Cosmic ray LET spectra and doses on board Cosmos-2044 biosatellite

NASA Technical Reports Server (NTRS)

Dudkin, V. E.; Kovalev, E. E.; Potapov, Y. V.; Benton, E. V.; Frank, A. L.; Benton, E. R.; Watts, J. W. Jr; Parnell, T. A.; Schopper, E.; Baican, B.;

Approximate distribution of dose among foetal organs for radioiodine uptake via placenta transfer

NASA Astrophysics Data System (ADS)

Millard, R. K.; Saunders, M.; Palmer, A. M.; Preece, A. W.

2001-11-01

Absorbed radiation doses to internal foetal organs were calculated according to the medical internal radiation dose (MIRD) technique in this study. Anthropomorphic phantoms of the pregnant female as in MIRDOSE3 enabled estimation of absorbed dose to the whole foetus at two stages of gestation. Some foetal organ self-doses could have been estimated by invoking simple spherical models for thyroid, liver, etc, but we investigated the use of the MIRDOSE3 new-born phantom as a surrogate for the stage 3 foetus, scaled to be compatible with total foetal body mean absorbed dose/cumulated activity. We illustrate the method for obtaining approximate dose distribution in the foetus near term following intake of 1 MBq of 123I, 124I, 125I or 131I as sodium iodide by the mother using in vivo biodistribution data examples from a good model of placenta transfer. Doses to the foetal thyroid of up to 1.85 Gy MBq-1 were predicted from the 131I uptake data. Activity in the foetal thyroid was the largest contributor to absorbed dose in the foetal body, brain, heart and thymus. Average total doses to the whole foetus ranged from 0.16 to 1.2 mGy MBq-1 for stages 1 and 3 of pregnancy using the MIRDOSE3 program, and were considerably higher than those predicted from the maternal contributions alone. Doses to the foetal thymus and stomach were similar, around 2-3 mGy MBq-1. Some foetal organ doses from the radioiodides were ten times higher than to the corresponding organs of the mother, and up to 100 times higher to the thyroid. The fraction of activity uptakes in foetal organs were distributed similarly to the maternal ones.

Cosmic ray LET spectra and doses on board Cosmos-2044 biosatellite

NASA Technical Reports Server (NTRS)

Watts, J. W., Jr.; Parnell, T. A.; Dudkin, V. E.; Kovalev, E. E.; Potapov, Yu. V.; Benton, E. V.; Frank, A. L.; Benton, E. R.; Beaujean, R.; Heilmann, C.

1995-01-01

Results of the experiments on board Cosmos-2044 (Biosatellite 9) are presented. Various nuclear track detectors (NTD) (dielectric, AgCl-based, nuclear emulsions) were used to obtain the Linear Energy Transfer (LET) spectra inside and outside the satellite. The spectra from the different NTDs have proved to be in general agreement. The results of LET spectra calculations using two different models are also presented. The resultant LET distributions are used to calculate the absorbed and equivalent doses and the orbit-averaged quality factors (QF) of the cosmic rays (CR). Absorbed dose rates inside (approximately 20 g cm (exp -2) shielding) and outside (1 g cm(exp -2) the spacecraft, omitting electrons, were found to be 4.8 and 8.6 mrad d (exp -1), respectively, while the corresponding equivalent doses were 8.8 and 19.7 mrem d(exp -1). The effects of the flight parameters on the total fluence of, and on the dose from the CR particles are analyzed. Integral dose distributions of the detected particles are also determined. The LET values which separate absorbed and equivalent doses into 50% intervals are estimated. The CR-39 dielectric NTD is shown to detect 20-30% of the absorbed dose and 60-70% of the equivalent dose in the Cosmos-2044 orbit. The influence of solar activity phase on the magnitude of CR flux is discussed.

Boron Neutron Capture Therapy (BNCT) Dose Calculation using Geometrical Factors Spherical Interface for Glioblastoma Multiforme

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

Zasneda, Sabriani; Widita, Rena

2010-06-22

Boron Neutron Capture Therapy (BNCT) is a cancer therapy by utilizing thermal neutron to produce alpha particles and lithium nuclei. The superiority of BNCT is that the radiation effects could be limited only for the tumor cells. BNCT radiation dose depends on the distribution of boron in the tumor. Absorbed dose to the cells from the reaction 10B (n, {alpha}) 7Li was calculated near interface medium containing boron and boron-free region. The method considers the contribution of the alpha particle and recoiled lithium particle to the absorbed dose and the variation of Linear Energy Transfer (LET) charged particles energy. Geometricalmore » factor data of boron distribution for the spherical surface is used to calculate the energy absorbed in the tumor cells, brain and scalp for case Glioblastoma Multiforme. The result shows that the optimal dose in tumor is obtained for boron concentrations of 22.1 mg {sup 10}B/g blood.« less

A bone marrow toxicity model for 223Ra alpha-emitter radiopharmaceutical therapy

NASA Astrophysics Data System (ADS)

Hobbs, Robert F.; Song, Hong; Watchman, Christopher J.; Bolch, Wesley E.; Aksnes, Anne-Kirsti; Ramdahl, Thomas; Flux, Glenn D.; Sgouros, George

2012-05-01

Ra-223, an α-particle emitting bone-seeking radionuclide, has recently been used in clinical trials for osseous metastases of prostate cancer. We investigated the relationship between absorbed fraction-based red marrow dosimetry and cell level-dosimetry using a model that accounts for the expected localization of this agent relative to marrow cavity architecture. We show that cell level-based dosimetry is essential to understanding potential marrow toxicity. The GEANT4 software package was used to create simple spheres representing marrow cavities. Ra-223 was positioned on the trabecular bone surface or in the endosteal layer and simulated for decay, along with the descendants. The interior of the sphere was divided into cell-size voxels and the energy was collected in each voxel and interpreted as dose cell histograms. The average absorbed dose values and absorbed fractions were also calculated in order to compare those results with previously published values. The absorbed dose was predominantly deposited near the trabecular surface. The dose cell histogram results were used to plot the percentage of cells that received a potentially toxic absorbed dose (2 or 4 Gy) as a function of the average absorbed dose over the marrow cavity. The results show (1) a heterogeneous distribution of cellular absorbed dose, strongly dependent on the position of the cell within the marrow cavity; and (2) that increasing the average marrow cavity absorbed dose, or equivalently, increasing the administered activity resulted in only a small increase in potential marrow toxicity (i.e. the number of cells receiving more than 4 or 2 Gy), for a range of average marrow cavity absorbed doses from 1 to 20 Gy. The results from the trabecular model differ markedly from a standard absorbed fraction method while presenting comparable average dose values. These suggest that increasing the amount of radioactivity may not substantially increase the risk of toxicity, a result unavailable to the absorbed fraction method of dose calculation.

Red Marrow-Absorbed Dose for Non-Hodgkin Lymphoma Patients Treated with 177Lu-Lilotomab Satetraxetan, a Novel Anti-CD37 Antibody-Radionuclide Conjugate.

PubMed

Blakkisrud, Johan; Løndalen, Ayca; Dahle, Jostein; Turner, Simon; Holte, Harald; Kolstad, Arne; Stokke, Caroline

2017-01-01

Red marrow (RM) is often the primary organ at risk in radioimmunotherapy; irradiation of marrow may induce short- and long-term hematologic toxicity. 177 Lu-lilotomab satetraxetan is a novel anti-CD37 antibody-radionuclide conjugate currently in phase 1/2a. Two predosing regimens have been investigated, one with 40 mg of unlabeled lilotomab antibody (arm 1) and one without (arm 2). The aim of this work was to compare RM-absorbed doses for the two arms and to correlate absorbed doses with hematologic toxicity. Eight patients with relapsed CD37+ indolent B-cell non-Hodgkin lymphoma were included for RM dosimetry. Hybrid SPECT and CT images were used to estimate the activity concentration in the RM of L2-L4. Pharmacokinetic parameters were calculated after measurement of the 177 Lu-lilotomab satetraxetan concentration in blood samples. Adverse events were graded according to the Common Terminology Criteria for Adverse Events, version 4.0. The mean absorbed doses to RM were 0.9 mGy/MBq for arm 1 (lilotomab+) and 1.5 mGy/MBq for arm 2 (lilotomab-). There was a statistically significant difference between arms 1 and 2 (Student t test, P = 0.02). Total RM-absorbed doses ranged from 67 to 127 cGy in arm 1 and from 158 to 207 cGy in arm 2. For blood, the area under the curve was higher with lilotomab predosing than without (P = 0.001), whereas the volume of distribution and the clearance of 177 Lu-lilotomab satetraxetan was significantly lower (P = 0.01 and P = 0.03, respectively). Patients with grade 3/4 thrombocytopenia had received significantly higher radiation doses to RM than patients with grade 1/2 thrombocytopenia (P = 0.02). A surrogate, non-imaging-based, method underestimated the RM dose and did not show any correlation with toxicity. Predosing with lilotomab reduces the RM-absorbed dose for 177 Lu-lilotomab satetraxetan patients. The decrease in RM dose could be explained by the lower volume of distribution. Hematologic toxicity was more severe for patients receiving higher absorbed radiation doses, indicating that adverse events possibly can be predicted by the calculation of absorbed dose to RM from SPECT/CT images. © 2017 by the Society of Nuclear Medicine and Molecular Imaging.

Depth distribution of absorbed dose on the external surface of Cosmos 1887 biosatellite

NASA Technical Reports Server (NTRS)

Watts, J. W., Jr.; Parnell, T. A.; Akatov, Yu. A.; Dudkin, V. E.; Kovalev, E. E.; Benton, E. V.; Frank, A. L.

1995-01-01

Significant absorbed dose levels exceeding 1.0 Gy day(exp -1) have been measured on the external surface of the Cosmos 1887 biosatellite as functions of depth in stacks of thin thermoluminescent detectors (TLD's) made in U.S.S.R. and U.S.A. The dose was found to decrease rapidly with increasing absorber thickness, thereby indicating the presence of intensive fluxes of low-energy particles. Comparison between the U.S.S.R. and U.S.A. results and calculations based on the Vette Model environment are in satisfactory agreement. The major contribution to the dose under thin shielding thickness is shown to be from electrons. The fraction of the dose due to protons and heavier charged particles increases with shielding thickness.

Depth distribution of absorbed dose on the external surface of Cosmos 1887 biosatellite

NASA Technical Reports Server (NTRS)

Dudkin, V. E.; Kovalev, E. E.; Benton, E. V.; Frank, A. L.; Watts, J. W. Jr; Parnell, T. A.

1990-01-01

Significant absorbed dose levels exceeding 1.0 Gy day-1 have been measured on the external surface of the Cosmos 1887 biosatellite as functions of depth in stacks of thin thermoluminescent detectors (TLDs) of U.S.S.R. and U.S.A. manufacture. The dose was found to decrease rapidly with increasing absorber thickness, thereby indicating the presence of intensive fluxes of low-energy particles. Comparison between the U.S.S.R. and U.S.A. results and calculations based on the Vette Model environment are in satisfactory agreement. The major contribution to the dose under thin shielding thickness is shown to be from electrons. The fraction of the dose due to protons and heavier charged particles increases with shielding thickness.

Study of Fricke-gel dosimeter calibration for attaining precise measurements of the absorbed dose

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

Liosi, Giulia Maria; Benedini, Sara; Giacobbo, Francesca

2015-07-01

A method has been studied for attaining, with good precision, absolute measurements of the spatial distribution of the absorbed dose by means of the Fricke gelatin Xylenol Orange dosimetric system. With this aim, the dose response to subsequent irradiations was analyzed. In fact, the proposed modality is based on a pre-irradiation of each single dosimeter in a uniform field with a known dose, in order to extrapolate a calibration image for a subsequent non-uniform irradiation with an un-known dose to be measured. (authors)

Measurement of absorbed dose during the phantom torso experiment on the International Space Station

NASA Astrophysics Data System (ADS)

Semones, E.; Gibbons, F.; Golightly, M.; Weyland, M.; Johnson, A.; Smith, G.; Shelfer, T.; Zapp, N.

The Phantom Torso Experiment (PTE) was flown on the International Space Station (ISS) during Increment 2 (April-August 2001). The experiment was located in the US Lab module Human Research Facility (HRF) rack. The objective of the passive dosimetry portion of the experiment was to measure spatial distributions of absorbed dose in the 34, 1 inch sections of a modified RandoTM phantom. In each section of the phantom, thermoluminescent detectors (TLDs) were placed at various locations (depths) to provide the spatial measurement. TLDs were also located at several radiosensitive organ locations (brain, thyroid, heart/lung, stomach and colon) and two locations on the surface (skin). Active silicon detectors were also placed at these organ locations to provide time resolved results of the absorbed dose rates. Using these detectors, it is possible to separate the trapped and galactic cosmic ray components of the absorbed dose. The TLD results of the spatial and organ dose measurements will be presented and comparisons of the TLD and silicon detector organ absorbed doses will be made.

A mathematical model for calculation of 90Sr absorbed dose in dental tissues: elaboration and comparison to EPR measurements.

PubMed

Shishkina, E A; Lyubashevskii, N M; Tolstykh, E I; Ignatiev, E A; Betenekova, T A; Nikiforov, S V

2001-09-01

A mathematical model for calculation of the 90Sr absorbed doses in dental tissues is presented. The results of the Monte-Carlo calculations are compared to the data obtained by EPR measurements of dental tissues. Radiometric measurements of the 90Sr concentrations. TLD and EPR dosimetry investigations were performed in animal (dog) study. The importance of the irregular 90Sr distribution in the dentine for absorbed dose formation has been shown. The dominant dose formation factors (main source-tissues) were identified for the crown dentine and enamel. The model has shown agreement with experimental data which allows to determine further directions of the human tooth model development.

Space radiation absorbed dose distribution in a human phantom

NASA Technical Reports Server (NTRS)

Badhwar, G. D.; Atwell, W.; Badavi, F. F.; Yang, T. C.; Cleghorn, T. F.

2002-01-01

The radiation risk to astronauts has always been based on measurements using passive thermoluminescent dosimeters (TLDs). The skin dose is converted to dose equivalent using an average radiation quality factor based on model calculations. The radiological risk estimates, however, are based on organ and tissue doses. This paper describes results from the first space flight (STS-91, 51.65 degrees inclination and approximately 380 km altitude) of a fully instrumented Alderson Rando phantom torso (with head) to relate the skin dose to organ doses. Spatial distributions of absorbed dose in 34 1-inch-thick sections measured using TLDs are described. There is about a 30% change in dose as one moves from the front to the back of the phantom body. Small active dosimeters were developed specifically to provide time-resolved measurements of absorbed dose rates and quality factors at five organ locations (brain, thyroid, heart/lung, stomach and colon) inside the phantom. Using these dosimeters, it was possible to separate the trapped-proton and the galactic cosmic radiation components of the doses. A tissue-equivalent proportional counter (TEPC) and a charged-particle directional spectrometer (CPDS) were flown next to the phantom torso to provide data on the incident internal radiation environment. Accurate models of the shielding distributions at the site of the TEPC, the CPDS and a scalable Computerized Anatomical Male (CAM) model of the phantom torso were developed. These measurements provided a comprehensive data set to map the dose distribution inside a human phantom, and to assess the accuracy and validity of radiation transport models throughout the human body. The results show that for the conditions in the International Space Station (ISS) orbit during periods near the solar minimum, the ratio of the blood-forming organ dose rate to the skin absorbed dose rate is about 80%, and the ratio of the dose equivalents is almost one. The results show that the GCR model dose-rate predictions are 20% lower than the observations. Assuming that the trapped-belt models lead to a correct orbit-averaged energy spectrum, the measurements of dose rates inside the phantom cannot be fully understood. Passive measurements using 6Li- and 7Li-based detectors on the astronauts and inside the brain and thyroid of the phantom show the presence of a significant contribution due to thermal neutrons, an area requiring additional study.

The absorbed dose to blood from blood-borne activity

NASA Astrophysics Data System (ADS)

Hänscheid, H.; Fernández, M.; Lassmann, M.

2015-01-01

The radiation absorbed dose to blood and organs from activity in the blood is relevant for nuclear medicine dosimetry and for research in biodosimetry. The present study provides coefficients for the average absorbed dose rates to the blood from blood-borne activity for radionuclides frequently used in targeted radiotherapy and in PET diagnostics. The results were deduced from published data for vessel radius-dependent dose rate coefficients and reasonable assumptions on the blood-volume distribution as a function of the vessel radius. Different parts of the circulatory system were analyzed separately. Vessel size information for heart chambers, aorta, vena cava, pulmonary artery, and capillaries was taken from published results of morphometric measurements. The remaining blood not contained in the mentioned vessels was assumed to reside in fractal-like vascular trees, the smallest branches of which are the arterioles or venules. The applied vessel size distribution is consistent with recommendations of the ICRP on the blood-volume distribution in the human. The resulting average absorbed dose rates to the blood per nuclear disintegration per milliliter (ml) of blood are (in 10-11 Gy·s-1·Bq-1·ml) Y-90: 5.58, I-131: 2.49, Lu-177: 1.72, Sm-153: 2.97, Tc-99m: 0.366, C-11: 4.56, F-18: 3.61, Ga-68: 5.94, I-124: 2.55. Photon radiation contributes 1.1-1.2·10-11 Gy·s-1·Bq-1·ml to the total dose rate for positron emitters but significantly less for the other nuclides. Blood self-absorption of the energy emitted by ß-particles in the whole blood ranges from 37% for Y-90 to 80% for Tc-99m. The correspondent values in vascular trees, which are important for the absorbed dose to organs, range from 30% for Y-90 to 82% for Tc-99m.

Comparison of microdosimetry-based absorbed doses to control tumours and clinically obtained tumour absorbed doses in treatments with ²²³Ra.

PubMed

Minguez Gabina, Pablo; Roeske, John C; Mínguez, Ricardo; Gomez de Iturriaga, Alfonso; Rodeño, Emilia

2018-06-20

We performed Monte Carlo simulations in order to determine by means of microdosimetry calculations the average number of hits to the cell nucleus required to reach a tumour control probability (TCP) of 0.9, 〈n_0.9 〉, for the source geometry of a nucleus embedded in a homogeneous distribution of ²²³Ra atoms. From the results obtained and following the MIRD methodology, we determined the values of lesion absorbed doses needed to reach a TCP of 0.9, D_0.9, for different values of mass density, cell radiosensitivity, nucleus radius and lesion volume. The greatest variation of those absorbed doses occurred with cell radiosensitivity and no dependence was found on mass density. The source geometry used was chosen because we aimed to compare the values of D_0.9 with the lesion absorbed doses obtained from image-based macrodosimetry in treatments of metastatic castration-resistant prostate cancer with ²²³Ra which were obtained assuming a homogeneous distribution of ²²³Ra atoms within the lesion. In a comparison with a study including 29 lesions, results showed that even for the case of the most radiosensitive cells simulated, 45% of the lesions treated following a schedule of two cycles of 110 kBq/kg body mass would receive absorbed doses below the values of D_0.9 determined in this study. © 2018 Institute of Physics and Engineering in Medicine.

[The use of polymer gel dosimetry to measure dose distribution around metallic implants].

PubMed

Nagahata, Tomomasa; Yamaguchi, Hajime; Monzen, Hajime; Nishimura, Yasumasa

2014-10-01

A semi-solid polymer dosimetry system using agar was developed to measure the dose distribution close to metallic implants. Dosimetry of heterogeneous fields where electron density markedly varies is often problematic. This prompted us to develop a polymer gel dosimetry technique using agar to measure the dose distribution near substance boundaries. Varying the concentration of an oxygen scavenger (tetra-hydroxymethyl phosphonium chloride) showed the absorbed dose and transverse relaxation rate of the magnetic resonance signal to be linear between 3 and 12 Gy. Although a change in the dosimeter due to oxidization was observed in room air after 24 hours, no such effects were observed in the first 4 hours. The dose distribution around the metal implants was measured using agar dosimetry. The metals tested were a lead rod, a titanium hip joint, and a metallic stent. A maximum 30% dose increase was observed near the lead rod, but only a 3% increase in the absorbed dose was noted near the surface of the titanium hip joint and metallic stent. Semi-solid polymer dosimetry using agar thus appears to be a useful method for dosimetry around metallic substances.

SU-F-207-01: Comparison of Beam Characteristics and Organ Dose From Four Commercial Multidetector Computed Tomography Scanners

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

Ohno, T; Araki, F

2015-06-15

Purpose: To compare dosimetric properties and patient organ doses from four commercial multidetector CT (MDCT) using Monte Carlo (MC) simulation based on the absorbed dose measured using a Farmer chamber and cylindrical water phantoms according to AAPM TG-111. Methods: Four commercial MDCT were modeled using the GMctdospp (IMPS, Germany) based on the EGSnrc user code. The incident photon spectrum and bowtie filter for MC simulations were determined so that calculated values of aluminum half-value layer (Al-HVL) and off-center ratio (OCR) profile in air agreed with measured values. The MC dose was calibrated from absorbed dose measurements using a Farmer chambermore » and cylindrical water phantoms. The dose distributions of head, chest, and abdominal scan were calculated using patient CT images and mean organ doses were evaluated from dose volume histograms. Results: The HVLs at 120 kVp of Brilliance, LightSpeed, Aquilion, and SOMATOM were 9.1, 7.5, 7.2, and 8.7 mm, respectively. The calculated Al-HVLs agreed with measurements within 0.3%. The calculated and measured OCR profiles agreed within 5%. For adult head scans, mean doses for eye lens from Brilliance, LightSpeed, Aquilion, and SOMATOM were 21.7, 38.5, 47.2 and 28.4 mGy, respectively. For chest scans, mean doses for lung from Brilliance, LightSpeed, Aquilion, and SOMATOM were 21.1, 26.1, 35.3 and 24.0 mGy, respectively. For adult abdominal scans, the mean doses for liver from Brilliance, LightSpeed, Aquilion, and SOMATOM were 16.5, 21.3, 22.7, and 18.0 mGy, respectively. The absorbed doses increased with decreasing Al-HVL. The organ doses from Aquilion were two greater than those from Brilliance in head scan. Conclusion: MC dose distributions based on absorbed dose measurement in cylindrical water phantom are useful to evaluate individual patient organ doses.« less

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

Calculation of absorbed dose and biological effectiveness from photonuclear reactions in a bremsstrahlung beam of end point 50 MeV.

PubMed

Gudowska, I; Brahme, A; Andreo, P; Gudowski, W; Kierkegaard, J

1999-09-01

The absorbed dose due to photonuclear reactions in soft tissue, lung, breast, adipose tissue and cortical bone has been evaluated for a scanned bremsstrahlung beam of end point 50 MeV from a racetrack accelerator. The Monte Carlo code MCNP4B was used to determine the photon source spectrum from the bremsstrahlung target and to simulate the transport of photons through the treatment head and the patient. Photonuclear particle production in tissue was calculated numerically using the energy distributions of photons derived from the Monte Carlo simulations. The transport of photoneutrons in the patient and the photoneutron absorbed dose to tissue were determined using MCNP4B; the absorbed dose due to charged photonuclear particles was calculated numerically assuming total energy absorption in tissue voxels of 1 cm3. The photonuclear absorbed dose to soft tissue, lung, breast and adipose tissue is about (0.11-0.12)+/-0.05% of the maximum photon dose at a depth of 5.5 cm. The absorbed dose to cortical bone is about 45% larger than that to soft tissue. If the contributions from all photoparticles (n, p, 3He and 4He particles and recoils of the residual nuclei) produced in the soft tissue and the accelerator, and from positron radiation and gammas due to induced radioactivity and excited states of the nuclei, are taken into account the total photonuclear absorbed dose delivered to soft tissue is about 0.15+/-0.08% of the maximum photon dose. It has been estimated that the RBE of the photon beam of 50 MV acceleration potential is approximately 2% higher than that of conventional 60Co radiation.

Primary and secondary particle contributions to the depth dose distribution in a phantom shielded from solar flare and Van Allen protons

NASA Technical Reports Server (NTRS)

Santoro, R. T.; Claiborne, H. C.; Alsmiller, R. G., Jr.

1972-01-01

Calculations have been made using the nucleon-meson transport code NMTC to estimate the absorbed dose and dose equivalent distributions in astronauts inside space vehicles bombarded by solar flare and Van Allen protons. A spherical shell shield of specific radius and thickness with a 30-cm-diam. tissue ball at the geometric center was used to simulate the spacecraft-astronaut configuration. The absorbed dose and the dose equivalent from primary protons, secondary protons, heavy nuclei, charged pions, muons, photons, and positrons and electrons are given as a function of depth in the tissue phantom. Results are given for solar flare protons with a characteristic rigidity of 100 MV and for Van Allen protons in a 240-nautical-mile circular orbit at 30 degree inclination angle incident on both 20-g/sq cm-thick aluminum and polyethylene spherical shell shields.

