurious signals and quantum noise from Iridium 192 photons, which make source verification impractical. To improve image quality, we quadrupled the C-arm fluoroscopic X-ray dose per pulse. The pulse rate was reduced by a factor of 4 to keep the average exposure compliant with Japanese medical regulations. The images were then displayed with quarter-frame rates. Results: Sufficient quality was obtained to enable observation of the source position relative to both the applicators and the anatomy. With this method, 2 errors were detected among 2031 treatment sessions for 370 patients within a 6-year period. Conclusions: With the use of a modified C-arm fluoroscopic verification method, treatment errors that were otherwise overlooked were detected in real time. This method should be given consideration for widespread use.« less

Real-Time Verification of a High-Dose-Rate Iridium 192 Source Position Using a Modified C-Arm Fluoroscope.

PubMed

Nose, Takayuki; Chatani, Masashi; Otani, Yuki; Teshima, Teruki; Kumita, Shinichirou

2017-03-15

High-dose-rate (HDR) brachytherapy misdeliveries can occur at any institution, and they can cause disastrous results. Even a patient's death has been reported. Misdeliveries could be avoided with real-time verification methods. In 1996, we developed a modified C-arm fluoroscopic verification of an HDR Iridium 192 source position prevent these misdeliveries. This method provided excellent image quality sufficient to detect errors, and it has been in clinical use at our institutions for 20 years. The purpose of the current study is to introduce the mechanisms and validity of our straightforward C-arm fluoroscopic verification method. Conventional X-ray fluoroscopic images are degraded by spurious signals and quantum noise from Iridium 192 photons, which make source verification impractical. To improve image quality, we quadrupled the C-arm fluoroscopic X-ray dose per pulse. The pulse rate was reduced by a factor of 4 to keep the average exposure compliant with Japanese medical regulations. The images were then displayed with quarter-frame rates. Sufficient quality was obtained to enable observation of the source position relative to both the applicators and the anatomy. With this method, 2 errors were detected among 2031 treatment sessions for 370 patients within a 6-year period. With the use of a modified C-arm fluoroscopic verification method, treatment errors that were otherwise overlooked were detected in real time. This method should be given consideration for widespread use. Copyright © 2016 Elsevier Inc. All rights reserved.

Dosimetric Consistency of Co-60 Teletherapy Unit- a ten years Study

PubMed Central

Baba, Misba H; Mohib-ul-Haq, M.; Khan, Aijaz A.

2013-01-01

Objective The goal of the Radiation standards and Dosimetry is to ensure that the output of the Teletherapy Unit is within ±2% of the stated one and the output of the treatment dose calculation methods are within ±5%. In the present paper, we studied the dosimetry of Cobalt-60 (Co-60) Teletherapy unit at Sher-I-Kashmir Institute of Medical Sciences (SKIMS) for last 10 years. Radioactivity is the phenomenon of disintegration of unstable nuclides called radionuclides. Among these radionuclides, Cobalt-60, incorporated in Telecobalt Unit, is commonly used in therapeutic treatment of cancer. Cobalt-60 being unstable decays continuously into Ni-60 with half life of 5.27 years thereby resulting in the decrease in its activity, hence dose rate (output). It is, therefore, mandatory to measure the dose rate of the Cobalt-60 source regularly so that the patient receives the same dose every time as prescribed by the radiation oncologist. The under dosage may lead to unsatisfactory treatment of cancer and over dosage may cause radiation hazards. Our study emphasizes the consistency between actual output and output obtained using decay method. Methodology The methodology involved in the present study is the calculations of actual dose rate of Co-60 Teletherapy Unit by two techniques i.e. Source to Surface Distance (SSD) and Source to Axis Distance (SAD), used for the External Beam Radiotherapy, of various cancers, using the standard methods. Thereby, a year wise comparison has been made between average actual dosimetric output (dose rate) and the average expected output values (obtained by using decay method for Co-60.) Results The present study shows that there is a consistency in the average output (dose rate) obtained by the actual dosimetry values and the expected output values obtained using decay method. The values obtained by actual dosimetry are within ±2% of the expected values. Conclusion The results thus obtained in a year wise comparison of average output by actual dosimetry done regularly as a part of Quality Assurance of the Telecobalt Radiotherapy Unit and its deviation from the expected output data is within the permissible limits. Thus our study shows a trend towards uniformity and a better dose delivery. PMID:23559901

WE-DE-201-05: Evaluation of a Windowless Extrapolation Chamber Design and Monte Carlo Based Corrections for the Calibration of Ophthalmic Applicators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, J; Culberson, W; DeWerd, L

Purpose: To test the validity of a windowless extrapolation chamber used to measure surface dose rate from planar ophthalmic applicators and to compare different Monte Carlo based codes for deriving correction factors. Methods: Dose rate measurements were performed using a windowless, planar extrapolation chamber with a {sup 90}Sr/{sup 90}Y Tracerlab RA-1 ophthalmic applicator previously calibrated at the National Institute of Standards and Technology (NIST). Capacitance measurements were performed to estimate the initial air gap width between the source face and collecting electrode. Current was measured as a function of air gap, and Bragg-Gray cavity theory was used to calculate themore » absorbed dose rate to water. To determine correction factors for backscatter, divergence, and attenuation from the Mylar entrance window found in the NIST extrapolation chamber, both EGSnrc Monte Carlo user code and Monte Carlo N-Particle Transport Code (MCNP) were utilized. Simulation results were compared with experimental current readings from the windowless extrapolation chamber as a function of air gap. Additionally, measured dose rate values were compared with the expected result from the NIST source calibration to test the validity of the windowless chamber design. Results: Better agreement was seen between EGSnrc simulated dose results and experimental current readings at very small air gaps (<100 µm) for the windowless extrapolation chamber, while MCNP results demonstrated divergence at these small gap widths. Three separate dose rate measurements were performed with the RA-1 applicator. The average observed difference from the expected result based on the NIST calibration was −1.88% with a statistical standard deviation of 0.39% (k=1). Conclusion: EGSnrc user code will be used during future work to derive correction factors for extrapolation chamber measurements. Additionally, experiment results suggest that an entrance window is not needed in order for an extrapolation chamber to provide accurate dose rate measurements for a planar ophthalmic applicator.« less

Environmental radioactivity in the UK: the airborne geophysical view of dose rate estimates.

PubMed

Beamish, David

2014-12-01

This study considers UK airborne gamma-ray data obtained through a series of high spatial resolution, low altitude surveys over the past decade. The ground concentrations of the naturally occurring radionuclides Potassium, Thorium and Uranium are converted to air absorbed dose rates and these are used to assess terrestrial exposure levels from both natural and technologically enhanced sources. The high resolution airborne information is also assessed alongside existing knowledge from soil sampling and ground-based measurements of exposure levels. The surveys have sampled an extensive number of the UK lithological bedrock formations and the statistical information provides examples of low dose rate lithologies (the formations that characterise much of southern England) to the highest sustained values associated with granitic terrains. The maximum dose rates (e.g. >300 nGy h(-1)) encountered across the sampled granitic terrains are found to vary by a factor of 2. Excluding granitic terrains, the most spatially extensive dose rates (>50 nGy h(-1)) are found in association with the Mercia Mudstone Group (Triassic argillaceous mudstones) of eastern England. Geological associations between high dose rate and high radon values are also noted. Recent studies of the datasets have revealed the extent of source rock (i.e. bedrock) flux attenuation by soil moisture in conjunction with the density and porosity of the temperate latitude soils found in the UK. The presence or absence of soil cover (and associated presence or absence of attenuation) appears to account for a range of localised variations in the exposure levels encountered. The hypothesis is supported by a study of an extensive combined data set of dose rates obtained from soil sampling and by airborne geophysical survey. With no attenuation factors applied, except those intrinsic to the airborne estimates, a bias to high values of between 10 and 15 nGy h(-1) is observed in the soil data. A wide range of technologically enhanced, localised contributions to dose rate values are also apparent in the data sets. Two detailed examples are provided that reveal the detectability of site-scale environmental impacts due to former industrial activities and the high dose values (>500 nGy h(-1)) that are associated with former, small-scale Uranium mining operations. Copyright © 2014. Published by Elsevier Ltd.

SU-C-16A-02: A Beryllium Oxide (BeO) Fibre-Coupled Luminescence Dosimeter for High Dose Rate Brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santos, A; Institute for Photonics and Advanced Sensing and School of Chem and Phys, Adelaide, South Australia; Mohammadi, M

Purpose: Beryllium oxide (BeO) ceramics have an effective atomic number, zeff ∼7.1, closely matched to water, zeff ∼7.4. The purpose of this study was to evaluate the use of a beryllium oxide (BeO) ceramic fibrecoupled luminescence dosimeter, named RL/OSL BeO FOD, for high dose rate (HDR) brachytherapy dosimetry. In our dosimetry system the radioluminescence (RL) of BeO ceramics is utilized for dose-rate measurements, and the optically stimulated luminescence (OSL) can be read post exposure for accumulated dose measurements. Methods: The RL/OSL BeO FOD consists of a 1 mm diameter × 1 mm long cylinder of BeO ceramic coupled to amore » 15 m long silica-silica optical fibre. The optical fibre is connected to a custom developed portable RL and OSL reader, located outside of the treatment suite. The x-ray energy response was evaluated using superficial x-rays, an Ir-192 source and high energy linear accelerators. The RL/OSL BeO FOD was then characterised for an Ir-192 source, investigating the dose response and angular dependency. A depth dose curve for the Ir-192 source was also measured. Results: The RL/OSL BeO FOD shows an under-response at low energy x-rays as expected. Though at higher x-ray energies, the OSL response continued to increase, while the RL response remained relatively constant. The dose response for the RL is found to be linear up to doses of 15 Gy, while the OSL response becomes more supralinear to doses above 15 Gy. Little angular dependency is observed and the depth dose curve measured agreed within 4% of that calculated based on TG-43. Conclusion: This works shows that the RL/OSL BeO FOD can be useful in HDR dosimetry. With the RL/OSL BeO FODs current size, it is capable of being inserted into intraluminal catheters and interstitial needles to verify HDR treatments.« less

GEANT4 and PHITS simulations of the shielding of neutrons from the 252Cf source

NASA Astrophysics Data System (ADS)

Shin, Jae Won; Hong, Seung-Woo; Bak, Sang-In; Kim, Do Yoon; Kim, Chong Yeal

2014-09-01

Monte Carlo simulations are performed by using the GEANT4 and the PHITS for studying the neutron-shielding abilities of several materials, such as graphite, iron, polyethylene, NS-4-FR and KRAFTON-HB. As a neutron source, 252Cf is considered. For the Monte Carlo simulations by using the GEANT4, high precision (G4HP) models with the G4NDL 4.2 based on ENDF/B-VII data are used. For the simulations by using the PHITS, the JENDL-4.0 library is used. The neutron-dose-equivalent rates with or without five different shielding materials are estimated and compared with the experimental values. The differences between the shielding abilities calculated by using the GEANT4 with the G4NDL 4.2 and the PHITS with the JENDL-4.0 are found not to be significant for all the cases considered in this work. The neutron-dose-equivalent rates obtained by using the GEANT4 and the PHITS are compared with experimental data and other simulation results. Our neutron-dose-equivalent rates agree well with the experimental dose-equivalent rates, within 20% errors, except for polyethylene. For polyethylene, the discrepancies between our calculations and the experiments are less than 40%, as observed in other simulation results.

Assessment of radiation shield integrity of DD/DT fusion neutron generator facilities by Monte Carlo and experimental methods

NASA Astrophysics Data System (ADS)

Srinivasan, P.; Priya, S.; Patel, Tarun; Gopalakrishnan, R. K.; Sharma, D. N.

2015-01-01

DD/DT fusion neutron generators are used as sources of 2.5 MeV/14.1 MeV neutrons in experimental laboratories for various applications. Detailed knowledge of the radiation dose rates around the neutron generators are essential for ensuring radiological protection of the personnel involved with the operation. This work describes the experimental and Monte Carlo studies carried out in the Purnima Neutron Generator facility of the Bhabha Atomic Research Center (BARC), Mumbai. Verification and validation of the shielding adequacy was carried out by measuring the neutron and gamma dose-rates at various locations inside and outside the neutron generator hall during different operational conditions both for 2.5-MeV and 14.1-MeV neutrons and comparing with theoretical simulations. The calculated and experimental dose rates were found to agree with a maximum deviation of 20% at certain locations. This study has served in benchmarking the Monte Carlo simulation methods adopted for shield design of such facilities. This has also helped in augmenting the existing shield thickness to reduce the neutron and associated gamma dose rates for radiological protection of personnel during operation of the generators at higher source neutron yields up to 1 × 1010 n/s.

In vivo TLD dose measurements in catheter-based high-dose-rate brachytherapy.

PubMed

Adlienė, Diana; Jakštas, Karolis; Urbonavičius, Benas Gabrielis

2015-07-01

Routine in vivo dosimetry is well established in external beam radiotherapy; however, it is restricted mainly to detection of gross errors in high-dose-rate (HDR) brachytherapy due to complicated measurements in the field of steep dose gradients in the vicinity of radioactive source and high uncertainties. The results of in vivo dose measurements using TLD 100 mini rods and TLD 'pin worms' in catheter-based HDR brachytherapy are provided in this paper alongside with their comparison with corresponding dose values obtained using calculation algorithm of the treatment planning system. Possibility to perform independent verification of treatment delivery in HDR brachytherapy using TLDs is discussed. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Dosimetry of 192Ir sources used for endovascular brachytherapy

NASA Astrophysics Data System (ADS)

Reynaert, N.; Van Eijkeren, M.; Taeymans, Y.; Thierens, H.

2001-02-01

An in-phantom calibration technique for 192Ir sources used for endovascular brachytherapy is presented. Three different source lengths were investigated. The calibration was performed in a solid phantom using a Farmer-type ionization chamber at source to detector distances ranging from 1 cm to 5 cm. The dosimetry protocol for medium-energy x-rays extended with a volume-averaging correction factor was used to convert the chamber reading to dose to water. The air kerma strength of the sources was determined as well. EGS4 Monte Carlo calculations were performed to determine the depth dose distribution at distances ranging from 0.6 mm to 10 cm from the source centre. In this way we were able to convert the absolute dose rate at 1 cm distance to the reference point chosen at 2 mm distance. The Monte Carlo results were confirmed by radiochromic film measurements, performed with a double-exposure technique. The dwell times to deliver a dose of 14 Gy at the reference point were determined and compared with results given by the source supplier (CORDIS). They determined the dwell times from a Sievert integration technique based on the source activity. The results from both methods agreed to within 2% for the 12 sources that were evaluated. A Visual Basic routine that superimposes dose distributions, based on the Monte Carlo calculations and the in-phantom calibration, onto intravascular ultrasound images is presented. This routine can be used as an online treatment planning program.

The Bebig Valencia-type skin applicators: Dosimetric study and implementation of a dosimetric hybrid technique.

PubMed

Anagnostopoulos, Georgios; Andrássy, Michael; Baltas, Dimos

To determine the relative dose rate distribution in water for the Bebig 20 mm and 30 mm skin applicators and report results in a form suitable for potential clinical use. Results for both skin applicators are also provided in the form of a hybrid Task Group 43 (TG-43) dosimetry technique. Furthermore, the radiation leakage around both skin applicators from the radiation protection point of view and the impact of the geometrical source position uncertainties are studied and reported. Monte Carlo simulations were performed using the MCNP 6.1 general purpose code, which was benchmarked against published dosimetry data for the Bebig Ir2.A85-2 high-dose-rate iridium-192 source, as well as the dosimetry data for the two Elekta skin applicators. Both Bebig skin applicators were modeled, and the dose rate distributions in a water phantom were calculated. The dosimetric quantities derived according to a hybrid TG-43 dosimetry technique are provided with their corresponding uncertainty values. The air kerma rate in air was simulated in the vicinity of each skin applicator to assess the radiation leakage. Results from the Monte Carlo simulations of both skin applicators are presented in the form of figures and relative dose rate tables, and additionally with the aid of the quantities defined in the hybrid TG-43 dosimetry technique and their corresponding uncertainty values. Their output factors, flatness, and penumbra values were found comparable to the Elekta skin applicators. The radiation shielding was evaluated to be adequate. The effect of potential uncertainties in source positioning on dosimetry should be investigated as part of applicator commissioning. Copyright © 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

Ir-192 HDR transit dose and radial dose function determination using alanine/EPR dosimetry

NASA Astrophysics Data System (ADS)

Guzmán Calcina, Carmen S.; de Almeida, Adelaide; Oliveira Rocha, José R.; Abrego, Felipe Chen; Baffa, Oswaldo

2005-03-01

Source positioning close to the tumour in high dose rate (HDR) brachytherapy is not instantaneous. An increment of dose will be delivered during the movement of the source in the trajectory to its static position. This increment is the transit dose, often not taken into account in brachytherapeutic treatment planning. The transit dose depends on the prescribed dose, number of treatment fractions, velocity and activity of the source. Combining all these factors, the transit dose can be 5% higher than the prescribed absorbed dose value (Sang-Hyun and Muller-Runkel, 1994 Phys. Med. Biol. 39 1181 8, Nath et al 1995 Med. Phys. 22 209 34). However, it cannot exceed this percentage (Nath et al 1995). In this work, we use the alanine-EPR (electron paramagnetic resonance) dosimetric system using analysis of the first derivative of the signal. The transit dose was evaluated for an HDR system and is consistent with that already presented for TLD dosimeters (Bastin et al 1993 Int. J. Radiat. Oncol. Biol. Phys. 26 695 702). Also using the same dosimetric system, the radial dose function, used to evaluate the geometric dose degradation around the source, was determined and its behaviour agrees better with those obtained by Monte Carlo simulations (Nath et al 1995, Williamson and Nath 1991 Med. Phys. 18 434 48, Ballester et al 1997 Med. Phys. 24 1221 8, Ballester et al 2001 Phys. Med. Biol. 46 N79 90) than with TLD measurements (Nath et al 1990 Med. Phys. 17 1032 40).

Ir-192 HDR transit dose and radial dose function determination using alanine/EPR dosimetry.

PubMed

Calcina, Carmen S Guzmán; de Almeida, Adelaide; Rocha, José R Oliveira; Abrego, Felipe Chen; Baffa, Oswaldo

2005-03-21

Source positioning close to the tumour in high dose rate (HDR) brachytherapy is not instantaneous. An increment of dose will be delivered during the movement of the source in the trajectory to its static position. This increment is the transit dose, often not taken into account in brachytherapeutic treatment planning. The transit dose depends on the prescribed dose, number of treatment fractions, velocity and activity of the source. Combining all these factors, the transit dose can be 5% higher than the prescribed absorbed dose value (Sang-Hyun and Muller-Runkel, 1994 Phys. Med. Biol. 39 1181-8, Nath et al 1995 Med. Phys. 22 209-34). However, it cannot exceed this percentage (Nath et al 1995). In this work, we use the alanine-EPR (electron paramagnetic resonance) dosimetric system using analysis of the first derivative of the signal. The transit dose was evaluated for an HDR system and is consistent with that already presented for TLD dosimeters (Bastin et al 1993 Int. J. Radiat. Oncol. Biol. Phys. 26 695-702). Also using the same dosimetric system, the radial dose function, used to evaluate the geometric dose degradation around the source, was determined and its behaviour agrees better with those obtained by Monte Carlo simulations (Nath et al 1995, Williamson and Nath 1991 Med. Phys. 18 434-48, Ballester et al 1997 Med. Phys. 24 1221-8, Ballester et al 2001 Phys. Med. Biol. 46 N79-90) than with TLD measurements (Nath et al 1990 Med. Phys. 17 1032-40).

Dose rate effects in radiation degradation of polymer-based cable materials

NASA Astrophysics Data System (ADS)

Plaček, V.; Bartoníček, B.; Hnát, V.; Otáhal, B.

2003-08-01

Cable ageing under the nuclear power plant (NPP) conditions must be effectively managed to ensure that the required plant safety and reliability are maintained throughout the plant service life. Ionizing radiation is one of the main stressors causing age-related degradation of polymer-based cable materials in air. For a given absorbed dose, radiation-induced damage to a polymer in air environment usually depends on the dose rate of the exposure. In this work, the effect of dose rate on the degradation rate has been studied. Three types of NPP cables (with jacket/insulation combinations PVC/PVC, PVC/PE, XPE/XPE) were irradiated at room temperature using 60Co gamma ray source at average dose rates of 7, 30 and 100 Gy/h with the doses up to 590 kGy. The irradiated samples have been tested for their mechanical properties, thermo-oxidative stability (using differential scanning calorimetry, DSC), and density. In the case of PVC and PE samples, the tested properties have shown evident dose rate effects, while the XPE material has shown no noticeable ones. The values of elongation at break and the thermo-oxidative stability decrease with the advanced degradation, density tends to increase with the absorbed dose. For XPE samples this effect can be partially explained by the increase of crystallinity. It was tested by the DSC determination of the crystalline phase amount.

Radiological Monitoring for Instructors. Student Workbook. Revised.

ERIC Educational Resources Information Center

Office of Civil Defense (DOD), Washington, DC.

This student workbook includes the necessary materials and some of the references needed by each student during the conduct of the Radiological Monitoring for Instructors (RMI) course. The contents include a radiation exposure record, instrument exercise materials, fallout forecasting problems, dose and dose rate problems, source handling…

Dose rate prediction methodology for remote handled transuranic waste workers at the waste isolation pilot plant.

PubMed

Hayes, Robert

2002-10-01

An approach is described for estimating future dose rates to Waste Isolation Pilot Plant workers processing remote handled transuranic waste. The waste streams will come from the entire U.S. Department of Energy complex and can take on virtually any form found from the processing sequences for defense-related production, radiochemistry, activation and related work. For this reason, the average waste matrix from all generator sites is used to estimate the average radiation fields over the facility lifetime. Innovative new techniques were applied to estimate expected radiation fields. Non-linear curve fitting techniques were used to predict exposure rate profiles from cylindrical sources using closed form equations for lines and disks. This information becomes the basis for Safety Analysis Report dose rate estimates and for present and future ALARA design reviews when attempts are made to reduce worker doses.

Effects of γ ray irradiation on Vibrio Qinghaiensis sp. Q67

NASA Astrophysics Data System (ADS)

Wei, Yan; Linping, Kuai

2017-12-01

In order to investigate the luminous responses of γ ray irradiation on Vibrio Qinghaiensis sp. Q67, two γ ray sources, 60Co and 137Cs, were used. Following the dose rates between 0.05Gy/min and 0.2Gy/min of 60Co, the relative luminous value (RLV ) of Q67 was less than 1 after 5 minutes irradiation and inversely related to dose rate. Irradiated 1 hour at dose rates range from 100nGy/h to 10mGy/h of 137Cs, two successive stages in the luminous response were found: hormesis and inhibition. It was found that RLV was interleaved and could not be distinguished until inhibition stage appearance. The time when RLV drops to less than 1 (T0 ) was linear with the logarithm of dose rate. Experimental result indicates that Q67 is sensitive to acute γray radiation, which could be used to monitor γray radiation.

Intraluminal low-dose-rate 192Ir brachytherapy combined with external beam radiotherapy and biliary stenting for unresectable extrahepatic bile duct carcinoma.

PubMed

Takamura, Akio; Saito, Hiroya; Kamada, Tadashi; Hiramatsu, Kazuhide; Takeuchi, Shuhei; Hasegawa, Masakazu; Miyamoto, Noriyuki

2003-12-01

To evaluate the results of combined-modality therapy, including external beam radiotherapy, intraluminal (192)Ir, and biliary stenting for extrahepatic bile duct carcinoma. Between 1988 and 1998, 93 patients with unresectable extrahepatic bile duct carcinoma underwent definitive radiotherapy. The dose of external beam radiotherapy was 50 Gy in 25 fractions. Low-dose-rate (192)Ir was delivered at a dose of 27-50 Gy (mean 39.2) at 0.5 cm from the source. An expandable metallic endoprosthesis was used to establish an internal bile passage. The median survival was 12 months, with a 1-, 3-, and 5-year actuarial survival rate of 50%, 10%, and 4%, respectively. Tumor length, hepatic invasion, and distant metastasis significantly affected survival. Ninety-six percent of patients could successfully remove external drainage catheters. The actuarial biliary patency rate for these patients at 1, 3, and 5 years was 52%, 29%, and 18%, respectively. Tumor length, tumor diameter and T stage were significantly associated with the patency rate. Mild-to-severe gastroduodenal complications were observed in 32 patients and were significantly associated with the active length of (192)Ir and linear source activity. Eight patients had treatment-related biliary fistula. Our combined-modality therapy provided reasonable local control and improved the quality of life of patients with extrahepatic bile duct carcinoma. Because none of the treatment characteristics had any impact on survival or biliary patency, lower dose levels and/or a localized target volume are recommended to minimize morbidity.

Computational study of radiation doses at UNLV accelerator facility

NASA Astrophysics Data System (ADS)

Hodges, Matthew; Barzilov, Alexander; Chen, Yi-Tung; Lowe, Daniel

2017-09-01

A Varian K15 electron linear accelerator (linac) has been considered for installation at University of Nevada, Las Vegas (UNLV). Before experiments can be performed, it is necessary to evaluate the photon and neutron spectra as generated by the linac, as well as the resulting dose rates within the accelerator facility. A computational study using MCNPX was performed to characterize the source terms for the bremsstrahlung converter. The 15 MeV electron beam available in the linac is above the photoneutron threshold energy for several materials in the linac assembly, and as a result, neutrons must be accounted for. The angular and energy distributions for bremsstrahlung flux generated by the interaction of the 15 MeV electron beam with the linac target were determined. This source term was used in conjunction with the K15 collimators to determine the dose rates within the facility.

Qualification tests for {sup 192}Ir sealed sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iancso, Georgeta, E-mail: georgetaiancso@yahoo.com; Iliescu, Elena, E-mail: georgetaiancso@yahoo.com; Iancu, Rodica, E-mail: georgetaiancso@yahoo.com

This paper describes the results of qualification tests for {sup 192}Ir sealed sources, available in Testing and Nuclear Expertise Laboratory of National Institute for Physics and Nuclear Engineering 'Horia Hulubei' (I.F.I.N.-HH), Romania. These sources had to be produced in I.F.I.N.-HH and were tested in order to obtain the authorization from The National Commission for Nuclear Activities Control (CNCAN). The sources are used for gammagraphy procedures or in gammadefectoscopy equipments. Tests, measurement methods and equipments used, comply with CNCAN, AIEA and International Quality Standards and regulations. The qualification tests are: 1. Radiological tests and measurements: dose equivalent rate at 1 m;more » tightness; dose equivalent rate at the surface of the transport and storage container; external unfixed contamination of the container surface. 2. Mechanical and climatic tests: thermal shock; external pressure; mechanic shock; vibrations; boring; thermal conditions for storage and transportation. Passing all tests, it was obtained the Radiological Security Authorization for producing the {sup 192}Ir sealed sources. Now IFIN-HH can meet many demands for this sealed sources, as the only manufacturer in Romania.« less

Analysis of neutron and gamma-ray streaming along the maze of NRCAM thallium production target room.

PubMed

Raisali, G; Hajiloo, N; Hamidi, S; Aslani, G

2006-08-01

Study of the shield performance of a thallium-203 production target room has been investigated in this work. Neutron and gamma-ray equivalent dose rates at various points of the maze are calculated by simulating the transport of streaming neutrons, and photons using Monte Carlo method. For determination of neutron and gamma-ray source intensities and their energy spectrum, we have applied SRIM 2003 and ALICE91 computer codes to Tl target and its Cu substrate for a 145 microA of 28.5 MeV protons beam. The MCNP/4C code has been applied with neutron source term in mode n p to consider both prompt neutrons and secondary gamma-rays. Then the code is applied for the prompt gamma-rays as the source term. The neutron-flux energy spectrum and equivalent dose rates for neutron and gamma-rays in various positions in the maze have been calculated. It has been found that the deviation between calculated and measured dose values along the maze is less than 20%.

A photon source model based on particle transport in a parameterized accelerator structure for Monte Carlo dose calculations.

PubMed

Ishizawa, Yoshiki; Dobashi, Suguru; Kadoya, Noriyuki; Ito, Kengo; Chiba, Takahito; Takayama, Yoshiki; Sato, Kiyokazu; Takeda, Ken

2018-05-17

An accurate source model of a medical linear accelerator is essential for Monte Carlo (MC) dose calculations. This study aims to propose an analytical photon source model based on particle transport in parameterized accelerator structures, focusing on a more realistic determination of linac photon spectra compared to existing approaches. We designed the primary and secondary photon sources based on the photons attenuated and scattered by a parameterized flattening filter. The primary photons were derived by attenuating bremsstrahlung photons based on the path length in the filter. Conversely, the secondary photons were derived from the decrement of the primary photons in the attenuation process. This design facilitates these sources to share the free parameters of the filter shape and be related to each other through the photon interaction in the filter. We introduced two other parameters of the primary photon source to describe the particle fluence in penumbral regions. All the parameters are optimized based on calculated dose curves in water using the pencil-beam-based algorithm. To verify the modeling accuracy, we compared the proposed model with the phase space data (PSD) of the Varian TrueBeam 6 and 15 MV accelerators in terms of the beam characteristics and the dose distributions. The EGS5 Monte Carlo code was used to calculate the dose distributions associated with the optimized model and reference PSD in a homogeneous water phantom and a heterogeneous lung phantom. We calculated the percentage of points passing 1D and 2D gamma analysis with 1%/1 mm criteria for the dose curves and lateral dose distributions, respectively. The optimized model accurately reproduced the spectral curves of the reference PSD both on- and off-axis. The depth dose and lateral dose profiles of the optimized model also showed good agreement with those of the reference PSD. The passing rates of the 1D gamma analysis with 1%/1 mm criteria between the model and PSD were 100% for 4 × 4, 10 × 10, and 20 × 20 cm 2 fields at multiple depths. For the 2D dose distributions calculated in the heterogeneous lung phantom, the 2D gamma pass rate was 100% for 6 and 15 MV beams. The model optimization time was less than 4 min. The proposed source model optimization process accurately produces photon fluence spectra from a linac using valid physical properties, without detailed knowledge of the geometry of the linac head, and with minimal optimization time. © 2018 American Association of Physicists in Medicine.

Patient-specific Monte Carlo-based dose-kernel approach for inverse planning in afterloading brachytherapy.

PubMed

D'Amours, Michel; Pouliot, Jean; Dagnault, Anne; Verhaegen, Frank; Beaulieu, Luc

2011-12-01

Brachytherapy planning software relies on the Task Group report 43 dosimetry formalism. This formalism, based on a water approximation, neglects various heterogeneous materials present during treatment. Various studies have suggested that these heterogeneities should be taken into account to improve the treatment quality. The present study sought to demonstrate the feasibility of incorporating Monte Carlo (MC) dosimetry within an inverse planning algorithm to improve the dose conformity and increase the treatment quality. The method was based on precalculated dose kernels in full patient geometries, representing the dose distribution of a brachytherapy source at a single dwell position using MC simulations and the Geant4 toolkit. These dose kernels are used by the inverse planning by simulated annealing tool to produce a fast MC-based plan. A test was performed for an interstitial brachytherapy breast treatment using two different high-dose-rate brachytherapy sources: the microSelectron iridium-192 source and the electronic brachytherapy source Axxent operating at 50 kVp. A research version of the inverse planning by simulated annealing algorithm was combined with MC to provide a method to fully account for the heterogeneities in dose optimization, using the MC method. The effect of the water approximation was found to depend on photon energy, with greater dose attenuation for the lower energies of the Axxent source compared with iridium-192. For the latter, an underdosage of 5.1% for the dose received by 90% of the clinical target volume was found. A new method to optimize afterloading brachytherapy plans that uses MC dosimetric information was developed. Including computed tomography-based information in MC dosimetry in the inverse planning process was shown to take into account the full range of scatter and heterogeneity conditions. This led to significant dose differences compared with the Task Group report 43 approach for the Axxent source. Copyright © 2011 Elsevier Inc. All rights reserved.

Assessing exposure to granite countertops--Part 1: Radiation.

PubMed

Myatt, Theodore A; Allen, Joseph G; Minegishi, Taeko; McCarthy, William B; Stewart, James H; Macintosh, David L; McCarthy, John F

2010-05-01

Humans are continuously exposed to low levels of ionizing radiation. Known sources include radon, soil, cosmic rays, medical treatment, food, and building products such as gypsum board and concrete. Little information exists about radiation emissions and associated doses from natural stone finish materials such as granite countertops in homes. To address this knowledge gap, gross radioactivity, gamma ray activity, and dose rate were determined for slabs of granite marketed for use as countertops. Annual effective radiation doses were estimated from measured dose rates and human activity patterns while accounting for the geometry of granite countertops in a model kitchen. Gross radioactivity, gamma activity, and dose rate varied significantly among and within slabs of granite with ranges for median levels at the slab surface of ND to 3000 cpm, ND to 98,000 cpm, and ND to 1.5E-4 mSv/h, respectively. The maximum activity concentrations of the (40)K, (232)Th, and (226)Ra series were 2715, 231, and 450 Bq/kg, respectively. The estimated annual radiation dose from spending 4 h/day in a hypothetical kitchen ranged from 0.005 to 0.18 mSv/a depending on the type of granite. In summary, our results show that the types of granite characterized in this study contain varying levels of radioactive isotopes and that their observed emissions are consistent with those reported in the scientific literature. We also conclude from our analyses that these emissions are likely to be a minor source of external radiation dose when used as countertop material within the home and present a negligible risk to human health.

Performance of turbo high-pitch dual-source CT for coronary CT angiography: first ex vivo and patient experience.

PubMed

Morsbach, Fabian; Gordic, Sonja; Desbiolles, Lotus; Husarik, Daniela; Frauenfelder, Thomas; Schmidt, Bernhard; Allmendinger, Thomas; Wildermuth, Simon; Alkadhi, Hatem; Leschka, Sebastian

2014-08-01

To evaluate image quality, maximal heart rate allowing for diagnostic imaging, and radiation dose of turbo high-pitch dual-source coronary computed tomographic angiography (CCTA). First, a cardiac motion phantom simulating heart rates (HRs) from 60-90 bpm in 5-bpm steps was examined on a third-generation dual-source 192-slice CT (prospective ECG-triggering, pitch 3.2; rotation time, 250 ms). Subjective image quality regarding the presence of motion artefacts was interpreted by two readers on a four-point scale (1, excellent; 4, non-diagnostic). Objective image quality was assessed by calculating distortion vectors. Thereafter, 20 consecutive patients (median, 50 years) undergoing clinically indicated CCTA were included. In the phantom study, image quality was rated diagnostic up to the HR75 bpm, with object distortion being 1 mm or less. Distortion increased above 1 mm at HR of 80-90 bpm. Patients had a mean HR of 66 bpm (47-78 bpm). Coronary segments were of diagnostic image quality for all patients with HR up to 73 bpm. Average effective radiation dose in patients was 0.6 ± 0.3 mSv. Our combined phantom and patient study indicates that CCTA with turbo high-pitch third-generation dual-source 192-slice CT can be performed at HR up to 75 bpm while maintaining diagnostic image quality, being associated with an average radiation dose of 0.6 mSv. • CCTA is feasible with the turbo high-pitch mode. • Turbo high-pitch CCTA provides diagnostic image quality up to 73 bpm. • The radiation dose of high-pitch CCTA is 0.6 mSv on average.

The use of new GAFCHROMIC EBT film for 125I seed dosimetry in Solid Water phantom.

PubMed

Chiu-Tsao, Sou-Tung; Medich, David; Munro, John

2008-08-01

Radiochromic film dosimetry has been extensively used for intravascular brachytherapy applications for near field within 1 cm from the sources. With the recent introduction of new model of radiochromic films, GAFCHROMIC EBT, with higher sensitivity than earlier models, it is promising to extend the distances out to 5 cm for low dose rate (LDR) source dosimetry. In this study, the use of new model GAFCHROMIC EBT film for 125I seed dosimetry in Solid Water was evaluated for radial distances from 0.06 cm out to 5 cm. A multiple film technique was employed for four 125I seeds (Implant Sciences model 3500) with NIST traceable air kerma strengths. Each experimental film was positioned in contact with a 125I seed in a Solid Water phantom. The products of the air kerma strength and exposure time ranged from 8 to 3158 U-h, with the initial air kerma strength of 6 U in a series of 25 experiments. A set of 25 calibration films each was sequentially exposed to one 125I seed at about 0.58 cm distance for doses from 0.1 to 33 Gy. A CCD camera based microdensitometer, with interchangeable green (520 nm) and red (665 nm) light boxes, was used to scan all the films with 0.2 mm pixel resolution. The dose to each 125I calibration film center was calculated using the air kerma strength of the seed (incorporating decay), exposure time, distance from seed center to film center, and TG43U1S1 recommended dosimetric parameters. Based on the established calibration curve, dose conversion from net optical density was achieved for each light source. The dose rate constant was determined as 0.991 cGy U(-1)h(-1) (+/-6.9%) and 1.014 cGy U(-1)h(-1) (+/-6.8%) from films scanned using green and red light sources, respectively. The difference between these two values was within the uncertainty of the measurement. Radial dose function and 2D anisotropy function were also determined. The results obtained using the two light sources corroborated each other. We found good agreement with the TG43U1S1 recommended values of radial dose function and 2D anisotropy function, to within the uncertainty of the measurement. We also verified the dosimetric parameters in the near field calculated by Rivard using Monte Carlo method. The radial dose function values in Solid Water were lower than those in water recommended by TG43U1S1, by about 2%, 3%, 7%, and 14% at 2, 3, 4, and 5 cm, respectively, partially due to the difference in the phantom material composition. Radiochromic film dosimetry using GAFCHROMIC EBT model is feasible in determining 2D dose distributions around low dose rate 125I seed. It is a viable alternative to TLD dosimetry for 125I seed dose characterization.

Optimal mapping of terrestrial gamma dose rates using geological parent material and aerogeophysical survey data.

PubMed

Rawlins, B G; Scheib, C; Tyler, A N; Beamish, D

2012-12-01

Regulatory authorities need ways to estimate natural terrestrial gamma radiation dose rates (nGy h⁻¹) across the landscape accurately, to assess its potential deleterious health effects. The primary method for estimating outdoor dose rate is to use an in situ detector supported 1 m above the ground, but such measurements are costly and cannot capture the landscape-scale variation in dose rates which are associated with changes in soil and parent material mineralogy. We investigate the potential for improving estimates of terrestrial gamma dose rates across Northern Ireland (13,542 km²) using measurements from 168 sites and two sources of ancillary data: (i) a map based on a simplified classification of soil parent material, and (ii) dose estimates from a national-scale, airborne radiometric survey. We used the linear mixed modelling framework in which the two ancillary variables were included in separate models as fixed effects, plus a correlation structure which captures the spatially correlated variance component. We used a cross-validation procedure to determine the magnitude of the prediction errors for the different models. We removed a random subset of 10 terrestrial measurements and formed the model from the remainder (n = 158), and then used the model to predict values at the other 10 sites. We repeated this procedure 50 times. The measurements of terrestrial dose vary between 1 and 103 (nGy h⁻¹). The median absolute model prediction errors (nGy h⁻¹) for the three models declined in the following order: no ancillary data (10.8) > simple geological classification (8.3) > airborne radiometric dose (5.4) as a single fixed effect. Estimates of airborne radiometric gamma dose rate can significantly improve the spatial prediction of terrestrial dose rate.

SU-C-BRC-04: Efficient Dose Calculation Algorithm for FFF IMRT with a Simplified Bivariate Gaussian Source Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, F; Park, J; Barraclough, B

2016-06-15

Purpose: To develop an efficient and accurate independent dose calculation algorithm with a simplified analytical source model for the quality assurance and safe delivery of Flattening Filter Free (FFF)-IMRT on an Elekta Versa HD. Methods: The source model consisted of a point source and a 2D bivariate Gaussian source, respectively modeling the primary photons and the combined effect of head scatter, monitor chamber backscatter and collimator exchange effect. The in-air fluence was firstly calculated by back-projecting the edges of beam defining devices onto the source plane and integrating the visible source distribution. The effect of the rounded MLC leaf end,more » tongue-and-groove and interleaf transmission was taken into account in the back-projection. The in-air fluence was then modified with a fourth degree polynomial modeling the cone-shaped dose distribution of FFF beams. Planar dose distribution was obtained by convolving the in-air fluence with a dose deposition kernel (DDK) consisting of the sum of three 2D Gaussian functions. The parameters of the source model and the DDK were commissioned using measured in-air output factors (Sc) and cross beam profiles, respectively. A novel method was used to eliminate the volume averaging effect of ion chambers in determining the DDK. Planar dose distributions of five head-and-neck FFF-IMRT plans were calculated and compared against measurements performed with a 2D diode array (MapCHECK™) to validate the accuracy of the algorithm. Results: The proposed source model predicted Sc for both 6MV and 10MV with an accuracy better than 0.1%. With a stringent gamma criterion (2%/2mm/local difference), the passing rate of the FFF-IMRT dose calculation was 97.2±2.6%. Conclusion: The removal of the flattening filter represents a simplification of the head structure which allows the use of a simpler source model for very accurate dose calculation. The proposed algorithm offers an effective way to ensure the safe delivery of FFF-IMRT.« less

Comparative analysis of dose rates in bricks determined by neutron activation analysis, alpha counting and X-ray fluorescence analysis for the thermoluminescence fine grain dating method

NASA Astrophysics Data System (ADS)

Bártová, H.; Kučera, J.; Musílek, L.; Trojek, T.

2014-11-01

In order to evaluate the age from the equivalent dose and to obtain an optimized and efficient procedure for thermoluminescence (TL) dating, it is necessary to obtain the values of both the internal and the external dose rates from dated samples and from their environment. The measurements described and compared in this paper refer to bricks from historic buildings and a fine-grain dating method. The external doses are therefore negligible, if the samples are taken from a sufficient depth in the wall. However, both the alpha dose rate and the beta and gamma dose rates must be taken into account in the internal dose. The internal dose rate to fine-grain samples is caused by the concentrations of natural radionuclides 238U, 235U, 232Th and members of their decay chains, and by 40K concentrations. Various methods can be used for determining trace concentrations of these natural radionuclides and their contributions to the dose rate. The dose rate fraction from 238U and 232Th can be calculated, e.g., from the alpha count rate, or from the concentrations of 238U and 232Th, measured by neutron activation analysis (NAA). The dose rate fraction from 40K can be calculated from the concentration of potassium measured, e.g., by X-ray fluorescence analysis (XRF) or by NAA. Alpha counting and XRF are relatively simple and are accessible for an ordinary laboratory. NAA can be considered as a more accurate method, but it is more demanding regarding time and costs, since it needs a nuclear reactor as a neutron source. A comparison of these methods allows us to decide whether the time- and cost-saving simpler techniques introduce uncertainty that is still acceptable.

Calibration factors for the SNOOPY NP-100 neutron dosimeter

NASA Astrophysics Data System (ADS)

Moscu, D. F.; McNeill, F. E.; Chase, J.

2007-10-01

Within CANDU nuclear power facilities, only a small fraction of workers are exposed to neutron radiation. For these individuals, roughly 4.5% of the total radiation equivalent dose is the result of exposure to neutrons. When this figure is considered across all workers receiving external exposure of any kind, only 0.25% of the total radiation equivalent dose is the result of exposure to neutrons. At many facilities, the NP-100 neutron dosimeter, manufactured by Canberra Industries Incorporated, is employed in both direct and indirect dosimetry methods. Also known as "SNOOPY", these detectors undergo calibration, which results in a calibration factor relating the neutron count rate to the ambient dose equivalent rate, using a standard Am-Be neutron source. Using measurements presented in a technical note, readings from the dosimeter for six different neutron fields in six source-detector orientations were used, to determine a calibration factor for each of these sources. The calibration factor depends on the neutron energy spectrum and the radiation weighting factor to link neutron fluence to equivalent dose. Although the neutron energy spectra measured in the CANDU workplace are quite different than that of the Am-Be calibration source, the calibration factor remains constant - within acceptable limits - regardless of the neutron source used in the calibration; for the specified calibration orientation and current radiation weighting factors. However, changing the value of the radiation weighting factors would result in changes to the calibration factor. In the event of changes to the radiation weighting factors, it will be necessary to assess whether a change to the calibration process or resulting calibration factor is warranted.

A revised dosimetric characterization of the model S700 electronic brachytherapy source containing an anode-centering plastic insert and other components not included in the 2006 model.

PubMed

Hiatt, Jessica R; Davis, Stephen D; Rivard, Mark J

2015-06-01

The model S700 Axxent electronic brachytherapy source by Xoft, Inc., was characterized by Rivard et al. in 2006. Since then, the source design was modified to include a new insert at the source tip. Current study objectives were to establish an accurate source model for simulation purposes, dosimetrically characterize the new source and obtain its TG-43 brachytherapy dosimetry parameters, and determine dose differences between the original simulation model and the current model S700 source design. Design information from measurements of dissected model S700 sources and from vendor-supplied CAD drawings was used to aid establishment of an updated Monte Carlo source model, which included the complex-shaped plastic source-centering insert intended to promote water flow for cooling the source anode. These data were used to create a model for subsequent radiation transport simulations in a water phantom. Compared to the 2006 simulation geometry, the influence of volume averaging close to the source was substantially reduced. A track-length estimator was used to evaluate collision kerma as a function of radial distance and polar angle for determination of TG-43 dosimetry parameters. Results for the 50 kV source were determined every 0.1 cm from 0.3 to 15 cm and every 1° from 0° to 180°. Photon spectra in water with 0.1 keV resolution were also obtained from 0.5 to 15 cm and polar angles from 0° to 165°. Simulations were run for 10(10) histories, resulting in statistical uncertainties on the transverse plane of 0.04% at r = 1 cm and 0.06% at r = 5 cm. The dose-rate distribution ratio for the model S700 source as compared to the 2006 model exceeded unity by more than 5% for roughly one quarter of the solid angle surrounding the source, i.e., θ ≥ 120°. The radial dose function diminished in a similar manner as for an (125)I seed, with values of 1.434, 0.636, 0.283, and 0.0975 at 0.5, 2, 5, and 10 cm, respectively. The radial dose function ratio between the current and the 2006 model had a minimum of 0.980 at 0.4 cm, close to the source sheath and for large distances approached 1.014. 2D anisotropy function ratios were close to unity for 50° ≤ θ ≤ 110°, but exceeded 5% for θ < 40° at close distances to the sheath and exceeded 15% for θ > 140°, even at large distances. Photon energy fluence of the updated model as compared to the 2006 model showed a decrease in output with increasing distance; this effect was pronounced at the lowest energies. A decrease in photon fluence with increase in polar angle was also observed and was attributed to the silver epoxy component. Changes in source design influenced the overall dose rate and distribution by more than 2% in several regions. This discrepancy is greater than the dose calculation acceptance criteria as recommended in the AAPM TG-56 report. The effect of the design change on the TG-43 parameters would likely not result in dose differences outside of patient applicators. Adoption of this new dataset is suggested for accurate depiction of model S700 source dose distributions.

A revised dosimetric characterization of the model S700 electronic brachytherapy source containing an anode-centering plastic insert and other components not included in the 2006 model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hiatt, Jessica R.; Davis, Stephen D.; Rivard, Mark J., E-mail: mark.j.rivard@gmail.com

2015-06-15

Purpose: The model S700 Axxent electronic brachytherapy source by Xoft, Inc., was characterized by Rivard et al. in 2006. Since then, the source design was modified to include a new insert at the source tip. Current study objectives were to establish an accurate source model for simulation purposes, dosimetrically characterize the new source and obtain its TG-43 brachytherapy dosimetry parameters, and determine dose differences between the original simulation model and the current model S700 source design. Methods: Design information from measurements of dissected model S700 sources and from vendor-supplied CAD drawings was used to aid establishment of an updated Montemore » Carlo source model, which included the complex-shaped plastic source-centering insert intended to promote water flow for cooling the source anode. These data were used to create a model for subsequent radiation transport simulations in a water phantom. Compared to the 2006 simulation geometry, the influence of volume averaging close to the source was substantially reduced. A track-length estimator was used to evaluate collision kerma as a function of radial distance and polar angle for determination of TG-43 dosimetry parameters. Results for the 50 kV source were determined every 0.1 cm from 0.3 to 15 cm and every 1° from 0° to 180°. Photon spectra in water with 0.1 keV resolution were also obtained from 0.5 to 15 cm and polar angles from 0° to 165°. Simulations were run for 10{sup 10} histories, resulting in statistical uncertainties on the transverse plane of 0.04% at r = 1 cm and 0.06% at r = 5 cm. Results: The dose-rate distribution ratio for the model S700 source as compared to the 2006 model exceeded unity by more than 5% for roughly one quarter of the solid angle surrounding the source, i.e., θ ≥ 120°. The radial dose function diminished in a similar manner as for an {sup 125}I seed, with values of 1.434, 0.636, 0.283, and 0.0975 at 0.5, 2, 5, and 10 cm, respectively. The radial dose function ratio between the current and the 2006 model had a minimum of 0.980 at 0.4 cm, close to the source sheath and for large distances approached 1.014. 2D anisotropy function ratios were close to unity for 50° ≤ θ ≤ 110°, but exceeded 5% for θ < 40° at close distances to the sheath and exceeded 15% for θ > 140°, even at large distances. Photon energy fluence of the updated model as compared to the 2006 model showed a decrease in output with increasing distance; this effect was pronounced at the lowest energies. A decrease in photon fluence with increase in polar angle was also observed and was attributed to the silver epoxy component. Conclusions: Changes in source design influenced the overall dose rate and distribution by more than 2% in several regions. This discrepancy is greater than the dose calculation acceptance criteria as recommended in the AAPM TG-56 report. The effect of the design change on the TG-43 parameters would likely not result in dose differences outside of patient applicators. Adoption of this new dataset is suggested for accurate depiction of model S700 source dose distributions.« less

Dismantling of Radium-226 Coal Level Gauges: Encountered Problems and How to Solve

DOE Office of Scientific and Technical Information (OSTI.GOV)

Punnachaiya, M.; Nuanjan, P.; Moombansao, K.

2006-07-01

This paper describes the techniques for dismantling of disused-sealed Radium-226 (Ra-226) coal level gauges which the source specifications and documents were not available, including problems occurred during dismantling stage and the decision making in solving all those obstacles. The 2 mCi (20 pieces), 6 mCi (20 pieces) and 6.6 mCi (30 pieces) of Ra-226 hemi-spherically-shaped with lead-filled coal level gauges were used in industrial applications for electric power generation. All sources needed to be dismantled for further conditioning as requested by the International Atomic Energy Agency (IAEA). One of the 2 mCi Ra-226 source was dismantled under the supervision ofmore » IAEA expert. Before conditioning period, each of the 6 mCi and 6.6 mCi sources were dismantled and inspected. It was found that coal level gauges had two different source types: the sealed cylindrical source (diameter 2 cm x 2 cm length) locked with spring in lead housing for 2 mCi and 6.6 mCi; while the 6 mCi was an embedded capsule inside source holder stud assembly in lead-filled housing. Dismantling Ra-226 coal level gauges comprised of 6 operational steps: confirmation of the surface dose rate on each source activity, calculation of working time within the effective occupational dose limit, cutting the weld of lead container by electrical blade, confirmation of the Ra-226 embedded capsule size using radiation scanning technique and gamma radiography, automatic sawing of the source holder stud assembly, and transferring the source to store in lead safe box. The embedded length of 6 mCi Ra-226 capsule in its diameter 2 cm x 14.7 cm length stud assembly was identified, the results from scanning technique and radiographic film revealed the embedded source length of about 2 cm, therefore all the 6 mCi sources were safely cut at 3 cm using the automatic saw. Another occurring problem was one of the 6.6 mCi spring type source stuck inside its housing because the spring was deformed and there was previously a leakage on inner source housing. Thus, during manufacturing the filled-lead for shielding passed through this small hole and fixed the deformed spring together with the source. The circular surface of inner hole was measured and slowly drilled at a diameter 2.2 cm behind shielding, till the spring and the fixed lead sheet were cut, therefore the source could be finally hammered out. The surface dose rate of coal level gauges before weld cutting was 10-15 mR/hr and the highest dose rate at the position of the weld cutter was 2.5 mR/hr. The total time for each weld cutting and automatic sawing was 2-3 minutes and 1 minute, respectively. The source was individually and safely transferred to store in lead safe box using a 1-meter length tong and a light container with 1 meter length handle. The total time for Ra-226 (70 pieces) dismantling, including the encountered problems and their troubles shooting took 4 days operation in which the total dose obtained by 18 operators were ranged from 1-38 {mu}Sv. The dismantling team safely completed the activities within the effective dose limit for occupational exposure of 20 mSv/year (80 {mu}Sv/day). (authors)« less

SU-F-T-32: Evaluation of the Performance of a Multiple-Array-Diode Detector for Quality Assurance Tests in High-Dose-Rate Brachytherapy with Ir-192 Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harpool, K; De La Fuente Herman, T; Ahmad, S

Purpose: To evaluate the performance of a two-dimensional (2D) array-diode- detector for geometric and dosimetric quality assurance (QA) tests of high-dose-rate (HDR) brachytherapy with an Ir-192-source. Methods: A phantom setup was designed that encapsulated a two-dimensional (2D) array-diode-detector (MapCheck2) and a catheter for the HDR brachytherapy Ir-192 source. This setup was used to perform both geometric and dosimetric quality assurance for the HDR-Ir192 source. The geometric tests included: (a) measurement of the position of the source and (b) spacing between different dwell positions. The dosimteric tests include: (a) linearity of output with time, (b) end effect and (c) relative dosemore » verification. The 2D-dose distribution measured with MapCheck2 was used to perform the previous tests. The results of MapCheck2 were compared with the corresponding quality assurance testes performed with Gafchromic-film and well-ionization-chamber. Results: The position of the source and the spacing between different dwell-positions were reproducible within 1 mm accuracy by measuring the position of maximal dose using MapCheck2 in contrast to the film which showed a blurred image of the dwell positions due to limited film sensitivity to irradiation. The linearity of the dose with dwell times measured from MapCheck2 was superior to the linearity measured with ionization chamber due to higher signal-to-noise ratio of the diode readings. MapCheck2 provided more accurate measurement of the end effect with uncertainty < 1.5% in comparison with the ionization chamber uncertainty of 3%. Although MapCheck2 did not provide absolute calibration dosimeter for the activity of the source, it provided accurate tool for relative dose verification in HDR-brachytherapy. Conclusion: The 2D-array-diode-detector provides a practical, compact and accurate tool to perform quality assurance for HDR-brachytherapy with an Ir-192 source. The diodes in MapCheck2 have high radiation sensitivity and linearity that is superior to Gafchromic-films and ionization chamber used for geometric and dosimetric QA in HDR-brachytherapy, respectively.« less

Radiation-Induced Gastrointestinal Death in the Monkey

DTIC Science & Technology

1959-06-01

muscularis mucosa FIGURE 9 could be identified in the histologic prep- One of the more severe cases of atrophic gastritis . arations. The bodies of the glands...sources into position and then was lowered rapidly The histologic preparations examined in this into the center of the field. The dose rate was 803 r...tributed over a spherical wire fram%. 𔄀 inches and one from the rectum. All histologic inter- in diameter. The dose rate at the center of pretations were

High dose rate brachytherapy for prevention of restenosis after percutaneous transluminal coronary angioplasty: Preliminary dosimetric tests of a new source presentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popowski, Y.; Rouzaud, M.; Kurtz, J.M.

1995-08-30

Balloon dilatation of coronary artery stenosis has become a standard treatment of atherosclerotic heart disease. Restenosis due to excessive intimal cell proliferation, which subsequently occurs in 20-50% of patients, represents one of the major clinical problems in contemporary cardiology, and no satisfactory method for its prevention has thus far been found. Because modest doses of radiation have proved effective in preventing certain types of abnormal cellular proliferation resulting from surgical trauma, and brachytherapy has already been used successfully after dilatation of peripheral arteries, development of a radioactive source suitable for coronary artery applications would be of great interest. Doses obtainedmore » at the surface of the balloon, for a 2-min exposure for the 0.26 mm wire (balloon inflated with air) and the 0.15 mm wire (air or contrast), were 56.5 Gy, 17.8 Gy, 5.4 Gy, respectively. As expected for a beta emitter, the fall-off in dose as a function of depth was rapid. External irradiation from the beta source was negligible. Our experiments indicate that the dose rates attainable at the surface of the angioplasty balloon using this technique allow the doses necessary for the inhibition of intimal cell proliferation to be reached within a relatively short period of time. The thin yttrium-90 wires are very easy to handle, and their mechanical and radioactive properties are well suited to the requirements of the catheterization procedure. 16 refs., 4 figs., 1 tab.« less

Optically Stimulated Luminescent Dosimetry for High Dose Rate Brachytherapy

PubMed Central

Tien, Christopher Jason; Ebeling, Robert; Hiatt, Jessica R.; Curran, Bruce; Sternick, Edward

2012-01-01

Purpose: The objective was to determine whether optically stimulated luminescent dosimeters (OSLDs) were appropriate for in vivo measurements in high dose rate brachytherapy. In order to make this distinction, three dosimetric characteristics were tested: dose linearity, dose rate dependence, and angular dependence. The Landauer nanoDot™ OSLDs were chosen due to their popularity and their availability commercially. Methods: To test the dose linearity, each OSLD was placed at a constant location and the dwell time was varied. Next, in order to test the dose rate dependence, each OSLD was placed at different OLSD-to-source distances and the dwell time was held constant. A curved geometry was created using a circular Accuboost® applicator in order to test angular dependence. Results: The OSLD response remained linear for high doses and was independent of dose rate. For doses up to 600 cGy, the linear coefficient of determination was 0.9988 with a response of 725 counts per cGy. The angular dependence was significant only in “edge-on” scenarios. Conclusion: OSLDs are conveniently read out using commercially available readers. OSLDs can be re-read and serve as a permanent record for clinical records or be annealed using conventional fluorescent light. Lastly, OSLDs are produced commercially for $5 each. Due to these convenient features, in conjunction with the dosimetric performance, OSLDs should be considered a clinically feasible and attractive tool for in vivo HDR brachytherapy measurements. PMID:22888476

Shielding synchrotron light sources: Advantages of circular shield walls tunnels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kramer, S. L.; Ghosh, V. J.; Breitfeller, M.

Third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produce significantly higher neutron component dose to the experimental floor than lower energy injection and ramped operations. High energy neutrons producedmore » in the forward direction from thin target beam losses are a major component of the dose rate outside the shield walls of the tunnel. The convention has been to provide thicker 90° ratchet walls to reduce this dose to the beam line users. We present an alternate circular shield wall design, which naturally and cost effectively increases the path length for this forward radiation in the shield wall and thereby substantially decreasing the dose rate for these beam losses. Here, this shield wall design will greatly reduce the dose rate to the users working near the front end optical components but will challenge the beam line designers to effectively utilize the longer length of beam line penetration in the shield wall. Additional advantages of the circular shield wall tunnel are that it's simpler to construct, allows greater access to the insertion devices and the upstream in tunnel beam line components, as well as reducing the volume of concrete and therefore the cost of the shield wall.« less

Shielding synchrotron light sources: Advantages of circular shield walls tunnels

DOE PAGES

Kramer, S. L.; Ghosh, V. J.; Breitfeller, M.

2016-04-26

Third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produce significantly higher neutron component dose to the experimental floor than lower energy injection and ramped operations. High energy neutrons producedmore » in the forward direction from thin target beam losses are a major component of the dose rate outside the shield walls of the tunnel. The convention has been to provide thicker 90° ratchet walls to reduce this dose to the beam line users. We present an alternate circular shield wall design, which naturally and cost effectively increases the path length for this forward radiation in the shield wall and thereby substantially decreasing the dose rate for these beam losses. Here, this shield wall design will greatly reduce the dose rate to the users working near the front end optical components but will challenge the beam line designers to effectively utilize the longer length of beam line penetration in the shield wall. Additional advantages of the circular shield wall tunnel are that it's simpler to construct, allows greater access to the insertion devices and the upstream in tunnel beam line components, as well as reducing the volume of concrete and therefore the cost of the shield wall.« less

ANALYSIS OF THE MOMENTS METHOD EXPERIMENT

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kloster, R.L.

1959-09-01

Monte Cario calculations show the effects of a plane water-air boundary on both fast neutron and gamma dose rates. Multigroup diffusion theory calculation for a reactor source shows the effects of a plane water-air boundary on thermal neutron dose rate. The results of Monte Cario and multigroup calculations are compared with experimental values. The predicted boundary effect for fast neutrons of 7.3% agrees within 16% with the measured effect of 6.3%. The gamma detector did not measure a boundary effect because it lacked sensitivity at low energies. However, the effect predicted for gamma rays of 5 to 10% is asmore » large as that for neutrons. An estimate of the boundary effect for thermal neutrons from a PoBe source is obtained from the results of muitigroup diffusion theory calcuiations for a reactor source. The calculated boundary effect agrees within 13% with the measured values. (auth)« less

High-dose-rate prostate brachytherapy inverse planning on dose-volume criteria by simulated annealing.

PubMed

Deist, T M; Gorissen, B L

2016-02-07

High-dose-rate brachytherapy is a tumor treatment method where a highly radioactive source is brought in close proximity to the tumor. In this paper we develop a simulated annealing algorithm to optimize the dwell times at preselected dwell positions to maximize tumor coverage under dose-volume constraints on the organs at risk. Compared to existing algorithms, our algorithm has advantages in terms of speed and objective value and does not require an expensive general purpose solver. Its success mainly depends on exploiting the efficiency of matrix multiplication and a careful selection of the neighboring states. In this paper we outline its details and make an in-depth comparison with existing methods using real patient data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farfan, E.; Jannik, T.

This article describes major studies performed by the Chernobyl Center's International Radioecology Laboratory (Slavutich, Ukraine) on radioecology of murine rodents and shrews inhabiting the Chernobyl Exclusion Zone. The article addresses the long-term (1986-2005) and seasonal dynamics of radioactive contamination of animals, and reviews interspecies differences in radionuclide accumulations and factors affecting the radionuclide accumulations. It is shown that bioavailability of radionuclides in the 'soil-to-plant' chain and a trophic specialization of animals play key roles in determining their actual contamination levels. The total absorbed dose rates in small mammals significantly reduced during the years following the Chernobyl Nuclear Power Plant accident.more » In 1986, the absorbed dose rate reached 1.3-6.0 Gy hr{sup -1} in the central areas of the Chernobyl Exclusion Zone (the 'Red Forest'). In 1988 and 1990, the total absorbed dose rates were 1.3 and 0.42 Gy hr{sup -1}, respectively. In 1995, 2000, and 2005, according to the present study, the total absorbed dose rates rarely exceeded 0.00023, 0.00018, and 0.00015 Gy hr{sup -1}, respectively. Contributions of individual radiation sources into the total absorbed dose are described.« less

A comprehensive experimental characterization of the iPIX gamma imager

NASA Astrophysics Data System (ADS)

Amgarou, K.; Paradiso, V.; Patoz, A.; Bonnet, F.; Handley, J.; Couturier, P.; Becker, F.; Menaa, N.

2016-08-01

The results of more than 280 different experiments aimed at exploring the main features and performances of a newly developed gamma imager, called iPIX, are summarized in this paper. iPIX is designed to quickly localize radioactive sources while estimating the ambient dose equivalent rate at the measurement point. It integrates a 1 mm thick CdTe detector directly bump-bonded to a Timepix chip, a tungsten coded-aperture mask, and a mini RGB camera. It also represents a major technological breakthrough in terms of lightness, compactness, usability, response sensitivity, and angular resolution. As an example of its key strengths, an 241Am source with a dose rate of only few nSv/h can be localized in less than one minute.

Optimal moderator materials at various proton energies considering photon dose rate after irradiation for an accelerator-driven ⁹Be(p, n) boron neutron capture therapy neutron source.

PubMed

Hashimoto, Y; Hiraga, F; Kiyanagi, Y

2015-12-01

We evaluated the accelerator beam power and the neutron-induced radioactivity of (9)Be(p, n) boron neutron capture therapy (BNCT) neutron sources having a MgF2, CaF2, or AlF3 moderator and driven by protons with energy from 8 MeV to 30 MeV. The optimal moderator materials were found to be MgF2 for proton energies less than 10 MeV because of lower required accelerator beam power and CaF2 for higher proton energies because of lower photon dose rate at the treatment position after neutron irradiation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Automatic optimisation of gamma dose rate sensor networks: The DETECT Optimisation Tool

NASA Astrophysics Data System (ADS)

Helle, K. B.; Müller, T. O.; Astrup, P.; Dyve, J. E.

2014-05-01

Fast delivery of comprehensive information on the radiological situation is essential for decision-making in nuclear emergencies. Most national radiological agencies in Europe employ gamma dose rate sensor networks to monitor radioactive pollution of the atmosphere. Sensor locations were often chosen using regular grids or according to administrative constraints. Nowadays, however, the choice can be based on more realistic risk assessment, as it is possible to simulate potential radioactive plumes. To support sensor planning, we developed the DETECT Optimisation Tool (DOT) within the scope of the EU FP 7 project DETECT. It evaluates the gamma dose rates that a proposed set of sensors might measure in an emergency and uses this information to optimise the sensor locations. The gamma dose rates are taken from a comprehensive library of simulations of atmospheric radioactive plumes from 64 source locations. These simulations cover the whole European Union, so the DOT allows evaluation and optimisation of sensor networks for all EU countries, as well as evaluation of fencing sensors around possible sources. Users can choose from seven cost functions to evaluate the capability of a given monitoring network for early detection of radioactive plumes or for the creation of dose maps. The DOT is implemented as a stand-alone easy-to-use JAVA-based application with a graphical user interface and an R backend. Users can run evaluations and optimisations, and display, store and download the results. The DOT runs on a server and can be accessed via common web browsers; it can also be installed locally.

A simple low-cost of liquid I-131 dispenser for routine radiopharmaceutical dispensing at nuclear medicine department, Institut Kanser Negara

NASA Astrophysics Data System (ADS)

Said, M. A.; Ashhar, Z. N.; Suhaimi, N. E. F.; Zainon, R.

2016-01-01

In routine radiopharmaceutical Iodine-131 (131I) dispensing, the amount of radiation dose received by the personnel depends on the distance between the personnel and the source, the time spent manipulating the source and the amount of shielding used to reduce the dose rate from the source. The novel iRAD-I131 dispenser using recycle 131I liquid lead pot will lead into low cost production, less maintenance and low dose received by the personnel that prepared the 131I. The new fabricated of low cost 131I dispenser was tested and the dose received by personnel were evaluated. The body of lead material is made from 2.5 cm lead shielded coated with epoxy paint to absorb the radiation dose up to 7.4 GBq of 131 I. The lead pot was supported with two stainless steel rod. The Optically Stimulated Luminescence (OSL) nanodot was used in this study to measure the dose rate at both extremities for every personnel who prepared the 131I. Each OSL nanodot was attached at the fingertip. Three different personnel (experienced between one to ten years above in preparing the radiopharmaceuticals) were participated in this study. The average equivalent dose at right and left hand were 122.694 ± 121.637 µSv/GBq and 77.281 ± 62.146 µSv/GBq respectively. This study found that the dose exposure received using iRAD-I131 was less up to seven times compared to the conventional method. The comparison of experimental data using iRAD-I131 and established radiopharmaceutical dispenser was also discussed. The innovation of 131I dispenser is highly recommended in a small radiopharmaceutical facility with limited budget. The novel iRAD-I131 enables implementation of higher output liquid dispensing with low radiation dose to the personnel.

A simple low-cost of liquid I-131 dispenser for routine radiopharmaceutical dispensing at nuclear medicine department, Institut Kanser Negara

DOE Office of Scientific and Technical Information (OSTI.GOV)

Said, M. A.; Suhaimi, N. E. F.; Ashhar, Z. N., E-mail: aminhpj@gmail.com

In routine radiopharmaceutical Iodine-131 ({sup 131}I) dispensing, the amount of radiation dose received by the personnel depends on the distance between the personnel and the source, the time spent manipulating the source and the amount of shielding used to reduce the dose rate from the source. The novel iRAD-I131 dispenser using recycle {sup 131}I liquid lead pot will lead into low cost production, less maintenance and low dose received by the personnel that prepared the {sup 131}I. The new fabricated of low cost {sup 131}I dispenser was tested and the dose received by personnel were evaluated. The body of leadmore » material is made from 2.5 cm lead shielded coated with epoxy paint to absorb the radiation dose up to 7.4 GBq of {sup 131} I. The lead pot was supported with two stainless steel rod. The Optically Stimulated Luminescence (OSL) nanodot was used in this study to measure the dose rate at both extremities for every personnel who prepared the {sup 131}I. Each OSL nanodot was attached at the fingertip. Three different personnel (experienced between one to ten years above in preparing the radiopharmaceuticals) were participated in this study. The average equivalent dose at right and left hand were 122.694 ± 121.637 µSv/GBq and 77.281 ± 62.146 µSv/GBq respectively. This study found that the dose exposure received using iRAD-I131 was less up to seven times compared to the conventional method. The comparison of experimental data using iRAD-I131 and established radiopharmaceutical dispenser was also discussed. The innovation of {sup 131}I dispenser is highly recommended in a small radiopharmaceutical facility with limited budget. The novel iRAD-I131 enables implementation of higher output liquid dispensing with low radiation dose to the personnel.« less

SU-E-J-93: Parametrisation of Dose to the Mucosa of the Anterior Rectal Wall in Transrectal Ultrasound Guided High-Dose-Rate Brachytherapy of the Prostate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Aitkenhead, A; Hamlett, L; Wood, D

2014-06-01

Purpose: In high-dose-rate (HDR) brachytherapy of the prostate, radiation is delivered from a number of radioactive sources which are inserted via catheter into the target volume. The rectal mucosa also receives dose during the treatment, which may lead to late toxicity effects. To allow possible links between rectal dose and toxicity to be investigated, suitable methods of parametrising the rectal dose are needed. Methods: During treatment of a series of 95 patients, anatomy and catheter locations were monitored by transrectal ultrasound, and target volume positions were contoured on the ultrasound scan by the therapist. The anterior rectal mucosal wall wasmore » identified by contouring the transrectal ultrasound balloon within the ultrasound scan. Source positions and dwell times, along with the dose delivered to the patient were computed using the Oncentra Prostate treatment planning system (TPS). Data for the series of patients were exported from the TPS in Dicom format, and a series of parametrisation methods were developed in a Matlab environment to assess the rectal dose. Results: Contours of the anterior rectal mucosa were voxelised within Matlab to allow the dose to the rectal mucosa to be analysed directly from the 3D dose grid. Dose parametrisations based on dose-surface (DSH) and dose-line (DLH) histograms were obtained. Both lateral and longitudinal extents of the mucosal dose were parametrised using dose-line histograms in the relevant directions. Conclusion: We have developed a series of dose parametrisations for quantifying the dose to the rectal mucosa during HDR prostate brachytherapy which are suitable for future studies investigating potential associations between mucosal dose and late toxicity effects. The geometry of the transrectal probe standardises the rectal anatomy, making this treatment technique particularly suited to studies of this nature.« less

Using LiF:Mg,Cu,P TLDs to estimate the absorbed dose to water in liquid water around an 192Ir brachytherapy source.

PubMed

Lucas, P Avilés; Aubineau-Lanièce, I; Lourenço, V; Vermesse, D; Cutarella, D

2014-01-01

The absorbed dose to water is the fundamental reference quantity for brachytherapy treatment planning systems and thermoluminescence dosimeters (TLDs) have been recognized as the most validated detectors for measurement of such a dosimetric descriptor. The detector response in a wide energy spectrum as that of an (192)Ir brachytherapy source as well as the specific measurement medium which surrounds the TLD need to be accounted for when estimating the absorbed dose. This paper develops a methodology based on highly sensitive LiF:Mg,Cu,P TLDs to directly estimate the absorbed dose to water in liquid water around a high dose rate (192)Ir brachytherapy source. Different experimental designs in liquid water and air were constructed to study the response of LiF:Mg,Cu,P TLDs when irradiated in several standard photon beams of the LNE-LNHB (French national metrology laboratory for ionizing radiation). Measurement strategies and Monte Carlo techniques were developed to calibrate the LiF:Mg,Cu,P detectors in the energy interval characteristic of that found when TLDs are immersed in water around an (192)Ir source. Finally, an experimental system was designed to irradiate TLDs at different angles between 1 and 11 cm away from an (192)Ir source in liquid water. Monte Carlo simulations were performed to correct measured results to provide estimates of the absorbed dose to water in water around the (192)Ir source. The dose response dependence of LiF:Mg,Cu,P TLDs with the linear energy transfer of secondary electrons followed the same variations as those of published results. The calibration strategy which used TLDs in air exposed to a standard N-250 ISO x-ray beam and TLDs in water irradiated with a standard (137)Cs beam provided an estimated mean uncertainty of 2.8% (k = 1) in the TLD calibration coefficient for irradiations by the (192)Ir source in water. The 3D TLD measurements performed in liquid water were obtained with a maximum uncertainty of 11% (k = 1) found at 1 cm from the source. Radial dose values in water were compared against published results of the American Association of Physicists in Medicine and the European Society for Radiotherapy and Oncology and no significant differences (maximum value of 3.1%) were found within uncertainties except for one position at 9 cm (5.8%). At this location the background contribution relative to the TLD signal is relatively small and an unexpected experimental fluctuation in the background estimate may have caused such a large discrepancy. This paper shows that reliable measurements with TLDs in complex energy spectra require a study of the detector dose response with the radiation quality and specific calibration methodologies which model accurately the experimental conditions where the detectors will be used. The authors have developed and studied a method with highly sensitive TLDs and contributed to its validation by comparison with results from the literature. This methodology can be used to provide direct estimates of the absorbed dose rate in water for irradiations with HDR (192)Ir brachytherapy sources.

Radiation dosimetry properties of smartphone CMOS sensors.

PubMed

Van Hoey, Olivier; Salavrakos, Alexia; Marques, Antonio; Nagao, Alexandre; Willems, Ruben; Vanhavere, Filip; Cauwels, Vanessa; Nascimento, Luana F

2016-03-01

During the past years, several smartphone applications have been developed for radiation detection. These applications measure radiation using the smartphone camera complementary metal-oxide-semiconductor sensor. They are potentially useful for data collection and personal dose assessment in case of a radiological incident. However, it is important to assess these applications. Six applications were tested by means of irradiations with calibrated X-ray and gamma sources. It was shown that the measurement stabilises only after at least 10-25 min. All applications exhibited a flat dose rate response in the studied ambient dose equivalent range from 2 to 1000 μSv h(-1). Most applications significantly over- or underestimate the dose rate or are not calibrated in terms of dose rate. A considerable energy dependence was observed below 100 keV but not for the higher energy range more relevant for incident scenarios. Photon impact angle variation gave a measured signal variation of only about 10 %. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Calculated organ doses for Mayak production association central hall using ICRP and MCNP.

PubMed

Choe, Dong-Ok; Shelkey, Brenda N; Wilde, Justin L; Walk, Heidi A; Slaughter, David M

2003-03-01

As part of an ongoing dose reconstruction project, equivalent organ dose rates from photons and neutrons were estimated using the energy spectra measured in the central hall above the graphite reactor core located in the Russian Mayak Production Association facility. Reconstruction of the work environment was necessary due to the lack of personal dosimeter data for neutrons in the time period prior to 1987. A typical worker scenario for the central hall was developed for the Monte Carlo Neutron Photon-4B (MCNP) code. The resultant equivalent dose rates for neutrons and photons were compared with the equivalent dose rates derived from calculations using the conversion coefficients in the International Commission on Radiological Protection Publications 51 and 74 in order to validate the model scenario for this Russian facility. The MCNP results were in good agreement with the results of the ICRP publications indicating the modeling scenario was consistent with actual work conditions given the spectra provided. The MCNP code will allow for additional orientations to accurately reflect source locations.

Contributions of Various Radiological Sources to Background in a Suburban Environment

DOE PAGES

Milvenan, Richard D.; Hayes, Robert B.

2016-11-01

This work is a brief overview and comparison of dose rates stemming from both indoor and outdoor natural background radiation and household objects within a suburban environment in North Carolina. Combined gamma and beta dose rates were taken from indoor objects that ranged from the potassium in fruit to the americium in smoke detectors. For outdoor measurements, various height and time data samples were collected to show fluctuations in dose rate due to temperature inversion and geometric attenuation. Although each sample tested proved to have a statistically significant increase over background using Students t-test, no sample proved to be moremore » than a minor increase in natural radiation dose. Furthermore, the relative contributions from natural radioactivity such as potassium in foods and common household items are shown to be easily distinguished from background using standard handheld instrumentation when applied in a systematic, methodological manner.« less

Contributions of Various Radiological Sources to Background in a Suburban Environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milvenan, Richard D.; Hayes, Robert B.

This work is a brief overview and comparison of dose rates stemming from both indoor and outdoor natural background radiation and household objects within a suburban environment in North Carolina. Combined gamma and beta dose rates were taken from indoor objects that ranged from the potassium in fruit to the americium in smoke detectors. For outdoor measurements, various height and time data samples were collected to show fluctuations in dose rate due to temperature inversion and geometric attenuation. Although each sample tested proved to have a statistically significant increase over background using Students t-test, no sample proved to be moremore » than a minor increase in natural radiation dose. Furthermore, the relative contributions from natural radioactivity such as potassium in foods and common household items are shown to be easily distinguished from background using standard handheld instrumentation when applied in a systematic, methodological manner.« less

Clinical outcomes and cost minimization with an alternative dosing regimen for meropenem in a community hospital.

PubMed

Patel, Gita Wasan; Duquaine, Susan M; McKinnon, Peggy S

2007-12-01

To compare outcomes and cost for the traditional United States Food and Drug Administration-approved dosing regimen for meropenem versus an alternative dosing regimen providing similar pharmacodynamic exposure with a lower total daily dose. Retrospective cohort study with a cost-minimization analysis. A 417-bed, privately owned community hospital. One hundred patients who received meropenem 1 g every 8 or 12 hours (traditional dosing regimen) between January 1 and September 30, 2004 (historical controls), and 192 patients who received meropenem 500 mg every 6 or 8 hours (alternative dosing regimen) between October 1, 2004, and September 30, 2005. Demographic and clinical data were collected for all patients. Cost-minimization analysis was performed by using the drug acquisition cost for meropenem. Demographics, sources of infection, distributions of organisms, and Charlson Comorbidity Index scores were similar between patients in the traditionally and alternatively dosed groups. Concomitant therapy, duration of therapy, success rates, lengths of stay, and in-hospital mortality rates were also similar between groups. Median time to the resolution of symptoms was 3 days for traditional dosing and 1.5 days for alternative dosing (p<0.0001). A logistic regression model including the dosing strategy showed that only polymicrobial infections and sepsis were associated with increased failure rates. The median cost for antibiotics was $439.05/patient for traditional dosing and $234.08/patient for alternative dosing (p<0.0001). An alternative dosing regimen for meropenem with a lower total daily dose yielded patient outcomes, including success rates and duration of therapy, equivalent to those of the traditional dosing regimen. Alternative dosing decreased total drug exposure, costs for antibiotics, and time to the resolution of infections.

Radionuclide production and dose rate estimation during the commissioning of the W-Ta spallation target

NASA Astrophysics Data System (ADS)

Yu, Q. Z.; Liang, T. J.

2018-06-01

China Spallation Neutron Source (CSNS) is intended to begin operation in 2018. CSNS is an accelerator-base multidisciplinary user facility. The pulsed neutrons are produced by a 1.6GeV short-pulsed proton beam impinging on a W-Ta spallation target, at a beam power of100 kW and a repetition rate of 25 Hz. 20 neutron beam lines are extracted for the neutron scattering and neutron irradiation research. During the commissioning and maintenance scenarios, the gamma rays induced from the W-Ta target can cause the dose threat to the personal and the environment. In this paper, the gamma dose rate distributions for the W-Ta spallation are calculated, based on the engineering model of the target-moderator-reflector system. The shipping cask is analyzed to satisfy the dose rate limit that less than 2 mSv/h at the surface of the shipping cask. All calculations are performed by the Monte carlo code MCNPX2.5 and the activation code CINDER’90.

Study of two different radioactive sources for prostate brachytherapy treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pereira Neves, Lucio; Perini, Ana Paula; Souza Santos, William de

In this study we evaluated two radioactive sources for brachytherapy treatments. Our main goal was to quantify the absorbed doses on organs and tissues of an adult male patient, submitted to a brachytherapy treatment with two radioactive sources. We evaluated a {sup 192}Ir and a {sup 125}I radioactive sources. The {sup 192}Ir radioactive source is a cylinder with 0.09 cm in diameter and 0.415 cm long. The {sup 125}I radioactive source is also a cylinder, with 0.08 cm in diameter and 0.45 cm long. To evaluate the absorbed dose distribution on the prostate, and other organs and tissues of anmore » adult man, a male virtual anthropomorphic phantom MASH, coupled in the radiation transport code MCNPX 2.7.0, was employed.We simulated 75, 90 and 102 radioactive sources of {sup 125}I and one of {sup 192}Ir, inside the prostate, as normally used in these treatments, and each treatment was simulated separately. As this phantom was developed in a supine position, the displacement of the internal organs of the chest, compression of the lungs and reduction of the sagittal diameter were all taken into account. For the {sup 192}Ir, the higher doses values were obtained for the prostate and surrounding organs, as the colon, gonads and bladder. Considering the {sup 125}I sources, with photons with lower energies, the doses to organs that are far from the prostate were lower. All values for the dose rates are in agreement with those recommended for brachytherapy treatments. Besides that, the new seeds evaluated in this work present usefulness as a new tool in prostate brachytherapy treatments, and the methodology employed in this work may be applied for other radiation sources, or treatments. (authors)« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, X

Purpose: To explore the real-time dose verification method in volumetric modulated arc radiotherapy (VMAT) with a 2D array ion chamber array. Methods: The 2D ion chamber array was fixed on the panel of electronic portal imaging device (EPID). Source-detector distance (SDD)was 140cm. 8mm RW3 solid water was added to the detector panel to achieve maximum readings.The patient plans for esophageal, prostate and liver cancers were selected to deliver on the cylindrical Cheese phantom 5 times in order to validate the reproducibility of doses. Real-time patient transit dose measurements were performed at each fraction. Dose distributions wereevaluated using gamma index criteriamore » of 3mm DTA and 3% dose difference referred to the firsttime Result. Results: The gamma index pass rate in the Cheese phantom were about 98%; The gamma index pass rate for esophageal, liver and prostate cancer patient were about 92%,94%, and 92%, respectively; Gamma pass rate for all single fraction were more than 90%. Conclusion: The 2D array is capable of monitoring the real time transit doses during VMAT delivery. It is helpful to improve the treatment accuracy.« less

Sol-gel derived copper-doped silica glass as a sensitive material for X-ray beam dosimetry

NASA Astrophysics Data System (ADS)

Capoen, Bruno; Hamzaoui, Hicham El; Bouazaoui, Mohamed; Ouerdane, Youcef; Boukenter, Aziz; Girard, Sylvain; Marcandella, Claude; Duhamel, Olivier

2016-01-01

The light emission from a sol-gel-derived Cu-doped silica glass was studied under 10 keV X-ray irradiation using a fibered setup. Both radioluminescence (RL) and optically stimulated luminescence (OSL) were analyzed at different high dose rates up to 50 Gy/s and for different exposure times, yielding accumulated doses up to 50 kGy (in SiO2). Even if a darkening effect appears at this dose level, the material remains X-sensitive after exposure to several kGy. At low dose rate, the scintillation mechanisms are similar to photoluminescence, involving the Cu+ ions electronic levels, contrary to the nonlinear domain (for dose rates higher than 30 Gy/s). This RL, as well as the OSL, could be exploited in their linear domain to measure doses as high as 3 kGy. A thorough study of the OSL signal has shown that it must be employed with caution in order to take the fading phenomenon and the response dependency on stimulation source intensity into consideration.

Modification and validation of an analytical source model for external beam radiotherapy Monte Carlo dose calculations.

PubMed

Davidson, Scott E; Cui, Jing; Kry, Stephen; Deasy, Joseph O; Ibbott, Geoffrey S; Vicic, Milos; White, R Allen; Followill, David S

2016-08-01

A dose calculation tool, which combines the accuracy of the dose planning method (DPM) Monte Carlo code and the versatility of a practical analytical multisource model, which was previously reported has been improved and validated for the Varian 6 and 10 MV linear accelerators (linacs). The calculation tool can be used to calculate doses in advanced clinical application studies. One shortcoming of current clinical trials that report dose from patient plans is the lack of a standardized dose calculation methodology. Because commercial treatment planning systems (TPSs) have their own dose calculation algorithms and the clinical trial participant who uses these systems is responsible for commissioning the beam model, variation exists in the reported calculated dose distributions. Today's modern linac is manufactured to tight specifications so that variability within a linac model is quite low. The expectation is that a single dose calculation tool for a specific linac model can be used to accurately recalculate dose from patient plans that have been submitted to the clinical trial community from any institution. The calculation tool would provide for a more meaningful outcome analysis. The analytical source model was described by a primary point source, a secondary extra-focal source, and a contaminant electron source. Off-axis energy softening and fluence effects were also included. The additions of hyperbolic functions have been incorporated into the model to correct for the changes in output and in electron contamination with field size. A multileaf collimator (MLC) model is included to facilitate phantom and patient dose calculations. An offset to the MLC leaf positions was used to correct for the rudimentary assumed primary point source. Dose calculations of the depth dose and profiles for field sizes 4 × 4 to 40 × 40 cm agree with measurement within 2% of the maximum dose or 2 mm distance to agreement (DTA) for 95% of the data points tested. The model was capable of predicting the depth of the maximum dose within 1 mm. Anthropomorphic phantom benchmark testing of modulated and patterned MLCs treatment plans showed agreement to measurement within 3% in target regions using thermoluminescent dosimeters (TLD). Using radiochromic film normalized to TLD, a gamma criteria of 3% of maximum dose and 2 mm DTA was applied with a pass rate of least 85% in the high dose, high gradient, and low dose regions. Finally, recalculations of patient plans using DPM showed good agreement relative to a commercial TPS when comparing dose volume histograms and 2D dose distributions. A unique analytical source model coupled to the dose planning method Monte Carlo dose calculation code has been modified and validated using basic beam data and anthropomorphic phantom measurement. While this tool can be applied in general use for a particular linac model, specifically it was developed to provide a singular methodology to independently assess treatment plan dose distributions from those clinical institutions participating in National Cancer Institute trials.

Impact of the differential fluence distribution of brachytherapy sources on the spectroscopic dose-rate constant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malin, Martha J.; Bartol, Laura J.; DeWerd, Larry A., E-mail: mmalin@wisc.edu, E-mail: ladewerd@wisc.edu

2015-05-15

Purpose: To investigate why dose-rate constants for {sup 125}I and {sup 103}Pd seeds computed using the spectroscopic technique, Λ{sub spec}, differ from those computed with standard Monte Carlo (MC) techniques. A potential cause of these discrepancies is the spectroscopic technique’s use of approximations of the true fluence distribution leaving the source, φ{sub full}. In particular, the fluence distribution used in the spectroscopic technique, φ{sub spec}, approximates the spatial, angular, and energy distributions of φ{sub full}. This work quantified the extent to which each of these approximations affects the accuracy of Λ{sub spec}. Additionally, this study investigated how the simplified water-onlymore » model used in the spectroscopic technique impacts the accuracy of Λ{sub spec}. Methods: Dose-rate constants as described in the AAPM TG-43U1 report, Λ{sub full}, were computed with MC simulations using the full source geometry for each of 14 different {sup 125}I and 6 different {sup 103}Pd source models. In addition, the spectrum emitted along the perpendicular bisector of each source was simulated in vacuum using the full source model and used to compute Λ{sub spec}. Λ{sub spec} was compared to Λ{sub full} to verify the discrepancy reported by Rodriguez and Rogers. Using MC simulations, a phase space of the fluence leaving the encapsulation of each full source model was created. The spatial and angular distributions of φ{sub full} were extracted from the phase spaces and were qualitatively compared to those used by φ{sub spec}. Additionally, each phase space was modified to reflect one of the approximated distributions (spatial, angular, or energy) used by φ{sub spec}. The dose-rate constant resulting from using approximated distribution i, Λ{sub approx,i}, was computed using the modified phase space and compared to Λ{sub full}. For each source, this process was repeated for each approximation in order to determine which approximations used in the spectroscopic technique affect the accuracy of Λ{sub spec}. Results: For all sources studied, the angular and spatial distributions of φ{sub full} were more complex than the distributions used in φ{sub spec}. Differences between Λ{sub spec} and Λ{sub full} ranged from −0.6% to +6.4%, confirming the discrepancies found by Rodriguez and Rogers. The largest contribution to the discrepancy was the assumption of isotropic emission in φ{sub spec}, which caused differences in Λ of up to +5.3% relative to Λ{sub full}. Use of the approximated spatial and energy distributions caused smaller average discrepancies in Λ of −0.4% and +0.1%, respectively. The water-only model introduced an average discrepancy in Λ of −0.4%. Conclusions: The approximations used in φ{sub spec} caused discrepancies between Λ{sub approx,i} and Λ{sub full} of up to 7.8%. With the exception of the energy distribution, the approximations used in φ{sub spec} contributed to this discrepancy for all source models studied. To improve the accuracy of Λ{sub spec}, the spatial and angular distributions of φ{sub full} could be measured, with the measurements replacing the approximated distributions. The methodology used in this work could be used to determine the resolution that such measurements would require by computing the dose-rate constants from phase spaces modified to reflect φ{sub full} binned at different spatial and angular resolutions.« less

Method and apparatus for measuring low currents in capacitance devices

DOEpatents

Kopp, M.K.; Manning, F.W.; Guerrant, G.C.

1986-06-04

A method and apparatus for measuring subnanoampere currents in capacitance devices is reported. The method is based on a comparison of the voltages developed across the capacitance device with that of a reference capacitor in which the current is adjusted by means of a variable current source to produce a stable voltage difference. The current varying means of the variable current source is calibrated to provide a read out of the measured current. Current gain may be provided by using a reference capacitor which is larger than the device capacitance with a corresponding increase in current supplied through the reference capacitor. The gain is then the ratio of the reference capacitance to the device capacitance. In one illustrated embodiment, the invention makes possible a new type of ionizing radiation dose-rate monitor where dose-rate is measured by discharging a reference capacitor with a variable current source at the same rate that radiation is discharging an ionization chamber. The invention eliminates high-megohm resistors and low current ammeters used in low-current measuring instruments.

A review on natural background radiation

PubMed Central

Shahbazi-Gahrouei, Daryoush; Gholami, Mehrdad; Setayandeh, Samaneh

2013-01-01

The world is naturally radioactive and approximately 82% of human-absorbed radiation doses, which are out of control, arise from natural sources such as cosmic, terrestrial, and exposure from inhalation or intake radiation sources. In recent years, several international studies have been carried out, which have reported different values regarding the effect of background radiation on human health. Gamma radiation emitted from natural sources (background radiation) is largely due to primordial radionuclides, mainly 232Th and 238U series, and their decay products, as well as 40K, which exist at trace levels in the earth's crust. Their concentrations in soil, sands, and rocks depend on the local geology of each region in the world. Naturally occurring radioactive materials generally contain terrestrial-origin radionuclides, left over since the creation of the earth. In addition, the existence of some springs and quarries increases the dose rate of background radiation in some regions that are known as high level background radiation regions. The type of building materials used in houses can also affect the dose rate of background radiations. The present review article was carried out to consider all of the natural radiations, including cosmic, terrestrial, and food radiation. PMID:24223380

Dual-source spiral CT with pitch up to 3.2 and 75 ms temporal resolution: image reconstruction and assessment of image quality.

PubMed

Flohr, Thomas G; Leng, Shuai; Yu, Lifeng; Aiimendinger, Thomas; Bruder, Herbert; Petersilka, Martin; Eusemann, Christian D; Stierstorfer, Karl; Schmidt, Bernhard; McCollough, Cynthia H

2009-12-01

To present the theory for image reconstruction of a high-pitch, high-temporal-resolution spiral scan mode for dual-source CT (DSCT) and evaluate its image quality and dose. With the use of two x-ray sources and two data acquisition systems, spiral CT exams having a nominal temporal resolution per image of up to one-quarter of the gantry rotation time can be acquired using pitch values up to 3.2. The scan field of view (SFOV) for this mode, however, is limited to the SFOV of the second detector as a maximum, depending on the pitch. Spatial and low contrast resolution, image uniformity and noise, CT number accuracy and linearity, and radiation dose were assessed using the ACR CT accreditation phantom, a 30 cm diameter cylindrical water phantom or a 32 cm diameter cylindrical PMMA CTDI phantom. Slice sensitivity profiles (SSPs) were measured for different nominal slice thicknesses, and an anthropomorphic phantom was used to assess image artifacts. Results were compared between single-source scans at pitch = 1.0 and dual-source scans at pitch = 3.2. In addition, image quality and temporal resolution of an ECG-triggered version of the DSCT high-pitch spiral scan mode were evaluated with a moving coronary artery phantom, and radiation dose was assessed in comparison with other existing cardiac scan techniques. No significant differences in quantitative measures of image quality were found between single-source scans at pitch = 1.0 and dual-source scans at pitch = 3.2 for spatial and low contrast resolution, CT number accuracy and linearity, SSPs, image uniformity, and noise. The pitch value (1.6 pitch 3.2) had only a minor impact on radiation dose and image noise when the effective tube current time product (mA s/pitch) was kept constant. However, while not severe, artifacts were found to be more prevalent for the dual-source pitch = 3.2 scan mode when structures varied markedly along the z axis, particularly for head scans. Images of the moving coronary artery phantom acquired with the ECG-triggered high-pitch scan mode were visually free from motion artifacts at heart rates of 60 and 70 bpm. However, image quality started to deteriorate for higher heart rates. At equivalent image quality, the ECG-triggered high-pitch scan mode demonstrated lower radiation dose than other cardiac scan techniques on the same DSCT equipment (25% and 60% dose reduction compared to ECG-triggered sequential step-and-shoot and ECG-gated spiral with x-ray pulsing). A high-pitch (up to pitch = 3.2), high-temporal-resolution (up to 75 ms) dual-source CT scan mode produced equivalent image quality relative to single-source scans using a more typical pitch value (pitch = 1.0). The resultant reduction in the overall acquisition time may offer clinical advantage for cardiovascular, trauma, and pediatric CT applications. In addition, ECG-triggered high-pitch scanning may be useful as an alternative to ECG-triggered sequential scanning for patients with low to moderate heart rates up to 70 bpm, with the potential to scan the heart within one heart beat at reduced radiation dose.

Portfolio of prospective clinical trials including brachytherapy: an analysis of the ClinicalTrials.gov database.

PubMed

Cihoric, Nikola; Tsikkinis, Alexandros; Miguelez, Cristina Gutierrez; Strnad, Vratislav; Soldatovic, Ivan; Ghadjar, Pirus; Jeremic, Branislav; Dal Pra, Alan; Aebersold, Daniel M; Lössl, Kristina

2016-03-22

To evaluate the current status of prospective interventional clinical trials that includes brachytherapy (BT) procedures. The records of 175,538 (100 %) clinical trials registered at ClinicalTrials.gov were downloaded on September 2014 and a database was established. Trials using BT as an intervention were identified for further analyses. The selected trials were manually categorized according to indication(s), BT source, applied dose rate, primary sponsor type, location, protocol initiator and funding source. We analyzed trials across 8 available trial protocol elements registered within the database. In total 245 clinical trials were identified, 147 with BT as primary investigated treatment modality and 98 that included BT as an optional treatment component or as part of the standard treatment. Academic centers were the most frequent protocol initiators in trials where BT was the primary investigational treatment modality (p < 0.01). High dose rate (HDR) BT was the most frequently investigated type of BT dose rate (46.3 %) followed by low dose rate (LDR) (42.0 %). Prostate was the most frequently investigated tumor entity in trials with BT as the primary treatment modality (40.1 %) followed by breast cancer (17.0 %). BT was rarely the primary investigated treatment modality for cervical cancer (6.8 %). Most clinical trials using BT are predominantly in early phases, investigator-initiated and with low accrual numbers. Current investigational activities that include BT mainly focus on prostate and breast cancers. Important questions concerning the optimal usage of BT will not be answered in the near future.

SU-E-T-795: Validations of Dose Calculation Accuracy of Acuros BV in High-Dose-Rate (HDR) Brachytherapy with a Shielded Cylinder Applicator Using Monte Carlo Simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Y; Department of Engineering Physics, Tsinghua University, Beijing; Tian, Z

Purpose: Acuros BV has become available to perform accurate dose calculations in high-dose-rate (HDR) brachytherapy with phantom heterogeneity considered by solving the Boltzmann transport equation. In this work, we performed validation studies regarding the dose calculation accuracy of Acuros BV in cases with a shielded cylinder applicator using Monte Carlo (MC) simulations. Methods: Fifteen cases were considered in our studies, covering five different diameters of the applicator and three different shielding degrees. For each case, a digital phantom was created in Varian BrachyVision with the cylinder applicator inserted in the middle of a large water phantom. A treatment plan withmore » eight dwell positions was generated for these fifteen cases. Dose calculations were performed with Acuros BV. We then generated a voxelized phantom of the same geometry, and the materials were modeled according to the vendor’s specifications. MC dose calculations were then performed using our in-house developed fast MC dose engine for HDR brachytherapy (gBMC) on a GPU platform, which is able to simulate both photon transport and electron transport in a voxelized geometry. A phase-space file for the Ir-192 HDR source was used as a source model for MC simulations. Results: Satisfactory agreements between the dose distributions calculated by Acuros BV and those calculated by gBMC were observed in all cases. Quantitatively, we computed point-wise dose difference within the region that receives a dose higher than 10% of the reference dose, defined to be the dose at 5mm outward away from the applicator surface. The mean dose difference was ∼0.45%–0.51% and the 95-percentile maximum difference was ∼1.24%–1.47%. Conclusion: Acuros BV is able to accurately perform dose calculations in HDR brachytherapy with a shielded cylinder applicator.« less

D-T Neutron Skyshine Experiments at JAERI/FNS

NASA Astrophysics Data System (ADS)

Nishitani, Takeo; Ochiai, Kentaro; Yoshida, Shigeo; Tanaka, Ryohei; Wakisaka, Masashi; Nakao, Makoto; Sato, Satoshi; Yamauchi, Michinori; Hori, Jun-Ichi; Takahashi, Akito; Kaneko, Jun-Ichi; Sawamura, Teruko

The D-T neutron skyshine experiments have been carried out at the Fusion Neutronics Source (FNS) of JAERI with the neutron yield of ˜1.7×1011n/s. The concrete thickness of the roof and the wall of a FNS target room are 1.15 and 2 m, respectively. The FNS skyshine port with a size of 0.9 × 0.9 m2 was open during the experimental period.The radiation dose rate outside the target room was measured as far as about 550 m away from the D-T target point with a spherical rem-counter. The highest neutron dose was about 0.5 μSv/hr at a distance of 30 m from the D-T target point and the dose rate was attenuated to 0.002 μSv/hr at a distance of 550 m. The measured neutron dose distribution was analyzed with Monte Carlo code MCNP-4B and a simple line source model. The MCNP calculation overestimates the neutron dose in the distance range larger than 250 m. The neutron spectra were evaluated with a 3He detector with different thickness of polyethylene neutron moderators. Secondary gamma-rays were measured with high purity Ge detectors and NaI scintillation detectors.

Coupled particle-in-cell and Monte Carlo transport modeling of intense radiographic sources

NASA Astrophysics Data System (ADS)

Rose, D. V.; Welch, D. R.; Oliver, B. V.; Clark, R. E.; Johnson, D. L.; Maenchen, J. E.; Menge, P. R.; Olson, C. L.; Rovang, D. C.

2002-03-01

Dose-rate calculations for intense electron-beam diodes using particle-in-cell (PIC) simulations along with Monte Carlo electron/photon transport calculations are presented. The electromagnetic PIC simulations are used to model the dynamic operation of the rod-pinch and immersed-B diodes. These simulations include algorithms for tracking electron scattering and energy loss in dense materials. The positions and momenta of photons created in these materials are recorded and separate Monte Carlo calculations are used to transport the photons to determine the dose in far-field detectors. These combined calculations are used to determine radiographer equations (dose scaling as a function of diode current and voltage) that are compared directly with measured dose rates obtained on the SABRE generator at Sandia National Laboratories.

Absolute measurement of LDR brachytherapy source emitted power: Instrument design and initial measurements.

PubMed

Malin, Martha J; Palmer, Benjamin R; DeWerd, Larry A

2016-02-01

Energy-based source strength metrics may find use with model-based dose calculation algorithms, but no instruments exist that can measure the energy emitted from low-dose rate (LDR) sources. This work developed a calorimetric technique for measuring the power emitted from encapsulated low-dose rate, photon-emitting brachytherapy sources. This quantity is called emitted power (EP). The measurement methodology, instrument design and performance, and EP measurements made with the calorimeter are presented in this work. A calorimeter operating with a liquid helium thermal sink was developed to measure EP from LDR brachytherapy sources. The calorimeter employed an electrical substitution technique to determine the power emitted from the source. The calorimeter's performance and thermal system were characterized. EP measurements were made using four (125)I sources with air-kerma strengths ranging from 2.3 to 5.6 U and corresponding EPs of 0.39-0.79 μW, respectively. Three Best Medical 2301 sources and one Oncura 6711 source were measured. EP was also computed by converting measured air-kerma strengths to EPs through Monte Carlo-derived conversion factors. The measured EP and derived EPs were compared to determine the accuracy of the calorimeter measurement technique. The calorimeter had a noise floor of 1-3 nW and a repeatability of 30-60 nW. The calorimeter was stable to within 5 nW over a 12 h measurement window. All measured values agreed with derived EPs to within 10%, with three of the four sources agreeing to within 4%. Calorimeter measurements had uncertainties ranging from 2.6% to 4.5% at the k = 1 level. The values of the derived EPs had uncertainties ranging from 2.9% to 3.6% at the k = 1 level. A calorimeter capable of measuring the EP from LDR sources has been developed and validated for (125)I sources with EPs between 0.43 and 0.79 μW.

Adaptive error detection for HDR/PDR brachytherapy: Guidance for decision making during real-time in vivo point dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kertzscher, Gustavo, E-mail: guke@dtu.dk; Andersen, Claus E., E-mail: clan@dtu.dk; Tanderup, Kari, E-mail: karitand@rm.dk

Purpose: This study presents an adaptive error detection algorithm (AEDA) for real-timein vivo point dosimetry during high dose rate (HDR) or pulsed dose rate (PDR) brachytherapy (BT) where the error identification, in contrast to existing approaches, does not depend on an a priori reconstruction of the dosimeter position. Instead, the treatment is judged based on dose rate comparisons between measurements and calculations of the most viable dosimeter position provided by the AEDA in a data driven approach. As a result, the AEDA compensates for false error cases related to systematic effects of the dosimeter position reconstruction. Given its nearly exclusivemore » dependence on stable dosimeter positioning, the AEDA allows for a substantially simplified and time efficient real-time in vivo BT dosimetry implementation. Methods: In the event of a measured potential treatment error, the AEDA proposes the most viable dosimeter position out of alternatives to the original reconstruction by means of a data driven matching procedure between dose rate distributions. If measured dose rates do not differ significantly from the most viable alternative, the initial error indication may be attributed to a mispositioned or misreconstructed dosimeter (false error). However, if the error declaration persists, no viable dosimeter position can be found to explain the error, hence the discrepancy is more likely to originate from a misplaced or misreconstructed source applicator or from erroneously connected source guide tubes (true error). Results: The AEDA applied on twoin vivo dosimetry implementations for pulsed dose rate BT demonstrated that the AEDA correctly described effects responsible for initial error indications. The AEDA was able to correctly identify the major part of all permutations of simulated guide tube swap errors and simulated shifts of individual needles from the original reconstruction. Unidentified errors corresponded to scenarios where the dosimeter position was sufficiently symmetric with respect to error and no-error source position constellations. The AEDA was able to correctly identify all false errors represented by mispositioned dosimeters contrary to an error detection algorithm relying on the original reconstruction. Conclusions: The study demonstrates that the AEDA error identification during HDR/PDR BT relies on a stable dosimeter position rather than on an accurate dosimeter reconstruction, and the AEDA’s capacity to distinguish between true and false error scenarios. The study further shows that the AEDA can offer guidance in decision making in the event of potential errors detected with real-timein vivo point dosimetry.« less

Assessing doses to terrestrial wildlife at a radioactive waste disposal site: inter-comparison of modelling approaches.

PubMed

Johansen, M P; Barnett, C L; Beresford, N A; Brown, J E; Černe, M; Howard, B J; Kamboj, S; Keum, D-K; Smodiš, B; Twining, J R; Vandenhove, H; Vives i Batlle, J; Wood, M D; Yu, C

2012-06-15

Radiological doses to terrestrial wildlife were examined in this model inter-comparison study that emphasised factors causing variability in dose estimation. The study participants used varying modelling approaches and information sources to estimate dose rates and tissue concentrations for a range of biota types exposed to soil contamination at a shallow radionuclide waste burial site in Australia. Results indicated that the dominant factor causing variation in dose rate estimates (up to three orders of magnitude on mean total dose rates) was the soil-to-organism transfer of radionuclides that included variation in transfer parameter values as well as transfer calculation methods. Additional variation was associated with other modelling factors including: how participants conceptualised and modelled the exposure configurations (two orders of magnitude); which progeny to include with the parent radionuclide (typically less than one order of magnitude); and dose calculation parameters, including radiation weighting factors and dose conversion coefficients (typically less than one order of magnitude). Probabilistic approaches to model parameterisation were used to encompass and describe variable model parameters and outcomes. The study confirms the need for continued evaluation of the underlying mechanisms governing soil-to-organism transfer of radionuclides to improve estimation of dose rates to terrestrial wildlife. The exposure pathways and configurations available in most current codes are limited when considering instances where organisms access subsurface contamination through rooting, burrowing, or using different localised waste areas as part of their habitual routines. Crown Copyright © 2012. Published by Elsevier B.V. All rights reserved.

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source.

PubMed

Shi, Chengyu; Guo, Bingqi; Cheng, Chih-Yao; Eng, Tony; Papanikolaou, Nikos

2010-09-21

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V(100) reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95.2% in water phantoms without RBE enhancement (planned BED). About 10% increase in the source output is required to raise BED PTV V(100) to 95%. As a conclusion, the composite effect of dose reduction in the target due to heterogeneities and RBE enhancement results in a net effect of 5.3% target BED coverage loss for electronic brachytherapy. Therefore, it is suggested that about 10% increase in the source output may be necessary to achieve sufficient target coverage higher than 95%.

Applications of tissue heterogeneity corrections and biologically effective dose volume histograms in assessing the doses for accelerated partial breast irradiation using an electronic brachytherapy source

NASA Astrophysics Data System (ADS)

Shi, Chengyu; Guo, Bingqi; Cheng, Chih-Yao; Eng, Tony; Papanikolaou, Nikos

2010-09-01

A low-energy electronic brachytherapy source (EBS), the model S700 Axxent™ x-ray device developed by Xoft Inc., has been used in high dose rate (HDR) intracavitary accelerated partial breast irradiation (APBI) as an alternative to an Ir-192 source. The prescription dose and delivery schema of the electronic brachytherapy APBI plan are the same as the Ir-192 plan. However, due to its lower mean energy than the Ir-192 source, an EBS plan has dosimetric and biological features different from an Ir-192 source plan. Current brachytherapy treatment planning methods may have large errors in treatment outcome prediction for an EBS plan. Two main factors contribute to the errors: the dosimetric influence of tissue heterogeneities and the enhancement of relative biological effectiveness (RBE) of electronic brachytherapy. This study quantified the effects of these two factors and revisited the plan quality of electronic brachytherapy APBI. The influence of tissue heterogeneities is studied by a Monte Carlo method and heterogeneous 'virtual patient' phantoms created from CT images and structure contours; the effect of RBE enhancement in the treatment outcome was estimated by biologically effective dose (BED) distribution. Ten electronic brachytherapy APBI cases were studied. The results showed that, for electronic brachytherapy cases, tissue heterogeneities and patient boundary effect decreased dose to the target and skin but increased dose to the bones. On average, the target dose coverage PTV V100 reduced from 95.0% in water phantoms (planned) to only 66.7% in virtual patient phantoms (actual). The actual maximum dose to the ribs is 3.3 times higher than the planned dose; the actual mean dose to the ipsilateral breast and maximum dose to the skin were reduced by 22% and 17%, respectively. Combining the effect of tissue heterogeneities and RBE enhancement, BED coverage of the target was 89.9% in virtual patient phantoms with RBE enhancement (actual BED) as compared to 95.2% in water phantoms without RBE enhancement (planned BED). About 10% increase in the source output is required to raise BED PTV V100 to 95%. As a conclusion, the composite effect of dose reduction in the target due to heterogeneities and RBE enhancement results in a net effect of 5.3% target BED coverage loss for electronic brachytherapy. Therefore, it is suggested that about 10% increase in the source output may be necessary to achieve sufficient target coverage higher than 95%.

Monte Carlo skin dose simulation in intraoperative radiotherapy of breast cancer using spherical applicators.

PubMed

Moradi, F; Ung, N M; Khandaker, M U; Mahdiraji, G A; Saad, M; Abdul Malik, R; Bustam, A Z; Zaili, Z; Bradley, D A

2017-07-28

The relatively new treatment modality electronic intraoperative radiotherapy (IORT) is gaining popularity, irradiation being obtained within a surgically produced cavity being delivered via a low-energy x-ray source and spherical applicators, primarily for early stage breast cancer. Due to the spatially dramatic dose-rate fall off with radial distance from the source and effects related to changes in the beam quality of the low keV photon spectra, dosimetric account of the Intrabeam system is rather complex. Skin dose monitoring in IORT is important due to the high dose prescription per treatment fraction. In this study, modeling of the x-ray source and related applicators were performed using the Monte Carlo N-Particle transport code. The dosimetric characteristics of the model were validated against measured data obtained using an ionization chamber and EBT3 film as dosimeters. By using a simulated breast phantom, absorbed doses to the skin for different combinations of applicator size (1.5-5 cm) and treatment depth (0.5-3 cm) were calculated. Simulation results showed overdosing of the skin (>30% of prescribed dose) at a treatment depth of 0.5 cm using applicator sizes larger than 1.5 cm. Skin doses were significantly increased with applicator size, insofar as delivering 12 Gy (60% of the prescribed dose) to skin for the largest sized applicator (5 cm diameter) and treatment depth of 0.5 cm. It is concluded that the recommended 0.5-1 cm distance between the skin and applicator surface does not guarantee skin safety and skin dose is generally more significant in cases with the larger applicators. • Intrabeam x-ray source and spherical applicators were simulated and skin dose was calculated. • Skin dose for constant skin to applicator distance strongly depends on applicator size. • Use of larger applicators generally results in higher skin dose. • The recommended 0.5-1 cm skin to applicator distance does not guarantee skin safety.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chan, M; Lee, V; Wong, M

Purpose: Following the method of in-phantom measurements of reference air kerma rate (Ka) at 100cm and absorbed water dose rate (Dw1) at 1cm of high-dose-rate 192Ir brachytherapy source using 60Co absorbed-dose-to-water calibrated (ND,w,60Co) ionization chamber (IC), we experimentally determined the in-phantom correction factors (kglob) of the PTW30013 (PTW, Freiburg, Germany) IC by comparing the Monte Carlo (MC)-calculated kglob of the other PTW30016 IC. Methods: The Dw1 formalism of in-phantom measurement is: M*ND,w,60Co*(kglob)Dw1, where M is the collected charges, and (kglob)Dw1 the in-phantom Dw1 correction factor. Similarly, Ka is determined by M*ND,w,60Co*(kglob)ka, where (kglob)ka the in-phantom Ka correction factor. Two thimblemore » ICs PTW30013 and another PTW30016 having a ND,w,60Co from the German primary standard laboratory (PTB) were simultaneously exposed to the microselectron 192Ir v2 source at 8cm in a PMMA phantom. A reference well chamber (PTW33004) with a PTB transfer Ka calibration Nka was used for comparing the in-phantom measurements to derive the experimental (kglob)ka factors. We determined the experimental (kglob)Dw1 of the PTW30013 by comparing the PTW30016 measurements with MC-calculated (kglob)Dw1. Results: Ka results of the PTW30016 based on ND,w,60Co and MC-calculated (kglob)ka differ from the well chamber results based on Nka by 1.6% and from the manufacturer by 1.0%. Experimental (kglob)ka factors for the PTW30016 and two other PTW30013 are 0.00683, 0.00681 and 0.00679, and vary <0.5% with 1mm source positioning uncertainty. Experimental (kglob)Dw1 of the PTW30013 ICs are 75.3 and 75.6, and differ by 1.6% from the conversion by dose rate constant from the AAPM report 229. Conclusion: The 1.7% difference between MC and experimental (kglob)ka for the PTW30016 IC is within the PTB 2.5% expanded uncertainty in Ka calibration standard. Using a single IC with ND,w,60Co to calibrate the brachytherapy source and dose output in external radiotherapy is feasible. MC validation of the PTW30013(kglob)Dw1 is warranted.« less

Low-dose-rate or high-dose-rate brachytherapy in treatment of prostate cancer – between options

PubMed Central

2013-01-01

Purpose Permanent low-dose-rate (LDR-BT) and temporary high-dose-rate (HDR-BT) brachytherapy are competitive techniques for clinically localized prostate radiotherapy. Although a randomized trial will likely never to be conducted comparing these two forms of brachytherapy, a comparative analysis proves useful in understanding some of their intrinsic differences, several of which could be exploited to improve outcomes. The aim of this paper is to look for possible similarities and differences between both brachytherapy modalities. Indications and contraindications for monotherapy and for brachytherapy as a boost to external beam radiation therapy (EBRT) are presented. It is suggested that each of these techniques has attributes that advocates for one or the other. First, they represent the extreme ends of the spectrum with respect to dose rate and fractionation, and therefore have inherently different radiobiological properties. Low-dose-rate brachytherapy has the great advantage of being practically a one-time procedure, and enjoys a long-term follow-up database supporting its excellent outcomes and low morbidity. Low-dose-rate brachytherapy has been a gold standard for prostate brachytherapy in low risk patients since many years. On the other hand, HDR is a fairly invasive procedure requiring several sessions associated with a brief hospital stay. Although lacking in significant long-term data, it possesses the technical advantage of control over its postimplant dosimetry (by modulating the source dwell time and position), which is absent in LDR brachytherapy. This important difference in dosimetric control allows HDR doses to be escalated safely, a flexibility that does not exist for LDR brachytherapy. Conclusions Radiobiological models support the current clinical evidence for equivalent outcomes in localized prostate cancer with either LDR or HDR brachytherapy, using current dose regimens. At present, all available clinical data regarding these two techniques suggests that they are equally effective, stage for stage, in providing high tumor control rates. PMID:23634153

Characterization of the neutron irradiation system for use in the Low-Dose-Rate Irradiation Facility at Sandia National Laboratories.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franco, Manuel

The objective of this work was to characterize the neutron irradiation system consisting of americium-241 beryllium (241AmBe) neutron sources placed in a polyethylene shielding for use at Sandia National Laboratories (SNL) Low Dose Rate Irradiation Facility (LDRIF). With a total activity of 0.3 TBq (9 Ci), the source consisted of three recycled 241AmBe sources of different activities that had been combined into a single source. The source in its polyethylene shielding will be used in neutron irradiation testing of components. The characterization of the source-shielding system was necessary to evaluate the radiation environment for future experiments. Characterization of the sourcemore » was also necessary because the documentation for the three component sources and their relative alignment within the Special Form Capsule (SFC) was inadequate. The system consisting of the source and shielding was modeled using Monte Carlo N-Particle transport code (MCNP). The model was validated by benchmarking it against measurements using multiple techniques. To characterize the radiation fields over the full spatial geometry of the irradiation system, it was necessary to use a number of instruments of varying sensitivities. First, the computed photon radiography assisted in determining orientation of the component sources. With the capsule properly oriented inside the shielding, the neutron spectra were measured using a variety of techniques. A N-probe Microspec and a neutron Bubble Dosimeter Spectrometer (BDS) set were used to characterize the neutron spectra/field in several locations. In the third technique, neutron foil activation was used to ascertain the neutron spectra. A high purity germanium (HPGe) detector was used to characterize the photon spectrum. The experimentally measured spectra and the MCNP results compared well. Once the MCNP model was validated to an adequate level of confidence, parametric analyses was performed on the model to optimize for potential experimental configurations and neutron spectra for component irradiation. The final product of this work is a MCNP model validated by measurements, an overall understanding of neutron irradiation system including photon/neutron transport and effective dose rates throughout the system, and possible experimental configurations for future irradiation of components.« less

Bremsstrahlung versus Monoenergetic Photon Dose and Photonuclear Stimulation Comparisons at Long Standoff Distances

NASA Astrophysics Data System (ADS)

Jones, J. L.; Sterbentz, J. W.; Yoon, W. Y.; Norman, D. R.

2009-12-01

Energetic photon sources with energies greater than 6 MeV continue to be recognized as viable source for various types of inspection applications, especially those related to nuclear and/or explosive material detection. These energetic photons can be produced as a continuum of energies (i.e., bremsstrahlung) or as a set of one or more discrete photon energies (i.e., monoenergetic). This paper will provide a follow-on extension of the photon dose comparison presented at the 9th International Conference on Applications of Nuclear Techniques (June 2008). Our previous paper showed the comparative advantages and disadvantages of the photon doses provided by these two energetic interrogation sources and highlighted the higher energy advantage of the bremsstrahlung source, especially at long standoff distances (i.e., distance from source to the inspected object). This paper will pursue higher energy photon inspection advantage (up to 100 MeV) by providing dose and stimulated photonuclear interaction predictions in air and for an infinitely dilute interrogated material (used for comparative interaction rate assessments since it excludes material self-shielding) as the interrogation object positioned forward on the inspection beam axis at increasing standoff distances. In addition to the direct energetic photon-induced stimulation, the predictions will identify the importance of secondary downscattered/attenuated source-term effects arising from the photon transport in the intervening air environment.

On the experimental validation of model-based dose calculation algorithms for 192Ir HDR brachytherapy treatment planning

NASA Astrophysics Data System (ADS)

Pappas, Eleftherios P.; Zoros, Emmanouil; Moutsatsos, Argyris; Peppa, Vasiliki; Zourari, Kyveli; Karaiskos, Pantelis; Papagiannis, Panagiotis

2017-05-01

There is an acknowledged need for the design and implementation of physical phantoms appropriate for the experimental validation of model-based dose calculation algorithms (MBDCA) introduced recently in 192Ir brachytherapy treatment planning systems (TPS), and this work investigates whether it can be met. A PMMA phantom was prepared to accommodate material inhomogeneities (air and Teflon), four plastic brachytherapy catheters, as well as 84 LiF TLD dosimeters (MTS-100M 1  ×  1  ×  1 mm3 microcubes), two radiochromic films (Gafchromic EBT3) and a plastic 3D dosimeter (PRESAGE). An irradiation plan consisting of 53 source dwell positions was prepared on phantom CT images using a commercially available TPS and taking into account the calibration dose range of each detector. Irradiation was performed using an 192Ir high dose rate (HDR) source. Dose to medium in medium, Dmm , was calculated using the MBDCA option of the same TPS as well as Monte Carlo (MC) simulation with the MCNP code and a benchmarked methodology. Measured and calculated dose distributions were spatially registered and compared. The total standard (k  =  1) spatial uncertainties for TLD, film and PRESAGE were: 0.71, 1.58 and 2.55 mm. Corresponding percentage total dosimetric uncertainties were: 5.4-6.4, 2.5-6.4 and 4.85, owing mainly to the absorbed dose sensitivity correction and the relative energy dependence correction (position dependent) for TLD, the film sensitivity calibration (dose dependent) and the dependencies of PRESAGE sensitivity. Results imply a LiF over-response due to a relative intrinsic energy dependence between 192Ir and megavoltage calibration energies, and a dose rate dependence of PRESAGE sensitivity at low dose rates (<1 Gy min-1). Calculations were experimentally validated within uncertainties except for MBDCA results for points in the phantom periphery and dose levels  <20%. Experimental MBDCA validation is laborious, yet feasible. Further work is required for the full characterization of dosimeter response for 192Ir and the reduction of experimental uncertainties.

Total-dose radiation effects data for semiconductor devices (1989 supplement)

NASA Technical Reports Server (NTRS)

Martin, Keith E.; Coss, James R.; Goben, Charles A.; Shaw, David C.; Farmanesh, Sam; Davarpanah, Michael M.; Craft, Leroy H.; Price, William E.

1990-01-01

Steady state, total dose radiation test data are provided for electronic designers and other personnel using semiconductor devices in a radiation environment. The data are presented in graphic and narrative formats. Two primary radiation source types were used: Cobalt-60 gamma rays and a Dynamitron electron accelerator capable of delivering 2.5 MeV electrons at a steady rate.

Impact of source-production revision on the dose-rate constant of {sup 131}Cs interstitial brachytherapy sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Zhe; Bongiorni, Paul; Nath, Ravinder

2010-07-15

Purpose: Since its introduction in 2004, the model CS-1 Rev.1 {sup 131}Cs source has been used in many radiation therapy clinics for prostate brachytherapy. In 2006, this source model underwent a Rev.2 production revision. The aim of this work was to investigate the dosimetric influences of the Rev.2 production revision using high-resolution photon spectrometry. Methods: Three CS-1 Rev.1 and three CS-1 Rev.2 {sup 131}Cs sources were used in this study. The relative photon energy spectrum emitted by each source in the transverse bisector of the source was measured using a high-resolution germanium detector designed for low-energy photon spectrometry. Based onmore » the measured photon energy spectrum and the radioactivity distribution in the source, the dose-rate constant ({Lambda}) of each source was determined. The effects of the Rev.2 production revision were quantified by comparing the emitted photon energy spectra and the {Lambda} values determined for the sources manufactured before and after the production revision. Results: The relative photon energy spectrum originating from the principal emissions of {sup 131}Cs was found to be nearly identical before and after the Rev.2 revision. However, the portion of the spectrum originating from the production of fluorescent x rays in niobium, a trace element present in the source construction materials, was found to differ significantly between the Rev.1 and Rev.2 sources. The peak intensity of the Nb K{sub {alpha}} and Nb K{sub {beta}} fluorescent x rays from the Rev.2 source was approximately 35% of that from the Rev.1 source. Consequently, the nominal {Lambda} value of the Rev.2 source was found to be greater than that determined for the Rev.1 source by approximately 0.7%{+-}0.5%. Conclusions: A significant reduction (65%) in relative niobium fluorescent x-ray yield was observed in the Rev.2 {sup 131}Cs sources. The impact of this reduction on the dose-rate constant was found to be small, with a relative difference of less than 1%. This study demonstrates that photon spectrometry can be used as a sensitive and convenient tool for monitoring and for quantifying the dosimetric effects of brachytherapy source-production revisions. Because production revision can change both the geometry and the atomic composition of brachytherapy sources, its dosimetric impact should be carefully monitored and evaluated for each production revision.« less

Radiation ecology issues associated with murine rodents and shrews in the Chernobyl exclusion zone.

PubMed

Gaschak, Sergey P; Maklyuk, Yulia A; Maksimenko, Andrey M; Bondarkov, Mikhail D; Jannik, G Timothy; Farfán, Eduardo B

2011-10-01

This article describes major studies performed by the Chernobyl Center's International Radioecology Laboratory (Slavutich, Ukraine) on radioecology of murine rodents and shrews inhabiting the Chernobyl Exclusion Zone. The article addresses the long-term (1986-2005) and seasonal dynamics of radioactive contamination of animals and reviews interspecies differences in radionuclide accumulations and factors affecting the radionuclide accumulations. It is shown that bioavailability of radionuclides in the "soil-to-plant" chain and a trophic specialization of animals play key roles in determining their actual contamination levels. The total absorbed dose rates in small mammals significantly reduced during the years following the Chernobyl Nuclear Power Plant accident. In 1986, the absorbed dose rate reached 1.3-6.0 Gy h(-1) in the central areas of the Chernobyl Exclusion Zone (the "Red Forest"). In 1988 and 1990, the total absorbed dose rates were 1.3 and 0.42 Gy h(-1), respectively. In 1995, 2000, and 2005, according to the present study, the total absorbed dose rates rarely exceeded 0.00023, 0.00018, and 0.00015 Gy h(-1), respectively. Contributions of individual radiation sources into the total absorbed dose are described.

Uncertainty propagation for SPECT/CT-based renal dosimetry in 177Lu peptide receptor radionuclide therapy

NASA Astrophysics Data System (ADS)

Gustafsson, Johan; Brolin, Gustav; Cox, Maurice; Ljungberg, Michael; Johansson, Lena; Sjögreen Gleisner, Katarina

2015-11-01

A computer model of a patient-specific clinical 177Lu-DOTATATE therapy dosimetry system is constructed and used for investigating the variability of renal absorbed dose and biologically effective dose (BED) estimates. As patient models, three anthropomorphic computer phantoms coupled to a pharmacokinetic model of 177Lu-DOTATATE are used. Aspects included in the dosimetry-process model are the gamma-camera calibration via measurement of the system sensitivity, selection of imaging time points, generation of mass-density maps from CT, SPECT imaging, volume-of-interest delineation, calculation of absorbed-dose rate via a combination of local energy deposition for electrons and Monte Carlo simulations of photons, curve fitting and integration to absorbed dose and BED. By introducing variabilities in these steps the combined uncertainty in the output quantity is determined. The importance of different sources of uncertainty is assessed by observing the decrease in standard deviation when removing a particular source. The obtained absorbed dose and BED standard deviations are approximately 6% and slightly higher if considering the root mean square error. The most important sources of variability are the compensation for partial volume effects via a recovery coefficient and the gamma-camera calibration via the system sensitivity.

Dose assessment for various coals in the coal-fired power plant

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antic, D.; Sokcic-Kostic, M.

1993-01-01

The radiation exposure of the public in the vicinity of a coal-fired power plant has been studied. The experimental data on uranium, thorium, and potassium content in selected coals from Serbia and Bosnia have been used to calculate the release rates of natural radionuclides from the power plant. A generalized model for analysis of radiological impact of an energy source that includes the two-dimensional version of the cloud model simulates the transport of radionuclides released to the atmosphere. The inhalation dose rates are assessed for various meteorological conditions.

Radiation Therapy for Cancer

MedlinePlus

... 1 , 12 ). In high-dose-rate treatment, a robotic machine attached to delivery tubes placed inside the ... with breast cancer who have undergone breast-conserving surgery . The placement of brachytherapy sources can be temporary ...

Technical Note: On maximizing Cherenkov emissions from medical linear accelerators.

PubMed

Shrock, Zachary; Yoon, Suk W; Gunasingha, Rathnayaka; Oldham, Mark; Adamson, Justus

2018-04-19

Cherenkov light during MV radiotherapy has recently found imaging and therapeutic applications but is challenged by relatively low fluence. Our purpose is to investigate the feasibility of increasing Cherenkov light production during MV radiotherapy by increasing photon energy and applying specialized beam-hardening filtration. GAMOS 5.0.0, a GEANT4-based framework for Monte Carlo simulations, was used to model standard clinical linear accelerator primary photon beams. The photon source was incident upon a 17.8 cm 3 cubic water phantom with a 94 cm source to surface distance. Dose and Cherenkov production was determined at depths of 3-9 cm. Filtration was simulated 15 cm below the photon beam source. Filter materials included aluminum, iron, and copper with thicknesses of 2-20 cm. Histories used depended on the level of attenuation from the filter, ranging from 100 million to 2 billion. Comparing average dose per history also allowed for evaluation of dose-rate reduction for different filters. Overall, increasing photon beam energy is more effective at improving Cherenkov production per unit dose than is filtration, with a standard 18 MV beam yielding 3.3-4.0× more photons than 6 MV. Introducing an aluminum filter into an unfiltered 2400 cGy/min 10 MV beam increases the Cherenkov production by 1.6-1.7×, while maintaining a clinical dose rate of 300 cGy/min, compared to increases of ~1.5× for iron and copper. Aluminum was also more effective than the standard flattening filter, with the increase over the unfiltered beam being 1.4-1.5× (maintaining 600 cGy/min dose rate) vs 1.3-1.4× for the standard flattening filter. Applying a 10 cm aluminum filter to a standard 18 MV, photon beam increased the Cherenkov production per unit dose to 3.9-4.3× beyond that of 6 MV (vs 3.3-4.0× for 18 MV with no aluminum filter). Through a combination of increasing photon energy and applying specialized beam-hardening filtration, the amount of Cherenkov photons per unit radiotherapy dose can be increased substantially. © 2018 American Association of Physicists in Medicine.

Performance characteristics of the MIT fission converter based epithermal neutron beam.

PubMed

Riley, K J; Binns, P J; Harling, O K

2003-04-07

A pre-clinical characterization of the first fission converter based epithermal neutron beam (FCB) designed for boron neutron capture therapy (BNCT) has been performed. Calculated design parameters describing the physical performance of the aluminium and Teflon filtered beam were confirmed from neutron fluence and absorbed dose rate measurements performed with activation foils and paired ionization chambers. The facility currently provides an epithermal neutron flux of 4.6 x 10(9) n cm(-2) s(-1) in-air at the patient position that makes it the most intense BNCT source in the world. This epithermal neutron flux is accompanied by very low specific photon and fast neutron absorbed doses of 3.5 +/- 0.5 and 1.4 +/- 0.2 x 10(-13) Gy cm2, respectively. A therapeutic dose rate of 1.7 RBE Gy min(-1) is achievable at the advantage depth of 97 mm when boronated phenylalanine (BPA) is used as the delivery agent, giving an average therapeutic ratio of 5.7. In clinical trials of normal tissue tolerance when using the FCB, the effective prescribed dose is due principally to neutron interactions with the nonselectively absorbed BPA present in brain. If an advanced compound is considered, the dose to brain would instead be predominately from the photon kerma induced by thermal neutron capture in hydrogen and advantage parameters of 0.88 Gy min(-1), 121 mm and 10.8 would be realized for the therapeutic dose rate, advantage depth and therapeutic ratio, respectively. This study confirms the success of a new approach to producing a high intensity, high purity epithermal neutron source that attains near optimal physical performance and which is well suited to exploit the next generation of boron delivery agents.

Ion-recombination correction for different ionization chambers in high dose rate flattening-filter-free photon beams

NASA Astrophysics Data System (ADS)

Lang, Stephanie; Hrbacek, Jan; Leong, Aidan; Klöck, Stephan

2012-05-01

Recently, there has been an increased interest in flattening-filter-free (FFF) linear accelerators. Removal of the filter results in available dose rates up to 24 Gy min-1 (for nominal energy 10 MV in depth of maximum dose, a source-surface distance of 100 cm and a field size of 10×10 cm2). To guarantee accurate relative and reference dosimetry for the FFF beams, we investigated the charge collection efficiency of multiple air-vented and one liquid ionization chamber for dose rates up to 31.9 Gy min-1. For flattened beams, the ion-collection efficiency of all air-vented ionization chambers (except for the PinPoint chamber) was above 0.995. By removing the flattening filter, we found a reduction in collection efficiency of approximately 0.5-0.9% for a 10 MV beam. For FFF beams, the Markus chamber showed the largest collection efficiency of 0.994. The observed collection efficiencies were dependent on dose per pulse, but independent of the pulse repetition frequency. Using the liquid ionization chamber, the ion-collection efficiency for flattened beams was above 0.990 for all dose rates. However, this chamber showed a low collection efficiency of 0.940 for the FFF 10 MV beam at a dose rate of 31.9 Gy min-1. All investigated air-vented ionization chambers can be reliably used for relative dosimetry of FFF beams. The order of correction for reference dosimetry is given in the manuscript. Due to their increased saturation in high dose rate FFF beams, liquid ionization chambers appear to be unsuitable for dosimetry within these contexts.

Modification and validation of an analytical source model for external beam radiotherapy Monte Carlo dose calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davidson, Scott E., E-mail: sedavids@utmb.edu

Purpose: A dose calculation tool, which combines the accuracy of the dose planning method (DPM) Monte Carlo code and the versatility of a practical analytical multisource model, which was previously reported has been improved and validated for the Varian 6 and 10 MV linear accelerators (linacs). The calculation tool can be used to calculate doses in advanced clinical application studies. One shortcoming of current clinical trials that report dose from patient plans is the lack of a standardized dose calculation methodology. Because commercial treatment planning systems (TPSs) have their own dose calculation algorithms and the clinical trial participant who usesmore » these systems is responsible for commissioning the beam model, variation exists in the reported calculated dose distributions. Today’s modern linac is manufactured to tight specifications so that variability within a linac model is quite low. The expectation is that a single dose calculation tool for a specific linac model can be used to accurately recalculate dose from patient plans that have been submitted to the clinical trial community from any institution. The calculation tool would provide for a more meaningful outcome analysis. Methods: The analytical source model was described by a primary point source, a secondary extra-focal source, and a contaminant electron source. Off-axis energy softening and fluence effects were also included. The additions of hyperbolic functions have been incorporated into the model to correct for the changes in output and in electron contamination with field size. A multileaf collimator (MLC) model is included to facilitate phantom and patient dose calculations. An offset to the MLC leaf positions was used to correct for the rudimentary assumed primary point source. Results: Dose calculations of the depth dose and profiles for field sizes 4 × 4 to 40 × 40 cm agree with measurement within 2% of the maximum dose or 2 mm distance to agreement (DTA) for 95% of the data points tested. The model was capable of predicting the depth of the maximum dose within 1 mm. Anthropomorphic phantom benchmark testing of modulated and patterned MLCs treatment plans showed agreement to measurement within 3% in target regions using thermoluminescent dosimeters (TLD). Using radiochromic film normalized to TLD, a gamma criteria of 3% of maximum dose and 2 mm DTA was applied with a pass rate of least 85% in the high dose, high gradient, and low dose regions. Finally, recalculations of patient plans using DPM showed good agreement relative to a commercial TPS when comparing dose volume histograms and 2D dose distributions. Conclusions: A unique analytical source model coupled to the dose planning method Monte Carlo dose calculation code has been modified and validated using basic beam data and anthropomorphic phantom measurement. While this tool can be applied in general use for a particular linac model, specifically it was developed to provide a singular methodology to independently assess treatment plan dose distributions from those clinical institutions participating in National Cancer Institute trials.« less

/sup 125/I interstitial implants in the RIF-1 murine flank tumor: an animal model for brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bernstein, M.; Gutin, P.H.; Weaver, D.A.