Measurement of the secondary neutron dose distribution from the LET spectrum of recoils using the CR-39 plastic nuclear track detector in 10 MV X-ray medical radiation fields

NASA Astrophysics Data System (ADS)

Fujibuchi, Toshioh; Kodaira, Satoshi; Sawaguchi, Fumiya; Abe, Yasuyuki; Obara, Satoshi; Yamaguchi, Masae; Kawashima, Hajime; Kitamura, Hisashi; Kurano, Mieko; Uchihori, Yukio; Yasuda, Nakahiro; Koguchi, Yasuhiro; Nakajima, Masaru; Kitamura, Nozomi; Sato, Tomoharu

2015-04-01

We measured the recoil charged particles from secondary neutrons produced by the photonuclear reaction in a water phantom from a 10-MV photon beam from medical linacs. The absorbed dose and the dose equivalent were evaluated from the linear energy transfer (LET) spectrum of recoils using the CR-39 plastic nuclear track detector (PNTD) based on well-established methods in the field of space radiation dosimetry. The contributions and spatial distributions of these in the phantom on nominal photon exposures were verified as the secondary neutron dose and neutron dose equivalent. The neutron dose equivalent normalized to the photon-absorbed dose was 0.261 mSv/100 MU at source to chamber distance 90 cm. The dose equivalent at the surface gave the highest value, and was attenuated to less than 10% at 5 cm from the surface. The dose contribution of the high LET component of ⩾100 keV/μm increased with the depth in water, resulting in an increase of the quality factor. The CR-39 PNTD is a powerful tool that can be used to systematically measure secondary neutron dose distributions in a water phantom from an in-field to out-of-field high-intensity photon beam.

3D dosimetry estimation for selective internal radiation therapy (SIRT) using SPECT/CT images: a phantom study

NASA Astrophysics Data System (ADS)

Debebe, Senait A.; Franquiz, Juan; McGoron, Anthony J.

2015-03-01

Selective Internal Radiation Therapy (SIRT) is a common way to treat liver cancer that cannot be treated surgically. SIRT involves administration of Yttrium - 90 (90Y) microspheres via the hepatic artery after a diagnostic procedure using 99mTechnetium (Tc)-macroaggregated albumin (MAA) to detect extrahepatic shunting to the lung or the gastrointestinal tract. Accurate quantification of radionuclide administered to patients and radiation dose absorbed by different organs is of importance in SIRT. Accurate dosimetry for SIRT allows optimization of dose delivery to the target tumor and may allow for the ability to assess the efficacy of the treatment. In this study, we proposed a method that can efficiently estimate radiation absorbed dose from 90Y bremsstrahlung SPECT/CT images of liver and the surrounding organs. Bremsstrahlung radiation from 90Y was simulated using the Compton window of 99mTc (78keV at 57%). 99mTc images acquired at the photopeak energy window were used as a standard to examine the accuracy of dosimetry prediction by the simulated bremsstrahlung images. A Liqui-Phil abdominal phantom with liver, stomach and two tumor inserts was imaged using a Philips SPECT/CT scanner. The Dose Point Kernel convolution method was used to find the radiation absorbed dose at a voxel level for a three dimensional dose distribution. This method will allow for a complete estimate of the distribution of radiation absorbed dose by tumors, liver, stomach and other surrounding organs at the voxel level. The method provides a quantitative predictive method for SIRT treatment outcome and administered dose response for patients who undergo the treatment.

Radiation dosimetry in cell biology: comparison of calculated and measured absorbed dose for a range of culture vessels and clinical beam qualities.

PubMed

Claridge Mackonis, Elizabeth; Hammond, Lauren; Esteves, Ana I S; Suchowerska, Natalka

2018-02-01

Cell culture studies are frequently used to evaluate the effects of cancer treatments such as radiotherapy, hormone therapy, chemotherapy, nanoparticle enhancement, and to determine any synergies between the treatments. To achieve valid results, the absorbed dose of each therapy needs to be well known and controlled. In this study, we aim to determine the uncertainty associated with radiation exposure in different experimental conditions. We have performed an in-depth evaluation of the absorbed dose and dose distribution that would be delivered to a cell sample when cultivated in a number of the more popular designs of culture vessels. We focus on exposure to two beam types: a kilovoltage x-ray beam and a megavoltage photon beam, both of which are routinely used to treat cancer patients in the clinical environment. Our results identify large variations of up to 16% in the absorbed dose across multi-well culture plates, which if ignored in radiobiological experiments, have the potential to lead to erroneous conclusions.

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.

Lithium formate EPR dosimetry for verifications of planned dose distributions prior to intensity-modulated radiation therapy.

PubMed

Gustafsson, H; Lund, E; Olsson, S

2008-09-07

The objective of the present investigation was to evaluate lithium formate electron paramagnetic resonance (EPR) dosimetry for measurement of dose distributions in phantoms prior to intensity-modulated radiation therapy (IMRT). Lithium formate monohydrate tablets were carefully prepared, and blind tests were performed in clinically relevant situations in order to determine the precision and accuracy of the method. Further experiments confirmed that within the accuracy of the current method, the dosimeter response was independent of beam energies and dose rates used for IMRT treatments. The method was applied to IMRT treatment plans, and the dose determinations were compared to ionization chamber measurements. The experiments showed that absorbed doses above 3 Gy could be measured with an uncertainty of less than 2.5% of the dose (coverage factor kappa = 1.96). Measurement time was about 15 min using a well-calibrated dosimeter batch. The conclusion drawn from the investigation was that lithium formate EPR dosimetry is a promising new tool for absorbed dose measurements in external beam radiation therapy, especially for doses above 3 Gy.

Lithium formate EPR dosimetry for verifications of planned dose distributions prior to intensity-modulated radiation therapy

NASA Astrophysics Data System (ADS)

Gustafsson, H.; Lund, E.; Olsson, S.

2008-09-01

The objective of the present investigation was to evaluate lithium formate electron paramagnetic resonance (EPR) dosimetry for measurement of dose distributions in phantoms prior to intensity-modulated radiation therapy (IMRT). Lithium formate monohydrate tablets were carefully prepared, and blind tests were performed in clinically relevant situations in order to determine the precision and accuracy of the method. Further experiments confirmed that within the accuracy of the current method, the dosimeter response was independent of beam energies and dose rates used for IMRT treatments. The method was applied to IMRT treatment plans, and the dose determinations were compared to ionization chamber measurements. The experiments showed that absorbed doses above 3 Gy could be measured with an uncertainty of less than 2.5% of the dose (coverage factor k = 1.96). Measurement time was about 15 min using a well-calibrated dosimeter batch. The conclusion drawn from the investigation was that lithium formate EPR dosimetry is a promising new tool for absorbed dose measurements in external beam radiation therapy, especially for doses above 3 Gy.

The intratumoral distribution of radiolabeled 177Lu-BR96 monoclonal antibodies changes in relation to tumor histology over time in a syngeneic rat colon carcinoma model.

PubMed

Örbom, Anders; Eriksson, Sophie E; Elgström, Erika; Ohlsson, Tomas; Nilsson, Rune; Tennvall, Jan; Strand, Sven-Erik

2013-08-01

The therapeutic effect of radioimmunotherapy depends on the distribution of the absorbed dose in relation to viable cancer cells within the tumor, which in turn is a function of the activity distribution. The aim of this study was to investigate the distribution of (177)Lu-DOTA-BR96 monoclonal antibodies targeting the Lewis Y antigen over 7 d using a syngeneic rat model of colon carcinoma. Thirty-eight tumor-bearing rats were intravenously given 25 or 50 MBq of (177)Lu-DOTA-BR96 per kilogram of body weight and were sacrificed 2, 8, 24, 48, 72, 96, 120, or 168 h after injection, with activity measured in blood and tumor samples. Adjacent cryosections of each tumor were analyzed in 3 ways: imaging using a silicon-strip detector for digital autoradiography, staining for histologic characterization, or staining to determine the distribution of the antigen, vasculature, and proliferating cells using immunohistochemistry. Absorbed-dose rate distribution images at the moment of sacrifice were calculated using the activity distribution and a point-dose kernel. The correlations between antigen expression and both activity uptake and absorbed-dose rate were calculated for several regions of interest in each tumor. Nine additional animals with tumors were given unlabeled antibody to evaluate possible immunologic effects. At 2-8 h after injection, activity was found in the tumor margins; at 24 h, in viable antigen-expressing areas within the tumor; and at 48 h and later, increasingly in antigen-negative areas of granulation tissue. The correlation between antigen expression and both the mean activity and the absorbed-dose rate in regions of interest changed from positive to negative after 24 h after injection. Antigen-negative areas also increased over time in animals injected with unlabeled BR96, compared with untreated tumors. The results indicate that viable Lewis Y-expressing tumor cells are most efficiently treated during the initial uptake period. The activity then seems to remain in these initial uptake regions after the elimination of tumor cells and formation of granulation tissue. Further studies using these techniques could aid in determining the effects of the intratumoral activity distribution on overall therapeutic efficacy.

Application of real-time radiation dosimetry using a new silicon LET sensor

NASA Technical Reports Server (NTRS)

Doke, T.; Hayashi, T.; Kikuchi, J.; Nagaoka, S.; Nakano, T.; Sakaguchi, T.; Terasawa, K.; Badhwar, G. D.

1999-01-01

A new type of real-time radiation monitoring device, RRMD-III, consisting of three double-sided silicon strip detectors (DSSDs), has been developed and tested on-board the Space Shuttle mission STS-84. The test succeeded in measuring the linear energy transfer (LET) distribution over the range of 0.2 keV/micrometer to 600 keV/micrometer for 178 h. The Shuttle cruised at an altitude of 300 to 400 km and an inclination angle of 51.6 degrees for 221.3 h, which is equivalent to the International Space Station orbit. The LET distribution obtained for particles was investigated by separating it into galactic cosmic ray (GCR) particles and trapped particles in the South Atlantic Anomaly (SAA) region. The result shows that the contribution in dose-equivalent due to GCR particles is almost equal to that from trapped particles. The total absorbed dose rate during the mission was 0.611 mGy/day; the effective quality factor, 1.64; and the dose equivalent rate, 0.998 mSv/day. The average absorbed dose rates are 0.158 mGy/min for GCR particles and 3.67 mGy/min for trapped particles. The effective quality factors are 2.48 for GCR particles and 1.19 for trapped particles. The absorbed doses obtained by the RRMD-III and a conventional method using TLD (Mg(2)SiO(4)), which was placed around the RRMD-III were compared. It was found that the TLDs showed a lower efficiency, just 58% of absorbed dose registered by the RRMD-III.

Food irradiation dosimetry by opti-chromic technique

NASA Astrophysics Data System (ADS)

Zhan-Jun, Liu; Radak, B. B.; McLaughlin, W. L.

The measurement of gamma-radiation quantities, e.g., absorbed dose in materials such as water, plastics, foodstuffs, is a convenient means of quality assurance in radiation processing. A new dosimetry system, called the "Opti-Chromic" dosimeter, is commercially available in large batches for use as a routine measurement system in the absorbed dose range 10 to 2x10 4 Gy. This dose range covers most food irradiation applications. A statistical evaluation was made of the reproducibility of this dosimeter for measuring doses appropriate for the disinfestation and shelf-life extension of many foods, namely 10 to 2x10 3 Gy. In addition, the small dosimeters were used to map absorbed dose distributions in boxes of foods having four different bulk densities (grapefruit, lemons, peanuts, and wheat bran). It is demonstrated that the dosimeters are rugged and stable enough to be used over a wide temperature and humidity range, and, in fact, can be placed in such environments as the inside of citrus fruits without adverse effects on their ability to give satisfactory dose assessment.

SU-E-CAMPUS-T-03: Four-Dimensional Dose Distribution Measurement Using Plastic Scintillator

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

Hashimoto, M; Kozuka, T; Oguchi, M

2014-06-15

Purpose: To develop the detector for the four-dimensional dose distribution measurement. Methods: We made the prototype detector for four-dimensional dose distribution measurement using a cylindrical plastic scintillator (5 cm diameter) and a conical reflection grass. The plastic scintillator is used as a phantom. When the plastic scintillator is irradiated, the scintillation light was emitted according to absorbed dose distribution. The conical reflection grass was arranged to surround the plastic scintillator, which project to downstream the projection images of the scintillation light. Then, the projection image was reflected to 45 degree direction by flat reflection grass, and was recorded by camcorder.more » By reconstructing the three-dimensional dose distribution from the projection image recorded in each frame, we could obtain the four-dimensional dose distribution. First, we tested the characteristic according to the amount of emitted light. Then we compared of the light profile and the dose profile calculated with the radiotherapy treatment planning system. Results: The dose dependency of the amount of light showed linearity. The pixel detecting smaller amount of light had high sensitivity than the pixel detecting larger amount of light. However the difference of the sensitivity could be corrected from the amount of light detected in each pixel. Both of the depth light profile through the conical reflection grass and the depth dose profile showed the same attenuation in the region deeper than peak depth. In lateral direction, the difference of the both profiles was shown at outside field and penumbra region. We consider that the difference is occurred due to the scatter of the scintillation light in the plastic scintillator block. Conclusion: It was possible to obtain the amount of light corresponding to the absorbed dose distribution from the prototype detector. Four-dimensional dose distributions can be reconstructed with high accuracy by the correction of the scattered light.« less

Model-based versus specific dosimetry in diagnostic context: Comparison of three dosimetric approaches

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

Marcatili, S., E-mail: sara.marcatili@inserm.fr; Villoing, D.; Mauxion, T.

Purpose: The dosimetric assessment of novel radiotracers represents a legal requirement in most countries. While the techniques for the computation of internal absorbed dose in a therapeutic context have made huge progresses in recent years, in a diagnostic scenario the absorbed dose is usually extracted from model-based lookup tables, most often derived from International Commission on Radiological Protection (ICRP) or Medical Internal Radiation Dose (MIRD) Committee models. The level of approximation introduced by these models may impact the resulting dosimetry. The aim of this work is to establish whether a more refined approach to dosimetry can be implemented in nuclearmore » medicine diagnostics, by analyzing a specific case. Methods: The authors calculated absorbed doses to various organs in six healthy volunteers administered with flutemetamol ({sup 18}F) injection. Each patient underwent from 8 to 10 whole body 3D PET/CT scans. This dataset was analyzed using a Monte Carlo (MC) application developed in-house using the toolkit GATE that is capable to take into account patient-specific anatomy and radiotracer distribution at the voxel level. They compared the absorbed doses obtained with GATE to those calculated with two commercially available software: OLINDA/EXM and STRATOS implementing a dose voxel kernel convolution approach. Results: Absorbed doses calculated with GATE were higher than those calculated with OLINDA. The average ratio between GATE absorbed doses and OLINDA’s was 1.38 ± 0.34 σ (from 0.93 to 2.23). The discrepancy was particularly high for the thyroid, with an average GATE/OLINDA ratio of 1.97 ± 0.83 σ for the six patients. Differences between STRATOS and GATE were found to be higher. The average ratio between GATE and STRATOS absorbed doses was 2.51 ± 1.21 σ (from 1.09 to 6.06). Conclusions: This study demonstrates how the choice of the absorbed dose calculation algorithm may introduce a bias when gamma radiations are of importance, as is the case in nuclear medicine diagnostics.« less

SU-E-CAMPUS-I-06: Y90 PET/CT for the Instantaneous Determination of Both Target and Non-Target Absorbed Doses Following Hepatic Radioembolization

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

Pasciak, A; Kao, J

2014-06-15

Purpose The process of converting Yttrium-90 (Y90) PET/CT images into 3D absorbed dose maps will be explained. The simple methods presented will allow the medical physicst to analyze Y90 PET images following radioembolization and determine the absorbed dose to tumor, normal liver parenchyma and other areas of interest, without application of Monte-Carlo radiation transport or dose-point-kernel (DPK) convolution. Methods Absorbed dose can be computed from Y90 PET/CT images based on the premise that radioembolization is a permanent implant with a constant relative activity distribution after infusion. Many Y90 PET/CT publications have used DPK convolution to obtain 3D absorbed dose maps.more » However, this method requires specialized software limiting clinical utility. The Local Deposition method, an alternative to DPK convolution, can be used to obtain absorbed dose and requires no additional computer processing. Pixel values from regions of interest drawn on Y90 PET/CT images can be converted to absorbed dose (Gy) by multiplication with a scalar constant. Results There is evidence that suggests the Local Deposition method may actually be more accurate than DPK convolution and it has been successfully used in a recent Y90 PET/CT publication. We have analytically compared dose-volume-histograms (DVH) for phantom hot-spheres to determine the difference between the DPK and Local Deposition methods, as a function of PET scanner point-spread-function for Y90. We have found that for PET/CT systems with a FWHM greater than 3.0 mm when imaging Y90, the Local Deposition Method provides a more accurate representation of DVH, regardless of target size than DPK convolution. Conclusion Using the Local Deposition Method, post-radioembolization Y90 PET/CT images can be transformed into 3D absorbed dose maps of the liver. An interventional radiologist or a Medical Physicist can perform this transformation in a clinical setting, allowing for rapid prediction of treatment efficacy by comparison to published tumoricidal thresholds.« less

Absorbed dose in target cell nuclei and dose conversion coefficient of radon progeny in the human lung.

PubMed

Nikezic, D; Lau, B M F; Stevanovic, N; Yu, K N

2006-01-01

To calculate the absorbed dose in the human lung due to inhaled radon progeny, ICRP focussed on the layers containing the target cells, i.e., the basal and secretory cells. Such an approach did not consider details of the sensitive cells in the layers. The present work uses the microdosimetric approach and determines the absorbed alpha-particle energy in non-spherical nuclei of target cells (basal and secretory cells). The absorbed energy for alpha particles emitted by radon progeny in the human respiratory tract was calculated in basal- and secretory-cell nuclei, assuming conical and ellipsoidal forms for these cells. Distributions of specific energy for different combinations of alpha-particle sources, energies and targets are calculated and shown. The dose conversion coefficient for radon progeny is reduced for about 2mSv/WLM when conical and ellipsoidal cell nuclei are considered instead of the layers. While changes in the geometry of secretory-cell nuclei do not have significant effects on their absorbed dose, changes from spherical to conical basal-cell nuclei have significantly reduced their absorbed dose from approximately 4 to approximately 3mGy/WLM. This is expected because basal cells are situated close to the end of the range of 6MeV alpha particles. This also underlines the significance of better and more precise information on targets in the T-B tree. A further change in the dose conversion coefficient can be achieved if a different weighting scheme is adopted for the doses for the cells. The results demonstrate the necessity for better information on the target cells for more accurate dosimetry for radon progeny.

Method and apparatus for measuring properties of particle beams using thermo-resistive material properties

DOEpatents

Degtiarenko, Pavel V.; Dotson, Danny Wayne

2007-10-09

A beam position detector for measuring the properties of a charged particle beam, including the beam's position, size, shape, and intensity. One or more absorbers are constructed of thermo-resistive material and positioned to intercept and absorb a portion of the incoming beam power, thereby causing local heating of each absorber. The local temperature increase distribution across the absorber, or the distribution between different absorbers, will depend on the intensity, size, and position of the beam. The absorbers are constructed of a material having a strong dependence of electrical resistivity on temperature. The beam position detector has no moving parts in the vicinity of the beam and is especially suited to beam areas having high ionizing radiation dose rates or poor beam quality, including beams dispersed in the transverse direction and in their time radio frequency structure.

MAGIC-f Gel in Nuclear Medicine Dosimetry: study in an external beam of Iodine-131

NASA Astrophysics Data System (ADS)

Schwarcke, M.; Marques, T.; Garrido, C.; Nicolucci, P.; Baffa, O.

2010-11-01

MAGIC-f gel applicability in Nuclear Medicine dosimetry was investigated by exposure to a 131I source. Calibration was made to provide known absorbed doses in different positions around the source. The absorbed dose in gel was compared with a Monte Carlo Simulation using PENELOPE code and a thermoluminescent dosimetry (TLD). Using MRI analysis for the gel a R2-dose sensitivity of 0.23 s-1Gy-1was obtained. The agreement between dose-distance curves obtained with Monte Carlo simulation and TLD was better than 97% and for MAGIC-f and TLD was better than 98%. The results show the potential of polymer gel for application in nuclear medicine where three dimensional dose distribution is demanded.

Absorbed dose to man from the Se-75 labeled conjugated bile salt SeHCAT: concise communication.

PubMed

Soundy, R G; Simpson, J D; Ross, H M; Merrick, M V

1982-02-01

The absorbed radiation dose that would result from the oral or intravenous administration of SeHCAT (23-[75Se]selena-25-homotaurocholate) has been calculated using the MIRD tables and formulas and data from measurements of whole-body distribution and from long-term whole-body counting in rats, mice, and man. When SeHCAT is administered to normal subjects, the gallbladder is the critical organ, receiving 12 mrad (oral dose) or 22 mrad (i.v.) per microcurie. The whole-body dose is 1 mrad/microCi, whatever the route of administration. In severe hepatic failure the liver might receive 200 mrad/microCi. The activity likely to be used in routine clinical practice is 10 microCi. Where a whole-body counter is used, an activity of 1 microCi has proved adequate. Even at an administered activity of 25 microCi, the absorbed dose is small compared with established techniques of investigating the gastrointestinal tract.

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

Role of shielding in modulating the effects of solar particle events: Monte Carlo calculation of absorbed dose and DNA complex lesions in different organs

NASA Technical Reports Server (NTRS)

Ballarini, F.; Biaggi, M.; De Biaggi, L.; Ferrari, A.; Ottolenghi, A.; Panzarasa, A.; Paretzke, H. G.; Pelliccioni, M.; Sala, P.; Scannicchio, D.;

Role of shielding in modulating the effects of solar particle events: Monte Carlo calculation of absorbed dose and DNA complex lesions in different organs

NASA Astrophysics Data System (ADS)

Ballarini, F.; Biaggi, M.; De Biaggi, L.; Ferrari, A.; Ottolenghi, A.; Panzarasa, A.; Paretzke, H. G.; Pelliccioni, M.; Sala, P.; Scannicchio, D.; Zankl, M.

2004-01-01

Distributions of absorbed dose and DNA clustered damage yields in various organs and tissues following the October 1989 solar particle event (SPE) were calculated by coupling the FLUKA Monte Carlo transport code with two anthropomorphic phantoms (a mathematical model and a voxel model), with the main aim of quantifying the role of the shielding features in modulating organ doses. The phantoms, which were assumed to be in deep space, were inserted into a shielding box of variable thickness and material and were irradiated with the proton spectra of the October 1989 event. Average numbers of DNA lesions per cell in different organs were calculated by adopting a technique already tested in previous works, consisting of integrating into "condensed-history" Monte Carlo transport codes - such as FLUKA - yields of radiobiological damage, either calculated with "event-by-event" track structure simulations, or taken from experimental works available in the literature. More specifically, the yields of "Complex Lesions" (or "CL", defined and calculated as a clustered DNA damage in a previous work) per unit dose and DNA mass (CL Gy -1 Da -1) due to the various beam components, including those derived from nuclear interactions with the shielding and the human body, were integrated in FLUKA. This provided spatial distributions of CL/cell yields in different organs, as well as distributions of absorbed doses. The contributions of primary protons and secondary hadrons were calculated separately, and the simulations were repeated for values of Al shielding thickness ranging between 1 and 20 g/cm 2. Slight differences were found between the two phantom types. Skin and eye lenses were found to receive larger doses with respect to internal organs; however, shielding was more effective for skin and lenses. Secondary particles arising from nuclear interactions were found to have a minor role, although their relative contribution was found to be larger for the Complex Lesions than for the absorbed dose, due to their higher LET and thus higher biological effectiveness.

Depth dose measurements with the Liulin-5 experiment inside the spherical phantom of the MATROSHKA-R project onboard the International Space Station

NASA Astrophysics Data System (ADS)

Semkova, J.; Koleva, R.; Maltchev, St.; Bankov, N.; Benghin, V.; Chernykh, I.; Shurshakov, V.; Petrov, V.; Drobyshev, S.; Nikolaev, I.

2012-02-01

The Liulin-5 experiment is a part of the international project MATROSHKA-R on the Russian segment of the ISS, which uses a tissue-equivalent spherical phantom equipped with a set of radiation detectors. The objective of the MATROSHKA-R project is to provide depth dose distribution of the radiation field inside the sphere in order to get more information on the distribution of dose in a human body. Liulin-5 is a charged particle telescope using three silicon detectors. It measures time resolved energy deposition spectra, linear energy transfer (LET) spectra, particle flux, and absorbed doses of electrons, protons and heavy ions, simultaneously at three depths along the radius of the phantom. Measurements during the minimum of the solar activity in cycle 23 show that the average absorbed daily doses at 40 mm depth in the phantom are between 180 μGy/day and 220 μGy/day. The absorbed doses at 165 mm depth in the phantom decrease by a factor of 1.6-1.8 compared to the doses at 40 mm depth due to the self-shielding of the phantom from trapped protons. The average dose equivalent at 40 mm depth is 590 ± 32 μSV/day and the galactic cosmic rays (GCR) contribute at least 70% of the total dose equivalent at that depth. Shown is that due to the South Atlantic Anomaly (SAA) trapped protons asymmetry and the direction of Liulin-5 lowest shielding zone the dose rates on ascending and descending nodes in SAA are different. The data obtained are compared to data from other radiation detectors on ISS.

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.

Criticality accident dosimetry with ESR spectroscopy.

PubMed

d'Errico, F; Fattibene, P; Onori, S; Pantaloni, M

1996-01-01

The suitability of the ESR alanine and sugar detectors for criticality accident dosimetry was experimentally investigated during an intercomparison of dosimetry techniques. Tests were performed irradiating detectors both free-in-air and on-phantom during controlled critcality excursions at the SILENE reactor in Valduc, France. Several grays of absorbed dose were imparted in neutron gamma-ray fields of various relative intensities and spectral distributions. Analysed results confirmed the potential of these systems which can immediately provide an acute dose assessment with an average underestimate of 30%in the various fields. This performance allows for the screening of severely exposed individuals and meets the IAEA recommendations on the early estimate of accident absorbed doses.