1982-09-01

The development of a model for interstitial brachytherapy that uses high-activity, removable /sup 125/I sources in the RIF-1 murine flank tumor is reported. Experimental end points are clonogenic cell and tumor regrowth delay assays. For the clonogenic cell assay, interestitial radiation is delivered at total doses of 500-10,000 rad at dose rates of 0.9-2.7 rad/min to cells in annuli of tissue in the tumor. Dose-survival curves are characterized by an initial shoulder followed by a straight (exponential) portion, with D/sub 0/ similar to that of the curve obtained by external irradiation of the RIF-1 tumor in a self-contained cesium irradiatormore » at similar dose rates. Tumor regrowth curves have been obtained for minimum tumor doses of 500-5000 rad; marked tumor regression has been observed with minimum tumor doses as low as 2000 rad, but results are not as reproducible as the results obtained with the clonogenic cell assay.« less

Dose reduction in LDR brachytherapy by implanted prostate gold fiducial markers.

PubMed

Landry, Guillaume; Reniers, Brigitte; Lutgens, Ludy; Murrer, Lars; Afsharpour, Hossein; de Haas-Kock, Danielle; Visser, Peter; van Gils, Francis; Verhaegen, Frank

2012-03-01

The dosimetric impact of gold fiducial markers (FM) implanted prior to external beam radiotherapy of prostate cancer on low dose rate (LDR) brachytherapy seed implants performed in the context of combined therapy was investigated. A virtual water phantom was designed containing a single FM. Single and multi source scenarios were investigated by performing Monte Carlo dose calculations, along with the influence of varying orientation and distance of the FM with respect to the sources. Three prostate cancer patients treated with LDR brachytherapy for a recurrence following external beam radiotherapy with implanted FM were studied as surrogate cases to combined therapy. FM and brachytherapy seeds were identified on post implant CT scans and Monte Carlo dose calculations were performed with and without FM. The dosimetric impact of the FM was evaluated by quantifying the amplitude of dose shadows and the volume of cold spots. D(90) was reported based on the post implant CT prostate contour. Large shadows are observed in the single source-FM scenarios. As expected from geometric considerations, the shadows are dependent on source-FM distance and orientation. Large dose reductions are observed at the distal side of FM, while at the proximal side a dose enhancement is observed. In multisource scenarios, the importance of shadows appears mitigated, although FM at the periphery of the seed distribution caused underdosage (

Monte Carlo study of the impact of a magnetic field on the dose distribution in MRI-guided HDR brachytherapy using Ir-192

NASA Astrophysics Data System (ADS)

Beld, E.; Seevinck, P. R.; Lagendijk, J. J. W.; Viergever, M. A.; Moerland, M. A.

2016-09-01

In the process of developing a robotic MRI-guided high-dose-rate (HDR) prostate brachytherapy treatment, the influence of the MRI scanner’s magnetic field on the dose distribution needs to be investigated. A magnetic field causes a deflection of electrons in the plane perpendicular to the magnetic field, and it leads to less lateral scattering along the direction parallel with the magnetic field. Monte Carlo simulations were carried out to determine the influence of the magnetic field on the electron behavior and on the total dose distribution around an Ir-192 source. Furthermore, the influence of air pockets being present near the source was studied. The Monte Carlo package Geant4 was utilized for the simulations. The simulated geometries consisted of a simplified point source inside a water phantom. Magnetic field strengths of 0 T, 1.5 T, 3 T, and 7 T were considered. The simulation results demonstrated that the dose distribution was nearly unaffected by the magnetic field for all investigated magnetic field strengths. Evidence was found that, from a dose perspective, the HDR prostate brachytherapy treatment using Ir-192 can be performed safely inside the MRI scanner. No need was found to account for the magnetic field during treatment planning. Nevertheless, the presence of air pockets in close vicinity to the source, particularly along the direction parallel with the magnetic field, appeared to be an important point for consideration.

Monte Carlo study of the impact of a magnetic field on the dose distribution in MRI-guided HDR brachytherapy using Ir-192.

PubMed

Beld, E; Seevinck, P R; Lagendijk, J J W; Viergever, M A; Moerland, M A

2016-09-21

In the process of developing a robotic MRI-guided high-dose-rate (HDR) prostate brachytherapy treatment, the influence of the MRI scanner's magnetic field on the dose distribution needs to be investigated. A magnetic field causes a deflection of electrons in the plane perpendicular to the magnetic field, and it leads to less lateral scattering along the direction parallel with the magnetic field. Monte Carlo simulations were carried out to determine the influence of the magnetic field on the electron behavior and on the total dose distribution around an Ir-192 source. Furthermore, the influence of air pockets being present near the source was studied. The Monte Carlo package Geant4 was utilized for the simulations. The simulated geometries consisted of a simplified point source inside a water phantom. Magnetic field strengths of 0 T, 1.5 T, 3 T, and 7 T were considered. The simulation results demonstrated that the dose distribution was nearly unaffected by the magnetic field for all investigated magnetic field strengths. Evidence was found that, from a dose perspective, the HDR prostate brachytherapy treatment using Ir-192 can be performed safely inside the MRI scanner. No need was found to account for the magnetic field during treatment planning. Nevertheless, the presence of air pockets in close vicinity to the source, particularly along the direction parallel with the magnetic field, appeared to be an important point for consideration.

Luminescence isochron dating: a new approach using different grain sizes.

PubMed

Zhao, H; Li, S H

2002-01-01

A new approach to isochron dating is described using different sizes of quartz and K-feldspar grains. The technique can be applied to sites with time-dependent external dose rates. It is assumed that any underestimation of the equivalent dose (De) using K-feldspar is by a factor F, which is independent of grain size (90-350 microm) for a given sample. Calibration of the beta source for different grain sizes is discussed, and then the sample ages are calculated using the differences between quartz and K-feldspar De from grains of similar size. Two aeolian sediment samples from north-eastern China are used to illustrate the application of the new method. It is confirmed that the observed values of De derived using K-feldspar underestimate the expected doses (based on the quartz De) but, nevertheless, these K-feldspar De values correlate linearly with the calculated internal dose rate contribution, supporting the assumption that the underestimation factor F is independent of grain size. The isochron ages are also compared with the results obtained using quartz De and the measured external dose rates.

Brachytherapy devices and methods employing americium-241

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gray, L. A.

1985-04-16

Sources and methods for radiation therapy, particularly brachytherapy, employing americium-241 (60 keV gamma emission and 433 year half-life) provide major advantages for radiotherapy, including simplified radiation protection, dose reduction to healthy tissue, increased dose to tumor, and improved dose distributions. A number of apparent drawbacks and unfavorable considerations including low gamma factor, high self-absorption, increased activity required and alpha-particle generation leading to helium gas pressure buildup and potential neutron contamination in the generated radiation are all effectively dealt with and overcome through recognition of subtle favorable factors unique to americium-241 among brachytherapy sources and through suitable constructional techniques. Due tomore » an additional amount of radiation, in the order of 50%, provided primarily to nearby regions as a result of Compton scatter in tissue and water, higher dose rates occur than would be predicted by conventional calculations.« less

Mathematical optimization of high dose-rate brachytherapy—derivation of a linear penalty model from a dose-volume model

NASA Astrophysics Data System (ADS)

Morén, B.; Larsson, T.; Carlsson Tedgren, Å.

2018-03-01

High dose-rate brachytherapy is a method for cancer treatment where the radiation source is placed within the body, inside or close to a tumour. For dose planning, mathematical optimization techniques are being used in practice and the most common approach is to use a linear model which penalizes deviations from specified dose limits for the tumour and for nearby organs. This linear penalty model is easy to solve, but its weakness lies in the poor correlation of its objective value and the dose-volume objectives that are used clinically to evaluate dose distributions. Furthermore, the model contains parameters that have no clear clinical interpretation. Another approach for dose planning is to solve mixed-integer optimization models with explicit dose-volume constraints which include parameters that directly correspond to dose-volume objectives, and which are therefore tangible. The two mentioned models take the overall goals for dose planning into account in fundamentally different ways. We show that there is, however, a mathematical relationship between them by deriving a linear penalty model from a dose-volume model. This relationship has not been established before and improves the understanding of the linear penalty model. In particular, the parameters of the linear penalty model can be interpreted as dual variables in the dose-volume model.

Verification of the radiometric map of the Czech Republic.

PubMed

Matolín, Milan

2017-01-01

The radiometric map of the Czech Republic is based on uniform regional airborne radiometric total count measurements (1957-1959) which covered 100% of the country. The airborne radiometric instrument was calibrated to a 226 Ra point source. The calibration facility for field gamma-ray spectrometers, established in the Czech Republic in 1975, significantly contributed to the subsequent radiometric data standardization. In the 1990's, the original analogue airborne radiometric data were digitized and using the method of back-calibration (IAEA, 2003) converted to dose rate. The map of terrestrial gamma radiation expressed in dose rate (nGy/h) was published on the scale 1:500,000 in 1995. Terrestrial radiation in the Czech Republic, formed by magmatic, sedimentary and metamorphic rocks of Proterozoic to Quaternary age, ranges mostly from 6 to 245 nGy/h, with a mean of 65.6 ± 19.0 nGy/h. The elevated terrestrial radiation in the Czech Republic, in comparison to the global dose rate average of 54 nGy/h, reflects an enhanced content of natural radioactive elements in the rocks. The 1995 published radiometric map of the Czech Republic was successively studied and verified by additional ground gamma-ray spectrometric measurements and by comparison to radiometric maps of Germany, Poland and Slovakia in border zones. A ground dose rate intercomparison measurement under participation of foreign and domestic professional institutions revealed mutual dose rate deviations about 20 nGy/h and more due to differing technical parameters of applied radiometric instruments. Studies and verification of the radiometric map of the Czech Republic illustrate the magnitude of current deviations in dose rate data. This gained experience can assist in harmonization of dose rate data on the European scale. Copyright © 2016 Elsevier Ltd. All rights reserved.

Sensory evaluation by gamma radiation effect on protein allergen of laying hen eggs

NASA Astrophysics Data System (ADS)

Harder, M. N. C.; Arthur, V.; Perina, V. C. S.; Silva, L. C. A. S.; Bortoleto, G. G.

2012-08-01

Although considered the most complete food and nutritionally shown to be part of a healthy diet, the egg is the source of many eating disorders, especially for infants. Irradiation has been used in studies not only as a means of microbiological control, but also on its structural action in the substances molecules and has been used to reduce the allergenic effects. The aim of this study was to evaluate the sensory effects of Co60 gamma radiation on proteins, enabling the acceptability of allergy food for genetically intolerant people. Eggs commercial fresh and freeze-dried and subjected to gamma irradiation by Co60 source at doses 0 (control), 10 kGy; 20 kGy and 30 kGy and rates of doses of 19.4 kGy/h and 31.8 kGy/h. Acceptability test was used by the hedonic scale, since it is necessary to know the "affective status" of consumers for the product, implying a preference, i.e. the most preferred samples are the most accepted and vice versa. The samples were presented as the habit of consumption (cooked) to a group of 41 adults panelists of both gender, aged from 21 to 40 years, and served under complete block design balanced with respect to the order of presentation. The evaluated attributes was flavor, appearance and overall acceptability. In general, for boiled eggs and freeze-dried, it was observed that the control sample was the most acceptable, followed by the sample irradiated with 10 kGy in both dose rates. In addition, panelists presented in testimony that they found interesting changes due to irradiation; also said they would not buy the product because of the marked change in appearance and smell, which at one point he ended up in disgust and detract from sales of the product, but they would buy irradiated with 10 kGy in both dose rate and dose of 20 kGy at a dose rate of 19.4 kGy/h.

The radiological exposure of man from radioactivity in the Baltic Sea.

PubMed

Nielsen, S P; Bengtson, P; Bojanowsky, R; Hagel, P; Herrmann, J; Ilus, E; Jakobson, E; Motiejunas, S; Panteleev, Y; Skujina, A; Suplinska, M

1999-09-30

A radiological assessment has been carried out considering discharges of radioactivity to the Baltic Sea marine environment since 1950. The sources of radioactivity that have been evaluated are atmospheric nuclear-weapons fallout, fallout from the Chernobyl accident in 1986, discharges of radionuclides from Sellafield and La Hague transported into the Baltic Sea, and discharges of radionuclides from nuclear installations located in the Baltic Sea area. Dose rates from man-made radioactivity to individual members of the public (critical groups) have been calculated based on annual intake of seafood and beach occupancy time. The dose rates to individuals from the regions of the Bothnian Sea and Gulf of Finland are predicted to be larger than from any other area in the Baltic Sea due to the pattern of Chernobyl fallout. The dose rates are predicted to have peaked in 1986 at a value of 0.2 mSv year-1. Collective committed doses to members of the public have been calculated based on fishery statistics and predicted concentrations of radionuclides in biota and coastal sediments. The total collective dose from man-made radioactivity in the Baltic Sea is estimated at 2600 manSv, of which approximately two-thirds originate from Chernobyl fallout, approximately one-quarter from atmospheric nuclear-weapons fallout, approximately 8% from European reprocessing facilities, and approximately 0.04% from nuclear installations bordering the Baltic Sea area. An assessment of small-scale dumping of low-level radioactive waste in the Baltic Sea in the 1960s by Sweden and the Soviet Union has showed that doses to man from these activities are negligible. Dose rates and doses from natural radioactivity dominate except for the year 1986 where dose rates to individuals from Chernobyl fallout in some regions of the Baltic Sea approached those from natural radioactivity.

Calculated organ doses using Monte Carlo simulations in a reference male phantom undergoing HDR brachytherapy applied to localized prostate carcinoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Candela-Juan, Cristian; Perez-Calatayud, Jose; Ballester, Facundo

Purpose: The aim of this study was to obtain equivalent doses in radiosensitive organs (aside from the bladder and rectum) when applying high-dose-rate (HDR) brachytherapy to a localized prostate carcinoma using {sup 60}Co or {sup 192}Ir sources. These data are compared with results in a water phantom and with expected values in an infinite water medium. A comparison with reported values from proton therapy and intensity-modulated radiation therapy (IMRT) is also provided. Methods: Monte Carlo simulations in Geant4 were performed using a voxelized phantom described in International Commission on Radiological Protection (ICRP) Publication 110, which reproduces masses and shapes frommore » an adult reference man defined in ICRP Publication 89. Point sources of {sup 60}Co or {sup 192}Ir with photon energy spectra corresponding to those exiting their capsules were placed in the center of the prostate, and equivalent doses per clinical absorbed dose in this target organ were obtained in several radiosensitive organs. Values were corrected to account for clinical circumstances with the source located at various positions with differing dwell times throughout the prostate. This was repeated for a homogeneous water phantom. Results: For the nearest organs considered (bladder, rectum, testes, small intestine, and colon), equivalent doses given by {sup 60}Co source were smaller (8%-19%) than from {sup 192}Ir. However, as the distance increases, the more penetrating gamma rays produced by {sup 60}Co deliver higher organ equivalent doses. The overall result is that effective dose per clinical absorbed dose from a {sup 60}Co source (11.1 mSv/Gy) is lower than from a {sup 192}Ir source (13.2 mSv/Gy). On the other hand, equivalent doses were the same in the tissue and the homogeneous water phantom for those soft tissues closer to the prostate than about 30 cm. As the distance increased, the differences of photoelectric effect in water and soft tissue, and appearance of other materials such as air, bone, or lungs, produced variations between both phantoms which were at most 35% in the considered organ equivalent doses. Finally, effective doses per clinical absorbed dose from IMRT and proton therapy were comparable to those from both brachytherapy sources, with brachytherapy being advantageous over external beam radiation therapy for the furthest organs. Conclusions: A database of organ equivalent doses when applying HDR brachytherapy to the prostate with either {sup 60}Co or {sup 192}Ir is provided. According to physical considerations, {sup 192}Ir is dosimetrically advantageous over {sup 60}Co sources at large distances, but not in the closest organs. Damage to distant healthy organs per clinical absorbed dose is lower with brachytherapy than with IMRT or protons, although the overall effective dose per Gy given to the prostate seems very similar. Given that there are several possible fractionation schemes, which result in different total amounts of therapeutic absorbed dose, advantage of a radiation treatment (according to equivalent dose to healthy organs) is treatment and facility dependent.« less

Brachytherapy dosimetry of 125I and 103Pd sources using an updated cross section library for the MCNP Monte Carlo transport code.

PubMed

Bohm, Tim D; DeLuca, Paul M; DeWerd, Larry A

2003-04-01

Permanent implantation of low energy (20-40 keV) photon emitting radioactive seeds to treat prostate cancer is an important treatment option for patients. In order to produce accurate implant brachytherapy treatment plans, the dosimetry of a single source must be well characterized. Monte Carlo based transport calculations can be used for source characterization, but must have up to date cross section libraries to produce accurate dosimetry results. This work benchmarks the MCNP code and its photon cross section library for low energy photon brachytherapy applications. In particular, we calculate the emitted photon spectrum, air kerma, depth dose in water, and radial dose function for both 125I and 103Pd based seeds and compare to other published results. Our results show that MCNP's cross section library differs from recent data primarily in the photoelectric cross section for low energies and low atomic number materials. In water, differences as large as 10% in the photoelectric cross section and 6% in the total cross section occur at 125I and 103Pd photon energies. This leads to differences in the dose rate constant of 3% and 5%, and differences as large as 18% and 20% in the radial dose function for the 125I and 103Pd based seeds, respectively. Using a partially updated photon library, calculations of the dose rate constant and radial dose function agree with other published results. Further, the use of the updated photon library allows us to verify air kerma and depth dose in water calculations performed using MCNP's perturbation feature to simulate updated cross sections. We conclude that in order to most effectively use MCNP for low energy photon brachytherapy applications, we must update its cross section library. Following this update, the MCNP code system will be a very effective tool for low energy photon brachytherapy dosimetry applications.

Calculations of the skyshine gamma-ray dose rates from independent spent fuel storage installations (ISFSI) under worst case accident conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pace, J.V. III; Cramer, S.N.; Knight, J.R.

1980-09-01

Calculations of the skyshine gamma-ray dose rates from three spent fuel storage pools under worst case accident conditions have been made using the discrete ordinates code DOT-IV and the Monte Carlo code MORSE and have been compared to those of two previous methods. The DNA 37N-21G group cross-section library was utilized in the calculations, together with the Claiborne-Trubey gamma-ray dose factors taken from the same library. Plots of all results are presented. It was found that the dose was a strong function of the iron thickness over the fuel assemblies, the initial angular distribution of the emitted radiation, and themore » photon source near the top of the assemblies. 16 refs., 11 figs., 7 tabs.« less

Absolute dose calibration of an X-ray system and dead time investigations of photon-counting techniques

NASA Astrophysics Data System (ADS)

Carpentieri, C.; Schwarz, C.; Ludwig, J.; Ashfaq, A.; Fiederle, M.

2002-07-01

High precision concerning the dose calibration of X-ray sources is required when counting and integrating methods are compared. The dose calibration for a dental X-ray tube was executed with special dose calibration equipment (dosimeter) as function of exposure time and rate. Results were compared with a benchmark spectrum and agree within ±1.5%. Dead time investigations with the Medipix1 photon-counting chip (PCC) have been performed by rate variations. Two different types of dead time, paralysable and non-paralysable will be discussed. The dead time depends on settings of the front-end electronics and is a function of signal height, which might lead to systematic defects of systems. Dead time losses in excess of 30% have been found for the PCC at 200 kHz absorbed photons per pixel.

Reload of an industrial cylindrical cobalt source rack

NASA Astrophysics Data System (ADS)

Gharbi, F.; Kadri, O.; Trabelsi, A.

2006-10-01

This work presents a Monte Carlo study of the cylindrical cobalt source rack geometry of the Tunisian gamma irradiation facility, using the GEANT code developed at CERN. The study investigates the question of the reload of the source rack. The studied configurations consist in housing four new cobalt pencils, two in the upper and two in the lower cylinder of the source rack. Global dose rate uniformity inside a "dummy" product for the case of routine and nonroutine irradiation, and as function of the product bulk density, was calculated for eight hypothetical configurations. The same calculation was also performed for both of the original and the ideal (but not practical) configurations. It was shown that hypothetical cases produced dose uniformity variations, according to product density, that were statistically no different than the original and the ideal configurations and that the reload procedure cannot improve the irradiation quality inside the facilities using cylindrical cobalt source racks.

SU-G-201-16: Thermal Imaging in Source Visualization and Radioactivity Measurement for High Dose Rate Brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, X; Lei, Y; Zheng, D

2016-06-15

Purpose: High Dose Rate (HDR) brachytherapy poses a special challenge to radiation safety and quality assurance (QA) due to its high radioactivity, and it is thus critical to verify the HDR source location and its radioactive strength. This study demonstrates a new method for measuring HDR source location and radioactivity utilizing thermal imaging. A potential application would relate to HDR QA and safety improvement. Methods: Heating effects by an HDR source were studied using Finite Element Analysis (FEA). Thermal cameras were used to visualize an HDR source inside a plastic applicator made of polyvinylidene difluoride (PVDF). Using different source dwellmore » times, correlations between the HDR source strength and heating effects were studied, thus establishing potential daily QA criteria using thermal imaging Results: For an Ir1?2 source with a radioactivity of 10 Ci, the decay-induced heating power inside the source is ∼13.3 mW. After the HDR source was extended into the PVDF applicator and reached thermal equilibrium, thermal imaging visualized the temperature gradient of 10 K/cm along the PVDF applicator surface, which agreed with FEA modeling. For Ir{sup 192} source activities ranging from 4.20–10.20 Ci, thermal imaging could verify source activity with an accuracy of 6.3% with a dwell time of 10 sec, and an accuracy of 2.5 % with 100 sec. Conclusion: Thermal imaging is a feasible tool to visualize HDR source dwell positions and verify source integrity. Patient safety and treatment quality will be improved by integrating thermal measurements into HDR QA procedures.« less

Calculations vs. Measurements for Remnant Dose Rates from SNS Spent Structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Popova, Irina I.; Gallmeier, Franz X.; Trotter, Steven M.

The Spallation Neutron Source (SNS) in Oak Ridge, Tennessee, is an accelerator driven neutron scattering facility for materials research. Presently SNS is capable to operate at 1.4 MW proton beam power incident on a mercury target with a proton beam energy of 1 GeV and 60 Hz repetition rate. SNS target system components are periodically replaced because they reach their end-of-life due to radiation induced material damage. Target vessel, which houses mercury target, is exchanged about two-three times per year and the proton beam window (PBW) is exchanged every two – three years.Each spent structure that leaves the SNS sitemore » requires supporting documentation with radionuclide inventory and dose rate prediction for the time of the transportation. Neutronics analyses are performed, assuming realistic irradiation history and decay case to ensure that the container/package, housing the structure, is compliant with the waste management regulations. Analyses are complex due to geometry, multi-code usage and following data treatment.To validate analyses, measurements of dose rates from the spent target vessel # 13 and PBW module #5 were performed. Neutronics analyses were performed to calculate residual dose rates from both structures for the time of measurements.« less

An environmental-level, real-time, pulsed photon dosemeter.

PubMed

Olsher, R H; Frymire, A; Gregoire, T

2005-01-01

Radiation sources producing short pulses of photon radiation are widespread. Such sources include electron linear accelerators and field emission impulse generators. It is often desirable to measure leakage and skyshine radiation for these sources in real time and at environmental levels as low as 0.02 microSv per pulse. This note provides an overview of the design and performance of a commercial, real-time, pulsed photon dosemeter (PPD) capable of single-pulse dose measurements over the range from 0.02 to 20 microSv. The PPD may also be operated in a multiple-pulse mode that integrates the dose from a train of pulses over a 3 s period. A pulse repetition rate of up to 300 Hz is accommodated.

SXTF Instrumentation Definition.

DTIC Science & Technology

1978-05-31

Reference 53. 3.3.2 Multipactor Jectron Sowrces I The multipactor source (Ref 54) has attractive features for application to space - craft charging ...The effect of high 9 energy electrons impinging on the cables can be minimized by shielding them with a sufficient thickness of dielectric . Of the...encountered because of dielectric charging of insulating surfaces, dose and dose rate problems caused by the high energy electron component penetrating

Electronic Subsystem Analysis (ESA)

DTIC Science & Technology

1977-01-01

than aluminum for the gate material, 0 Ion implanted source and draia regions, 0 Dielectrically isolated transistors. The use of a doped polysilicon gate...second level of interconnect ( polysilicon ). Ion implantation is essentially a precisely controllable pre-deposition of the required dopants. It’s use...discussed below). Radiation effects on MOS devices include the following: 0 Total Dose ol Dose Rate o Neutrons Because MOS technology is based on

Validating Fricke dosimetry for the measurement of absorbed dose to water for HDR 192Ir brachytherapy: a comparison between primary standards of the LCR, Brazil, and the NRC, Canada.

PubMed

Salata, Camila; David, Mariano Gazineu; de Almeida, Carlos Eduardo; El Gamal, Islam; Cojocaru, Claudiu; Mainegra-Hing, Ernesto; McEwen, Malcom

2018-04-05

Two Fricke-based absorbed dose to water standards for HDR Ir-192 dosimetry, developed independently by the LCR in Brazil and the NRC in Canada have been compared. The agreement in the determination of the dose rate from a HDR Ir-192 source at 1 cm in a water phantom was found to be within the k  =  1 combined measurement uncertainties of the two standards: D NRC /D LCR   =  1.011, standard uncertainty  =  2.2%. The dose-based standards also agreed within the uncertainties with the manufacturer's stated dose rate value, which is traceable to a national standard of air kerma. A number of possible influence quantities were investigated, including the specific method for producing the ferrous-sulphate Fricke solution, the geometry of the holder, and the Monte Carlo code used to determine correction factors. The comparison highlighted the lack of data on the determination of G(Fe 3+ ) in this energy range and the possibilities for further development of the holders used to contain the Fricke solution. The comparison also confirmed the suitability of Fricke dosimetry for Ir-192 primary standard dose rate determinations at therapy dose levels.

Validating Fricke dosimetry for the measurement of absorbed dose to water for HDR 192Ir brachytherapy: a comparison between primary standards of the LCR, Brazil, and the NRC, Canada

NASA Astrophysics Data System (ADS)

Salata, Camila; Gazineu David, Mariano; de Almeida, Carlos Eduardo; El Gamal, Islam; Cojocaru, Claudiu; Mainegra-Hing, Ernesto; McEwen, Malcom

2018-04-01

Two Fricke-based absorbed dose to water standards for HDR Ir-192 dosimetry, developed independently by the LCR in Brazil and the NRC in Canada have been compared. The agreement in the determination of the dose rate from a HDR Ir-192 source at 1 cm in a water phantom was found to be within the k  =  1 combined measurement uncertainties of the two standards: D NRC/D LCR  =  1.011, standard uncertainty  =  2.2%. The dose-based standards also agreed within the uncertainties with the manufacturer’s stated dose rate value, which is traceable to a national standard of air kerma. A number of possible influence quantities were investigated, including the specific method for producing the ferrous-sulphate Fricke solution, the geometry of the holder, and the Monte Carlo code used to determine correction factors. The comparison highlighted the lack of data on the determination of G(Fe3+) in this energy range and the possibilities for further development of the holders used to contain the Fricke solution. The comparison also confirmed the suitability of Fricke dosimetry for Ir-192 primary standard dose rate determinations at therapy dose levels.

Nuclear Warfare Water Contamination.

DTIC Science & Technology

1982-05-01

obscured the important relationship between radionuclide ground concentrations and fallout dose rate contours by focusing too much attention on the...19 ) Radiological water contamination by nonpoint sources has received little, if any, attention in the current literature on the environmental... attention . Nevertheless, the environmental contamination of water supplies by fallout has been noted as a source of background radiation (20 ) and a possible

Radionuclides in bats using a contaminated pond on the Nevada National Security Site, USA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warren, Ronald W.; Hall, Derek B.; Greger, Paul D.

In this study, perched groundwater percolating through radionuclide contamination in the E Tunnel Complex on the Nevada National Security Site, formerly the Nevada Test Site, emerges and is stored in a series of ponds making it available to wildlife, including bats. Since many bat species using the ponds are considered sensitive or protected/regulated and little information is available on dose to bats from radioactive water sources, bats were sampled to determine if the dose they were receiving exceeded the United States Department of Energy dose limit of 1.0E-3 Gy/day. Radionuclide concentrations in water, sediment, and flying insects were also measuredmore » as input parameters to the dose rate model and to examine trophic level relationships. The RESRAD-Biota model was used to calculate dose rates to bats using different screening levels. Efficacy of RESRAD-Biota and suggested improvements are discussed. Finally, dose to bats foraging and drinking at these ponds is well below the dose limit set to protect terrestrial biota populations.« less

Radionuclides in bats using a contaminated pond on the Nevada National Security Site, USA

DOE PAGES

Warren, Ronald W.; Hall, Derek B.; Greger, Paul D.

2014-01-03

In this study, perched groundwater percolating through radionuclide contamination in the E Tunnel Complex on the Nevada National Security Site, formerly the Nevada Test Site, emerges and is stored in a series of ponds making it available to wildlife, including bats. Since many bat species using the ponds are considered sensitive or protected/regulated and little information is available on dose to bats from radioactive water sources, bats were sampled to determine if the dose they were receiving exceeded the United States Department of Energy dose limit of 1.0E-3 Gy/day. Radionuclide concentrations in water, sediment, and flying insects were also measuredmore » as input parameters to the dose rate model and to examine trophic level relationships. The RESRAD-Biota model was used to calculate dose rates to bats using different screening levels. Efficacy of RESRAD-Biota and suggested improvements are discussed. Finally, dose to bats foraging and drinking at these ponds is well below the dose limit set to protect terrestrial biota populations.« less

Development of a Monte Carlo multiple source model for inclusion in a dose calculation auditing tool.

PubMed

Faught, Austin M; Davidson, Scott E; Fontenot, Jonas; Kry, Stephen F; Etzel, Carol; Ibbott, Geoffrey S; Followill, David S

2017-09-01

The Imaging and Radiation Oncology Core Houston (IROC-H) (formerly the Radiological Physics Center) has reported varying levels of agreement in their anthropomorphic phantom audits. There is reason to believe one source of error in this observed disagreement is the accuracy of the dose calculation algorithms and heterogeneity corrections used. To audit this component of the radiotherapy treatment process, an independent dose calculation tool is needed. Monte Carlo multiple source models for Elekta 6 MV and 10 MV therapeutic x-ray beams were commissioned based on measurement of central axis depth dose data for a 10 × 10 cm 2 field size and dose profiles for a 40 × 40 cm 2 field size. The models were validated against open field measurements consisting of depth dose data and dose profiles for field sizes ranging from 3 × 3 cm 2 to 30 × 30 cm 2 . The models were then benchmarked against measurements in IROC-H's anthropomorphic head and neck and lung phantoms. Validation results showed 97.9% and 96.8% of depth dose data passed a ±2% Van Dyk criterion for 6 MV and 10 MV models respectively. Dose profile comparisons showed an average agreement using a ±2%/2 mm criterion of 98.0% and 99.0% for 6 MV and 10 MV models respectively. Phantom plan comparisons were evaluated using ±3%/2 mm gamma criterion, and averaged passing rates between Monte Carlo and measurements were 87.4% and 89.9% for 6 MV and 10 MV models respectively. Accurate multiple source models for Elekta 6 MV and 10 MV x-ray beams have been developed for inclusion in an independent dose calculation tool for use in clinical trial audits. © 2017 American Association of Physicists in Medicine.

SU-F-T-54: Determination of the AAPM TG-43 Brachytherapy Dosimetry Parameters for A New Titanium-Encapsulated Yb-169 Source by Monte Carlo Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reynoso, F; Washington University School of Medicine, St. Louis, MO; Munro, J

2016-06-15

Purpose: To determine the AAPM TG-43 brachytherapy dosimetry parameters of a new titanium-encapsulated Yb-169 source designed to maximize the dose enhancement during gold nanoparticle-aided radiation therapy (GNRT). Methods: An existing Monte Carlo (MC) model of the titanium-encapsulated Yb-169 source, which was described in the current investigators’ published MC optimization study, was modified based on the source manufacturer’s detailed specifications, resulting in an accurate model of the titanium-encapsulated Yb-169 source that was actually manufactured. MC calculations were then performed using the MCNP5 code system and the modified source model, in order to obtain a complete set of the AAPM TG-43 parametersmore » for the new Yb-169 source. Results: The MC-calculated dose rate constant for the new titanium-encapsulated Yb-169 source was 1.05 ± 0.03 cGy per hr U, indicating about 10% decrease from the values reported for the conventional stainless steel-encapsulated Yb-169 sources. The source anisotropy and radial dose function for the new source were found similar to those reported for the conventional Yb-169 sources. Conclusion: In this study, the AAPM TG-43 brachytherapy dosimetry parameters of a new titanium-encapsulated Yb-169 source were determined by MC calculations. The current results suggested that the use of titanium, instead of stainless steel, to encapsulate the Yb-169 core would not lead to any major change in the dosimetric characteristics of the Yb-169 source, while it would allow more low energy photons being transmitted through the source filter thereby leading to an increased dose enhancement during GNRT. Supported by DOD/PCRP grant W81XWH-12-1-0198 This investigation was supported by DOD/PCRP grant W81XWH-12-1- 0198.« less

Estimation of absorbed radiation dose rates in wild rodents inhabiting a site severely contaminated by the Fukushima Dai-ichi nuclear power plant accident.

PubMed

Kubota, Yoshihisa; Takahashi, Hiroyuki; Watanabe, Yoshito; Fuma, Shoichi; Kawaguchi, Isao; Aoki, Masanari; Kubota, Masahide; Furuhata, Yoshiaki; Shigemura, Yusaku; Yamada, Fumio; Ishikawa, Takahiro; Obara, Satoshi; Yoshida, Satoshi

2015-04-01

The dose rates of radiation absorbed by wild rodents inhabiting a site severely contaminated by the Fukushima Dai-ichi Nuclear Power Plant accident were estimated. The large Japanese field mouse (Apodemus speciosus), also called the wood mouse, was the major rodent species captured in the sampling area, although other species of rodents, such as small field mice (Apodemus argenteus) and Japanese grass voles (Microtus montebelli), were also collected. The external exposure of rodents calculated from the activity concentrations of radiocesium ((134)Cs and (137)Cs) in litter and soil samples using the ERICA (Environmental Risk from Ionizing Contaminants: Assessment and Management) tool under the assumption that radionuclides existed as the infinite plane isotropic source was almost the same as those measured directly with glass dosimeters embedded in rodent abdomens. Our findings suggest that the ERICA tool is useful for estimating external dose rates to small animals inhabiting forest floors; however, the estimated dose rates showed large standard deviations. This could be an indication of the inhomogeneous distribution of radionuclides in the sampled litter and soil. There was a 50-fold difference between minimum and maximum whole-body activity concentrations measured in rodents at the time of capture. The radionuclides retained in rodents after capture decreased exponentially over time. Regression equations indicated that the biological half-life of radiocesium after capture was 3.31 d. At the time of capture, the lowest activity concentration was measured in the lung and was approximately half of the highest concentration measured in the mixture of muscle and bone. The average internal absorbed dose rate was markedly smaller than the average external dose rate (<10% of the total absorbed dose rate). The average total absorbed dose rate to wild rodents inhabiting the sampling area was estimated to be approximately 52 μGy h(-1) (1.2 mGy d(-1)), even 3 years after the accident. This dose rate exceeds 0.1-1 mGy d(-1) derived consideration reference level for Reference rat proposed by the International Commission on Radiological Protection (ICRP). Copyright © 2015 Elsevier Ltd. All rights reserved.

Modeling intersubject variability of bronchial doses for inhaled radon progeny.

PubMed

Hofmann, Werner; Winkler-Heil, Renate; Hussain, Majid

2010-10-01

The main sources of intersubject variations considered in the present study were: (1) size and structure of nasal and oral passages, affecting extrathoracic deposition and, in further consequence, the fraction of the inhaled activity reaching the bronchial region; (2) size and asymmetric branching of the human bronchial airway system, leading to variations of diameters, lengths, branching angles, etc.; (3) respiratory parameters, such as tidal volume, and breathing frequency; (4) mucociliary clearance rates; and (5) thickness of the bronchial epithelium and depth of target cells, related to airway diameters. For the calculation of deposition fractions, retained surface activities, and bronchial doses, parameter values were randomly selected from their corresponding probability density functions, derived from experimental data, by applying Monte Carlo methods. Bronchial doses, expressed in mGy WLM-1, were computed for specific mining conditions, i.e., for defined size distributions, unattached fractions, and physical activities. Resulting bronchial dose distributions could be approximated by lognormal distributions. Geometric standard deviations illustrating intersubject variations ranged from about 2 in the trachea to about 7 in peripheral bronchiolar airways. The major sources of the intersubject variability of bronchial doses for inhaled radon progeny are the asymmetry and variability of the linear airway dimensions, the filtering efficiency of the nasal passages, and the thickness of the bronchial epithelium, while fluctuations of the respiratory parameters and mucociliary clearance rates seem to compensate each other.

WE-D-BRE-01: A Sr-90 Irradiation Device for the Study of Cutaneous Radiation Injury

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dorand, JE; Bourland, JD; Burnett, LR

2014-06-15

Purpose: To determine dosimetric character for a custom-built Sr-90 beta irradiator designed for the study of Cutaneous Radiation Injury (CRI) in a porcine animal model. In the event of a radiological accident or terrorist event, Sr-90, a fission by-product, will likely be produced. CRI is a main concern due to the low energy and superficial penetration in tissue of beta particles from Sr-90. Seven 100 mCi plaque Sr-90 radiation sources within a custom-built irradiation device create a 40 mm diameter region of radiation-induced skin injury as part of a larger project to study the efficacy of a topical keratin-based productmore » in CRI healing. Methods: A custom-built mobile irradiation device was designed and implemented for in vivo irradiations. Gafchromic™ EBT3 radiochromic film and a PTW Markus chamber type 23343 were utilized for dosimetric characterization of the beta fluence at the surface produced by this device. Films were used to assess 2-dimensional dose distribution and percent depth dose characteristics of the radiation field. Ion chamber measurements provided dose rate data within the field. Results: The radiation field produced by the irradiation device is homogeneous with high uniformity (∼5%) and symmetry (∼3%) with a steep dose fall-off with depth from the surface. Dose rates were determined to be 3.8 Gy/min and 3.3 Gy/min for film and ion chamber measurements, respectively. A dose rate of 3.4 Gy/min was used to calculate irradiation times for in vivo irradiations. Conclusion: The custom-built irradiation device enables the use of seven Sr-90 beta sources in an array to deliver a 40 mm diameter area of homogeneous skin dose with a dose rate that is useful for research purposes and clinically relevant for the induction of CRI. Doses of 36 and 42 Gy successfully produce Grade III CRI and are used in the study of the efficacy of KeraStat™. This project has been funded in whole or in part with Federal funds from the Biomedical Advanced Research and Development Authority, Office of the Assistant Secretary for Preparedness and Response, Office of the Secretary, Department of Health and Human Services, under Contract No. HHSO100201200007C.« less

Development and comparison of computational models for estimation of absorbed organ radiation dose in rainbow trout (Oncorhynchus mykiss) from uptake of iodine-131.

PubMed

Martinez, N E; Johnson, T E; Capello, K; Pinder, J E

2014-12-01

This study develops and compares different, increasingly detailed anatomical phantoms for rainbow trout (Oncorhynchus mykiss) for the purpose of estimating organ absorbed radiation dose and dose rates from (131)I uptake in multiple organs. The models considered are: a simplistic geometry considering a single organ, a more specific geometry employing additional organs with anatomically relevant size and location, and voxel reconstruction of internal anatomy obtained from CT imaging (referred to as CSUTROUT). Dose Conversion Factors (DCFs) for whole body as well as selected organs of O. mykiss were computed using Monte Carlo modeling, and combined with estimated activity concentrations, to approximate dose rates and ultimately determine cumulative radiation dose (μGy) to selected organs after several half-lives of (131)I. The different computational models provided similar results, especially for source organs (less than 30% difference between estimated doses), and whole body DCFs for each model (∼3 × 10(-3) μGy d(-1) per Bq kg(-1)) were comparable to DCFs listed in ICRP 108 for (131)I. The main benefit provided by the computational models developed here is the ability to accurately determine organ dose. A conservative mass-ratio approach may provide reasonable results for sufficiently large organs, but is only applicable to individual source organs. Although CSUTROUT is the more anatomically realistic phantom, it required much more resource dedication to develop and is less flexible than the stylized phantom for similar results. There may be instances where a detailed phantom such as CSUTROUT is appropriate, but generally the stylized phantom appears to be the best choice for an ideal balance between accuracy and resource requirements. Copyright © 2014 Elsevier Ltd. All rights reserved.

Threat Identification Parameters for a Stolen Category 1 Radioactive Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ussery, Larry Eugene; Winkler, Ryan; Myers, Steven Charles

2016-02-18

Radioactive sources are used very widely for research and practical applications across medicine, industry, government, universities, and agriculture. The risks associated with these sources vary widely depending on the specific radionuclide used to make the source, source activity, and its chemical and physical form. Sources are categorized by a variety of classification schemes according to the specific risk they pose to the public. This report specifically addresses sources that are classified in the highest category for health risk (category 1). Exposure to an unshielded or lightly shielded category 1 source is extremely dangerous to life and health and can bemore » fatal in relatively short exposure times measured in seconds to minutes. A Category 1 source packaged according to the guidelines dictated by the NRC and U.S. Department of Transportation will typically be surrounded by a large amount of dense shielding material, but will still exhibit a significant dose rate in close proximity. Detection ranges for Category 1 gamma ray sources can extend beyond 5000 ft, but will depend mostly on the source isotope and activity, and the level of shielding around the source. Category 1 sources are easy to detect, but difficult to localize. Dose rates in proximity to an unshielded Category 1 source are extraordinarily high. At distances of a few hundred feet, the functionality of many commonly used handheld instruments will be extremely limited for both the localization and identification of the source. Radiation emitted from a Category 1 source will scatter off of both solid material (ground and buildings) and the atmosphere, a phenomenon known as skyshine. This scattering affects the ability to easily localize and find the source.« less

The importance of applicator design for intraluminal brachytherapy of rectal cancer.

PubMed

Hansen, Johnny Witterseh; Jakobsen, Anders

2006-09-01

An important aspect of designing an applicator for radiation treatment of rectal cancer is the ability to minimize dose to the mucosa and noninvolved parts of the rectum wall. For this reason we investigated a construction of a flexible multichannel applicator with several channels placed along the periphery of a cylinder and a construction of a rigid cylinder with a central channel and interchangeable shields. Calculations of the dose gradient, dose homogeneity in the tumor, and shielding ability were performed for the two applicators in question. Furthermore, the influence on dose distribution around a flexible multichannel applicator from an unintended off-axis positioning of the source inside a bent channel was investigated by film measurements on a single bent catheter. Calculations showed that a single-channel applicator with interchangeable shields yields a higher degree of shielding and has a better dose homogeneity in the tumor volume than that of a multi-channel applicator. A single-channel applicator with interchangeable shields was manufactured, and the influence of different size of shield angle on dose rate in front of and behind the shields was measured. While dose rate in front of the shield and shielding ability are closely independent of the size of the shield angle when measured 1 cm from the applicator surface, dose rate in more distant volumes will to some extent be influenced by shield angle due to volume scatter conditions.

The importance of applicator design for intraluminal brachytherapy of rectal cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hansen, Johnny Witterseh; Jakobsen, Anders; Department of Oncology, Hospital of Vejle, DK-7100 Vejle

2006-09-15

An important aspect of designing an applicator for radiation treatment of rectal cancer is the ability to minimize dose to the mucosa and noninvolved parts of the rectum wall. For this reason we investigated a construction of a flexible multichannel applicator with several channels placed along the periphery of a cylinder and a construction of a rigid cylinder with a central channel and interchangeable shields. Calculations of the dose gradient, dose homogeneity in the tumor, and shielding ability were performed for the two applicators in question. Furthermore, the influence on dose distribution around a flexible multichannel applicator from an unintendedmore » off-axis positioning of the source inside a bent channel was investigated by film measurements on a single bent catheter. Calculations showed that a single-channel applicator with interchangeable shields yields a higher degree of shielding and has a better dose homogeneity in the tumor volume than that of a multichannel applicator. A single-channel applicator with interchangeable shields was manufactured, and the influence of different size of shield angle on dose rate in front of and behind the shields was measured. While dose rate in front of the shield and shielding ability are closely independent of the size of the shield angle when measured 1 cm from the applicator surface, dose rate in more distant volumes will to some extent be influenced by shield angle due to volume scatter conditions.« less

SU-E-T-548: Modeling of Breast IORT Using the Xoft 50 KV Brachytherapy Source and 316L Steel Rigid Shield

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burnside, W

Purpose: Xoft provides a set of 316L Stainless Steel Rigid Shields to be used with their 50 kV X-ray source for Breast IORT treatments. Modeling the different shield sizes in MCNP provides information to help make clinical decisions for selecting the appropriate shield size. Methods: The Xoft Axxent 50 kV Electronic Brachytherapy System has several applications in radiation therapy, one of which is treating cancer of the breast intraoperatively by placing the miniaturized X-ray tube inside an applicator balloon that is expanded to fill the lumpectomy bed immediately following tumor removal. The ribs, lung, and muscular chest wall are allmore » regions at risk to receive undesired dose during the treatment. A Xoft 316L Stainless Steel Rigid Shield can be placed between the intracostal muscles of the chest wall and the remaining breast tissue near the balloon to attenuate the beam and protect these organs. These shields are provided in 5 different sizes, and the effects on dose to the surrounding tissues vary with shield size. MCNP was used to model this environment and tally dose rate to certain regions of interest. Results: The average rib dose rate calculated using 0cm (i.e., no shield), 3cm, and 5cm diameter shields were 26.89, 15.43, and 8.91 Gy/hr respectively. The maximum dose rates within the rib reached 94.74 Gy/hr, 53.56 Gy/hr, and 31.44 Gy/hr for the 0cm, 3cm, and 5cm cases respectively. The shadowing effect caused by the steel shields was seen in the 3-D meshes and line profiles. Conclusion: This model predicts a higher dose rate to the underlying rib region with the 3cm shield compared to the 5cm shield; it may be useful to select the largest possible diameter when choosing a shield size for a particular IORT patient. The ability to attenuate the beam to reduce rib dose was also confirmed. Research sponsored by Xoft Inc, a subsidiary of iCAD.« less

PACKAGING CERTIFICATION PROGRAM METHODOLOGY FOR DETERMINING DOSE RATES FOR SMALL GRAM QUANTITIES IN SHIPPING PACKAGINGS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nathan, S.; Loftin, B.; Abramczyk, G.

The Small Gram Quantity (SGQ) concept is based on the understanding that small amounts of hazardous materials, in this case radioactive materials (RAM), are significantly less hazardous than large amounts of the same materials. This paper describes a methodology designed to estimate an SGQ for several neutron and gamma emitting isotopes that can be shipped in a package compliant with 10 CFR Part 71 external radiation level limits regulations. These regulations require packaging for the shipment of radioactive materials, under both normal and accident conditions, to perform the essential functions of material containment, subcriticality, and maintain external radiation levels withinmore » the specified limits. By placing the contents in a helium leak-tight containment vessel, and limiting the mass to ensure subcriticality, the first two essential functions are readily met. Some isotopes emit sufficiently strong photon radiation that small amounts of material can yield a large dose rate outside the package. Quantifying the dose rate for a proposed content is a challenging issue for the SGQ approach. It is essential to quantify external radiation levels from several common gamma and neutron sources that can be safely placed in a specific packaging, to ensure compliance with federal regulations. The Packaging Certification Program (PCP) Methodology for Determining Dose Rate for Small Gram Quantities in Shipping Packagings provides bounding shielding calculations that define mass limits compliant with 10 CFR 71.47 for a set of proposed SGQ isotopes. The approach is based on energy superposition with dose response calculated for a set of spectral groups for a baseline physical packaging configuration. The methodology includes using the MCNP radiation transport code to evaluate a family of neutron and photon spectral groups using the 9977 shipping package and its associated shielded containers as the base case. This results in a set of multipliers for 'dose per particle' for each spectral group. For a given isotope, the source spectrum is folded with the response for each group. The summed contribution from all isotopes determines the total dose from the RAM in the container.« less

A novel approach to neutron dosimetry.

PubMed

Balmer, Matthew J I; Gamage, Kelum A A; Taylor, Graeme C

2016-11-01

Having been overlooked for many years, research is now starting to take into account the directional distribution of neutron workplace fields. Existing neutron dosimetry instrumentation does not account for this directional distribution, resulting in conservative estimates of dose in neutron workplace fields (by around a factor of 2, although this is heavily dependent on the type of field). This conservatism could influence epidemiological studies on the health effects of radiation exposure. This paper reports on the development of an instrument which can estimate the effective dose of a neutron field, accounting for both the direction and the energy distribution. A 6 Li-loaded scintillator was used to perform neutron assays at a number of locations in a 20 × 20 × 17.5 cm 3 water phantom. The variation in thermal and fast neutron response to different energies and field directions was exploited. The modeled response of the instrument to various neutron fields was used to train an artificial neural network (ANN) to learn the effective dose and ambient dose equivalent of these fields. All experimental data published in this work were measured at the National Physical Laboratory (UK). Experimental results were obtained for a number of radionuclide source based neutron fields to test the performance of the system. The results of experimental neutron assays at 25 locations in a water phantom were fed into the trained ANN. A correlation between neutron counting rates in the phantom and neutron fluence rates was experimentally found to provide dose rate estimates. A radionuclide source behind shadow cone was used to create a more complex field in terms of energy and direction. For all fields, the resulting estimates of effective dose rate were within 45% or better of their calculated values, regardless of energy distribution or direction for measurement times greater than 25 min. This work presents a novel, real-time, approach to workplace neutron dosimetry. It is believed that in the research presented in this paper, for the first time, a single instrument has been able to estimate effective dose.

A quality assurance program for clinical PDT

NASA Astrophysics Data System (ADS)

Dimofte, Andreea; Finlay, Jarod; Ong, Yi Hong; Zhu, Timothy C.

2018-02-01

Successful outcome of Photodynamic therapy (PDT) depends on accurate delivery of prescribed light dose. A quality assurance program is necessary to ensure that light dosimetry is correctly measured. We have instituted a QA program that include examination of long term calibration uncertainty of isotropic detectors for light fluence rate, power meter head intercomparison for laser power, stability of the light-emitting diode (LED) light source integrating sphere as a light fluence standard, laser output and calibration of in-vivo reflective fluorescence and absorption spectrometers. We examined the long term calibration uncertainty of isotropic detector sensitivity, defined as fluence rate per voltage. We calibrate the detector using the known calibrated light fluence rate of the LED light source built into an internally baffled 4" integrating sphere. LED light sources were examined using a 1mm diameter isotropic detector calibrated in a collimated beam. Wavelengths varying from 632nm to 690nm were used. The internal LED method gives an overall calibration accuracy of +/- 4%. Intercomparison among power meters was performed to determine the consistency of laser power and light fluence rate measured among different power meters. Power and fluence readings were measured and compared among detectors. A comparison of power and fluence reading among several power heads shows long term consistency for power and light fluence rate calibration to within 3% regardless of wavelength. The standard LED light source is used to calibrate the transmission difference between different channels for the diffuse reflective absorption and fluorescence contact probe as well as isotropic detectors used in PDT dose dosimeter.

Biphasic and monophasic repair: comparative implications for biologically equivalent dose calculations in pulsed dose rate brachytherapy of cervical carcinoma

PubMed Central

Millar, W T; Davidson, S E

2013-01-01

Objective: To consider the implications of the use of biphasic rather than monophasic repair in calculations of biologically-equivalent doses for pulsed-dose-rate brachytherapy of cervix carcinoma. Methods: Calculations are presented of pulsed-dose-rate (PDR) doses equivalent to former low-dose-rate (LDR) doses, using biphasic vs monophasic repair kinetics, both for cervical carcinoma and for the organ at risk (OAR), namely the rectum. The linear-quadratic modelling calculations included effects due to varying the dose per PDR cycle, the dose reduction factor for the OAR compared with Point A, the repair kinetics and the source strength. Results: When using the recommended 1 Gy per hourly PDR cycle, different LDR-equivalent PDR rectal doses were calculated depending on the choice of monophasic or biphasic repair kinetics pertaining to the rodent central nervous and skin systems. These differences virtually disappeared when the dose per hourly cycle was increased to 1.7 Gy. This made the LDR-equivalent PDR doses more robust and independent of the choice of repair kinetics and α/β ratios as a consequence of the described concept of extended equivalence. Conclusion: The use of biphasic and monophasic repair kinetics for optimised modelling of the effects on the OAR in PDR brachytherapy suggests that an optimised PDR protocol with the dose per hourly cycle nearest to 1.7 Gy could be used. Hence, the durations of the new PDR treatments would be similar to those of the former LDR treatments and not longer as currently prescribed. Advances in knowledge: Modelling calculations indicate that equivalent PDR protocols can be developed which are less dependent on the different α/β ratios and monophasic/biphasic kinetics usually attributed to normal and tumour tissues for treatment of cervical carcinoma. PMID:23934965

Prospectively ECG-triggered high-pitch coronary angiography with third-generation dual-source CT at 70 kVp tube voltage: feasibility, image quality, radiation dose, and effect of iterative reconstruction.

PubMed

Hell, Michaela M; Bittner, Daniel; Schuhbaeck, Annika; Muschiol, Gerd; Brand, Michael; Lell, Michael; Uder, Michael; Achenbach, Stephan; Marwan, Mohamed

2014-01-01

Low tube voltage reduces radiation exposure in coronary CT angiography (CTA). Using 70 kVp tube potential has so far not been possible because CT systems were unable to provide sufficiently high tube current with low voltage. We evaluated feasibility, image quality (IQ), and radiation dose of coronary CTA using a third-generation dual-source CT system capable of producing 450 mAs tube current at 70 kVp tube voltage. Coronary CTA was performed in 26 consecutive patients with suspected coronary artery disease, selected for body weight <100 kg and heart rate <60 beats/min. High-pitch spiral acquisition was used. Filtered back projection (FBP) and iterative reconstruction (IR) algorithms were applied. IQ was assessed using a 4-point rating scale (1 = excellent, 4 = nondiagnostic) and objective parameters. Mean age was 62 ± 9 years (46% males; mean body mass index, 27.7 ± 3.8 kg/m(2); mean heart rate, 54 ± 5 beats/min). Mean dose-length product was 20.6 ± 1.9 mGy × cm; mean estimated effective radiation dose was 0.3 ± 0.03 mSv. Diagnostic IQ was found in 365 of 367 (FBP) and 366 of 367 (IR) segments (P nonsignificant). IQ was rated "excellent" in 53% (FBP) and 86% (IR) segments (P = .001) and "nondiagnostic" in 2 (FBP) and 1 segment (IR) (P nonsignificant). Mean IQ score was lesser in FBP vs IR (1.5 ± 0.4 vs 1.1 ± 0.2; P < .001). Image noise was lower in IR vs FBP (60 ± 10 HU vs 74 ± 8 HU; P < .001). In patients <100 kg and with a regular heart rate <60 beats/min, third-generation dual-source CT using high-pitch spiral acquisition and 70 kVp tube voltage is feasible and provides both robust IQ and very low radiation exposure. Copyright © 2014 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.

MAGAT gel and EBT2 film‐based dosimetry for evaluating source plugging‐based treatment plan in Gamma Knife stereotactic radiosurgery

PubMed Central

Vivekanandhan, S.; Kale, S.S.; Rath, G.K.; Senthilkumaran, S.; Thulkar, S.; Subramani, V.; Laviraj, M.A.; Bisht, R.K.; Mahapatra, A.K.

2012-01-01

This work illustrates a procedure to assess the overall accuracy associated with Gamma Knife treatment planning using plugging. The main role of source plugging or blocking is to create dose falloff in the junction between a target and a critical structure. We report the use of MAGAT gel dosimeter for verification of an experimental treatment plan based on plugging. The polymer gel contained in a head‐sized glass container simulated all major aspects of the treatment process of Gamma Knife radiosurgery. The 3D dose distribution recorded in the gel dosimeter was read using a 1.5T MRI scanner. Scanning protocol was: CPMG pulse sequence with 8 equidistant echoes, TR=7 s, echo step=14 ms, pixel size=0.5 mm x 0.5 mm, and slice thickness of 2 mm. Using a calibration relationship between absorbed dose and spin‐spin relaxation rate (R2), we converted R2 images to dose images. Volumetric dose comparison between treatment planning system (TPS) and gel measurement was accomplished using an in‐house MATLAB‐based program. The isodose overlay of the measured and computed dose distribution on axial planes was in close agreement. Gamma index analysis of 3D data showed more than 94% voxel pass rate for different tolerance criteria of 3%/2 mm, 3%/1 mm and 2%/2 mm. Film dosimetry with GAFCHROMIC EBT 2 film was also performed to compare the results with the calculated TPS dose. Gamma index analysis of film measurement for the same tolerance criteria used for gel measurement evaluation showed more than 95% voxel pass rate. Verification of gamma plan calculated dose on account of shield is not part of acceptance testing of Leksell Gamma Knife (LGK). Through this study we accomplished a volumetric comparison of dose distributions measured with a polymer gel dosimeter and Leksell GammaPlan (LGP) calculations for plans using plugging. We propose gel dosimeter as a quality assurance (QA) tool for verification of plug‐based planning. PACS number: 87.53.Ly, 87.55.‐x, 87.56.N‐ PMID:23149780

Inverse modelling of radionuclide release rates using gamma dose rate observations

NASA Astrophysics Data System (ADS)

Hamburger, Thomas; Evangeliou, Nikolaos; Stohl, Andreas; von Haustein, Christoph; Thummerer, Severin; Wallner, Christian

2015-04-01

Severe accidents in nuclear power plants such as the historical accident in Chernobyl 1986 or the more recent disaster in the Fukushima Dai-ichi nuclear power plant in 2011 have drastic impacts on the population and environment. Observations and dispersion modelling of the released radionuclides help to assess the regional impact of such nuclear accidents. Modelling the increase of regional radionuclide activity concentrations, which results from nuclear accidents, underlies a multiplicity of uncertainties. One of the most significant uncertainties is the estimation of the source term. That is, the time dependent quantification of the released spectrum of radionuclides during the course of the nuclear accident. The quantification of the source term may either remain uncertain (e.g. Chernobyl, Devell et al., 1995) or rely on estimates given by the operators of the nuclear power plant. Precise measurements are mostly missing due to practical limitations during the accident. The release rates of radionuclides at the accident site can be estimated using inverse modelling (Davoine and Bocquet, 2007). The accuracy of the method depends amongst others on the availability, reliability and the resolution in time and space of the used observations. Radionuclide activity concentrations are observed on a relatively sparse grid and the temporal resolution of available data may be low within the order of hours or a day. Gamma dose rates, on the other hand, are observed routinely on a much denser grid and higher temporal resolution and provide therefore a wider basis for inverse modelling (Saunier et al., 2013). We present a new inversion approach, which combines an atmospheric dispersion model and observations of radionuclide activity concentrations and gamma dose rates to obtain the source term of radionuclides. We use the Lagrangian particle dispersion model FLEXPART (Stohl et al., 1998; Stohl et al., 2005) to model the atmospheric transport of the released radionuclides. The inversion method uses a Bayesian formulation considering uncertainties for the a priori source term and the observations (Eckhardt et al., 2008, Stohl et al., 2012). The a priori information on the source term is a first guess. The gamma dose rate observations are used to improve the first guess and to retrieve a reliable source term. The details of this method will be presented at the conference. This work is funded by the Bundesamt für Strahlenschutz BfS, Forschungsvorhaben 3612S60026. References Davoine, X. and Bocquet, M., Atmos. Chem. Phys., 7, 1549-1564, 2007. Devell, L., et al., OCDE/GD(96)12, 1995. Eckhardt, S., et al., Atmos. Chem. Phys., 8, 3881-3897, 2008. Saunier, O., et al., Atmos. Chem. Phys., 13, 11403-11421, 2013. Stohl, A., et al., Atmos. Environ., 32, 4245-4264, 1998. Stohl, A., et al., Atmos. Chem. Phys., 5, 2461-2474, 2005. Stohl, A., et al., Atmos. Chem. Phys., 12, 2313-2343, 2012.

SU-F-T-50: Evaluation of Monte Carlo Simulations Performance for Pediatric Brachytherapy Dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatzipapas, C; Kagadis, G; Papadimitroulas, P

Purpose: Pediatric tumors are generally treated with multi-modal procedures. Brachytherapy can be used with pediatric tumors, especially given that in this patient population low toxicity on normal tissues is critical as is the suppression of the probability for late malignancies. Our goal is to validate the GATE toolkit on realistic brachytherapy applications, and evaluate brachytherapy plans on pediatrics for accurate dosimetry on sensitive and critical organs of interest. Methods: The GATE Monte Carlo (MC) toolkit was used. Two High Dose Rate (HDR) 192Ir brachytherapy sources were simulated (Nucletron mHDR-v1 and Varian VS2000), and fully validated using the AAPM and ESTROmore » protocols. A realistic brachytherapy plan was also simulated using the XCAT anthropomorphic computational model .The simulated data were compared to the clinical dose points. Finally, a 14 years old girl with vaginal rhabdomyosarcoma was modelled based on clinical procedures for the calculation of the absorbed dose per organ. Results: The MC simulations resulted in accurate dosimetry in terms of dose rate constant (Λ), radial dose gL(r) and anisotropy function F(r,θ) for both sources.The simulations were executed using ∼1010 number of primaries resulting in statistical uncertainties lower than 2%.The differences between the theoretical values and the simulated ones ranged from 0.01% up to 3.3%, with the largest discrepancy (6%) being observed in the dose rate constant calculation.The simulated DVH using an adult female XCAT model was also compared to a clinical one resulting in differences smaller than 5%. Finally, a realistic pediatric brachytherapy simulation was performed to evaluate the absorbed dose per organ and to calculate DVH with respect to heterogeneities of the human anatomy. Conclusion: GATE is a reliable tool for brachytherapy simulations both for source modeling and for dosimetry in anthropomorphic voxelized models. Our project aims to evaluate a variety of pediatric brachytherapy schemes using a population of pediatric phantoms for several pathological cases. This study is part of a project that has received funding from the European Union Horizon2020 research and innovation programme under the MarieSklodowska-Curiegrantagreement.No691203.The results published in this study reflect only the authors view and the Research Executive Agency (REA) and the European Commission is not responsible for any use that may be madeof the information it contains.« less

Severe accident skyshine radiation analysis by MCNP

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eurajoki, T.

1994-12-31

If a severe accident with a considerable core damage occurs at a nuclear power plant whose containment top is remarkably thin compared with the walls, the radiation transported through the top and scattered in air may cause high dose rates at the power plant area. Noble gases and other fission products released to the containment act as sources. The dose rates caused by skyshine have been calculated by MCNP3A for the Loviisa nuclear power plant (two-unit, 445-MW VVER) for the outside area and inside some buildings, taking the attenuation in the roofs of the buildings into account.

Combined experimental and Monte Carlo verification of brachytherapy plans for vaginal applicators

NASA Astrophysics Data System (ADS)

Sloboda, Ron S.; Wang, Ruqing

1998-12-01

Dose rates in a phantom around a shielded and an unshielded vaginal applicator containing Selectron low-dose-rate sources were determined by experiment and Monte Carlo simulation. Measurements were performed with thermoluminescent dosimeters in a white polystyrene phantom using an experimental protocol geared for precision. Calculations for the same set-up were done using a version of the EGS4 Monte Carlo code system modified for brachytherapy applications into which a new combinatorial geometry package developed by Bielajew was recently incorporated. Measured dose rates agree with Monte Carlo estimates to within 5% (1 SD) for the unshielded applicator, while highlighting some experimental uncertainties for the shielded applicator. Monte Carlo calculations were also done to determine a value for the effective transmission of the shield required for clinical treatment planning, and to estimate the dose rate in water at points in axial and sagittal planes transecting the shielded applicator. Comparison with dose rates generated by the planning system indicates that agreement is better than 5% (1 SD) at most positions. The precision thermoluminescent dosimetry protocol and modified Monte Carlo code are effective complementary tools for brachytherapy applicator dosimetry.

Monte Carlo skin dose simulation in intraoperative radiotherapy of breast cancer using spherical applicators

NASA Astrophysics Data System (ADS)

Moradi, F.; Ung, N. M.; Khandaker, M. U.; Mahdiraji, G. A.; Saad, M.; Malik, R. Abdul; Bustam, A. Z.; Zaili, Z.; Bradley, D. A.

2017-08-01

The relatively new treatment modality electronic intraoperative radiotherapy (IORT) is gaining popularity, irradiation being obtained within a surgically produced cavity being delivered via a low-energy x-ray source and spherical applicators, primarily for early stage breast cancer. Due to the spatially dramatic dose-rate fall off with radial distance from the source and effects related to changes in the beam quality of the low keV photon spectra, dosimetric account of the Intrabeam system is rather complex. Skin dose monitoring in IORT is important due to the high dose prescription per treatment fraction. In this study, modeling of the x-ray source and related applicators were performed using the Monte Carlo N-Particle transport code. The dosimetric characteristics of the model were validated against measured data obtained using an ionization chamber and EBT3 film as dosimeters. By using a simulated breast phantom, absorbed doses to the skin for different combinations of applicator size (1.5-5 cm) and treatment depth (0.5-3 cm) were calculated. Simulation results showed overdosing of the skin (>30% of prescribed dose) at a treatment depth of 0.5 cm using applicator sizes larger than 1.5 cm. Skin doses were significantly increased with applicator size, insofar as delivering 12 Gy (60% of the prescribed dose) to skin for the largest sized applicator (5 cm diameter) and treatment depth of 0.5 cm. It is concluded that the recommended 0.5-1 cm distance between the skin and applicator surface does not guarantee skin safety and skin dose is generally more significant in cases with the larger applicators. Highlights: • Intrabeam x-ray source and spherical applicators were simulated and skin dose was calculated. • Skin dose for constant skin to applicator distance strongly depends on applicator size. • Use of larger applicators generally results in higher skin dose. • The recommended 0.5-1 cm skin to applicator distance does not guarantee skin safety.

SU-E-T-278: Realization of Dose Verification Tool for IMRT Plan Based On DPM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cai, Jinfeng; Cao, Ruifen; Dai, Yumei

Purpose: To build a Monte Carlo dose verification tool for IMRT Plan by implementing a irradiation source model into DPM code. Extend the ability of DPM to calculate any incident angles and irregular-inhomogeneous fields. Methods: With the virtual source and the energy spectrum which unfolded from the accelerator measurement data,combined with optimized intensity maps to calculate the dose distribution of the irradiation irregular-inhomogeneous field. The irradiation source model of accelerator was substituted by a grid-based surface source. The contour and the intensity distribution of the surface source were optimized by ARTS (Accurate/Advanced Radiotherapy System) optimization module based on the tumormore » configuration. The weight of the emitter was decided by the grid intensity. The direction of the emitter was decided by the combination of the virtual source and the emitter emitting position. The photon energy spectrum unfolded from the accelerator measurement data was adjusted by compensating the contaminated electron source. For verification, measured data and realistic clinical IMRT plan were compared with DPM dose calculation. Results: The regular field was verified by comparing with the measured data. It was illustrated that the differences were acceptable (<2% inside the field, 2–3mm in the penumbra). The dose calculation of irregular field by DPM simulation was also compared with that of FSPB (Finite Size Pencil Beam) and the passing rate of gamma analysis was 95.1% for peripheral lung cancer. The regular field and the irregular rotational field were all within the range of permitting error. The computing time of regular fields were less than 2h, and the test of peripheral lung cancer was 160min. Through parallel processing, the adapted DPM could complete the calculation of IMRT plan within half an hour. Conclusion: The adapted parallelized DPM code with irradiation source model is faster than classic Monte Carlo codes. Its computational accuracy and speed satisfy the clinical requirement, and it is expectable to be a Monte Carlo dose verification tool for IMRT Plan. Strategic Priority Research Program of the China Academy of Science(XDA03040000); National Natural Science Foundation of China (81101132)« less

WE-DE-201-07: Measurement of Real-Time Dose for Tandem and Ovoid Brachytherapy Procedures Using a High Precision Optical Fiber Radiation Detector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belley, MD; Current Address Rhode Island Hospital, Providence, RI; Faught, A

Purpose: Development of a novel on-line dosimetry tool is needed to move toward patient-specific quality assurance measurements for Ir-192 HDR brachytherapy to verify accurate dose delivery to the intended location. This work describes the development and use of a nano-crystalline yttrium oxide inorganic scintillator based optical-fiber detector capable of acquiring real-time high-precision dose measurements during tandem and ovoid (T&O) gynecological (GYN) applicator Ir-192 HDR brachytherapy procedures. Methods: An optical-fiber detector was calibrated by acquiring light output measurements in liquid water at 3, 5, 7, and 9cm radial source-detector-distances from an Ir-192 HDR source. A regression model was fit to themore » data to describe the relative light output per unit dose (TG-43 derived) as a function of source-detector-distance. Next, the optical-fiber detector was attached to a vaginal balloon fixed to a Varian Fletcher-Suit-Delclos-style applicator (to mimic clinical setup), and localized by acquiring high-resolution computed tomography (CT) images. To compare the physical point dose to the TPS calculated values (TG-43 and Acuros-BV), a phantom measurement was performed, by submerging the T&O applicator in a liquid water bath and delivering a treatment template representative of a clinical T&O procedure. The fiber detector collected scintillation signal as a function of time, and the calibration data was applied to calculate both real-time dose rate, and cumulative dose. Results: Fiber cumulative dose values were 100.0cGy, 94.3cGy, and 348.9cGy from the tandem, left ovoid, and right ovoid dwells, respectively (total of 443.2cGy). A plot of real time dose rate during the treatment was also acquired. The TPS values at the fiber location were 458.4cGy using TG-43, and 437.6cGy using Acuros-BV calculated as Dm,m (per TG-186). Conclusion: The fiber measured dose value agreement was 3% vs TG-43 and −1% vs Acuros-BV. This fiber detector opens up new possibilities for performing patient-specific quality assurance for Ir-192 HDR GYN procedures. Funding from Coulter Foundation, Duke Bio-medical Engineering. Company is being created around the detector technology. Duke holds patents on the technology.« less

Characterization of the radiation environment for a large-area interim spent-nuclear-fuel storage facility

NASA Astrophysics Data System (ADS)

Fortkamp, Jonathan C.

Current needs in the nuclear industry and movements in the political arena indicate that authorization may soon be given for development of a federal interim storage facility for spent nuclear fuel. The initial stages of the design work have already begun within the Department of Energy and are being reviewed by the Nuclear Regulatory Commission. This dissertation addresses the radiation environment around an interim spent nuclear fuel storage facility. Specifically the dissertation characterizes the radiation dose rates around the facility based on a design basis source term, evaluates the changes in dose due to varying cask spacing configurations, and uses these results to define some applicable health physics principles for the storage facility. Results indicate that dose rates from the facility are due primarily from photons from the spent fuel and Co-60 activation in the fuel assemblies. In the modeled cask system, skyshine was a significant contribution to dose rates at distances from the cask array, but this contribution can be reduced with an alternate cask venting system. With the application of appropriate health physics principles, occupation doses can be easily maintained far below regulatory limits and maintained ALARA.

A dose assessment method for arbitrary geometries with virtual reality in the nuclear facilities decommissioning

NASA Astrophysics Data System (ADS)

Chao, Nan; Liu, Yong-kuo; Xia, Hong; Ayodeji, Abiodun; Bai, Lu

2018-03-01

During the decommissioning of nuclear facilities, a large number of cutting and demolition activities are performed, which results in a frequent change in the structure and produce many irregular objects. In order to assess dose rates during the cutting and demolition process, a flexible dose assessment method for arbitrary geometries and radiation sources was proposed based on virtual reality technology and Point-Kernel method. The initial geometry is designed with the three-dimensional computer-aided design tools. An approximate model is built automatically in the process of geometric modeling via three procedures namely: space division, rough modeling of the body and fine modeling of the surface, all in combination with collision detection of virtual reality technology. Then point kernels are generated by sampling within the approximate model, and when the material and radiometric attributes are inputted, dose rates can be calculated with the Point-Kernel method. To account for radiation scattering effects, buildup factors are calculated with the Geometric-Progression formula in the fitting function. The effectiveness and accuracy of the proposed method was verified by means of simulations using different geometries and the dose rate results were compared with that derived from CIDEC code, MCNP code and experimental measurements.

Adaptive prospective ECG-triggered sequence coronary angiography in dual-source CT without heart rate control: Image quality and diagnostic performance.

PubMed

Pan, Chang-Jie; Qian, Nong; Wang, Tao; Tang, Xiao-Qiang; Xue, Yue-Jun

2013-02-01

The aim of this study was to evaluate the accuracy of using second generation dual-source CT (DSCT) to obtain high quality images and diagnostic performance and to reduce the radiation dose in adaptive prospective electrocardiography (ECG)-triggered sequence (CorAdSeq) CT coronary angiography (CTCA) without heart rate control. No prescan β-blockers were administered. Un-enhanced CT and CTCA with adaptive prospective CorAdSeq scanning without heart rate control were performed in 683 consecutive patients divided into two body mass index (BMI) groups: BMI <25 kg/m(2) (group A, n=412) and BMI ≥25 kg/m(2) (group B, n=271). The image quality and quantitative stenosis of all coronary segments with a diameter ≥1 mm were assessed. The mean heart rate (MHR), heart rate variability (HRV) and radiation dose values were recorded. In 426 cases, the diagnostic performance was evaluated using quantitative conventional coronary angiography as the reference standard. Diagnostic image quality was obtained in 98.5% of segments in group A and in 98.8% of segments in group B, with no significant differences between the groups. No correlations were observed between the image quality score and MHR or HRV (P=0.492, P=0.564, respectively). The effective radiation doses in groups A and B were 2.57±1.01 mSv and 6.36±1.88 mSv, respectively. The sensitivities and specificities of diagnosing coronary heart disease per patient were 99.6% and 97.8% in group A and 99.5% and 97.5% in group B, respectively (P>0.05). Adaptive prospective CorAdSeq scanning, without heart rate control, by second generation DSCT had a high image quality and diagnostic performance for coronary artery stenosis with lower radiation doses.

In vivo urethral dose measurements: a method to verify high dose rate prostate treatments.

PubMed

Brezovich, I A; Duan, J; Pareek, P N; Fiveash, J; Ezekiel, M

2000-10-01

Radiation doses delivered in high dose rate (HDR) brachytherapy are susceptible to many inaccuracies and errors, including imaging, planning and delivery. Consequently, the dose delivered to the patient may deviate substantially from the treatment plan. We investigated the feasibility of using TLD measurements in the urethra to estimate the discrepancy in treatments for prostate cancer. The dose response of the 1 mm diam, 6 mm long LiF rods that we used for the in vivo measurements was calibrated with the 192Ir HDR source, as well as a 60Co teletherapy unit. A train of 20 rods contained in a sterile plastic tube was inserted into the urethral (Foley) catheter for the duration of a treatment fraction, and the measured doses were compared to the treatment plan. Initial results from a total of seven treatments in four patients show good agreement between theory and experiment. Analysis of any one treatment showed agreement within 11.7% +/- 6.2% for the highest dose encountered in the central prostatic urethra, and within 10.4% +/- 4.4% for the mean dose. Taking the average over all seven treatments shows agreement within 1.7% for the maximum urethral dose, and within 1.5% for the mean urethral dose. Based on these initial findings it seems that planned prostate doses can be accurately reproduced in the clinic.

High dose-per-pulse electron beam dosimetry - A model to correct for the ion recombination in the Advanced Markus ionization chamber.

PubMed

Petersson, Kristoffer; Jaccard, Maud; Germond, Jean-François; Buchillier, Thierry; Bochud, François; Bourhis, Jean; Vozenin, Marie-Catherine; Bailat, Claude

2017-03-01

The purpose of this work was to establish an empirical model of the ion recombination in the Advanced Markus ionization chamber for measurements in high dose rate/dose-per-pulse electron beams. In addition, we compared the observed ion recombination to calculations using the standard Boag two-voltage-analysis method, the more general theoretical Boag models, and the semiempirical general equation presented by Burns and McEwen. Two independent methods were used to investigate the ion recombination: (a) Varying the grid tension of the linear accelerator (linac) gun (controls the linac output) and measuring the relative effect the grid tension has on the chamber response at different source-to-surface distances (SSD). (b) Performing simultaneous dose measurements and comparing the dose-response, in beams with varying dose rate/dose-per-pulse, with the chamber together with dose rate/dose-per-pulse independent Gafchromic™ EBT3 film. Three individual Advanced Markus chambers were used for the measurements with both methods. All measurements were performed in electron beams with varying mean dose rate, dose rate within pulse, and dose-per-pulse (10 -2  ≤ mean dose rate ≤ 10 3 Gy/s, 10 2  ≤ mean dose rate within pulse ≤ 10 7  Gy/s, 10 -4  ≤ dose-per-pulse ≤ 10 1  Gy), which was achieved by independently varying the linac gun grid tension, and the SSD. The results demonstrate how the ion collection efficiency of the chamber decreased as the dose-per-pulse increased, and that the ion recombination was dependent on the dose-per-pulse rather than the dose rate, a behavior predicted by Boag theory. The general theoretical Boag models agreed well with the data over the entire investigated dose-per-pulse range, but only for a low polarizing chamber voltage (50 V). However, the two-voltage-analysis method and the Burns & McEwen equation only agreed with the data at low dose-per-pulse values (≤ 10 -2 and ≤ 10 -1  Gy, respectively). An empirical model of the ion recombination in the chamber was found by fitting a logistic function to the data. The ion collection efficiency of the Advanced Markus ionization chamber decreases for measurements in electron beams with increasingly higher dose-per-pulse. However, this chamber is still functional for dose measurements in beams with dose-per-pulse values up toward and above 10 Gy, if the ion recombination is taken into account. Our results show that existing models give a less-than-accurate description of the observed ion recombination. This motivates the use of the presented empirical model for measurements with the Advanced Markus chamber in high dose-per-pulse electron beams, as it enables accurate absorbed dose measurements (uncertainty estimation: 2.8-4.0%, k = 1). The model depends on the dose-per-pulse in the beam, and it is also influenced by the polarizing chamber voltage, with increasing ion recombination with a lowering of the voltage. © 2017 American Association of Physicists in Medicine.

Comparison of 10 efficient protocols for photodynamic therapy of actinic keratosis: How relevant are effective light dose and local damage in predicting the complete response rate at 3 months?

PubMed

Vignion-Dewalle, Anne-Sophie; Baert, Gregory; Thecua, Elise; Lecomte, Fabienne; Vicentini, Claire; Abi-Rached, Henry; Mortier, Laurent; Mordon, Serge

2018-04-18

Topical photodynamic therapy is an established treatment modality for various dermatological conditions, including actinic keratosis. In Europe, the approved protocols for photodynamic therapy of actinic keratosis involve irradiation with either an Aktilite CL 128 lamp or daylight, whereas irradiation with the Blu-U illuminator is approved in the United States. Many other protocols using irradiation by a variety of light sources are also clinically efficient. This paper aims to compare 10 different protocols with clinically proven efficacy for photodynamic therapy of actinic keratosis and the available spectral irradiance of the light source. Effective irradiance, effective light dose, and local damage are compared. We also investigate whether there is an association between the complete response rate at 3 months and the effective light dose or local damage. The effective irradiance, also referred to as protoporphyrin IX-weighted irradiance, is obtained by integrating the spectral irradiance weighted by the normalized absorption spectrum of protoporphyrin IX over the wavelength. Integrating the effective irradiance over the irradiation time yields the effective light dose, which is also known as the protoporphyrin IX-weighted light dose. Local damage, defined as the total cumulative singlet oxygen molecules produced during treatment, is estimated using mathematical modeling of the photodynamic therapy process. This modeling is based on an iterative procedure taking into account the spatial and temporal variations in the protoporphyrin IX absorption spectrum during treatment. The protocol for daylight photodynamic therapy on a clear sunny day, the protocol for daylight photodynamic therapy on an overcast day, the photodynamic therapy protocol for a white LED lamp for operating rooms and the photodynamic therapy protocol for the Blu-U illuminator perform better than the six other protocols-all involving red light illumination-in terms of both effective light dose and local damage. However, no association between the complete response rate at 3 months and the effective light dose or local damage was found. Protocols that achieve high complete response rates at 3 months and low pain scores should be preferred regardless of the effective light dose and local damage. Lasers Surg. Med. © 2018 Wiley Periodicals, Inc. © 2018 Wiley Periodicals, Inc.

FW-CADIS Method for Global and Semi-Global Variance Reduction of Monte Carlo Radiation Transport Calculations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wagner, John C; Peplow, Douglas E.; Mosher, Scott W

2014-01-01

This paper presents a new hybrid (Monte Carlo/deterministic) method for increasing the efficiency of Monte Carlo calculations of distributions, such as flux or dose rate distributions (e.g., mesh tallies), as well as responses at multiple localized detectors and spectra. This method, referred to as Forward-Weighted CADIS (FW-CADIS), is an extension of the Consistent Adjoint Driven Importance Sampling (CADIS) method, which has been used for more than a decade to very effectively improve the efficiency of Monte Carlo calculations of localized quantities, e.g., flux, dose, or reaction rate at a specific location. The basis of this method is the development ofmore » an importance function that represents the importance of particles to the objective of uniform Monte Carlo particle density in the desired tally regions. Implementation of this method utilizes the results from a forward deterministic calculation to develop a forward-weighted source for a deterministic adjoint calculation. The resulting adjoint function is then used to generate consistent space- and energy-dependent source biasing parameters and weight windows that are used in a forward Monte Carlo calculation to obtain more uniform statistical uncertainties in the desired tally regions. The FW-CADIS method has been implemented and demonstrated within the MAVRIC sequence of SCALE and the ADVANTG/MCNP framework. Application of the method to representative, real-world problems, including calculation of dose rate and energy dependent flux throughout the problem space, dose rates in specific areas, and energy spectra at multiple detectors, is presented and discussed. Results of the FW-CADIS method and other recently developed global variance reduction approaches are also compared, and the FW-CADIS method outperformed the other methods in all cases considered.« less

Transmutation approximations for the application of hybrid Monte Carlo/deterministic neutron transport to shutdown dose rate analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biondo, Elliott D.; Wilson, Paul P. H.

In fusion energy systems (FES) neutrons born from burning plasma activate system components. The photon dose rate after shutdown from resulting radionuclides must be quantified. This shutdown dose rate (SDR) is calculated by coupling neutron transport, activation analysis, and photon transport. The size, complexity, and attenuating configuration of FES motivate the use of hybrid Monte Carlo (MC)/deterministic neutron transport. The Multi-Step Consistent Adjoint Driven Importance Sampling (MS-CADIS) method can be used to optimize MC neutron transport for coupled multiphysics problems, including SDR analysis, using deterministic estimates of adjoint flux distributions. When used for SDR analysis, MS-CADIS requires the formulation ofmore » an adjoint neutron source that approximates the transmutation process. In this work, transmutation approximations are used to derive a solution for this adjoint neutron source. It is shown that these approximations are reasonably met for typical FES neutron spectra and materials over a range of irradiation scenarios. When these approximations are met, the Groupwise Transmutation (GT)-CADIS method, proposed here, can be used effectively. GT-CADIS is an implementation of the MS-CADIS method for SDR analysis that uses a series of single-energy-group irradiations to calculate the adjoint neutron source. For a simple SDR problem, GT-CADIS provides speedups of 200 100 relative to global variance reduction with the Forward-Weighted (FW)-CADIS method and 9 ± 5 • 104 relative to analog. As a result, this work shows that GT-CADIS is broadly applicable to FES problems and will significantly reduce the computational resources necessary for SDR analysis.« less

Transmutation approximations for the application of hybrid Monte Carlo/deterministic neutron transport to shutdown dose rate analysis

DOE PAGES

Biondo, Elliott D.; Wilson, Paul P. H.

2017-05-08

In fusion energy systems (FES) neutrons born from burning plasma activate system components. The photon dose rate after shutdown from resulting radionuclides must be quantified. This shutdown dose rate (SDR) is calculated by coupling neutron transport, activation analysis, and photon transport. The size, complexity, and attenuating configuration of FES motivate the use of hybrid Monte Carlo (MC)/deterministic neutron transport. The Multi-Step Consistent Adjoint Driven Importance Sampling (MS-CADIS) method can be used to optimize MC neutron transport for coupled multiphysics problems, including SDR analysis, using deterministic estimates of adjoint flux distributions. When used for SDR analysis, MS-CADIS requires the formulation ofmore » an adjoint neutron source that approximates the transmutation process. In this work, transmutation approximations are used to derive a solution for this adjoint neutron source. It is shown that these approximations are reasonably met for typical FES neutron spectra and materials over a range of irradiation scenarios. When these approximations are met, the Groupwise Transmutation (GT)-CADIS method, proposed here, can be used effectively. GT-CADIS is an implementation of the MS-CADIS method for SDR analysis that uses a series of single-energy-group irradiations to calculate the adjoint neutron source. For a simple SDR problem, GT-CADIS provides speedups of 200 100 relative to global variance reduction with the Forward-Weighted (FW)-CADIS method and 9 ± 5 • 104 relative to analog. As a result, this work shows that GT-CADIS is broadly applicable to FES problems and will significantly reduce the computational resources necessary for SDR analysis.« less

A macroscopic and microscopic study of radon exposure using Geant4 and MCNPX to estimate dose rates and DNA damage

NASA Astrophysics Data System (ADS)

van den Akker, Mary Evelyn

Radon is considered the second-leading cause of lung cancer after smoking. Epidemiological studies have been conducted in miner cohorts as well as general populations to estimate the risks associated with high and low dose exposures. There are problems with extrapolating risk estimates to low dose exposures, mainly that the dose-response curve at low doses is not well understood. Calculated dosimetric quantities give average energy depositions in an organ or a whole body, but morphological features of an individual can affect these values. As opposed to human phantom models, Computed Tomography (CT) scans provide unique, patient-specific geometries that are valuable in modeling the radiological effects of the short-lived radon progeny sources. Monte Carlo particle transport code Geant4 was used with the CT scan data to model radon inhalation in the main bronchial bifurcation. The equivalent dose rates are near the lower bounds of estimates found in the literature, depending on source volume. To complement the macroscopic study, simulations were run in a small tissue volume in Geant4-DNA toolkit. As an expansion of Geant4 meant to simulate direct physical interactions at the cellular level, the particle track structure of the radon progeny alphas can be analyzed to estimate the damage that can occur in sensitive cellular structures like the DNA molecule. These estimates of DNA double strand breaks are lower than those found in Geant4-DNA studies. Further refinements of the microscopic model are at the cutting edge of nanodosimetry research.

A tool to automatically analyze electromagnetic tracking data from high dose rate brachytherapy of breast cancer patients.

PubMed

Götz, Th I; Lahmer, G; Strnad, V; Bert, Ch; Hensel, B; Tomé, A M; Lang, E W

2017-01-01

During High Dose Rate Brachytherapy (HDR-BT) the spatial position of the radiation source inside catheters implanted into a female breast is determined via electromagnetic tracking (EMT). Dwell positions and dwell times of the radiation source are established, relative to the patient's anatomy, from an initial X-ray-CT-image. During the irradiation treatment, catheter displacements can occur due to patient movements. The current study develops an automatic analysis tool of EMT data sets recorded with a solenoid sensor to assure concordance of the source movement with the treatment plan. The tool combines machine learning techniques such as multi-dimensional scaling (MDS), ensemble empirical mode decomposition (EEMD), singular spectrum analysis (SSA) and particle filter (PF) to precisely detect and quantify any mismatch between the treatment plan and actual EMT measurements. We demonstrate that movement artifacts as well as technical signal distortions can be removed automatically and reliably, resulting in artifact-free reconstructed signals. This is a prerequisite for a highly accurate determination of any deviations of dwell positions from the treatment plan.

A tool to automatically analyze electromagnetic tracking data from high dose rate brachytherapy of breast cancer patients

PubMed Central

Lahmer, G.; Strnad, V.; Bert, Ch.; Hensel, B.; Tomé, A. M.; Lang, E. W.

2017-01-01

During High Dose Rate Brachytherapy (HDR-BT) the spatial position of the radiation source inside catheters implanted into a female breast is determined via electromagnetic tracking (EMT). Dwell positions and dwell times of the radiation source are established, relative to the patient’s anatomy, from an initial X-ray-CT-image. During the irradiation treatment, catheter displacements can occur due to patient movements. The current study develops an automatic analysis tool of EMT data sets recorded with a solenoid sensor to assure concordance of the source movement with the treatment plan. The tool combines machine learning techniques such as multi-dimensional scaling (MDS), ensemble empirical mode decomposition (EEMD), singular spectrum analysis (SSA) and particle filter (PF) to precisely detect and quantify any mismatch between the treatment plan and actual EMT measurements. We demonstrate that movement artifacts as well as technical signal distortions can be removed automatically and reliably, resulting in artifact-free reconstructed signals. This is a prerequisite for a highly accurate determination of any deviations of dwell positions from the treatment plan. PMID:28934238

Cancer radiotherapy based on femtosecond IR laser-beam filamentation yielding ultra-high dose rates and zero entrance dose.

PubMed

Meesat, Ridthee; Belmouaddine, Hakim; Allard, Jean-François; Tanguay-Renaud, Catherine; Lemay, Rosalie; Brastaviceanu, Tiberius; Tremblay, Luc; Paquette, Benoit; Wagner, J Richard; Jay-Gerin, Jean-Paul; Lepage, Martin; Huels, Michael A; Houde, Daniel

2012-09-18

Since the invention of cancer radiotherapy, its primary goal has been to maximize lethal radiation doses to the tumor volume while keeping the dose to surrounding healthy tissues at zero. Sadly, conventional radiation sources (γ or X rays, electrons) used for decades, including multiple or modulated beams, inevitably deposit the majority of their dose in front or behind the tumor, thus damaging healthy tissue and causing secondary cancers years after treatment. Even the most recent pioneering advances in costly proton or carbon ion therapies can not completely avoid dose buildup in front of the tumor volume. Here we show that this ultimate goal of radiotherapy is yet within our reach: Using intense ultra-short infrared laser pulses we can now deposit a very large energy dose at unprecedented microscopic dose rates (up to 10(11) Gy/s) deep inside an adjustable, well-controlled macroscopic volume, without any dose deposit in front or behind the target volume. Our infrared laser pulses produce high density avalanches of low energy electrons via laser filamentation, a phenomenon that results in a spatial energy density and temporal dose rate that both exceed by orders of magnitude any values previously reported even for the most intense clinical radiotherapy systems. Moreover, we show that (i) the type of final damage and its mechanisms in aqueous media, at the molecular and biomolecular level, is comparable to that of conventional ionizing radiation, and (ii) at the tumor tissue level in an animal cancer model, the laser irradiation method shows clear therapeutic benefits.

Shielding NSLS-II light source: Importance of geometry for calculating radiation levels from beam losses

NASA Astrophysics Data System (ADS)

Kramer, S. L.; Ghosh, V. J.; Breitfeller, M.; Wahl, W.

2016-11-01

Third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produces significantly higher neutron component dose to the experimental floor than a lower energy beam injection and ramped operations. Minimizing this dose will require adequate knowledge of where the miss-steered beam can occur and sufficient EM shielding close to the loss point, in order to attenuate the energy of the particles in the EM shower below the neutron production threshold (<10 MeV), which will spread the incident energy on the bulk shield walls and thereby the dose penetrating the shield walls. Designing supplemental shielding near the loss point using the analytic shielding model is shown to be inadequate because of its lack of geometry specification for the EM shower process. To predict the dose rates outside the tunnel requires detailed description of the geometry and materials that the beam losses will encounter inside the tunnel. Modern radiation shielding Monte-Carlo codes, like FLUKA, can handle this geometric description of the radiation transport process in sufficient detail, allowing accurate predictions of the dose rates expected and the ability to show weaknesses in the design before a high radiation incident occurs. The effort required to adequately define the accelerator geometry for these codes has been greatly reduced with the implementation of the graphical interface of FLAIR to FLUKA. This made the effective shielding process for NSLS-II quite accurate and reliable. The principles used to provide supplemental shielding to the NSLS-II accelerators and the lessons learned from this process are presented.

External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting.

PubMed

Yoo, Song Jae; Jang, Han-Ki; Lee, Jai-Ki; Noh, Siwan; Cho, Gyuseong

2013-01-01

For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion. Doses to the Reference Phantoms were calculated by Monte Carlo simulations with the MCNPX 2.7.0 radiation transport code for 26 mono-energy photons between 0.01 and 10 MeV. The transport calculations were performed for the source volume within the cut-off distances practically contributing to the dose rates, which were determined by a simplified calculation model. For small tissues for which the reduction of variances are difficult, the equivalent dose ratios to a larger tissue (with lower statistical errors) nearby were employed to make the calculation efficient. Empirical response functions relating photon energies, and the organ equivalent doses or the effective doses were then derived by the use of cubic-spline fitting of the resulting doses for 26 energy points. The DCFs for all radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the empirical response functions. Finally, contributions of accompanied beta particles to the skin equivalent doses and the effective doses were calculated separately and added to the DCFs. For radionuclides considered in this study, the new DCFs for the three exposure settings were within ±10 % when compared with DCFs in FGR 13.

External dose-rate conversion factors of radionuclides for air submersion, ground surface contamination and water immersion based on the new ICRP dosimetric setting

PubMed Central

Yoo, Song Jae; Jang, Han-Ki; Lee, Jai-Ki; Noh, Siwan; Cho, Gyuseong

2013-01-01

For the assessment of external doses due to contaminated environment, the dose-rate conversion factors (DCFs) prescribed in Federal Guidance Report 12 (FGR 12) and FGR 13 have been widely used. Recently, there were significant changes in dosimetric models and parameters, which include the use of the Reference Male and Female Phantoms and the revised tissue weighting factors, as well as the updated decay data of radionuclides. In this study, the DCFs for effective and equivalent doses were calculated for three exposure settings: skyshine, groundshine and water immersion. Doses to the Reference Phantoms were calculated by Monte Carlo simulations with the MCNPX 2.7.0 radiation transport code for 26 mono-energy photons between 0.01 and 10 MeV. The transport calculations were performed for the source volume within the cut-off distances practically contributing to the dose rates, which were determined by a simplified calculation model. For small tissues for which the reduction of variances are difficult, the equivalent dose ratios to a larger tissue (with lower statistical errors) nearby were employed to make the calculation efficient. Empirical response functions relating photon energies, and the organ equivalent doses or the effective doses were then derived by the use of cubic-spline fitting of the resulting doses for 26 energy points. The DCFs for all radionuclides considered important were evaluated by combining the photon emission data of the radionuclide and the empirical response functions. Finally, contributions of accompanied beta particles to the skin equivalent doses and the effective doses were calculated separately and added to the DCFs. For radionuclides considered in this study, the new DCFs for the three exposure settings were within ±10 % when compared with DCFs in FGR 13. PMID:23542764

WE-DE-201-08: Multi-Source Rotating Shield Brachytherapy Apparatus for Prostate Cancer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dadkhah, H; Wu, X; Kim, Y

Purpose: To introduce a novel multi-source rotating shield brachytherapy (RSBT) apparatus for the precise simultaneous angular and linear positioning of all partially-shielded 153Gd radiation sources in interstitial needles for treating prostate cancer. The mechanism is designed to lower the detrimental dose to healthy tissues, the urethra in particular, relative to conventional high-dose-rate brachytherapy (HDR-BT) techniques. Methods: Following needle implantation, the delivery system is docked to the patient template. Each needle is coupled to a multi-source afterloader catheter by a connector passing through a shaft. The shafts are rotated by translating a moving template between two stationary templates. Shaft walls asmore » well as moving template holes are threaded such that the resistive friction produced between the two parts exerts enough force on the shafts to bring about the rotation. Rotation of the shaft is then transmitted to the shielded source via several keys. Thus, shaft angular position is fully correlated with the position of the moving template. The catheter angles are simultaneously incremented throughout treatment as needed, and only a single 360° rotation of all catheters is needed for a full treatment. For each rotation angle, source depth in each needle is controlled by a multi-source afterloader, which is proposed as an array of belt-driven linear actuators, each of which drives a source wire. Results: Optimized treatment plans based on Monte Carlo dose calculations demonstrated RSBT with the proposed apparatus reduced urethral D{sub 1cc} below that of conventional HDR-BT by 35% for urethral dose gradient volume within 3 mm of the urethra surface. Treatment time to deliver 20 Gy with multi-source RSBT apparatus using nineteen 62.4 GBq {sup 153}Gd sources is 117 min. Conclusions: The proposed RSBT delivery apparatus in conjunction with multiple nitinol catheter-mounted platinum-shielded {sup 153}Gd sources enables a mechanically feasible urethra-sparing treatment technique for prostate cancer in a clinically reasonable timeframe.« less

An analytic linear accelerator source model for GPU-based Monte Carlo dose calculations.

PubMed

Tian, Zhen; Li, Yongbao; Folkerts, Michael; Shi, Feng; Jiang, Steve B; Jia, Xun

2015-10-21

Recently, there has been a lot of research interest in developing fast Monte Carlo (MC) dose calculation methods on graphics processing unit (GPU) platforms. A good linear accelerator (linac) source model is critical for both accuracy and efficiency considerations. In principle, an analytical source model should be more preferred for GPU-based MC dose engines than a phase-space file-based model, in that data loading and CPU-GPU data transfer can be avoided. In this paper, we presented an analytical field-independent source model specifically developed for GPU-based MC dose calculations, associated with a GPU-friendly sampling scheme. A key concept called phase-space-ring (PSR) was proposed. Each PSR contained a group of particles that were of the same type, close in energy and reside in a narrow ring on the phase-space plane located just above the upper jaws. The model parameterized the probability densities of particle location, direction and energy for each primary photon PSR, scattered photon PSR and electron PSR. Models of one 2D Gaussian distribution or multiple Gaussian components were employed to represent the particle direction distributions of these PSRs. A method was developed to analyze a reference phase-space file and derive corresponding model parameters. To efficiently use our model in MC dose calculations on GPU, we proposed a GPU-friendly sampling strategy, which ensured that the particles sampled and transported simultaneously are of the same type and close in energy to alleviate GPU thread divergences. To test the accuracy of our model, dose distributions of a set of open fields in a water phantom were calculated using our source model and compared to those calculated using the reference phase-space files. For the high dose gradient regions, the average distance-to-agreement (DTA) was within 1 mm and the maximum DTA within 2 mm. For relatively low dose gradient regions, the root-mean-square (RMS) dose difference was within 1.1% and the maximum dose difference within 1.7%. The maximum relative difference of output factors was within 0.5%. Over 98.5% passing rate was achieved in 3D gamma-index tests with 2%/2 mm criteria in both an IMRT prostate patient case and a head-and-neck case. These results demonstrated the efficacy of our model in terms of accurately representing a reference phase-space file. We have also tested the efficiency gain of our source model over our previously developed phase-space-let file source model. The overall efficiency of dose calculation was found to be improved by ~1.3-2.2 times in water and patient cases using our analytical model.

High dose-per-pulse electron beam dosimetry: Usability and dose-rate independence of EBT3 Gafchromic films.

PubMed

Jaccard, Maud; Petersson, Kristoffer; Buchillier, Thierry; Germond, Jean-François; Durán, Maria Teresa; Vozenin, Marie-Catherine; Bourhis, Jean; Bochud, François O; Bailat, Claude

2017-02-01

The aim of this study was to assess the suitability of Gafchromic EBT3 films for reference dose measurements in the beam of a prototype high dose-per-pulse linear accelerator (linac), capable of delivering electron beams with a mean dose-rate (Ḋ m ) ranging from 0.07 to 3000 Gy/s and a dose-rate in pulse (Ḋ p ) of up to 8 × 10 6 Gy/s. To do this, we evaluated the overall uncertainties in EBT3 film dosimetry as well as the energy and dose-rate dependence of their response. Our dosimetric system was composed of EBT3 Gafchromic films in combination with a flatbed scanner and was calibrated against an ionization chamber traceable to primary standard. All sources of uncertainties in EBT3 dosimetry were carefully analyzed using irradiations at a clinical radiotherapy linac. Energy dependence was investigated with the same machine by acquiring and comparing calibration curves for three different beam energies (4, 8 and 12 MeV), for doses between 0.25 and 30 Gy. Ḋ m dependence was studied at the clinical linac by changing the pulse repetition frequency (f) of the beam in order to vary Ḋ m between 0.55 and 4.40 Gy/min, while Ḋ p dependence was probed at the prototype machine for Ḋ p ranging from 7 × 10 3 to 8 × 10 6 Gy/s. Ḋ p dependence was first determined by studying the correlation between the dose measured by films and the charge of electrons measured at the exit of the machine by an induction torus. Furthermore, we compared doses from the films to independently calibrated thermo-luminescent dosimeters (TLD) that have been reported as being dose-rate independent up to such high dose-rates. We report that uncertainty below 4% (k = 2) can be achieved in the dose range between 3 and 17 Gy. Results also demonstrated that EBT3 films did not display any detectable energy dependence for electron beam energies between 4 and 12 MeV. No Ḋ m dependence was found either. In addition, we obtained excellent consistency between films and TLDs over the entire Ḋ p range attainable at the prototype linac confirming the absence of any dose-rate dependence within the investigated range (7 × 10 3 to 8 × 10 6 Gy/s). This aspect was further corroborated by the linear relationship between the dose-per-pulse (D p ) measured by films and the charge per pulse (C p ) measured at the prototype linac exit. Our study shows that the use of EBT3 Gafchromic films can be extended to reference dosimetry in pulsed electron beams with a very high dose rate. The measurement results are associated with an overall uncertainty below 4% (k = 2) and are dose-rate and energy independent. © 2016 American Association of Physicists in Medicine.

The difference of scoring dose to water or tissues in Monte Carlo dose calculations for low energy brachytherapy photon sources.

PubMed

Landry, Guillaume; Reniers, Brigitte; Pignol, Jean-Philippe; Beaulieu, Luc; Verhaegen, Frank

2011-03-01

The goal of this work is to compare D(m,m) (radiation transported in medium; dose scored in medium) and D(w,m) (radiation transported in medium; dose scored in water) obtained from Monte Carlo (MC) simulations for a subset of human tissues of interest in low energy photon brachytherapy. Using low dose rate seeds and an electronic brachytherapy source (EBS), the authors quantify the large cavity theory conversion factors required. The authors also assess whether ap plying large cavity theory utilizing the sources' initial photon spectra and average photon energy induces errors related to spatial spectral variations. First, ideal spherical geometries were investigated, followed by clinical brachytherapy LDR seed implants for breast and prostate cancer patients. Two types of dose calculations are performed with the GEANT4 MC code. (1) For several human tissues, dose profiles are obtained in spherical geometries centered on four types of low energy brachytherapy sources: 125I, 103Pd, and 131Cs seeds, as well as an EBS operating at 50 kV. Ratios of D(w,m) over D(m,m) are evaluated in the 0-6 cm range. In addition to mean tissue composition, compositions corresponding to one standard deviation from the mean are also studied. (2) Four clinical breast (using 103Pd) and prostate (using 125I) brachytherapy seed implants are considered. MC dose calculations are performed based on postimplant CT scans using prostate and breast tissue compositions. PTV D90 values are compared for D(w,m) and D(m,m). (1) Differences (D(w,m)/D(m,m)-1) of -3% to 70% are observed for the investigated tissues. For a given tissue, D(w,m)/D(m,m) is similar for all sources within 4% and does not vary more than 2% with distance due to very moderate spectral shifts. Variations of tissue composition about the assumed mean composition influence the conversion factors up to 38%. (2) The ratio of D90(w,m) over D90(m,m) for clinical implants matches D(w,m)/D(m,m) at 1 cm from the single point sources, Given the small variation with distance, using conversion factors based on the emitted photon spectrum (or its mean energy) of a given source introduces minimal error. The large differences observed between scoring schemes underline the need for guidelines on choice of media for dose reporting. Providing such guidelines is beyond the scope of this work.

Commissioning dosimetry and in situ dose mapping of a semi-industrial Cobalt-60 gamma-irradiation facility using Fricke and Ceric-cerous dosimetry system and comparison with Monte Carlo simulation data

NASA Astrophysics Data System (ADS)

Mortuza, Md Firoz; Lepore, Luigi; Khedkar, Kalpana; Thangam, Saravanan; Nahar, Arifatun; Jamil, Hossen Mohammad; Bandi, Laxminarayan; Alam, Md Khorshed

2018-03-01

Characterization of a 90 kCi (3330 TBq), semi-industrial, cobalt-60 gamma irradiator was performed by commissioning dosimetry and in-situ dose mapping experiments with Ceric-cerous and Fricke dosimetry systems. Commissioning dosimetry was carried out to determine dose distribution pattern of absorbed dose in the irradiation cell and products. To determine maximum and minimum absorbed dose, overdose ratio and dwell time of the tote boxes, homogeneous dummy product (rice husk) with a bulk density of 0.13 g/cm3 were used in the box positions of irradiation chamber. The regions of minimum absorbed dose of the tote boxes were observed in the lower zones of middle plane and maximum absorbed doses were found in the middle position of front plane. Moreover, as a part of dose mapping, dose rates in the wall positions and some selective strategic positions were also measured to carry out multiple irradiation program simultaneously, especially for low dose research irradiation program. In most of the cases, Monte Carlo simulation data, using Monte Carlo N-Particle eXtended code version MCNPX 2.7., were found to be in congruence with experimental values obtained from Ceric-cerous and Fricke dosimetry; however, in close proximity positions from the source, the dose rate variation between chemical dosimetry and MCNP was higher than distant positions.

Poster — Thur Eve — 40: Automated Quality Assurance for Remote-Afterloading High Dose Rate Brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Anthony; Ravi, Ananth

2014-08-15

High dose rate (HDR) remote afterloading brachytherapy involves sending a small, high-activity radioactive source attached to a cable to different positions within a hollow applicator implanted in the patient. It is critical that the source position within the applicator and the dwell time of the source are accurate. Daily quality assurance (QA) tests of the positional and dwell time accuracy are essential to ensure that the accuracy of the remote afterloader is not compromised prior to patient treatment. Our centre has developed an automated, video-based QA system for HDR brachytherapy that is dramatically superior to existing diode or film QAmore » solutions in terms of cost, objectivity, positional accuracy, with additional functionalities such as being able to determine source dwell time and transit time of the source. In our system, a video is taken of the brachytherapy source as it is sent out through a position check ruler, with the source visible through a clear window. Using a proprietary image analysis algorithm, the source position is determined with respect to time as it moves to different positions along the check ruler. The total material cost of the video-based system was under $20, consisting of a commercial webcam and adjustable stand. The accuracy of the position measurement is ±0.2 mm, and the time resolution is 30 msec. Additionally, our system is capable of robustly verifying the source transit time and velocity (a test required by the AAPM and CPQR recommendations), which is currently difficult to perform accurately.« less

SU-E-I-85: Absorbed Dose Estimation for a Commercially Available MicroCT Scanner

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lau, A; Ahmad, S; Chen, Y

2015-06-15

Purpose: To quantify the simulated absorbed dose delivered for a typical scan from a commercially available microCT scanner in order to aid in the dose estimation. Methods: The simulations were conducted using the Geant4 Monte Carlo Toolkit (version 10) with the standard electromagnetic classes. The Quantum FX microCT scanner (PerkinElmer, Waltham, MA) was modeled incorporating the energy fluence and angular distributions of generated photons, spatial dimensions of nominal source-to-object and source-to-detector distances. The energy distribution was measured using a spectrometer (X-123CdTe, Amptek Inc., Bedford, USA) with a 300 angular spread from the source for the 90 kVp X-ray beams withmore » no additional filtration. The nominal distances from the source to object consisted of three setups: 154.0 mm, 104.0 mm, and 51.96 mm. Our simulations recorded the dose absorbed in a cylindrical phantom of PMMA with a fixed length of 2 cm and varying radii (10, 20, 30 and 40 mm) using 100 million incident photons. The averaged absorbed dose in the object was then quantified for all setups. An exposure measurement of 417 mR was taken using a Radcal 9095 system utilizing 10×9–180 ion chamber with the given technique of 90 kVp, 63 μA, and 12 s. The exposure rate was also simulated with same setup to calculate the conversion factor of the beam current and the number of incident photons. Results: For a typical cone-beam scan with non-filtered 90kVp, the dose coefficients (the absorbed dose per mAs) were 2.614, 2.549 and 2.467 μGy/mAs under source to object distance of 104 mm for the object diameters of 10 mm, 20 mm and 30 mm, respectively. Conclusion: A look-up table was developed where an investigator can estimate the delivered dose using this particular microCT given the scanning protocol (kVp and mAs) as well as the size of the scanned object.« less

Semi-3D dosimetry of high dose rate brachytherapy using a novel Gafchromic EBT3 film-array water phantom

NASA Astrophysics Data System (ADS)

Palmer, A. L.; Nisbet, A.; Bradley, D. A.

2013-06-01

There is a need to modernise clinical brachytherapy dosimetry measurement beyond traditional point dose verification to enable appropriate quality control within 3D treatment environments. This is to keep pace with the 3D clinical and planning approaches which often include significant patient-specific optimisation away from 'standard loading patterns'. A multi-dimension measurement system is required to provide assurance of the complex 3D dose distributions, to verify equipment performance, and to enable quality audits. However, true 3D dose measurements around brachytherapy applicators are often impractical due to their complex shapes and the requirement for close measurement distances. A solution utilising an array of radiochromic film (Gafchromic EBT3) positioned within a water filled phantom is presented. A calibration function for the film has been determined over 0 to 90Gy dose range using three colour channel analysis (FilmQAPro software). Film measurements of the radial dose from a single HDR source agree with TPS and Monte Carlo calculations within 5 % up to 50 mm from the source. Film array measurements of the dose distribution around a cervix applicator agree with TPS calculations generally within 4 mm distance to agreement. The feasibility of film array measurements for semi-3D dosimetry in clinical HDR applications is demonstrated.

Characterization of a MOSkin detector for in vivo skin dose measurements during interventional radiology procedures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Safari, M. J.; Wong, J. H. D.; Ng, K. H., E-mail: ngkh@um.edu.my

2015-05-15

Purpose: The MOSkin is a MOSFET detector designed especially for skin dose measurements. This detector has been characterized for various factors affecting its response for megavoltage photon beams and has been used for patient dose measurements during radiotherapy procedures. However, the characteristics of this detector in kilovoltage photon beams and low dose ranges have not been studied. The purpose of this study was to characterize the MOSkin detector to determine its suitability for in vivo entrance skin dose measurements during interventional radiology procedures. Methods: The calibration and reproducibility of the MOSkin detector and its dependency on different radiation beam qualitiesmore » were carried out using RQR standard radiation qualities in free-in-air geometry. Studies of the other characterization parameters, such as the dose linearity and dependency on exposure angle, field size, frame rate, depth-dose, and source-to-surface distance (SSD), were carried out using a solid water phantom under a clinical x-ray unit. Results: The MOSkin detector showed good reproducibility (94%) and dose linearity (99%) for the dose range of 2 to 213 cGy. The sensitivity did not significantly change with the variation of SSD (±1%), field size (±1%), frame rate (±3%), or beam energy (±5%). The detector angular dependence was within ±5% over 360° and the dose recorded by the MOSkin detector in different depths of a solid water phantom was in good agreement with the Markus parallel plate ionization chamber to within ±3%. Conclusions: The MOSkin detector proved to be reliable when exposed to different field sizes, SSDs, depths in solid water, dose rates, frame rates, and radiation incident angles within a clinical x-ray beam. The MOSkin detector with water equivalent depth equal to 0.07 mm is a suitable detector for in vivo skin dosimetry during interventional radiology procedures.« less

Characterization of a MOSkin detector for in vivo skin dose measurements during interventional radiology procedures.

PubMed

Safari, M J; Wong, J H D; Ng, K H; Jong, W L; Cutajar, D L; Rosenfeld, A B

2015-05-01

The MOSkin is a MOSFET detector designed especially for skin dose measurements. This detector has been characterized for various factors affecting its response for megavoltage photon beams and has been used for patient dose measurements during radiotherapy procedures. However, the characteristics of this detector in kilovoltage photon beams and low dose ranges have not been studied. The purpose of this study was to characterize the MOSkin detector to determine its suitability for in vivo entrance skin dose measurements during interventional radiology procedures. The calibration and reproducibility of the MOSkin detector and its dependency on different radiation beam qualities were carried out using RQR standard radiation qualities in free-in-air geometry. Studies of the other characterization parameters, such as the dose linearity and dependency on exposure angle, field size, frame rate, depth-dose, and source-to-surface distance (SSD), were carried out using a solid water phantom under a clinical x-ray unit. The MOSkin detector showed good reproducibility (94%) and dose linearity (99%) for the dose range of 2 to 213 cGy. The sensitivity did not significantly change with the variation of SSD (± 1%), field size (± 1%), frame rate (± 3%), or beam energy (± 5%). The detector angular dependence was within ± 5% over 360° and the dose recorded by the MOSkin detector in different depths of a solid water phantom was in good agreement with the Markus parallel plate ionization chamber to within ± 3%. The MOSkin detector proved to be reliable when exposed to different field sizes, SSDs, depths in solid water, dose rates, frame rates, and radiation incident angles within a clinical x-ray beam. The MOSkin detector with water equivalent depth equal to 0.07 mm is a suitable detector for in vivo skin dosimetry during interventional radiology procedures.

A dosimetric comparison of {sup 169}Yb versus {sup 192}Ir for HDR prostate brachytherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lymperopoulou, G.; Papagiannis, P.; Sakelliou, L.

2005-12-15

For the purpose of evaluating the use of {sup 169}Yb for prostate High Dose Rate brachytherapy (HDR), a hypothetical {sup 169}Yb source is assumed with the exact same design of the new microSelectron source replacing the {sup 192}Ir active core by pure {sup 169}Yb metal. Monte Carlo simulation is employed for the full dosimetric characterization of both sources and results are compared following the AAPM TG-43 dosimetric formalism. Monte Carlo calculated dosimetry results are incorporated in a commercially available treatment planning system (SWIFT{sup TM}), which features an inverse treatment planning option based on a multiobjective dose optimization engine. The qualitymore » of prostate HDR brachytherapy using the real {sup 192}Ir and hypothetical {sup 169}Yb source is compared in a comprehensive analysis of different prostate implants in terms of the multiobjective dose optimization solutions as well as treatment quality indices such as Dose Volume Histograms (DVH) and the Conformal Index (COIN). Given that scattering overcompensates for absorption in intermediate photon energies and distances in the range of interest to prostate HDR brachytherapy, {sup 169}Yb proves at least equivalent to {sup 192}Ir irrespective of prostate volume. This has to be evaluated in view of the shielding requirements for the {sup 169}Yb energies that are minimal relative to that for {sup 192}Ir.« less

Dose-current discharge correlation analysis in a Mather type Plasma Focus device for medical applications

NASA Astrophysics Data System (ADS)

Sumini, M.; Mostacci, D.; Tartari, A.; Mazza, A.; Cucchi, G.; Isolan, L.; Buontempo, F.; Zironi, I.; Castellani, G.

2017-11-01

In a Plasma Focus device the plasma collapses into the pinch where it reaches thermonuclear conditions for a few tens of nanoseconds, becoming a multi-radiation source. The nature of the radiation generated depends on the gas filling the chamber and the device working parameters. The self-collimated electron beam generated in the backward direction with respect to the plasma motion is one of the main radiation sources of interest also for medical applications. The electron beam may be guided against a high Z material target to produce an X-ray beam. This technique offers an ultra-high dose rate source of X-rays, able to deliver during the pinch a massive dose (up to 1 Gy per discharge for the PFMA-3 test device), as measured with EBT3 GafchromicⒸfilm tissue equivalent dosimeters. Given the stochastic behavior of the discharge process, a reliable on-line estimate of the dose-delivered is a very challenging task, in some way preventing a systematic application as a potentially interesting therapy device. This work presents an approach to linking the dose registered by the EBT3 GafchromicⒸfilms with the information contained in the signal recorded during the current discharge process. Processing the signal with the Wigner-Ville distribution, a spectrogram was obtained, displaying the information on intensity at various frequency scales, identifying the band of frequencies representative of the pinch events and define some patterns correlated with the dose.

Application of computational models to estimate organ radiation dose in rainbow trout from uptake of molybdenum-99 with comparison to iodine-131.

PubMed

Martinez, N E; Johnson, T E; Pinder, J E

2016-01-01

This study compares three anatomical phantoms for rainbow trout (Oncorhynchus mykiss) for the purpose of estimating organ radiation dose and dose rates from molybdenum-99 ((99)Mo) uptake in the liver and GI tract. Model comparison and refinement is important to the process of determining accurate doses and dose rates to the whole body and the various organs. Accurate and consistent dosimetry is crucial to the determination of appropriate dose-effect relationships for use in environmental risk assessment. The computational phantoms considered are (1) a geometrically defined model employing anatomically relevant organ size and location, (2) voxel reconstruction of internal anatomy obtained from CT imaging, and (3) a new model utilizing NURBS surfaces to refine the model in (2). Dose Conversion Factors (DCFs) for whole body as well as selected organs of O. mykiss were computed using Monte Carlo modeling and combined with empirical models for predicting activity concentration to estimate dose rates and ultimately determine cumulative radiation dose (μGy) to selected organs after several half-lives of (99)Mo. The computational models provided similar results, especially for organs that were both the source and target of radiation (less than 30% difference between all models). Values in the empirical model as well as the 14 day cumulative organ doses determined from (99)Mo uptake are compared to similar models developed previously for (131)I. Finally, consideration is given to treating the GI tract as a solid organ compared to partitioning it into gut contents and GI wall, which resulted in an order of magnitude difference in estimated dose for most organs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Gamma Radiation Dose Rate in Air due to Terrestrial Radionuclides in Southern Brazil: Synthesis by Geological Units and Lithotypes Covered by the Serra do Mar Sul Aero-Geophysical Project

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bastos, Rodrigo O.; Appoloni, Carlos R.; Pinese, Jose P. P.

2008-08-07

The absorbed dose rates in air due to terrestrial radionuclides were estimated from aerial gamma spectrometric data for an area of 48,600 km{sup 2} in Southern Brazil. The source data was the Serra do Mar Sul Aero-Geophysical Project back-calibrated in a cooperative work among the Geological Survey of Brazil, the Geological Survey of Canada, and Paterson, Grant and Watson Ltd. The concentrations of eU (ppm), eTh (ppm) and K (%) were converted to dose rates in air (nGy{center_dot}h{sup -1}) by accounting for the contribution of each element's concentration. Regional variation was interpreted according to lithotypes and a synthesis was performedmore » according to the basic geological units present in the area. Higher values of total dose were estimated for felsic igneous and metamorphic rocks, with average values varying up to 119{+-}24 nGy{center_dot}h{sup -1}, obtained by Anitapolis syenite body. Sedimentary, metasedimentary and metamafic rocks presented the lower dose levels, and some beach deposits reached the lowest average total dose, 18.5{+-}8.2 nGy{center_dot}h{sup -1}. Thorium gives the main average contribution in all geological units, the highest value being reached by the nebulitic gneisses of Atuba Complex, 71{+-}23 nGy{center_dot}h{sup -1}. Potassium presents the lowest average contribution to dose rate in 53 of the 72 units analyzed, the highest contribution being obtained by intrusive alkaline bodies (28{+-}12 nGy{center_dot}h{sup -1}). The general pattern of geographic dose distribution respects well the hypotheses on geo-physicochemical behavior of radioactive elements.« less

Imaging method for monitoring delivery of high dose rate brachytherapy

DOEpatents

Weisenberger, Andrew G; Majewski, Stanislaw

2012-10-23

A method for in-situ monitoring both the balloon/cavity and the radioactive source in brachytherapy treatment utilizing using at least one pair of miniature gamma cameras to acquire separate images of: 1) the radioactive source as it is moved in the tumor volume during brachytherapy; and 2) a relatively low intensity radiation source produced by either an injected radiopharmaceutical rendering cancerous tissue visible or from a radioactive solution filling a balloon surgically implanted into the cavity formed by the surgical resection of a tumor.

A new apparatus for on-site calibration of gamma dose rate monitors

NASA Astrophysics Data System (ADS)

Zhang, Yu; Chen, Bo; Zhao, Chao; Zhuo, Weihai

2018-01-01

In order to carry out on-site calibrations of environmental gamma dose rate monitors, a new irradiation apparatus was developed in this study. The apparatus mainly consists of a piece of 137Cs source, a set of beam attenuators, and 3 built-in laser rangefinders, and it can be remotely controlled by using a laptop through WiFi network. With an activity of 4.6 × 108 Bq of 137Cs source, the reference air kerma rate could be adjusted from 0.26 μGy h-1 to 140 μGy h-1 by changing the calibration distance from 0.5 m to 5 m and using different beam attenuators (or none), and both the reproducibility and the homogeneity of reference radiation were better than 97%. The overall uncertainty of the calibration was estimated to be 6.5% (k = 2). Both the laboratory and field experiments confirmed that the calibration method met the requirements of ISO 4037-1. As the advantages of portability and simplicity, it is considered that the new irradiation apparatus is applicable to stationary gamma radiation monitors for on-site calibration.

238PuO 2 Fuel and Dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayo, Douglas R.; Rawool-Sullivan, Mohini; Garner, Scott Edward

2016-06-01

238Pu is an ideal material for use as a heat source with its half-life of 87.7 years and copious particle emissions. 238Pu radioisotope thermoelectric generators (RTGs) have found use for pacemakers, Apollo Space missions, Mars rovers, and Voyager spacecraft. In evaluating the dose to personnel and components near a 238Pu-based RTG, a number of additional nuclides and their daughter products must be considered to get an accurate estimate for γ-dose, and the amount of 17O and 18O for the neutron-dose must be considered. This paper looks at the contributing nuclides and their daughter products that add the most to themore » dose rates.« less

Detailed source term estimation of atmospheric release during the Fukushima Dai-ichi nuclear power plant accident by coupling atmospheric and oceanic dispersion models

NASA Astrophysics Data System (ADS)

Katata, Genki; Chino, Masamichi; Terada, Hiroaki; Kobayashi, Takuya; Ota, Masakazu; Nagai, Haruyasu; Kajino, Mizuo

2014-05-01

Temporal variations of release amounts of radionuclides during the Fukushima Dai-ichi Nuclear Power Plant (FNPP1) accident and their dispersion process are essential to evaluate the environmental impacts and resultant radiological doses to the public. Here, we estimated a detailed time trend of atmospheric releases during the accident by combining environmental monitoring data and coupling atmospheric and oceanic dispersion simulations by WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information) and SEA-GEARN developed by the authors. New schemes for wet, dry, and fog depositions of radioactive iodine gas (I2 and CH3I) and other particles (I-131, Te-132, Cs-137, and Cs-134) were incorporated into WSPEEDI-II. The deposition calculated by WSPEEDI-II was used as input data of ocean dispersion calculations by SEA-GEARN. The reverse estimation method based on the simulation by both models assuming unit release rate (1 Bq h-1) was adopted to estimate the source term at the FNPP1 using air dose rate, and air sea surface concentrations. The results suggested that the major release of radionuclides from the FNPP1 occurred in the following periods during March 2011: afternoon on the 12th when the venting and hydrogen explosion occurred at Unit 1, morning on the 13th after the venting event at Unit 3, midnight on the 14th when several openings of SRV (steam relief valve) were conducted at Unit 2, morning and night on the 15th, and morning on the 16th. The modified WSPEEDI-II using the newly estimated source term well reproduced local and regional patterns of air dose rate and surface deposition of I-131 and Cs-137 obtained by airborne observations. Our dispersion simulations also revealed that the highest radioactive contamination areas around FNPP1 were created from 15th to 16th March by complicated interactions among rainfall (wet deposition), plume movements, and phase properties (gas or particle) of I-131 and release rates associated with reactor pressure variations in Units 2 and 3.

Very low dose gamma irradiation stimulates gaseous exchange and carboxylation efficiency, but inhibits vascular sap flow in groundnut (Arachis hypogaea L.).

PubMed

Ahuja, Sumedha; Singh, Bhupinder; Gupta, Vijay Kumar; Singhal, R K; Venu Babu, P

2014-02-01

An experiment was carried out to determine the effect of low dose gamma radiation on germination, plant growth, nitrogen and carbon fixation and carbon flow and release characteristics of groundnut. Dry seeds of groundnut variety Trombay groundnut 37A (TG 37A), a radio mutant type developed by Bhabha Atomic Research Centre (BARC), Mumbai, India, were subjected to the pre-sowing treatment of gamma radiation within low to high dose physiological range, i.e., 0.0, 0.0082, 0.0164. 0.0328, 0.0656, 0.1312, 5, 25, 100, 500 Gray (Gy) from a cobalt source ((60)Co). Observations were recorded for the radiation effect on percentage germination, vigour, gas exchange attributes such as photosynthetic rate, stomatal conductance and transpiration rate, chlorophyll content, root exudation in terms of (14)C release, vascular sap flow rate and activities of rate defining carbon and nitrogen assimilating enzymes such as ribulose-1,5-bisphosphate carboxylase (rubisco) and nitrate reductase (NR). Seed germination was increased by 10-25% at the lower doses up to 5 Gy while the improvement in plant vigour in the same dose range was much higher (22-84%) than the unirradiated control. For radiation exposure above 5 Gy, a dose-dependent decline in germination and plant vigour was measured. No significant effect was observed on the photosynthesis at radiation exposure below 5 Gy but above 5 Gy dose there was a decline in the photosynthetic rate. Stomatal conductance and transpiration rate, however, were only inhibited at a high dose of 500 Gy. Leaf rubisco activity and NR activities remained unaffected at all the investigated doses of gamma irradiation. Mean root exudation and sap flow rate of the irradiated plants, irrespective of the dose, was reduced over the unirradiated control more so in a dose-dependent manner. Results indicated that a very low dose of gamma radiation, in centigray to gray range, did not pose any threat and in fact stimulated metabolic functions in such a way to aid growth and development of groundnut plants. It further showed that the radiation threshold for the gas exchange traits and rubisco activity, which ultimately determine the plant health and yield, were higher than compared to the other metabolic attributes and were well beyond 500 Gy and that the dose range above 500 Gy should be targeted to measure lethal effects of radiation on carbon assimilation attributes in leguminous crops, in general, and groundnut in particular.

Undulator Radiation Damage Experience at LCLS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nuhn, H. D.; Field, C.; Mao, S.

2015-01-06

The SLAC National Accelerator Laboratory has been running the Linac Coherent Light Source (LCLS), the first x-ray Free Electron Laser since 2009. Undulator magnet damage from radiation, produced by the electron beam traveling through the 133-m long straight vacuum tube, has been and is a concern. A damage measurement experiment has been performed in 2007 in order to obtain dose versus damage calibrations. Radiation reduction and detection devices have been integrated into the LCLS undulator system. The accumulated radiation dose rate was continuously monitored and recorded. In addition, undulator segments have been routinely removed from the beamline to be checkedmore » for magnetic (50 ppm, rms) and mechanic (about 0.25 µm, rms) changes. A reduction in strength of the undulator segments is being observed, at a level, which is now clearly above the noise. Recently, potential sources for the observed integrated radiation levels have been investigated. The paper discusses the results of these investigation as well as comparison between observed damage and measured dose accumulations and discusses, briefly, strategies for the new LCLS-II upgrade, which will be operating at more than 300 times larger beam rate.« less

Relative dosimetrical verification in high dose rate brachytherapy using two-dimensional detector array IMatriXX

PubMed Central

Manikandan, A.; Biplab, Sarkar; David, Perianayagam A.; Holla, R.; Vivek, T. R.; Sujatha, N.

2011-01-01

For high dose rate (HDR) brachytherapy, independent treatment verification is needed to ensure that the treatment is performed as per prescription. This study demonstrates dosimetric quality assurance of the HDR brachytherapy using a commercially available two-dimensional ion chamber array called IMatriXX, which has a detector separation of 0.7619 cm. The reference isodose length, step size, and source dwell positional accuracy were verified. A total of 24 dwell positions, which were verified for positional accuracy gave a total error (systematic and random) of –0.45 mm, with a standard deviation of 1.01 mm and maximum error of 1.8 mm. Using a step size of 5 mm, reference isodose length (the length of 100% isodose line) was verified for single and multiple catheters of same and different source loadings. An error ≤1 mm was measured in 57% of tests analyzed. Step size verification for 2, 3, 4, and 5 cm was performed and 70% of the step size errors were below 1 mm, with maximum of 1.2 mm. The step size ≤1 cm could not be verified by the IMatriXX as it could not resolve the peaks in dose profile. PMID:21897562

Measurements and PHITS Monte Carlo Estimations of Residual Activities Induced by the 181 MeV Proton Beam in the Injection Area at J-PARC RCS Ring

NASA Astrophysics Data System (ADS)

Yamakawa, Emi; Yoshimoto, Masahiro; Kinsho, Michikazu

At the injection area of the RCS ring in the J-PARC, residual gamma dose at the rectangular ceramic ducts, especially immediately downstream of the charge-exchanged foil, has increased with the output beam power. In order to investigate the cause of high residual activities, residual gamma dose and radioactive sources produced at the exterior surface of the ducts have been measured by a GM survey meter and a handy type of Germanium (Ge) semiconductor detector in the case of 181 MeV injected proton beam energy. With these measurements, it is revealed that the radioactive sources produced by nuclear reactions cause the high activities at the injection area. For a better understanding of phenomena in the injection area, various simulations have been done with the PHITS Monte Carlo code. The distribution of radioactive sources and residual gamma dose rate obtained by the calculations are consistent with the measurement results. With this consistency, secondary neutrons and protons derived from nuclear reactions at the charge-exchanged foil are the dominant cause to high residual gamma dose at the ceramic ducts in the injection area. These measurements and calculations are unique approaches to reveal the cause of high residual dose around the foil. This study is essential for the future of high-intensity proton accelerators using a stripping foil.

Characterization of MOSFET detectors for in vivo dosimetry in interventional radiology and for dose reconstruction in case of overexposure.

PubMed

Bassinet, Céline; Huet, Christelle; Baumann, Marion; Etard, Cécile; Réhel, Jean-Luc; Boisserie, Gilbert; Debroas, Jacques; Aubert, Bernard; Clairand, Isabelle

2013-04-01

As MOSFET (Metal Oxide Semiconductor Field Effect Transistor) detectors allow dose measurements in real time, the interest in these dosimeters is growing. The aim of this study was to investigate the dosimetric properties of commercially available TN-502RD-H MOSFET silicon detectors (Best Medical Canada, Ottawa, Canada) in order to use them for in vivo dosimetry in interventional radiology and for dose reconstruction in case of overexposure. Reproducibility of the measurements, dose rate dependence, and dose response of the MOSFET detectors have been studied with a Co source. Influence of the dose rate, frequency, and pulse duration on MOSFET responses has also been studied in pulsed x-ray fields. Finally, in order to validate the integrated dose given by MOSFET detectors, MOSFETs and TLDs (LiF:Mg,Cu,P) were fixed on an Alderson-Rando phantom in the conditions of an interventional neuroradiology procedure, and their responses have been compared. The results of this study show the suitability of MOSFET detectors for in vivo dosimetry in interventional radiology and for dose reconstruction in case of accident, provided a well-corrected energy dependence, a pulse duration equal to or higher than 10 ms, and an optimized contact between the detector and the skin of the patient are achieved.

Recovery of damage in rad-hard MOS devices during and after irradiation by electrons, protons, alphas, and gamma rays

NASA Technical Reports Server (NTRS)

Brucker, G. J.; Van Gunten, O.; Stassinopoulos, E. G.; Shapiro, P.; August, L. S.; Jordan, T. M.

1983-01-01

This paper reports on the recovery properties of rad-hard MOS devices during and after irradiation by electrons, protons, alphas, and gamma rays. The results indicated that complex recovery properties controlled the damage sensitivities of the tested parts. The results also indicated that damage sensitivities depended on dose rate, total dose, supply bias, gate bias, transistor type, radiation source, and particle energy. The complex nature of these dependencies make interpretation of LSI device performance in space (exposure to entire electron and proton spectra) difficult, if not impossible, without respective ground tests and analyses. Complete recovery of n-channel shifts was observed, in some cases within hours after irradiation, with equilibrium values of threshold voltages greater than their pre-irradiation values. This effect depended on total dose, radiation source, and gate bias during exposure. In contrast, the p-channel shifts recovered only 20 percent within 30 days after irradiation.