Secondary neutron dose measurement for proton eye treatment using an eye snout with a borated neutron absorber

PubMed Central

2013-01-01

Background We measured and assessed ways to reduce the secondary neutron dose from a system for proton eye treatment. Methods Proton beams of 60.30 MeV were delivered through an eye-treatment snout in passive scattering mode. Allyl diglycol carbonate (CR-39) etch detectors were used to measure the neutron dose in the external field at 0.00, 1.64, and 6.00 cm depths in a water phantom. Secondary neutron doses were measured and compared between those with and without a high-hydrogen–boron-containing block. In addition, the neutron energy and vertices distribution were obtained by using a Geant4 Monte Carlo simulation. Results The ratio of the maximum neutron dose equivalent to the proton absorbed dose (H(10)/D) at 2.00 cm from the beam field edge was 8.79 ± 1.28 mSv/Gy. The ratio of the neutron dose equivalent to the proton absorbed dose with and without a high hydrogen-boron containing block was 0.63 ± 0.06 to 1.15 ± 0.13 mSv/Gy at 2.00 cm from the edge of the field at depths of 0.00, 1.64, and 6.00 cm. Conclusions We found that the out-of-field secondary neutron dose in proton eye treatment with an eye snout is relatively small, and it can be further reduced by installing a borated neutron absorbing material. PMID:23866307

Comparative dosimetry of diode and diamond detectors in electron beams for intraoperative radiation therapy.

PubMed

Björk, P; Knöös, T; Nilsson, P

2000-11-01

The aim of the present study is to examine the validity of using silicon semiconductor detectors in degraded electron beams with a broad energy spectrum and a wide angular distribution. A comparison is made with diamond detector measurements, which is the dosimeter considered to give the best results provided that dose rate effects are corrected for. Two-dimensional relative absorbed dose distributions in electron beams (6-20 MeV) for intraoperative radiation therapy (IORT) are measured in a water phantom. To quantify deviations between the detectors, a dose comparison tool that simultaneously examines the dose difference and distance to agreement (DTA) is used to evaluate the results in low- and high-dose gradient regions, respectively. Uncertainties of the experimental measurement setup (+/- 1% and +/- 0.5 mm) are taken into account by calculating a composite distribution that fails this dose-difference and DTA acceptance limit. Thus, the resulting area of disagreement should be related to differences in detector performance. The dose distributions obtained with the diode are generally in very good agreement with diamond detector measurements. The buildup region and the dose falloff region show good agreement with increasing electron energy, while the region outside the radiation field close to the water surface shows an increased difference with energy. The small discrepancies in the composite distributions are due to several factors: (a) variation of the silicon-to-water collision stopping-power ratio with electron energy, (b) a more pronounced directional dependence for diodes than for diamonds, and (c) variation of the electron fluence perturbation correction factor with depth. For all investigated treatment cones and energies, the deviation is within dose-difference and DTA acceptance criteria of +/- 3% and +/- 1 mm, respectively. Therefore, p-type silicon diodes are well suited, in the sense that they give results in close agreement with diamond detectors, for practical measurements of relative absorbed dose distributions in degraded electron beams used for IORT.

Postlumpectomy Focal Brachytherapy for Simultaneous Treatment of Surgical Cavity and Draining Lymph Nodes

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

Hrycushko, Brian A.; Li Shihong; Shi Chengyu

2011-03-01

Purpose: The primary objective was to investigate a novel focal brachytherapy technique using lipid nanoparticle (liposome)-carried {beta}-emitting radionuclides (rhenium-186 [{sup 186}Re]/rhenium-188 [{sup 188}Re]) to simultaneously treat the postlumpectomy surgical cavity and draining lymph nodes. Methods and Materials: Cumulative activity distributions in the lumpectomy cavity and lymph nodes were extrapolated from small animal imaging and human lymphoscintigraphy data. Absorbed dose calculations were performed for lumpectomy cavities with spherical and ellipsoidal shapes and lymph nodes within human subjects by use of the dose point kernel convolution method. Results: Dose calculations showed that therapeutic dose levels within the lumpectomy cavity wall can covermore » 2- and 5-mm depths for {sup 186}Re and {sup 188}Re liposomes, respectively. The absorbed doses at 1 cm sharply decreased to only 1.3% to 3.7% of the doses at 2 mm for {sup 186}Re liposomes and 5 mm for {sup 188}Re liposomes. Concurrently, the draining sentinel lymph nodes would receive a high focal therapeutic absorbed dose, whereas the average dose to 1 cm of surrounding tissue received less than 1% of that within the nodes. Conclusions: Focal brachytherapy by use of {sup 186}Re/{sup 188}Re liposomes was theoretically shown to be capable of simultaneously treating the lumpectomy cavity wall and draining sentinel lymph nodes with high absorbed doses while significantly lowering dose to surrounding healthy tissue. In turn, this allows for dose escalation to regions of higher probability of containing residual tumor cells after lumpectomy while reducing normal tissue complications.« less

SU-F-T-255: Accuracy and Precision of Dynamic Tracking Irradiation with VERO-4DRT System

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

Hayashi, N; Takada, Y; Mizuno, T

2016-06-15

Purpose: The VERO-4DRT system is able to provide dynamic tracking irradiation (DTI) for the target with respiratory motion. This technique requires enough commissioning for clinical implementation. The purpose of this study is to make sure the accuracy and precision of DTI using VERO- 4DRT through commissioning from fundamental evaluation to end-to-end test. Method: We evaluated several contents for DTI commissioning: the accuracy of absorption dose at isocenter in DTI, the field size and penumbra of DTI, the accuracy of 4D modeling in DTI. All evaluations were performed by respiratory motion phantom (Quasar phantom). These contents were compared the results betweenmore » static irradiation and DTI. The shape of radiation field was set to square from 3 cm × 3 cm to 10 cm × 10 cm. The micro 3D chamber and Gafchromic EBT3 film were used for absorbed dose and relative dose distribution measurement, respectively. The sine and irregular shaped waves were used for demonstrative respiratory motion. The visicoil was implanted into the phantom for guidance of respiratory motion. The respiration patterns of frequency and motion amount were set to 10–15 BPM and 1–2 cm, respectively. Results: As the result of absorbed dose of DTI in comparison with static irradiation, the average dose error at isocenter was 0.5% even though various respiratory patterns were set on. As the result of relative dose distribution, the field size (set it on 50% dose line) was not significantly changed in all respiratory patterns. However, the penumbra was larger in greater respiratory motion (up to 4.1 mm). The 4D modeling coincidence between actual and created waves was within 1%. Conclusion: The DTI using VERO-4DRT can provide sufficient accuracy and precision in absorbed dose and distribution. However, the patientspecific quantitative internal margin corresponding respiratory motion should be taken into consideration with image guidance.« less

Depth dependence of absorbed dose, dose equivalent and linear energy transfer spectra of galactic and trapped particles in polyethylene and comparison with calculations of models

NASA Technical Reports Server (NTRS)

Badhwar, G. D.; Cucinotta, F. A.; Wilson, J. W. (Principal Investigator)

1998-01-01

A matched set of five tissue-equivalent proportional counters (TEPCs), embedded at the centers of 0 (bare), 3, 5, 8 and 12-inch-diameter polyethylene spheres, were flown on the Shuttle flight STS-81 (inclination 51.65 degrees, altitude approximately 400 km). The data obtained were separated into contributions from trapped protons and galactic cosmic radiation (GCR). From the measured linear energy transfer (LET) spectra, the absorbed dose and dose-equivalent rates were calculated. The results were compared to calculations made with the radiation transport model HZETRN/NUCFRG2, using the GCR free-space spectra, orbit-averaged geomagnetic transmission function and Shuttle shielding distributions. The comparison shows that the model fits the dose rates to a root mean square (rms) error of 5%, and dose-equivalent rates to an rms error of 10%. Fairly good agreement between the LET spectra was found; however, differences are seen at both low and high LET. These differences can be understood as due to the combined effects of chord-length variation and detector response function. These results rule out a number of radiation transport/nuclear fragmentation models. Similar comparisons of trapped-proton dose rates were made between calculations made with the proton transport model BRYNTRN using the AP-8 MIN trapped-proton model and Shuttle shielding distributions. The predictions of absorbed dose and dose-equivalent rates are fairly good. However, the prediction of the LET spectra below approximately 30 keV/microm shows the need to improve the AP-8 model. These results have strong implications for shielding requirements for an interplanetary manned mission.

Monte Carlo Assessments of Absorbed Doses to the Hands of Radiopharmaceutical Workers Due to Photon Emitters

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

Ilas, Dan; Eckerman, Keith F; Karagiannis, Harriet

This paper describes the characterization of radiation doses to the hands of nuclear medicine technicians resulting from the handling of radiopharmaceuticals. Radiation monitoring using ring dosimeters indicates that finger dosimeters that are used to show compliance with applicable regulations may overestimate or underestimate radiation doses to the skin depending on the nature of the particular procedure and the radionuclide being handled. To better understand the parameters governing the absorbed dose distributions, a detailed model of the hands was created and used in Monte Carlo simulations of selected nuclear medicine procedures. Simulations of realistic configurations typical for workers handling radiopharmaceuticals weremore » performedfor a range of energies of the source photons. The lack of charged-particle equilibrium necessitated full photon-electron coupled transport calculations. The results show that the dose to different regions of the fingers can differ substantially from dosimeter readings when dosimeters are located at the base of the finger. We tried to identify consistent patterns that relate the actual dose to the dosimeter readings. These patterns depend on the specific work conditions and can be used to better assess the absorbed dose to different regions of the exposed skin.« less

Impact of interpatient variability on organ dose estimates according to MIRD schema: Uncertainty and variance-based sensitivity analysis.

PubMed

Zvereva, Alexandra; Kamp, Florian; Schlattl, Helmut; Zankl, Maria; Parodi, Katia

2018-05-17

Variance-based sensitivity analysis (SA) is described and applied to the radiation dosimetry model proposed by the Committee on Medical Internal Radiation Dose (MIRD) for the organ-level absorbed dose calculations in nuclear medicine. The uncertainties in the dose coefficients thus calculated are also evaluated. A Monte Carlo approach was used to compute first-order and total-effect SA indices, which rank the input factors according to their influence on the uncertainty in the output organ doses. These methods were applied to the radiopharmaceutical (S)-4-(3- 18 F-fluoropropyl)-L-glutamic acid ( 18 F-FSPG) as an example. Since 18 F-FSPG has 11 notable source regions, a 22-dimensional model was considered here, where 11 input factors are the time-integrated activity coefficients (TIACs) in the source regions and 11 input factors correspond to the sets of the specific absorbed fractions (SAFs) employed in the dose calculation. The SA was restricted to the foregoing 22 input factors. The distributions of the input factors were built based on TIACs of five individuals to whom the radiopharmaceutical 18 F-FSPG was administered and six anatomical models, representing two reference, two overweight, and two slim individuals. The self-absorption SAFs were mass-scaled to correspond to the reference organ masses. The estimated relative uncertainties were in the range 10%-30%, with a minimum and a maximum for absorbed dose coefficients for urinary bladder wall and heart wall, respectively. The applied global variance-based SA enabled us to identify the input factors that have the highest influence on the uncertainty in the organ doses. With the applied mass-scaling of the self-absorption SAFs, these factors included the TIACs for absorbed dose coefficients in the source regions and the SAFs from blood as source region for absorbed dose coefficients in highly vascularized target regions. For some combinations of proximal target and source regions, the corresponding cross-fire SAFs were found to have an impact. Global variance-based SA has been for the first time applied to the MIRD schema for internal dose calculation. Our findings suggest that uncertainties in computed organ doses can be substantially reduced by performing an accurate determination of TIACs in the source regions, accompanied by the estimation of individual source region masses along with the usage of an appropriate blood distribution in a patient's body and, in a few cases, the cross-fire SAFs from proximal source regions. © 2018 American Association of Physicists in Medicine.

SU-D-213-06: Dosimetry of Modulated Electron Radiation Therapy Using Fricke Gel Dosimeter

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

Gawad, M Abdel; Elgohary, M; Hassaan, M

Purpose: Modulated electron radiation therapy (MERT) has been proposed as an effective modality for treatment of superficial targets. MERT utilizes multiple beams of different energies which are intensity modulated to deliver optimized dose distribution. Energy independent dosimeters are thus needed for quantitative evaluations of MERT dose distributions and measurements of absolute doses delivered to patients. Thus in the current work we study the feasibility of Fricke gel dosimeters in MERT dosimetry. Methods: Batches of radiation sensitive Fricke gel is fabricated and poured into polymethyl methacrylate cuvettes. The samples were irradiated in solid water phantom and a thick layer of bolusmore » was used as a buildup. A spectrophotometer system was used for measuring the color changes (the absorbance) before and after irradiation and then we calculate net absorbance. We constructed calibration curves to relate the measured absorbance in terms of absorbed dose for all available electron energies. Dosimetric measurements were performed for mixed electron beam delivery and we also performed measurement for segmented field delivery with the dosimeter placed at the junction of two adjacent electron beams of different energies. Dose measured by our gel dosimetry is compared to that calculation from our precise treatment planning system. We also initiated a Monte Carlo study to evaluate the water equivalence of our dosimeters. MCBEAM and MCSIM codes were used for treatment head simulation and phantom dose calculation. PDDs and profiles were calculated for electron beams incident on a phantom designed with 1cm slab of Fricke gel. Results: The calibration curves showed no observed energy dependence with all studied electron beam energies. Good agreement was obtained between dose calculated and that obtained by gel dosimetry. Monte Carlo results illustrated the tissue equivalency of our Gel dosimeters. Conclusion: Fricke Gel dosimeters represent a good option for the dosimetric quality assurance prior to MERT application.« less

Dose perturbations due to in vivo dosimetry with diodes.

PubMed

Alecu, R; Feldmeier, J J; Alecu, M

1997-03-01

In vivo dosimetry performed with semiconductor detectors is a reliable method for patient dose control. The purpose of this study is to evaluate the perturbations introduced in the patient's absorbed dose distribution by three types of commercially available diodes (Isorad, Sun Nuclear Corp.; model 114200, 114300 and 114400) from the same company and to present possible solutions for minimizing this side-effect.

Monte Carlo dose distribution calculation at nuclear level for Auger-emitting radionuclide energies.

PubMed

Di Maria, S; Belchior, A; Romanets, Y; Paulo, A; Vaz, P

2018-05-01

The distribution of radiopharmaceuticals in tumor cells represents a fundamental aspect for a successful molecular targeted radiotherapy. It was largely demonstrated at microscopic level that only a fraction of cells in tumoral tissues incorporate the radiolabel. In addition, the distribution of the radionuclides at sub-cellular level, namely inside each nucleus, should also be investigated for accurate dosimetry estimation. The most used method to perform cellular dosimetry is the MIRD one, where S-values are able to estimate cellular absorbed doses for several electron energies, nucleus diameters, and considering homogeneous source distributions. However the radionuclide distribution inside nuclei can be also highly non-homogeneous. The aim of this study is to show in what extent a non-accurate cellular dosimetry could lead to misinterpretations of surviving cell fraction vs dose relationship; in this context, a dosimetric case study with 99m Tc is also presented. The state-of-art MCNP6 Monte Carlo simulation was used in order to model cell structures both in MIRD geometry (MG) and MIRD modified geometries (MMG), where also entire mitotic chromosome volumes were considered (each structure was modeled as liquid water material). In order to simulate a wide energy range of Auger emitting radionuclides, four mono energetic electron emissions were considered, namely 213eV, 6keV, 11keV and 20keV. A dosimetric calculation for 99m Tc undergoing inhomogeneous nuclear internalization was also performed. After a successful validation step between MIRD and our computed S-values for three Auger-emitting radionuclides ( 99m Tc, 125 I and 64 Cu), absorbed dose results showed that the standard MG could differ from the MMG from one to three orders of magnitude. These results were also confirmed by considering the 99m Tc spectrum emission (Auger and internal conversion electrons). Moreover, considering an inhomogeneous radionuclide distribution, the average electron energy that maximizes the absorbed dose was found to be different for MG and MMG. The modeling of realistic radionuclide localization inside cells, including a inhomogeneous nuclear distribution, revealed that i) a strong bias in surviving cell fraction vs dose relationships (taking to different radiobiological models) can arise; ii) the alternative models might contribute to a more accurate prediction of the radiobiological effects inherent to more specific molecular targeted radiotherapy strategies. Copyright © 2018 Elsevier Ltd. All rights reserved.

Enhancing Cytogenetic Biological Dosimetry Capabilities of the Philippines for Nuclear Incident Preparedness.

PubMed

Asaad, Celia O; Caraos, Gloriamaris L; Robles, Gerardo Jose M; Asa, Anie Day D C; Cobar, Maria Lucia C; Asaad, Al-Ahmadgaid

2016-01-01

The utility of a biological dosimeter based on the analysis of dicentrics is invaluable in the event of a radiological emergency wherein the estimated absorbed dose of an exposed individual is crucial in the proper medical management of patients. The technique is also used for routine monitoring of occupationally exposed workers to determine radiation exposure. An in vitro irradiation study of human peripheral blood lymphocytes was conducted to establish a dose-response curve for radiation-induced dicentric aberrations. Blood samples were collected from volunteer donors and together with optically stimulated luminescence (OSL) dosimeters and were irradiated at 0, 0.1, 0.25, 0.5, 0.75, 1, 2, 4, and 6 Gy using a cobalt-60 radiotherapy unit. Blood samples were cultured for 48 h, and the metaphase chromosomes were prepared following the procedure of the International Atomic Energy Agency's Emergency Preparedness and Response - Biodosimetry 2011 manual. At least 100 metaphases were scored for dicentric aberrations at each dose point. The data were analyzed using R language program. The results indicated that the distribution of dicentric cells followed a Poisson distribution and the dose-response curve was established using the estimated model, Y dic = 0.0003 (±0.0003) +0.0336 (±0.0115) × D + 0.0236 (±0.0054) × D 2 . In this study, the reliability of the dose-response curve in estimating the absorbed dose was also validated for 2 and 4 Gy using OSL dosimeters. The data were fitted into the constructed curve. The result of the validation study showed that the obtained estimate for the absorbed exposure doses was close to the true exposure doses.

Pain and mean absorbed dose to the pubic bone after radiotherapy among gynecological cancer survivors.

PubMed

Waldenström, Ann-Charlotte; Olsson, Caroline; Wilderäng, Ulrica; Dunberger, Gail; Lind, Helena; al-Abany, Massoud; Palm, Åsa; Avall-Lundqvist, Elisabeth; Johansson, Karl-Axel; Steineck, Gunnar

2011-07-15

To analyze the relationship between mean absorbed dose to the pubic bone after pelvic radiotherapy for gynecological cancer and occurrence of pubic bone pain among long-term survivors. In an unselected, population-based study, we identified 823 long-term gynecological cancer survivors treated with pelvic radiotherapy during 1991-2003. For comparison, we used a non-radiation-treated control population of 478 matched women from the Swedish Population Register. Pain, intensity of pain, and functional impairment due to pain in the pubic bone were assessed with a study-specific postal questionnaire. We analyzed data from 650 survivors (participation rate 79%) with median follow-up of 6.3 years (range, 2.3-15.0 years) along with 344 control women (participation rate, 72 %). Ten percent of the survivors were treated with radiotherapy; ninety percent with surgery plus radiotherapy. Brachytherapy was added in 81%. Complete treatment records were recovered for 538/650 survivors, with dose distribution data including dose-volume histograms over the pubic bone. Pubic bone pain was reported by 73 survivors (11%); 59/517 (11%) had been exposed to mean absorbed external beam doses <52.5 Gy to the pubic bone and 5/12 (42%) to mean absorbed external beam doses ≥ 52.5 Gy. Thirty-three survivors reported pain affecting sleep, a 13-fold increased prevalence compared with control women. Forty-nine survivors reported functional impairment measured as pain walking indoors, a 10-fold increased prevalence. Mean absorbed external beam dose above 52.5 Gy to the pubic bone increases the occurrence of pain in the pubic bone and may affect daily life of long-term survivors treated with radiotherapy for gynecological cancer. Copyright © 2011 Elsevier Inc. All rights reserved.

Pain and Mean Absorbed Dose to the Pubic Bone After Radiotherapy Among Gynecological Cancer Survivors

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

Waldenstroem, Ann-Charlotte, E-mail: ann-charlotte.waldenstrom@oncology.gu.se; Department of Oncology, Sahlgrenska University Hospital, Gothenburg; Olsson, Caroline

Purpose: To analyze the relationship between mean absorbed dose to the pubic bone after pelvic radiotherapy for gynecological cancer and occurrence of pubic bone pain among long-term survivors. Methods and Materials: In an unselected, population-based study, we identified 823 long-term gynecological cancer survivors treated with pelvic radiotherapy during 1991-2003. For comparison, we used a non-radiation-treated control population of 478 matched women from the Swedish Population Register. Pain, intensity of pain, and functional impairment due to pain in the pubic bone were assessed with a study-specific postal questionnaire. Results: We analyzed data from 650 survivors (participation rate 79%) with median follow-upmore » of 6.3 years (range, 2.3-15.0 years) along with 344 control women (participation rate, 72 %). Ten percent of the survivors were treated with radiotherapy; ninety percent with surgery plus radiotherapy. Brachytherapy was added in 81%. Complete treatment records were recovered for 538/650 survivors, with dose distribution data including dose-volume histograms over the pubic bone. Pubic bone pain was reported by 73 survivors (11%); 59/517 (11%) had been exposed to mean absorbed external beam doses <52.5 Gy to the pubic bone and 5/12 (42%) to mean absorbed external beam doses {>=}52.5 Gy. Thirty-three survivors reported pain affecting sleep, a 13-fold increased prevalence compared with control women. Forty-nine survivors reported functional impairment measured as pain walking indoors, a 10-fold increased prevalence. Conclusions: Mean absorbed external beam dose above 52.5 Gy to the pubic bone increases the occurrence of pain in the pubic bone and may affect daily life of long-term survivors treated with radiotherapy for gynecological cancer.« less

Calculation of radiation therapy dose using all particle Monte Carlo transport

DOEpatents

Chandler, William P.; Hartmann-Siantar, Christine L.; Rathkopf, James A.

1999-01-01

The actual radiation dose absorbed in the body is calculated using three-dimensional Monte Carlo transport. Neutrons, protons, deuterons, tritons, helium-3, alpha particles, photons, electrons, and positrons are transported in a completely coupled manner, using this Monte Carlo All-Particle Method (MCAPM). The major elements of the invention include: computer hardware, user description of the patient, description of the radiation source, physical databases, Monte Carlo transport, and output of dose distributions. This facilitated the estimation of dose distributions on a Cartesian grid for neutrons, photons, electrons, positrons, and heavy charged-particles incident on any biological target, with resolutions ranging from microns to centimeters. Calculations can be extended to estimate dose distributions on general-geometry (non-Cartesian) grids for biological and/or non-biological media.

Calculation of radiation therapy dose using all particle Monte Carlo transport

DOEpatents

Chandler, W.P.; Hartmann-Siantar, C.L.; Rathkopf, J.A.

1999-02-09

The actual radiation dose absorbed in the body is calculated using three-dimensional Monte Carlo transport. Neutrons, protons, deuterons, tritons, helium-3, alpha particles, photons, electrons, and positrons are transported in a completely coupled manner, using this Monte Carlo All-Particle Method (MCAPM). The major elements of the invention include: computer hardware, user description of the patient, description of the radiation source, physical databases, Monte Carlo transport, and output of dose distributions. This facilitated the estimation of dose distributions on a Cartesian grid for neutrons, photons, electrons, positrons, and heavy charged-particles incident on any biological target, with resolutions ranging from microns to centimeters. Calculations can be extended to estimate dose distributions on general-geometry (non-Cartesian) grids for biological and/or non-biological media. 57 figs.

[Polymer Gel Dosimeter].

PubMed

Hayashi, Shin-Ichiro

2017-01-01

With rapid advances being made in radiotherapy treatment, three-dimensional (3D) dose measurement techniques of great precision are required more than ever before. It is expected that 3D polymer gel dosimeters will satisfy clinical needs for an effective detector that can measure the complex 3D dose distributions. Polymer gel dosimeters are devices that utilize the radiation-induced polymerization reactions of vinyl monomers in a gel to store information about radiation dose. The 3D absorbed dose distribution can be deduced from the resulting polymer distribution using several imaging modalities, such as MRI, X-ray and optical CTs. In this article, the fundamental characteristics of polymer gel dosimeter are reviewed and some challenging keys are also suggested for the widely spread in clinical use.

Analytical functions for beta and gamma absorbed fractions of iodine-131 in spherical and ellipsoidal volumes.

PubMed

Mowlavi, Ali Asghar; Fornasier, Maria Rossa; Mirzaei, Mohammd; Bregant, Paola; de Denaro, Mario

2014-10-01

The beta and gamma absorbed fractions in organs and tissues are the important key factors of radionuclide internal dosimetry based on Medical Internal Radiation Dose (MIRD) approach. The aim of this study is to find suitable analytical functions for beta and gamma absorbed fractions in spherical and ellipsoidal volumes with a uniform distribution of iodine-131 radionuclide. MCNPX code has been used to calculate the energy absorption from beta and gamma rays of iodine-131 uniformly distributed inside different ellipsoids and spheres, and then the absorbed fractions have been evaluated. We have found the fit parameters of a suitable analytical function for the beta absorbed fraction, depending on a generalized radius for ellipsoid based on the radius of sphere, and a linear fit function for the gamma absorbed fraction. The analytical functions that we obtained from fitting process in Monte Carlo data can be used for obtaining the absorbed fractions of iodine-131 beta and gamma rays for any volume of the thyroid lobe. Moreover, our results for the spheres are in good agreement with the results of MIRD and other scientific literatures.