A single-source photon source model of a linear accelerator for Monte Carlo dose calculation

PubMed Central

Glatting, Gerhard; Wenz, Frederik; Fleckenstein, Jens

2017-01-01

Purpose To introduce a new method of deriving a virtual source model (VSM) of a linear accelerator photon beam from a phase space file (PSF) for Monte Carlo (MC) dose calculation. Materials and methods A PSF of a 6 MV photon beam was generated by simulating the interactions of primary electrons with the relevant geometries of a Synergy linear accelerator (Elekta AB, Stockholm, Sweden) and recording the particles that reach a plane 16 cm downstream the electron source. Probability distribution functions (PDFs) for particle positions and energies were derived from the analysis of the PSF. These PDFs were implemented in the VSM using inverse transform sampling. To model particle directions, the phase space plane was divided into a regular square grid. Each element of the grid corresponds to an area of 1 mm2 in the phase space plane. The average direction cosines, Pearson correlation coefficient (PCC) between photon energies and their direction cosines, as well as the PCC between the direction cosines were calculated for each grid element. Weighted polynomial surfaces were then fitted to these 2D data. The weights are used to correct for heteroscedasticity across the phase space bins. The directions of the particles created by the VSM were calculated from these fitted functions. The VSM was validated against the PSF by comparing the doses calculated by the two methods for different square field sizes. The comparisons were performed with profile and gamma analyses. Results The doses calculated with the PSF and VSM agree to within 3% /1 mm (>95% pixel pass rate) for the evaluated fields. Conclusion A new method of deriving a virtual photon source model of a linear accelerator from a PSF file for MC dose calculation was developed. Validation results show that the doses calculated with the VSM and the PSF agree to within 3% /1 mm. PMID:28886048

A single-source photon source model of a linear accelerator for Monte Carlo dose calculation.

PubMed

Nwankwo, Obioma; Glatting, Gerhard; Wenz, Frederik; Fleckenstein, Jens

2017-01-01

To introduce a new method of deriving a virtual source model (VSM) of a linear accelerator photon beam from a phase space file (PSF) for Monte Carlo (MC) dose calculation. A PSF of a 6 MV photon beam was generated by simulating the interactions of primary electrons with the relevant geometries of a Synergy linear accelerator (Elekta AB, Stockholm, Sweden) and recording the particles that reach a plane 16 cm downstream the electron source. Probability distribution functions (PDFs) for particle positions and energies were derived from the analysis of the PSF. These PDFs were implemented in the VSM using inverse transform sampling. To model particle directions, the phase space plane was divided into a regular square grid. Each element of the grid corresponds to an area of 1 mm2 in the phase space plane. The average direction cosines, Pearson correlation coefficient (PCC) between photon energies and their direction cosines, as well as the PCC between the direction cosines were calculated for each grid element. Weighted polynomial surfaces were then fitted to these 2D data. The weights are used to correct for heteroscedasticity across the phase space bins. The directions of the particles created by the VSM were calculated from these fitted functions. The VSM was validated against the PSF by comparing the doses calculated by the two methods for different square field sizes. The comparisons were performed with profile and gamma analyses. The doses calculated with the PSF and VSM agree to within 3% /1 mm (>95% pixel pass rate) for the evaluated fields. A new method of deriving a virtual photon source model of a linear accelerator from a PSF file for MC dose calculation was developed. Validation results show that the doses calculated with the VSM and the PSF agree to within 3% /1 mm.

FLUKA simulation of TEPC response to cosmic radiation.

PubMed

Beck, P; Ferrari, A; Pelliccioni, M; Rollet, S; Villari, R

2005-01-01

The aircrew exposure to cosmic radiation can be assessed by calculation with codes validated by measurements. However, the relationship between doses in the free atmosphere, as calculated by the codes and from results of measurements performed within the aircraft, is still unclear. The response of a tissue-equivalent proportional counter (TEPC) has already been simulated successfully by the Monte Carlo transport code FLUKA. Absorbed dose rate and ambient dose equivalent rate distributions as functions of lineal energy have been simulated for several reference sources and mixed radiation fields. The agreement between simulation and measurements has been well demonstrated. In order to evaluate the influence of aircraft structures on aircrew exposure assessment, the response of TEPC in the free atmosphere and on-board is now simulated. The calculated results are discussed and compared with other calculations and measurements.

Quality control in interstitial brachytherapy of the breast using pulsed dose rate: treatment planning and dose delivery with an Ir-192 afterloading system.

PubMed

Mangold, C A; Rijnders, A; Georg, D; Van Limbergen, E; Pötter, R; Huyskens, D

2001-01-01

In the Radiotherapy Department of Leuven, about 20% of all breast cancer patients treated with breast conserving surgery and external radiotherapy receive an additional boost with pulsed dose rate (PDR) Ir-192 brachytherapy. An investigation was performed to assess the accuracy of the delivered PDR brachytherapy treatment. Secondly, the feasibility of in vivo measurements during PDR dose delivery was investigated. Two phantoms are manufactured to mimic a breast, one for thermoluminescent dosimetry (TLD) measurements, and one for dosimetry using radiochromic films. The TLD phantom allows measurements at 34 dose points in three planes including the basal dose points. The film phantom is designed in such a way that films can be positioned in a plane parallel and orthogonal to the needles. The dose distributions calculated with the TPS are in good agreement with both TLD and radiochromic film measurements (average deviations of point doses <+/-5%). However, close to the interface tissue-air the dose is overestimated by the TPS since it neglects the finite size of a breast and the associated lack of backscatter (average deviations of point doses -14%). Most deviations between measured and calculated doses, are in the order of magnitude of the uncertainty associated with the source strength specification, except for the point doses measured close to the skin. In vivo dosimetry during PDR brachytherapy treatment was found to be a valuable procedure to detect large errors, e.g. errors caused by an incorrect data transfer.

In vivo dose verification method in catheter based high dose rate brachytherapy.

PubMed

Jaselskė, Evelina; Adlienė, Diana; Rudžianskas, Viktoras; Urbonavičius, Benas Gabrielis; Inčiūra, Arturas

2017-12-01

In vivo dosimetry is a powerful tool for dose verification in radiotherapy. Its application in high dose rate (HDR) brachytherapy is usually limited to the estimation of gross errors, due to inability of the dosimetry system/ method to record non-uniform dose distribution in steep dose gradient fields close to the radioactive source. In vivo dose verification in interstitial catheter based HDR brachytherapy is crucial since the treatment is performed inserting radioactive source at the certain positions within the catheters that are pre-implanted into the tumour. We propose in vivo dose verification method for this type of brachytherapy treatment which is based on the comparison between experimentally measured and theoretical dose values calculated at well-defined locations corresponding dosemeter positions in the catheter. Dose measurements were performed using TLD 100-H rods (6 mm long, 1 mm diameter) inserted in a certain sequences into additionally pre-implanted dosimetry catheter. The adjustment of dosemeter positioning in the catheter was performed using reconstructed CT scans of patient with pre-implanted catheters. Doses to three Head&Neck and one Breast cancer patient have been measured during several randomly selected treatment fractions. It was found that the average experimental dose error varied from 4.02% to 12.93% during independent in vivo dosimetry control measurements for selected Head&Neck cancer patients and from 7.17% to 8.63% - for Breast cancer patient. Average experimental dose error was below the AAPM recommended margin of 20% and did not exceed the measurement uncertainty of 17.87% estimated for this type of dosemeters. Tendency of slightly increasing average dose error was observed in every following treatment fraction of the same patient. It was linked to the changes of theoretically estimated dosemeter positions due to the possible patient's organ movement between different treatment fractions, since catheter reconstruction was performed for the first treatment fraction only. These findings indicate potential for further average dose error reduction in catheter based brachytherapy by at least 2-3% in the case that catheter locations will be adjusted before each following treatment fraction, however it requires more detailed investigation. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Purification of sulfide-alkali effluent with the aid of ionizing radiation. [Gamma radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petryaev, E.P.; Gerasimovich, O.A.; Kovalevskaya, A.M.

1984-03-01

The treatment of sulfide-alkali effluent under the effect of ionizing radiation was investigated. The source was an LMB-..gamma..-1M ..gamma..-apparatus with /sup 137/Cs source. The dose rate was 52 rad/s. Irradiation was done in glass ampules and in vessels allowing bubbling with air and irradiation to be carried out at the same time. 7 references, 1 figure, 1 table.

The space radiation environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robbins, D E

There are three primary sources of space radiation: galactic cosmic rays (GCR), trapped belt radiation, and solar particle events (SPE). All are composed of ions, the nuclei of atoms. Their energies range from a few MeV u{sup -1} to over a GeV u{sup -1}. These ions can fragment when they interact with spacecraft materials and produce energetic neutrons and ions of lower atomic mass. Absorbed dose rates inside a typical spacecraft (like the Space Shuttle) in a low inclination (28.5 degrees) orbit range between 0.05 and 2 mGy d{sup -1} depending on the altitude and flight inclination (angle of orbitmore » with the equator). The quality factor of radiation in orbit depends on the relative contributions of trapped belt radiation and GCR, and the dose rate varies both with orbital altitude and inclination. The corresponding equivalent dose rate ranges between 0.1 and 4 mSv d{sup -1}. In high inclination orbits, like that of the Mir Space Station and as is planned for the International Space Station, blood-forming organ (BFO) equivalent dose rates as high as 1.5 mSv d{sup -1}. Thus, on a 1 y mission, a crew member could obtain a total dose of 0.55 Sv. Maximum equivalent dose rates measured in high altitude passes through the South Atlantic Anomaly (SAA) were 10 mSv h{sup -1}. For an interplanetary space mission (e.g., to Mars) annual doses from GCR alone range between 150 mSv y{sup -1} at solar maximum and 580 mSv y{sup -1} at solar minimum. Large SPE, like the October 1989 series, are more apt to occur in the years around solar maximum. In free space, such an event could contribute another 300 mSv, assuming that a warning system and safe haven can be effectively used with operational procedures to minimize crew exposures. Thus, the total dose for a 3 y mission to Mars could exceed 2 Sv.« less

Dosimetric characterization of two radium sources for retrospective dosimetry studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Candela-Juan, C., E-mail: ccanjuan@gmail.com; Karlsson, M.; Lundell, M.

2015-05-15

Purpose: During the first part of the 20th century, {sup 226}Ra was the most used radionuclide for brachytherapy. Retrospective accurate dosimetry, coupled with patient follow up, is important for advancing knowledge on long-term radiation effects. The purpose of this work was to dosimetrically characterize two {sup 226}Ra sources, commonly used in Sweden during the first half of the 20th century, for retrospective dose–effect studies. Methods: An 8 mg {sup 226}Ra tube and a 10 mg {sup 226}Ra needle, used at Radiumhemmet (Karolinska University Hospital, Stockholm, Sweden), from 1925 to the 1960s, were modeled in two independent Monte Carlo (MC) radiationmore » transport codes: GEANT4 and MCNP5. Absorbed dose and collision kerma around the two sources were obtained, from which the TG-43 parameters were derived for the secular equilibrium state. Furthermore, results from this dosimetric formalism were compared with results from a MC simulation with a superficial mould constituted by five needles inside a glass casing, placed over a water phantom, trying to mimic a typical clinical setup. Calculated absorbed doses using the TG-43 formalism were also compared with previously reported measurements and calculations based on the Sievert integral. Finally, the dose rate at large distances from a {sup 226}Ra point-like-source placed in the center of 1 m radius water sphere was calculated with GEANT4. Results: TG-43 parameters [including g{sub L}(r), F(r, θ), Λ, and s{sub K}] have been uploaded in spreadsheets as additional material, and the fitting parameters of a mathematical curve that provides the dose rate between 10 and 60 cm from the source have been provided. Results from TG-43 formalism are consistent within the treatment volume with those of a MC simulation of a typical clinical scenario. Comparisons with reported measurements made with thermoluminescent dosimeters show differences up to 13% along the transverse axis of the radium needle. It has been estimated that the uncertainty associated to the absorbed dose within the treatment volume is 10%–15%, whereas uncertainty of absorbed dose to distant organs is roughly 20%–25%. Conclusions: The results provided here facilitate retrospective dosimetry studies of {sup 226}Ra using modern treatment planning systems, which may be used to improve knowledge on long term radiation effects. It is surely important for the epidemiologic studies to be aware of the estimated uncertainty provided here before extracting their conclusions.« less

Design of YCF-1 mobile γ irradiator

NASA Astrophysics Data System (ADS)

Hehu, Zhang; Chuanzhen, Wang

1993-07-01

YCF-1 Mobile irradiator is designed by BINE of China. It has been put into running in YanJi city of Jilin province. It is able to be moved to border and distance places and area lumped and spreading out of agricultural products to service. It can play a important role in demonstration and extending irradiation technology in food irradiation, disinfestation, sterilization and quarantine, etc. This paper describes the features and design considerations of mobile irradiator. This irradiator adopted Cesium-137 source. The design capacity of loading source is 9.25PBq (250kCi), A half-time of Cs- 137 is 30.2 years long, exchanging source is not needed utilization rate of energy is higher, and the shielding is thinner, The Weight is lighter, The dose rate on the surface of it is 0.0025mSv/h in accordance with national standard. The internal size of irradiation room is 1800×1800×900mm (L×W×H), The sheilding of irradiation room is a steel shell filled with lead. The thickness of lead is 18cm. The irradiator is installed on a special flat truck. The size of the truck is 7000×3400×4200mm (L×W×H). The weight of irradiator is more than 80 150kw. The main components and parts of irradiator are: source, source racks and hoist, irradiation chamber, storage source chamber, the product's transport system, dose monitoring system, ventilation system and safety interlock system, etc.

Impact of external carbon dose on the removal of micropollutants using methanol and ethanol in post-denitrifying Moving Bed Biofilm Reactors.

PubMed

Torresi, Elena; Escolà Casas, Mònica; Polesel, Fabio; Plósz, Benedek G; Christensson, Magnus; Bester, Kai

2017-01-01

Addition of external carbon sources to post-denitrification systems is frequently used in wastewater treatment plants to enhance nitrate removal. However, little is known about the fate of micropollutants in post-denitrification systems and the influence of external carbon dosing on their removal. In this study, we assessed the effects of two different types and availability of commonly used carbon sources -methanol and ethanol- on the removal of micropollutants in biofilm systems. Two laboratory-scale moving bed biofilm reactors (MBBRs), containing AnoxKaldnes K1 carriers with acclimated biofilm from full-scale systems, were operated in continuous-flow using wastewater dosed with methanol and ethanol, respectively. Batch experiments with 22 spiked pharmaceuticals were performed to assess removal kinetics. Acetyl-sulfadiazine, atenolol, citalopram, propranolol and trimethoprim were easily biotransformed in both MBBRs (biotransformations rate constants k bio between 1.2 and 12.9 L g biomass -1  d -1 ), 13 compounds were moderately biotransformed (rate constants between 0.2 and 2 L g biomass -1  d -1 ) and 4 compounds were recalcitrant. The methanol-dosed MBBR showed higher k bio (e.g., 1.5-2.5-fold) than in the ethanol-dosed MBBR for 9 out of the 22 studied compounds, equal k bio for 10 compounds, while 3 compounds (i.e., targeted sulfonamides) were biotransformed faster in the ethanol-dosed MBBR. While biotransformation of most of the targeted compounds followed first-order kinetics, removal of venlafaxine, carbamazepine, sulfamethoxazole and sulfamethizole could be described with a cometabolic model. Analyses of the microbial composition in the biofilms using 16S rRNA amplicon sequencing revealed that the methanol-dosed MBBR contained higher microbial richness than the one dosed with ethanol, suggesting that improved biotransformation of targeted compounds could be associated with higher microbial richness. During continuous-flow operation, at conditions representative of full-scale denitrification systems (hydraulic residence time = 2 h), the removal efficiencies of micropollutants were below 35% in both MBBRs, with the exception of atenolol and trimethoprim (>80%). Overall, this study demonstrated that MBBRs used for post-denitrification could be optimized to enhance the biotransformation of a number of micropollutants by accounting for optimal carbon sources and extended residence time. Copyright © 2016 Elsevier Ltd. All rights reserved.

A dosimetric uncertainty analysis for photon-emitting brachytherapy sources: Report of AAPM Task Group No. 138 and GEC-ESTRO

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeWerd, Larry A.; Ibbott, Geoffrey S.; Meigooni, Ali S.

2011-02-15

This report addresses uncertainties pertaining to brachytherapy single-source dosimetry preceding clinical use. The International Organization for Standardization (ISO) Guide to the Expression of Uncertainty in Measurement (GUM) and the National Institute of Standards and Technology (NIST) Technical Note 1297 are taken as reference standards for uncertainty formalism. Uncertainties in using detectors to measure or utilizing Monte Carlo methods to estimate brachytherapy dose distributions are provided with discussion of the components intrinsic to the overall dosimetric assessment. Uncertainties provided are based on published observations and cited when available. The uncertainty propagation from the primary calibration standard through transfer to the clinicmore » for air-kerma strength is covered first. Uncertainties in each of the brachytherapy dosimetry parameters of the TG-43 formalism are then explored, ending with transfer to the clinic and recommended approaches. Dosimetric uncertainties during treatment delivery are considered briefly but are not included in the detailed analysis. For low- and high-energy brachytherapy sources of low dose rate and high dose rate, a combined dosimetric uncertainty <5% (k=1) is estimated, which is consistent with prior literature estimates. Recommendations are provided for clinical medical physicists, dosimetry investigators, and source and treatment planning system manufacturers. These recommendations include the use of the GUM and NIST reports, a requirement of constancy of manufacturer source design, dosimetry investigator guidelines, provision of the lowest uncertainty for patient treatment dosimetry, and the establishment of an action level based on dosimetric uncertainty. These recommendations reflect the guidance of the American Association of Physicists in Medicine (AAPM) and the Groupe Europeen de Curietherapie-European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) for their members and may also be used as guidance to manufacturers and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments.« less

A dosimetric uncertainty analysis for photon-emitting brachytherapy sources: Report of AAPM Task Group No. 138 and GEC-ESTRO

PubMed Central

DeWerd, Larry A.; Ibbott, Geoffrey S.; Meigooni, Ali S.; Mitch, Michael G.; Rivard, Mark J.; Stump, Kurt E.; Thomadsen, Bruce R.; Venselaar, Jack L. M.

2011-01-01

This report addresses uncertainties pertaining to brachytherapy single-source dosimetry preceding clinical use. The International Organization for Standardization (ISO) Guide to the Expression of Uncertainty in Measurement (GUM) and the National Institute of Standards and Technology (NIST) Technical Note 1297 are taken as reference standards for uncertainty formalism. Uncertainties in using detectors to measure or utilizing Monte Carlo methods to estimate brachytherapy dose distributions are provided with discussion of the components intrinsic to the overall dosimetric assessment. Uncertainties provided are based on published observations and cited when available. The uncertainty propagation from the primary calibration standard through transfer to the clinic for air-kerma strength is covered first. Uncertainties in each of the brachytherapy dosimetry parameters of the TG-43 formalism are then explored, ending with transfer to the clinic and recommended approaches. Dosimetric uncertainties during treatment delivery are considered briefly but are not included in the detailed analysis. For low- and high-energy brachytherapy sources of low dose rate and high dose rate, a combined dosimetric uncertainty <5% (k=1) is estimated, which is consistent with prior literature estimates. Recommendations are provided for clinical medical physicists, dosimetry investigators, and source and treatment planning system manufacturers. These recommendations include the use of the GUM and NIST reports, a requirement of constancy of manufacturer source design, dosimetry investigator guidelines, provision of the lowest uncertainty for patient treatment dosimetry, and the establishment of an action level based on dosimetric uncertainty. These recommendations reflect the guidance of the American Association of Physicists in Medicine (AAPM) and the Groupe Européen de Curiethérapie–European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) for their members and may also be used as guidance to manufacturers and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments. PMID:21452716

A dosimetric uncertainty analysis for photon-emitting brachytherapy sources: report of AAPM Task Group No. 138 and GEC-ESTRO.

PubMed

DeWerd, Larry A; Ibbott, Geoffrey S; Meigooni, Ali S; Mitch, Michael G; Rivard, Mark J; Stump, Kurt E; Thomadsen, Bruce R; Venselaar, Jack L M

2011-02-01

This report addresses uncertainties pertaining to brachytherapy single-source dosimetry preceding clinical use. The International Organization for Standardization (ISO) Guide to the Expression of Uncertainty in Measurement (GUM) and the National Institute of Standards and Technology (NIST) Technical Note 1297 are taken as reference standards for uncertainty formalism. Uncertainties in using detectors to measure or utilizing Monte Carlo methods to estimate brachytherapy dose distributions are provided with discussion of the components intrinsic to the overall dosimetric assessment. Uncertainties provided are based on published observations and cited when available. The uncertainty propagation from the primary calibration standard through transfer to the clinic for air-kerma strength is covered first. Uncertainties in each of the brachytherapy dosimetry parameters of the TG-43 formalism are then explored, ending with transfer to the clinic and recommended approaches. Dosimetric uncertainties during treatment delivery are considered briefly but are not included in the detailed analysis. For low- and high-energy brachytherapy sources of low dose rate and high dose rate, a combined dosimetric uncertainty <5% (k=1) is estimated, which is consistent with prior literature estimates. Recommendations are provided for clinical medical physicists, dosimetry investigators, and source and treatment planning system manufacturers. These recommendations include the use of the GUM and NIST reports, a requirement of constancy of manufacturer source design, dosimetry investigator guidelines, provision of the lowest uncertainty for patient treatment dosimetry, and the establishment of an action level based on dosimetric uncertainty. These recommendations reflect the guidance of the American Association of Physicists in Medicine (AAPM) and the Groupe Européen de Curiethérapie-European Society for Therapeutic Radiology and Oncology (GEC-ESTRO) for their members and may also be used as guidance to manufacturers and regulatory agencies in developing good manufacturing practices for sources used in routine clinical treatments.

Short Communication: Rheological properties of blood serum of rats after irradiation with different gamma radiation doses in vivo.

PubMed

Abdelhalim, Mohamed Anwar K; Moussa, Sherif Aa; Ms, Al-Ayed

2016-01-01

The blood serum rheological properties open the door to find suitable radio-protectors and convenient therapy for many cases of radiation exposure. The present study aimed to investigate the rheological properties of rat blood serum at wide range of shear rates after whole body irradiation with different gamma radiation doses in vivo. Healthy male rats were divided into five groups; one control group and 4 irradiated groups. The irradiation process was carried out using Co60 source with dose rate of 0.883cG/sec. Several rheological parameters were measured using Brookfield LVDV-III Programmable rheometer. A significant increase in viscosity and shear stress was observed with 25 and 50Gy corresponding to each shear rate compared with the control; while a significant decrease observed with 75 and 100Gy. The viscosity exhibited a Non-Newtonian behaviour with the shear rate while shear stress values were linearly related with shear rate. The decrease in blood viscosity might be attributed to changes in molecular weight, pH sensitivity and protein structure. The changes in rheological properties of irradiated rats' blood serum might be attributed to destruction changes in the haematological and dimensional properties of rats' blood products.

Air core detectors for Cerenkov-free scintillation dosimetry of brachytherapy β-sources.

PubMed

Eichmann, Marion; Thomann, Benedikt

2017-09-01

Plastic scintillation detectors are used for dosimetry in small radiation fields with high dose gradients, e.g., provided by β-emitting sources like 106 Ru/ 106 Rh eye plaques. A drawback is a background signal caused by Cerenkov radiation generated by electrons passing the optical fibers (light guides) of this dosimetry system. Common approaches to correct for the Cerenkov signal are influenced by uncertainties resulting from detector positioning and calibration procedures. A different approach to avoid any correction procedure is to suppress the Cerenkov signal by replacing the solid core optical fiber with an air core light guide, previously shown for external beam therapy. In this study, the air core concept is modified and applied to the requirements of dosimetry in brachytherapy, proving its usability for measuring water energy doses in small radiation fields. Three air core detectors with different air core lengths are constructed and their performance in dosimetry for brachytherapy β-sources is compared with a standard two-fiber system, which uses a second fiber for Cerenkov correction. The detector systems are calibrated with a 90 Sr/ 90 Y secondary standard and tested for their angular dependence as well as their performance in depth dose measurements of 106 Ru/ 106 Rh sources. The signal loss relative to the standard detector increases with increasing air core length to a maximum value of 58.3%. At the same time, however, the percentage amount of Cerenkov light in the total signal is reduced from at least 12.1% to a value below 1.1%. There is a linear correlation between induced dose and measured signal current. The air core detectors determine the dose rates for 106 Ru/ 106 Rh sources without any form of correction for the Cerenkov signal. The air core detectors show advantages over the standard two-fiber system especially when measuring in radiation fields with high dose gradients. They can be used as simple one-fiber systems and allow for an almost Cerenkov-free scintillation dosimetry of brachytherapy β-sources. © 2017 American Association of Physicists in Medicine.

SU-E-J-274: Responses of Medulloblastoma Cells to Radiation Dosimetric Parameters in Intensity-Modulated Radiation Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, J; Molecular Imaging Program at Stanford, Stanford, CA; Bio-X Program, Stanford, CA

2015-06-15

Purpose: To evaluate radiation responses of the medulloblastoma cell line Daoy in intensity-modulated radiation therapy (IMRT), quantitative variations to variable radiation dosimetic parameters were tracked by bioluminescent images (BLIs). Methods: The luciferase and green fluorescent protein positive Daoy cells were cultured on dishes. The medulloblastoma cells irradiated to different dose rate, interval of fractionated doses, field margin and misalignment, and dose uniformity in IMRT were monitored using bioluminescent images. The cultured cells were placed into a dedicated acrylic phantom to deliver intensity-modulated fluences and calculate accurate predicted dose distribution. The radiation with dose rate from 0.5 Gy/min to 15 Gy/minmore » was irradiated by adjusting monitor unit per minute and source-to-surface distances. The intervals of fractionated dose delivery were changed considering the repair time of double strand breaks (DSB) revealed by straining of gamma-H2AX.The effect of non-uniform doses on the cells were visualized by registering dose distributions and BLIs. The viability according to dosimetric parameters was correlated with bioluminescent intensities for cross-check of radiation responses. Results: The DSB and cell responses due to the first fractionated dose delivery significantly affected final tumor control rather than other parameters. The missing tumor volumes due to the smaller field margin than the tumor periphery or field misalignment caused relapse of cell responses on BLIs. The dose rate and gradient had effect on initial responses but could not bring out the distinguishable killing effect on cancer cells. Conclusion: Visualized and quantified bioluminescent images were useful to correlate the dose distributions with spatial radiation effects on cells. This would derive the effective combination of dose delivery parameters and fractionation. Radiation responses in particular IMRT configuration could be reflected to image based-dose re-optimization.« less

Estimates of internal-dose equivalent from inhalation and ingestion of selected radionuclides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dunning, D.E.

1982-01-01

This report presents internal radiation dose conversion factors for radionuclides of interest in environmental assessments of nuclear fuel cycles. This volume provides an updated summary of estimates of committed dose equivalent for radionuclides considered in three previous Oak Ridge National Laboratory (ORNL) reports. Intakes by inhalation and ingestion are considered. The International Commission on Radiological Protection (ICRP) Task Group Lung Model has been used to simulate the deposition and retention of particulate matter in the respiratory tract. Results corresponding to activity median aerodynamic diameters (AMAD) of 0.3, 1.0, and 5.0 ..mu..m are given. The gastorintestinal (GI) tract has been representedmore » by a four-segment catenary model with exponential transfer of radioactivity from one segment to the next. Retention of radionuclides in systemic organs is characterized by linear combinations of decaying exponential functions, recommended in ICRP Publication 30. The first-year annual dose rate, maximum annual dose rate, and fifty-year dose commitment per microcurie intake of each radionuclide is given for selected target organs and the effective dose equivalent. These estimates include contributions from specified source organs plus the systemic activity residing in the rest of the body; cross irradiation due to penetrating radiations has been incorporated into these estimates. 15 references.« less

The Effects of Low Dose-Rate Ionizing Radiation on the Shapes of Transients in the LM124 Operational Amplifier

NASA Technical Reports Server (NTRS)

Buchner, Stephen; McMorrow, Dale; Roche, Nicholas; Dusseau, Laurent; Pease, Ron L.

2008-01-01

Shapes of single event transients (SETs) in a linear bipolar circuit (LM124) change with exposure to total ionizing dose (TID) radiation. SETs shape changes are a direct consequence of TID-induced degradation of bipolar transistor gain. A reduction in transistor gain causes a reduction in the drive current of the current sources in the circuit, and it is the lower drive current that most affects the shapes of large amplitude SETs.

The feasibility study and characterization of a two-dimensional diode array in "magic phantom" for high dose rate brachytherapy quality assurance.

PubMed

Espinoza, A; Beeksma, B; Petasecca, M; Fuduli, I; Porumb, C; Cutajar, D; Corde, S; Jackson, M; Lerch, M L F; Rosenfeld, A B

2013-11-01

High dose rate (HDR) brachytherapy is a radiation treatment technique capable of delivering large dose rates to the tumor. Radiation is delivered using remote afterloaders to drive highly active sources (commonly (192)Ir with an air KERMA strength range between 20,000 and 40,000 U, where 1 U = 1 μGy m(2)/h in air) through applicators directly into the patient's prescribed region of treatment. Due to the obvious ramifications of incorrect treatment while using such an active source, it is essential that there are methods for quality assurance (QA) that can directly and accurately verify the treatment plan and the functionality of the remote afterloader. This paper describes the feasibility study of a QA system for HDR brachytherapy using a phantom based two-dimensional 11 × 11 epitaxial diode array, named "magic phantom." The HDR brachytherapy treatment plan is translated to the phantom with two rows of 10 (20 in total) HDR source flexible catheters, arranged above and below the diode array "magic plate" (MP). Four-dimensional source tracking in each catheter is based upon a developed fast iterative algorithm, utilizing the response of the diodes in close proximity to the (192)Ir source, sampled at 100 ms intervals by a fast data acquisition (DAQ) system. Using a (192)Ir source in a solid water phantom, the angular response of the developed epitaxial diodes utilized in the MP and also the variation of the MP response as a function of the source-to-detector distance (SDD) were investigated. These response data are then used by an iterative algorithm for source dwelling position determination. A measurement of the average transit speed between dwell positions was performed using the diodes and a fast DAQ. The angular response of the epitaxial diode showed a variation of 15% within 360°, with two flat regions above and below the detector face with less than 5% variation. For SDD distances of between 5 and 30 mm the relative response of the epitaxial diodes used in the MP is in good agreement (within 8%) with radial dose function measurements found within the TG-43 protocol, with SDD of up to 70 mm showing a 40% over response. A method for four-dimensional localization of the HDR source was developed, allowing the source dwell position to be derived within 0.50 mm of the expected position. An estimation of the average transit speed for varying step sizes was determined and was found to increase from (12.8 ± 0.3) up to (38.6 ± 0.4) cm/s for a step size of 2.5 and 50 mm, respectively. Our characterization of the designed QA "magic phantom" with MP in realistic HDR photon fields demonstrates the promising performance for real-time source position tracking in four dimensions and measurements of transit times. Further development of this system will allow a full suite for QA in HDR brachytherapy and analysis, and for future in vivo tracking.

Radiation-induced hemopoietic death in mice as a function of photon energy and dose rate

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gengozian, N.; Taylor, T.; Jameson, H.

1986-03-01

Radiation-induced hemopoietic death was measured in mice exposed to photons of four different energies: 250-kVp X rays, /sup 60/Co gamma rays (1.25 MeV), and 6- and 25-MV photons from a linear accelerator. For each radiation source, the lethal dose which killed 50% of the population in 30 days (LD50/30) associated with the hemopoietic syndrome was determined in groups of mice exposed to graded doses from 600 to 1150 cGy at dose rates of 20, 40, and 80 cGy/min. The calculated LD50/30 values for 25 and 6 MV were significantly different from each other at all exposure rates while no differencemore » was observed between 6 MV and /sup 60/Co. Using /sup 60/Co gamma rays as the standard, the relative biologic effectiveness was as follows: 250 kVp greater than 25 MV greater than 6 MV = /sup 60/Co. The data suggest that there may be a greater damage to tissue within the marrow cavities following exposure to very high megavoltage radiation, a factor which must be considered with the increasing utilization of linear accelerators in the clinic and laboratory.« less

Stability analysis of a deterministic dose calculation for MRI-guided radiotherapy.

PubMed

Zelyak, O; Fallone, B G; St-Aubin, J

2017-12-14

Modern effort in radiotherapy to address the challenges of tumor localization and motion has led to the development of MRI guided radiotherapy technologies. Accurate dose calculations must properly account for the effects of the MRI magnetic fields. Previous work has investigated the accuracy of a deterministic linear Boltzmann transport equation (LBTE) solver that includes magnetic field, but not the stability of the iterative solution method. In this work, we perform a stability analysis of this deterministic algorithm including an investigation of the convergence rate dependencies on the magnetic field, material density, energy, and anisotropy expansion. The iterative convergence rate of the continuous and discretized LBTE including magnetic fields is determined by analyzing the spectral radius using Fourier analysis for the stationary source iteration (SI) scheme. The spectral radius is calculated when the magnetic field is included (1) as a part of the iteration source, and (2) inside the streaming-collision operator. The non-stationary Krylov subspace solver GMRES is also investigated as a potential method to accelerate the iterative convergence, and an angular parallel computing methodology is investigated as a method to enhance the efficiency of the calculation. SI is found to be unstable when the magnetic field is part of the iteration source, but unconditionally stable when the magnetic field is included in the streaming-collision operator. The discretized LBTE with magnetic fields using a space-angle upwind stabilized discontinuous finite element method (DFEM) was also found to be unconditionally stable, but the spectral radius rapidly reaches unity for very low-density media and increasing magnetic field strengths indicating arbitrarily slow convergence rates. However, GMRES is shown to significantly accelerate the DFEM convergence rate showing only a weak dependence on the magnetic field. In addition, the use of an angular parallel computing strategy is shown to potentially increase the efficiency of the dose calculation.

Stability analysis of a deterministic dose calculation for MRI-guided radiotherapy

NASA Astrophysics Data System (ADS)

Zelyak, O.; Fallone, B. G.; St-Aubin, J.

2018-01-01

Modern effort in radiotherapy to address the challenges of tumor localization and motion has led to the development of MRI guided radiotherapy technologies. Accurate dose calculations must properly account for the effects of the MRI magnetic fields. Previous work has investigated the accuracy of a deterministic linear Boltzmann transport equation (LBTE) solver that includes magnetic field, but not the stability of the iterative solution method. In this work, we perform a stability analysis of this deterministic algorithm including an investigation of the convergence rate dependencies on the magnetic field, material density, energy, and anisotropy expansion. The iterative convergence rate of the continuous and discretized LBTE including magnetic fields is determined by analyzing the spectral radius using Fourier analysis for the stationary source iteration (SI) scheme. The spectral radius is calculated when the magnetic field is included (1) as a part of the iteration source, and (2) inside the streaming-collision operator. The non-stationary Krylov subspace solver GMRES is also investigated as a potential method to accelerate the iterative convergence, and an angular parallel computing methodology is investigated as a method to enhance the efficiency of the calculation. SI is found to be unstable when the magnetic field is part of the iteration source, but unconditionally stable when the magnetic field is included in the streaming-collision operator. The discretized LBTE with magnetic fields using a space-angle upwind stabilized discontinuous finite element method (DFEM) was also found to be unconditionally stable, but the spectral radius rapidly reaches unity for very low-density media and increasing magnetic field strengths indicating arbitrarily slow convergence rates. However, GMRES is shown to significantly accelerate the DFEM convergence rate showing only a weak dependence on the magnetic field. In addition, the use of an angular parallel computing strategy is shown to potentially increase the efficiency of the dose calculation.

Corrigendum to "Stability analysis of a deterministic dose calculation for MRI-guided radiotherapy".

PubMed

Zelyak, Oleksandr; Fallone, B Gino; St-Aubin, Joel

2018-03-12

Modern effort in radiotherapy to address the challenges of tumor localization and motion has led to the development of MRI guided radiotherapy technologies. Accurate dose calculations must properly account for the effects of the MRI magnetic fields. Previous work has investigated the accuracy of a deterministic linear Boltzmann transport equation (LBTE) solver that includes magnetic field, but not the stability of the iterative solution method. In this work, we perform a stability analysis of this deterministic algorithm including an investigation of the convergence rate dependencies on the magnetic field, material density, energy, and anisotropy expansion. The iterative convergence rate of the continuous and discretized LBTE including magnetic fields is determined by analyzing the spectral radius using Fourier analysis for the stationary source iteration (SI) scheme. The spectral radius is calculated when the magnetic field is included (1) as a part of the iteration source, and (2) inside the streaming-collision operator. The non-stationary Krylov subspace solver GMRES is also investigated as a potential method to accelerate the iterative convergence, and an angular parallel computing methodology is investigated as a method to enhance the efficiency of the calculation. SI is found to be unstable when the magnetic field is part of the iteration source, but unconditionally stable when the magnetic field is included in the streaming-collision operator. The discretized LBTE with magnetic fields using a space-angle upwind stabilized discontinuous finite element method (DFEM) was also found to be unconditionally stable, but the spectral radius rapidly reaches unity for very low density media and increasing magnetic field strengths indicating arbitrarily slow convergence rates. However, GMRES is shown to significantly accelerate the DFEM convergence rate showing only a weak dependence on the magnetic field. In addition, the use of an angular parallel computing strategy is shown to potentially increase the efficiency of the dose calculation. © 2018 Institute of Physics and Engineering in Medicine.

SU-F-T-273: Using a Diode Array to Explore the Weakness of TPS DoseCalculation Algorithm for VMAT and Sliding Window Techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, J; Lu, B; Yan, G

Purpose: To identify the weakness of dose calculation algorithm in a treatment planning system for volumetric modulated arc therapy (VMAT) and sliding window (SW) techniques using a two-dimensional diode array. Methods: The VMAT quality assurance(QA) was implemented with a diode array using multiple partial arcs that divided from a VMAT plan; each partial arc has the same segments and the original monitor units. Arc angles were less than ± 30°. Multiple arcs delivered through consecutive and repetitive gantry operating clockwise and counterclockwise. The source-toaxis distance setup with the effective depths of 10 and 20 cm were used for a diodemore » array. To figure out dose errors caused in delivery of VMAT fields, the numerous fields having the same segments with the VMAT field irradiated using different delivery techniques of static and step-and-shoot. The dose distributions of the SW technique were evaluated by creating split fields having fine moving steps of multi-leaf collimator leaves. Calculated doses using the adaptive convolution algorithm were analyzed with measured ones with distance-to-agreement and dose difference of 3 mm and 3%.. Results: While the beam delivery through static and step-and-shoot techniques showed the passing rate of 97 ± 2%, partial arc delivery of the VMAT fields brought out passing rate of 85%. However, when leaf motion was restricted less than 4.6 mm/°, passing rate was improved up to 95 ± 2%. Similar passing rate were obtained for both 10 and 20 cm effective depth setup. The calculated doses using the SW technique showed the dose difference over 7% at the final arrival point of moving leaves. Conclusion: Error components in dynamic delivery of modulated beams were distinguished by using the suggested QA method. This partial arc method can be used for routine VMAT QA. Improved SW calculation algorithm is required to provide accurate estimated doses.« less

Neutron dose rate analysis on HTGR-10 reactor using Monte Carlo code

NASA Astrophysics Data System (ADS)

Suwoto; Adrial, H.; Hamzah, A.; Zuhair; Bakhri, S.; Sunaryo, G. R.

2018-02-01

The HTGR-10 reactor is cylinder-shaped core fuelled with kernel TRISO coated fuel particles in the spherical pebble with helium cooling system. The outlet helium gas coolant temperature outputted from the reactor core is designed to 700 °C. One advantage HTGR type reactor is capable of co-generation, as an addition to generating electricity, the reactor was designed to produce heat at high temperature can be used for other processes. The spherical fuel pebble contains 8335 TRISO UO2 kernel coated particles with enrichment of 10% and 17% are dispersed in a graphite matrix. The main purpose of this study was to analysis the distribution of neutron dose rates generated from HTGR-10 reactors. The calculation and analysis result of neutron dose rate in the HTGR-10 reactor core was performed using Monte Carlo MCNP5v1.6 code. The problems of double heterogeneity in kernel fuel coated particles TRISO and spherical fuel pebble in the HTGR-10 core are modelled well with MCNP5v1.6 code. The neutron flux to dose conversion factors taken from the International Commission on Radiological Protection (ICRP-74) was used to determine the dose rate that passes through the active core, reflectors, core barrel, reactor pressure vessel (RPV) and a biological shield. The calculated results of neutron dose rate with MCNP5v1.6 code using a conversion factor of ICRP-74 (2009) for radiation workers in the radial direction on the outside of the RPV (radial position = 220 cm from the center of the patio HTGR-10) provides the respective value of 9.22E-4 μSv/h and 9.58E-4 μSv/h for enrichment 10% and 17%, respectively. The calculated values of neutron dose rates are compliant with BAPETEN Chairman’s Regulation Number 4 Year 2013 on Radiation Protection and Safety in Nuclear Energy Utilization which sets the limit value for the average effective dose for radiation workers 20 mSv/year or 10μSv/h. Thus the protection and safety for radiation workers to be safe from the radiation source has been fulfilled. From the result analysis, it can be concluded that the model of calculation result of neutron dose rate for HTGR-10 core has met the required radiation safety standards.

Spatial Prediction of Coxiella burnetii Outbreak Exposure via Notified Case Counts in a Dose-Response Model.

PubMed

Brooke, Russell J; Kretzschmar, Mirjam E E; Hackert, Volker; Hoebe, Christian J P A; Teunis, Peter F M; Waller, Lance A

2017-01-01

We develop a novel approach to study an outbreak of Q fever in 2009 in the Netherlands by combining a human dose-response model with geostatistics prediction to relate probability of infection and associated probability of illness to an effective dose of Coxiella burnetii. The spatial distribution of the 220 notified cases in the at-risk population are translated into a smooth spatial field of dose. Based on these symptomatic cases, the dose-response model predicts a median of 611 asymptomatic infections (95% range: 410, 1,084) for the 220 reported symptomatic cases in the at-risk population; 2.78 (95% range: 1.86, 4.93) asymptomatic infections for each reported case. The low attack rates observed during the outbreak range from (Equation is included in full-text article.)to (Equation is included in full-text article.). The estimated peak levels of exposure extend to the north-east from the point source with an increasing proportion of asymptomatic infections further from the source. Our work combines established methodology from model-based geostatistics and dose-response modeling allowing for a novel approach to study outbreaks. Unobserved infections and the spatially varying effective dose can be predicted using the flexible framework without assuming any underlying spatial structure of the outbreak process. Such predictions are important for targeting interventions during an outbreak, estimating future disease burden, and determining acceptable risk levels.

Missing doses in the life span study of Japanese atomic bomb survivors.

PubMed

Richardson, David B; Wing, Steve; Cole, Stephen R

2013-03-15

The Life Span Study of atomic bomb survivors is an important source of risk estimates used to inform radiation protection and compensation. Interviews with survivors in the 1950s and 1960s provided information needed to estimate radiation doses for survivors proximal to ground zero. Because of a lack of interview or the complexity of shielding, doses are missing for 7,058 of the 68,119 proximal survivors. Recent analyses excluded people with missing doses, and despite the protracted collection of interview information necessary to estimate some survivors' doses, defined start of follow-up as October 1, 1950, for everyone. We describe the prevalence of missing doses and its association with mortality, distance from hypocenter, city, age, and sex. Missing doses were more common among Nagasaki residents than among Hiroshima residents (prevalence ratio = 2.05; 95% confidence interval: 1.96, 2.14), among people who were closer to ground zero than among those who were far from it, among people who were younger at enrollment than among those who were older, and among males than among females (prevalence ratio = 1.22; 95% confidence interval: 1.17, 1.28). Missing dose was associated with all-cancer and leukemia mortality, particularly during the first years of follow-up (all-cancer rate ratio = 2.16, 95% confidence interval: 1.51, 3.08; and leukemia rate ratio = 4.28, 95% confidence interval: 1.72, 10.67). Accounting for missing dose and late entry should reduce bias in estimated dose-mortality associations.

Missing Doses in the Life Span Study of Japanese Atomic Bomb Survivors

PubMed Central

Richardson, David B.; Wing, Steve; Cole, Stephen R.

2013-01-01

The Life Span Study of atomic bomb survivors is an important source of risk estimates used to inform radiation protection and compensation. Interviews with survivors in the 1950s and 1960s provided information needed to estimate radiation doses for survivors proximal to ground zero. Because of a lack of interview or the complexity of shielding, doses are missing for 7,058 of the 68,119 proximal survivors. Recent analyses excluded people with missing doses, and despite the protracted collection of interview information necessary to estimate some survivors' doses, defined start of follow-up as October 1, 1950, for everyone. We describe the prevalence of missing doses and its association with mortality, distance from hypocenter, city, age, and sex. Missing doses were more common among Nagasaki residents than among Hiroshima residents (prevalence ratio = 2.05; 95% confidence interval: 1.96, 2.14), among people who were closer to ground zero than among those who were far from it, among people who were younger at enrollment than among those who were older, and among males than among females (prevalence ratio = 1.22; 95% confidence interval: 1.17, 1.28). Missing dose was associated with all-cancer and leukemia mortality, particularly during the first years of follow-up (all-cancer rate ratio = 2.16, 95% confidence interval: 1.51, 3.08; and leukemia rate ratio = 4.28, 95% confidence interval: 1.72, 10.67). Accounting for missing dose and late entry should reduce bias in estimated dose-mortality associations. PMID:23429722

The estimation of absorbed dose rates for non-human biota : an extended inter-comparison.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Batlle, J. V. I.; Beaugelin-Seiller, K.; Beresford, N. A.

An exercise to compare 10 approaches for the calculation of unweighted whole-body absorbed dose rates was conducted for 74 radionuclides and five of the ICRP's Reference Animals and Plants, or RAPs (duck, frog, flatfish egg, rat and elongated earthworm), selected for this exercise to cover a range of body sizes, dimensions and exposure scenarios. Results were analysed using a non-parametric method requiring no specific hypotheses about the statistical distribution of data. The obtained unweighted absorbed dose rates for internal exposure compare well between the different approaches, with 70% of the results falling within a range of variation of {+-}20%. Themore » variation is greater for external exposure, although 90% of the estimates are within an order of magnitude of one another. There are some discernible patterns where specific models over- or under-predicted. These are explained based on the methodological differences including number of daughter products included in the calculation of dose rate for a parent nuclide; source-target geometry; databases for discrete energy and yield of radionuclides; rounding errors in integration algorithms; and intrinsic differences in calculation methods. For certain radionuclides, these factors combine to generate systematic variations between approaches. Overall, the technique chosen to interpret the data enabled methodological differences in dosimetry calculations to be quantified and compared, allowing the identification of common issues between different approaches and providing greater assurance on the fundamental dose conversion coefficient approaches used in available models for assessing radiological effects to biota.« less

Image Quality and Radiation Dose for Prospectively Triggered Coronary CT Angiography: 128-Slice Single-Source CT versus First-Generation 64-Slice Dual-Source CT

NASA Astrophysics Data System (ADS)

Gu, Jin; Shi, He-Shui; Han, Ping; Yu, Jie; Ma, Gui-Na; Wu, Sheng

2016-10-01

This study sought to compare the image quality and radiation dose of coronary computed tomography angiography (CCTA) from prospectively triggered 128-slice CT (128-MSCT) versus dual-source 64-slice CT (DSCT). The study was approved by the Medical Ethics Committee at Tongji Medical College of Huazhong University of Science and Technology. Eighty consecutive patients with stable heart rates lower than 70 bpm were enrolled. Forty patients were scanned with 128-MSCT, and the other 40 patients were scanned with DSCT. Two radiologists independently assessed the image quality in segments (diameter >1 mm) according to a three-point scale (1: excellent; 2: moderate; 3: insufficient). The CCTA radiation dose was calculated. Eighty patients with 526 segments in the 128-MSCT group and 544 segments in the DSCT group were evaluated. The image quality 1, 2 and 3 scores were 91.6%, 6.9% and 1.5%, respectively, for the 128-MSCT group and 97.6%, 1.7% and 0.7%, respectively, for the DSCT group, and there was a statistically significant inter-group difference (P ≤ 0.001). The effective doses were 3.0 mSv in the 128-MSCT group and 4.5 mSv in the DSCT group (P ≤ 0.001). Compared with DSCT, CCTA with prospectively triggered 128-MSCT had adequate image quality and a 33.3% lower radiation dose.

A GREEN'S FUNCTION APPROACH FOR DETERMINING DOSE RATES FOR SMALL GRAM QUANTITIES IN SHIPPING PACKAGINGS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nathan, S.

The Small Gram Quantity (SGQ) concept is based on the understanding that small amounts of hazardous materials, in this case radioactive materials (RAM), are significantly less hazardous than large amounts of the same materials. This paper describes a methodology designed to estimate an SGQ for several neutron and gamma emitting isotopes that can be shipped in a package in compliance with 10 CFR Part 71 external radiation level limits regulations. The neutron and photon sources were calculated using both ORIGEN-S and RASTA. The response from a unit source in each neutron and photon group was calculated using MCNP5 with eachmore » unshielded and shielded container configuration. Effects of self-shielding on both neutron and photon response were evaluated by including either plutonium oxide or iron in the source region for the case with no shielded container. For the cases of actinides mixed with light elements, beryllium is the bounding light element. The added beryllium (10 to 90 percent of the actinide mass) in the cases studied represents between 9 and 47 percent concentration of the total mixture mass. For beryllium concentrations larger than 50 percent, the increase in the neutron source term and dose rate tend to increase at a much lower rate than at concentrations lower than 50%. The intimately mixed actinide-beryllium form used in these models is very conservative and thus the limits presented in this report are practical bounds on the mass that can be safely shipped. The calculated dose rate from one gram of each isotope was then used to determin the maximum amount of a single isotope that could be shipped in the Model 9977 Package (or packagings having the same or larger external dimensions as well as similar structural materials) and have the external radiation level within the regulatory dose limits at the surface of the package. The estimates of the mass limits presented would also serve as conservative limits for both the Models 9975 and 9978 packages. If a package contains a mixture of isotopes, the acceptability for shipment can be determined by a sum of fractions approach. It should be noted that the SGQ masses presented in this report represent limits that would comply with the external radiation limits under 10CFR Part 71. They do not necessarily bound lower limits that may be required to comply with other factors such as heat load of the package.« less

Digital version of the European Atlas of natural radiation.

PubMed

Cinelli, Giorgia; Tollefsen, Tore; Bossew, Peter; Gruber, Valeria; Bogucarskis, Konstantins; De Felice, Luca; De Cort, Marc

2018-02-26

The European Atlas of Natural Radiation is a collection of maps displaying the levels of natural radioactivity caused by different sources. It has been developed and is being maintained by the Joint Research Centre (JRC) of the European Commission, in line with its mission, based on the Euratom Treaty: to collect, validate and report information on radioactivity levels in the environment of the EU Member States. This work describes the first version of the European Atlas of Natural Radiation, available in digital format through a web portal, as well as the methodology and results for the maps already developed. So far the digital Atlas contains: an annual cosmic-ray dose map; a map of indoor radon concentration; maps of uranium, thorium and potassium concentration in soil and in bedrock; a terrestrial gamma dose rate map; and a map of soil permeability. Through these maps, the public will be able to: familiarize itself with natural environmental radioactivity; be informed about the levels of natural radioactivity caused by different sources; have a more balanced view of the annual dose received by the European population, to which natural radioactivity is the largest contributor; and make direct comparisons between doses from natural sources of ionizing radiation and those from man-made (artificial) ones, hence, to better assess the latter. Work will continue on the European Geogenic Radon Map and on estimating the annual dose that the public may receive from natural radioactivity, by combining all the information from the different maps. More maps could be added to the Atlas, such us radon in outdoor air and in water and concentration of radionuclides in water, even if these sources usually contribute less to the total exposure. Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.

The evolution of brachytherapy for prostate cancer.

PubMed

Zaorsky, Nicholas G; Davis, Brian J; Nguyen, Paul L; Showalter, Timothy N; Hoskin, Peter J; Yoshioka, Yasuo; Morton, Gerard C; Horwitz, Eric M

2017-06-30

Brachytherapy (BT), using low-dose-rate (LDR) permanent seed implantation or high-dose-rate (HDR) temporary source implantation, is an acceptable treatment option for select patients with prostate cancer of any risk group. The benefits of HDR-BT over LDR-BT include the ability to use the same source for other cancers, lower operator dependence, and - typically - fewer acute irritative symptoms. By contrast, the benefits of LDR-BT include more favourable scheduling logistics, lower initial capital equipment costs, no need for a shielded room, completion in a single implant, and more robust data from clinical trials. Prospective reports comparing HDR-BT and LDR-BT to each other or to other treatment options (such as external beam radiotherapy (EBRT) or surgery) suggest similar outcomes. The 5-year freedom from biochemical failure rates for patients with low-risk, intermediate-risk, and high-risk disease are >85%, 69-97%, and 63-80%, respectively. Brachytherapy with EBRT (versus brachytherapy alone) is an appropriate approach in select patients with intermediate-risk and high-risk disease. The 10-year rates of overall survival, distant metastasis, and cancer-specific mortality are >85%, <10%, and <5%, respectively. Grade 3-4 toxicities associated with HDR-BT and LDR-BT are rare, at <4% in most series, and quality of life is improved in patients who receive brachytherapy compared with those who undergo surgery.

Determination of the intrinsic energy dependence of LiF:Mg,Ti thermoluminescent dosimeters for 125I and 103Pd brachytherapy sources relative to 60Co.

PubMed

Reed, J L; Rasmussen, B E; Davis, S D; Micka, J A; Culberson, W S; DeWerd, L A

2014-12-01

To determine the intrinsic energy dependence of LiF:Mg,Ti thermoluminescent dosimeters (TLD-100) for (125)I and (103)Pd brachytherapy sources relative to (60)Co. LiF:Mg,Ti TLDs were irradiated with low-energy brachytherapy sources and with a (60)Co teletherapy source. The brachytherapy sources measured were the Best 2301 (125)I seed, the OncoSeed 6711 (125)I seed, and the Best 2335 (103)Pd seed. The TLD light output per measured air-kerma strength was determined for the brachytherapy source irradiations, and the TLD light output per air kerma was determined for the (60)Co irradiations. Monte Carlo (MC) simulations were used to calculate the dose-to-TLD rate per air-kerma strength for the brachytherapy source irradiations and the dose to TLD per air kerma for the (60)Co irradiations. The measured and MC-calculated results for all irradiations were used to determine the TLD intrinsic energy dependence for (125)I and (103)Pd relative to (60)Co. The relative TLD intrinsic energy dependences (relative to (60)Co) and associated uncertainties (k = 1) were determined to be 0.883 ± 1.3%, 0.870 ± 1.4%, and 0.871 ± 1.5% for the Best 2301 seed, OncoSeed 6711 seed, and Best 2335 seed, respectively. The intrinsic energy dependence of TLD-100 is dependent on photon energy, exhibiting changes of 13%-15% for (125)I and (103)Pd sources relative to (60)Co. TLD measurements of absolute dose around (125)I and (103)Pd brachytherapy sources should explicitly account for the relative TLD intrinsic energy dependence in order to improve dosimetric accuracy.

Shielding NSLS-II light source: Importance of geometry for calculating radiation levels from beam losses

DOE PAGES

Kramer, S. L.; Ghosh, V. J.; Breitfeller, M.; ...

2016-08-10

We present that third generation high brightness light sources are designed to have low emittance and high current beams, which contribute to higher beam loss rates that will be compensated by Top-Off injection. Shielding for these higher loss rates will be critical to protect the projected higher occupancy factors for the users. Top-Off injection requires a full energy injector, which will demand greater consideration of the potential abnormal beam miss-steering and localized losses that could occur. The high energy electron injection beam produces significantly higher neutron component dose to the experimental floor than a lower energy beam injection and rampedmore » operations. Minimizing this dose will require adequate knowledge of where the miss-steered beam can occur and sufficient EM shielding close to the loss point, in order to attenuate the energy of the particles in the EM shower below the neutron production threshold (<10 MeV), which will spread the incident energy on the bulk shield walls and thereby the dose penetrating the shield walls. Designing supplemental shielding near the loss point using the analytic shielding model is shown to be inadequate because of its lack of geometry specification for the EM shower process. To predict the dose rates outside the tunnel requires detailed description of the geometry and materials that the beam losses will encounter inside the tunnel. Modern radiation shielding Monte-Carlo codes, like FLUKA, can handle this geometric description of the radiation transport process in sufficient detail, allowing accurate predictions of the dose rates expected and the ability to show weaknesses in the design before a high radiation incident occurs. The effort required to adequately define the accelerator geometry for these codes has been greatly reduced with the implementation of the graphical interface of FLAIR to FLUKA. In conclusion, this made the effective shielding process for NSLS-II quite accurate and reliable. The principles used to provide supplemental shielding to the NSLS-II accelerators and the lessons learned from this process are presented.« less

Rivaroxaban for Stroke Prevention after Embolic Stroke of Undetermined Source.

PubMed

Hart, Robert G; Sharma, Mukul; Mundl, Hardi; Kasner, Scott E; Bangdiwala, Shrikant I; Berkowitz, Scott D; Swaminathan, Balakumar; Lavados, Pablo; Wang, Yongjun; Wang, Yilong; Davalos, Antonio; Shamalov, Nikolay; Mikulik, Robert; Cunha, Luis; Lindgren, Arne; Arauz, Antonio; Lang, Wilfried; Czlonkowska, Anna; Eckstein, Jens; Gagliardi, Rubens J; Amarenco, Pierre; Ameriso, Sebastian F; Tatlisumak, Turgut; Veltkamp, Roland; Hankey, Graeme J; Toni, Danilo; Bereczki, Daniel; Uchiyama, Shinichiro; Ntaios, George; Yoon, Byung-Woo; Brouns, Raf; Endres, Matthias; Muir, Keith W; Bornstein, Natan; Ozturk, Serefnur; O'Donnell, Martin J; De Vries Basson, Matthys M; Pare, Guillaume; Pater, Calin; Kirsch, Bodo; Sheridan, Patrick; Peters, Gary; Weitz, Jeffrey I; Peacock, W Frank; Shoamanesh, Ashkan; Benavente, Oscar R; Joyner, Campbell; Themeles, Ellison; Connolly, Stuart J

2018-06-07

Embolic strokes of undetermined source represent 20% of ischemic strokes and are associated with a high rate of recurrence. Anticoagulant treatment with rivaroxaban, an oral factor Xa inhibitor, may result in a lower risk of recurrent stroke than aspirin. We compared the efficacy and safety of rivaroxaban (at a daily dose of 15 mg) with aspirin (at a daily dose of 100 mg) for the prevention of recurrent stroke in patients with recent ischemic stroke that was presumed to be from cerebral embolism but without arterial stenosis, lacune, or an identified cardioembolic source. The primary efficacy outcome was the first recurrence of ischemic or hemorrhagic stroke or systemic embolism in a time-to-event analysis; the primary safety outcome was the rate of major bleeding. A total of 7213 participants were enrolled at 459 sites; 3609 patients were randomly assigned to receive rivaroxaban and 3604 to receive aspirin. Patients had been followed for a median of 11 months when the trial was terminated early because of a lack of benefit with regard to stroke risk and because of bleeding associated with rivaroxaban. The primary efficacy outcome occurred in 172 patients in the rivaroxaban group (annualized rate, 5.1%) and in 160 in the aspirin group (annualized rate, 4.8%) (hazard ratio, 1.07; 95% confidence interval [CI], 0.87 to 1.33; P=0.52). Recurrent ischemic stroke occurred in 158 patients in the rivaroxaban group (annualized rate, 4.7%) and in 156 in the aspirin group (annualized rate, 4.7%). Major bleeding occurred in 62 patients in the rivaroxaban group (annualized rate, 1.8%) and in 23 in the aspirin group (annualized rate, 0.7%) (hazard ratio, 2.72; 95% CI, 1.68 to 4.39; P<0.001). Rivaroxaban was not superior to aspirin with regard to the prevention of recurrent stroke after an initial embolic stroke of undetermined source and was associated with a higher risk of bleeding. (Funded by Bayer and Janssen Research and Development; NAVIGATE ESUS ClinicalTrials.gov number, NCT02313909 .).

Measurement of nitrogen in the body using a commercial PGNAA system--phantom experiments.

PubMed

Chichester, D L; Empey, E

2004-01-01

An industrial prompt-gamma neutron activation analysis (PGNAA) system, originally designed for the real-time elemental analyses of bulk coal on a conveyor belt, has been studied to examine the feasibility of using such a system for body composition analysis. Experiments were conducted to measure nitrogen in a simple, tissue equivalent phantom comprised of 2.7 wt% of nitrogen. The neutron source for these experiments was 365 MBq (18.38 microg) of 252Cf located within an engineered low Z moderator and it yielded a dose rate in the measurement position of 3.91 mSv/h; data were collected using a 2780 cm(3) NaI(Tl) cylindrical detector with a digital signal processor and a 512 channel MCA. Source, moderator and detector geometries were unaltered from the system's standard configuration, where they have been optimized for considerations such as neutron thermalization, measurement sensitivity and uniformity, background radiation and external dose minimization. Based on net counts in the 10.8 MeV PGNAA nitrogen photopeak and its escape peaks the dose dependent nitrogen count rate was 11,600 counts/mSv with an uncertainty of 3.0% after 0.32 mSv (4.9 min), 2.0% after 0.74 mSv (11.4 min) and 1.0% after 3.02 mSv (46.4 min).

Dose profile modeling of Idaho National Laboratory's active neutron interrogation laboratory.

PubMed

Chichester, D L; Seabury, E H; Zabriskie, J M; Wharton, J; Caffrey, A J

2009-06-01

A new laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for deuterium-tritium (DT) fusion (14.1 MeV) neutron generators (2 x 10(8) n/s), deuterium-deuterium (DD) fusion (2.5 MeV) neutron generators (1 x 10(7) n/s), and (252)Cf spontaneous fission neutron sources (6.96 x 10(7) n/s, 30 microg). Shielding at the laboratory is comprised of modular concrete shield blocks 0.76 m thick with tongue-in-groove features to prevent radiation streaming, arranged into one small and one large test vault. The larger vault is designed to allow operation of the DT generator and has walls 3.8m tall, an entrance maze, and a fully integrated electrical interlock system; the smaller test vault is designed for (252)Cf and DD neutron sources and has walls 1.9 m tall and a simple entrance maze. Both analytical calculations and numerical simulations were used in the design process for the building to assess the performance of the shielding walls and to ensure external dose rates are within required facility limits. Dose rate contour plots have been generated for the facility to visualize the effectiveness of the shield walls and entrance mazes and to illustrate the spatial profile of the radiation dose field above the facility and the effects of skyshine around the vaults.

DOSE PROFILE MODELING OF IDAHO NATIONAL LABORATORY’S ACTIVE NEUTRON INTERROGATION TEST FACILITY

DOE Office of Scientific and Technical Information (OSTI.GOV)

D. L. Chichester; E. H. Seabury; J. M. Zabriskie

2009-06-01

A new research and development laboratory has been commissioned at Idaho National Laboratory for performing active neutron interrogation research and development. The facility is designed to provide radiation shielding for DT fusion (14.1 MeV) neutron generators (2 x 108 neutrons per second), DD fusion (2.5 MeV) neutron generators (up to 2 x 106 neutrons per second), and 252Cf spontaneous fission neutron sources (6.7 x 107 neutrons per second, 30 micrograms). Shielding at the laboratory is comprised of modular concrete shield blocks 0.76 m thick with tongue-in-groove features to prevent radiation streaming, arranged into one small and one large test vault.more » The larger vault is designed to allow operation of the DT generator and has walls 3.8 m tall, an entrance maze, and a fully integrated electrical interlock system; the smaller test vault is designed for 252Cf and DD neutron sources and has walls 1.9 m tall and a simple entrance maze. Both analytical calculations and numerical simulations were used in the design process for the building to assess the performance of the shielding walls and to ensure external dose rates are within required facility limits. Dose rate contour plots have been generated for the facility to visualize the effectiveness of the shield wall and entrance maze and to illustrate the spatial profile of the radiation dose field above the facility and the effects of skyshine around the vaults.« less

epsilon-N-trimethyllysine availability regulates the rate of carnitine biosynthesis in the growing rat

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rebouche, C.J.; Lehman, L.J.; Olson, L.

1986-05-01

Rates of carnitine biosynthesis in mammals depend on the availability of substrates and the activity of enzymes subserving the pathway. This study was undertaken to test the hypothesis that the availability of epsilon-N-trimethyllysine is rate-limiting for synthesis of carnitine in the growing rat and to evaluate diet as a source of this precursor for carnitine biosynthesis. Rats apparently absorbed greater than 90% of a tracer dose of (methyl-/sup 3/H)epsilon-N-trimethyllysine, and approximately 30% of that was incorporated into tissues as (/sup 3/H)carnitine. Rats given oral supplements of epsilon-N-trimethyllysine (0.5-20 mg/d), but no dietary carnitine, excreted more carnitine than control animals receivingmore » no dietary epsilon-N-trimethyllysine or carnitine. Rates of carnitine excretion increased in a dose-dependent manner. Tissue and serum levels of carnitine also increased with dietary epsilon-N-trimethyllysine supplementation. There was no evidence that the capacity for carnitine biosynthesis was saturated even at the highest level of oral epsilon-N-trimethyllysine supplementation. Common dietary proteins (casein, soy protein and wheat gluten) were found to be poor sources of epsilon-N-trimethyllysine for carnitine biosynthesis. The results of this study indicate that the availability of epsilon-N-trimethyllysine limits the rate of carnitine biosynthesis in the growing rat.« less

Keeping an eye on the ring: COMS plaque loading optimization for improved dose conformity and homogeneity.