Investigating the dose distribution in the uncompressed breast with a dedicated CT mammotomography system

NASA Astrophysics Data System (ADS)

Crotty, Dominic J.; Brady, Samuel L.; Jackson, D'Vone C.; Toncheva, Greta I.; Anderson, Colin E.; Yoshizumi, Terry T.; Tornai, Martin P.

2010-04-01

A dual modality SPECT-CT prototype dedicated to uncompressed breast imaging (mammotomography) has been developed. The CT subsystem incorporates an ultra-thick K-edge filtration technique producing a quasi-monochromatic x-ray cone beam to optimize the dose efficiency for uncompressed breast tomography. We characterize the absorbed dose to the breast under normal tomographic cone beam image acquisition protocols using both TLD measurements and ionization chamber-calibrated radiochromic film. Geometric and anthropomorphic breast phantoms are filled with 1000mL of water and oil to simulate different breast compositions and varying object shapes having density bounds of 100% glandular and fatty breast compositions, respectively. Doses to the water filled geometric and anthropomorphic breast phantoms for a tomographic scan range from 1.3-7.3mGy and 1.7-6.3mGy, respectively, with a mean whole-breast dose of 4.5mGy for the water-filled anthropomorphic phantom. Measured dose distribution trends indicate lower doses in the center of the breast phantoms towards the chest wall along with higher doses near the peripheries and nipple regions. Measured doses to the oil-filled phantoms are consistently lower across all volume shapes (mean dose, 3.8mGy for the anthropomorphic breast). Results agree with Monte Carlo dose estimates generated for uncompressed breast imaging and illustrate the advantages of using the novel K-edge filtered beam to minimize absorbed dose to the breast during fully-3D imaging.

Absorbed dose measurements for kV-cone beam computed tomography in image-guided radiation therapy

NASA Astrophysics Data System (ADS)

Hioki, Kazunari; Araki, Fujio; Ohno, Takeshi; Nakaguchi, Yuji; Tomiyama, Yuuki

2014-12-01

In this study, we develope a novel method to directly evaluate an absorbed dose-to-water for kilovoltage-cone beam computed tomography (kV-CBCT) in image-guided radiation therapy (IGRT). Absorbed doses for the kV-CBCT systems of the Varian On-Board Imager (OBI) and the Elekta X-ray Volumetric Imager (XVI) were measured by a Farmer ionization chamber with a 60Co calibration factor. The chamber measurements were performed at the center and four peripheral points in body-type (30 cm diameter and 51 cm length) and head-type (16 cm diameter and 33 cm length) cylindrical water phantoms. The measured ionization was converted to the absorbed dose-to-water by using a 60Co calibration factor and a Monte Carlo (MC)-calculated beam quality conversion factor, kQ, for 60Co to kV-CBCT. The irradiation for OBI and XVI was performed with pelvis and head modes for the body- and the head-type phantoms, respectively. In addition, the dose distributions in the phantom for both kV-CBCT systems were calculated with MC method and were compared with measured values. The MC-calculated doses were calibrated at the center in the water phantom and compared with measured doses at four peripheral points. The measured absorbed doses at the center in the body-type phantom were 1.96 cGy for OBI and 0.83 cGy for XVI. The peripheral doses were 2.36-2.90 cGy for OBI and 0.83-1.06 cGy for XVI. The doses for XVI were lower up to approximately one-third of those for OBI. Similarly, the measured doses at the center in the head-type phantom were 0.48 cGy for OBI and 0.21 cGy for XVI. The peripheral doses were 0.26-0.66 cGy for OBI and 0.16-0.30 cGy for XVI. The calculated peripheral doses agreed within 3% in the pelvis mode and within 4% in the head mode with measured doses for both kV-CBCT systems. In addition, the absorbed dose determined in this study was approximately 4% lower than that in TG-61 but the absorbed dose by both methods was in agreement within their combined uncertainty. This method is more robust and accurate compared to the dosimetry based on a conventional air-kerma calibration factor. Therefore, it is possible to be used as a standard dosimetry protocol for kV-CBCT in IGRT.

Neutron production from beam-modifying devices in a modern double scattering proton therapy beam delivery system.

PubMed

Pérez-Andújar, Angélica; Newhauser, Wayne D; Deluca, Paul M

2009-02-21

In this work the neutron production in a passive beam delivery system was investigated. Secondary particles including neutrons are created as the proton beam interacts with beam shaping devices in the treatment head. Stray neutron exposure to the whole body may increase the risk that the patient develops a radiogenic cancer years or decades after radiotherapy. We simulated a passive proton beam delivery system with double scattering technology to determine the neutron production and energy distribution at 200 MeV proton energy. Specifically, we studied the neutron absorbed dose per therapeutic absorbed dose, the neutron absorbed dose per source particle and the neutron energy spectrum at various locations around the nozzle. We also investigated the neutron production along the nozzle's central axis. The absorbed doses and neutron spectra were simulated with the MCNPX Monte Carlo code. The simulations revealed that the range modulation wheel (RMW) is the most intense neutron source of any of the beam spreading devices within the nozzle. This finding suggests that it may be helpful to refine the design of the RMW assembly, e.g., by adding local shielding, to suppress neutron-induced damage to components in the nozzle and to reduce the shielding thickness of the treatment vault. The simulations also revealed that the neutron dose to the patient is predominated by neutrons produced in the field defining collimator assembly, located just upstream of the patient.

SU-F-I-53: Coded Aperture Coherent Scatter Spectral Imaging of the Breast: A Monte Carlo Evaluation of Absorbed Dose

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

Morris, R; Lakshmanan, M; Fong, G

Purpose: Coherent scatter based imaging has shown improved contrast and molecular specificity over conventional digital mammography however the biological risks have not been quantified due to a lack of accurate information on absorbed dose. This study intends to characterize the dose distribution and average glandular dose from coded aperture coherent scatter spectral imaging of the breast. The dose deposited in the breast from this new diagnostic imaging modality has not yet been quantitatively evaluated. Here, various digitized anthropomorphic phantoms are tested in a Monte Carlo simulation to evaluate the absorbed dose distribution and average glandular dose using clinically feasible scanmore » protocols. Methods: Geant4 Monte Carlo radiation transport simulation software is used to replicate the coded aperture coherent scatter spectral imaging system. Energy sensitive, photon counting detectors are used to characterize the x-ray beam spectra for various imaging protocols. This input spectra is cross-validated with the results from XSPECT, a commercially available application that yields x-ray tube specific spectra for the operating parameters employed. XSPECT is also used to determine the appropriate number of photons emitted per mAs of tube current at a given kVp tube potential. With the implementation of the XCAT digital anthropomorphic breast phantom library, a variety of breast sizes with differing anatomical structure are evaluated. Simulations were performed with and without compression of the breast for dose comparison. Results: Through the Monte Carlo evaluation of a diverse population of breast types imaged under real-world scan conditions, a clinically relevant average glandular dose for this new imaging modality is extrapolated. Conclusion: With access to the physical coherent scatter imaging system used in the simulation, the results of this Monte Carlo study may be used to directly influence the future development of the modality to keep breast dose to a minimum while still maintaining clinically viable image quality.« less

Contrast-enhanced radiotherapy: feasibility and characteristics of the physical absorbed dose distribution for deep-seated tumors

NASA Astrophysics Data System (ADS)

Garnica-Garza, H. M.

2009-09-01

Radiotherapy using kilovoltage x-rays in conjunction with contrast agents incorporated into the tumor, gold nanoparticles in particular, could represent a potential alternative to current techniques based on high-energy linear accelerators. In this paper, using the voxelized Zubal phantom in conjunction with the Monte Carlo code PENELOPE to model a prostate cancer treatment, it is shown that in combination with a 360° arc delivery technique, tumoricidal doses of radiation can be delivered to deep-seated tumors while still providing acceptable doses to the skin and other organs at risk for gold concentrations in the tumor within the range of 7-10 mg-Au per gram of tissue. Under these conditions and using a x-ray beam with 90% of the fluence within the range of 80-200 keV, a 72 Gy physical absorbed dose to the prostate can be delivered, while keeping the rectal wall, bladder, skin and femoral heads below 65 Gy, 55 Gy, 40 Gy and 30 Gy, respectively. However, it is also shown that non-uniformities in the contrast agent concentration lead to a severe degradation of the dose distribution and that, therefore, techniques to locally quantify the presence of the contrast agent would be necessary in order to determine the incident x-ray fluence that best reproduces the dosimetry obtained under conditions of uniform contrast agent distribution.

Direct intratumoral infusion of liposome encapsulated rhenium radionuclides for cancer therapy: Effects of nonuniform intratumoral dose distribution

PubMed Central

Hrycushko, Brian A.; Li, Shihong; Goins, Beth; Otto, Randal A.; Bao, Ande

2011-01-01

Purpose: Focused radiation therapy by direct intratumoral infusion of lipid nanoparticle (liposome)-carried beta-emitting radionuclides has shown promising results in animal model studies; however, little is known about the impact the intratumoral liposomal radionuclide distribution may have on tumor control. The primary objective of this work was to investigate the effects the intratumoral absorbed dose distributions from this cancer therapy modality have on tumor control and treatment planning by combining dosimetric and radiobiological modeling with in vivo imaging data. Methods:99mTc-encapsulated liposomes were intratumorally infused with a single injection location to human head and neck squamous cell carcinoma xenografts in nude rats. High resolution in vivo planar imaging was performed at various time points for quantifying intratumoral retention following infusion. The intratumoral liposomal radioactivity distribution was obtained from 1 mm resolution pinhole collimator SPECT imaging coregistered with CT imaging of excised tumors at 20 h postinfusion. Coregistered images were used for intratumoral dosimetric and radiobiological modeling at a voxel level following extrapolation to the therapeutic analogs, 186Re∕188Re liposomes. Effective uniform dose (EUD) and tumor control probability (TCP) were used to assess therapy effectiveness and possible methods of improving upon tumor control with this radiation therapy modality. Results: Dosimetric analysis showed that average tumor absorbed doses of 8.6 Gy∕MBq (318.2 Gy∕mCi) and 5.7 Gy∕MBq (209.1 Gy∕mCi) could be delivered with this protocol of radiation delivery for 186Re∕188Re liposomes, respectively, and 37–92 MBq (1–2.5 mCi)∕g tumor administered activity; however, large intratumoral absorbed dose heterogeneity, as seen in dose-volume histograms, resulted in insignificant values of EUD and TCP for achieving tumor control. It is indicated that the use of liposomes encapsulating radionuclides with higher energy beta emissions, dose escalation through increased specific activity, and increasing the number of direct tumor infusion sites improve tumor control. For larger tumors, the use of multiple infusion locations was modeled to be much more efficient, in terms of activity usage, at improving EUD and TCP to achieve a tumoricidal effect. Conclusions: Direct intratumoral infusion of beta-emitting radionuclide encapsulated liposomes shows promise for cancer therapy by achieving large focally delivered tumor doses. However, the results of this work also indicate that average tumor dose may underestimate tumoricidal effect due to substantial heterogeneity in intratumoral liposomal radionuclide distributions. The resulting intratumoral distribution of liposomes following infusion should be taken into account in treatment planning and evaluation in a clinical setting for an optimal cancer therapy. PMID:21520844

Direct intratumoral infusion of liposome encapsulated rhenium radionuclides for cancer therapy: Effects of nonuniform intratumoral dose distribution

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

Hrycushko, Brian A.; Li Shihong; Goins, Beth

2011-03-15

Purpose: Focused radiation therapy by direct intratumoral infusion of lipid nanoparticle (liposome)-carried beta-emitting radionuclides has shown promising results in animal model studies; however, little is known about the impact the intratumoral liposomal radionuclide distribution may have on tumor control. The primary objective of this work was to investigate the effects the intratumoral absorbed dose distributions from this cancer therapy modality have on tumor control and treatment planning by combining dosimetric and radiobiological modeling with in vivo imaging data. Methods: {sup 99m}Tc-encapsulated liposomes were intratumorally infused with a single injection location to human head and neck squamous cell carcinoma xenografts inmore » nude rats. High resolution in vivo planar imaging was performed at various time points for quantifying intratumoral retention following infusion. The intratumoral liposomal radioactivity distribution was obtained from 1 mm resolution pinhole collimator SPECT imaging coregistered with CT imaging of excised tumors at 20 h postinfusion. Coregistered images were used for intratumoral dosimetric and radiobiological modeling at a voxel level following extrapolation to the therapeutic analogs, {sup 186}Re/{sup 188}Re liposomes. Effective uniform dose (EUD) and tumor control probability (TCP) were used to assess therapy effectiveness and possible methods of improving upon tumor control with this radiation therapy modality. Results: Dosimetric analysis showed that average tumor absorbed doses of 8.6 Gy/MBq (318.2 Gy/mCi) and 5.7 Gy/MBq (209.1 Gy/mCi) could be delivered with this protocol of radiation delivery for {sup 186}Re/{sup 188}Re liposomes, respectively, and 37-92 MBq (1-2.5 mCi)/g tumor administered activity; however, large intratumoral absorbed dose heterogeneity, as seen in dose-volume histograms, resulted in insignificant values of EUD and TCP for achieving tumor control. It is indicated that the use of liposomes encapsulating radionuclides with higher energy beta emissions, dose escalation through increased specific activity, and increasing the number of direct tumor infusion sites improve tumor control. For larger tumors, the use of multiple infusion locations was modeled to be much more efficient, in terms of activity usage, at improving EUD and TCP to achieve a tumoricidal effect. Conclusions: Direct intratumoral infusion of beta-emitting radionuclide encapsulated liposomes shows promise for cancer therapy by achieving large focally delivered tumor doses. However, the results of this work also indicate that average tumor dose may underestimate tumoricidal effect due to substantial heterogeneity in intratumoral liposomal radionuclide distributions. The resulting intratumoral distribution of liposomes following infusion should be taken into account in treatment planning and evaluation in a clinical setting for an optimal cancer therapy.« less

Development of a primary standard for absorbed dose from unsealed radionuclide solutions

NASA Astrophysics Data System (ADS)

Billas, I.; Shipley, D.; Galer, S.; Bass, G.; Sander, T.; Fenwick, A.; Smyth, V.

2016-12-01

Currently, the determination of the internal absorbed dose to tissue from an administered radionuclide solution relies on Monte Carlo (MC) calculations based on published nuclear decay data, such as emission probabilities and energies. In order to validate these methods with measurements, it is necessary to achieve the required traceability of the internal absorbed dose measurements of a radionuclide solution to a primary standard of absorbed dose. The purpose of this work was to develop a suitable primary standard. A comparison between measurements and calculations of absorbed dose allows the validation of the internal radiation dose assessment methods. The absorbed dose from an yttrium-90 chloride (90YCl) solution was measured with an extrapolation chamber. A phantom was developed at the National Physical Laboratory (NPL), the UK’s National Measurement Institute, to position the extrapolation chamber as closely as possible to the surface of the solution. The performance of the extrapolation chamber was characterised and a full uncertainty budget for the absorbed dose determination was obtained. Absorbed dose to air in the collecting volume of the chamber was converted to absorbed dose at the centre of the radionuclide solution by applying a MC calculated correction factor. This allowed a direct comparison of the analytically calculated and experimentally determined absorbed dose of an 90YCl solution. The relative standard uncertainty in the measurement of absorbed dose at the centre of an 90YCl solution with the extrapolation chamber was found to be 1.6% (k  =  1). The calculated 90Y absorbed doses from published medical internal radiation dose (MIRD) and radiation dose assessment resource (RADAR) data agreed with measurements to within 1.5% and 1.4%, respectively. This study has shown that it is feasible to use an extrapolation chamber for performing primary standard absorbed dose measurements of an unsealed radionuclide solution. Internal radiation dose assessment methods based on MIRD and RADAR data for 90Y have been validated with experimental absorbed dose determination and they agree within the stated expanded uncertainty (k  =  2).

Radon Exposure and the Definition of Low Doses-The Problem of Spatial Dose Distribution.

PubMed

Madas, Balázs G

2016-07-01

Investigating the health effects of low doses of ionizing radiation is considered to be one of the most important fields in radiological protection research. Although the definition of low dose given by a dose range seems to be clear, it leaves some open questions. For example, the time frame and the target volume in which absorbed dose is measured have to be defined. While dose rate is considered in the current system of radiological protection, the same cancer risk is associated with all exposures, resulting in a given amount of energy absorbed by a single target cell or distributed among all the target cells of a given organ. However, the biological effects and so the health consequences of these extreme exposure scenarios are unlikely to be the same. Due to the heterogeneous deposition of radon progeny within the lungs, heterogeneous radiation exposure becomes a practical issue in radiological protection. While the macroscopic dose is still within the low dose range, local tissue doses on the order of Grays can be reached in the most exposed parts of the bronchial airways. It can be concluded that progress in low dose research needs not only low dose but also high dose experiments where small parts of a biological sample receive doses on the order of Grays, while the average dose over the whole sample remains low. A narrow interpretation of low dose research might exclude investigations with high relevance to radiological protection. Therefore, studies important to radiological protection should be performed in the frame of low dose research even if the applied doses do not fit in the dose range used for the definition of low doses.

Absorbed dose kernel and self-shielding calculations for a novel radiopaque glass microsphere for transarterial radioembolization.

PubMed

Church, Cody; Mawko, George; Archambault, John Paul; Lewandowski, Robert; Liu, David; Kehoe, Sharon; Boyd, Daniel; Abraham, Robert; Syme, Alasdair

2018-02-01

Radiopaque microspheres may provide intraprocedural and postprocedural feedback during transarterial radioembolization (TARE). Furthermore, the potential to use higher resolution x-ray imaging techniques as opposed to nuclear medicine imaging suggests that significant improvements in the accuracy and precision of radiation dosimetry calculations could be realized for this type of therapy. This study investigates the absorbed dose kernel for novel radiopaque microspheres including contributions of both short and long-lived contaminant radionuclides while concurrently quantifying the self-shielding of the glass network. Monte Carlo simulations using EGSnrc were performed to determine the dose kernels for all monoenergetic electron emissions and all beta spectra for radionuclides reported in a neutron activation study of the microspheres. Simulations were benchmarked against an accepted 90 Y dose point kernel. Self-shielding was quantified for the microspheres by simulating an isotropically emitting, uniformly distributed source, in glass and in water. The ratio of the absorbed doses was scored as a function of distance from a microsphere. The absorbed dose kernel for the microspheres was calculated for (a) two bead formulations following (b) two different durations of neutron activation, at (c) various time points following activation. Self-shielding varies with time postremoval from the reactor. At early time points, it is less pronounced due to the higher energies of the emissions. It is on the order of 0.4-2.8% at a radial distance of 5.43 mm with increased size from 10 to 50 μm in diameter during the time that the microspheres would be administered to a patient. At long time points, self-shielding is more pronounced and can reach values in excess of 20% near the end of the range of the emissions. Absorbed dose kernels for 90 Y, 90m Y, 85m Sr, 85 Sr, 87m Sr, 89 Sr, 70 Ga, 72 Ga, and 31 Si are presented and used to determine an overall kernel for the microspheres based on weighted activities. The shapes of the absorbed dose kernels are dominated at short times postactivation by the contributions of 70 Ga and 72 Ga. Following decay of the short-lived contaminants, the absorbed dose kernel is effectively that of 90 Y. After approximately 1000 h postactivation, the contributions of 85 Sr and 89 Sr become increasingly dominant, though the absorbed dose-rate around the beads drops by roughly four orders of magnitude. The introduction of high atomic number elements for the purpose of increasing radiopacity necessarily leads to the production of radionuclides other than 90 Y in the microspheres. Most of the radionuclides in this study are short-lived and are likely not of any significant concern for this therapeutic agent. The presence of small quantities of longer lived radionuclides will change the shape of the absorbed dose kernel around a microsphere at long time points postadministration when activity levels are significantly reduced. © 2017 American Association of Physicists in Medicine.

Absorbed dose thresholds and absorbed dose rate limitations for studies of electron radiation effects on polyetherimides

NASA Technical Reports Server (NTRS)

Long, Edward R., Jr.; Long, Sheila Ann T.; Gray, Stephanie L.; Collins, William D.

1989-01-01

The threshold values of total absorbed dose for causing changes in tensile properties of a polyetherimide film and the limitations of the absorbed dose rate for accelerated-exposure evaluation of the effects of electron radiation in geosynchronous orbit were studied. Total absorbed doses from 1 kGy to 100 MGy and absorbed dose rates from 0.01 MGy/hr to 100 MGy/hr were investigated, where 1 Gy equals 100 rads. Total doses less than 2.5 MGy did not significantly change the tensile properties of the film whereas doses higher than 2.5 MGy significantly reduced elongation-to-failure. There was no measurable effect of the dose rate on the tensile properties for accelerated electron exposures.

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

Bronskill, M.J.

The spatial distribution of radioactivity in the injection site, and its rate of clearance, have been measured in patients undergoing various types of interstitial radiocolloid lymphoscintigraphy using 99mTc-antimony sulfide colloid. The clearance of radioactivity from the injection site, and the expansion with time of the localized radioactivity vary considerably for different sites of injection. Maximum absorbed dose estimates of 45.6 rads to the center of the injection site (rectus sheath) and 21 rads to individual lymph nodes have been calculated for patients undergoing internal mammary lymphoscintigraphy with 450 mu Ci injected radioactivity. Absorbed dose estimates for finger web, toe web,more » and perianal injection sites are also presented.« less

Effects of body habitus on internal radiation dose calculations using the 5-year-old anthropomorphic male models.

PubMed

Xie, Tianwu; Kuster, Niels; Zaidi, Habib

2017-07-13

Computational phantoms are commonly used in internal radiation dosimetry to assess the amount and distribution pattern of energy deposited in various parts of the human body from different internal radiation sources. Radiation dose assessments are commonly performed on predetermined reference computational phantoms while the argument for individualized patient-specific radiation dosimetry exists. This study aims to evaluate the influence of body habitus on internal dosimetry and to quantify the uncertainties in dose estimation correlated with the use of fixed reference models. The 5-year-old IT'IS male phantom was modified to match target anthropometric parameters, including body weight, body height and sitting height/stature ratio (SSR), determined from reference databases, thus enabling the creation of 125 5-year-old habitus-dependent male phantoms with 10th, 25th, 50th, 75th and 90th percentile body morphometries. We evaluated the absorbed fractions and the mean absorbed dose to the target region per unit cumulative activity in the source region (S-values) of F-18 in 46 source regions for the generated 125 anthropomorphic 5-year-old hybrid male phantoms using the Monte Carlo N-Particle eXtended general purpose Monte Carlo transport code and calculated the absorbed dose and effective dose of five 18 F-labelled radiotracers for children of various habitus. For most organs, the S-value of F-18 presents stronger statistical correlations with body weight, standing height and sitting height than BMI and SSR. The self-absorbed fraction and self-absorbed S-values of F-18 and the absorbed dose and effective dose of 18 F-labelled radiotracers present with the strongest statistical correlations with body weight. For 18 F-Amino acids, 18 F-Brain receptor substances, 18 F-FDG, 18 F-L-DOPA and 18 F-FBPA, the mean absolute effective dose differences between phantoms of different habitus and fixed reference models are 11.4%, 11.3%, 10.8%, 13.3% and 11.4%, respectively. Total body weight, standing height and sitting height have considerable effects on human internal dosimetry. Radiation dose calculations for individual subjects using the most closely matched habitus-dependent computational phantom should be considered as an alternative to improve the accuracy of the estimates.

Effects of body habitus on internal radiation dose calculations using the 5-year-old anthropomorphic male models

NASA Astrophysics Data System (ADS)

Xie, Tianwu; Kuster, Niels; Zaidi, Habib

2017-08-01

Computational phantoms are commonly used in internal radiation dosimetry to assess the amount and distribution pattern of energy deposited in various parts of the human body from different internal radiation sources. Radiation dose assessments are commonly performed on predetermined reference computational phantoms while the argument for individualized patient-specific radiation dosimetry exists. This study aims to evaluate the influence of body habitus on internal dosimetry and to quantify the uncertainties in dose estimation correlated with the use of fixed reference models. The 5-year-old IT’IS male phantom was modified to match target anthropometric parameters, including body weight, body height and sitting height/stature ratio (SSR), determined from reference databases, thus enabling the creation of 125 5-year-old habitus-dependent male phantoms with 10th, 25th, 50th, 75th and 90th percentile body morphometries. We evaluated the absorbed fractions and the mean absorbed dose to the target region per unit cumulative activity in the source region (S-values) of F-18 in 46 source regions for the generated 125 anthropomorphic 5-year-old hybrid male phantoms using the Monte Carlo N-Particle eXtended general purpose Monte Carlo transport code and calculated the absorbed dose and effective dose of five 18F-labelled radiotracers for children of various habitus. For most organs, the S-value of F-18 presents stronger statistical correlations with body weight, standing height and sitting height than BMI and SSR. The self-absorbed fraction and self-absorbed S-values of F-18 and the absorbed dose and effective dose of 18F-labelled radiotracers present with the strongest statistical correlations with body weight. For 18F-Amino acids, 18F-Brain receptor substances, 18F-FDG, 18F-L-DOPA and 18F-FBPA, the mean absolute effective dose differences between phantoms of different habitus and fixed reference models are 11.4%, 11.3%, 10.8%, 13.3% and 11.4%, respectively. Total body weight, standing height and sitting height have considerable effects on human internal dosimetry. Radiation dose calculations for individual subjects using the most closely matched habitus-dependent computational phantom should be considered as an alternative to improve the accuracy of the estimates.