PubMed

Gagne, Nolan L; Cutright, Daniel R; Rivard, Mark J

2012-09-01

To improve tumor dose conformity and homogeneity for COMS plaque brachytherapy by investigating the dosimetric effects of varying component source ring radionuclides and source strengths. The MCNP5 Monte Carlo (MC) radiation transport code was used to simulate plaque heterogeneity-corrected dose distributions for individually-activated source rings of 14, 16 and 18 mm diameter COMS plaques, populated with (103)Pd, (125)I and (131)Cs sources. Ellipsoidal tumors were contoured for each plaque size and MATLAB programming was developed to generate tumor dose distributions for all possible ring weighting and radionuclide permutations for a given plaque size and source strength resolution, assuming a 75 Gy apical prescription dose. These dose distributions were analyzed for conformity and homogeneity and compared to reference dose distributions from uniformly-loaded (125)I plaques. The most conformal and homogeneous dose distributions were reproduced within a reference eye environment to assess organ-at-risk (OAR) doses in the Pinnacle(3) treatment planning system (TPS). The gamma-index analysis method was used to quantitatively compare MC and TPS-generated dose distributions. Concentrating > 97% of the total source strength in a single or pair of central (103)Pd seeds produced the most conformal dose distributions, with tumor basal doses a factor of 2-3 higher and OAR doses a factor of 2-3 lower than those of corresponding uniformly-loaded (125)I plaques. Concentrating 82-86% of the total source strength in peripherally-loaded (131)Cs seeds produced the most homogeneous dose distributions, with tumor basal doses 17-25% lower and OAR doses typically 20% higher than those of corresponding uniformly-loaded (125)I plaques. Gamma-index analysis found > 99% agreement between MC and TPS dose distributions. A method was developed to select intra-plaque ring radionuclide compositions and source strengths to deliver more conformal and homogeneous tumor dose distributions than uniformly-loaded (125)I plaques. This method may support coordinated investigations of an appropriate clinical target for eye plaque brachytherapy.

Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit

NASA Astrophysics Data System (ADS)

El-Jaby, Samy; Richardson, Richard B.

2015-07-01

Occupational exposures from ionizing radiation are currently regulated for airline travel (<20 km) and for missions to low-Earth orbit (∼300-400 km). Aircrew typically receive between 1 and 6 mSv of occupational dose annually, while aboard the International Space Station, the area radiation dose equivalent measured over just 168 days was 106 mSv at solar minimum conditions. It is anticipated that space tourism vehicles will reach suborbital altitudes of approximately 100 km and, therefore, the annual occupational dose to flight crew during repeated transits is expected to fall somewhere between those observed for aircrew and astronauts. Unfortunately, measurements of the radiation environment at the high altitudes reached by suborbital vehicles are sparse, and modelling efforts have been similarly limited. In this paper, preliminary MCNPX radiation transport code simulations are developed of the secondary neutron flux profile in air from surface altitudes up to low Earth orbit at solar minimum conditions and excluding the effects of spacecraft shielding. These secondary neutrons are produced by galactic cosmic radiation interacting with Earth's atmosphere and are among the sources of radiation that can pose a health risk. Associated estimates of the operational neutron ambient dose equivalent, used for radiation protection purposes, and the neutron effective dose equivalent that is typically used for estimates of stochastic health risks, are provided in air. Simulations show that the neutron radiation dose rates received at suborbital altitudes are comparable to those experienced by aircrew flying at 7 to 14 km. We also show that the total neutron dose rate tails off beyond the Pfotzer maximum on ascension from surface up to low Earth orbit.

Monte Carlo simulations of the secondary neutron ambient and effective dose equivalent rates from surface to suborbital altitudes and low Earth orbit.

PubMed

El-Jaby, Samy; Richardson, Richard B

2015-07-01

Occupational exposures from ionizing radiation are currently regulated for airline travel (<20 km) and for missions to low-Earth orbit (∼300-400 km). Aircrew typically receive between 1 and 6 mSv of occupational dose annually, while aboard the International Space Station, the area radiation dose equivalent measured over just 168 days was 106 mSv at solar minimum conditions. It is anticipated that space tourism vehicles will reach suborbital altitudes of approximately 100 km and, therefore, the annual occupational dose to flight crew during repeated transits is expected to fall somewhere between those observed for aircrew and astronauts. Unfortunately, measurements of the radiation environment at the high altitudes reached by suborbital vehicles are sparse, and modelling efforts have been similarly limited. In this paper, preliminary MCNPX radiation transport code simulations are developed of the secondary neutron flux profile in air from surface altitudes up to low Earth orbit at solar minimum conditions and excluding the effects of spacecraft shielding. These secondary neutrons are produced by galactic cosmic radiation interacting with Earth's atmosphere and are among the sources of radiation that can pose a health risk. Associated estimates of the operational neutron ambient dose equivalent, used for radiation protection purposes, and the neutron effective dose equivalent that is typically used for estimates of stochastic health risks, are provided in air. Simulations show that the neutron radiation dose rates received at suborbital altitudes are comparable to those experienced by aircrew flying at 7 to 14 km. We also show that the total neutron dose rate tails off beyond the Pfotzer maximum on ascension from surface up to low Earth orbit. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

Satiety effects of a whole-grain fibre composite ingredient: reduced food intake and appetite ratings.

PubMed

Harrold, Joanne; Breslin, Leanne; Walsh, Jennifer; Halford, Jason; Pelkman, Christine

2014-10-01

The current study assesses the impact on appetite and food intake of a novel co-processed ingredient containing a viscous fibre and whole-grain high-amylose corn flour, a source of type 1 and type 2 resistant starch (HAM-RS). Ninety adults completed a crossover, placebo-controlled study comparing two doses of the ingredient (20 and 30 g) to a maltodextrin control in a fruit-based smoothie served with breakfast. Ad libitum food intake was measured over the day and visual analogue scales were used to assess subjective appetite sensations. Subjects consumed 7% less energy intake at dinner following the 30 g dose (p = 0.02) compared to control. In addition, a trend for lower lunch intake (5% less weight of food) was observed for the 20 g dose (p = 0.10). Reductions were also observed for the two meals combined, with 3% lower energy intake for the 20 g dose (p = 0.04) and 5% less weight of food consumed for the 30 g dose (p = 0.04). Lower ratings of hunger were reported at 3 h after breakfast for both doses and also at 2 and 3 h after lunch for the 30 g dose. With ratings combined to compute an overall appetite score, a trend for lower appetite scores at 3 h after breakfast was found for both doses. Consistent with this, significant reductions in AUC hunger and prospective consumption were identified in the 30 g condition. A similar pattern of results was observed for fullness and desire to eat. The results of this study show that a new composite satiety ingredient comprised of a viscous fibre and whole-grain corn flour can affect acute satiety responses in men and women.

Indoor terrestrial gamma dose rate mapping in France: a case study using two different geostatistical models.

PubMed

Warnery, E; Ielsch, G; Lajaunie, C; Cale, E; Wackernagel, H; Debayle, C; Guillevic, J

2015-01-01

Terrestrial gamma dose rates show important spatial variations in France. Previous studies resulted in maps of arithmetic means of indoor terrestrial gamma dose rates by "departement" (French district). However, numerous areas could not be characterized due to the lack of data. The aim of our work was to obtain more precise estimates of the spatial variability of indoor terrestrial gamma dose rates in France by using a more recent and complete data base and geostatistics. The study was based on the exploitation of 97,595 measurements results distributed in 17,404 locations covering all of France. Measurements were done by the Institute for Radioprotection and Nuclear Safety (IRSN) using RPL (Radio Photo Luminescent) dosimeters, exposed during several months between years 2011 and 2012 in French dentist surgeries and veterinary clinics. The data used came from dosimeters which were not exposed to anthropic sources. After removing the cosmic rays contribution in order to study only the telluric gamma radiation, it was decided to work with the arithmetic means of the time-series measurements, weighted by the time-exposure of the dosimeters, for each location. The values varied between 13 and 349 nSv/h, with an arithmetic mean of 76 nSv/h. The observed statistical distribution of the gamma dose rates was skewed to the right. Firstly, ordinary kriging was performed in order to predict the gamma dose rate on cells of 1*1 km(2), all over the domain. The second step of the study was to use an auxiliary variable in estimates. The IRSN achieved in 2010 a classification of the French geological formations, characterizing their uranium potential on the bases of geology and local measurement results of rocks uranium content. This information is georeferenced in a map at the scale 1:1,000,000. The geological uranium potential (GUP) was classified in 5 qualitative categories. As telluric gamma rays mostly come from the progenies of the (238)Uranium series present in rocks, this information, which is exhaustive throughout France, could help in estimating the telluric gamma dose rates. Such an approach is possible using multivariate geostatistics and cokriging. Multi-collocated cokriging has been performed on 1*1 km(2) cells over the domain. This model used gamma dose rate measurement results and GUP classes. Our results provide useful information on the variability of the natural terrestrial gamma radiation in France ('natural background') and exposure data for epidemiological studies and risk assessment from low dose chronic exposures. Copyright © 2014 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, P.H.; Krishnamurthy, G.T.; Bobba, V.R.

The radiation absorbed doses from five commercially available hepatobiliary agents-Tc-99m-tagged analogs of IDA (EIDA, PIPIDA, HIDA, PBIDA, DISIDA*) have been calculated from biokinetic data in 41 normal subjects. Serial gamma images, with blood and urine samples, were obtained to calculate cumulated radioactivity in the source organs: blood, kidey, bladder, liver, gallbladder, and intestines. The critical organ was the gallbladder, with an absorbed-dose range of 690 to 780 mrad/mCi. Absorbed doses for other target organs were: upper large intestine 320 to 370 mrad/mCi, lower large intestine 210 to 240, small intestine 170 to 200, liver 65 (DISIDA) to 130 (PBIDA), ovariesmore » 63 to 72, and urinary bladder wall 23 (PBIDA) to 36 (EIDA). The radiation absorbed dose was largely independent of changes in chemical structure except in (a) the liver, where absorbed dose varied by a factor of two in proportion to the rate of excretion of the IDA agent from the liver, and (b) the urinary bladder, where absorbed dose varied by a factor of 1.6 because of differences in rate of excretion. When the stimulus for gallbladder emptying is changed from whole-meal ingestion to cholecystokinin injection, the absorbed dose to the gallbladder increases to approx. 1 rad/mCi; if no gallbladder emptying is assumed, its absorbed dose increases to approx. 1.9 rad/mCi. In the absence of contraindication, the gallbladder absorbed dose may thus be decreased by inducing gallbladder emptying at the end of the imaging study.« less

Proton flux and radiation dose from galactic cosmic rays in the lunar regolith and implications for organic synthesis at the poles of the Moon and Mercury

NASA Astrophysics Data System (ADS)

Crites, S. T.; Lucey, P. G.; Lawrence, D. J.

2013-11-01

Galactic cosmic rays are a potential energy source to stimulate organic synthesis from simple ices. The recent detection of organic molecules at the polar regions of the Moon by LCROSS (Colaprete, A. et al. [2010]. Science 330, 463-468, http://dx.doi.org/10.1126/science.1186986), and possibly at the poles of Mercury (Paige, D.A. et al. [2013]. Science 339, 300-303, http://dx.doi.org/10.1126/science.1231106), introduces the question of whether the organics were delivered by impact or formed in situ. Laboratory experiments show that high energy particles can cause organic production from simple ices. We use a Monte Carlo particle scattering code (MCNPX) to model and report the flux of GCR protons at the surface of the Moon and report radiation dose rates and absorbed doses at the Moon’s surface and with depth as a result of GCR protons and secondary particles, and apply scaling factors to account for contributions to dose from heavier ions. We compare our results with dose rate measurements by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) experiment on Lunar Reconnaissance Orbiter (Schwadron, N.A. et al. [2012]. J. Geophys. Res. 117, E00H13, http://dx.doi.org/10.1029/2011JE003978) and find them in good agreement, indicating that MCNPX can be confidently applied to studies of radiation dose at and within the surface of the Moon. We use our dose rate calculations to conclude that organic synthesis is plausible well within the age of the lunar polar cold traps, and that organics detected at the poles of the Moon may have been produced in situ. Our dose rate calculations also indicate that galactic cosmic rays can induce organic synthesis within the estimated age of the dark deposits at the pole of Mercury that may contain organics.

Recent international regulations: low dose-low rate radiation protection and the demise of reason.

PubMed

Okkalides, Demetrios

2008-01-01

The radiation protection measures suggested by the International Committee for Radiation Protection (ICRP), national regulating bodies and experts, have been becoming ever more strict despite the decrease of any information supporting the existence of the Linear no Threshold model (LNT) and of any adverse effects of Low Dose Low Rate (LDLR) irradiation. This tendency arises from the disproportionate response of human society to hazards that are currently in fashion and is unreasonable. The 1 mSv/year dose limit for the public suggested by the ICRP corresponds to a 1/18,181 detriment-adjusted cancer risk and is much lower than other hazards that are faced by modern societies such as e.g. driving and smoking which carry corresponding rate risks of 1/2,100 and 1/2,000. Even worldwide deadly work accidents rate is higher at 1/ 8,065. Such excessive safety measures against minimal risks from man made radiation sources divert resources from very real and much greater hazards. In addition they undermine research and development of radiation technology and tend to subjugate science and the quest for understanding nature to phobic practices.

[Intracoronary brachytherapy with strontium/yttrium-90. Initial experiences in Germany].

PubMed

Silber, S; von Rottkay, P; Gielow, A; Schneider, A; Bauer, A; Schöfer, H

1998-09-01

Restenosis after PTCA is still an unresolved problem and occurs in approximately 30% of our patients despite a stent implantation rate of up to 63%. Intracoronary brachytherapy has the potential to counteract the proliferative component of restenosis as well as to prevent shrinking of the coronary artery. Two years ago, we applied for the license to use the Novoste Beta-Cath system. This is the first report of its use in Germany. Attaining the license was complicated by the facts that this device did not yet have CE-certification (MPG section 17), that brachytherapy is not yet an approved method of treatment (StrSchV section 41), the report of the BfS and the approval by an accredited ethical committee. The application becomes even more complicated by the amount demanded by the LfU for insurance: 1 Million DM for each individual patient (AtDeckV section 15). The final local inspection needs to be performed by an expert from the LfAS (StrSchV section 76). Strontium-90 decays into Yttrium-90 with a half-life time of approximately 28 years. Yttrium-90, too, is a pure beta-emitter with a shorter half-life time of approximately 64 hours and a considerably higher electron energy of maximum 2.27 MeV. Yttrium-90 is the therapeutic agent. The radiation source of the Beta-Cath system consists of 12 single, separate cylinders (pellets, seeds) with a total length of 3 cm. The activity of the total train is approximately 1.3 to 1.5 GBq (35 to 40 mCi). For verification of the dose rate provided by the manufacturer, we performed a check using the GafChromic film. The test dose (exactly 2 mm from the center of the long axis of the activity train) was 150 Gy. We obtained the following results for the optical density: reference source: 0.29 +/- 0.01, source C: 0.318 +/- 0.013 and source D: 0.317 +/- 0.028. For a dose rate of e.g. 0.083 Gy/s, the radiation times are 169 s for a dose of 14 Gy (vessel diameter 2.7 to 3.35 mm) or 217 s for 18 Gy (vessel diameter 3.36 to 4.0 mm), respectively. In our cath lab, the following dose rates were measured: at the lead container: 20 microSv/h, surface of the transfer device: 400 microSv/h, surface of the phantom: 20 microSv/h and surface of the bail out box: 100 microSv/h. Because moving the source train to the tip of the catheter takes only approximately 1 s, the exposure to other tissues or organs is negligible. However, inappropriate handling of the device could cause significant radiation of other organs. Therefore, the importance of intensive training cannot be overemphasized. The results of the currently ongoing multicenter trials (Beta-Cath system trial in the USA and the BRIE trial in Europe) are being anxiously awaited and will have a decisive impact on the medical acceptance of intracoronary radiation for prophylaxis and/or therapy of restenosis.

Action research regarding the optimisation of radiological protection for nurses during vascular interventional radiology.

PubMed

Mori, Hiroshige

2015-06-01

The optimisation and decision-making processes for radiological protection have been broadened by the introduction of re-examination or feedback after introducing protective measures. In this study, action research was used to reduce the occupational exposure of vascular interventional radiology (IR) nurses. Four radiological protection improvement measures were continuously performed in cooperation with the researchers, nurses and stakeholders, and the nurses' annual effective doses were compared before and after the improvements. First, the dosimetry equipment was changed from one electronic personal dosimeter (EPD) to two silver-activated phosphate glass dosimeters (PGDs). Second, the nurses were educated regarding maintaining a safe distance from the sources of scattered and leakage radiation. Third, portable radiation shielding screens were placed in the IR rooms. Fourth, the x-ray units' pulse rates were reduced by half. On changing the dosimetry method, the two PGDs recorded a 4.4 fold greater dose than the single EPD. Educating nurses regarding radiological protection and reducing the pulse rates by half decreased their effective doses to one-third and two-fifths of the baseline dose, respectively. No significant difference in their doses was detected after the placement of the shielding screens. Therefore, the action research effectively decreased the occupational doses of the vascular IR nurses.

Organ shielding and doses in Low-Earth orbit calculated for spherical and anthropomorphic phantoms

NASA Astrophysics Data System (ADS)

Matthiä, Daniel; Berger, Thomas; Reitz, Günther

2013-08-01

Humans in space are exposed to elevated levels of radiation compared to ground. Different sources contribute to the total exposure with galactic cosmic rays being the most important component. The application of numerical and anthropomorphic phantoms in simulations allows the estimation of dose rates from galactic cosmic rays in individual organs and whole body quantities such as the effective dose. The male and female reference phantoms defined by the International Commission on Radiological Protection and the hermaphrodite numerical RANDO phantom are voxel implementations of anthropomorphic phantoms and contain all organs relevant for radiation risk assessment. These anthropomorphic phantoms together with a spherical water phantom were used in this work to translate the mean shielding of organs in the different anthropomorphic voxel phantoms into positions in the spherical phantom. This relation allows using a water sphere as surrogate for the anthropomorphic phantoms in both simulations and measurements. Moreover, using spherical phantoms in the calculation of radiation exposure offers great advantages over anthropomorphic phantoms in terms of computational time. In this work, the mean shielding of organs in the different voxel phantoms exposed to isotropic irradiation is presented as well as the corresponding depth in a water sphere. Dose rates for Low-Earth orbit from galactic cosmic rays during solar minimum conditions were calculated using the different phantoms and are compared to the results for a spherical water phantom in combination with the mean organ shielding. For the spherical water phantom the impact of different aluminium shielding between 1 g/cm2 and 100 g/cm2 was calculated. The dose equivalent rates were used to estimate the effective dose rate.

An open source solution for an in-house built dynamic platform for the validation of stereotactic ablative body radiotherapy for VMAT and IMRT.

PubMed

Munoz, Luis; Ziebell, Amy; Morton, Jason; Bhat, Madhava

2016-12-01

An in-house solution for the verification of dose delivered to a moving phantom as required for the clinical implementation of lung stereotactic ablative body radiation therapy was developed. The superior-inferior movement required to simulate tumour motion during a normal breathing cycle was achieved via the novel use of an Arduino Uno™, a low-cost open-source microcontroller board connected to a high torque servo motor. Slow CT imaging was used to acquire the image set and a 4D cone beam CT (4D-CBCT) verified the efficacy of contoured margins before treatment on the moving phantom. Treatment fields were delivered to a section of a CIRS™ anthropomorphic phantom. Dose verification to the dynamic phantom with Gafchromic EBT3 film using 3 %-1 mm gamma analysis acceptance criteria registered an absolute dose pass rate for IMRT and VMAT of 98 and 96.6 %, respectively. It was verified that 100 % of the PTV received the prescribed dose of 12 Gy per fraction using the dynamic phantom, and no major discrepancy between planned and measured results due to interplay between multileaf collimator sequences and target motion was observed. This study confirmed that the use of an in-house solution using open source hardware and software with existing quality assurance equipment was appropriate in validating a new treatment technique.

Dosimetric effects of Onyx embolization on Gamma Knife arteriovenous malformation dose distributions.

PubMed

Schlesinger, David J; Nordström, Håkan; Lundin, Anders; Xu, Zhiyuan; Sheehan, Jason P

2016-12-01

OBJECTIVE Patients with arteriovenous malformations (AVMs) treated with Gamma Knife radiosurgery (GKRS) subsequent to embolization suffer from elevated local failure rates and differences in adverse radiation effects. Onyx is a common embolic material for AVMs. Onyx is formulated with tantalum, a high atomic number (Z = 73) element that has been investigated as a source of dosimetric uncertainty contributing to the less favorable clinical results. However, prior studies have not modeled the complicated anatomical and beam geometries characteristic of GKRS. This study investigated the magnitude of dose perturbation that can occur due to Onyx embolization using clinically realistic anatomical and Gamma Knife beam models. METHODS Leksell GammaPlan (LGP) was used to segment the AVM nidus and areas of Onyx from postcontrast stereotactic MRI for 7 patients treated with GKRS postembolization. The resulting contours, skull surface, and clinically selected dose distributions were exported from LGP in DICOM-RT (Digital Imaging and Communications in Medicine-radiotherapy) format. Isocenter locations and dwell times were recorded from the LGP database. Contours were converted into 3D mesh representations using commercial and in-house mesh-editing software. The resulting data were imported into a Monte Carlo (MC) dose calculation engine (Pegasos, Elekta Instruments AB) with a beam geometry for the Gamma Knife Perfexion. The MC-predicted dose distributions were calculated with Onyx assigned manufacturer-reported physical constants (MC-Onyx), and then compared with corresponding distributions in which Onyx was reassigned constants for water (MC-water). Differences in dose metrics were determined, including minimum, maximum, and mean dose to the AVM nidus; selectivity index; and target coverage. Combined differences in dose magnitude and distance to agreement were calculated as 3D Gamma analysis passing rates using tolerance criteria of 0.5%/0.5 mm, 1.0%/1.0 mm, and 3.0%/3.0 mm. RESULTS Overall, the mean percentage differences in dose metrics for MC-Onyx relative to MC-water were as follows; all data are reported as mean (SD): minimum dose to AVM = -0.7% (1.4%), mean dose to AVM = 0.1% (0.2%), maximum dose to AVM = 2.9% (5.0%), selectivity = 0.1% (0.2%), and coverage = -0.0% (0.2%). The mean percentage of voxels passing at each Gamma tolerance were as follows: 99.7% (0.1%) for 3.0%/3.0 mm, 98.2% (0.7%) for 1.0%/1.0 mm, and 52.1% (4.4%) for 0.5%/0.5 mm. CONCLUSIONS Onyx embolization appears to have a detectable effect on the delivered dose distribution. However, the small changes in dose metrics and high Gamma passing rates at 1.0%/1.0 mm tolerance suggest that these changes are unlikely to be clinically significant. Additional sources of delivery and biological uncertainty should be investigated to determine the root cause of the observed less favorable postembolization GKRS outcomes.

SU-E-T-467: Implementation of Monte Carlo Dose Calculation for a Multileaf Collimator Equipped Robotic Radiotherapy System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, JS; Fan, J; Ma, C-M

Purpose: To improve the treatment efficiency and capabilities for full-body treatment, a robotic radiosurgery system has equipped with a multileaf collimator (MLC) to extend its accuracy and precision to radiation therapy. To model the MLC and include it in the Monte Carlo patient dose calculation is the goal of this work. Methods: The radiation source and the MLC were carefully modeled to consider the effects of the source size, collimator scattering, leaf transmission and leaf end shape. A source model was built based on the output factors, percentage depth dose curves and lateral dose profiles measured in a water phantom.more » MLC leaf shape, leaf end design and leaf tilt for minimizing the interleaf leakage and their effects on beam fluence and energy spectrum were all considered in the calculation. Transmission/leakage was added to the fluence based on the transmission factors of the leaf and the leaf end. The transmitted photon energy was tuned to consider the beam hardening effects. The calculated results with the Monte Carlo implementation was compared with measurements in homogeneous water phantom and inhomogeneous phantoms with slab lung or bone material for 4 square fields and 9 irregularly shaped fields. Results: The calculated output factors are compared with the measured ones and the difference is within 1% for different field sizes. The calculated dose distributions in the phantoms show good agreement with measurements using diode detector and films. The dose difference is within 2% inside the field and the distance to agreement is within 2mm in the penumbra region. The gamma passing rate is more than 95% with 2%/2mm criteria for all the test cases. Conclusion: Implementation of Monte Carlo dose calculation for a MLC equipped robotic radiosurgery system is completed successfully. The accuracy of Monte Carlo dose calculation with MLC is clinically acceptable. This work was supported by Accuray Inc.« less

Dosimetric evaluation of a new OneDose MOSFET for Ir-192 energy.

PubMed

Kinhikar, Rajesh A; Sharma, Pramod K; Tambe, Chandrashekhar M; Deshpande, Deepak D

2006-03-07

The purpose of this study was to investigate dosimetry (reproducibility, energy correction, relative response with distance from source, linearity with threshold dose, rate of fading, temperature and angular dependence) of a newly designed OneDosetrade mark MOSFET patient dosimetry system for use in HDR brachytherapy with Ir-192 energy. All measurements were performed with a MicroSelectron HDR unit and OneDose MOSFET detectors. All dosimeters were normalized to 3 min post-irradiation to minimize fading effects. All dosimeters gave reproducible readings with mean deviation of 1.8% (SD 0.4) and 2.4% (SD 0.6) for 0 degrees and 180 degrees incidences, respectively. The mean energy correction factor was found to be 1.1 (range 1.06-1.12). Overall, there was 60% and 40% mean response of the MOSFET at 2 and 3 cm, respectively, from the source. MOSFET results showed good agreement with TLD and parallel plate ion chamber. Linear dose response with threshold voltage shift was observed with applied doses of 0.3 Gy-5 Gy with Ir-192 energy. Linearity (R2 = 1) was observed in the MOSFET signal with the applied dose range of 0.3 Gy-5 Gy with Ir-192 energy. Fading effects were less than 1% after 10 min and the MOSFET detectors stayed stable (within 5%) over a period of 1 month. The MOSFET response was found to be decreased by approximately 1.5% at 37 degrees C compared to 20 degrees C. The isotropic response of the MOSFET was found to be within +/-6%. A maximum deviation of 5.5% was obtained between 0 degrees and 180 degrees for both the axes and this should be considered in clinical applications. The small size, cable-less, instant readout, permanent storage of dose and ease of use make the MOSFET a novel dosimeter and beneficial to patients for skin dose measurements with HDRBT using an Ir-192 source compared to the labour demanding and time-consuming TLDs.

Performance evaluation of a direct-conversion flat-panel detector system in imaging and quality assurance for a high-dose-rate 192Ir source

NASA Astrophysics Data System (ADS)

Miyahara, Yoshinori; Hara, Yuki; Nakashima, Hiroto; Nishimura, Tomonori; Itakura, Kanae; Inomata, Taisuke; Kitagaki, Hajime

2018-03-01

In high-dose-rate (HDR) brachytherapy, a direct-conversion flat-panel detector (d-FPD) clearly depicts a 192Ir source without image halation, even under the emission of high-energy gamma rays. However, it was unknown why iridium is visible when using a d-FPD. The purpose of this study was to clarify the reasons for visibility of the source core based on physical imaging characteristics, including the modulation transfer functions (MTF), noise power spectral (NPS), contrast transfer functions, and linearity of d-FPD to high-energy gamma rays. The acquired data included: x-rays, [X]; gamma rays, [γ] dual rays (X  +  γ), [D], and subtracted data for depicting the source ([D]  -  [γ]). In the quality assurance (QA) test for the positional accuracy of a source core, the coordinates of each dwelling point were compared between the planned and actual source core positions using a CT/MR-compatible ovoid applicator and a Fletcher-Williamson applicator. The profile curves of [X] and ([D]  -  [γ]) matched well on MTF and NPS. The contrast resolutions of [D] and [X] were equivalent. A strongly positive linear correlation was found between the output data of [γ] and source strength (r 2  >  0.99). With regard to the accuracy of the source core position, the largest coordinate difference (3D distance) was noted at the maximum curvature of the CT/MR-compatible ovoid and Fletcher-Williamson applicators, showing 1.74  ±  0.02 mm and 1.01  ±  0.01 mm, respectively. A d-FPD system provides high-quality images of a source, even when high-energy gamma rays are emitted to the detector, and positional accuracy tests with clinical applicators are useful in identifying source positions (source movements) within the applicator for QA.

Impact of imaging approach on radiation dose and associated cancer risk in children undergoing cardiac catheterization

PubMed Central

Einstein, Andrew J.; Januzis, Natalie; Nguyen, Giao; Li, Jennifer S.; Fleming, Gregory A.; Yoshizumi, Terry K.

2016-01-01

Objectives To quantify the impact of image optimization on absorbed radiation dose and associated risk in children undergoing cardiac catheterization. Background Various imaging and fluoroscopy system technical parameters including camera magnification, source-to-image distance, collimation, anti-scatter grids, beam quality, and pulse rates, all affect radiation dose but have not been well studied in younger children. Methods We used anthropomorphic phantoms (ages: newborn and 5-years-old) to measure surface radiation exposure from various imaging approaches and estimated absorbed organ doses and effective doses (ED) using Monte Carlo simulations. Models developed in the National Academies’ Biological Effects of Ionizing Radiation VII report were used to compare an imaging protocol optimized for dose reduction versus suboptimal imaging (+20cm source-to-image-distance, +1 magnification setting, no collimation) on lifetime attributable risk (LAR) of cancer. Results For the newborn and 5-year-old phantoms respectively ED changes were as follows: +157% and +232% for an increase from 6-inch to 10-inch camera magnification; +61% and +59% for a 20cm increase in source-to-image-distance; −42% and −48% with addition of 1-inch periphery collimation; −31% and −46% with removal of the anti-scatter grid. Compared to an optimized protocol, suboptimal imaging increased ED by 2.75-fold (newborn) and 4-fold (5-year-old). Estimated cancer LAR from 30-minutes of postero-anterior fluoroscopy using optimized versus sub-optimal imaging respectively was: 0.42% versus 1.23% (newborn female), 0.20% vs 0.53% (newborn male), 0.47% versus 1.70% (5-year-old female) and 0.16% vs 0.69% (5-year-old male). Conclusions Radiation-related risks to children undergoing cardiac catheterization can be substantial but are markedly reduced with an optimized imaging approach. PMID:27315598

Impact of imaging approach on radiation dose and associated cancer risk in children undergoing cardiac catheterization.

PubMed

Hill, Kevin D; Wang, Chu; Einstein, Andrew J; Januzis, Natalie; Nguyen, Giao; Li, Jennifer S; Fleming, Gregory A; Yoshizumi, Terry K

2017-04-01

To quantify the impact of image optimization on absorbed radiation dose and associated risk in children undergoing cardiac catheterization. Various imaging and fluoroscopy system technical parameters including camera magnification, source-to-image distance, collimation, antiscatter grids, beam quality, and pulse rates, all affect radiation dose but have not been well studied in younger children. We used anthropomorphic phantoms (ages: newborn and 5 years old) to measure surface radiation exposure from various imaging approaches and estimated absorbed organ doses and effective doses (ED) using Monte Carlo simulations. Models developed in the National Academies' Biological Effects of Ionizing Radiation VII report were used to compare an imaging protocol optimized for dose reduction versus suboptimal imaging (+20 cm source-to-image-distance, +1 magnification setting, no collimation) on lifetime attributable risk (LAR) of cancer. For the newborn and 5-year-old phantoms, respectively ED changes were as follows: +157% and +232% for an increase from 6-inch to 10-inch camera magnification; +61% and +59% for a 20 cm increase in source-to-image-distance; -42% and -48% with addition of 1-inch periphery collimation; -31% and -46% with removal of the antiscatter grid. Compared with an optimized protocol, suboptimal imaging increased ED by 2.75-fold (newborn) and fourfold (5 years old). Estimated cancer LAR from 30-min of posteroanterior fluoroscopy using optimized versus suboptimal imaging, respectively was 0.42% versus 1.23% (newborn female), 0.20% versus 0.53% (newborn male), 0.47% versus 1.70% (5-year-old female) and 0.16% versus 0.69% (5-year-old male). Radiation-related risks to children undergoing cardiac catheterization can be substantial but are markedly reduced with an optimized imaging approach. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilczek, Krzysztof; Petelenz, Barbara; Strzala, Alicja

Purpose. Biological effects of intravascular brachytherapy are very sensitive to discrepancies between the prescription and the applied dose. If brachytherapy is aimed at in-stent restenosis, shielding and shadowing effects of metallic stents may change the dose distribution relative to that produced by the bare source. The development of new generations of stents inspired us to a new experimental study in this field. The effect was studied for 14 stents which we have recently encountered in clinical practice. Methods. The model source was a continuous 20-mm column of {sup 90}Sr/{sup 90}Y solution sealed in a 1-mm-I.D. Plexiglas capillary. The dose distributionmore » in the Plexiglas phantom was mapped using GafChromic MD-55-2 film. The stent masses varied from 2.5 to 25 mg; the strut thicknesses, from 0.075 to 0.15 mm; and the atomic numbers of stent materials, from 24 (Cr) to 79 (Au). Results. Dose perturbations depend on a variety of stent features. Local reduction of the mean dose rates near the reference distance (r{sub 0} = 2 mm) varied from 11% to 47%. No simple correlation was found between these data and stent characteristics, but it seems that the atomic number of the stent material is less important than the strut thickness and mesh density. Conclusion. The results provide a warning that clinical indications for in-stent radiation therapy must always be confronted with another aspect of the patient's history: the kind of implanted stent. Intravascular brachytherapy using pure beta sources may be recommended only for patients 'wearing' light, thin-strut stents. The presence of thick-strut stents is a contraindication for this modality, due to excessive dose perturbation.« less

Design and implementation of a film dosimetry audit tool for comparison of planned and delivered dose distributions in high dose rate (HDR) brachytherapy

NASA Astrophysics Data System (ADS)

Palmer, Antony L.; Lee, Chris; Ratcliffe, Ailsa J.; Bradley, David; Nisbet, Andrew

2013-10-01

A novel phantom is presented for ‘full system’ dosimetric audit comparing planned and delivered dose distributions in HDR gynaecological brachytherapy, using clinical treatment applicators. The brachytherapy applicator dosimetry test object consists of a near full-scatter water tank with applicator and film supports constructed of Solid Water, accommodating any typical cervix applicator. Film dosimeters are precisely held in four orthogonal planes bisecting the intrauterine tube, sampling dose distributions in the high risk clinical target volume, points A and B, bladder, rectum and sigmoid. The applicator position is fixed prior to CT scanning and through treatment planning and irradiation. The CT data is acquired with the applicator in a near clinical orientation to include applicator reconstruction in the system test. Gamma analysis is used to compare treatment planning system exported RTDose grid with measured multi-channel film dose maps. Results from two pilot audits are presented, using Ir-192 and Co-60 HDR sources, with a mean gamma passing rate of 98.6% using criteria of 3% local normalization and 3 mm distance to agreement (DTA). The mean DTA between prescribed dose and measured film dose at point A was 1.2 mm. The phantom was funded by IPEM and will be used for a UK national brachytherapy dosimetry audit.

Design and implementation of a film dosimetry audit tool for comparison of planned and delivered dose distributions in high dose rate (HDR) brachytherapy.

PubMed

Palmer, Antony L; Lee, Chris; Ratcliffe, Ailsa J; Bradley, David; Nisbet, Andrew

2013-10-07

A novel phantom is presented for 'full system' dosimetric audit comparing planned and delivered dose distributions in HDR gynaecological brachytherapy, using clinical treatment applicators. The brachytherapy applicator dosimetry test object consists of a near full-scatter water tank with applicator and film supports constructed of Solid Water, accommodating any typical cervix applicator. Film dosimeters are precisely held in four orthogonal planes bisecting the intrauterine tube, sampling dose distributions in the high risk clinical target volume, points A and B, bladder, rectum and sigmoid. The applicator position is fixed prior to CT scanning and through treatment planning and irradiation. The CT data is acquired with the applicator in a near clinical orientation to include applicator reconstruction in the system test. Gamma analysis is used to compare treatment planning system exported RTDose grid with measured multi-channel film dose maps. Results from two pilot audits are presented, using Ir-192 and Co-60 HDR sources, with a mean gamma passing rate of 98.6% using criteria of 3% local normalization and 3 mm distance to agreement (DTA). The mean DTA between prescribed dose and measured film dose at point A was 1.2 mm. The phantom was funded by IPEM and will be used for a UK national brachytherapy dosimetry audit.

Study of the biochemical indicators of chronic irradiation in rats.

PubMed

Szabo, L D; Benko, A B; Gyenge, L; Predmerszky, T

1976-01-01

Daily urinary excretion of pseudouridine, creatinine and creatine of chronically irradiated Wistar rats was estimated. The irradiation conditions were: 60Co gamma source, dose-rate 10 rad/day, total dose 200, 400 and 600 rad. Control groups were kept under similar conditions. Urine samples were taken three times after the end of the irradiation period. It was found that: (1) pseudouridine excretion seems more suitable for indicating radiation injury than the creatine/creatinine ratio in chronic irradiation in rats; (ii) there are significant changes in dose dependence of pseudouridine excretion in the post-irradiation period; (iii) a new method for pseudouridine estimation gives closely similar data to those of earlier investigations.

A medical image-based graphical platform -- features, applications and relevance for brachytherapy.

PubMed

Fonseca, Gabriel P; Reniers, Brigitte; Landry, Guillaume; White, Shane; Bellezzo, Murillo; Antunes, Paula C G; de Sales, Camila P; Welteman, Eduardo; Yoriyaz, Hélio; Verhaegen, Frank

2014-01-01

Brachytherapy dose calculation is commonly performed using the Task Group-No 43 Report-Updated protocol (TG-43U1) formalism. Recently, a more accurate approach has been proposed that can handle tissue composition, tissue density, body shape, applicator geometry, and dose reporting either in media or water. Some model-based dose calculation algorithms are based on Monte Carlo (MC) simulations. This work presents a software platform capable of processing medical images and treatment plans, and preparing the required input data for MC simulations. The A Medical Image-based Graphical platfOrm-Brachytherapy module (AMIGOBrachy) is a user interface, coupled to the MCNP6 MC code, for absorbed dose calculations. The AMIGOBrachy was first validated in water for a high-dose-rate (192)Ir source. Next, dose distributions were validated in uniform phantoms consisting of different materials. Finally, dose distributions were obtained in patient geometries. Results were compared against a treatment planning system including a linear Boltzmann transport equation (LBTE) solver capable of handling nonwater heterogeneities. The TG-43U1 source parameters are in good agreement with literature with more than 90% of anisotropy values within 1%. No significant dependence on the tissue composition was observed comparing MC results against an LBTE solver. Clinical cases showed differences up to 25%, when comparing MC results against TG-43U1. About 92% of the voxels exhibited dose differences lower than 2% when comparing MC results against an LBTE solver. The AMIGOBrachy can improve the accuracy of the TG-43U1 dose calculation by using a more accurate MC dose calculation algorithm. The AMIGOBrachy can be incorporated in clinical practice via a user-friendly graphical interface. Copyright © 2014 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

SU-F-T-62: Three-Dimensional Dosimetric Gamma Analysis for Impacts of Tissue Inhomogeneity Using Monte Carlo Simulation in Intracavitary Brachytheray for Cervix Carcinoma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Tran Thi Thao; Nakamoto, Takahiro; Shibayama, Yusuke

Purpose: The aim of this study was to investigate the impacts of tissue inhomogeneity on dose distributions using a three-dimensional (3D) gamma analysis in cervical intracavitary brachytherapy using Monte Carlo (MC) simulations. Methods: MC simulations for comparison of dose calculations were performed in a water phantom and a series of CT images of a cervical cancer patient (stage: Ib; age: 27) by employing a MC code, Particle and Heavy Ion Transport Code System (PHIT) version 2.73. The {sup 192}Ir source was set at fifteen dwell positions, according to clinical practice, in an applicator consisting of a tandem and two ovoids.more » Dosimetric comparisons were performed for the dose distributions in the water phantom and CT images by using gamma index image and gamma pass rate (%). The gamma index is the minimum Euclidean distance between two 3D spatial dose distributions of the water phantom and CT images in a same space. The gamma pass rates (%) indicate the percentage of agreement points, which mean that two dose distributions are similar, within an acceptance criteria (3 mm/3%). The volumes of physical and clinical interests for the gamma analysis were a whole calculated volume and a region larger than t% of a dose (close to a target), respectively. Results: The gamma pass rates were 77.1% for a whole calculated volume and 92.1% for a region within 1% dose region. The differences of 7.7% to 22.9 % between two dose distributions in the water phantom and CT images were found around the applicator region and near the target. Conclusion: This work revealed the large difference on the dose distributions near the target in the presence of the tissue inhomogeneity. Therefore, the tissue inhomogeneity should be corrected in the dose calculation for clinical treatment.« less

Characterization of neutron calibration fields at the TINT's 50 Ci americium-241/beryllium neutron irradiator

NASA Astrophysics Data System (ADS)

Liamsuwan, T.; Channuie, J.; Ratanatongchai, W.

2015-05-01

Reliable measurement of neutron radiation is important for monitoring and protection in workplace where neutrons are present. Although Thailand has been familiar with applications of neutron sources and neutron beams for many decades, there is no calibration facility dedicated to neutron measuring devices available in the country. Recently, Thailand Institute of Nuclear Technology (TINT) has set up a multi-purpose irradiation facility equipped with a 50 Ci americium-241/beryllium neutron irradiator. The facility is planned to be used for research, nuclear analytical techniques and, among other applications, calibration of neutron measuring devices. In this work, the neutron calibration fields were investigated in terms of neutron energy spectra and dose equivalent rates using Monte Carlo simulations, an in-house developed neutron spectrometer and commercial survey meters. The characterized neutron fields can generate neutron dose equivalent rates ranging from 156 μSv/h to 3.5 mSv/h with nearly 100% of dose contributed by neutrons of energies larger than 0.01 MeV. The gamma contamination was less than 4.2-7.5% depending on the irradiation configuration. It is possible to use the described neutron fields for calibration test and routine quality assurance of neutron dose rate meters and passive dosemeters commonly used in radiation protection dosimetry.

Low dose or low dose rate ionizing radiation-induced health effect in the human.

PubMed

Tang, Feng Ru; Loganovsky, Konstantin

2018-06-05

The extensive literature review on human epidemiological studies suggests that low dose ionizing radiation (LDIR) (≤100 mSv) or low dose rate ionizing radiation (LDRIR) (<6mSv/H) exposure could induce either negative or positive health effects. These changes may depend on genetic background, age (prenatal day for embryo), sex, nature of radiation exposure, i.e., acute or chronic irradiation, radiation sources (such as atomic bomb attack, fallout from nuclear weapon test, nuclear power plant accidents, 60 Co-contaminated building, space radiation, high background radiation, medical examinations or procedures) and radionuclide components and human epidemiological experimental designs. Epidemiological and clinical studies show that LDIR or LDRIR exposure may induce cancer, congenital abnormalities, cardiovascular and cerebrovascular diseases, cognitive and other neuropsychiatric disorders, cataracts and other eye and somatic pathology (endocrine, bronchopulmonary, digestive, etc). LDIR or LDRIR exposure may also reduce mutation and cancer mortality rates. So far, the mechanisms of LDIR- or LDRIR -induced health effect are poorly understood. Further extensive studies are still needed to clarify under what circumstances, LDIR or LDRIR exposure may induce positive or negative effects, which may facilitate development of new therapeutic approaches to prevent or treat the radiation-induced human diseases or enhance radiation-induced positive health effect. Copyright © 2018 Elsevier Ltd. All rights reserved.

Radiation Damage in Si Diodes from Short, Intense Ion Pulses

NASA Astrophysics Data System (ADS)

de Leon, S. J.; Ludewigt, B. A.; Persaud, A.; Seidl, P. A.; Schenkel, T.

2017-10-01

The Neutralized Drift Compression Experiment (NDCX-II) at Berkeley Lab is an induction accelerator studying the effects that concentrated ion beams have on various materials. Charged particle radiation damage was the focus of this research - we have characterized a series of Si diodes using an electrometer and calibrated the diodes response using an 241Am alpha source, both before and after exposing the diodes to 1 MeV He ions in the accelerator. The key part here is that the high intensity pulses from NDCX-II (>1010 ions/cm2 per pulse in <20 ns) enabled a systematic study of dose-rate effects. An example of a dose-rate effect in Si diodes is increased accumulation of defects due to damage from ions that bombard them in a short pulse. This accumulated damage leads to a reduction in the charge collection efficiency and an increase in leakage current. Testing dose-rate effects in Si diodes and other semiconductors is a crucial step in designing sustainable instruments that can encounter high doses of radiation, such as high intensity accelerators, fusion energy experiments and space applications and results from short pulses can inform models of radiation damage evolution. This work was supported by the Office of Science of the US Department of Energy under contract DE-AC0205CH11231.

Light dose versus rate of delivery: implications for macroalgal productivity.

PubMed

Desmond, Matthew J; Pritchard, Daniel W; Hepburn, Christopher D

2017-06-01

The role of how light is delivered over time is an area of macroalgal photosynthesis that has been overlooked but may play a significant role in controlling rates of productivity and the structure and persistence of communities. Here we present data that quantify the relative influence of total quantum dose and delivery rate on the photosynthetic productivity of five ecologically important Phaeophyceae species from southern New Zealand. Results suggested that greater net oxygen production occurs when light is delivered at a lower photon flux density (PFD) over a longer period compared to a greater PFD over a shorter period, given the same total dose. This was due to greater efficiency (α) at a lower PFD which, for some species, meant a compensatory effect can occur. This resulted in equal or greater productivity even when the total quantum dose of the lower PFD was significantly reduced. It was also shown that light limitation at Huriawa Peninsula, where macroaglae were sourced, may be restricting the acclimation potential of species at greater depths, and that even at shallow depth periods of significant light limitation are likely to occur. This research is of particular interest as the variability of light delivery to coastal reef systems increases as a result of anthropogenic disturbances, and as the value of in situ community primary productivity estimates is recognised.

Global real-time dose measurements using the Automated Radiation Measurements for Aerospace Safety (ARMAS) system

NASA Astrophysics Data System (ADS)

Tobiska, W. Kent; Bouwer, D.; Smart, D.; Shea, M.; Bailey, J.; Didkovsky, L.; Judge, K.; Garrett, H.; Atwell, W.; Gersey, B.; Wilkins, R.; Rice, D.; Schunk, R.; Bell, D.; Mertens, C.; Xu, X.; Wiltberger, M.; Wiley, S.; Teets, E.; Jones, B.; Hong, S.; Yoon, K.

2016-11-01

The Automated Radiation Measurements for Aerospace Safety (ARMAS) program has successfully deployed a fleet of six instruments measuring the ambient radiation environment at commercial aircraft altitudes. ARMAS transmits real-time data to the ground and provides quality, tissue-relevant ambient dose equivalent rates with 5 min latency for dose rates on 213 flights up to 17.3 km (56,700 ft). We show five cases from different aircraft; the source particles are dominated by galactic cosmic rays but include particle fluxes for minor radiation periods and geomagnetically disturbed conditions. The measurements from 2013 to 2016 do not cover a period of time to quantify galactic cosmic rays' dependence on solar cycle variation and their effect on aviation radiation. However, we report on small radiation "clouds" in specific magnetic latitude regions and note that active geomagnetic, variable space weather conditions may sufficiently modify the magnetospheric magnetic field that can enhance the radiation environment, particularly at high altitudes and middle to high latitudes. When there is no significant space weather, high-latitude flights produce a dose rate analogous to a chest X-ray every 12.5 h, every 25 h for midlatitudes, and every 100 h for equatorial latitudes at typical commercial flight altitudes of 37,000 ft ( 11 km). The dose rate doubles every 2 km altitude increase, suggesting a radiation event management strategy for pilots or air traffic control; i.e., where event-driven radiation regions can be identified, they can be treated like volcanic ash clouds to achieve radiation safety goals with slightly lower flight altitudes or more equatorial flight paths.

Systematic review of reporting rates of adverse events following immunization: an international comparison of post-marketing surveillance programs with reference to China.

PubMed

Guo, Biao; Page, Andrew; Wang, Huaqing; Taylor, Richard; McIntyre, Peter

2013-01-11

China is the most populous country in the world, with an annual birth cohort of approximately 16 million, requiring an average of 500 million vaccine doses administered annually. In China, over 30 domestic and less than 10 overseas vaccine manufacturers supply over 60 licensed vaccine products, representing a growing vaccine market mainly due to recent additions to the national immunization schedule, but data on post-marketing surveillance for adverse events following immunization (AEFI) are sparse. To compare reporting rates for various categories of AEFI from China with other routine post-marketing surveillance programs internationally. Systematic review of published studies reporting rates of AEFI by vaccine, category of reaction and age from post-marketing surveillance systems in English and Chinese languages. Overall AEFI reporting rates (all vaccines, all ages) in Chinese studies were consistent with those from similar international studies elsewhere, but there was substantial heterogeneity in regional reporting rates in China (range 2.3-37.8/100,000 doses). The highest AEFI reporting rates were for diphtheria-tetanus-pertussis whole-cell (DTwP) and acellular (DTaP) vaccines (range 3.3-181.1/100,000 doses for DTwP; range 3.5-92.6/100,000 doses for DTaP), with higher median rates for DTwP than DTaP, and higher than expected rates for DTaP vaccine. Similar higher rates for DTwP and DTaP containing vaccines, and relatively lower rates for vaccines against hepatitis B virus, poliovirus, and Japanese encephalitis virus were found in China and elsewhere in the world. Overall AEFI reporting rates in China were consistent with similar post-marketing surveillance systems in other countries. Sources of regional heterogeneity in AEFI reporting rates, and their relationships to differing vaccine manufacturers versus differing surveillance practices, require further exploration. Copyright © 2012 Elsevier Ltd. All rights reserved.

PCP METHODOLOGY FOR DETERMINING DOSE RATES FOR SMALL GRAM QUANTITIES IN SHIPPING PACKAGINGS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nathan, S.

The Small Gram Quantity (SGQ) concept is based on the understanding that small amounts of hazardous materials, in this case radioactive materials, are significantly less hazardous than large amounts of the same materials. This study describes a methodology designed to estimate an SGQ for several neutron and gamma emitting isotopes that can be shipped in a package compliant with 10 CFR Part 71 external radiation level limits regulations. These regulations require packaging for the shipment of radioactive materials perform, under both normal and accident conditions, the essential functions of material containment, subcriticality, and maintain external radiation levels within regulatory limits.more » 10 CFR 71.33(b)(1)(2)&(3) state radioactive and fissile materials must be identified and their maximum quantity, chemical and physical forms be included in an application. Furthermore, the U.S. Federal Regulations require application contain an evaluation demonstrating the package (i.e., the packaging and its contents) satisfies the external radiation standards for all packages (10 CFR 71.31(2), 71.35(a), & 71.47). By placing the contents in a He leak-tight containment vessel, and limiting the mass to ensure subcriticality, the first two essential functions are readily met. Some isotopes emit sufficiently strong photon radiation that small amounts of material can yield a large external dose rate. Quantifying of the dose rate for a proposed content is a challenging issue for the SGQ approach. It is essential to quantify external radiation levels from several common gamma and neutron sources that can be safely placed in a specific packaging, to ensure compliance with federal regulations. The Packaging Certification Program (PCP) Methodology for Determining Dose Rate for Small Gram Quantities in Shipping Packagings described in this report provides bounding mass limits for a set of proposed SGQ isotopes. Methodology calculations were performed to estimate external radiation levels for the 9977 shipping package using the MCNP radiation transport code to develop a set of response multipliers (Green's functions) for 'dose per particle' for each neutron and photon spectral group. The source spectrum for each isotope generated using the ORIGEN-S and RASTA computer codes was folded with the response multipliers to generate the dose rate per gram of each isotope in the 9977 shipping package and its associated shielded containers. The maximum amount of a single isotope that could be shipped within the regulatory limits contained in 10 CFR 71.47 for dose rate at the surface of the package is determined. If a package contains a mixture of isotopes, the acceptability for shipment can be determined by a sum of fractions approach. Furthermore, the results of this analysis can be easily extended to additional radioisotopes by simply evaluating the neutron and/or photon spectra of those isotopes and folding the spectral data with the Green's functions provided.« less

High dose rate brachytherapy source measurement intercomparison.

PubMed

Poder, Joel; Smith, Ryan L; Shelton, Nikki; Whitaker, May; Butler, Duncan; Haworth, Annette

2017-06-01

This work presents a comparison of air kerma rate (AKR) measurements performed by multiple radiotherapy centres for a single HDR 192 Ir source. Two separate groups (consisting of 15 centres) performed AKR measurements at one of two host centres in Australia. Each group travelled to one of the host centres and measured the AKR of a single 192 Ir source using their own equipment and local protocols. Results were compared to the 192 Ir source calibration certificate provided by the manufacturer by means of a ratio of measured to certified AKR. The comparisons showed remarkably consistent results with the maximum deviation in measurement from the decay-corrected source certificate value being 1.1%. The maximum percentage difference between any two measurements was less than 2%. The comparisons demonstrated the consistency of well-chambers used for 192 Ir AKR measurements in Australia, despite the lack of a local calibration service, and served as a valuable focal point for the exchange of ideas and dosimetry methods.

Comparison of TID Effects in Space-Like Variable Dose Rates and Constant Dose Rates

NASA Technical Reports Server (NTRS)

Harris, Richard D.; McClure, Steven S.; Rax, Bernard G.; Evans, Robin W.; Jun, Insoo

2008-01-01

The degradation of the LM193 dual voltage comparator has been studied at different TID dose rate profiles, including several different constant dose rates and a variable dose rate that simulates the behavior of a solar flare. A comparison of results following constant dose rate vs. variable dose rates is made to explore how well the constant dose rates used for typical part testing predict the performance during a simulated space-like mission. Testing at a constant dose rate equal to the lowest dose rate seen during the simulated flare provides an extremely conservative estimate of the overall amount of degradation. A constant dose rate equal to the average dose rate is also more conservative than the variable rate. It appears that, for this part, weighting the dose rates by the amount of total dose received at each rate (rather than the amount of time at each dose rate) results in an average rate that produces an amount of degradation that is a reasonable approximation to that received by the variable rate.

Accuracy Evaluation of Oncentra™ TPS in HDR Brachytherapy of Nasopharynx Cancer Using EGSnrc Monte Carlo Code.

PubMed

Hadad, K; Zohrevand, M; Faghihi, R; Sedighi Pashaki, A

2015-03-01

HDR brachytherapy is one of the commonest methods of nasopharyngeal cancer treatment. In this method, depending on how advanced one tumor is, 2 to 6 Gy dose as intracavitary brachytherapy is prescribed. Due to high dose rate and tumor location, accuracy evaluation of treatment planning system (TPS) is particularly important. Common methods used in TPS dosimetry are based on computations in a homogeneous phantom. Heterogeneous phantoms, especially patient-specific voxel phantoms can increase dosimetric accuracy. In this study, using CT images taken from a patient and ctcreate-which is a part of the DOSXYZnrc computational code, patient-specific phantom was made. Dose distribution was plotted by DOSXYZnrc and compared with TPS one. Also, by extracting the voxels absorbed dose in treatment volume, dose-volume histograms (DVH) was plotted and compared with Oncentra™ TPS DVHs. The results from calculations were compared with data from Oncentra™ treatment planning system and it was observed that TPS calculation predicts lower dose in areas near the source, and higher dose in areas far from the source relative to MC code. Absorbed dose values in the voxels also showed that TPS reports D90 value is 40% higher than the Monte Carlo method. Today, most treatment planning systems use TG-43 protocol. This protocol may results in errors such as neglecting tissue heterogeneity, scattered radiation as well as applicator attenuation. Due to these errors, AAPM emphasized departing from TG-43 protocol and approaching new brachytherapy protocol TG-186 in which patient-specific phantom is used and heterogeneities are affected in dosimetry.

Accuracy Evaluation of Oncentra™ TPS in HDR Brachytherapy of Nasopharynx Cancer Using EGSnrc Monte Carlo Code

PubMed Central

Hadad, K.; Zohrevand, M.; Faghihi, R.; Sedighi Pashaki, A.

2015-01-01

Background HDR brachytherapy is one of the commonest methods of nasopharyngeal cancer treatment. In this method, depending on how advanced one tumor is, 2 to 6 Gy dose as intracavitary brachytherapy is prescribed. Due to high dose rate and tumor location, accuracy evaluation of treatment planning system (TPS) is particularly important. Common methods used in TPS dosimetry are based on computations in a homogeneous phantom. Heterogeneous phantoms, especially patient-specific voxel phantoms can increase dosimetric accuracy. Materials and Methods In this study, using CT images taken from a patient and ctcreate-which is a part of the DOSXYZnrc computational code, patient-specific phantom was made. Dose distribution was plotted by DOSXYZnrc and compared with TPS one. Also, by extracting the voxels absorbed dose in treatment volume, dose-volume histograms (DVH) was plotted and compared with Oncentra™ TPS DVHs. Results The results from calculations were compared with data from Oncentra™ treatment planning system and it was observed that TPS calculation predicts lower dose in areas near the source, and higher dose in areas far from the source relative to MC code. Absorbed dose values in the voxels also showed that TPS reports D90 value is 40% higher than the Monte Carlo method. Conclusion Today, most treatment planning systems use TG-43 protocol. This protocol may results in errors such as neglecting tissue heterogeneity, scattered radiation as well as applicator attenuation. Due to these errors, AAPM emphasized departing from TG-43 protocol and approaching new brachytherapy protocol TG-186 in which patient-specific phantom is used and heterogeneities are affected in dosimetry. PMID:25973408

Charged particles radiation measurements with Liulin-MO dosimeter of FREND instrument aboard ExoMars Trace Gas Orbiter during the transit and in high elliptic Mars orbit

NASA Astrophysics Data System (ADS)

Semkova, Jordanka; Koleva, Rositza; Benghin, Victor; Dachev, Tsvetan; Matviichuk, Yuri; Tomov, Borislav; Krastev, Krasimir; Maltchev, Stephan; Dimitrov, Plamen; Mitrofanov, Igor; Malahov, Alexey; Golovin, Dmitry; Mokrousov, Maxim; Sanin, Anton; Litvak, Maxim; Kozyrev, Andrey; Tretyakov, Vladislav; Nikiforov, Sergey; Vostrukhin, Andrey; Fedosov, Fedor; Grebennikova, Natalia; Zelenyi, Lev; Shurshakov, Vyacheslav; Drobishev, Sergey

2018-03-01

ExoMars is a joint ESA-Rosscosmos program for investigating Mars. Two missions are foreseen within this program: one consisting of the Trace Gas Orbiter (TGO), that carries scientific instruments for the detection of trace gases in the Martian atmosphere and for the location of their source regions, plus an Entry, Descent and landing demonstrator Module (EDM), launched on March 14, 2016; and the other, featuring a rover and a surface platform, with a launch date of 2020. On October 19, 2016 TGO was inserted into high elliptic Mars' orbit. The dosimetric telescope Liulin-MO for measuring the radiation environment onboard the ExoMars 2016 TGO is a module of the Fine Resolution Epithermal Neutron Detector (FREND). Here we present first results from measurements of the charged particle fluxes, dose rates, Linear Energy Transfer (LET) spectra and estimation of dose equivalent rates in the interplanetary space during the cruise of TGO to Mars and first results from dosimetric measurements in high elliptic Mars' orbit. A comparison is made with the dose rates obtained by RAD instrument onboard Mars Science Laboratory during the cruise to Mars in 2011-2012 and with the Galactic Cosmic Rays (GCR) count rates provided by other particle detectors currently in space. The average measured dose rate in Si from GCR during the transit to Mars for the period April 22-September 15, 2016 is 372 ± 37 μGy d-1 and 390 ± 39 μGy d-1 in two perpendicular directions. The dose equivalent rate from GCR for the same time period is about 2 ± 0.3 mSv d-1. This is in good agreement with RAD results for radiation dose rate in Si from GCR in the interplanetary space, taking into account the different solar activity during the measurements of both instruments. About 10% increase of the dose rate, and 15% increase of the dose equivalent rate for 10.5 months flight is observed. It is due to the increase of Liulin-MO particle fluxes for that period and corresponds to the overall GCR intensity increase during the declining phase of the solar activity. Data show that during the cruise to Mars and back (6 months in each direction), taken during the declining of solar activity, the crewmembers of future manned flights to Mars will accumulate at least 60% of the total dose limit for the cosmonaut's/astronaut's career in case their shielding conditions are close to the average shielding of Liulin-MO detectors-about 10 g cm-2. The dosimetric measurements in high elliptic Mars' orbit demonstrate strong dependence of the GCR fluxes near the TGO pericenter on satellite's field of view shadowed by Mars.

External dose assessment in the Ukraine following the Chernobyl accident

NASA Astrophysics Data System (ADS)

Frazier, Remi Jordan Lesartre

While the physiological effects of radiation exposure have been well characterized in general, it remains unclear what the relationship is between large-scale radiological events and psychosocial behavior outcomes in individuals or populations. To investigate this, the National Science Foundation funded a research project in 2008 at the University of Colorado in collaboration with Colorado State University to expand the knowledge of complex interactions between radiation exposure, perception of risk, and psychosocial behavior outcomes by modeling outcomes for a representative sample of the population of the Ukraine which had been exposed to radiocontaminant materials released by the reactor accident at Chernobyl on 26 April 1986. In service of this project, a methodology (based substantially on previously published models specific to the Chernobyl disaster and the Ukrainian population) was developed for daily cumulative effective external dose and dose rate assessment for individuals in the Ukraine for as a result of the Chernobyl disaster. A software platform was designed and produced to estimate effective external dose and dose rate for individuals based on their age, occupation, and location of residence on each day between 26 April 1986 and 31 December 2009. A methodology was developed to transform published 137Cs soil deposition contour maps from the Comprehensive Atlas of Caesium Deposition on Europe after the Chernobyl Accident into a geospatial database to access these data as a radiological source term. Cumulative effective external dose and dose rate were computed for each individual in a 703-member cohort of Ukrainians randomly selected to be representative of the population of the country as a whole. Error was estimated for the resulting individual dose and dose rate values with Monte Carlo simulations. Distributions of input parameters for the dose assessment methodology were compared to computed dose and dose rate estimates to determine which parameters were driving the computed results. The mean external effective dose for all individuals in the cohort due to exposure to radiocontamination from the Chernobyl accident between 26 April 1986 and 31 December 2009 was found to be 1.2 mSv; the geometric mean was 0.84 mSv with a geometric standard deviation of 2.1. The mean value is well below the mean external effective dose expected due to typical background radiation (which in the United States over this time period would be 12.0 mSv). Sensitivity analysis suggests that the greatest driver of the distribution of individual dose estimates is lack of specific information about the daily behavior of each individual, specifically the portion of time each individual spent indoors (and shielded from radionuclides deposited on the soil) versus outdoors (and unshielded).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Purwaningsih, Anik

Dosimetric data for a brachytherapy source should be known before it used for clinical treatment. Iridium-192 source type H01 was manufactured by PRR-BATAN aimed to brachytherapy is not yet known its dosimetric data. Radial dose function and anisotropic dose distribution are some primary keys in brachytherapy source. Dose distribution for Iridium-192 source type H01 was obtained from the dose calculation formalism recommended in the AAPM TG-43U1 report using MCNPX 2.6.0 Monte Carlo simulation code. To know the effect of cavity on Iridium-192 type H01 caused by manufacturing process, also calculated on Iridium-192 type H01 if without cavity. The result ofmore » calculation of radial dose function and anisotropic dose distribution for Iridium-192 source type H01 were compared with another model of Iridium-192 source.« less

Determination of correction factors in beta radiation beams using Monte Carlo method.

PubMed

Polo, Ivón Oramas; Santos, William de Souza; Caldas, Linda V E

2018-06-15

The absorbed dose rate is the main characterization quantity for beta radiation. The extrapolation chamber is considered the primary standard instrument. To determine absorbed dose rates in beta radiation beams, it is necessary to establish several correction factors. In this work, the correction factors for the backscatter due to the collecting electrode and to the guard ring, and the correction factor for Bremsstrahlung in beta secondary standard radiation beams are presented. For this purpose, the Monte Carlo method was applied. The results obtained are considered acceptable, and they agree within the uncertainties. The differences between the backscatter factors determined by the Monte Carlo method and those of the ISO standard were 0.6%, 0.9% and 2.04% for 90 Sr/ 90 Y, 85 Kr and 147 Pm sources respectively. The differences between the Bremsstrahlung factors determined by the Monte Carlo method and those of the ISO were 0.25%, 0.6% and 1% for 90 Sr/ 90 Y, 85 Kr and 147 Pm sources respectively. Copyright © 2018 Elsevier Ltd. All rights reserved.

On the use of particle filters for electromagnetic tracking in high dose rate brachytherapy.

PubMed

Götz, Th I; Lahmer, G; Brandt, T; Kallis, K; Strnad, V; Bert, Ch; Hensel, B; Tomé, A M; Lang, E W

2017-09-12

Modern radiotherapy of female breast cancers often employs high dose rate brachytherapy, where a radioactive source is moved inside catheters, implanted in the female breast, according to a prescribed treatment plan. Source localization relative to the patient's anatomy is determined with solenoid sensors whose spatial positions are measured with an electromagnetic tracking system. Precise sensor dwell position determination is of utmost importance to assure irradiation of the cancerous tissue according to the treatment plan. We present a hybrid data analysis system which combines multi-dimensional scaling with particle filters to precisely determine sensor dwell positions in the catheters during subsequent radiation treatment sessions. Both techniques are complemented with empirical mode decomposition for the removal of superimposed breathing artifacts. We show that the hybrid model robustly and reliably determines the spatial positions of all catheters used during the treatment and precisely determines any deviations of actual sensor dwell positions from the treatment plan. The hybrid system only relies on sensor positions measured with an EMT system and relates them to the spatial positions of the implanted catheters as initially determined with a computed x-ray tomography.

Poster — Thur Eve — 38: Feasibility of a Table-Top Total Body Irradiation Technique using Robotic Couch Motion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chin, Erika; Otto, Karl; Hoppe, Richard

Purpose: To develop and test the feasibility of a table-top implementation for total body irradiation (TBI) via robotic couch motion and coordinated monitor unit modulation on a standard C-arm linac geometry. Methods: To allow for collision free delivery and to maximize the effective field size, the couch was rotated to 270° IEC and dropped to 150 cm from the vertical radiation source. The robotic delivery was programmed using the TrueBeam STx Developer Mode using custom XML scripting. To assess the dosimetry of a sliding 30×20 cm{sup 2} field, irradiation on a solid water phantom of varying thickness was analyzed usingmore » EDR2 radiographic film and OSLDs. Beam modulation was achieved by dividing the couch path into multiple segments of varying dose rates and couch speeds in order to deliver 120 cGy to the midline. Results: The programmed irradiation in conjunction with coordinated couch motion was successfully delivered on a TrueBeam linac. When no beam modulation was employed, the dose difference between two different phantom sections was 17.0%. With simple beam modulation via changing dose rates and couch speeds, the desired prescription dose can be achieved at the centre of each phantom section within 1.9%. However, dose deviation at the junction was 9.2% due to the nonphysical change in the phantom thickness. Conclusions: The feasibility of robotic table-top TBI on a C-arm linac geometry was experimentally demonstrated. To achieve a more uniform dose distribution, inverse-planning allowing for a combination of dose rate modulation, jaw tracking and MLC motion is under investigation.« less

Characterization of Thymol blue Radiochromic dosimeters for high dose applications

NASA Astrophysics Data System (ADS)

Aldweri, Feras M.; Abuzayed, Manar H.; Al-Ajaleen, Musab S.; Rabaeh, Khalid A.

2018-03-01

Thymol blue (TB) solutions and Thymol blue Polyvinyl Alcohol (TB-PVA) films have been introduced as Radiochromic dosimeter for high dose applications. The dosimeters were irradiated with gamma ray (60Co source) from 5 to 30 kGy for film, and from 0.150 kGy to 4 kGy for solution. The optical density of unirradiated and irradiated TB solution as well as TB-PVA film dosimeters were studied in terms of absorbance at 434 nm using UV/VIS spectrophotometer. The effects of scan temperature, light pre-gamma irradiation, dose rate, relative humidity and stability of the absorbance of solutions and films after irradiation were investigated. We found the dose sensitivity of TB solution and TB-PVA film dosimeters increases significantly with increases of the absorbed dose as well as with the increases of TB dye concentrations. The useful dose range of developed TB solutions and TB-PVA films dosimeters is in the range 0.125-1 kGy and of 5-20 kGy, respectively.

Measures for curtailment of iatrogenic exposure. Guide to correct x-ray examinations (in Japanese)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Misonoo, K.

1973-08-01

Of the coposure dose for humans from various radiation sources, introgenic exposure amounts to 1/2 to twice the natural radiation source. Although the mechanism of induction of malignant tumor by radiation is not clanified, it is evident that it is induced after receiving a dose above 100 rads. However, the presence of a threshold, under which it does not develop, is unknown. Tabulated were ICRP's calculations on the degree of risk of injury and the estimated values of genetic injury due to 1 rad. In order to estimate the harmful effect of exposure in x-ray diagnosis, the dose in themore » critical tissue of the human body and the types and the frequency of radiation examinations are important. The judgment of genetic injury is expressed by the genetically significant dose, which is calculated from the dose in the genital gland received by individuals. The impcrtant criterion for the judgment of physical injury is the mean annual dose per person in the marrow (mean dose in the red marrow). The dose in the genital organ is important as the dose related to the evaluation of the degree of genetic risk. The characteristics of iatrogenic exposure are partial and acute exposure and a high dose rate. Tabulated individually were the frequency of x-ray examinations, the mean dose in the genital organ according urce. The radiation dose during x-ray pelvimetry to 51 patients was estimated, and the cytogenetic response of peripheral lymphocytes was determined in 25 of their newborn babies. The calculations resulted in an average midline fetal dose of 1,035 and 1,860 mrads for the patients receiving 2 projections and more than 2 projections, respectively. There was no evidence of radioinduced chromosomal darnage in the newborn infants following x-ray exposure in utero. (auth)« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Marsh, I; Otto, M; Weichert, J

Purpose: The focus of this work is to perform Monte Carlo-based dosimetry for several pediatric cancer xenografts in mice treated with a novel radiopharmaceutical {sup 131}I-CLR1404. Methods: Four mice for each tumor cell line were injected with 8–13 µCi/g of the {sup 124}124I-CLR1404. PET/CT images of each individual mouse were acquired at 5–6 time points over the span of 96–170 hours post-injection. Following acquisition, the images were co-registered, resampled, rescaled, corrected for partial volume effects (PVE), and masked. For this work the pre-treatment PET images of {sup 124}I-CLR1404 were used to predict therapeutic doses from {sup 131}I-CLR1404 at each timemore » point by assuming the same injection activity and accounting for the difference in physical decay rates. Tumors and normal tissues were manually contoured using anatomical and functional images. The CT and the PET images were used in the Geant4 (v9.6) Monte Carlo simulation to define the geometry and source distribution, respectively. The total cumulated absorbed dose was calculated by numerically integrating the dose-rate at each time point over all time on a voxel-by-voxel basis. Results: Spatial distributions of the absorbed dose rates and dose volume histograms as well as mean, minimum, maximum, and total dose values for each ROI were generated for each time point. Conclusion: This work demonstrates how mouse-specific MC-based dosimetry could potentially provide more accurate characterization of efficacy of novel radiopharmaceuticals in radionuclide therapy. This work is partially funded by NIH grant CA198392.« less

Randomized controlled trial of a dose consolidation program.

PubMed

Delate, Thomas; Fairman, Kathleen A; Carey, Shelly M; Motheral, Brenda R

2004-01-01

To evaluate the effectiveness and financial impact of a drug dose consolidation (optimization) program using letter intervention. This pilot program in a large, mid-Atlantic health plan utilized a randomized controlled trial research design. A review of adjudicated pharmacy claims records was performed monthly for 3 consecutive months from November 2002 through February 2003 to identify inefficient (i.e., >once-daily) regimens for any one of 68 dosage strengths of 37 single-source maintenance drugs with once-daily dosing recommendations. Prescribers who had prescribed one or more inefficient regimens were identified and randomized to one of the 2 intervention arms or a control arm. Prescribers in both intervention arms were sent personalized letters with information on their patients. inefficient regimens and suggested dose consolidation options. Patients of prescribers in one intervention arm received a complementary, patient-oriented letter. Pharmacy claims for patients in all arms were examined at 180 days after the date of the letter mailing for conversion to an efficient (once-daily) regimen. Financial modeling analysis calculated net savings as changes in pharmacy expenditures minus administrative costs. A total of 2,614 inefficient regimens, representing 6.7% of claims for the targeted medications, were identified. The rate of consolidation to a suggested dosing option was lower for the Physician Letter arm (7.3%) than for the Physician/Member Letter arm (10.2%) (P = 0.046). Both intervention arms had higher consolidation rates than the Control arm (3.9%) (P = 0.018 and P = 0.000, respectively.). Approximately 30% of the regimens in each study arm were never refilled after being targeted. Financial modeling indicated that a dose consolidation intervention could save 0.03 dollars to 0.07 dollars per member per month (PMPM) in 2003 dollars with full medication compliance but only 0.02 dollars to 0.03 dollars PMPM when savings were calculated with realistic, partial compliance rates. Subanalyses performed at the drug therapy class level revealed few opportunities to justify implementing a dose consolidation program. After taking into consideration program administrative costs, high rates of refill discontinuation, and dose consolidation that occurs naturally without intervention, the results indicated that a letter-based dose consolidation program did not appreciably decrease pharmacy expenditures.

Calculation note for an underground leak which remains underground

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goldberg, H.J.

1997-05-20

This calculation note supports the subsurface leak accident scenario which remains subsurface. It is assumed that a single walled pipe carrying waste from tank 106-C ruptures, releasing the liquid waste into the soil. In this scenario, the waste does not form a surface pool, but remains subsurface. However, above the pipe is a berm, 0.762 m (2.5 ft) high and 2.44 m (8 ft) wide, and the liquid released from the leak rises into the berm. The slurry line, which transports a source term of higher activity than the sluice line, leaks into the soil at a rate of 5%more » of the maximum flow rate of 28.4 L/s (450 gpm) for twelve hours. The dose recipient was placed a perpendicular distance of 100 m from the pipe. Two source terms were considered, mitigated and unmitigated release as described in section 3.4.1 of UANF-SD-WM-BIO-001, Addendum 1. The unmitigated consisted of two parts of AWF liquid and one part AWF solid. The mitigated release consisted of two parts SST liquid, eighteen parts AWF liquid, nine parts SST solid, and one part AWF solid. The isotopic breakdown of the release in these cases is presented. Two geometries were considered in preliminary investigations, disk source, and rectangular source. Since the rectangular source results from the assumption that the contamination is wicked up into the berm, only six inches of shielding from uncontaminated earth is present, while the disk source, which remains six inches below the level of the surface of the land is often shielded by a thick shield due to the slant path to the dose point. For this reason, only the rectangular source was considered in the final analysis. The source model was a rectangle 2.134 m (7 ft) thick, 0.6096 m (2 ft) high, and 130.899 m (131 ft) long. The top and sides of this rectangular source was covered with earth of density 1.6 g/cm{sup 3} to a thickness of 15.24 cm (6 in). This soil is modeled as 40% void space. The source consisted of earth of the same density with the void spaces filled with the liquid waste which added 0.56 g/cm{sup 3} to the density. The dose point was 100 m (328 ft) away from the berm in a perpendicular direction off the center. The computer code MICROSKYSHINEO was used to calculate the skyshine from the source. This code calculates exposure rate at the receptor point. The photon spectrum from 2 MeV to 0.15 MeV, obtained from ISOSHLD, was used as input, although this did not differ substantially from the results obtained from using Co, 137mBa, and 154Eu. However, this methodology allowed the bremsstrahlung contribution to be included in the skyshine calculation as well as in the direct radiation calculation.« less

Study of some health physics parameters of bismuth-ground granulated blast furnace slag shielding concretes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Sandeep, E-mail: sandeep0078monu@gmail.com; Singh, Sukhpal, E-mail: sukhpal-78@rediffmail.com

2016-05-06

The Bismuth-ground granulated blastfurnace slang (Bi-GGBFS) concrete samples were prepared. The weight percentage of different elements present in Bi-GGBFS Shielding concretewas evaluated by Energy Dispersive X-ray Microanalysis (EDX). The exposure rate and absorbed dose rate characteristics were calculated theoretically for radioactive sources namely {sup 241}Am and {sup 137}Cs. Our calculations reveal that the Bi-GGBFS concretes are effective in shielding material for gamma radiations.

Dosimetric characteristics of a new unit for electronic skin brachytherapy

PubMed Central

Garcia-Martinez, Teresa; Chan, Jan-Pieter; Perez-Calatayud, Jose

2014-01-01

Purpose Brachytherapy with radioactive high dose rate (HDR) 192Ir source is applied to small skin cancer lesions, using surface applicators, i.e. Leipzig or Valencia type. New developments in the field of radiotherapy for skin cancer include electronic brachytherapy. This technique involves the placement of an HDR X-ray source close to the skin, therefore combining the benefits of brachytherapy with the reduced shielding requirements and targeted energy of low energy X-rays. Recently, the Esteya® Electronic Brachytherapy System (Esteya EBS, Elekta AB-Nucletron, Stockholm, Sweden) has been developed specifically for HDR brachytherapy treatment of surface lesions. The system provides radionuclide free HDR brachytherapy by means of a small 69.5 kV X-ray source. The purpose of this study is to obtain the dosimetric characterization required for clinical implementation, providing the detailed methodology to perform the commissioning. Material and methods Flatness, symmetry and penumbra, percentage of depth dose (PDD), kV stability, HVL, output, spectrum, linearity, and leakage have been evaluated for a set of applicators (from 10 mm to 30 mm in diameter). Results Flatness and symmetry resulted better than 5% with around 1 mm of penumbra. The depth dose gradient is about 7%/mm. A kV value of 68.4 ± 1.0 kV (k = 1) was obtained, in good agreement with manufacturer data (69.5 kV). HVL was 1.85 mm Al. Dose rate for a typical 6 Gy to 7 Gy prescription resulted about 3.3 Gy/min and the leakage value was < 100 µGy/min. Conclusions The new Esteya® Electronic Brachytherapy System presents excellent flatness and penumbra as with the Valencia applicator case, combined with an improved PDD, allowing treatment of lesions of up to a depth of 5 mm in combination with reduced treatment duration. The Esteya unit allows HDR brachytherapy superficial treatment within a minimally shielded environment due its low energy. PMID:24790622

Calibration of GafChromic EBT3 for absorbed dose measurements in 5 MeV proton beam and (60)Co γ-rays.

PubMed

Vadrucci, M; Esposito, G; Ronsivalle, C; Cherubini, R; Marracino, F; Montereali, R M; Picardi, L; Piccinini, M; Pimpinella, M; Vincenti, M A; De Angelis, C

2015-08-01

To study EBT3 GafChromic film in low-energy protons, and for comparison purposes, in a reference (60)Co beam in order to use it as a calibrated dosimetry system in the proton irradiation facility under construction within the framework of the Oncological Therapy with Protons (TOP)-Intensity Modulated Proton Linear Accelerator for RadioTherapy (IMPLART) Project at ENEA-Frascati, Italy. EBT3 film samples were irradiated at the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Legnaro, Italy, with a 5 MeV proton beam generated by a 7 MV Van de Graaff CN accelerator. The nominal dose rates used were 2.1 Gy/min and 40 Gy/min. The delivered dose was determined by measuring the particle fluence and the energy spectrum in air with silicon surface barrier detector monitors. A preliminary study of the EBT3 film beam quality dependence in low-energy protons was conducted by passively degrading the beam energy. EBT3 films were also irradiated at ENEA-National Institute of Ionizing Radiation Metrology with gamma radiation produced by a (60)Co source characterized by an absorbed dose to water rate of 0.26 Gy/min as measured by a calibrated Farmer type ionization chamber. EBT3 film calibration curves were determined by means of a set of 40 film pieces irradiated to various doses ranging from 0.5 Gy to 30 Gy absorbed dose to water. An EPSON Expression 11000XL color scanner in transmission mode was used for film analysis. Scanner response stability, intrafilm uniformity, and interfilm reproducibility were verified. Optical absorption spectra measurements were performed on unirradiated and irradiated EBT3 films to choose the most sensitive color channel to the dose range used. EBT3 GafChromic films show an under response up to about 33% for low-energy protons with respect to (60)Co gamma radiation, which is consistent with the linear energy transfer dependence already observed with higher energy protons, and a negligible dose-rate dependence in the 2-40 Gy/min range. Short- and long-term scanner stabilities were 0.5% and 1.5%, respectively; film uniformity and reproducibility were better than 0.5%. The main purpose of this study was to implement EBT3 dosimetry in the proton low-energy radiobiology line of the TOP-IMPLART accelerator, having a maximum energy of 7 MeV. Low-energy proton and (60)Co calibrated sources were used to investigate the behavior of film response vs to be written in italicum dose. The calibration in 5 MeV protons is currently used for dose assessment in the radiobiological experiments at the TOP-IMPLART accelerator carried out at that energy value.

SU-F-T-524: Investigation of the Dosimertric Benefits of Interchangeable Source Size of a Novel Rotating Gamma System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eldib, A; Chibani, O; Chen, L

Purpose: Tremendous technological developments were made for conformal therapy techniques with linear accelerators, while less attention was paid to cobalt-60 units. The aim of the current study is to explore the dosimetric benefits of a novel rotating gamma ray system enhanced with interchangeable source sizes and multi-leaf collimator (MLC). Material and Methods: CybeRT is a novel rotating gamma ray machine with a ring gantry that ensures an iso-center accuracy of less than 0.3 mm. The new machine has a 70cm source axial distance allowing for improved penumbra compared to conventional machines. MCBEAM was used to simulate Cobalt-60 beams from themore » CybeRT head, while the MCPLAN code was used for modeling the MLC and for phantom/patient dose calculation. The CybeRT collimation will incorporate a system allowing for interchanging source sizes. In this work we have created phase space files for 1cm and 2cm source sizes. Evaluation of the system was done by comparing CybeRT beams with the 6MV beams in a water phantom and in patient geometry. Treatment plans were compared based on isodose distributions and dose volume histograms. Results: Profiles for the 1cm source were comparable to that from 6MV in the order of 6mm for 10×10 cm{sup 2} field size at the depth of maximum dose. This could ascribe to Cobalt-60 beams producing lowerenergy secondary electrons. Although, the 2cm source have a larger penumbra however it could be still used for large targets with proportionally increased dose rate. For large lung targets, the difference between cobalt and 6MV plans is clinically insignificant. Our preliminary results showed that interchanging source sizes will allow cobalt beams for volumetric arc therapy of both small lesions and large tumors. Conclusion: The CybeRT system will be a cost effective machine capable of performing advanced radiation therapy treatments of both small tumors and large target volumes.« less

Dose properties of a laser accelerated electron beam and prospects for clinical application.

PubMed

Kainz, K K; Hogstrom, K R; Antolak, J A; Almond, P R; Bloch, C D; Chiu, C; Fomytskyi, M; Raischel, F; Downer, M; Tajima, T

2004-07-01

Laser wakefield acceleration (LWFA) technology has evolved to where it should be evaluated for its potential as a future competitor to existing technology that produces electron and x-ray beams. The purpose of the present work is to investigate the dosimetric properties of an electron beam that should be achievable using existing LWFA technology, and to document the necessary improvements to make radiotherapy application for LWFA viable. This paper first qualitatively reviews the fundamental principles of LWFA and describes a potential design for a 30 cm accelerator chamber containing a gas target. Electron beam energy spectra, upon which our dose calculations are based, were obtained from a uniform energy distribution and from two-dimensional particle-in-cell (2D PIC) simulations. The 2D PIC simulation parameters are consistent with those reported by a previous LWFA experiment. According to the 2D PIC simulations, only approximately 0.3% of the LWFA electrons are emitted with an energy greater than 1 MeV. We studied only the high-energy electrons to determine their potential for clinical electron beams of central energy from 9 to 21 MeV. Each electron beam was broadened and flattened by designing a dual scattering foil system to produce a uniform beam (103%>off-axis ratio>95%) over a 25 x 25 cm2 field. An energy window (deltaE) ranging from 0.5 to 6.5 MeV was selected to study central-axis depth dose, beam flatness, and dose rate. Dose was calculated in water at a 100 cm source-to-surface distance using the EGS/BEAM Monte Carlo algorithm. Calculations showed that the beam flatness was fairly insensitive to deltaE. However, since the falloff of the depth-dose curve (R10-R90) and the dose rate both increase with deltaE, a tradeoff between minimizing (R10-R90) and maximizing dose rate is implied. If deltaE is constrained so that R10-R90 is within 0.5 cm of its value for a monoenergetic beam, the maximum practical dose rate based on 2D PIC is approximately 0.1 Gy min(-1) for a 9 MeV beam and 0.03 Gy min(-1) for a 15 MeV beam. It was concluded that current LWFA technology should allow a table-top terawatt (T3) laser to produce therapeutic electron beams that have acceptable flatness, penetration, and falloff of depth dose; however, the dose rate is still 1%-3% of that which would be acceptable, especially for higher-energy electron beams. Further progress in laser technology, e.g., increasing the pulse repetition rate or number of high energy electrons generated per pulse, is necessary to give dose rates acceptable for electron beams. Future measurements confirming dosimetric calculations are required to substantiate our results. In addition to achieving adequate dose rate, significant engineering developments are needed for this technology to compete with current electron acceleration technology. Also, the functional benefits of LWFA electron beams require further study and evaluation.

Exposure of luminous marine bacteria to low-dose gamma-radiation.

PubMed

Kudryasheva, N S; Petrova, A S; Dementyev, D V; Bondar, A A

2017-04-01

The study addresses biological effects of low-dose gamma-radiation. Radioactive 137 Cs-containing particles were used as model sources of gamma-radiation. Luminous marine bacterium Photobacterium phosphoreum was used as a bioassay with the bioluminescent intensity as the physiological parameter tested. To investigate the sensitivity of the bacteria to the low-dose gamma-radiation exposure (≤250 mGy), the irradiation conditions were varied as follows: bioluminescence intensity was measured at 5, 10, and 20°С for 175, 100, and 47 h, respectively, at different dose rates (up to 4100 μGy/h). There was no noticeable effect of gamma-radiation at 5 and 10°С, while the 20°С exposure revealed authentic bioluminescence inhibition. The 20°С results of gamma-radiation exposure were compared to those for low-dose alpha- and beta-radiation exposures studied previously under comparable experimental conditions. In contrast to ionizing radiation of alpha and beta types, gamma-emission did not initiate bacterial bioluminescence activation (adaptive response). As with alpha- and beta-radiation, gamma-emission did not demonstrate monotonic dose-effect dependencies; the bioluminescence inhibition efficiency was found to be related to the exposure time, while no dose rate dependence was found. The sequence analysis of 16S ribosomal RNA gene did not reveal a mutagenic effect of low-dose gamma radiation. The exposure time that caused 50% bioluminescence inhibition was suggested as a test parameter for radiotoxicity evaluation under conditions of chronic low-dose gamma irradiation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Analysis of Radiation Transport Due to Activated Coolant in the ITER Neutral Beam Injection Cell

DOE Office of Scientific and Technical Information (OSTI.GOV)

Royston, Katherine; Wilson, Stephen C.; Risner, Joel M.

Detailed spatial distributions of the biological dose rate due to a variety of sources are required for the design of the ITER tokamak facility to ensure that all radiological zoning limits are met. During operation, water in the Integrated loop of Blanket, Edge-localized mode and vertical stabilization coils, and Divertor (IBED) cooling system will be activated by plasma neutrons and will flow out of the bioshield through a complex system of pipes and heat exchangers. This paper discusses the methods used to characterize the biological dose rate outside the tokamak complex due to 16N gamma radiation emitted by the activatedmore » coolant in the Neutral Beam Injection (NBI) cell of the tokamak building. Activated coolant will enter the NBI cell through the IBED Primary Heat Transfer System (PHTS), and the NBI PHTS will also become activated due to radiation streaming through the NBI system. To properly characterize these gamma sources, the production of 16N, the decay of 16N, and the flow of activated water through the coolant loops were modeled. The impact of conservative approximations on the solution was also examined. Once the source due to activated coolant was calculated, the resulting biological dose rate outside the north wall of the NBI cell was determined through the use of sophisticated variance reduction techniques. The AutomateD VAriaNce reducTion Generator (ADVANTG) software implements methods developed specifically to provide highly effective variance reduction for complex radiation transport simulations such as those encountered with ITER. Using ADVANTG with the Monte Carlo N-particle (MCNP) radiation transport code, radiation responses were calculated on a fine spatial mesh with a high degree of statistical accuracy. In conclusion, advanced visualization tools were also developed and used to determine pipe cell connectivity, to facilitate model checking, and to post-process the transport simulation results.« less

Analysis of Radiation Transport Due to Activated Coolant in the ITER Neutral Beam Injection Cell

DOE PAGES

Royston, Katherine; Wilson, Stephen C.; Risner, Joel M.; ...

2017-07-26

Detailed spatial distributions of the biological dose rate due to a variety of sources are required for the design of the ITER tokamak facility to ensure that all radiological zoning limits are met. During operation, water in the Integrated loop of Blanket, Edge-localized mode and vertical stabilization coils, and Divertor (IBED) cooling system will be activated by plasma neutrons and will flow out of the bioshield through a complex system of pipes and heat exchangers. This paper discusses the methods used to characterize the biological dose rate outside the tokamak complex due to 16N gamma radiation emitted by the activatedmore » coolant in the Neutral Beam Injection (NBI) cell of the tokamak building. Activated coolant will enter the NBI cell through the IBED Primary Heat Transfer System (PHTS), and the NBI PHTS will also become activated due to radiation streaming through the NBI system. To properly characterize these gamma sources, the production of 16N, the decay of 16N, and the flow of activated water through the coolant loops were modeled. The impact of conservative approximations on the solution was also examined. Once the source due to activated coolant was calculated, the resulting biological dose rate outside the north wall of the NBI cell was determined through the use of sophisticated variance reduction techniques. The AutomateD VAriaNce reducTion Generator (ADVANTG) software implements methods developed specifically to provide highly effective variance reduction for complex radiation transport simulations such as those encountered with ITER. Using ADVANTG with the Monte Carlo N-particle (MCNP) radiation transport code, radiation responses were calculated on a fine spatial mesh with a high degree of statistical accuracy. In conclusion, advanced visualization tools were also developed and used to determine pipe cell connectivity, to facilitate model checking, and to post-process the transport simulation results.« less

Calibration of helical tomotherapy machine using EPR/alanine dosimetry.

PubMed

Perichon, Nicolas; Garcia, Tristan; François, Pascal; Lourenço, Valérie; Lesven, Caroline; Bordy, Jean-Marc

2011-03-01

Current codes of practice for clinical reference dosimetry of high-energy photon beams in conventional radiotherapy recommend using a 10 x 10 cm2 square field, with the detector at a reference depth of 10 cm in water and 100 cm source to surface distance (SSD) (AAPM TG-51) or 100 cm source-to-axis distance (SAD) (IAEA TRS-398). However, the maximum field size of a helical tomotherapy (HT) machine is 40 x 5 cm2 defined at 85 cm SAD. These nonstandard conditions prevent a direct implementation of these protocols. The purpose of this study is twofold: To check the absorbed dose in water and dose rate calibration of a tomotherapy unit as well as the accuracy of the tomotherapy treatment planning system (TPS) calculations for a specific test case. Both topics are based on the use of electron paramagnetic resonance (EPR) using alanine as transfer dosimeter between the Laboratoire National Henri Becquerel (LNHB) 60Co-gamma-ray reference beam and the Institut Curie's HT beam. Irradiations performed in the LNHB reference 60Co-gamma-ray beam allowed setting up the calibration method, which was then implemented and tested at the LNHB 6 MV linac x-ray beam, resulting in a deviation of 1.6% (at a 1% standard uncertainty) relative to the reference value determined with the standard IAEA TRS-398 protocol. HT beam dose rate estimation shows a difference of 2% with the value stated by the manufacturer at a 2% standard uncertainty. A 4% deviation between measured dose and the calculation from the tomotherapy TPS was found. The latter was originated by an inadequate representation of the phantom CT-scan values and, consequently, mass densities within the phantom. This difference has been explained by the mass density values given by the CT-scan and used by the TPS which were not the true ones. Once corrected using Monte Carlo N-Particle simulations to validate the accuracy of this process, the difference between corrected TPS calculations and alanine measured dose values was then found to be around 2% (with 2% standard uncertainty on TPS doses and 1.5% standard uncertainty on EPR measurements). Beam dose rate estimation results were found to be in good agreement with the reference value given by the manufacturer at 2% standard uncertainty. Moreover, the dose determination method was set up with a deviation around 2% (at a 2% standard uncertainty).

Relative biologic effectiveness in terms of tumor response of {sup 125}I implants compared with {sup 60}Co gamma rays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lehnert, Shirley; Reniers, Brigitte; Verhaegen, Frank

2005-09-01

Purpose: To measure the relative biologic effectiveness (RBE) for {sup 125}I seeds compared with external beam radiotherapy using a clinically relevant in vivo system. Methods and Materials: Photon emission from a detailed source model was simulated using the Monte Carlo code MCNP4C, sampling from a {sup 125}I spectrum. The mouse RIF-1 tumor was treated with either temporary implant of an {sup 125}I seed or with {sup 60}Co gamma rays. The tumors were always the same size at the initiation of treatment, and the endpoint was growth inhibition. Results: The dose-response curve for both modalities was close to linear and wasmore » independent of the initial {sup 125}I activity (dose rate) for the range investigated. Calculation of the RBE for tumor response requires assigning a unique value for the tumor dose that is not homogenous but depends on the distance from the {sup 125}I source. Because tumor regrowth will depend on the subpopulation of cells that have the greatest probability of survival (i.e., those at the greatest distance from the {sup 125}I source), one approach is to use the dose to this population. On this basis, the RBE for {sup 125}I compared with {sup 60}Co gamma rays is 1.5. If the {sup 125}I dose is computed as the average dose to the tumor, corrected for the dose that is wasted as overkill in the cell population closest to the center of the {sup 125}I seed, the RBE is 1.4. Conclusion: The result, an RBE of 1.4-1.5 is similar to findings obtained by other methods, supporting the validity of this approach to derive an RBE with validity in a clinical context.« less

Radiation protection of staff in 111In radionuclide therapy--is the lead apron shielding effective?

PubMed

Lyra, M; Charalambatou, P; Sotiropoulos, M; Diamantopoulos, S

2011-09-01

(111)In (Eγ = 171-245 keV, t1/2 = 2.83 d) is used for targeted therapies of endocrine tumours. An average activity of 6.3 GBq is injected into the liver by catheterisation of the hepatic artery. This procedure is time-consuming (4-5 min) and as a result, both the physicians and the technical staff involved are subjected to radiation exposure. In this research, the efficiency of the use of lead apron has been studied as far as the radiation protection of the working staff is concerned. A solution of (111)In in a cylindrical scattering phantom was used as a source. Close to the scattering phantom, an anthropomorphic male Alderson RANDO phantom was positioned. Thermoluminescent dosemeters were located in triplets on the front surface, in the exit and in various depths in the 26th slice of the RANDO phantom. The experiment was repeated by covering the RANDO phantom by a lead apron 0.25 mm Pb equivalent. The unshielded dose rates and the shielded photon dose rates were measured. Calculations of dose rates by Monte Carlo N-particle transport code were compared with this study's measurements. A significant reduction of 65 % on surface dose was observed when using lead apron. A decrease of 30 % in the mean absorbed dose among the different depths of the 26th slice of the RANDO phantom has also been noticed. An accurate correlation of the experimental results with Monte Carlo simulation has been achieved.

Radiation streaming and skyshine evaluation for a proposed low-level radioactive waste assured isolation facility.

PubMed

Arno, Matthew; Hamilton, Ian S

2003-10-01

Texas is investigating the idea of building a long term waste storage facility, also known as an Assured Isolation Facility. This is an above-ground, retrievable low-level radioactive waste storage facility. A preliminary, scoping-level analysis has been extended to consider more complex scenarios of radiation streaming and skyshine by using MCNP to model the facility in greater detail. Using bounding source term assumptions, the radiation doses and dose rates are found to exceed applicable limits by an order of magnitude. By altering the facility design to fill in the hollow cores of the prefabricated concrete slabs used in the roof over the "high-gamma" rooms where the waste with greatest gamma radiation intensity is stored, dose rates outside the facility decrease by an order of magnitude. With the modified design, the annual dose at the site fenceline is less than the 1 mSv annual limit for exposure of the public. Within the site perimeter, modifying the roof results in an order of magnitude drop in the dose rate for personnel outside the facility and on the facility roof, as well as a significant drop inside the facility. Radiation streaming inside the facility can be lowered almost two orders of magnitude by placing operational restrictions to keep at least two rows of waste containers in front of the high-gamma room to cut down on the size of the path for streaming.

Background radiation: natural and man-made.

PubMed

Thorne, M C

2003-03-01

A brief overview and comparison is given of dose rates arising from natural background radiation and the fallout from atmospheric testing of nuclear weapons. Although there are considerable spatial variations in exposure to natural background radiation, it is useful to give estimates of worldwide average overall exposures from the various components of that background. Cosmic-ray secondaries of low linear energy transfer (LET), mainly muons and photons, deliver about 280 microSv a(-1). Cosmic-ray neutrons deliver about another 100 microSv a(-1). These low- and high-LET exposures are relatively uniform to the whole body. The effective dose rate from cosmogenic radionuclides is dominated by the contribution of 12 microSv a(-1) from 14C. This is due to relatively uniform irradiation of all organs and tissues from low-energy beta particles. Primordial radionuclides and their progeny (principally the 238U and 232Th series, and 40K) contribute about 480 microSv a(-1) of effective dose by external irradiation. This is relatively uniform photon irradiation of the whole body. Internally incorporated 40K contributes a further 165 microSv a(-1) of effective dose in adults, mainly from beta particles, but with a significant gamma component. Equivalent doses from 40K are somewhat higher in muscle than other soft tissues, but the distinction is less than a factor of three. Uranium and thorium series radionuclides give rise to an average effective dose rate of around 120 microSv a(-1). This includes a major alpha particle component, and exposures of radiosensitive tissues in lung, liver, kidney and the skeleton are recognised as important contributors to effective dose. Overall, these various sources give a worldwide average effective dose rate of about 1160 microSv a(-1). Exposure to 222Rn, 220Rn and their short-lived progeny has to be considered separately. This is very variable both within and between countries. For 222Rn and its progeny, a worldwide average effective dose rate is about 1105 microSv a(-1). For 220Rn and its progeny, the corresponding value is 91 microSv a(-1). In both cases, the effective dose is mainly due to a particle irradiation of the bronchial tissues of the lungs. Overall, the worldwide average effective dose rate from natural background is about 2400 microSv a(-1) or 2.4 mSv a(-1). For comparison, worldwide average effective dose rates from weapons fallout peaked at 113 microSv a(-1) (about 5% of natural background) in 1963 and have since fallen to about 5.5 microSv a(-1) (about 0.2% of natural background). These values perhaps serve to emphasise that even gross insults to the natural environment from anthropogenic releases of radioactive materials are likely to be of limited significance when set in the context of the ambient radioactive environment within which all organisms, including humans, have developed.

HDR {sup 192}Ir source speed measurements using a high speed video camera

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fonseca, Gabriel P.; Viana, Rodrigo S. S.; Yoriyaz, Hélio

Purpose: The dose delivered with a HDR {sup 192}Ir afterloader can be separated into a dwell component, and a transit component resulting from the source movement. The transit component is directly dependent on the source speed profile and it is the goal of this study to measure accurate source speed profiles. Methods: A high speed video camera was used to record the movement of a {sup 192}Ir source (Nucletron, an Elekta company, Stockholm, Sweden) for interdwell distances of 0.25–5 cm with dwell times of 0.1, 1, and 2 s. Transit dose distributions were calculated using a Monte Carlo code simulatingmore » the source movement. Results: The source stops at each dwell position oscillating around the desired position for a duration up to (0.026 ± 0.005) s. The source speed profile shows variations between 0 and 81 cm/s with average speed of ∼33 cm/s for most of the interdwell distances. The source stops for up to (0.005 ± 0.001) s at nonprogrammed positions in between two programmed dwell positions. The dwell time correction applied by the manufacturer compensates the transit dose between the dwell positions leading to a maximum overdose of 41 mGy for the considered cases and assuming an air-kerma strength of 48 000 U. The transit dose component is not uniformly distributed leading to over and underdoses, which is within 1.4% for commonly prescribed doses (3–10 Gy). Conclusions: The source maintains its speed even for the short interdwell distances. Dose variations due to the transit dose component are much lower than the prescribed treatment doses for brachytherapy, although transit dose component should be evaluated individually for clinical cases.« less

Waterborne gastroenteritis outbreak at a scouting camp caused by two norovirus genogroups: GI and GII.

PubMed

ter Waarbeek, Henriëtte L G; Dukers-Muijrers, Nicole H T M; Vennema, Harry; Hoebe, Christian J P A

2010-03-01

A cross-border gastroenteritis outbreak at a scouting camp was associated with drinking water from a farmer's well. A retrospective cohort study was performed to identify size and source of the outbreak, as well as other characteristics. Epidemiological investigation included standardized questionnaires about sex, age, risk exposures, illness and family members. Stool and water (100mL) samples were analyzed for bacteria, viruses and parasites. Questionnaires were returned by 84 scouts (response rate 82%), mean age of 13 years. The primary attack rate was 85% (diarrhoea and/or vomiting). Drinking water was the strongest independent risk factor showing a dose-response effect with 50%, 75%, 75%, 93% and 96% case prevalence for 0, 1, 2-3, 4-5 and >5 glasses consumed, respectively. Norovirus (GI.2 Southampton and GII.7 Leeds) was detected in 51 stool specimens (75%) from ill scouts. Water analysis showed fecal contamination, but no norovirus. The secondary attack rate was 20%. This remarkable outbreak was caused by a point-source infection with two genogroups of noroviruses most likely transmitted by drinking water from a well. Finding a dose-response relationship was striking. Specific measures to reduce the risk of waterborne diseases, outbreak investigation and a good international public health network are important.

Horizontal and trophic transfer of diflubenzuron and fipronil among grasshoppers (Melanoplus sanguinipes) and between grasshoppers and darkling beetles (Tenebrionidae).

PubMed

Smith, D I; Lockwood, J A

2003-04-01

The possibility of horizontal transmission of diflubenzuron and fipronil was assessed in rangeland grasshoppers. Laboratory studies of Melanoplus sanguinipes demonstrated that fipronil was horizontally transferred at lethal levels (p < 0.05) via cannibalism through four passages when the initial dose applied to a food source was 250 times the label rate for rangeland grasshopper and locust control (label rate is 4 g AI/ha). Mortality was 100% on the first three passages through cannibalism. At 25 and 1 times the label rate, fipronil was lethal (p < 0.05) only on the first cannibalistic passage. Diflubenzuron generated significant (p < 0.05) mortality via horizontal transmission through two passages when the initial dose applied to a food source was 2,000 times the label rate for rangeland grasshopper control (label rate is 8.71 g AI/ha). There was 100% mortality in the first passage via cannibalism. At 250 and 25 times the label rate, diflubenzuron was lethal only on the first cannibalistic passage. Field applications of these two acridicides followed by collection of cadavers (Amphitornus coloradus and Ageneotettix deorum) that were fed to M. sanguinipes in the laboratory revealed that fipronil (25 times the label rate) generated significant (p < 0.05) mortality through two passages and diflubenzuron (label rate) caused no mortality via necrophagy. Tenebrionid beetles fed grasshopper cadavers collected from the field application of fipronil yielded 45% mortality, compared with 25% mortality in the controls. These findings suggest that horizontal and trophic transfer probably play a nominal ecotoxicological role in rangeland grasshopper control programs with diflubenzuron, but the transfer of fipronil to grasshoppers, scavengers, and natural enemies via necrophagy may increase both the efficacy of control programs and their environmental affects.

Source terms, shielding calculations and soil activation for a medical cyclotron.

PubMed

Konheiser, J; Naumann, B; Ferrari, A; Brachem, C; Müller, S E

2016-12-01

Calculations of the shielding and estimates of soil activation for a medical cyclotron are presented in this work. Based on the neutron source term from the 18 O(p,n) 18 F reaction produced by a 28 MeV proton beam, neutron and gamma dose rates outside the building were estimated with the Monte Carlo code MCNP6 (Goorley et al 2012 Nucl. Technol. 180 298-315). The neutron source term was calculated with the MCNP6 code and FLUKA (Ferrari et al 2005 INFN/TC_05/11, SLAC-R-773) code as well as with supplied data by the manufacturer. MCNP and FLUKA calculations yielded comparable results, while the neutron yield obtained using the manufacturer-supplied information is about a factor of 5 smaller. The difference is attributed to the missing channels in the manufacturer-supplied neutron source terms which considers only the 18 O(p,n) 18 F reaction, whereas the MCNP and FLUKA calculations include additional neutron reaction channels. Soil activation was performed using the FLUKA code. The estimated dose rate based on MCNP6 calculations in the public area is about 0.035 µSv h -1 and thus significantly below the reference value of 0.5 µSv h -1 (2011 Strahlenschutzverordnung, 9 Auflage vom 01.11.2011, Bundesanzeiger Verlag). After 5 years of continuous beam operation and a subsequent decay time of 30 d, the activity concentration of the soil is about 0.34 Bq g -1 .

Skyshine analysis using energy and angular dependent dose-contribution fluxes obtained from air-over-ground adjoint calculation.

PubMed

Uematsu, Mikio; Kurosawa, Masahiko

2005-01-01

A generalised and convenient skyshine dose analysis method has been developed based on forward-adjoint folding technique. In the method, the air penetration data were prepared by performing an adjoint DOT3.5 calculation with cylindrical air-over-ground geometry having an adjoint point source (importance of unit flux to dose rate at detection point) in the centre. The accuracy of the present method was certified by comparing with DOT3.5 forward calculation. The adjoint flux data can be used as generalised radiation skyshine data for all sorts of nuclear facilities. Moreover, the present method supplies plenty of energy-angular dependent contribution flux data, which will be useful for detailed shielding design of facilities.

ANEMOS: A computer code to estimate air concentrations and ground deposition rates for atmospheric nuclides emitted from multiple operating sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miller, C.W.; Sjoreen, A.L.; Begovich, C.L.

This code estimates concentrations in air and ground deposition rates for Atmospheric Nuclides Emitted from Multiple Operating Sources. ANEMOS is one component of an integrated Computerized Radiological Risk Investigation System (CRRIS) developed for the US Environmental Protection Agency (EPA) for use in performing radiological assessments and in developing radiation standards. The concentrations and deposition rates calculated by ANEMOS are used in subsequent portions of the CRRIS for estimating doses and risks to man. The calculations made in ANEMOS are based on the use of a straight-line Gaussian plume atmospheric dispersion model with both dry and wet deposition parameter options. Themore » code will accommodate a ground-level or elevated point and area source or windblown source. Adjustments may be made during the calculations for surface roughness, building wake effects, terrain height, wind speed at the height of release, the variation in plume rise as a function of downwind distance, and the in-growth and decay of daughter products in the plume as it travels downwind. ANEMOS can also accommodate multiple particle sizes and clearance classes, and it may be used to calculate the dose from a finite plume of gamma-ray-emitting radionuclides passing overhead. The output of this code is presented for 16 sectors of a circular grid. ANEMOS can calculate both the sector-average concentrations and deposition rates at a given set of downwind distances in each sector and the average of these quantities over an area within each sector bounded by two successive downwind distances. ANEMOS is designed to be used primarily for continuous, long-term radionuclide releases. This report describes the models used in the code, their computer implementation, the uncertainty associated with their use, and the use of ANEMOS in conjunction with other codes in the CRRIS. A listing of the code is included in Appendix C.« less

MTS-6 detectors calibration by using ²³⁹Pu-Be neutron source.

PubMed

Wrzesień, Małgorzata; Albiniak, Łukasz; Al-Hameed, Hiba

2017-10-17

Thermoluminescent detectors, type MTS-6, containing isotope ⁶Li (lithium) are sensitive in the range of thermal neutron energy; the ²³⁹Pu-Be (plutonium-and-beryllium) source emits neutrons in the energy range from 1 to 11 MeV. These seemingly contradictory elements may be combined by using the paraffin moderator, a determined density of thermal neutrons in the paraffin block and a conversion coefficient neutron flux to kerma, not forgetting the simultaneous registration of the photon radiation inseparable from the companion neutron radiation. The main aim of this work is to present the idea of calibration of thermoluminescent detectors that consist of a ⁶Li isotope, by using ²³⁹Pu-Be neutron radiation source. In this work, MTS-6 and MTS-7 thermoluminescent detectors and a plutonium-and-beryllium (²³⁹Pu-Be) neutron source were used. Paraffin wax fills the block, acting as a moderator. The calibration idea was based on the determination of dose equivalent rate based on the average kerma rate calculated taking into account the empirically determined function describing the density of thermal neutron flux in the paraffin block and a conversion coefficient neutron flux to kerma. The calculated value of the thermal neutron flux density was 1817.5 neutrons/cm²/s and the average value of kerma rate determined on this basis amounted to 244 μGy/h, and the dose equivalent rate 610 μSv/h. The calculated value allowed for the assessment of the length of time of exposure of the detectors directly in the paraffin block. The calibration coefficient for the used batch of detectors is (6.80±0.42)×10^-7 Sv/impulse. Med Pr 2017;68(6):705-710. This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.

An environmental dose experiment

NASA Astrophysics Data System (ADS)

Peralta, Luis

2017-11-01

Several radiation sources worldwide contribute to the delivered dose to the human population. This radiation also acts as a natural background when detecting radiation, for instance from radioactive sources. In this work a medium-sized plastic scintillation detector is used to evaluate the dose delivered by natural radiation sources. Calibration of the detector involved the use of radioactive sources and Monte Carlo simulation of the energy deposition per disintegration. A measurement of the annual dose due to background radiation to the body was then estimated. A dose value compatible with the value reported by the United Nations Scientific Committee on the Effects of Atomic Radiation was obtained.

Determination of absorbed dose to water around a clinical HDR {sup 192}Ir source using LiF:Mg,Ti TLDs demonstrates an LET dependence of detector response

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carlsson Tedgren, Aasa; Elia, Rouba; Hedtjaern, Haakan

2012-02-15

Purpose: Experimental radiation dosimetry with thermoluminescent dosimeters (TLDs), calibrated in a {sup 60}Co or megavoltage (MV) photon beam, is recommended by AAPM TG-43U1for verification of Monte Carlo calculated absorbed doses around brachytherapy sources. However, it has been shown by Carlsson Tedgren et al.[Med. Phys. 38, 5539-5550 (2011)] that for TLDs of LiF:Mg,Ti, detector response was 4% higher in a {sup 137}Cs beam than in a {sup 60}Co one. The aim of this work was to investigate if similar over-response exists when measuring absorbed dose to water around {sup 192}Ir sources, using LiF:Mg,Ti dosimeters calibrated in a 6 MV photon beam.more » Methods: LiF dosimeters were calibrated to measure absorbed dose to water in a 6 MV photon beam and used to measure absorbed dose to water at distances of 3, 5, and 7 cm from a clinical high dose rate (HDR) {sup 192}Ir source in a polymethylmethacrylate (PMMA) phantom. Measured values were compared to values of absorbed dose to water calculated using a treatment planning system (TPS) including corrections for the difference in energy absorption properties between calibration quality and the quality in the users'{sup 192}Ir beam and for the use of a PMMA phantom instead of the water phantom underlying dose calculations in the TPS. Results: Measured absorbed doses to water around the {sup 192}Ir source were overestimated by 5% compared to those calculated by the TPS. Corresponding absorbed doses to water measured in a previous work with lithium formate electron paramagnetic resonance (EPR) dosimeters by Antonovic et al. [Med. Phys. 36, 2236-2247 (2009)], using the same irradiation setup and calibration procedure as in this work, were 2% lower than those calculated by the TPS. The results obtained in the measurements in this work and those obtained using the EPR lithium formate dosimeters were, within the expanded (k = 2) uncertainty, in agreement with the values derived by the TPS. The discrepancy between the results using LiF:Mg,Ti TLDs and the EPR lithium formate dosimeters was, however, statistically significant and in agreement with the difference in relative detector responses found for the two detector systems by Carlsson Tedgren et al. [Med. Phys. 38, 5539-5550 (2011)] and by Adolfsson et al.[Med. Phys. 37, 4946-4959 (2010)]. Conclusions: When calibrated in {sup 60}Co or MV photon beams, correction for the linear energy transfer (LET) dependence of LiF:Mg,Ti detector response will be needed as to measure absorbed doses to water in a {sup 192}Ir beam with highest accuracy. Such corrections will depend on the manufacturing process (MTS-N Poland or Harshaw TLD-100) and details of the annealing and read-out schemes used.« less

Determination of absorbed dose to water around a clinical HDR (192)Ir source using LiF:Mg,Ti TLDs demonstrates an LET dependence of detector response.

PubMed

Carlsson Tedgren, Asa; Elia, Rouba; Hedtjarn, Hakan; Olsson, Sara; Alm Carlsson, Gudrun

2012-02-01

Experimental radiation dosimetry with thermoluminescent dosimeters (TLDs), calibrated in a (60)Co or megavoltage (MV) photon beam, is recommended by AAPM TG-43U1for verification of Monte Carlo calculated absorbed doses around brachytherapy sources. However, it has been shown by Carlsson Tedgren et al. [Med. Phys. 38, 5539-5550 (2011)] that for TLDs of LiF:Mg,Ti, detector response was 4% higher in a (137)Cs beam than in a (60)Co one. The aim of this work was to investigate if similar over-response exists when measuring absorbed dose to water around (192)Ir sources, using LiF:Mg,Ti dosimeters calibrated in a 6 MV photon beam. LiF dosimeters were calibrated to measure absorbed dose to water in a 6 MV photon beam and used to measure absorbed dose to water at distances of 3, 5, and 7 cm from a clinical high dose rate (HDR) (192)Ir source in a polymethylmethacrylate (PMMA) phantom. Measured values were compared to values of absorbed dose to water calculated using a treatment planning system (TPS) including corrections for the difference in energy absorption properties between calibration quality and the quality in the users' (192)Ir beam and for the use of a PMMA phantom instead of the water phantom underlying dose calculations in the TPS. Measured absorbed doses to water around the (192)Ir source were overestimated by 5% compared to those calculated by the TPS. Corresponding absorbed doses to water measured in a previous work with lithium formate electron paramagnetic resonance (EPR) dosimeters by Antonovic et al. [Med. Phys. 36, 2236-2247 (2009)], using the same irradiation setup and calibration procedure as in this work, were 2% lower than those calculated by the TPS. The results obtained in the measurements in this work and those obtained using the EPR lithium formate dosimeters were, within the expanded (k = 2) uncertainty, in agreement with the values derived by the TPS. The discrepancy between the results using LiF:Mg,Ti TLDs and the EPR lithium formate dosimeters was, however, statistically significant and in agreement with the difference in relative detector responses found for the two detector systems by Carlsson Tedgren et al. [Med. Phys. 38, 5539-5550 (2011)] and by Adolfsson et al. [Med. Phys. 37, 4946-4959 (2010)]. When calibrated in (60)Co or MV photon beams, correction for the linear energy transfer (LET) dependence of LiF:Mg,Ti detector response will be needed as to measure absorbed doses to water in a (192)Ir beam with highest accuracy. Such corrections will depend on the manufacturing process (MTS-N Poland or Harshaw TLD-100) and details of the annealing and read-out schemes used.

Dosimetric evaluation of two treatment planning systems for high dose rate brachytherapy applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shwetha, Bondel; Ravikumar, Manickam, E-mail: drravikumarm@gmail.com; Supe, Sanjay S.

2012-04-01

Various treatment planning systems are used to design plans for the treatment of cervical cancer using high-dose-rate brachytherapy. The purpose of this study was to make a dosimetric comparison of the 2 treatment planning systems from Varian medical systems, namely ABACUS and BrachyVision. The dose distribution of Ir-192 source generated with a single dwell position was compared using ABACUS (version 3.1) and BrachyVision (version 6.5) planning systems. Ten patients with intracavitary applications were planned on both systems using orthogonal radiographs. Doses were calculated at the prescription points (point A, right and left) and reference points RU, LU, RM, LM, bladder,more » and rectum. For single dwell position, little difference was observed in the doses to points along the perpendicular bisector. The mean difference between ABACUS and BrachyVision for these points was 1.88%. The mean difference in the dose calculated toward the distal end of the cable by ABACUS and BrachyVision was 3.78%, whereas along the proximal end the difference was 19.82%. For the patient case there was approximately 2% difference between ABACUS and BrachyVision planning for dose to the prescription points. The dose difference for the reference points ranged from 0.4-1.5%. For bladder and rectum, the differences were 5.2% and 13.5%, respectively. The dose difference between the rectum points was statistically significant. There is considerable difference between the dose calculations performed by the 2 treatment planning systems. It is seen that these discrepancies are caused by the differences in the calculation methodology adopted by the 2 systems.« less

Estimation of whole-body radiation exposure from brachytherapy for oral cancer using a Monte Carlo simulation

PubMed Central

Ozaki, Y.; Kaida, A.; Miura, M.; Nakagawa, K.; Toda, K.; Yoshimura, R.; Sumi, Y.; Kurabayashi, T.

2017-01-01

Abstract Early stage oral cancer can be cured with oral brachytherapy, but whole-body radiation exposure status has not been previously studied. Recently, the International Commission on Radiological Protection Committee (ICRP) recommended the use of ICRP phantoms to estimate radiation exposure from external and internal radiation sources. In this study, we used a Monte Carlo simulation with ICRP phantoms to estimate whole-body exposure from oral brachytherapy. We used a Particle and Heavy Ion Transport code System (PHITS) to model oral brachytherapy with 192Ir hairpins and 198Au grains and to perform a Monte Carlo simulation on the ICRP adult reference computational phantoms. To confirm the simulations, we also computed local dose distributions from these small sources, and compared them with the results from Oncentra manual Low Dose Rate Treatment Planning (mLDR) software which is used in day-to-day clinical practice. We successfully obtained data on absorbed dose for each organ in males and females. Sex-averaged equivalent doses were 0.547 and 0.710 Sv with 192Ir hairpins and 198Au grains, respectively. Simulation with PHITS was reliable when compared with an alternative computational technique using mLDR software. We concluded that the absorbed dose for each organ and whole-body exposure from oral brachytherapy can be estimated with Monte Carlo simulation using PHITS on ICRP reference phantoms. Effective doses for patients with oral cancer were obtained. PMID:28339846

Improved Nitrogen Removal Effect In Continuous Flow A2/O Process Using Typical Extra Carbon Source

NASA Astrophysics Data System (ADS)

Wu, Haiyan; Gao, Junyan; Yang, Dianhai; Zhou, Qi; Cai, Bijing

2010-11-01

In order to provide a basis for optimal selection of carbon source, three typical external carbon sources (i.e. methanol, sodium acetate and leachate) were applied to examine nitrogen removal efficiency of continuous flow A2/O system with the influent from the effluent of grit chamber in the second Kunming wastewater treatment plant. The best dosage was determined, and the specific nitrogen removal rate and carbon consumption rate were calculated with regard to individual external carbon source in A2/O system. Economy and technology analysis was also conducted to select the suitable carbon source with a low operation cost. Experimental results showed that the external typical carbon source caused a remarkable enhancement of system nitrate degradation ability. In comparison with the blank test, the average TN and NH3-N removal efficiency of system with different dosing quantities of external carbon source was improved by 15.2% and 34.2%, respectively. The optimal dosage of methanol, sodium acetate and leachate was respectively up to 30 mg/L, 40 mg/L and 100 mg COD/L in terms of a high nitrogen degradation effect. The highest removal efficiency of COD, TN and NH3-N reached respectively 92.3%, 73.9% and 100% with methanol with a dosage of 30 mg/L. The kinetic analysis and calculation revealed that the greatest denitrification rate was 0.0107 mg TN/mg MLVSSṡd with sodium acetate of 60 mg/L. As to carbon consumption rate, however, the highest value occurred in the blank test with a rate of 0.1955 mg COD/mg MLVSSṡd. Also, further economic analysis proved leachate to be pragmatic external carbon source whose cost was far cheaper than methanol.

Characterization of a fiber-coupled Al2O3:C luminescence dosimetry system for online in vivo dose verification during 192Ir brachytherapy.

PubMed

Andersen, Claus E; Nielsen, Søren Kynde; Greilich, Steffen; Helt-Hansen, Jakob; Lindegaard, Jacob Christian; Tanderup, Kari

2009-03-01

A prototype of a new dose-verification system has been developed to facilitate prevention and identification of dose delivery errors in remotely afterloaded brachytherapy. The system allows for automatic online in vivo dosimetry directly in the tumor region using small passive detector probes that fit into applicators such as standard needles or catheters. The system measures the absorbed dose rate (0.1 s time resolution) and total absorbed dose on the basis of radioluminescence (RL) and optically stimulated luminescence (OSL) from aluminum oxide crystals attached to optical fiber cables (1 mm outer diameter). The system was tested in the range from 0 to 4 Gy using a solid-water phantom, a Varian GammaMed Plus 192Ir PDR afterloader, and dosimetry probes inserted into stainless-steel brachytherapy needles. The calibrated system was found to be linear in the tested dose range. The reproducibility (one standard deviation) for RL and OSL measurements was 1.3%. The measured depth-dose profiles agreed well with the theoretical expectations computed with the EGSNRC Monte Carlo code, suggesting that the energy dependence for the dosimeter probes (relative to water) is less than 6% for source-to-probe distances in the range of 2-50 mm. Under certain conditions, the RL signal could be greatly disturbed by the so-called stem signal (i.e., unwanted light generated in the fiber cable upon irradiation). The OSL signal is not subject to this source of error. The tested system appears to be adequate for in vivo brachytherapy dosimetry.

The IPEM code of practice for determination of the reference air kerma rate for HDR 192Ir brachytherapy sources based on the NPL air kerma standard

NASA Astrophysics Data System (ADS)

Bidmead, A. M.; Sander, T.; Locks, S. M.; Lee, C. D.; Aird, E. G. A.; Nutbrown, R. F.; Flynn, A.

2010-06-01

This paper contains the recommendations of the high dose rate (HDR) brachytherapy working party of the UK Institute of Physics and Engineering in Medicine (IPEM). The recommendations consist of a Code of Practice (COP) for the UK for measuring the reference air kerma rate (RAKR) of HDR 192Ir brachytherapy sources. In 2004, the National Physical Laboratory (NPL) commissioned a primary standard for the realization of RAKR of HDR 192Ir brachytherapy sources. This has meant that it is now possible to calibrate ionization chambers directly traceable to an air kerma standard using an 192Ir source (Sander and Nutbrown 2006 NPL Report DQL-RD 004 (Teddington: NPL) http://publications.npl.co.uk). In order to use the source specification in terms of either RAKR, \\dot K_R (ICRU 1985 ICRU Report No 38 (Washington, DC: ICRU); ICRU 1997 ICRU Report No 58 (Bethesda, MD: ICRU)), or air kerma strength, SK (Nath et al 1995 Med. Phys. 22 209-34), it has been necessary to develop algorithms that can calculate the dose at any point around brachytherapy sources within the patient tissues. The AAPM TG-43 protocol (Nath et al 1995 Med. Phys. 22 209-34) and the 2004 update TG-43U1 (Rivard et al 2004 Med. Phys. 31 633-74) have been developed more fully than any other protocol and are widely used in commercial treatment planning systems. Since the TG-43 formalism uses the quantity air kerma strength, whereas this COP uses RAKR, a unit conversion from RAKR to air kerma strength was included in the appendix to this COP. It is recommended that the measured RAKR determined with a calibrated well chamber traceable to the NPL 192Ir primary standard is used in the treatment planning system. The measurement uncertainty in the source calibration based on the system described in this COP has been reduced considerably compared to other methods based on interpolation techniques.

A measurement-based generalized source model for Monte Carlo dose simulations of CT scans

PubMed Central

Ming, Xin; Feng, Yuanming; Liu, Ransheng; Yang, Chengwen; Zhou, Li; Zhai, Hezheng; Deng, Jun

2018-01-01

The goal of this study is to develop a generalized source model (GSM) for accurate Monte Carlo dose simulations of CT scans based solely on the measurement data without a priori knowledge of scanner specifications. The proposed generalized source model consists of an extended circular source located at x-ray target level with its energy spectrum, source distribution and fluence distribution derived from a set of measurement data conveniently available in the clinic. Specifically, the central axis percent depth dose (PDD) curves measured in water and the cone output factors measured in air were used to derive the energy spectrum and the source distribution respectively with a Levenberg-Marquardt algorithm. The in-air film measurement of fan-beam dose profiles at fixed gantry was back-projected to generate the fluence distribution of the source model. A benchmarked Monte Carlo user code was used to simulate the dose distributions in water with the developed source model as beam input. The feasibility and accuracy of the proposed source model was tested on a GE LightSpeed and a Philips Brilliance Big Bore multi-detector CT (MDCT) scanners available in our clinic. In general, the Monte Carlo simulations of the PDDs in water and dose profiles along lateral and longitudinal directions agreed with the measurements within 4%/1mm for both CT scanners. The absolute dose comparison using two CTDI phantoms (16 cm and 32 cm in diameters) indicated a better than 5% agreement between the Monte Carlo-simulated and the ion chamber-measured doses at a variety of locations for the two scanners. Overall, this study demonstrated that a generalized source model can be constructed based only on a set of measurement data and used for accurate Monte Carlo dose simulations of patients’ CT scans, which would facilitate patient-specific CT organ dose estimation and cancer risk management in the diagnostic and therapeutic radiology. PMID:28079526

A measurement-based generalized source model for Monte Carlo dose simulations of CT scans

NASA Astrophysics Data System (ADS)

Ming, Xin; Feng, Yuanming; Liu, Ransheng; Yang, Chengwen; Zhou, Li; Zhai, Hezheng; Deng, Jun

2017-03-01

The goal of this study is to develop a generalized source model for accurate Monte Carlo dose simulations of CT scans based solely on the measurement data without a priori knowledge of scanner specifications. The proposed generalized source model consists of an extended circular source located at x-ray target level with its energy spectrum, source distribution and fluence distribution derived from a set of measurement data conveniently available in the clinic. Specifically, the central axis percent depth dose (PDD) curves measured in water and the cone output factors measured in air were used to derive the energy spectrum and the source distribution respectively with a Levenberg-Marquardt algorithm. The in-air film measurement of fan-beam dose profiles at fixed gantry was back-projected to generate the fluence distribution of the source model. A benchmarked Monte Carlo user code was used to simulate the dose distributions in water with the developed source model as beam input. The feasibility and accuracy of the proposed source model was tested on a GE LightSpeed and a Philips Brilliance Big Bore multi-detector CT (MDCT) scanners available in our clinic. In general, the Monte Carlo simulations of the PDDs in water and dose profiles along lateral and longitudinal directions agreed with the measurements within 4%/1 mm for both CT scanners. The absolute dose comparison using two CTDI phantoms (16 cm and 32 cm in diameters) indicated a better than 5% agreement between the Monte Carlo-simulated and the ion chamber-measured doses at a variety of locations for the two scanners. Overall, this study demonstrated that a generalized source model can be constructed based only on a set of measurement data and used for accurate Monte Carlo dose simulations of patients’ CT scans, which would facilitate patient-specific CT organ dose estimation and cancer risk management in the diagnostic and therapeutic radiology.

Determination of the intrinsic energy dependence of LiF:Mg,Ti thermoluminescent dosimeters for {sup 125}I and {sup 103}Pd brachytherapy sources relative to {sup 60}Co

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reed, J. L., E-mail: jlreed2@wisc.edu; Micka, J. A.; Culberson, W. S.

Purpose: To determine the intrinsic energy dependence of LiF:Mg,Ti thermoluminescent dosimeters (TLD-100) for {sup 125}I and {sup 103}Pd brachytherapy sources relative to {sup 60}Co. Methods: LiF:Mg,Ti TLDs were irradiated with low-energy brachytherapy sources and with a {sup 60}Co teletherapy source. The brachytherapy sources measured were the Best 2301 {sup 125}I seed, the OncoSeed 6711 {sup 125}I seed, and the Best 2335 {sup 103}Pd seed. The TLD light output per measured air-kerma strength was determined for the brachytherapy source irradiations, and the TLD light output per air kerma was determined for the {sup 60}Co irradiations. Monte Carlo (MC) simulations were usedmore » to calculate the dose-to-TLD rate per air-kerma strength for the brachytherapy source irradiations and the dose to TLD per air kerma for the {sup 60}Co irradiations. The measured and MC-calculated results for all irradiations were used to determine the TLD intrinsic energy dependence for {sup 125}I and {sup 103}Pd relative to {sup 60}Co. Results: The relative TLD intrinsic energy dependences (relative to {sup 60}Co) and associated uncertainties (k = 1) were determined to be 0.883 ± 1.3%, 0.870 ± 1.4%, and 0.871 ± 1.5% for the Best 2301 seed, OncoSeed 6711 seed, and Best 2335 seed, respectively. Conclusions: The intrinsic energy dependence of TLD-100 is dependent on photon energy, exhibiting changes of 13%–15% for {sup 125}I and {sup 103}Pd sources relative to {sup 60}Co. TLD measurements of absolute dose around {sup 125}I and {sup 103}Pd brachytherapy sources should explicitly account for the relative TLD intrinsic energy dependence in order to improve dosimetric accuracy.« less

High resolution ion chamber array delivery quality assurance for robotic radiosurgery: Commissioning and validation.

PubMed

Blanck, Oliver; Masi, Laura; Chan, Mark K H; Adamczyk, Sebastian; Albrecht, Christian; Damme, Marie-Christin; Loutfi-Krauss, Britta; Alraun, Manfred; Fehr, Roman; Ramm, Ulla; Siebert, Frank-Andre; Stelljes, Tenzin Sonam; Poppinga, Daniela; Poppe, Björn

2016-06-01

High precision radiosurgery demands comprehensive delivery-quality-assurance techniques. The use of a liquid-filled ion-chamber-array for robotic-radiosurgery delivery-quality-assurance was investigated and validated using several test scenarios and routine patient plans. Preliminary evaluation consisted of beam profile validation and analysis of source-detector-distance and beam-incidence-angle response dependence. The delivery-quality-assurance analysis is performed in four steps: (1) Array-to-plan registration, (2) Evaluation with standard Gamma-Index criteria (local-dose-difference⩽2%, distance-to-agreement⩽2mm, pass-rate⩾90%), (3) Dose profile alignment and dose distribution shift until maximum pass-rate is found, and (4) Final evaluation with 1mm distance-to-agreement criterion. Test scenarios consisted of intended phantom misalignments, dose miscalibrations, and undelivered Monitor Units. Preliminary method validation was performed on 55 clinical plans in five institutions. The 1000SRS profile measurements showed sufficient agreement compared with a microDiamond detector for all collimator sizes. The relative response changes can be up to 2.2% per 10cm source-detector-distance change, but remains within 1% for the clinically relevant source-detector-distance range. Planned and measured dose under different beam-incidence-angles showed deviations below 1% for angles between 0° and 80°. Small-intended errors were detected by 1mm distance-to-agreement criterion while 2mm criteria failed to reveal some of these deviations. All analyzed delivery-quality-assurance clinical patient plans were within our tight tolerance criteria. We demonstrated that a high-resolution liquid-filled ion-chamber-array can be suitable for robotic radiosurgery delivery-quality-assurance and that small errors can be detected with tight distance-to-agreement criterion. Further improvement may come from beam specific correction for incidence angle and source-detector-distance response. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Fast GPU-based Monte Carlo simulations for LDR prostate brachytherapy.

PubMed

Bonenfant, Éric; Magnoux, Vincent; Hissoiny, Sami; Ozell, Benoît; Beaulieu, Luc; Després, Philippe

2015-07-07

The aim of this study was to evaluate the potential of bGPUMCD, a Monte Carlo algorithm executed on Graphics Processing Units (GPUs), for fast dose calculations in permanent prostate implant dosimetry. It also aimed to validate a low dose rate brachytherapy source in terms of TG-43 metrics and to use this source to compute dose distributions for permanent prostate implant in very short times. The physics of bGPUMCD was reviewed and extended to include Rayleigh scattering and fluorescence from photoelectric interactions for all materials involved. The radial and anisotropy functions were obtained for the Nucletron SelectSeed in TG-43 conditions. These functions were compared to those found in the MD Anderson Imaging and Radiation Oncology Core brachytherapy source registry which are considered the TG-43 reference values. After appropriate calibration of the source, permanent prostate implant dose distributions were calculated for four patients and compared to an already validated Geant4 algorithm. The radial function calculated from bGPUMCD showed excellent agreement (differences within 1.3%) with TG-43 accepted values. The anisotropy functions at r = 1 cm and r = 4 cm were within 2% of TG-43 values for angles over 17.5°. For permanent prostate implants, Monte Carlo-based dose distributions with a statistical uncertainty of 1% or less for the target volume were obtained in 30 s or less for 1 × 1 × 1 mm(3) calculation grids. Dosimetric indices were very similar (within 2.7%) to those obtained with a validated, independent Monte Carlo code (Geant4) performing the calculations for the same cases in a much longer time (tens of minutes to more than a hour). bGPUMCD is a promising code that lets envision the use of Monte Carlo techniques in a clinical environment, with sub-minute execution times on a standard workstation. Future work will explore the use of this code with an inverse planning method to provide a complete Monte Carlo-based planning solution.