Fine-resolution voxel S values for constructing absorbed dose distributions at variable voxel size.

PubMed

Dieudonné, Arnaud; Hobbs, Robert F; Bolch, Wesley E; Sgouros, George; Gardin, Isabelle

2010-10-01

This article presents a revised voxel S values (VSVs) approach for dosimetry in targeted radiotherapy, allowing dose calculation for any voxel size and shape of a given SPECT or PET dataset. This approach represents an update to the methodology presented in MIRD pamphlet no. 17. VSVs were generated in soft tissue with a fine spatial sampling using the Monte Carlo (MC) code MCNPX for particle emissions of 9 radionuclides: (18)F, (90)Y, (99m)Tc, (111)In, (123)I, (131)I, (177)Lu, (186)Re, and (201)Tl. A specific resampling algorithm was developed to compute VSVs for desired voxel dimensions. The dose calculation was performed by convolution via a fast Hartley transform. The fine VSVs were calculated for cubic voxels of 0.5 mm for electrons and 1.0 mm for photons. Validation studies were done for (90)Y and (131)I VSV sets by comparing the revised VSV approach to direct MC simulations. The first comparison included 20 spheres with different voxel sizes (3.8-7.7 mm) and radii (4-64 voxels) and the second comparison a hepatic tumor with cubic voxels of 3.8 mm. MC simulations were done with MCNPX for both. The third comparison was performed on 2 clinical patients with the 3D-RD (3-Dimensional Radiobiologic Dosimetry) software using the EGSnrc (Electron Gamma Shower National Research Council Canada)-based MC implementation, assuming a homogeneous tissue-density distribution. For the sphere model study, the mean relative difference in the average absorbed dose was 0.20% ± 0.41% for (90)Y and -0.36% ± 0.51% for (131)I (n = 20). For the hepatic tumor, the difference in the average absorbed dose to tumor was 0.33% for (90)Y and -0.61% for (131)I and the difference in average absorbed dose to the liver was 0.25% for (90)Y and -1.35% for (131)I. The comparison with the 3D-RD software showed an average voxel-to-voxel dose ratio between 0.991 and 0.996. The calculation time was below 10 s with the VSV approach and 50 and 15 h with 3D-RD for the 2 clinical patients. This new VSV approach enables the calculation of absorbed dose based on a SPECT or PET cumulated activity map, with good agreement with direct MC methods, in a faster and more clinically compatible manner.

Dose distribution for dental cone beam CT and its implication for defining a dose index

PubMed Central

Pauwels, R; Theodorakou, C; Walker, A; Bosmans, H; Jacobs, R; Horner, K; Bogaerts, R

2012-01-01

Objectives To characterize the dose distribution for a range of cone beam CT (CBCT) units, investigating different field of view sizes, central and off-axis geometries, full or partial rotations of the X-ray tube and different clinically applied beam qualities. The implications of the dose distributions on the definition and practicality of a CBCT dose index were assessed. Methods Dose measurements on CBCT devices were performed by scanning cylindrical head-size water and polymethyl methacrylate phantoms, using thermoluminescent dosemeters, a small-volume ion chamber and radiochromic films. Results It was found that the dose distribution can be asymmetrical for dental CBCT exposures throughout a homogeneous phantom, owing to an asymmetrical positioning of the isocentre and/or partial rotation of the X-ray source. Furthermore, the scatter tail along the z-axis was found to have a distinct shape, generally resulting in a strong drop (90%) in absorbed dose outside the primary beam. Conclusions There is no optimal dose index available owing to the complicated exposure geometry of CBCT and the practical aspects of quality control measurements. Practical validation of different possible dose indices is needed, as well as the definition of conversion factors to patient dose. PMID:22752320

Pergolide: multiple-dose pharmacokinetics in patients with mild to moderate Parkinson disease.

PubMed

Thalamas, Claire; Rajman, Iris; Kulisevsky, Jaime; Lledó, Alberto; Mackie, Alison E; Blin, Olivier; Gillespie, Todd A; Seger, Mary; Rascol, Olivier

2005-01-01

The primary objective of this study was to describe the pharmacokinetics of oral pergolide in patients with mild to moderate Parkinson disease using a new high-performance liquid chromatography-tandem mass spectrometry assay. A secondary objective was to investigate the relationship between plasma concentrations and efficacy. Fourteen patients with a diagnosis of Parkinson disease completed this multicenter, open-label, dose-escalating study. Pergolide was administered for 58 days, using increasing daily doses from 0.05 mg daily up to 1 mg three times daily and then tapering the dose. The steady-state pharmacokinetic profile and motor score were determined at dose levels of 0.25, 0.5, and 1 mg three times a day and during elimination after the last dose. Pergolide was absorbed with a median time to maximum concentration of 2 to 3 hours across the dose range. Systemic exposure appeared to increase proportionally with dose over the range of 0.25 to 1 mg three times daily within a patient, but there was a large variability in exposures between patients (interpatient coefficients of variation were 56.4% for the area under the curve). Pergolide was widely distributed (volume of distribution, approximately 14,000 L) and was eliminated with a mean half-life of 21 hours. Motor scores improved as both peak plasma pergolide concentrations and exposure increased. No unexpected safety concerns were identified. Pergolide is absorbed relatively quickly into the systemic circulation, has a large apparent volume of distribution, and has a relatively long half-life (mean, 21 hours). This prolonged half-life is of particular interest, given the current hypothesis that more continuous dopaminergic receptor stimulation may reduce motor complications in patients with Parkinson disease.

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

Soundy, R.G.; Simpson, J.D.; Ross, H.M.

The absorbed radiation dose that would result from the oral or intravenous administration of SeHCAT (23-(/sup 75/Se)selena-25-homotaurocholate) has been calculated using the MIRD tables and formulas and data from measurements of whole-body distribution and from long-term whole-body counting in rats, mice, and man. When SeHCAT is administered to normal subjects, the gallbladder is the critical organ, receiving 12 mrad (oral dose) or 22 mrad (i.v.) per microcurie. The whole-body dose is 1 mrad/..mu..Ci, whatever the route of administration. In severe hepatic failure the liver might receive 200 mrad/..mu..Ci. The activity likely to be used in routine clinical practice is 10more » ..mu..Ci. Where a whole-body counter is used, an activity of 1 ..mu..Ci has proved adequate. Even at an administered activity of 25 ..mu..Ci, the absorbed dose is small compared with established techniques of investigating the gastrointestinal tract.« less

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

Soundy, R.G.; Simpson, J.D.; Ross, H.M.

The absorbed radiation dose that would result from the oral or intravenous administration of SeHCAT (23-(75Se)selena-25-homotaurocholate) has been calculated using the MIRD tables and formulas and data from measurements of whole-body distribution and from long-term whole-body counting in rats, mice, and man. When SeHCAT is administered to normal subjects, the gallbladder is the critical organ, receiving 12 mrad (oral dose) or 22 mrad (i.v.) per microcurie. The whole-body dose is 1 mrad/microCi, whatever the route of administration. In severe hepatic failure the liver might receive 200 mrad/microCi. The activity likely to be used in routine clinical practice is 10 microCi.more » Where a whole-body counter is used, an activity of 1 microCi has proved adequate. Even at an administered activity of 25 microCi, the absorbed dose is small compared with established techniques of investigating the gastrointestinal tract.« less

Neutron production from beam-modifying devices in a modern double scattering proton therapy beam delivery system

PubMed Central

Pérez-Andújar, Angélica; Newhauser, Wayne D; DeLuca, Paul M

2014-01-01

In this work the neutron production in a passive beam delivery system was investigated. Secondary particles including neutrons are created as the proton beam interacts with beam shaping devices in the treatment head. Stray neutron exposure to the whole body may increase the risk that the patient develops a radiogenic cancer years or decades after radiotherapy. We simulated a passive proton beam delivery system with double scattering technology to determine the neutron production and energy distribution at 200 MeV proton energy. Specifically, we studied the neutron absorbed dose per therapeutic absorbed dose, the neutron absorbed dose per source particle and the neutron energy spectrum at various locations around the nozzle. We also investigated the neutron production along the nozzle's central axis. The absorbed doses and neutron spectra were simulated with the MCNPX Monte Carlo code. The simulations revealed that the range modulation wheel (RMW) is the most intense neutron source of any of the beam spreading devices within the nozzle. This finding suggests that it may be helpful to refine the design of the RMW assembly, e.g., by adding local shielding, to suppress neutron-induced damage to components in the nozzle and to reduce the shielding thickness of the treatment vault. The simulations also revealed that the neutron dose to the patient is predominated by neutrons produced in the field defining collimator assembly, located just upstream of the patient. PMID:19147903

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

Li, Xinhua; Zhang, Da; Liu, Bob, E-mail: bliu7@mgh.harvard.edu

Purpose: The knowledge of longitudinal dose distribution provides the most direct view of the accumulated dose in computed tomography (CT) scanning. The purpose of this work was to perform a comprehensive study of dose distribution width and energy absorption with a wide range of subject sizes and beam irradiated lengths. Methods: Cumulative dose distribution along the z-axis was calculated based on the previously published CT dose equilibration data by Li, Zhang, and Liu [Med. Phys. 40, 031903 (10pp.) (2013)] and a mechanism for computing dose on axial lines by Li, Zhang, and Liu [Med. Phys. 39, 5347–5352 (2012)]. Full widthmore » at half maximum (FWHM), full width at tenth maximum (FWTM), the total energy (E) absorbed in a small cylinder of unit mass per centimeter square about the central or peripheral axis, and the energy (E{sub in}) absorbed inside irradiated length (L) were subsequently extracted from the dose distribution. Results: Extensive results of FWHM, FWTM, and E{sub in}/E were presented on the central and peripheral axes of infinitely long PMMA (diameters 6–50 cm) and water (diameters 6–55 cm) cylinders with L < 100 cm. FWHM was greater than the primary beam width only on the central axes of large phantoms and also with L ranging from a few centimeter to about 33 cm. FWTM generally increased with phantom diameter, and could be up to 32 cm longer than irradiated length, depending on L, phantom diameter and axis, but was insensitive to phantom material (PMMA or water). E{sub in}/E increased with L and asymptotically approached unity for large L. As phantom diameter increased, E{sub in}/E generally decreased, but asymptotically approached constant levels on the peripheral axes of large phantoms. A heuristic explanation of dose distribution width results was presented. Conclusions: This study enables the reader to gain a comprehensive view of dose distribution width and energy absorption and provides useful data for estimating doses to organs inside or beyond the irradiated region. The dose length product (DLP) presented by CT scanners is equal to neither E nor E{sub in}. Both E and E{sub in} can be evaluated using the equations and results presented in this paper and are robust with both constant and variable tube current scanning techniques.« less

Treatment planning for internal emitter therapy: Methods, applications and clinical implications

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

Sgouros, G.

1999-01-01

Treatment planning involves three basic steps: (1) a procedure must be devised that will provide the most relevant information, (2) the procedure must be applied and (3) the resulting information must be translated into a definition of the optimum implementation. There are varying degrees of treatment planning that may be implemented in internal emitter therapy. As in chemotherapy, the information from a Phase 1 study may be used to treat patients based upon body surface area. If treatment planning is included on a patient-specific basis, a pretherapy, trace-labeled, administration of the radiopharmaceutical is generally required. The data collected following themore » tracer dose may range from time-activity curves of blood and whole-body for use in blood, marrow or total body absorbed dose estimation to patient imaging for three-dimensional internal emitter dosimetry. The most ambitious approach requires a three-dimensional set of images representing radionuclide distribution (SPECT or PET) and a corresponding set of images representing anatomy (CT or MRI). The absorbed dose (or dose-rate) distribution may be obtained by convolution of a point kernel with the radioactivity distribution or by direct Monte Carlo calculation. A critical requirement for both techniques is the development of an overall structure that makes it possible, in a routine manner, to input the images, to identify the structures of interest and to display the results of the dose calculations in a clinically relevant manner. 52 refs., 4 figs., 1 tab.« 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.

Development of computational pregnant female and fetus models and assessment of radiation dose from positron-emitting tracers.

PubMed

Xie, Tianwu; Zaidi, Habib

2016-12-01

Molecular imaging using PET and hybrid (PET/CT and PET/MR) modalities nowadays plays a pivotal role in the clinical setting for diagnosis and staging, treatment response monitoring, and radiation therapy treatment planning of a wide range of oncologic malignancies. The developing embryo/fetus presents a high sensitivity to ionizing radiation. Therefore, estimation of the radiation dose delivered to the embryo/fetus and pregnant patients from PET examinations to assess potential radiation risks is highly praised. We constructed eight embryo/fetus models at various gestation periods with 25 identified tissues according to reference data recommended by the ICRP publication 89 representing the anatomy of the developing embryo/fetus. The developed embryo/fetus models were integrated into realistic anthropomorphic computational phantoms of the pregnant female and used for estimating, using Monte Carlo calculations, S-values of common positron-emitting radionuclides, organ absorbed dose, and effective dose of a number of positron-emitting labeled radiotracers. The absorbed dose is nonuniformly distributed in the fetus. The absorbed dose of the kidney and liver of the 8-week-old fetus are about 47.45 % and 44.76 % higher than the average absorbed dose of the fetal total body for all investigated radiotracers. For 18 F-FDG, the fetal effective doses are 2.90E-02, 3.09E-02, 1.79E-02, 1.59E-02, 1.47E-02, 1.40E-02, 1.37E-02, and 1.27E-02 mSv/MBq at the 8th, 10th, 15th, 20th, 25th, 30th, 35th, and 38th weeks of gestation, respectively. The developed pregnant female/fetus models matching the ICRP reference data can be exploited by dedicated software packages for internal and external dose calculations. The generated S-values will be useful to produce new standardized dose estimates to pregnant patients and embryo/fetus from a variety of positron-emitting labeled radiotracers.

Scattered radiation doses absorbed by technicians at different distances from X-ray exposure: Experiments on prosthesis.

PubMed

Chiang, Hsien-Wen; Liu, Ya-Ling; Chen, Tou-Rong; Chen, Chun-Lon; Chiang, Hsien-Jen; Chao, Shin-Yu

2015-01-01

This work aimed to investigate the spatial distribution of scattered radiation doses induced by exposure to the portable X-ray, the C-arm machine, and to simulate the radiologist without a shield of lead clothing, radiation doses absorbed by medical staff at 2 m from the central exposure point. With the adoption of the Rando Phantom, several frequently X-rayed body parts were exposed to X-ray radiation, and the scattered radiation doses were measured by ionization chamber dosimeters at various angles from the patient. Assuming that the central point of the X-ray was located at the belly button, five detection points were distributed in the operation room at 1 m above the ground and 1-2 m from the central point horizontally. The radiation dose measured at point B was the lowest, and the scattered radiation dose absorbed by the prosthesis from the X-ray's vertical projection was 0.07 ±0.03 μGy, which was less than the background radiation levels. The Fluke biomedical model 660-5DE (400 cc) and 660-3DE (4 cc) ion chambers were used to detect air dose at a distance of approximately two meters from the central point. The AP projection radiation doses at point B was the lowest (0.07±0.03 μGy) and the radiation doses at point D was the highest (0.26±0.08 μGy) .Only taking the vertical projection into account, the radiation doses at point B was the lowest (0.52 μGy), and the radiation doses at point E was the highest (4 μGy).The PA projection radiation at point B was the lowest (0.36 μGy) and the radiation doses at point E was the highest(2.77 μGy), occupying 10-32% of the maximum doses. The maximum dose in five directions was nine times to the minimum dose. When the PX and the C-arm machine were used, the radiation doses at a distance of 2 m were attenuated to the background radiation level. The radiologist without a lead shield should stand at point B of patient's feet. Accordingly, teaching materials on radiation safety for radiological interns and clinical technicians were formulated.

(⁹⁹m)Tc-MAA overestimates the absorbed dose to the lungs in radioembolization: a quantitative evaluation in patients treated with ¹⁶⁶Ho-microspheres.

PubMed

Elschot, Mattijs; Nijsen, Johannes F W; Lam, Marnix G E H; Smits, Maarten L J; Prince, Jip F; Viergever, Max A; van den Bosch, Maurice A A J; Zonnenberg, Bernard A; de Jong, Hugo W A M

2014-10-01

Radiation pneumonitis is a rare but serious complication of radioembolic therapy of liver tumours. Estimation of the mean absorbed dose to the lungs based on pretreatment diagnostic (99m)Tc-macroaggregated albumin ((99m)Tc-MAA) imaging should prevent this, with administered activities adjusted accordingly. The accuracy of (99m)Tc-MAA-based lung absorbed dose estimates was evaluated and compared to absorbed dose estimates based on pretreatment diagnostic (166)Ho-microsphere imaging and to the actual lung absorbed doses after (166)Ho radioembolization. This prospective clinical study included 14 patients with chemorefractory, unresectable liver metastases treated with (166)Ho radioembolization. (99m)Tc-MAA-based and (166)Ho-microsphere-based estimation of lung absorbed doses was performed on pretreatment diagnostic planar scintigraphic and SPECT/CT images. The clinical analysis was preceded by an anthropomorphic torso phantom study with simulated lung shunt fractions of 0 to 30 % to determine the accuracy of the image-based lung absorbed dose estimates after (166)Ho radioembolization. In the phantom study, (166)Ho SPECT/CT-based lung absorbed dose estimates were more accurate (absolute error range 0.1 to -4.4 Gy) than (166)Ho planar scintigraphy-based lung absorbed dose estimates (absolute error range 9.5 to 12.1 Gy). Clinically, the actual median lung absorbed dose was 0.02 Gy (range 0.0 to 0.7 Gy) based on posttreatment (166)Ho-microsphere SPECT/CT imaging. Lung absorbed doses estimated on the basis of pretreatment diagnostic (166)Ho-microsphere SPECT/CT imaging (median 0.02 Gy, range 0.0 to 0.4 Gy) were significantly better predictors of the actual lung absorbed doses than doses estimated on the basis of (166)Ho-microsphere planar scintigraphy (median 10.4 Gy, range 4.0 to 17.3 Gy; p < 0.001), (99m)Tc-MAA SPECT/CT imaging (median 2.5 Gy, range 1.2 to 12.3 Gy; p < 0.001), and (99m)Tc-MAA planar scintigraphy (median 5.5 Gy, range 2.3 to 18.2 Gy; p < 0.001). In clinical practice, lung absorbed doses are significantly overestimated by pretreatment diagnostic (99m)Tc-MAA imaging. Pretreatment diagnostic (166)Ho-microsphere SPECT/CT imaging accurately predicts lung absorbed doses after (166)Ho radioembolization.

Dose rate effect of pulsed electron beam on micronucleus frequency in human peripheral blood lymphocytes.

PubMed

Acharya, Santhosh; Sanjeev, Ganesh; Bhat, Nagesh N; Narayana, Yerol

2010-03-01

The micronucleus assay in human peripheral blood lymphocytes is a sensitive indicator of radiation damage and could serve as a biological dosimeter in evaluating suspected overexposure to ionising radiation. Micronucleus (MN) frequency as a measure of chromosomal damage has also extensively been employed to quantify the effects of radiation dose rate on biological systems. Here we studied the effects of 8 MeV pulsed electron beam emitted by Microtron electron accelerator on MN induction at dose rates between 35 Gy min-1 and 352.5 Gy min-1. These dose rates were achieved by varying the pulse repetition rate (PRR). Fricke dosimeter was employed to measure the absorbed dose at different PRR and to ensure uniform dose distribution of the electron beam. To study the dose rate effect, blood samples were irradiated to an absorbed dose of (4.7+/-0.2) Gy at different rates and cytogenetic damage was quantified using the micronucleus assay. The obtained MN frequency showed no dose rate dependence within the studied dose rate range. Our earlier dose effect study using 8 MeV electrons revealed that the response of MN was linear-quadratic. Therefore, in the event of an accident, dose estimation can be made using linear-quadratic dose response parameters, without adding dose rate as a correction factor.

PHITS simulations of absorbed dose out-of-field and neutron energy spectra for ELEKTA SL25 medical linear accelerator.

PubMed

Puchalska, Monika; Sihver, Lembit

2015-06-21

Monte Carlo (MC) based calculation methods for modeling photon and particle transport, have several potential applications in radiotherapy. An essential requirement for successful radiation therapy is that the discrepancies between dose distributions calculated at the treatment planning stage and those delivered to the patient are minimized. It is also essential to minimize the dose to radiosensitive and critical organs. With MC technique, the dose distributions from both the primary and scattered photons can be calculated. The out-of-field radiation doses are of particular concern when high energy photons are used, since then neutrons are produced both in the accelerator head and inside the patients. Using MC technique, the created photons and particles can be followed and the transport and energy deposition in all the tissues of the patient can be estimated. This is of great importance during pediatric treatments when minimizing the risk for normal healthy tissue, e.g. secondary cancer. The purpose of this work was to evaluate 3D general purpose PHITS MC code efficiency as an alternative approach for photon beam specification. In this study, we developed a model of an ELEKTA SL25 accelerator and used the transport code PHITS for calculating the total absorbed dose and the neutron energy spectra infield and outside the treatment field. This model was validated against measurements performed with bubble detector spectrometers and Boner sphere for 18 MV linacs, including both photons and neutrons. The average absolute difference between the calculated and measured absorbed dose for the out-of-field region was around 11%. Taking into account a simplification for simulated geometry, which does not include any potential scattering materials around, the obtained result is very satisfactorily. A good agreement between the simulated and measured neutron energy spectra was observed while comparing to data found in the literature.

PHITS simulations of absorbed dose out-of-field and neutron energy spectra for ELEKTA SL25 medical linear accelerator

NASA Astrophysics Data System (ADS)

Puchalska, Monika; Sihver, Lembit

2015-06-01

Monte Carlo (MC) based calculation methods for modeling photon and particle transport, have several potential applications in radiotherapy. An essential requirement for successful radiation therapy is that the discrepancies between dose distributions calculated at the treatment planning stage and those delivered to the patient are minimized. It is also essential to minimize the dose to radiosensitive and critical organs. With MC technique, the dose distributions from both the primary and scattered photons can be calculated. The out-of-field radiation doses are of particular concern when high energy photons are used, since then neutrons are produced both in the accelerator head and inside the patients. Using MC technique, the created photons and particles can be followed and the transport and energy deposition in all the tissues of the patient can be estimated. This is of great importance during pediatric treatments when minimizing the risk for normal healthy tissue, e.g. secondary cancer. The purpose of this work was to evaluate 3D general purpose PHITS MC code efficiency as an alternative approach for photon beam specification. In this study, we developed a model of an ELEKTA SL25 accelerator and used the transport code PHITS for calculating the total absorbed dose and the neutron energy spectra infield and outside the treatment field. This model was validated against measurements performed with bubble detector spectrometers and Boner sphere for 18 MV linacs, including both photons and neutrons. The average absolute difference between the calculated and measured absorbed dose for the out-of-field region was around 11%. Taking into account a simplification for simulated geometry, which does not include any potential scattering materials around, the obtained result is very satisfactorily. A good agreement between the simulated and measured neutron energy spectra was observed while comparing to data found in the literature.

Design and Calibration of a X-Ray Millibeam

DTIC Science & Technology

2005-12-01

developed for use in Fricke dosimetry , parallel-plate ionization chambers, Lithium Fluoride thermoluminescent dosimetry ( TLD ), and EBT GafChromic...thermoluminescent dosimetry ( TLD ), and EBT GafChromic film to characterize the spatial distribution and accuracy of the doses produced by the Faxitron. A...absorbed dose calibration factors for use in Fricke dosimetry , parallel-plate ionization chambers, Lithium Fluoride (LiF) TLD , and EBT GafChromic film. The

Absorbed Dose Determination Using Experimental and Analytical Predictions of X-Ray Spectra

NASA Technical Reports Server (NTRS)

Edwards, D. L.; Carruth, Ralph (Technical Monitor)

2001-01-01

Electron beam welding in a vacuum is a technology that NASA is investigating as a joining technique for manufacture of space structures. This investigation characterizes the x-ray environment due to operation of an in-vacuum electron beam welding tool and provides recommendations for adequate shielding for astronauts performing the in-vacuum electron beam welding. NASA, in a joint venture with the Russian Space Agency, was scheduled to perform a series of welding in space experiments on board the U.S. Space Shuttle. This series of experiments was named the international space welding experiment (ISWE). The hardware associated with the ISWE was leased to NASA by the Paton Welding Institute (PWI) in Ukraine for ground-based welding experiments in preparation for flight. Two ground tests were scheduled, using the ISWE electron beam welding tool, to characterize the radiation exposure to an astronaut during the operation of the ISWE. These radiation exposure tests used thermoluminescence dosimeters (TLD's) shielded with material currently used by astronauts during extravehicular activities to measure the radiation dose. The TLD's were exposed to x-ray radiation generated by operation of the ISWE in-vacuum electron beam welding tool. This investigation was the first known application of TLD's to measure absorbed dose from x rays of energy less than 10 keV. The ISWE hardware was returned to Ukraine before the issue of adequate shielding for the astronauts was completely verified. Therefore, alternate experimental and analytical methods were developed to measure and predict the x-ray spectral and intensity distribution generated by ISWE electron beam impact with metal. These x-ray spectra were normalized to an equivalent ISWE exposure, then used to calculate the absorbed radiation dose to astronauts. These absorbed dose values were compared to TLD measurements obtained during actual operation of the ISWE in-vacuum electron beam welding tool. The calculated absorbed dose values were found to be in agreement with the measured TLD values.

WE-AB-204-12: Dosimetry at the Sub-Cellular Scale of Auger-Electron Emitter 99m-Tc in a Mouse Single Thyroid Follicle Model

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

Taborda, A; Benabdallah, N; Desbree, A

2015-06-15

Purpose: To perform a dosimetry study at the sub-cellular scale of Auger-electron emitter 99m-Tc using a mouse single thyroid cellular model to investigate the contribution of the 99m-Tc Auger-electrons to the absorbed dose and possible link to the thyroid stunning in in vivo experiments in mice, recently reported in literature. Methods: The simulation of S-values for Auger-electron emitting radionuclides was performed using both the recent MCNP6 software and the Geant4-DNA extension of the Geant4 toolkit. The dosimetric calculations were validated through comparison with results from literature, using a simple model of a single cell consisting of two concentric spheres ofmore » unit density water and for six Auger-electron emitting radionuclides. Furthermore, the S-values were calculated using a single thyroid follicle model for uniformly distributed 123-I and 125-I radionuclides and compared with published S-values. After validation, the simulation of the S-values was performed for the 99m-Tc radionuclide within the several mouse thyroid follicle cellular compartments, considering the radiative and non-radiative transitions of the 99m-Tc radiation spectrum. Results: The calculated S-values using MCNP6 are in good agreement with the results from literature, validating its use for the 99m-Tc S-values calculations. The most significant absorbed dose corresponds to the case where the radionuclide is uniformly distributed in the follicular cell’s nucleus, with a S-value of 7.8 mGy/disintegration, due mainly to the absorbed Auger-electrons. The results show that, at a sub-cellular scale, the emitted X-rays and gamma particles do not contribute significantly to the absorbed dose. Conclusion: In this work, MCNP6 was validated for dosimetric studies at the sub-cellular scale. It was shown that the contribution of the Auger-electrons to the absorbed dose is important at this scale compared to the emitted photons’ contribution and can’t be neglected. The obtained S-values of Auger-electron emitting 99m-Tc radionuclide will be presented and discussed.« less

Estimated human absorbed dose of a new (153)Sm bone seeking agent based on biodistribution data in mice: Comparison with (153)Sm-EDTMP.

PubMed

Yousefnia, Hassan; Zolghadri, Samaneh

2015-11-01

The main goal in radiotherapy is to deliver the absorbed dose within the target organs in highest possible amount, while the absorbed dose of the other organs, especially the critical organs, should be kept as low as possible. In this work, the absorbed dose to human organs for a new (153)Sm bone-seeking agent was investigated. (153)Sm-(4-{[(bis(phosphonomethyl))carbamoyl]methyl}-7,10-bis(carboxymethyl)-1,4,7,10-tetraazacyclododec-1-yl) acetic acid ((153)Sm-BPAMD) complex was successfully prepared. The biodistribution of the complex was investigated in male Syrian mice up to 48 h post injection. The human absorbed dose of the complex was estimated based on the biodistribution data of the mice by radiation absorbed dose assessment resource (RADAR) method. The target to non-target absorbed dose ratios for (153)Sm-BPAMD were compared with these ratios for (153)Sm-EDTMP. The highest absorbed dose for (153)Sm-BPAMD was observed in bone surface with 5.828 mGy/MBq. The dose ratios of the bone surface to the red marrow and to the total body for (153)Sm-BPAMD were 5.3 and 20.0, respectively, while these ratios for (153)Sm-EDTMP were 4.4 and 18.3, respectively. This means, for a given dose to the bone surface as the target organ, the red marrow (as the main critical organ) and the total body would receive lesser absorbed dose in the case of (153)Sm-BPAMD. Generally, the human absorbed dose estimation of (153)Sm-BPAMD indicated that all other tissues approximately received insignificant absorbed dose in comparison with bone surface and therefore can be regarded as a new potential agent for bone pain palliation therapy. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

MCNP simulation of radiation doses distributions in a water phantoms simulating interventional radiology patients

NASA Astrophysics Data System (ADS)

He, Wenjun; Mah, Eugene; Huda, Walter; Selby, Bayne; Yao, Hai

2011-03-01

Purpose: To investigate the dose distributions in water cylinders simulating patients undergoing Interventional Radiological examinations. Method: The irradiation geometry consisted of an x-ray source, dose-area-product chamber, and image intensifier as currently used in Interventional Radiology. Water cylinders of diameters ranging between 17 and 30 cm were used to simulate patients weighing between 20 and 90 kg. X-ray spectra data with peak x-ray tube voltages ranging from 60 to 120 kV were generated using XCOMP3R. Radiation dose distributions inside the water cylinder (Dw) were obtained using MCNP5. The depth dose distribution along the x-ray beam central axis was normalized to free-in-air air kerma (AK) that is incident on the phantom. Scattered radiation within the water cylinders but outside the directly irradiated region was normalized to the dose at the edge of the radiation field. The total absorbed energy to the directly irradiated volume (Ep) and indirectly irradiated volume (Es) were also determined and investigated as a function of x-ray tube voltage and phantom size. Results: At 80 kV, the average Dw/AK near the x-ray entrance point was 1.3. The ratio of Dw near the entrance point to Dw near the exit point increased from ~ 26 for the 17 cm water cylinder to ~ 290 for the 30 cm water cylinder. At 80 kV, the relative dose for a 17 cm water cylinder fell to 0.1% at 49 cm away from the central ray of the x-ray beam. For a 30 cm water cylinder, the relative dose fell to 0.1% at 53 cm away from the central ray of the x-ray beam. At a fixed x-ray tube voltage of 80 kV, increasing the water cylinder diameter from 17 to 30 cm increased the Es/(Ep+Es) ratio by about 50%. At a fixed water cylinder diameter of 24 cm, increasing the tube voltage from 60 kV to 120 kV increased the Es/(Ep+Es) ratio by about 12%. The absorbed energy from scattered radiation was between 20-30% of the total energy absorbed by the water cylinder, and was affected more by patient size than x-ray beam energy. Conclusion: MCNP offers a powerful tool to study the absorption and transmission of x-ray energy in phantoms that can be designed to represent patients undergoing Interventional Radiological procedures. This ability will permit a systematic investigation of the relationship between patient dose and diagnostic image quality, and thereby keep patient doses As Low As Reasonably Achievable (ALARA).

Prediction and Measurement of X-Ray Spectral and Intensity Distributions from Low Energy Electron Impact Sources

NASA Technical Reports Server (NTRS)

Edwards, David L.

1999-01-01

In-vacuum electron beam welding is a technology that NASA considered as a joining technique for manufacture of space structures. The interaction of energetic electrons with metal produces x-rays. The radiation exposure to astronauts performing the in-vacuum electron beam welding must be characterized and minimized to insure safe operating conditions. This investigation characterized the x-ray environment due to operation of an in-vacuum electron beam welding tool. NASA, in a joint venture with the Russian Space Agency, was scheduled to perform a series of welding in space experiments on board the United States Space Shuttle. This series of experiments was named the International Space Welding Experiment (ISWE). The hardware associated with the ISWE was leased to NASA, by the Paton Welding Institute (PWI) in Ukraine, for ground based welding experiments in preparation for flight. Two tests were scheduled, using the ISWE electron beam welding tool, to characterize the radiation exposure to an astronaut during the operation of the ISWE. These radiation exposure tests consisted of Thermoluminescence Dosimeters (TLD's) shielded with material currently used by astronauts during Extra Vehicular Activities (EVA) and exposed to x-ray radiation generated by operation of an in-vacuum electron beam welding tool. This investigation was the first known application of TLD's to measure absorbed dose from x-rays of energy less than 10 KeV. The ISWE hardware was returned to Ukraine before the issue of adequate shielding for the astronauts was verified. Therefore, alternate experimental and analytical methods were developed to measure and predict the x-ray spectral and intensity distribution generated by electron impact with metal. These x-ray spectra were used to calculate the absorbed radiation dose to astronauts. These absorbed dose values were compared to TLD measurements obtained during actual operation of the in-vacuum electron beam welding tool. The calculated absorbed dose values were found to be in good agreement with the TLD values.

Comparative Pharmacokinetics of the Organophosphorus Insecticide Chlorpyrifos and its Major Metabolites Diethylphosphate, Diethylthiophosphate and 3,5,6-Trichloro-2-pyridinol in the Rat

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

Timchalk, Chuck; Busby, Andrea L; Campbell, James A

2007-07-31

Abstract Chlorpyrifos (CPF) is a commonly used diethylphosphorothionate organophosphorus (OP) insecticide. Diethylphosphate (DEP), diethylthiophosphate (DETP) and 3,5,6-trichloro-2-pyridinol (TCPy) are products of metabolism and of environmental degradation of CPF and are routinely measured in urine as biomarkers of exposure. However, because these same chemicals can result from metabolism or by biodegradation, monitoring total urinary metabolite levels may be reflective of not only an individual’s contact with the parent pesticide, but also exposure with the metabolites, which are present in the environment. The objective of the current study was to compare the pharmacokinetics of orally administered DEP, DETP and TCPy with theirmore » kinetics following oral dosing with the parent insecticide CPF in the rat. Groups of rats were orally administered CPF, DEP, TCPy or DETP at doses of 140 μmol/kg body weight, and the time-courses of the metabolites were evaluated in blood and urine. Following oral administration, all three metabolites were well absorbed with peak blood concentrations being attained between 1-3 h post-dosing. In the case of DEP and TCPy virtually all the administered dose was recovered in the urine by 72 h post-dosing, suggesting negligible, if any, metabolism; whereas with DETP, ~50% of the orally administered dose was recovered in the urine. The CPF oral dose was likewise rapidly absorbed and metabolized to DEP, TCPy and DETP, with the distribution of metabolites in the urine followed the order: TCPy (22 ± 3 μmol) > DETP (14 ± 2 μmol) > DEP (1.4 ± 0.7 μmol). Based upon the total amount of TCPy detected in the urine a minimum of 63% of the oral CPF dose was absorbed. These studies support the hypotheses that DEP, DETP and TCPy present in the environment can be readily absorbed and eliminated in the urine of rats and potentially humans.« less

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

Yasui, Keisuke, E-mail: k.yasui.20@west-med.jp; Toshito, Toshiyuki; Omachi, Chihiro

Purpose: In the authors’ proton therapy system, the patient-specific aperture can be attached to the nozzle of spot scanning beams to shape an irradiation field and reduce lateral fall-off. The authors herein verified this system for clinical application. Methods: The authors prepared four types of patient-specific aperture systems equipped with an energy absorber to irradiate shallow regions less than 4 g/cm{sup 2}. The aperture was made of 3-cm-thick brass and the maximum water equivalent penetration to be used with this system was estimated to be 15 g/cm{sup 2}. The authors measured in-air lateral profiles at the isocenter plane and integralmore » depth doses with the energy absorber. All input data were obtained by the Monte Carlo calculation, and its parameters were tuned to reproduce measurements. The fluence of single spots in water was modeled as a triple Gaussian function and the dose distribution was calculated using a fluence dose model. The authors compared in-air and in-water lateral profiles and depth doses between calculations and measurements for various apertures of square, half, and U-shaped fields. The absolute doses and dose distributions with the aperture were then validated by patient-specific quality assurance. Measured data were obtained by various chambers and a 2D ion chamber detector array. Results: The patient-specific aperture reduced the penumbra from 30% to 70%, for example, from 34.0 to 23.6 mm and 18.8 to 5.6 mm. The calculated field width for square-shaped apertures agreed with measurements within 1 mm. Regarding patient-specific aperture plans, calculated and measured doses agreed within −0.06% ± 0.63% (mean ± SD) and 97.1% points passed the 2%-dose/2 mm-distance criteria of the γ-index on average. Conclusions: The patient-specific aperture system improved dose distributions, particularly in shallow-region plans.« less

Simplified method for creating a density-absorbed dose calibration curve for the low dose range from Gafchromic EBT3 film.

PubMed

Gotanda, Tatsuhiro; Katsuda, Toshizo; Gotanda, Rumi; Kuwano, Tadao; Akagawa, Takuya; Tanki, Nobuyoshi; Tabuchi, Akihiko; Shimono, Tetsunori; Kawaji, Yasuyuki

2016-01-01

Radiochromic film dosimeters have a disadvantage in comparison with an ionization chamber in that the dosimetry process is time-consuming for creating a density-absorbed dose calibration curve. The purpose of this study was the development of a simplified method of creating a density-absorbed dose calibration curve from radiochromic film within a short time. This simplified method was performed using Gafchromic EBT3 film with a low energy dependence and step-shaped Al filter. The simplified method was compared with the standard method. The density-absorbed dose calibration curves created using the simplified and standard methods exhibited approximately similar straight lines, and the gradients of the density-absorbed dose calibration curves were -32.336 and -33.746, respectively. The simplified method can obtain calibration curves within a much shorter time compared to the standard method. It is considered that the simplified method for EBT3 film offers a more time-efficient means of determining the density-absorbed dose calibration curve within a low absorbed dose range such as the diagnostic range.

Simplified method for creating a density-absorbed dose calibration curve for the low dose range from Gafchromic EBT3 film

PubMed Central

Gotanda, Tatsuhiro; Katsuda, Toshizo; Gotanda, Rumi; Kuwano, Tadao; Akagawa, Takuya; Tanki, Nobuyoshi; Tabuchi, Akihiko; Shimono, Tetsunori; Kawaji, Yasuyuki

2016-01-01

Radiochromic film dosimeters have a disadvantage in comparison with an ionization chamber in that the dosimetry process is time-consuming for creating a density-absorbed dose calibration curve. The purpose of this study was the development of a simplified method of creating a density-absorbed dose calibration curve from radiochromic film within a short time. This simplified method was performed using Gafchromic EBT3 film with a low energy dependence and step-shaped Al filter. The simplified method was compared with the standard method. The density-absorbed dose calibration curves created using the simplified and standard methods exhibited approximately similar straight lines, and the gradients of the density-absorbed dose calibration curves were −32.336 and −33.746, respectively. The simplified method can obtain calibration curves within a much shorter time compared to the standard method. It is considered that the simplified method for EBT3 film offers a more time-efficient means of determining the density-absorbed dose calibration curve within a low absorbed dose range such as the diagnostic range. PMID:28144120

The geomagnetically trapped radiation environment: A radiological point of view

NASA Technical Reports Server (NTRS)

Holly, F. E.

1972-01-01

The regions of naturally occurring, geomagnetically trapped radiation are briefly reviewed in terms of physical parameters such as; particle types, fluxes, spectrums, and spatial distributions. The major emphasis is placed upon a description of this environment in terms of the radiobiologically relevant parameters of absorbed dose and dose-rate and a discussion of the radiological implications in terms of the possible impact on space vehicle design and mission planning.

Review of reconstruction of radiation incident air kerma by measurement of absorbed dose in tooth enamel with EPR.

PubMed

Wieser, A

2012-03-01

Electron paramagnetic resonance dosimetry with tooth enamel has been proved to be a reliable method to determine retrospectively exposures from photon fields with minimal detectable doses of 100 mGy or lower, which is lower than achievable with cytogenetic dose reconstruction methods. For risk assessment or validating dosimetry systems for specific radiation incidents, the relevant dose from the incident has to be calculated from the total absorbed dose in enamel by subtracting additional dose contributions from the radionuclide content in teeth, natural external background radiation and medical exposures. For calculating organ doses or evaluating dosimetry systems the absorbed dose in enamel from a radiation incident has to be converted to air kerma using dose conversion factors depending on the photon energy spectrum and geometry of the exposure scenario. This paper outlines the approach to assess individual dose contributions to absorbed dose in enamel and calculate individual air kerma of a radiation incident from the absorbed dose in tooth enamel.

A radiobiological model of metastatic burden reduction for molecular radiotherapy: application to patients with bone metastases

NASA Astrophysics Data System (ADS)

Denis-Bacelar, Ana M.; Chittenden, Sarah J.; Murray, Iain; Divoli, Antigoni; McCready, V. Ralph; Dearnaley, David P.; O'Sullivan, Joe M.; Johnson, Bernadette; Flux, Glenn D.

2017-04-01

Skeletal tumour burden is a biomarker of prognosis and survival in cancer patients. This study proposes a novel method based on the linear quadratic model to predict the reduction in metastatic tumour burden as a function of the absorbed doses delivered from molecular radiotherapy treatments. The range of absorbed doses necessary to eradicate all the bone lesions and to reduce the metastatic burden was investigated in a cohort of 22 patients with bone metastases from castration-resistant prostate cancer. A metastatic burden reduction curve was generated for each patient, which predicts the reduction in metastatic burden as a function of the patient mean absorbed dose, defined as the mean of all the lesion absorbed doses in any given patient. In the patient cohort studied, the median of the patient mean absorbed dose predicted to reduce the metastatic burden by 50% was 89 Gy (interquartile range: 83-105 Gy), whilst a median of 183 Gy (interquartile range: 107-247 Gy) was found necessary to eradicate all metastases in a given patient. The absorbed dose required to eradicate all the lesions was strongly correlated with the variability of the absorbed doses delivered to multiple lesions in a given patient (r  =  0.98, P  <  0.0001). The metastatic burden reduction curves showed a potential large reduction in metastatic burden for a small increase in absorbed dose in 91% of patients. The results indicate the range of absorbed doses required to potentially obtain a significant survival benefit. The metastatic burden reduction method provides a simple tool that could be used in routine clinical practice for patient selection and to indicate the required administered activity to achieve a predicted patient mean absorbed dose and reduction in metastatic tumour burden.

Dose Assessments to the Hands of Radiopharmaceutical Workers

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

Ilas, Dan; Eckerman, Keith F; Sherbini, Sami

This paper describes the characterization of radiation doses to the hands of nuclear medicine technicians resulting from the handling of radiopharmaceuticals. Radiation monitoring using ring dosimeters indicates that finger dosimeters may overestimate or underestimate the radiation doses to the skin that are used to show compliance with applicable regulations depending on the nature of the particular procedure and the radioisotope being handled. To better understand the parameters governing the absorbed dose distributions, a detailed model of the hands was created and used in Monte Carlo simulations of selected nuclear medicine procedures. Simulations on realistic configurations typical for workers handling radiopharmaceuticalsmore » were performed for a range of energies of the source photons. The lack of charged-particle equilibrium necessitated full photon-electron coupled transport calculations. The results show that the dose to different regions of the fingers can differ substantially from the dosimeters' readings when the dosimeters are located at the base of the finger. We tried to identify consistent patterns that relate the actual dose to the dosimeter readings. These patterns depend on the specific work conditions and can be used to better assess the absorbed dose to different regions of the exposed skin.« less

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

An automated voxelized dosimetry tool for radionuclide therapy based on serial quantitative SPECT/CT imaging

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

Jackson, Price A.; Kron, Tomas; Beauregard, Jean-Mathieu

2013-11-15

Purpose: To create an accurate map of the distribution of radiation dose deposition in healthy and target tissues during radionuclide therapy.Methods: Serial quantitative SPECT/CT images were acquired at 4, 24, and 72 h for 28 {sup 177}Lu-octreotate peptide receptor radionuclide therapy (PRRT) administrations in 17 patients with advanced neuroendocrine tumors. Deformable image registration was combined with an in-house programming algorithm to interpolate pharmacokinetic uptake and clearance at a voxel level. The resultant cumulated activity image series are comprised of values representing the total number of decays within each voxel's volume. For PRRT, cumulated activity was translated to absorbed dose basedmore » on Monte Carlo-determined voxel S-values at a combination of long and short ranges. These dosimetric image sets were compared for mean radiation absorbed dose to at-risk organs using a conventional MIRD protocol (OLINDA 1.1).Results: Absorbed dose values to solid organs (liver, kidneys, and spleen) were within 10% using both techniques. Dose estimates to marrow were greater using the voxelized protocol, attributed to the software incorporating crossfire effect from nearby tumor volumes.Conclusions: The technique presented offers an efficient, automated tool for PRRT dosimetry based on serial post-therapy imaging. Following retrospective analysis, this method of high-resolution dosimetry may allow physicians to prescribe activity based on required dose to tumor volume or radiation limits to healthy tissue in individual patients.« less

Lung Dosimetry for Radioiodine Treatment Planning in the Case of Diffuse Lung Metastases

PubMed Central

Song, Hong; He, Bin; Prideaux, Andrew; Du, Yong; Frey, Eric; Kasecamp, Wayne; Ladenson, Paul W.; Wahl, Richard L.; Sgouros, George

2010-01-01

The lungs are the most frequent sites of distant metastasis in differentiated thyroid carcinoma. Radioiodine treatment planning for these patients is usually performed following the Benua– Leeper method, which constrains the administered activity to 2.96 GBq (80 mCi) whole-body retention at 48 h after administration to prevent lung toxicity in the presence of iodine-avid lung metastases. This limit was derived from clinical experience, and a dosimetric analysis of lung and tumor absorbed dose would be useful to understand the implications of this limit on toxicity and tumor control. Because of highly nonuniform lung density and composition as well as the nonuniform activity distribution when the lungs contain tumor nodules, Monte Carlo dosimetry is required to estimate tumor and normal lung absorbed dose. Reassessment of this toxicity limit is also appropriate in light of the contemporary use of recombinant thyrotropin (thyroid-stimulating hormone) (rTSH) to prepare patients for radioiodine therapy. In this work we demonstrated the use of MCNP, a Monte Carlo electron and photon transport code, in a 3-dimensional (3D) imaging–based absorbed dose calculation for tumor and normal lungs. Methods A pediatric thyroid cancer patient with diffuse lung metastases was administered 37MBq of 131I after preparation with rTSH. SPECT/CT scans were performed over the chest at 27, 74, and 147 h after tracer administration. The time–activity curve for 131I in the lungs was derived from the whole-body planar imaging and compared with that obtained from the quantitative SPECT methods. Reconstructed and coregistered SPECT/CT images were converted into 3D density and activity probability maps suitable for MCNP4b input. Absorbed dose maps were calculated using electron and photon transport in MCNP4b. Administered activity was estimated on the basis of the maximum tolerated dose (MTD) of 27.25 Gy to the normal lungs. Computational efficiency of the MCNP4b code was studied with a simple segmentation approach. In addition, the Benua–Leeper method was used to estimate the recommended administered activity. The standard dosing plan was modified to account for the weight of this pediatric patient, where the 2.96-GBq (80 mCi) whole-body retention was scaled to 2.44 GBq (66 mCi) to give the same dose rate of 43.6 rad/h in the lungs at 48 h. Results Using the MCNP4b code, both the spatial dose distribution and a dose–volume histogram were obtained for the lungs. An administered activity of 1.72 GBq (46.4 mCi) delivered the putative MTD of 27.25 Gy to the lungs with a tumor absorbed dose of 63.7 Gy. Directly applying the Benua–Leeper method, an administered activity of 3.89 GBq (105.0 mCi) was obtained, resulting in tumor and lung absorbed doses of 144.2 and 61.6 Gy, respectively, when the MCNP-based dosimetry was applied. The voxel-by-voxel calculation time of 4,642.3 h for photon transport was reduced to 16.8 h when the activity maps were segmented into 20 regions. Conclusion MCNP4b–based, patient-specific 3D dosimetry is feasible and important in the dosimetry of thyroid cancer patients with avid lung metastases that exhibit prolonged retention in the lungs. PMID:17138741

PET/CT-Based Dosimetry in 90Y-Microsphere Selective Internal Radiation Therapy: Single Cohort Comparison With Pretreatment Planning on (99m)Tc-MAA Imaging and Correlation With Treatment Efficacy.

PubMed

Song, Yoo Sung; Paeng, Jin Chul; Kim, Hyo-Cheol; Chung, Jin Wook; Cheon, Gi Jeong; Chung, June-Key; Lee, Dong Soo; Kang, Keon Wook

2015-06-01

⁹⁰Y PET/CT can be acquired after ⁹⁰Y-microsphere selective radiation internal therapy (SIRT) to describe radioactivity distribution. We performed dosimetry using ⁹⁰Y-microsphere PET/CT data to evaluate treatment efficacy and appropriateness of activity planning from (99m)Tc-MAA scan and SPECT/CT. Twenty-three patients with liver malignancy were included in the study. (99m)Tc-MAA was injected during planning angiography and whole body (99m)Tc-MAA scan and liver SPECT/CT were acquired. After SIRT using ⁹⁰Y-resin microsphere, ⁹⁰Y-microsphere PET/CT was acquired. A partition model (PM) using 4 compartments (tumor, intarget normal liver, out-target normal liver, and lung) was adopted, and absorbed dose to each compartment was calculated based on measurements from (99m)Tc-MAA SPECT/CT and ⁹⁰Y-microsphere PET/CT, respectively, to be compared with each other. Progression-free survival (PFS) was evaluated in terms of tumor absorbed doses calculated by (99m)Tc-MAA SPECT/CT and ⁹⁰Y-microsphere PET/CT results. Lung shunt fraction was overestimated on (99m)Tc-MAA scan compared with ⁹⁰Y-microsphere PET/CT (0.060 ± 0.037 vs. 0.018 ± 0.026, P < 0.01). Tumor absorbed dose exhibited a close correlation between the results from (99m)Tc-MAA SPECT/CT and ⁹⁰Y-microsphere PET/CT (r = 0.64, P < 0.01), although the result from (99m)Tc-MAA SPECT/CT was significantly lower than that from ⁹⁰Y-microsphere PET/CT (135.4 ± 64.2 Gy vs. 185.0 ± 87.8 Gy, P < 0.01). Absorbed dose to in-target normal liver was overestimated on (99m)Tc-MAA SPECT/CT compared with PET/CT (62.6 ± 38.2 Gy vs. 45.2 ± 32.0 Gy, P = 0.02). Absorbed dose to out-target normal liver did not differ between (99m)Tc-MAA SPECT/CT and ⁹⁰Y-microsphere PET/CT (P = 0.49). Patients with tumor absorbed dose >200 Gy on ⁹⁰Y-microsphere PET/CT had longer PFS than those with tumor absorbed dose ≤200 Gy (286 ± 56 days vs. 92 ± 20 days, P = 0.046). Tumor absorbed dose calculated by (99m)Tc-MAA SPECT/CT was not a significant predictor for PFS. Activity planning based on (99m)Tc-MAA scan and SPECT/CT can be effectively used as a conservative method. Post-SIRT dosimetry based on ⁹⁰Y-microsphere PET/CT is an effective method to predict treatment efficacy.