Fast GPU-based Monte Carlo simulations for LDR prostate brachytherapy

NASA Astrophysics Data System (ADS)

Bonenfant, Éric; Magnoux, Vincent; Hissoiny, Sami; Ozell, Benoît; Beaulieu, Luc; Després, Philippe

2015-07-01

The aim of this study was to evaluate the potential of bGPUMCD, a Monte Carlo algorithm executed on Graphics Processing Units (GPUs), for fast dose calculations in permanent prostate implant dosimetry. It also aimed to validate a low dose rate brachytherapy source in terms of TG-43 metrics and to use this source to compute dose distributions for permanent prostate implant in very short times. The physics of bGPUMCD was reviewed and extended to include Rayleigh scattering and fluorescence from photoelectric interactions for all materials involved. The radial and anisotropy functions were obtained for the Nucletron SelectSeed in TG-43 conditions. These functions were compared to those found in the MD Anderson Imaging and Radiation Oncology Core brachytherapy source registry which are considered the TG-43 reference values. After appropriate calibration of the source, permanent prostate implant dose distributions were calculated for four patients and compared to an already validated Geant4 algorithm. The radial function calculated from bGPUMCD showed excellent agreement (differences within 1.3%) with TG-43 accepted values. The anisotropy functions at r = 1 cm and r = 4 cm were within 2% of TG-43 values for angles over 17.5°. For permanent prostate implants, Monte Carlo-based dose distributions with a statistical uncertainty of 1% or less for the target volume were obtained in 30 s or less for 1 × 1 × 1 mm3 calculation grids. Dosimetric indices were very similar (within 2.7%) to those obtained with a validated, independent Monte Carlo code (Geant4) performing the calculations for the same cases in a much longer time (tens of minutes to more than a hour). bGPUMCD is a promising code that lets envision the use of Monte Carlo techniques in a clinical environment, with sub-minute execution times on a standard workstation. Future work will explore the use of this code with an inverse planning method to provide a complete Monte Carlo-based planning solution.

Low-dose abdominal computed tomography for detection of urinary stone disease - Impact of additional spectral shaping of the X-ray beam on image quality and dose parameters.

PubMed

Dewes, Patricia; Frellesen, Claudia; Scholtz, Jan-Erik; Fischer, Sebastian; Vogl, Thomas J; Bauer, Ralf W; Schulz, Boris

2016-06-01

To evaluate a novel tin filter-based abdominal CT protocol for urolithiasis in terms of image quality and CT dose parameters. 130 consecutive patients with suspected urolithiasis underwent non-enhanced CT with three different protocols: 48 patients (group 1) were examined at tin-filtered 150kV (150kV Sn) on a third-generation dual-source-CT, 33 patients were examined with automated kV-selection (110-140kV) based on the scout view on the same CT-device (group 2), and 49 patients were examined on a second-generation dual-source-CT (group 3) with automated kV-selection (100-140kV). Automated exposure control was active in all groups. Image quality was subjectively evaluated on a 5-point-likert-scale by two radiologists and interobserver agreement as well as signal-to-noise-ratio (SNR) was calculated. Dose-length-product (DLP) and volume CT dose index (CTDIvol) were compared. Image quality was rated in favour for the tin filter protocol with excellent interobserver agreement (ICC=0.86-0.91) and the difference reached statistical significance (p<0.001). SNR was significantly higher in group 1 and 2 compared to second-generation DSCT (p<0.001). On third-generation dual-source CT, there was no significant difference in SNR between the 150kV Sn and the automated kV selection protocol (p=0.5). The DLP of group 1 was 23% and 21% (p<0.002) lower in comparison to group 2 and 3, respectively. So was the CTDIvol of group 1 compared to group 2 (-36%) and 3 (-32%) (p<0.001). Additional shaping of a 150kV source spectrum by a tin filter substantially lowers patient exposure while improving image quality on un-enhanced abdominal computed tomography for urinary stone disease. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Shielding design of the Mayo Clinic Scottsdale cyclotron vault

NASA Astrophysics Data System (ADS)

Riper, Kenneth A. Van; Metzger, Robert L.; Nelson, Kevin

2017-09-01

Mayo Clinic Scottsdale (Scottsdale, Arizona) is building a cyclotron vault containing a cyclotron with adjacent targets and a beam line leading to an external target. The targets are irradiated by high energy (15 to 16.5 MeV) protons for the production of radioisotopes. We performed Monte Carlo radiation transport simulations to calculate the radiation dose outside of the vault during irradiation of the cyclotron and external targets. We present the Monte Carlo model including the geometry, sources, and variance reduction methods. Mesh tallies surrounding the vault show the external dose rate is within acceptable limits.

Assessment of normal tissue complications following prostate cancer irradiation: Comparison of radiation treatment modalities using NTCP models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takam, Rungdham; Bezak, Eva; Yeoh, Eric E.

2010-09-15

Purpose: Normal tissue complication probability (NTCP) of the rectum, bladder, urethra, and femoral heads following several techniques for radiation treatment of prostate cancer were evaluated applying the relative seriality and Lyman models. Methods: Model parameters from literature were used in this evaluation. The treatment techniques included external (standard fractionated, hypofractionated, and dose-escalated) three-dimensional conformal radiotherapy (3D-CRT), low-dose-rate (LDR) brachytherapy (I-125 seeds), and high-dose-rate (HDR) brachytherapy (Ir-192 source). Dose-volume histograms (DVHs) of the rectum, bladder, and urethra retrieved from corresponding treatment planning systems were converted to biological effective dose-based and equivalent dose-based DVHs, respectively, in order to account for differences inmore » radiation treatment modality and fractionation schedule. Results: Results indicated that with hypofractionated 3D-CRT (20 fractions of 2.75 Gy/fraction delivered five times/week to total dose of 55 Gy), NTCP of the rectum, bladder, and urethra were less than those for standard fractionated 3D-CRT using a four-field technique (32 fractions of 2 Gy/fraction delivered five times/week to total dose of 64 Gy) and dose-escalated 3D-CRT. Rectal and bladder NTCPs (5.2% and 6.6%, respectively) following the dose-escalated four-field 3D-CRT (2 Gy/fraction to total dose of 74 Gy) were the highest among analyzed treatment techniques. The average NTCP for the rectum and urethra were 0.6% and 24.7% for LDR-BT and 0.5% and 11.2% for HDR-BT. Conclusions: Although brachytherapy techniques resulted in delivering larger equivalent doses to normal tissues, the corresponding NTCPs were lower than those of external beam techniques other than the urethra because of much smaller volumes irradiated to higher doses. Among analyzed normal tissues, the femoral heads were found to have the lowest probability of complications as most of their volume was irradiated to lower equivalent doses compared to other tissues.« less

Low-dose 4D cardiac imaging in small animals using dual source micro-CT

NASA Astrophysics Data System (ADS)

Holbrook, M.; Clark, D. P.; Badea, C. T.

2018-01-01

Micro-CT is widely used in preclinical studies, generating substantial interest in extending its capabilities in functional imaging applications such as blood perfusion and cardiac function. However, imaging cardiac structure and function in mice is challenging due to their small size and rapid heart rate. To overcome these challenges, we propose and compare improvements on two strategies for cardiac gating in dual-source, preclinical micro-CT: fast prospective gating (PG) and uncorrelated retrospective gating (RG). These sampling strategies combined with a sophisticated iterative image reconstruction algorithm provide faster acquisitions and high image quality in low-dose 4D (i.e. 3D  +  Time) cardiac micro-CT. Fast PG is performed under continuous subject rotation which results in interleaved projection angles between cardiac phases. Thus, fast PG provides a well-sampled temporal average image for use as a prior in iterative reconstruction. Uncorrelated RG incorporates random delays during sampling to prevent correlations between heart rate and sampling rate. We have performed both simulations and animal studies to validate these new sampling protocols. Sampling times for 1000 projections using fast PG and RG were 2 and 3 min, respectively, and the total dose was 170 mGy each. Reconstructions were performed using a 4D iterative reconstruction technique based on the split Bregman method. To examine undersampling robustness, subsets of 500 and 250 projections were also used for reconstruction. Both sampling strategies in conjunction with our iterative reconstruction method are capable of resolving cardiac phases and provide high image quality. In general, for equal numbers of projections, fast PG shows fewer errors than RG and is more robust to undersampling. Our results indicate that only 1000-projection based reconstruction with fast PG satisfies a 5% error criterion in left ventricular volume estimation. These methods promise low-dose imaging with a wide range of preclinical applications in cardiac imaging.

Pre-travel advice, attitudes and hepatitis A and B vaccination rates among travellers from seven countries†

PubMed Central

Heywood, Anita E.; Nothdurft, Hans; Tessier, Dominique; Moodley, Melissa; Rombo, Lars; Marano, Cinzia; De Moerlooze, Laurence

2017-01-01

Background: Knowledge about the travel-associated risks of hepatitis A and B, and the extent of pre-travel health-advice being sought may vary between countries. Methods: An online survey was undertaken to assess the awareness, advice-seeking behaviour, rates of vaccination against hepatitis A and B and adherence rates in Australia, Finland, Germany, Norway, Sweden, the UK and Canada between August and October 2014. Individuals aged 18–65 years were screened for eligibility based on: travel to hepatitis A and B endemic countries within the past 3 years, awareness of hepatitis A, and/or combined hepatitis A&B vaccines; awareness of their self-reported vaccination status and if vaccinated, vaccination within the last 3 years. Awareness and receipt of the vaccines, sources of advice, reasons for non-vaccination, adherence to recommended doses and the value of immunization reminders were analysed. Results: Of 27 386 screened travellers, 19 817 (72%) were aware of monovalent hepatitis A or combined A&B vaccines. Of these 13 857 (70%) had sought advice from a healthcare provider (HCP) regarding combined hepatitis A&B or monovalent hepatitis A vaccination, and 9328 (67%) were vaccinated. Of 5225 individuals eligible for the main survey (recently vaccinated = 3576; unvaccinated = 1649), 27% (841/3111) and 37% (174/465) of vaccinated travellers had adhered to the 3-dose combined hepatitis A&B or 2-dose monovalent hepatitis A vaccination schedules, respectively. Of travellers partially vaccinated against combined hepatitis A&B or hepatitis A, 84% and 61%, respectively, believed that they had received the recommended number of doses. Conclusions: HCPs remain the main source of pre-travel health advice. The majority of travellers who received monovalent hepatitis A or combined hepatitis A&B vaccines did not complete the recommended course. These findings highlight the need for further training of HCPs and the provision of reminder services to improve traveller awareness and adherence to vaccination schedules. PMID:27738112

Beam related response of in vivo diode detectors for external radiotherapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baci, Syrja, E-mail: sbarci2013@gmail.com; Telhaj, Ervis; Malkaj, Partizan

2016-03-25

In Vivo Dosimetry (IVD) is a set of methods used in cancer treatment clinics to determine the real dose of radiation absorbed by target volume in a patient’s body. IVD has been widely implemented in radiotherapy treatment centers and is now recommended part of Quality Assurance program by many International health and radiation organizations. Because of cost and lack of specialized personnel, IVD has not been practiced as yet, in Albanian radiotherapy clinics. At Hygeia Hospital Tirana, patients are irradiated with high energy photons generated by Elekta Synergy Accelerators. We have recently started experimenting with the purpose of establishing anmore » IVD practice at this hospital. The first set of experiments was aimed at calibration of diodes that are going to be used for IVD. PMMA, phantoms by PTW were used to calibrate p – type Si, semiconductor diode dosimeters, made by PTW Freiburg for entrance dose. Response of the detectors is affected by energy of the beam, accumulated radiation dose, dose rate, temperature, angle against the beam axis, etc. Here we present the work done for calculating calibration factor and correction factors of source to surface distance, field size, and beam incidence for the entrance dose for both 6 MV photon beam and 18 MV photon beam. Dependence of dosimeter response was found to be more pronounced with source to surface distance as compared to other variables investigated.« less

Compact D-D Neutron Source-Driven Subcritical Multiplier and Beam-Shaping Assembly for Boron Neutron Capture Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Francesco Ganda; Jasmina Vujic; Ehud Greenspan

2010-12-01

This work assesses the feasibility of using a small, safe, and inexpensive keff 0.98 subcritical fission assembly [subcritical neutron multiplier (SCM)] to amplify the treatment neutron beam intensity attainable from a compact deuterium-deuterium (D-D) fusion neutron source delivering [approximately]1012 n/s. The objective is to reduce the treatment time for deep-seated brain tumors to [approximately]1 h. The paper describes the optimal SCM design and two optimal beam-shaping assemblies (BSAs) - one designed to maximize the dose rate and the other designed to maximize the total dose that can be delivered to a deep-seated tumor. The neutron beam intensity amplification achieved withmore » the optimized SCM and BSA results in an increase in the treatment dose rate by a factor of 18: from 0.56 Gy/h without the SCM to 10.1 Gy/h. The entire SCM is encased in an aluminum structure. The total amount of 20% enriched uranium required for the SCM is 8.5 kg, and the cost (not including fabrication) is estimated to be less than $60,000. The SCM power level is estimated at 400 W when driven by a 1012 n/s D-D neutron source. This translates into consumption of only [approximately]0.6% of the initially loaded 235U atoms during 50 years of continuous operation and implies that the SCM could operate continuously for the entire lifetime of the facility without refueling. Cooling the SCM does not pose a challenge; it may be accomplished by natural circulation as the maximum heat flux is only 0.034 W/cm2.« less

Dosimetric properties of a proton beamline dedicated to the treatment of ocular disease

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slopsema, R. L., E-mail: rslopsema@floridaproton.org; Mamalui, M.; Yeung, D.

2014-01-15

Purpose: A commercial proton eyeline has been developed to treat ocular disease. Radiotherapy of intraocular lesions (e.g., uveal melanoma, age-related macular degeneration) requires sharp dose gradients to avoid critical structures like the macula and optic disc. A high dose rate is needed to limit patient gazing times during delivery of large fractional dose. Dose delivery needs to be accurate and predictable, not in the least because current treatment planning algorithms have limited dose modeling capabilities. The purpose of this paper is to determine the dosimetric properties of a new proton eyeline. These properties are compared to those of existing systemsmore » and evaluated in the context of the specific clinical requirements of ocular treatments. Methods: The eyeline is part of a high-energy, cyclotron-based proton therapy system. The energy at the entrance of the eyeline is 105 MeV. A range modulator (RM) wheel generates the spread-out Bragg peak, while a variable range shifter system adjusts the range and spreads the beam laterally. The range can be adjusted from 0.5 up to 3.4 g/cm{sup 2}; the modulation width can be varied in steps of 0.3 g/cm{sup 2} or less. Maximum field diameter is 2.5 cm. All fields can be delivered with a dose rate of 30 Gy/min or more. The eyeline is calibrated according to the IAEA TRS-398 protocol using a cylindrical ionization chamber. Depth dose distributions and dose/MU are measured with a parallel-plate ionization chamber; lateral profiles with radiochromic film. The dose/MU is modeled as a function of range, modulation width, and instantaneous MU rate with fit parameters determined per option (RM wheel). Results: The distal fall-off of the spread-out Bragg peak is 0.3 g/cm{sup 2}, larger than for most existing systems. The lateral penumbra varies between 0.9 and 1.4 mm, except for fully modulated fields that have a larger penumbra at skin. The source-to-axis distance is found to be 169 cm. The dose/MU shows a strong dependence on range (up to 4%/mm). A linear increase in dose/MU as a function of instantaneous MU rate is observed. The dose/MU model describes the measurements with an accuracy of ±2%. Neutron dose is found to be 146 ± 102 μSv/Gy at the contralateral eye and 19 ± 13 μSv/Gy at the chest. Conclusions: Measurements show the proton eyeline meets the requirements to effectively treat ocular disease.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Slopsema, R. L., E-mail: rslopsema@floridaproton.org; Mamalui, M.; Yeung, D.

Purpose: A commercial proton eyeline has been developed to treat ocular disease. Radiotherapy of intraocular lesions (e.g., uveal melanoma, age-related macular degeneration) requires sharp dose gradients to avoid critical structures like the macula and optic disc. A high dose rate is needed to limit patient gazing times during delivery of large fractional dose. Dose delivery needs to be accurate and predictable, not in the least because current treatment planning algorithms have limited dose modeling capabilities. The purpose of this paper is to determine the dosimetric properties of a new proton eyeline. These properties are compared to those of existing systemsmore » and evaluated in the context of the specific clinical requirements of ocular treatments. Methods: The eyeline is part of a high-energy, cyclotron-based proton therapy system. The energy at the entrance of the eyeline is 105 MeV. A range modulator (RM) wheel generates the spread-out Bragg peak, while a variable range shifter system adjusts the range and spreads the beam laterally. The range can be adjusted from 0.5 up to 3.4 g/cm{sup 2}; the modulation width can be varied in steps of 0.3 g/cm{sup 2} or less. Maximum field diameter is 2.5 cm. All fields can be delivered with a dose rate of 30 Gy/min or more. The eyeline is calibrated according to the IAEA TRS-398 protocol using a cylindrical ionization chamber. Depth dose distributions and dose/MU are measured with a parallel-plate ionization chamber; lateral profiles with radiochromic film. The dose/MU is modeled as a function of range, modulation width, and instantaneous MU rate with fit parameters determined per option (RM wheel). Results: The distal fall-off of the spread-out Bragg peak is 0.3 g/cm{sup 2}, larger than for most existing systems. The lateral penumbra varies between 0.9 and 1.4 mm, except for fully modulated fields that have a larger penumbra at skin. The source-to-axis distance is found to be 169 cm. The dose/MU shows a strong dependence on range (up to 4%/mm). A linear increase in dose/MU as a function of instantaneous MU rate is observed. The dose/MU model describes the measurements with an accuracy of ±2%. Neutron dose is found to be 146 ± 102 μSv/Gy at the contralateral eye and 19 ± 13 μSv/Gy at the chest. Conclusions: Measurements show the proton eyeline meets the requirements to effectively treat ocular disease.« less

Methylene blue treatment for residual symptoms of bipolar disorder: randomised crossover study.

PubMed

Alda, Martin; McKinnon, Margaret; Blagdon, Ryan; Garnham, Julie; MacLellan, Susan; O'Donovan, Claire; Hajek, Tomas; Nair, Cynthia; Dursun, Serdar; MacQueen, Glenda

2017-01-01

Residual symptoms and cognitive impairment are among important sources of disability in patients with bipolar disorder. Methylene blue could improve such symptoms because of its potential neuroprotective effects. We conducted a double-blind crossover study of a low dose (15 mg, 'placebo') and an active dose (195 mg) of methylene blue in patients with bipolar disorder treated with lamotrigine. Thirty-seven participants were enrolled in a 6-month trial (trial registration: NCT00214877). The outcome measures included severity of depression, mania and anxiety, and cognitive functioning. The active dose of methylene blue significantly improved symptoms of depression both on the Montgomery-Åsberg Depression Rating Scale and Hamilton Rating Scale for Depression (P = 0.02 and 0.05 in last-observation-carried-forward analysis). It also reduced the symptoms of anxiety measured by the Hamilton Rating Scale for Anxiety (P = 0.02). The symptoms of mania remained low and stable throughout the study. The effects of methylene blue on cognitive symptoms were not significant. The medication was well tolerated with transient and mild side-effects. Methylene blue used as an adjunctive medication improved residual symptoms of depression and anxiety in patients with bipolar disorder. © The Royal College of Psychiatrists 2017.

Characterization of detector-systems based on CeBr3, LaBr3, SrI2 and CdZnTe for the use as dosemeters

NASA Astrophysics Data System (ADS)

Kessler, P.; Behnke, B.; Dombrowski, H.; Neumaier, S.

2017-11-01

For the upgrade of existing dosimetric early warning networks in Europe spectrometric detectors based on CeBr3, LaBr3, SrI2, and CdZnTe are investigated as possible substitutes for the current detector generation which is mainly based on gas filled detectors. The additional information on the nuclide vector which can be derived from the spectra of γ-radiation is highly useful for an appropriate response in case of a nuclear or radiological accident. The measured γ-spectra will be converted into ambient dose equivalent H* (10) using a method where the spectrum is subdivided into multiple energy bands. For each band the conversion coefficients from count rate to dose rate is determined. The derivation of these conversion coefficients is explained in this work. Both experimental and simulative approaches are investigated using quasi-mono-energetic γ-sources and synthetic spectra from Monte-Carlo simulations to determine the conversion coefficients for each detector type. Finally, precision of the obtained characterization is checked by irradiation of the detectors in different well-known photon fields with traceable dose rates.

Poster - Thur Eve - 03: LDR to HDR: RADPOS applications in brachytherapy.

PubMed

Cherpak, A J; Cygler, J E; Kertzscher, G; E, C; Perry, G

2012-07-01

The RADPOS in vivo dosimetry system combines an electromagnetic positioning sensor and either one or five MOSFET dosimeters. The feasibility of using the system for quality control has been explored for a range of radiotherapy treatment techniques including most recently transperineal interstitial permanent prostate brachytherapy and high dose rate (HDR) treatments. Dose and position information was collected by a RADPOS array detector inside a Foley catheter within patients' urethra during permanent seed implantation. Ten patients were studied, and average displacement during implantation was Δr = (1.4-5.1) mm, with movements up to 9.7 mm due to the removal of the transrectal ultrasound probe. Maximum integral dose in the prostatic urethra ranged from 110-195 Gy, and it was found that the dose can change up to 63 cGy (62.0%) depending on whether the rectal probe is in place. For HDR, a RADPOS detector was first calibrated with an Ir-192 source. A treatment was then simulated using a total of 50 dwell positions in 5 catheters in an acrylic phantom. Dwell positions ranged from 1 to 10 cm away from the RADPOS detector and dose was measured for each source position. An average calibration coefficient of 0.74±0.11 cGy/mV was calculated for the detector and the average absolute difference between measured values and expected dose was 0.7±5.4 cGy (5±20%). The demonstrated accuracy of RADPOS dose measurements along with its ability to simultaneously measure displacement makes it a powerful tool for brachytherapy treatments, where high dose gradients can present unique in vivo dosimetry challenges. © 2012 American Association of Physicists in Medicine.

Prospective Measurement of Patient Exposure to Radiation During Pediatric Ureteroscopy

PubMed Central

Kokorowski, Paul J.; Chow, Jeanne S.; Strauss, Keith; Pennison, Melanie; Routh, Jonathan C.; Nelson, Caleb P.

2013-01-01

Objective Little data have been reported regarding radiation exposure during pediatric endourologic procedures, including ureteroscopy (URS). We sought to measure radiation exposure during pediatric URS and identify opportunities for exposure reduction. Methods We prospectively observed URS procedures as part of a quality improvement initiative. Pre-operative patient characteristics, operative factors, fluoroscopy settings and radiation exposure were recorded. Our outcomes were entrance skin dose (ESD, in mGy) and midline dose (MLD, in mGy). Specific modifiable factors were identified as targets for potential quality improvement. Results Direct observation was performed on 56 consecutive URS procedures. Mean patient age was 14.8 ± 3.8 years (range 7.4 to 19.2); 9 children were under age 12 years. Mean ESD was 46.4 ± 48 mGy. Mean MLD was 6.2 ± 5.0 mGy. The most important major determinant of radiation dose was total fluoroscopy time (mean 2.68 ± 1.8 min) followed by dose rate setting, child anterior-posterior (AP) diameter, and source to skin distance (all p<0.01). The analysis of factors affecting exposure levels found that the use of ureteral access sheaths (p=0.01) and retrograde pyelography (p=0.04) were significantly associated with fluoroscopy time. We also found that dose rate settings were higher than recommended in up to 43% of cases and ideal C-arm positioning could have reduced exposure 14% (up to 49% in some cases). Conclusions Children receive biologically significant radiation doses during URS procedures. Several modifiable factors contribute to dose and could be targeted in efforts to implement dose reduction strategies. PMID:22341275

Application of the concept of biologically effective dose (BED) to patients with Vestibular Schwannomas treated by radiosurgery

PubMed Central

Millar, William T.; Lindquist, Christer; Nordström, Håkan; Lidberg, Pär; Gårding, Jonas

2013-01-01

In the application of stereotactic radiosurgery, using the Gamma Knife, there are large variations in the overall treatment time for the same prescription dose, given in a single treatment session, for different patients. This is due to not only changes in the activity of the Cobolt-60 sources, but also to variations in the number of iso-centers used, the collimator size for a particular iso-center, and the time gap between the different iso-centers. Although frequently viewed as a single dose treatment the concept of biologically effective dose (BED), incorporating concurrent fast and a slow components of repair of sublethal damage, would imply potential variations in BED because of the influence of these different variables associated with treatment. This was investigated in 26 patients, treated for Vestibular Schwannomas, using the Series B Gamma-Knife, between 1999 and 2005. The iso-center number varied between 2 and 13, and the overall treatment time from 25.4–129.58 min. The prescription doses varied from 10–14 Gy. To obtain physical dose and dose-rates from each iso-center, in a number of locations in the region of interest, a prototype version of the Leksell GammaPlan® was used. For an individual patient, BED values varied by up to 15% for a given physical iso-dose. This was due to variation in the dose prescription at different locations on that iso-dose. Between patients there was a decline in the range of BED values as the overall treatment time increased. This increased treatment time was partly a function of the slow decline in the activity of the sources with time but predominantly due to changes in the number of iso-centers used. Thus, variations in BED values did not correlate with prescription dose but was modified by the overall treatment time. PMID:29296371

Estimation of the indoor radon and the annual effective dose from granite samples

NASA Astrophysics Data System (ADS)

Sola, P.; Srinuttrakul, W.; Kewsuwan, P.

2015-05-01

Inhalation of radon and thoron daughters increases the risk of lung cancer. The main sources of indoor radon are building materials. The aim of this research is to estimate the indoor radon and the annual effective dose from the building materials. Eighteen granite samples bought from the markets in Thailand were measured using an ionization chamber (ATMOS 12 DPX) for the radon concentration in air. Radon exhalation rates were calculated from the radon concentration in chamber. The indoor radon from the granite samples ranged from 10.04 to 55.32 Bq·m-2·h-1 with an average value of 20.30 Bq·m-2·h-1 and the annual effective dose ranged from 0.25 to 1.39 mSv·y-1 with an average value of 0.48 mSv·y-1. The results showed that the annual effective doses of three granite samples were higher than the annual exposure limit for the general public (1 mSv·y-1) recommended by the International Commission on Radiological Protection (ICRP). In addition, the relationship between the colours and radon exhalation rates of granite samples was also explained.

TEDE per cumulated activity for family members exposed to adult patients treated with 131I.

PubMed

Han, Eun Young; Lee, Choonsik; Bolch, Wesley E

2013-01-01

In 1997, the United States Nuclear Regulatory Commission amended its criteria under which patients administered radioactive materials could be released from the hospital. The revised criteria ensures that the total effective dose equivalent (TEDE) to any individual exposed to the released patient will not likely exceed 5 mSv. Licensees are recommended to use one of the three options to release the patient in accordance with these regulatory requirements: administered activity, measured dose rate, or patient-specific dose calculation. The NRC's suggested calculation method is based on the assumption that the patient (source) and a family member (target) are each considered to be points in space. This point source/target assumption has been shown to be conservative in comparison to more realistic guidelines. In this present study, the effective doses to family members were calculated using a series of revised Oak Ridge National Laboratory stylised phantoms coupled with a Monte Carlo radiation transport code. A set of TEDE per cumulated activity values were calculated for three different distributions of (131)I (thyroid, abdomen and whole body), various separation distances and two exposure scenarios (face-to-face standing and side-by-side lying). The results indicate that an overestimation of TEDE per cumulated activity based on the point source/target method was >2-fold. The values for paediatric phantoms showed a strong age-dependency, which showed that dosimetry for children should be separately considered instead of using adult phantoms as a substitute. On the basis of the results of this study, a licensee may use less conservative patient-specific release criteria and provide the patient and the family members with more practical dose avoidance guidelines.

A fast and simple dose-calibrator-based quality control test for the radionuclidic purity of cyclotron-produced (99m)Tc.

PubMed

Tanguay, J; Hou, X; Esquinas, P; Vuckovic, M; Buckley, K; Schaffer, P; Bénard, F; Ruth, T J; Celler, A

2015-11-07

Cyclotron production of 99mTc through the (100)Mo(p,2n)99mTc reaction channel is actively being investigated as an alternative to reactor-based (99)Mo generation by nuclear fission of (235)U. Like most radioisotope production methods, cyclotron production of 99mTc will result in creation of unwanted impurities, including Tc and non-Tc isotopes. It is important to measure the amounts of these impurities for release of cyclotron-produced 99mTc (CPTc) for clinical use. Detection of radioactive impurities will rely on measurements of their gamma (γ) emissions. Gamma spectroscopy is not suitable for this purpose because the overwhelming presence of 99mTc and the count-rate limitations of γ spectroscopy systems preclude fast and accurate measurement of small amounts of impurities. In this article we describe a simple and fast method for measuring γ emission rates from radioactive impurities in CPTc. The proposed method is similar to that used to identify (99)Mo breakthrough in generator-produced 99mTc: one dose calibrator (DC) reading of a CPTc source placed in a lead shield is followed by a second reading of the same source in air. Our experimental and theoretical analysis show that the ratio of DC readings in lead to those in air are linearly related to γ emission rates from impurities per MBq of 99mTc over a large range of clinically-relevant production conditions. We show that estimates of the γ emission rates from Tc impurities per MBq of 99mTc can be used to estimate increases in radiation dose (relative to pure 99mTc) to patients injected with CPTc-based radiopharmaceuticals. This enables establishing dosimetry-based clinical-release criteria that can be tested using commercially-available dose calibrators. We show that our approach is highly sensitive to the presence of 93gTc, 93mTc, 94gTc, 94mTc, 95mTc, 95gTc, and 96gTc, in addition to a number of non-Tc impurities.

A fast and simple dose-calibrator-based quality control test for the radionuclidic purity of cyclotron-produced 99mTc

NASA Astrophysics Data System (ADS)

Tanguay, J.; Hou, X.; Esquinas, P.; Vuckovic, M.; Buckley, K.; Schaffer, P.; Bénard, F.; Ruth, T. J.; Celler, A.

2015-11-01

Cyclotron production of {{}99\\text{m}} Tc through the 100Mo(p,2n){{}99\\text{m}} Tc reaction channel is actively being investigated as an alternative to reactor-based 99Mo generation by nuclear fission of 235U. Like most radioisotope production methods, cyclotron production of {{}99\\text{m}} Tc will result in creation of unwanted impurities, including Tc and non-Tc isotopes. It is important to measure the amounts of these impurities for release of cyclotron-produced {{}99\\text{m}} Tc (CPTc) for clinical use. Detection of radioactive impurities will rely on measurements of their gamma (γ) emissions. Gamma spectroscopy is not suitable for this purpose because the overwhelming presence of {{}99\\text{m}} Tc and the count-rate limitations of γ spectroscopy systems preclude fast and accurate measurement of small amounts of impurities. In this article we describe a simple and fast method for measuring γ emission rates from radioactive impurities in CPTc. The proposed method is similar to that used to identify 99Mo breakthrough in generator-produced {{}99\\text{m}} Tc: one dose calibrator (DC) reading of a CPTc source placed in a lead shield is followed by a second reading of the same source in air. Our experimental and theoretical analysis show that the ratio of DC readings in lead to those in air are linearly related to γ emission rates from impurities per MBq of {{}99\\text{m}} Tc over a large range of clinically-relevant production conditions. We show that estimates of the γ emission rates from Tc impurities per MBq of {{}99\\text{m}} Tc can be used to estimate increases in radiation dose (relative to pure {{}99\\text{m}} Tc) to patients injected with CPTc-based radiopharmaceuticals. This enables establishing dosimetry-based clinical-release criteria that can be tested using commercially-available dose calibrators. We show that our approach is highly sensitive to the presence of {{}93\\text{g}} Tc, {{}93\\text{m}} Tc, {{}94\\text{g}} Tc, {{}94\\text{m}} Tc, {{}95\\text{m}} Tc, {{}95\\text{g}} Tc, and {{}96\\text{g}} Tc, in addition to a number of non-Tc impurities.

High-dose rate brachytherapy in the treatment of carcinoma of uterine cervix: twenty-year experience with cobalt after-loading system.

PubMed

Mosalaei, A; Mohammadianpanah, M; Omidvari, S; Ahmadloo, N

2006-01-01

This retrospective analysis aims to report results of patients with cancer of uterine cervix treated with external-beam radiotherapy (EBR) and high-dose rate (HDR) brachytherapy, using manual treatment planning. From 1975 to 1995, 237 patients with FIGO stages IIB-IVA and mean age of 54.31 years were treated. EBR dose to the whole pelvis was 50 Gy in 25 fractions. Brachytherapy with HDR after-loading cobalt source (Cathetron) was performed following EBR completion with a dose of 30 Gy in three weekly fractions of 10 Gy to point A. Survival, local control, and genitourinary and gastrointestinal complications were assessed. In a median follow-up of 60.2 months, the 10-year overall and disease-free survival rate was 62.4%. Local recurrence was seen in 12.2% of patients. Distant metastases to the lymph nodes, peritoneum, lung, liver, and bone occurred in 25.3% of patients. Less than 6% of patients experienced severe genitourinary and/or gastrointestinal toxicity that were relieved by surgical intervention. No treatment-related mortality was seen. This series suggests that 50 Gy to the whole pelvis together with three fractions of 10 Gy to point A with HDR brachytherapy is an effective fractionation schedule in the treatment of locally advanced cancer of cervix. To decrease the complications, newer devices and treatment planning may be beneficial.

Monte Carlo Shielding Comparative Analysis Applied to TRIGA HEU and LEU Spent Fuel Transport

NASA Astrophysics Data System (ADS)

Margeanu, C. A.; Margeanu, S.; Barbos, D.; Iorgulis, C.

2010-12-01

The paper is a comparative study of LEU and HEU fuel utilization effects for the shielding analysis during spent fuel transport. A comparison against the measured data for HEU spent fuel, available from the last stage of spent fuel repatriation fulfilled in the summer of 2008, is also presented. All geometrical and material data for the shipping cask were considered according to NAC-LWT Cask approved model. The shielding analysis estimates radiation doses to shipping cask wall surface, and in air at 1 m and 2 m, respectively, from the cask, by means of 3D Monte Carlo MORSE-SGC code. Before loading into the shipping cask, TRIGA spent fuel source terms and spent fuel parameters have been obtained by means of ORIGEN-S code. Both codes are included in ORNL's SCALE 5 programs package. The actinides contribution to total fuel radioactivity is very low in HEU spent fuel case, becoming 10 times greater in LEU spent fuel case. Dose rates for both HEU and LEU fuel contents are below regulatory limits, LEU spent fuel photon dose rates being greater than HEU ones. Comparison between HEU spent fuel theoretical and measured dose rates in selected measuring points shows a good agreement, calculated values being greater than the measured ones both to cask wall surface (about 34% relative difference) and in air at 1 m distance from cask surface (about 15% relative difference).

Evaluation of a lithium formate EPR dosimetry system for dose measurements around {sup 192}Ir brachytherapy sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antonovic, Laura; Gustafsson, Haakan; Alm Carlsson, Gudrun

2009-06-15

A dosimetry system using lithium formate monohydrate (HCO{sub 2}Li{center_dot}H{sub 2}O) as detector material and electron paramagnetic resonance (EPR) spectroscopy for readout has been used to measure absorbed dose distributions around clinical {sup 192}Ir sources. Cylindrical tablets with diameter of 4.5 mm, height of 4.8 mm, and density of 1.26 g/cm{sup 3} were manufactured. Homogeneity test and calibration of the dosimeters were performed in a 6 MV photon beam. {sup 192}Ir irradiations were performed in a PMMA phantom using two different source models, the GammaMed Plus HDR and the microSelectron PDR-v1 model. Measured absorbed doses to water in the PMMA phantommore » were converted to the corresponding absorbed doses to water in water phantoms of dimensions used by the treatment planning systems (TPSs) using correction factors explicitly derived for this experiment. Experimentally determined absorbed doses agreed with the absorbed doses to water calculated by the TPS to within {+-}2.9%. Relative standard uncertainties in the experimentally determined absorbed doses were estimated to be within the range of 1.7%-1.3% depending on the radial distance from the source, the type of source (HDR or PDR), and the particular absorbed doses used. This work shows that a lithium formate dosimetry system is well suited for measurements of absorbed dose to water around clinical HDR and PDR {sup 192}Ir sources. Being less energy dependent than the commonly used thermoluminescent lithium fluoride (LiF) dosimeters, lithium formate monohydrate dosimeters are well suited to measure absorbed doses in situations where the energy dependence cannot easily be accounted for such as in multiple-source irradiations to verify treatment plans. Their wide dynamic range and linear dose response over the dose interval of 0.2-1000 Gy make them suitable for measurements on sources of the strengths used in clinical applications. The dosimeter size needs, however, to be reduced for application to single-source dosimetry.« less

Typical doses and dose rates in studies pertinent to radiation risk inference at low doses and low dose rates

PubMed Central

Rühm, Werner; Azizova, Tamara; Bouffler, Simon; Cullings, Harry M; Grosche, Bernd; Little, Mark P; Shore, Roy S; Walsh, Linda; Woloschak, Gayle E

2018-01-01

Abstract In order to quantify radiation risks at exposure scenarios relevant for radiation protection, often extrapolation of data obtained at high doses and high dose rates down to low doses and low dose rates is needed. Task Group TG91 on ‘Radiation Risk Inference at Low-dose and Low-dose Rate Exposure for Radiological Protection Purposes’ of the International Commission on Radiological Protection is currently reviewing the relevant cellular, animal and human studies that could be used for that purpose. This paper provides an overview of dose rates and doses typically used or present in those studies, and compares them with doses and dose rates typical of those received by the A-bomb survivors in Japan. PMID:29432579

SU-F-T-336: A Quick Auto-Planning (QAP) Method for Patient Intensity Modulated Radiotherapy (IMRT)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, J; Zhang, Z; Wang, J

2016-06-15

Purpose: The aim of this study is to develop a quick auto-planning system that permits fast patient IMRT planning with conformal dose to the target without manual field alignment and time-consuming dose distribution optimization. Methods: The planning target volume (PTV) of the source and the target patient were projected to the iso-center plane in certain beameye- view directions to derive the 2D projected shapes. Assuming the target interior was isotropic for each beam direction boundary analysis under polar coordinate was performed to map the source shape boundary to the target shape boundary to derive the source-to-target shape mapping function. Themore » derived shape mapping function was used to morph the source beam aperture to the target beam aperture over all segments in each beam direction. The target beam weights were re-calculated to deliver the same dose to the reference point (iso-center) as the source beam did in the source plan. The approach was tested on two rectum patients (one source patient and one target patient). Results: The IMRT planning time by QAP was 5 seconds on a laptop computer. The dose volume histograms and the dose distribution showed the target patient had the similar PTV dose coverage and OAR dose sparing with the source patient. Conclusion: The QAP system can instantly and automatically finish the IMRT planning without dose optimization.« less

Detailed source term estimation of the atmospheric release for the Fukushima Daiichi Nuclear Power Station accident by coupling simulations of an atmospheric dispersion model with an improved deposition scheme and oceanic dispersion model

NASA Astrophysics Data System (ADS)

Katata, G.; Chino, M.; Kobayashi, T.; Terada, H.; Ota, M.; Nagai, H.; Kajino, M.; Draxler, R.; Hort, M. C.; Malo, A.; Torii, T.; Sanada, Y.

2015-01-01

Temporal variations in the amount of radionuclides released into the atmosphere during the Fukushima Daiichi Nuclear Power Station (FNPS1) accident and their atmospheric and marine dispersion are essential to evaluate the environmental impacts and resultant radiological doses to the public. In this paper, we estimate the detailed atmospheric releases during the accident using a reverse estimation method which calculates the release rates of radionuclides by comparing measurements of air concentration of a radionuclide or its dose rate in the environment with the ones calculated by atmospheric and oceanic transport, dispersion and deposition models. The atmospheric and oceanic models used are WSPEEDI-II (Worldwide version of System for Prediction of Environmental Emergency Dose Information) and SEA-GEARN-FDM (Finite difference oceanic dispersion model), both developed by the authors. A sophisticated deposition scheme, which deals with dry and fog-water depositions, cloud condensation nuclei (CCN) activation, and subsequent wet scavenging due to mixed-phase cloud microphysics (in-cloud scavenging) for radioactive iodine gas (I2 and CH3I) and other particles (CsI, Cs, and Te), was incorporated into WSPEEDI-II to improve the surface deposition calculations. The results revealed that the major releases of radionuclides due to the FNPS1 accident occurred in the following periods during March 2011: the afternoon of 12 March due to the wet venting and hydrogen explosion at Unit 1, midnight of 14 March when the SRV (safety relief valve) was opened three times at Unit 2, the morning and night of 15 March, and the morning of 16 March. According to the simulation results, the highest radioactive contamination areas around FNPS1 were created from 15 to 16 March by complicated interactions among rainfall, plume movements, and the temporal variation of release rates. The simulation by WSPEEDI-II using the new source term reproduced the local and regional patterns of cumulative surface deposition of total 131I and 137Cs and air dose rate obtained by airborne surveys. The new source term was also tested using three atmospheric dispersion models (Modèle Lagrangien de Dispersion de Particules d'ordre zéro: MLDP0, Hybrid Single Particle Lagrangian Integrated Trajectory Model: HYSPLIT, and Met Office's Numerical Atmospheric-dispersion Modelling Environment: NAME) for regional and global calculations, and the calculated results showed good agreement with observed air concentration and surface deposition of 137Cs in eastern Japan.

Commissioning a CT-compatible LDR tandem and ovoid applicator using Monte Carlo calculation and 3D dosimetry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Adamson, Justus; Newton, Joseph; Yang Yun

2012-07-15

Purpose: To determine the geometric and dose attenuation characteristics of a new commercially available CT-compatible LDR tandem and ovoid (T and O) applicator using Monte Carlo calculation and 3D dosimetry. Methods: For geometric characterization, we quantified physical dimensions and investigated a systematic difference found to exist between nominal ovoid angle and the angle at which the afterloading buckets fall within the ovoid. For dosimetric characterization, we determined source attenuation through asymmetric gold shielding in the buckets using Monte Carlo simulations and 3D dosimetry. Monte Carlo code MCNP5 was used to simulate 1.5 Multiplication-Sign 10{sup 9} photon histories from a {supmore » 137}Cs source placed in the bucket to achieve statistical uncertainty of 1% at a 6 cm distance. For 3D dosimetry, the distribution about an unshielded source was first measured to evaluate the system for {sup 137}Cs, after which the distribution was measured about sources placed in each bucket. Cylindrical PRESAGE{sup Registered-Sign} dosimeters (9.5 cm diameter, 9.2 cm height) with a central channel bored for source placement were supplied by Heuris Inc. The dosimeters were scanned with the Duke Large field of view Optical CT-Scanner before and after delivering a nominal dose at 1 cm of 5-8 Gy. During irradiation the dosimeter was placed in a water phantom to provide backscatter. Optical CT scan time lasted 15 min during which 720 projections were acquired at 0.5 Degree-Sign increments, and a 3D distribution was reconstructed with a (0.05 cm){sup 3} isotropic voxel size. The distributions about the buckets were used to calculate a 3D distribution of transmission rate through the bucket, which was applied to a clinical CT-based T and O implant plan. Results: The systematic difference in bucket angle relative to the nominal ovoid angle (105 Degree-Sign ) was 3.1 Degree-Sign -4.7 Degree-Sign . A systematic difference in bucket angle of 1 Degree-Sign , 5 Degree-Sign , and 10 Degree-Sign caused a 1%{+-} 0.1%, 1.7%{+-} 0.4%, and 2.6%{+-} 0.7% increase in rectal dose, respectively, with smaller effect to dose to Point A, bladder, sigmoid, and bowel. For 3D dosimetry, 90.6% of voxels had a 3D {gamma}-index (criteria = 0.1 cm, 3% local signal) below 1.0 when comparing measured and expected dose about the unshielded source. Dose transmission through the gold shielding at a radial distance of 1 cm was 85.9%{+-} 0.2%, 83.4%{+-} 0.7%, and 82.5%{+-} 2.2% for Monte Carlo, and measurement for left and right buckets, respectively. Dose transmission was lowest at oblique angles from the bucket with a minimum of 56.7%{+-} 0.8%, 65.6%{+-} 1.7%, and 57.5%{+-} 1.6%, respectively. For a clinical T and O plan, attenuation from the buckets leads to a decrease in average Point A dose of {approx}3.2% and decrease in D{sub 2cc} to bladder, rectum, bowel, and sigmoid of 5%, 18%, 6%, and 12%, respectively. Conclusions: Differences between dummy and afterloading bucket position in the ovoids is minor compared to effects from asymmetric ovoid shielding, for which rectal dose is most affected. 3D dosimetry can fulfill a novel role in verifying Monte Carlo calculations of complex dose distributions as are common about brachytherapy sources and applicators.« less

Commissioning a CT-compatible LDR tandem and ovoid applicator using Monte Carlo calculation and 3D dosimetry.

PubMed

Adamson, Justus; Newton, Joseph; Yang, Yun; Steffey, Beverly; Cai, Jing; Adamovics, John; Oldham, Mark; Chino, Junzo; Craciunescu, Oana

2012-07-01

To determine the geometric and dose attenuation characteristics of a new commercially available CT-compatible LDR tandem and ovoid (T&O) applicator using Monte Carlo calculation and 3D dosimetry. For geometric characterization, we quantified physical dimensions and investigated a systematic difference found to exist between nominal ovoid angle and the angle at which the afterloading buckets fall within the ovoid. For dosimetric characterization, we determined source attenuation through asymmetric gold shielding in the buckets using Monte Carlo simulations and 3D dosimetry. Monte Carlo code MCNP5 was used to simulate 1.5 × 10(9) photon histories from a (137)Cs source placed in the bucket to achieve statistical uncertainty of 1% at a 6 cm distance. For 3D dosimetry, the distribution about an unshielded source was first measured to evaluate the system for (137)Cs, after which the distribution was measured about sources placed in each bucket. Cylindrical PRESAGE(®) dosimeters (9.5 cm diameter, 9.2 cm height) with a central channel bored for source placement were supplied by Heuris Inc. The dosimeters were scanned with the Duke Large field of view Optical CT-Scanner before and after delivering a nominal dose at 1 cm of 5-8 Gy. During irradiation the dosimeter was placed in a water phantom to provide backscatter. Optical CT scan time lasted 15 min during which 720 projections were acquired at 0.5° increments, and a 3D distribution was reconstructed with a (0.05 cm)(3) isotropic voxel size. The distributions about the buckets were used to calculate a 3D distribution of transmission rate through the bucket, which was applied to a clinical CT-based T&O implant plan. The systematic difference in bucket angle relative to the nominal ovoid angle (105°) was 3.1°-4.7°. A systematic difference in bucket angle of 1°, 5°, and 10° caused a 1% ± 0.1%, 1.7% ± 0.4%, and 2.6% ± 0.7% increase in rectal dose, respectively, with smaller effect to dose to Point A, bladder, sigmoid, and bowel. For 3D dosimetry, 90.6% of voxels had a 3D γ-index (criteria = 0.1 cm, 3% local signal) below 1.0 when comparing measured and expected dose about the unshielded source. Dose transmission through the gold shielding at a radial distance of 1 cm was 85.9% ± 0.2%, 83.4% ± 0.7%, and 82.5% ± 2.2% for Monte Carlo, and measurement for left and right buckets, respectively. Dose transmission was lowest at oblique angles from the bucket with a minimum of 56.7% ± 0.8%, 65.6% ± 1.7%, and 57.5% ± 1.6%, respectively. For a clinical T&O plan, attenuation from the buckets leads to a decrease in average Point A dose of ∼3.2% and decrease in D(2cc) to bladder, rectum, bowel, and sigmoid of 5%, 18%, 6%, and 12%, respectively. Differences between dummy and afterloading bucket position in the ovoids is minor compared to effects from asymmetric ovoid shielding, for which rectal dose is most affected. 3D dosimetry can fulfill a novel role in verifying Monte Carlo calculations of complex dose distributions as are common about brachytherapy sources and applicators.

SU-F-T-49: Dosimetry Parameters and TPS Commissioning for the CivaSheet Directional Pd-103 Brachytherapy Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rivard, MJ

2016-06-15

Purpose: The CivaSheet is a new LDR Pd-103 brachytherapy device offering directional-radiation for preferentially irradiating malignancies with healthy-tissue sparing. Observations are presented on dosimetric characterization, TPS commissioning, and evaluation of the dosesuperposition- principle for summing individual elements comprising a planar CivaSheet Methods: The CivaSheet comprises individual sources (CivaDots, 0.05cm thick and 0.25cm diam.) inside a flexible bioabsorbable substrate with a 0.8cm center-to-center rectangular array. All non-radioactive components were measured to ensure accuracy of manufacturer-provided dimensional information. The Pd spatial distribution was gleaned from radioactive and inert samples, then modeled with the MCNP6 radiation-transport-code. A 6×6 array CivaSheet was modeled tomore » evaluate the dose superposition principle for treatment planning. Air-kerma-strength was estimated using the NIST WAFAC geometry. Absorbed dose was estimated in water with polar sampling covering 0.05≤r≤15cm in 0.05cm increments and 0°≤θ≤180° in 1° increments. These data were entered into VariSeed9.0 and tested for the dose-superposition-principle. Results: The dose-rate-constant was 0.579 cGy/h/U with g(r) determined along the rotational-axis of symmetry (0°) instead of 90°. gP(r) values at 0.1, 0.5, 2, 5, and 10cm were 1.884, 1.344, 0.558, 0.088, and 0.0046. F(r,θ) decreased between 0° and 180° by factors of 270, 23, and 5.1 at 0.1, 1, and 10cm. The highest dose-gradient was at 92°, changing by a factor of 3 within 1° due to Au-foil shielding. TPS commissioning from 0.1≤r≤11cm and 0°≤θ≤180° demonstrated 2% reproducibility of input data except at the high-dose-gradient where interpolations caused 3% differences. Dose superposition of CivaDots replicated a multi-source CivaSheet array within 2% except where another CivaDot was present. Following implantation, the device is not perfectly planar. TPS accuracy utilizing the dose-superposition-principle through geometric repositioning of CivaDots supersedes TPS limitations of intersource shielding effects Conclusion: Dosimetric characterization, source commissioning, and evaluation of the dose-superposition-principle with VariSeed9.0 permits treatment planning for the CivaSheet brachytherapy device. Research supported in part by CivaTech Oncology, Inc.« less

Error Analysis of non-TLD HDR Brachytherapy Dosimetric Techniques

NASA Astrophysics Data System (ADS)

Amoush, Ahmad

The American Association of Physicists in Medicine Task Group Report43 (AAPM-TG43) and its updated version TG-43U1 rely on the LiF TLD detector to determine the experimental absolute dose rate for brachytherapy. The recommended uncertainty estimates associated with TLD experimental dosimetry include 5% for statistical errors (Type A) and 7% for systematic errors (Type B). TG-43U1 protocol does not include recommendation for other experimental dosimetric techniques to calculate the absolute dose for brachytherapy. This research used two independent experimental methods and Monte Carlo simulations to investigate and analyze uncertainties and errors associated with absolute dosimetry of HDR brachytherapy for a Tandem applicator. An A16 MicroChamber* and one dose MOSFET detectors† were selected to meet the TG-43U1 recommendations for experimental dosimetry. Statistical and systematic uncertainty analyses associated with each experimental technique were analyzed quantitatively using MCNPX 2.6‡ to evaluate source positional error, Tandem positional error, the source spectrum, phantom size effect, reproducibility, temperature and pressure effects, volume averaging, stem and wall effects, and Tandem effect. Absolute dose calculations for clinical use are based on Treatment Planning System (TPS) with no corrections for the above uncertainties. Absolute dose and uncertainties along the transverse plane were predicted for the A16 microchamber. The generated overall uncertainties are 22%, 17%, 15%, 15%, 16%, 17%, and 19% at 1cm, 2cm, 3cm, 4cm, and 5cm, respectively. Predicting the dose beyond 5cm is complicated due to low signal-to-noise ratio, cable effect, and stem effect for the A16 microchamber. Since dose beyond 5cm adds no clinical information, it has been ignored in this study. The absolute dose was predicted for the MOSFET detector from 1cm to 7cm along the transverse plane. The generated overall uncertainties are 23%, 11%, 8%, 7%, 7%, 9%, and 8% at 1cm, 2cm, 3cm, and 4cm, 5cm, 6cm, and 7cm, respectively. The Nucletron Freiburg flap applicator is used with the Nucletron remote afterloader HDR machine to deliver dose to surface cancers. Dosimetric data for the Nucletron 192Ir source were generated using Monte Carlo simulation and compared with the published data. Two dimensional dosimetric data were calculated at two source positions; at the center of the sphere of the applicator and between two adjacent spheres. Unlike the TPS dose algorithm, The Monte Carlo code developed for this research accounts for the applicator material, secondary electrons and delta particles, and the air gap between the skin and the applicator. *Standard Imaging, Inc., Middleton, Wisconsin USA † OneDose MOSFET, Sicel Technologies, Morrisville NC ‡ Los Alamos National Laboratory, NM USA

Radon and thoron inhalation doses in dwellings with earthen architecture: Comparison of measurement methods.

PubMed

Meisenberg, Oliver; Mishra, Rosaline; Joshi, Manish; Gierl, Stefanie; Rout, Rajeswari; Guo, Lu; Agarwal, Tarun; Kanse, Sandeep; Irlinger, Josef; Sapra, Balvinder K; Tschiersch, Jochen

2017-02-01

The radioactive noble gas radon ( 222 Rn) and its decay products have been considered a health risk in the indoor environment for many years because of their contribution to the radiation dose of the lungs. The radioisotope thoron ( 220 Rn) and its decay products came into focus of being a health risk only recently. The reason for this is its short half-life, so only building material can become a significant source for indoor thoron. In this study, dwellings with earthen architecture were investigated with different independent measurement techniques in order to determine appropriate methods for reliable dose assessment of the dwellers. While for radon dose assessment, radon gas measurement and the assumption of a common indoor equilibrium factor often are sufficient, thoron gas has proven to be an unreliable surrogate for a direct measurement of thoron decay products. Active/time-resolved but also passive/integrating measurements of the total concentration of thoron decay products demonstrated being precise and efficient methods for determining the exposure and inhalation dose from thoron and its decay products. Exhalation rate measurements are a useful method for a rough dose estimate only if the exhalation rate is homogeneous throughout the house. Before the construction of a building in-vitro exhalation rate measurements on the building material can yield information about the exposure that is to be expected. Determining the unattached fraction of radon decay products and even more of thoron decay products leads to only a slightly better precision; this confirms the relative unimportance of the unattached thoron decay products due to their low concentration. The results of this study thereby give advice on the proper measurement method in similar exposure situations. Copyright © 2017 Elsevier B.V. All rights reserved.

Monte Carlo dose calculations of beta-emitting sources for intravascular brachytherapy: a comparison between EGS4, EGSnrc, and MCNP.

PubMed

Wang, R; Li, X A

2001-02-01

The dose parameters for the beta-particle emitting 90Sr/90Y source for intravascular brachytherapy (IVBT) have been calculated by different investigators. At a distant distance from the source, noticeable differences are seen in these parameters calculated using different Monte Carlo codes. The purpose of this work is to quantify as well as to understand these differences. We have compared a series of calculations using an EGS4, an EGSnrc, and the MCNP Monte Carlo codes. Data calculated and compared include the depth dose curve for a broad parallel beam of electrons, and radial dose distributions for point electron sources (monoenergetic or polyenergetic) and for a real 90Sr/90Y source. For the 90Sr/90Y source, the doses at the reference position (2 mm radial distance) calculated by the three code agree within 2%. However, the differences between the dose calculated by the three codes can be over 20% in the radial distance range interested in IVBT. The difference increases with radial distance from source, and reaches 30% at the tail of dose curve. These differences may be partially attributed to the different multiple scattering theories and Monte Carlo models for electron transport adopted in these three codes. Doses calculated by the EGSnrc code are more accurate than those by the EGS4. The two calculations agree within 5% for radial distance <6 mm.

The small-animal radiation research platform (SARRP): dosimetry of a focused lens system.

PubMed

Deng, Hua; Kennedy, Christopher W; Armour, Elwood; Tryggestad, Erik; Ford, Eric; McNutt, Todd; Jiang, Licai; Wong, John

2007-05-21

A small animal radiation platform equipped with on-board cone-beam CT and conformal irradiation capabilities is being constructed for translational research. To achieve highly localized dose delivery, an x-ray lens is used to focus the broad beam from a 225 kVp x-ray tube down to a beam with a full width half maximum (FWHM) of approximately 1.5 mm in the energy range 40-80 keV. Here, we report on the dosimetric characteristics of the focused beam from the x-ray lens subsystem for high-resolution dose delivery. Using the metric of the average dose within a 1.5 mm diameter area, the dose rates at a source-to-surface distance (SSD) of 34 cm are 259 and 172 cGy min(-1) at 6 mm and 2 cm depths, respectively, with an estimated uncertainty of +/-5%. The per cent depth dose is approximately 56% at 2 cm depth for a beam at 34 cm SSD.

Conditioning Procedure for Spent Cs-137 Sealed Sources in Egypt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mohamed, Y.T.; Hasan, M.A.; Lasheen, Y.F.

2006-07-01

It is the duty of the Hot Laboratories and Waste Management Center, Egyptian Atomic Energy Authority to mange the radioactive waste generated from any user for radioactive materials in Egypt. The most hazardous or dangerous radioactive waste we collect is spent radioactive sealed sources that have to be managed safely to protect human, workers and environment from any undue burden for radiation. Through the Integrated Management Program Of Radioactive Sealed Sources In Egypt, IMPRSS all spent Cs-137 sources with low activity will be retrievable conditioned in 200 L drum with special lead shield to keep the surface dose rate lowermore » than 200 merm/h according to US regulations and IAEA guidelines. Using this procedure the EAEA will condition about 243 sources in 9 drums. (authors)« less

Implementation and application of an interactive user-friendly validation software for RADIANCE

NASA Astrophysics Data System (ADS)

Sundaram, Anand; Boonn, William W.; Kim, Woojin; Cook, Tessa S.

2012-02-01

RADIANCE extracts CT dose parameters from dose sheets using optical character recognition and stores the data in a relational database. To facilitate validation of RADIANCE's performance, a simple user interface was initially implemented and about 300 records were evaluated. Here, we extend this interface to achieve a wider variety of functions and perform a larger-scale validation. The validator uses some data from the RADIANCE database to prepopulate quality-testing fields, such as correspondence between calculated and reported total dose-length product. The interface also displays relevant parameters from the DICOM headers. A total of 5,098 dose sheets were used to test the performance accuracy of RADIANCE in dose data extraction. Several search criteria were implemented. All records were searchable by accession number, study date, or dose parameters beyond chosen thresholds. Validated records were searchable according to additional criteria from validation inputs. An error rate of 0.303% was demonstrated in the validation. Dose monitoring is increasingly important and RADIANCE provides an open-source solution with a high level of accuracy. The RADIANCE validator has been updated to enable users to test the integrity of their installation and verify that their dose monitoring is accurate and effective.

[A Quality Assurance (QA) System with a Web Camera for High-dose-rate Brachytherapy].

PubMed

Hirose, Asako; Ueda, Yoshihiro; Oohira, Shingo; Isono, Masaru; Tsujii, Katsutomo; Inui, Shouki; Masaoka, Akira; Taniguchi, Makoto; Miyazaki, Masayoshi; Teshima, Teruki

2016-03-01

The quality assurance (QA) system that simultaneously quantifies the position and duration of an (192)Ir source (dwell position and time) was developed and the performance of this system was evaluated in high-dose-rate brachytherapy. This QA system has two functions to verify and quantify dwell position and time by using a web camera. The web camera records 30 images per second in a range from 1,425 mm to 1,505 mm. A user verifies the source position from the web camera at real time. The source position and duration were quantified with the movie using in-house software which was applied with a template-matching technique. This QA system allowed verification of the absolute position in real time and quantification of dwell position and time simultaneously. It was evident from the verification of the system that the mean of step size errors was 0.31±0.1 mm and that of dwell time errors 0.1±0.0 s. Absolute position errors can be determined with an accuracy of 1.0 mm at all dwell points in three step sizes and dwell time errors with an accuracy of 0.1% in more than 10.0 s of the planned time. This system is to provide quick verification and quantification of the dwell position and time with high accuracy at various dwell positions without depending on the step size.

Dose rate mapping of VMAT treatments

NASA Astrophysics Data System (ADS)

Podesta, Mark; Antoniu Popescu, I.; Verhaegen, Frank

2016-06-01

Human tissues exhibit a varying response to radiation dose depending on the dose rate and fractionation scheme used. Dose rate effects have been reported for different radiations, and tissue types. The literature indicates that there is not a significant difference in response for low-LET radiation when using dose rates between 1 Gy min-1 and 12 Gy min-1 but lower dose rates have an observable sparing effect on tissues and a differential effect between tissues. In intensity-modulated radiotherapy such as volumetric modulated arc therapy (VMAT) the dose can be delivered with a wide range of dose rates. In this work we developed a method based on time-resolved Monte Carlo simulations to quantify the dose rate frequency distribution for clinical VMAT treatments for three cancer sites, head and neck, lung, and pelvis within both planning target volumes (PTV) and normal tissues. The results show a wide range of dose rates are used to deliver dose in VMAT and up to 75% of the PTV can have its dose delivered with dose rates  <1 Gy min-1. Pelvic plans on average have a lower mean dose rate within the PTV than lung or head and neck plans but a comparable mean dose rate within the organs at risk. Two VMAT plans that fulfil the same dose objectives and constraints may be delivered with different dose rate distributions, particularly when comparing single arcs to multiple arc plans. It is concluded that for dynamic plans, the dose rate range used varies to a larger degree than previously assumed. The effect of the dose rate range in VMAT on clinical outcome is unknown.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Volotskova, O; Xu, A; Jozsef, G

Purpose: To investigate the response and dose rate dependence of a scintillation detector over a wide energy range. Methods: The energy dependence of W1 scintillation detector was tested with: 1) 50–225 keV beams generated by an animal irradiator, 2) a Leksell Gamma Knife Perfexion Co-60 source, 3) 6MV, 6FFF, 10FFF and 15MV photon beams, and 4) 6–20MeV electron beams from a linac. Calibrated linac beams were used to deliver 100 cGy to the detector at dmax in water under reference conditions. The gamma-knife measurement was performed in solid water (100 cGy with 16mm collimator). The low energy beams were calibratedmore » with an ion chamber in air (TG-61), and the scintillation detector was placed at the same location as the ionization chamber during calibration. For the linac photon and electron beams, dose rate dependence was tested for 100–2400 and 100–800 MU/min. Results: The scintillation detector demonstrated strong energy dependence in the range of 50–225keV. The measured values were lower than the delivered dose and increased as the energy increased. Therapeutic photon beams showed energy independence with variations less than 1%. Therapeutic electron beams displayed the same sensitivity of ∼2–3% at their corresponding dmax depths. The change in dose-rate of photon and electron beams within the therapeutic energy range did not affect detector output (<0.5%). Measurements acquired with the gamma knife showed that the output data agreed with the delivered dose up to 3%. Conclusion: W1 scintillation detector output has a strong energy dependence in the diagnostic and orthovoltage energy range. Therapeutic photon beams exhibited energy independence with no observable dose-rate dependence. This study may aid in the implementation of a scintillation detector in QA programs by providing energy calibration factors.« less

Probability Distribution of Dose and Dose-Rate Effectiveness Factor for use in Estimating Risks of Solid Cancers From Exposure to Low-Let Radiation.

PubMed

Kocher, David C; Apostoaei, A Iulian; Hoffman, F Owen; Trabalka, John R

2018-06-01

This paper presents an analysis to develop a subjective state-of-knowledge probability distribution of a dose and dose-rate effectiveness factor for use in estimating risks of solid cancers from exposure to low linear energy transfer radiation (photons or electrons) whenever linear dose responses from acute and chronic exposure are assumed. A dose and dose-rate effectiveness factor represents an assumption that the risk of a solid cancer per Gy at low acute doses or low dose rates of low linear energy transfer radiation, RL, differs from the risk per Gy at higher acute doses, RH; RL is estimated as RH divided by a dose and dose-rate effectiveness factor, where RH is estimated from analyses of dose responses in Japanese atomic-bomb survivors. A probability distribution to represent uncertainty in a dose and dose-rate effectiveness factor for solid cancers was developed from analyses of epidemiologic data on risks of incidence or mortality from all solid cancers as a group or all cancers excluding leukemias, including (1) analyses of possible nonlinearities in dose responses in atomic-bomb survivors, which give estimates of a low-dose effectiveness factor, and (2) comparisons of risks in radiation workers or members of the public from chronic exposure to low linear energy transfer radiation at low dose rates with risks in atomic-bomb survivors, which give estimates of a dose-rate effectiveness factor. Probability distributions of uncertain low-dose effectiveness factors and dose-rate effectiveness factors for solid cancer incidence and mortality were combined using assumptions about the relative weight that should be assigned to each estimate to represent its relevance to estimation of a dose and dose-rate effectiveness factor. The probability distribution of a dose and dose-rate effectiveness factor for solid cancers developed in this study has a median (50th percentile) and 90% subjective confidence interval of 1.3 (0.47, 3.6). The harmonic mean is 1.1, which implies that the arithmetic mean of an uncertain estimate of the risk of a solid cancer per Gy at low acute doses or low dose rates of low linear energy transfer radiation is only about 10% less than the mean risk per Gy at higher acute doses. Data were also evaluated to define a low acute dose or low dose rate of low linear energy transfer radiation, i.e., a dose or dose rate below which a dose and dose-rate effectiveness factor should be applied in estimating risks of solid cancers.

Probabilistic dose assessment of normal operations and accident conditions for an assured isolation facility in Texas

NASA Astrophysics Data System (ADS)

Arno, Matthew Gordon

Texas is investigating building a long-term waste storage facility, also known as an Assured Isolation Facility. This is an above-ground low-level radioactive waste storage facility that is actively maintained and from which waste may be retrieved. A preliminary, scoping-level analysis has been extended to consider more complex scenarios of radiation streaming and skyshine by using the computer code Monte Carlo N-Particle (MCNP) to model the facility in greater detail. Accidental release scenarios have been studied in more depth to better assess the potential dose to off-site individuals. Using bounding source term assumptions, the projected radiation doses and dose rates are estimated to exceed applicable limits by an order of magnitude. By altering the facility design to fill in the hollow cores of the prefabricated concrete slabs used in the roof over the "high-gamma rooms," where the waste with the highest concentration of gamma emitting radioactive material is stored, dose rates outside the facility decrease by an order of magnitude. With the modified design, the annual dose at the site fenceline is estimated at 86 mrem, below the 100 mrem annual limit for exposure of the public. Within the site perimeter, the dose rates are lowered sufficiently such that it is not necessary to categorize many workers and contractor personnel as radiation workers, saving on costs as well as being advisable under ALARA principles. A detailed analysis of bounding accidents incorporating information on the local meteorological conditions indicate that the maximum committed effective dose equivalent from the passage of a plume of material released in an accident at any of the cities near the facility is 59 :rem in the city of Eunice, NM based on the combined day and night meteorological conditions. Using the daytime meteorological conditions, the maximum dose at any city is 7 :rem, also in the city of Eunice. The maximum dose at the site boundary was determined to be 230 mrem using the combined day and night meteorological conditions and 33 mrem using the daytime conditions.