PET/CT-Based Dosimetry in 90Y-Microsphere Selective Internal Radiation Therapy: Single Cohort Comparison With Pretreatment Planning on 99mTc-MAA Imaging and Correlation With Treatment Efficacy

PubMed Central

Song, Yoo Sung; Paeng, Jin Chul; Kim, Hyo-Cheol; Chung, Jin Wook; Cheon, Gi Jeong; Chung, June-Key; Lee, Dong Soo; Kang, Keon Wook

2015-01-01

Abstract 90Y PET/CT can be acquired after 90Y-microsphere selective radiation internal therapy (SIRT) to describe radioactivity distribution. We performed dosimetry using 90Y-microsphere PET/CT data to evaluate treatment efficacy and appropriateness of activity planning from 99mTc-MAA scan and SPECT/CT. Twenty-three patients with liver malignancy were included in the study. 99mTc-MAA was injected during planning angiography and whole body 99mTc-MAA scan and liver SPECT/CT were acquired. After SIRT using 90Y-resin microsphere, 90Y-microsphere PET/CT was acquired. A partition model (PM) using 4 compartments (tumor, intarget normal liver, out-target normal liver, and lung) was adopted, and absorbed dose to each compartment was calculated based on measurements from 99mTc-MAA SPECT/CT and 90Y-microsphere PET/CT, respectively, to be compared with each other. Progression-free survival (PFS) was evaluated in terms of tumor absorbed doses calculated by 99mTc-MAA SPECT/CT and 90Y-microsphere PET/CT results. Lung shunt fraction was overestimated on 99mTc-MAA scan compared with 90Y-microsphere PET/CT (0.060 ± 0.037 vs. 0.018 ± 0.026, P < 0.01). Tumor absorbed dose exhibited a close correlation between the results from 99mTc-MAA SPECT/CT and 90Y-microsphere PET/CT (r = 0.64, P < 0.01), although the result from 99mTc-MAA SPECT/CT was significantly lower than that from 90Y-microsphere PET/CT (135.4 ± 64.2 Gy vs. 185.0 ± 87.8 Gy, P < 0.01). Absorbed dose to in-target normal liver was overestimated on 99mTc-MAA SPECT/CT compared with PET/CT (62.6 ± 38.2 Gy vs. 45.2 ± 32.0 Gy, P = 0.02). Absorbed dose to out-target normal liver did not differ between 99mTc-MAA SPECT/CT and 90Y-microsphere PET/CT (P = 0.49). Patients with tumor absorbed dose >200 Gy on 90Y-microsphere PET/CT had longer PFS than those with tumor absorbed dose ≤200 Gy (286 ± 56 days vs. 92 ± 20 days, P = 0.046). Tumor absorbed dose calculated by 99mTc-MAA SPECT/CT was not a significant predictor for PFS. Activity planning based on 99mTc-MAA scan and SPECT/CT can be effectively used as a conservative method. Post-SIRT dosimetry based on 90Y-microsphere PET/CT is an effective method to predict treatment efficacy. PMID:26061323

High-energy neutron depth-dose distribution experiment.

PubMed

Ferenci, M S; Hertel, N E

2003-01-01

A unique set of high-energy neutron depth-dose benchmark experiments were performed at the Los Alamos Neutron Science Center/Weapons Neutron Research (LANSCE/WNR) complex. The experiments consisted of filtered neutron beams with energies up to 800 MeV impinging on a 30 x 30 x 30 cm3 liquid, tissue-equivalent phantom. The absorbed dose was measured in the phantom at various depths with tissue-equivalent ion chambers. This experiment is intended to serve as a benchmark experiment for the testing of high-energy radiation transport codes for the international radiation protection community.

Models of Hematopoietic Dynamics Following Burn for Use in Combined Injury Simulations

DTIC Science & Technology

2015-04-28

distribution is unlimited. 13. SUPPLEMENTARY NOTES 14. ABSTRACT The effects of thermal injury were incorporated into previously developed models that...per kilogram (C kg–1) absorbed dose (rad) 1 × 10–2 joule per kilogram (J kg–1§) equivalent and effective dose (rem) 1 × 10–2 joule per kilogram (J...Gy = 1 J kg–1). **The special name for the SI unit of equivalent and effective dose is the sievert (Sv). (1 Sv = 1 J kg–1). Table of Contents Table

Intercomparison of standards of absorbed dose between the USSR and the UK

NASA Astrophysics Data System (ADS)

Berlyand, V. A.; Bregadze, J. I.; Burns, J. E.; Dusautoy, A. R.; Sharpe, P. H. G.

1991-05-01

A comparison of national standards of absorbed dose was carried out between the All-Union Research Institute for Physical Technical and Radiotechnical Measurements (VNIIFTRI), USSR, and the National Physical Laboratotry (NPL), UK (United Kingdom). Absorbed dose to water for cobalt 60 gamma radiation was compared by means of Fricke dosimeters and ionization chambers in 1985 and 1986. The primary standards used to derive absorbed dose to water were cavity ionization chambers at NPL and a graphite calorimeter at VNIIFTRI. The ratio of absorbed dose to water, NPL to VNIIFTRI, using Fricke dosimeters was 1.008; using ionization chambers it was 1.007. This agreement is within the estimated uncertainties of the standards and measurement methods.

Converging stereotactic radiotherapy using kilovoltage X-rays: experimental irradiation of normal rabbit lung and dose-volume analysis with Monte Carlo simulation.

PubMed

Kawase, Takatsugu; Kunieda, Etsuo; Deloar, Hossain M; Tsunoo, Takanori; Seki, Satoshi; Oku, Yohei; Saitoh, Hidetoshi; Saito, Kimiaki; Ogawa, Eileen N; Ishizaka, Akitoshi; Kameyama, Kaori; Kubo, Atsushi

2009-10-01

To validate the feasibility of developing a radiotherapy unit with kilovoltage X-rays through actual irradiation of live rabbit lungs, and to explore the practical issues anticipated in future clinical application to humans through Monte Carlo dose simulation. A converging stereotactic irradiation unit was developed, consisting of a modified diagnostic computed tomography (CT) scanner. A tiny cylindrical volume in 13 normal rabbit lungs was individually irradiated with single fractional absorbed doses of 15, 30, 45, and 60 Gy. Observational CT scanning of the whole lung was performed every 2 weeks for 30 weeks after irradiation. After 30 weeks, histopathologic specimens of the lungs were examined. Dose distribution was simulated using the Monte Carlo method, and dose-volume histograms were calculated according to the data. A trial estimation of the effect of respiratory movement on dose distribution was made. A localized hypodense change and subsequent reticular opacity around the planning target volume (PTV) were observed in CT images of rabbit lungs. Dose-volume histograms of the PTVs and organs at risk showed a focused dose distribution to the target and sufficient dose lowering in the organs at risk. Our estimate of the dose distribution, taking respiratory movement into account, revealed dose reduction in the PTV. A converging stereotactic irradiation unit using kilovoltage X-rays was able to generate a focused radiobiologic reaction in rabbit lungs. Dose-volume histogram analysis and estimated sagittal dose distribution, considering respiratory movement, clarified the characteristics of the irradiation received from this type of unit.

Prevention of Transfusion-Associated Graft-versus-Host Disease by Irradiation: Technical Aspect of a New Ferrous Sulphate Dosimetric System

PubMed Central

Del Lama, Lucas Sacchini; de Góes, Evamberto Garcia; Petchevist, Paulo César Dias; Moretto, Edson Lara; Borges, José Carlos; Covas, Dimas Tadeu; de Almeida, Adelaide

2013-01-01

Irradiation of whole blood and blood components before transfusion is currently the only accepted method to prevent Transfusion-Associated Graft-Versus-Host-Disease (TA-GVHD). However, choosing the appropriate technique to determine the dosimetric parameters associated with blood irradiation remains an issue. We propose a dosimetric system based on the standard Fricke Xylenol Gel (FXG) dosimeter and an appropriate phantom. The modified dosimeter was previously calibrated using a 60Co teletherapy unit and its validation was accomplished with a 137Cs blood irradiator. An ionization chamber, standard FXG, radiochromic film and thermoluminescent dosimeters (TLDs) were used as reference dosimeters to determine the dose response and dose rate of the 60Co unit. The dose distributions in a blood irradiator were determined with the modified FXG, the radiochromic film, and measurements by TLD dosimeters. A linear response for absorbed doses up to 54 Gy was obtained with our system. Additionally, the dose rate uncertainties carried out with gel dosimetry were lower than 5% and differences lower than 4% were noted when the absorbed dose responses were compared with ionization chamber, film and TLDs. PMID:23762345

On the suitability of ultrathin detectors for absorbed dose assessment in the presence of high-density heterogeneities.

PubMed

Bueno, M; Carrasco, P; Jornet, N; Muñoz-Montplet, C; Duch, M A

2014-08-01

The aim of this study was to evaluate the suitability of several detectors for the determination of absorbed dose in bone. Three types of ultrathin LiF-based thermoluminescent dosimeters (TLDs)-two LiF:Mg,Cu,P-based (MCP-Ns and TLD-2000F) and a (7)Li-enriched LiF:Mg,Ti-based (MTS-7s)-as well as EBT2 Gafchromic films were used to measure percentage depth-dose distributions (PDDs) in a water-equivalent phantom with a bone-equivalent heterogeneity for 6 and 18 MV and a set of field sizes ranging from 5 x 5 cm2 to 20 x 20 cm2. MCP-Ns, TLD-2000F, MTS-7s, and EBT2 have active layers of 50, 20, 50, and 30 μm, respectively. Monte Carlo (MC) dose calculations (PENELOPE code) were used as the reference and helped to understand the experimental results and to evaluate the potential perturbation of the fluence in bone caused by the presence of the detectors. The energy dependence and linearity of the TLDs' response was evaluated. TLDs exhibited flat energy responses (within 2.5%) and linearity with dose (within 1.1%) within the range of interest for the selected beams. The results revealed that all considered detectors perturb the electron fluence with respect to the energy inside the bone-equivalent material. MCP-Ns and MTS-7s underestimated the absorbed dose in bone by 4%-5%. EBT2 exhibited comparable accuracy to MTS-7s and MCP-Ns. TLD-2000F was able to determine the dose within 2% accuracy. No dependence on the beam energy or field size was observed. The MC calculations showed that a[Formula: see text] thick detector can provide reliable dose estimations in bone regardless of whether it is made of LiF, water or EBT's active layer material. TLD-2000F was found to be suitable for providing reliable absorbed dose measurements in the presence of bone for high-energy x-ray beams.

The NUKDOS software for treatment planning in molecular radiotherapy.

PubMed

Kletting, Peter; Schimmel, Sebastian; Hänscheid, Heribert; Luster, Markus; Fernández, Maria; Nosske, Dietmar; Lassmann, Michael; Glatting, Gerhard

2015-09-01

The aim of this work was the development of a software tool for treatment planning prior to molecular radiotherapy, which comprises all functionality to objectively determine the activity to administer and the pertaining absorbed doses (including the corresponding error) based on a series of gamma camera images and one SPECT/CT or probe data. NUKDOS was developed in MATLAB. The workflow is based on the MIRD formalism For determination of the tissue or organ pharmacokinetics, gamma camera images as well as probe, urine, serum and blood activity data can be processed. To estimate the time-integrated activity coefficients (TIAC), sums of exponentials are fitted to the time activity data and integrated analytically. To obtain the TIAC on the voxel level, the voxel activity distribution from the quantitative 3D SPECT/CT (or PET/CT) is used for scaling and weighting the TIAC derived from the 2D organ data. The voxel S-values are automatically calculated based on the voxel-size of the image and the therapeutic nuclide ((90)Y, (131)I or (177)Lu). The absorbed dose coefficients are computed by convolution of the voxel TIAC and the voxel S-values. The activity to administer and the pertaining absorbed doses are determined by entering the absorbed dose for the organ at risk. The overall error of the calculated absorbed doses is determined by Gaussian error propagation. NUKDOS was tested for the operation systems Windows(®) 7 (64 Bit) and 8 (64 Bit). The results of each working step were compared to commercially available (SAAMII, OLINDA/EXM) and in-house (UlmDOS) software. The application of the software is demonstrated using examples form peptide receptor radionuclide therapy (PRRT) and from radioiodine therapy of benign thyroid diseases. For the example from PRRT, the calculated activity to administer differed by 4% comparing NUKDOS and the final result using UlmDos, SAAMII and OLINDA/EXM sequentially. The absorbed dose for the spleen and tumour differed by 7% and 8%, respectively. The results from the example from radioiodine therapy of benign thyroid diseases and the example given in the latest corresponding SOP were identical. The implemented, objective methods facilitate accurate and reproducible results. The software is freely available. Copyright © 2015. Published by Elsevier GmbH.

Potential implications of the bystander effect on TCP and EUD when considering target volume dose heterogeneity.

PubMed

Balderson, Michael J; Kirkby, Charles

2015-01-01

In light of in vitro evidence suggesting that radiation-induced bystander effects may enhance non-local cell killing, there is potential for impact on radiotherapy treatment planning paradigms such as the goal of delivering a uniform dose throughout the clinical target volume (CTV). This work applies a bystander effect model to calculate equivalent uniform dose (EUD) and tumor control probability (TCP) for external beam prostate treatment and compares the results with a more common model where local response is dictated exclusively by local absorbed dose. The broad assumptions applied in the bystander effect model are intended to place an upper limit on the extent of the results in a clinical context. EUD and TCP of a prostate cancer target volume under conditions of increasing dose heterogeneity were calculated using two models: One incorporating bystander effects derived from previously published in vitro bystander data ( McMahon et al. 2012 , 2013a); and one using a common linear-quadratic (LQ) response that relies exclusively on local absorbed dose. Dose through the CTV was modelled as a normal distribution, where the degree of heterogeneity was then dictated by changing the standard deviation (SD). Also, a representative clinical dose distribution was examined as cold (low dose) sub-volumes were systematically introduced. The bystander model suggests a moderate degree of dose heterogeneity throughout a target volume will yield as good or better outcome compared to a uniform dose in terms of EUD and TCP. For a typical intermediate risk prostate prescription of 78 Gy over 39 fractions maxima in EUD and TCP as a function of increasing SD occurred at SD ∼ 5 Gy. The plots only dropped below the uniform dose values for SD ∼ 10 Gy, almost 13% of the prescribed dose. Small, but potentially significant differences in the outcome metrics between the models were identified in the clinically-derived dose distribution as cold sub-volumes were introduced. In terms of EUD and TCP, the bystander model demonstrates the potential to deviate from the common local LQ model predictions as dose heterogeneity through a prostate CTV varies. The results suggest, at least in a limiting sense, the potential for allowing some degree of dose heterogeneity within a CTV, although further investigation of the assumptions of the bystander model are warranted.

Absorbed dose determination using experimental and analytical predictions of x-ray spectra

NASA Astrophysics Data System (ADS)

Edwards, David Lee

1999-10-01

Electron beam welding in a vacuum is a technology that NASA is investigating as a joining technique for manufacture of space structures. The interaction of energetic electrons with metal produces x-rays. This investigation characterizes the x-ray environment due to operation of an in-vacuum electron beam welding tool and provides recommendations for adequate radiation shielding for astronauts performing the in-vacuum electron beam welding. NASA, in a joint venture with the Russian Space Agency, was scheduled to perform a series of welding in space experiments on board the United States Space Shuttle. This series of experiments was named the International Space Welding Experiment (ISWE). The hardware associated with the ISWE was leased to NASA, by the Paton Welding Institute (PWI) in Ukraine, for ground based welding experiments in preparation for flight. Two ground tests were scheduled, using the ISWE electron beam welding tool, to characterize the radiation exposure to an astronaut during the operation of the ISWE. These radiation exposure tests used Thermoluminescence Dosimeters (TLD's) shielded with material currently used by astronauts during Extra Vehicular Activities (EVA) to measure the radiation dose. The TLD's were exposed to x- ray radiation generated by operation of the ISWE in- vacuum electron beam welding tool. This investigation was the first known application of TLD's to measure absorbed dose from x-rays of energy less than 10 keV. The ISWE hardware was returned to Ukraine before the issue of adequate shielding for the astronauts was completely verified. Therefore alternate experimental and analytical methods were developed to measure and predict the x-ray spectral and intensity distribution generated by ISWE electron beam impact with metal. These x-ray spectra were normalized to an equivalent ISWE exposure then used to calculate the absorbed radiation dose to astronauts. These absorbed dose values were compared to TLD measurements obtained during actual operation of the ISWE in-vacuum electron beam welding tool. The calculated absorbed dose values were found to be in good agreement with the measured TLD values.

Neutron emission and dose distribution from natural carbon irradiated with a 12 MeV amu-1 12C5+ ion beam.

PubMed

Nandy, Maitreyee; Sarkar, P K; Sanami, T; Takada, M; Shibata, T

2016-09-01

Measured neutron energy distribution emitted from a thick stopping target of natural carbon at 0°, 30°, 60° and 90° from nuclear reactions caused by 12 MeV amu -1 incident 12 C 5+ ions were converted to energy differential and total neutron absorbed dose as well as ambient dose equivalent H * (10) using the fluence-to-dose conversion coefficients provided by the ICRP. Theoretical estimates were obtained using the Monte Carlo nuclear reaction model code PACE and a few existing empirical formulations for comparison. Results from the PACE code showed an underestimation of the high-energy part of energy differential dose distributions at forward angles whereas the empirical formulation by Clapier and Zaidins (1983 Nucl. Instrum. Methods 217 489-94) approximated the energy integrated angular distribution of H * (10) satisfactorily. Using the measured data, the neutron doses received by some vital human organs were estimated for anterior-posterior exposure. The estimated energy-averaged quality factors were found to vary for different organs from about 7 to about 13. Emitted neutrons having energies above 20 MeV were found to contribute about 20% of the total dose at 0° while at 90° the contribution was reduced to about 2%.

Determination of neutron flux distribution in an Am-Be irradiator using the MCNP.

PubMed

Shtejer-Diaz, K; Zamboni, C B; Zahn, G S; Zevallos-Chávez, J Y

2003-10-01

A neutron irradiator has been assembled at IPEN facilities to perform qualitative-quantitative analysis of many materials using thermal and fast neutrons outside the nuclear reactor premises. To establish the prototype specifications, the neutron flux distribution and the absorbed dose rates were calculated using the MCNP computer code. These theoretical predictions then allow one to discuss the optimum irradiator design and its performance.

Biokinetics and dosimetric studies about 99mTc(V)-DMSA distribution.

PubMed

Correia, M B L; Magnata, S S L P; Silva, I M S; Catanho, M T J A; Lima, F F

2010-05-10

Research for radiodiagnostic agents should considerate biological critical parameters which will give own contribution on the absorbed dose. The dimercaptosuccinic acid (DMSA) labeled with (99m)Tc(V) is a radiopharmaceutical which has well established role in medullar thyroid carcinoma and has been proposed in evaluation of bone metastasis. This work studied the biokinetics and dosimetry of (99m)Tc(V)-DMSA by animal model. The (99m)Tc(V)-DMSA was prepared from a (III)DMSA kit alkalized. Mice (n=5) received (99m)Tc(V)DMSA i.v., they were sacrificed (30 min, 1h, 5h and 12h), the organs excised and the activities measured by a gamma counter. The results were evaluated based on %activity/g and the absorbed dose was estimated (MIRDOSE 3.0 program) by extrapolation of data from animal to human scale. The results showed the majority of organs reached the top uptake at 30 min, the greatest kidney uptake was (4.81 +/- 1.38)% activity/g, while the bone presented its highest uptake at 1h (5.49+/- 0.47)% activity/g, after 1h all the organs had activity exponential decrease. The biokinetic profile of (99m)Tc(V)-DMSA was well established, allowing quantifying of residence time, and the radiation dose estimates were made for this agent. About the absorbed dose, the preliminary results showed higher value to bone, being the soft tissue dose relatively low.

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

A method for depth-dose distribution measurements in tissue irradiated by a proton beam

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

Gambarini, G.; Birattari, C.; Bartolo, D. de

1994-12-31

The use of protons and heavy ions for the treatment of malignant and non-malignant disease has aroused a growing interest in the last decade. The notable advantage of heavy charged particles over photons in external beam radiotherapy lies in the possibility of irradiating a small localized region within the body, keeping a low value for the entrance dose. Owing to this high disuniformity of energy deposition, an essential requirement for treatment planning is a precise evaluation of the spatial distribution of absorbed dose. The proposed method for depth-dose distribution measurements utilizes a chemical dosimeter (ferrous sulphate solution plus sulfuric acidmore » and eventually xylenol orange) incorporated in a gelatine, whose role is the maintenance of spatial information. Ionizing radiation causes a variation in some parameters of the system such as the proton relaxation rates in the solution (measurable by NMR analysis) or the optical absorption of the gel in the visible spectrum (measurable by spectrophotometry).« 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

Dose perturbation due to the presence of a prostatic urethral stent in patients receiving pelvic radiotherapy: an in vitro study.

PubMed

Gez, E; Cederbaum, M; Yachia, D; Bar-Deroma, R; Kuten, A

1997-01-01

Temporary metallic intraprostatic stent is a new alternative treatment for patients with urinary obstructive syndrome caused by prostate cancer. Definitive radiotherapy is a treatment of choice for localized prostate cancer. This study evaluates in vitro the effect of a urethral intraprostatic metallic stent on the dose absorbed by the surrounding tissue. The study was designed to mimic the conditions under which the prostatic stent is placed in the body during pelvic irradiation. A urethral stent composed of a 50% nickel-50% titanium alloy (Uracoil-InStent) was imbedded in material mimicking normal tissue (bolus) at a simulated body depth of 10 cm. The distribution of the absorbed dose of irradiation was determined by film dosimetry using Kodak X-Omat V film. Irradiation was done in a single field at the isocenter of a 6 MV linear accelerator with a field size of 7 x 7 cm. The degree of film blackening was in direct proportion to the absorbed dose. The measurements showed an increase in dose of up to 20% immediately before the stent and a decrease of up to 18% immediately after the stent. These changes occurred within a range of 1-3 mm from both sides of the stent. In practice, irradiation in prostate cancer is given by two pairs of opposed co-axial fields; a total of four fields (Box Technique). The dose perturbations are partly cancelled in a pair of opposed beams resulting in a net variation of +/- 4%; therefore, the presence of the intraprostatic stent should not influence radiotherapy planning for prostate cancer.

Measuring dose from radiotherapy treatments in the vicinity of a cardiac pacemaker.

PubMed

Peet, Samuel C; Wilks, Rachael; Kairn, Tanya; Crowe, Scott B

2016-12-01

This study investigated the dose absorbed by tissues surrounding artificial cardiac pacemakers during external beam radiotherapy procedures. The usefulness of out-of-field reference data, treatment planning systems, and skin dose measurements to estimate the dose in the vicinity of a pacemaker was also examined. Measurements were performed by installing a pacemaker onto an anthropomorphic phantom, and using radiochromic film and optically stimulated luminescence dosimeters to measure the dose in the vicinity of the device during the delivery of square fields and clinical treatment plans. It was found that the dose delivered in the vicinity of the cardiac device was unevenly distributed both laterally and anteroposteriorly. As the device was moved distally from the square field, the dose dropped exponentially, in line with out-of-field reference data in the literature. Treatment planning systems were found to substantially underestimate the dose for volumetric modulated arc therapy, helical tomotherapy, and 3D conformal treatments. The skin dose was observed to be either greater or lesser than the dose received at the depth of the device, depending on the treatment site, and so care should be if skin dose measurements are to be used to estimate the dose to a pacemaker. Square field reference data may be used as an upper estimate of absorbed dose per monitor unit in the vicinity of a cardiac device for complex treatments involving multiple gantry angles. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Pharmacokinetics of multiple doses of transdermal flunixin meglumine in adult Holstein dairy cows.

PubMed

Kleinhenz, M D; Gorden, P J; Smith, J S; Schleining, J A; Kleinhenz, K E; Wulf, L L; Sidhu, P K; Rea, D; Coetzee, J F

2018-06-01

A transdermal formulation of the nonsteroidal anti-inflammatory drug, flunixin meglumine, has been approved in the United States and Canada for single-dose administration. Transdermal flunixin meglumine was administered to 10 adult Holstein cows in their second or third lactation at the label dose of 3.33 mg/kg every 24 hr for three total treatments. Plasma flunixin concentrations were determined using high-pressure liquid chromatography with mass spectroscopy (HPLC-MS). Pharmacokinetic analysis was completed on each individual animal with noncompartmental methods using computer software. The time to maximum drug concentration (Tmax) was 2.81 hr, and the maximum drug concentration was 1.08 μg/ml. The mean terminal half-life (T½) was determined to be 5.20 hr. Clearance per fraction absorbed (Cl/F) was calculated to be 0.294 L/hr kg -1 , and volume of distribution of fraction (Vz/F) absorbed was 2.20 L/kg. The mean accumulation factor was 1.10 after three doses. This indicates changes in dosing may not be required when giving multiple doses of flunixin transdermal. Further work is required to investigate the clinical efficacy of transdermal flunixin after multiple daily doses. © 2018 John Wiley & Sons Ltd.

Dose mapping using MCNP code and experiment for SVST-Co-60/B irradiator in Vietnam.

PubMed

Tran, Van Hung; Tran, Khac An

2010-06-01

By using MCNP code and ethanol-chlorobenzene (ECB) dosimeters the simulations and measurements of absorbed dose distribution in a tote-box of the Cobalt-60 irradiator, SVST-Co60/B at VINAGAMMA have been done. Based on the results Dose Uniformity Ratios (DUR), positions and values of minimum and maximum dose extremes in a tote-box, and efficiency of the irradiator for the different dummy densities have been gained. There is a good agreement between simulation and experimental results in comparison and they have valuable meanings for operation of the irradiator. Copyright 2010 Elsevier Ltd. All rights reserved.

Neutron relative biological effectiveness for solid cancer incidence in the Japanese A-bomb survivors: an analysis considering the degree of independent effects from γ-ray and neutron absorbed doses with hierarchical partitioning.

PubMed

Walsh, Linda

2013-03-01

It has generally been assumed that the neutron and γ-ray absorbed doses in the data from the life span study (LSS) of the Japanese A-bomb survivors are too highly correlated for an independent separation of the all solid cancer risks due to neutrons and due to γ-rays. However, with the release of the most recent data for all solid cancer incidence and the increased statistical power over previous datasets, it is instructive to consider alternatives to the usual approaches. Simple excess relative risk (ERR) models for radiation-induced solid cancer incidence fitted to the LSS epidemiological data have been applied with neutron and γ-ray absorbed doses as separate explanatory covariables. A simple evaluation of the degree of independent effects from γ-ray and neutron absorbed doses on the all solid cancer risk with the hierarchical partitioning (HP) technique is presented here. The degree of multi-collinearity between the γ-ray and neutron absorbed doses has also been considered. The results show that, whereas the partial correlation between the neutron and γ-ray colon absorbed doses may be considered to be high at 0.74, this value is just below the level beyond which remedial action, such as adding the doses together, is usually recommended. The resulting variance inflation factor is 2.2. Applying HP indicates that just under half of the drop in deviance resulting from adding the γ-ray and neutron absorbed doses to the baseline risk model comes from the joint effects of the neutrons and γ-rays-leaving a substantial proportion of this deviance drop accounted for by individual effects of the neutrons and γ-rays. The average ERR/Gy γ-ray absorbed dose and the ERR/Gy neutron absorbed dose that have been obtained here directly for the first time, agree well with previous indirect estimates. The average relative biological effectiveness (RBE) of neutrons relative to γ-rays, calculated directly from fit parameters to the all solid cancer ERR model with both colon absorbed dose covariables, is 65 (95 %CI: 11; 170). Therefore, although the 95 % CI is quite wide, reference to the colon doses with a neutron weighting of 10 may not be optimal as the basis for the determination of all solid cancer risks. Further investigations into the neutron RBE are required, ideally based on the LSS data with organ-specific neutron and γ-ray absorbed doses for all organs rather than the RBE weighted absorbed doses currently provided. The HP method is also suggested for use in other epidemiological cohort analyses that involve correlated explanatory covariables.

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.

3D modeling of effects of increased oxygenation and activity concentration in tumors treated with radionuclides and antiangiogenic drugs

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

Lagerloef, Jakob H.; Kindblom, Jon; Bernhardt, Peter

Purpose: Formation of new blood vessels (angiogenesis) in response to hypoxia is a fundamental event in the process of tumor growth and metastatic dissemination. However, abnormalities in tumor neovasculature often induce increased interstitial pressure (IP) and further reduce oxygenation (pO{sub 2}) of tumor cells. In radiotherapy, well-oxygenated tumors favor treatment. Antiangiogenic drugs may lower IP in the tumor, improving perfusion, pO{sub 2} and drug uptake, by reducing the number of malfunctioning vessels in the tissue. This study aims to create a model for quantifying the effects of altered pO{sub 2}-distribution due to antiangiogenic treatment in combination with radionuclide therapy. Methods:more » Based on experimental data, describing the effects of antiangiogenic agents on oxygenation of GlioblastomaMultiforme (GBM), a single cell based 3D model, including 10{sup 10} tumor cells, was developed, showing how radionuclide therapy response improves as tumor oxygenation approaches normal tissue levels. The nuclides studied were {sup 90}Y, {sup 131}I, {sup 177}Lu, and {sup 211}At. The absorbed dose levels required for a tumor control probability (TCP) of 0.990 are compared for three different log-normal pO{sub 2}-distributions: {mu}{sub 1} = 2.483, {sigma}{sub 1} = 0.711; {mu}{sub 2} = 2.946, {sigma}{sub 2} = 0.689; {mu}{sub 3} = 3.689, and {sigma}{sub 3} = 0.330. The normal tissue absorbed doses will, in turn, depend on this. These distributions were chosen to represent the expected oxygen levels in an untreated hypoxic tumor, a hypoxic tumor treated with an anti-VEGF agent, and in normal, fully-oxygenated tissue, respectively. The former two are fitted to experimental data. The geometric oxygen distributions are simulated using two different patterns: one Monte Carlo based and one radially increasing, while keeping the log-normal volumetric distributions intact. Oxygen and activity are distributed, according to the same pattern. Results: As tumor pO{sub 2} approaches normal tissue levels, the therapeutic effect is improved so that the normal tissue absorbed doses can be decreased by more than 95%, while retaining TCP, in the most favorable scenario and by up to about 80% with oxygen levels previously achieved in vivo, when the least favourable oxygenation case is used as starting point. The major difference occurs in poorly oxygenated cells. This is also where the pO{sub 2}-dependence of the oxygen enhancement ratio is maximal. Conclusions: Improved tumor oxygenation together with increased radionuclide uptake show great potential for optimising treatment strategies, leaving room for successive treatments, or lowering absorbed dose to normal tissues, due to increased tumor response. Further studies of the concomitant use of antiangiogenic drugs and radionuclide therapy therefore appear merited.« less

SU-E-T-477: An Efficient Dose Correction Algorithm Accounting for Tissue Heterogeneities in LDR Brachytherapy

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

Mashouf, S; Lai, P; Karotki, A

2014-06-01

Purpose: Seed brachytherapy is currently used for adjuvant radiotherapy of early stage prostate and breast cancer patients. The current standard for calculation of dose surrounding the brachytherapy seeds is based on American Association of Physicist in Medicine Task Group No. 43 (TG-43 formalism) which generates the dose in homogeneous water medium. Recently, AAPM Task Group No. 186 emphasized the importance of accounting for tissue heterogeneities. This can be done using Monte Carlo (MC) methods, but it requires knowing the source structure and tissue atomic composition accurately. In this work we describe an efficient analytical dose inhomogeneity correction algorithm implemented usingmore » MIM Symphony treatment planning platform to calculate dose distributions in heterogeneous media. Methods: An Inhomogeneity Correction Factor (ICF) is introduced as the ratio of absorbed dose in tissue to that in water medium. ICF is a function of tissue properties and independent of source structure. The ICF is extracted using CT images and the absorbed dose in tissue can then be calculated by multiplying the dose as calculated by the TG-43 formalism times ICF. To evaluate the methodology, we compared our results with Monte Carlo simulations as well as experiments in phantoms with known density and atomic compositions. Results: The dose distributions obtained through applying ICF to TG-43 protocol agreed very well with those of Monte Carlo simulations as well as experiments in all phantoms. In all cases, the mean relative error was reduced by at least 50% when ICF correction factor was applied to the TG-43 protocol. Conclusion: We have developed a new analytical dose calculation method which enables personalized dose calculations in heterogeneous media. The advantages over stochastic methods are computational efficiency and the ease of integration into clinical setting as detailed source structure and tissue segmentation are not needed. University of Toronto, Natural Sciences and Engineering Research Council of Canada.« less

[Investigation of radiation dose for lower tube voltage CT using automatic exposure control].

PubMed

Takata, Mitsuo; Matsubara, Kousuke; Koshida, Kichirou; Tarohda, Tohru

2015-04-01

The purpose of our study was to investigate radiation dose for lower tube voltage CT using automatic exposure control (AEC). An acrylic body phantom was used, and volume CT dose indices (CTDIvol) for tube voltages of 80, 100, 120, and 135 kV were investigated with combination of AEC. Average absorbed dose in the abdomen for 100 and 120 kV were also measured using thermoluminescence dosimeters. In addition, we examined noise characteristics under the same absorbed doses. As a result, the exposure dose was not decreased even when the tube voltage was lowered, and the organ absorbed dose value became approximately 30% high. And the noise was increased under the radiographic condition to be an equal absorbed dose. Therefore, radiation dose increases when AEC is used for lower tube voltage CT under the same standard deviation (SD) setting with 120 kV, and the optimization of SD setting is crucial.

Changes in prescribed doses for the Seattle neutron therapy system

NASA Astrophysics Data System (ADS)

Popescu, A.

2008-06-01

From the beginning of the neutron therapy program at the University of Washington Medical Center, the neutron dose distribution in tissue has been calculated using an in-house treatment planning system called PRISM. In order to increase the accuracy of the absorbed dose calculations, two main improvements were made to the PRISM treatment planning system: (a) the algorithm was changed by the addition of an analytical expression of the central axis wedge factor dependence with field size and depth developed at UWMC. Older versions of the treatment-planning algorithm used a constant central axis wedge factor; (b) a complete newly commissioned set of measured data was introduced in the latest version of PRISM. The new version of the PRISM algorithm allowed for the use of the wedge profiles measured at different depths instead of one wedge profile measured at one depth. The comparison of the absorbed dose calculations using the old and the improved algorithm showed discrepancies mainly due to the missing central axis wedge factor dependence with field size and depth and due to the absence of the wedge profiles at depths different from 10 cm. This study concludes that the previously reported prescribed doses for neutron therapy should be changed.

On the definition of absorbed dose

NASA Astrophysics Data System (ADS)

Grusell, Erik

2015-02-01

Purpose: The quantity absorbed dose is used extensively in all areas concerning the interaction of ionizing radiation with biological organisms, as well as with matter in general. The most recent and authoritative definition of absorbed dose is given by the International Commission on Radiation Units and Measurements (ICRU) in ICRU Report 85. However, that definition is incomplete. The purpose of the present work is to give a rigorous definition of absorbed dose. Methods: Absorbed dose is defined in terms of the random variable specific energy imparted. A random variable is a mathematical function, and it cannot be defined without specifying its domain of definition which is a probability space. This is not done in report 85 by the ICRU, mentioned above. Results: In the present work a definition of a suitable probability space is given, so that a rigorous definition of absorbed dose is possible. This necessarily includes the specification of the experiment which the probability space describes. In this case this is an irradiation, which is specified by the initial particles released and by the material objects which can interact with the radiation. Some consequences are discussed. Specific energy imparted is defined for a volume, and the definition of absorbed dose as a point function involves the specific energy imparted for a small mass contained in a volume surrounding the point. A possible more precise definition of this volume is suggested and discussed. Conclusions: The importance of absorbed dose motivates a proper definition, and one is given in the present work. No rigorous definition has been presented before.

Orthovoltage radiation therapy treatment planning using Monte Carlo simulation: treatment of neuroendocrine carcinoma of the maxillary sinus

NASA Astrophysics Data System (ADS)

Gao, Wanbao; Raeside, David E.

1997-12-01

Dose distributions that result from treating a patient with orthovoltage beams are best determined with a treatment planning system that uses the Monte Carlo method, and such systems are not readily available. In the present work, the Monte Carlo method was used to develop a computer code for determining absorbed dose distributions in orthovoltage radiation therapy. The code was used in planning treatment of a patient with a neuroendocrine carcinoma of the maxillary sinus. Two lateral high-energy photon beams supplemented by an anterior orthovoltage photon beam were utilized in the treatment plan. For the clinical case and radiation beams considered, a reasonably uniform dose distribution is achieved within the target volume, while the dose to the lens of each eye is 4 - 8% of the prescribed dose. Therefore, an orthovoltage photon beam, when properly filtered and optimally combined with megavoltage beams, can be effective in the treatment of cancers below the skin, providing that accurate treatment planning is carried out to establish with accuracy and precision the doses to critical structures.

A rule of unity for human intestinal absorption 3: Application to pharmaceuticals.

PubMed

Patel, Raj B; Yalkowsky, Samuel H

2018-02-01

The rule of unity is based on a simple absorption parameter, Π, that can accurately predict whether or not an orally administered drug will be well absorbed or poorly absorbed. The intrinsic aqueous solubility and octanol-water partition coefficient, along with the drug dose are used to calculate Π. We show that a single delineator value for Π exist that can distinguish whether a drug is likely to be well absorbed (FA ≥ 0.5) or poorly absorbed (FA < 0.5) at any specified dose. The model is shown to give 82.5% correct predictions for over 938 pharmaceuticals. The maximum well-absorbed dose (i.e. the maximum dose that will be more than 50% absorbed) calculated using this model can be utilized as a guideline for drug design and synthesis. Copyright © 2017 John Wiley & Sons, Ltd.

Dose Distribution in Cone-Beam Breast Computed Tomography: An Experimental Phantom Study

NASA Astrophysics Data System (ADS)

Russo, Paolo; Lauria, Adele; Mettivier, Giovanni; Montesi, Maria Cristina; Villani, Natalia

2010-02-01

We measured the spatial distribution of absorbed dose in a 14 cm diameter PMMA half-ellipsoid phantom simulating the uncompressed breast, using an X-ray cone-beam breast computed tomography apparatus, assembled for laboratory tests. Thermoluminescent dosimeters (TLD-100) were placed inside the phantom in six positions, both axially and at the phantom periphery. To study the dose distribution inside the PMMA phantom two experimental setups were adopted with effective energies in the range 28.7-44.4 keV. Different values of effective energies were obtained by combining different configurations of added Cu filtration (0.05 mm or 0.2 mm) and tube voltages (from 50 kVp to 80 kVp). Dose values obtained by TLDs in different positions inside the PMMA are reported. To evaluate the dose distribution in the breast shaped volume, the values measured were normalized to the one obtained in the inner position inside the phantom. Measurements with a low energy setup show a gradual increment of dose going from the "chest wall" to the "nipple" (63% more at the "nipple" compared to the central position). Likewise, a gradual increment is observed going from the breast axis toward the periphery (82% more at the "skin" compared to the central position). A more uniform distribution of dose inside the PMMA was obtained with a high energy setup (the maximum variation was 33% at 35.5 keV effective energy in the radial direction). The most uniform distribution is obtained at 44.4 keV. The results of this study show how the dose is distributed: it varies as a function of effective energy of the incident X-ray beam and as a function of the position inside the volume (axial or peripheral position).

[Radiation effect on cosmonauts during extravehicular activities in 2008-2009].

PubMed

Mitrikas, V G

2010-01-01

The geometrical model of suited cosmonaut's phantom was used in mathematical modeling of EVAs performed by cosmonauts with consideration of changes in the ISS Russian segment configuration during 2008-2009 and the dependence of space radiation absorbed dose on EVA scene. Influence of spatial position of cosmonaut on absorbed dose value was evaluated with the EVA dosimeter model reproducing the actually determined weight and dimension. Calculated absorbed dose values are in good agreement with experimental data. Absorbed doses imparted to body organs (skin, lens, hemopoietic system, gastrointestinal tract, central nervous system, gonads) were determined for specific EVA events.

A methodological approach to a realistic evaluation of skin absorbed doses during manipulation of radioactive sources by means of GAMOS Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Italiano, Antonio; Amato, Ernesto; Auditore, Lucrezia; Baldari, Sergio

2018-05-01

The accurate evaluation of the radiation burden associated with radiation absorbed doses to the skin of the extremities during the manipulation of radioactive sources is a critical issue in operational radiological protection, deserving the most accurate calculation approaches available. Monte Carlo simulation of the radiation transport and interaction is the gold standard for the calculation of dose distributions in complex geometries and in presence of extended spectra of multi-radiation sources. We propose the use of Monte Carlo simulations in GAMOS, in order to accurately estimate the dose to the extremities during manipulation of radioactive sources. We report the results of these simulations for 90Y, 131I, 18F and 111In nuclides in water solutions enclosed in glass or plastic receptacles, such as vials or syringes. Skin equivalent doses at 70 μm of depth and dose-depth profiles are reported for different configurations, highlighting the importance of adopting a realistic geometrical configuration in order to get accurate dosimetric estimations. Due to the easiness of implementation of GAMOS simulations, case-specific geometries and nuclides can be adopted and results can be obtained in less than about ten minutes of computation time with a common workstation.

SU-E-I-28: Evaluating the Organ Dose From Computed Tomography Using Monte Carlo Calculations

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

Ono, T; Araki, F

Purpose: To evaluate organ doses from computed tomography (CT) using Monte Carlo (MC) calculations. Methods: A Philips Brilliance CT scanner (64 slice) was simulated using the GMctdospp (IMPS, Germany) based on the EGSnrc user code. The X-ray spectra and a bowtie filter for MC simulations were determined to coincide with measurements of half-value layer (HVL) and off-center ratio (OCR) profile in air. The MC dose was calibrated from absorbed dose measurements using a Farmer chamber and a cylindrical water phantom. The dose distribution from CT was calculated using patient CT images and organ doses were evaluated from dose volume histograms.more » Results: The HVLs of Al at 80, 100, and 120 kV were 6.3, 7.7, and 8.7 mm, respectively. The calculated HVLs agreed with measurements within 0.3%. The calculated and measured OCR profiles agreed within 3%. For adult head scans (CTDIvol) =51.4 mGy), mean doses for brain stem, eye, and eye lens were 23.2, 34.2, and 37.6 mGy, respectively. For pediatric head scans (CTDIvol =35.6 mGy), mean doses for brain stem, eye, and eye lens were 19.3, 24.5, and 26.8 mGy, respectively. For adult chest scans (CTDIvol=19.0 mGy), mean doses for lung, heart, and spinal cord were 21.1, 22.0, and 15.5 mGy, respectively. For adult abdominal scans (CTDIvol=14.4 mGy), the mean doses for kidney, liver, pancreas, spleen, and spinal cord were 17.4, 16.5, 16.8, 16.8, and 13.1 mGy, respectively. For pediatric abdominal scans (CTDIvol=6.76 mGy), mean doses for kidney, liver, pancreas, spleen, and spinal cord were 8.24, 8.90, 8.17, 8.31, and 6.73 mGy, respectively. In head scan, organ doses were considerably different from CTDIvol values. Conclusion: MC dose distributions calculated by using patient CT images are useful to evaluate organ doses absorbed to individual patients.« less

[Absorbed doses to critical organs from full mouth dental radiography].

PubMed

Zhang, G; Yasuhiko, O; Hidegiko, Y

1999-01-01

A few studies were reported in China on radiological risk of dental radiography. The aim of this study is to evaluate the absorbed doses of patients from the full mouth radiographs, and to find out the contribution from each projection to the total absorbed dose of the organs. Absorbed doses to critical organs were measured from 14-film complete dental radiography. The organs included pituitary, optical lens, parotid glands, submandibular glands, sublingual glands, thyroid, breasts, ovary, testes and the skin in center field of each projection were studied. A-radiation analog dosimetry system (RANDO) phantom with thermoluminescent dosimeters (ILD200) was used for the study. All of the exposure parameters were fixed. The total filtration was 2 mm Al equivalent. The column collaboration was 6 cm in diameter and 20 cm in length. The absorbed doses of organs were measured three times in each projection of the full-mouth series (FMS) exposures. The absorbed dose of lenses in FMS (249 microGy) in present study was much less (10%) than the doses (2,630 microGy) reported in 1976. The doses absorbed of other organs in the present study were thyroid gland (125 microGy), pituitary gland (112 microGy), parotid gland (153 microGy), submandibular gland (629 microGy), sublingual gland (1,900 microGy), and breast gland (12 microGy). The doses of the ovary and testis were to small to further analysis. All of the results show that the radiation risk to patients in intraoral radiograph has been reduced significantly. In the pituitary, half of the dose is from both sides of the maxillary molar projection. For the lenses, the largest contribultions of radiation (60%) come from the ipsilateral molar and premolar projection of maxilla. In parotid gland, up to 57% of the dose is from the contralateral molar, pre-molar and canine of maxilla. It could be derived that about 90% of the absorbed doses could be avoided in FMS if the column collimator is 20 cm long and the filter is 2.0 mm thick. If we use the 10-film complete mouth radiograph instead of the 14-film series, more 20% of the doses would be reduced.

Maximum dose rate is a determinant of hypothyroidism after 131I therapy of Graves' disease but the total thyroid absorbed dose is not.

PubMed

Krohn, Thomas; Hänscheid, Heribert; Müller, Berthold; Behrendt, Florian F; Heinzel, Alexander; Mottaghy, Felix M; Verburg, Frederik A

2014-11-01

The determinants of successful (131)I therapy of Graves' disease (GD) are unclear. To relate dosimetry parameters to outcome of therapy to identify significant determinants eu- and/or hypothyroidism after (131)I therapy in patients with GD. A retrospective study in which 206 Patients with GD treated in University Hospital between November 1999 and January 2011. All received (131)I therapy aiming at a total absorbed dose to the thyroid of 250 Gy based on pre-therapeutic dosimetry. Post-therapy dosimetric thyroid measurements were performed twice daily until discharge. From these measurements, thyroid (131)I half-life, the total thyroid absorbed dose, and the maximum dose rate after (131)I administration were calculated. In all, 48.5% of patients were hypothyroid and 28.6% of patients were euthyroid after (131)I therapy. In univariate analysis, nonhyperthyroid and hyperthyroid patients only differed by sex. A lower thyroid mass, a higher activity per gram thyroid tissue, a shorter effective thyroidal (131)I half-life, and a higher maximum dose rate, but not the total thyroid absorbed dose, were significantly associated with hypothyroidism. In multivariate analysis, the maximum dose rate remained the only significant determinant of hypothyroidism (P < .001). Maximum dose rates of 2.2 Gy/h and higher were associated with a 100% hypothyroidism rate. Not the total thyroid absorbed dose, but the maximum dose rate is a determinant of successfully achieving hypothyroidism in Graves' disease. Dosimetric concepts aiming at a specific total thyroid absorbed dose will therefore require reconsideration if our data are confirmed prospectively.

Measurement and simulation of lineal energy distribution at the CERN high energy facility with a tissue equivalent proportional counter.

PubMed

Rollet, S; Autischer, M; Beck, P; Latocha, M

2007-01-01

The response of a tissue equivalent proportional counter (TEPC) in a mixed radiation field with a neutron energy distribution similar to the radiation field at commercial flight altitudes has been studied. The measurements have been done at the CERN-EU High-Energy Reference Field (CERF) facility where a well-characterised radiation field is available for intercomparison. The TEPC instrument used by the ARC Seibersdorf Research is filled with pure propane gas at low pressure and can be used to determine the lineal energy distribution of the energy deposition in a mass of gas equivalent to a 2 microm diameter volume of unit density tissue, of similar size to the nuclei of biological cells. The linearity of the detector response was checked both in term of dose and dose rate. The effect of dead-time has been corrected. The influence of the detector exposure location and orientation in the radiation field on the dose distribution was also studied as a function of the total dose. The microdosimetric distribution of the absorbed dose as a function of the lineal energy has been obtained and compared with the same distribution simulated with the FLUKA Monte Carlo transport code. The dose equivalent was calculated by folding this distribution with the quality factor as a function of linear energy transfer. The comparison between the measured and simulated distributions show that they are in good agreement. As a result of this study the detector is well characterised, thanks also to the numerical simulations the instrument response is well understood, and it's currently being used onboard the aircrafts to evaluate the dose to aircraft crew caused by cosmic radiation.

Toxicity and tissue distribution of 2,2',4,4'- and 3,3',4, 4'-tetrachlorobiphenyls in houseflies.

PubMed

Saghir, S A; Hansen, L G

1999-02-01

Insects selectively retain different polychlorinated biphenyls (PCBs) which are then contributed to the food chain. To quantitate specific differences, adult female houseflies (Musca domestica L.) were topically dosed with 0.5 microgram of two structurally distinct PCB congeners (14C-2,2',4,4'-tetraCB or 14C-3,3',4,4'-tetraCB). Total radioactivity in the acetone rinse of intact flies, several tissues, and excrement was determined at 11 time points over a 48-h period. Ninety-seven percent of the applied 2,2',4,4'-tetraCB disappeared from the surface following an initial rapid absorption of 79% within 3 h. The absorbed 2,2',4,4'-tetraCB was immediately found within the thoracic cuticle, then spreading laterally to the abdominal cuticle and head, through the wax layers, or penetrating to the alimentary canal and ovaries. Penetration of 3,3',4, 4'-tetraCB was markedly slower; even though 87% of the applied dose was absorbed within 48 h, only 19% of the dose penetrated into the fly body within the first 3 h. This PCB very slowly distributed into the tissues. Toxicities of the sublethal doses were determined by monitoring changes in activity of houseflies following dosing with 0. 5 microg of radioactive PCBs. Flies treated with 2,2',5-triCB and 3, 3',4,4'-tetraCB remained very active, whereas 2,2',4, 4'-tetraCB-treated flies were less active, consistent with the previously reported toxicity of this congener. Copyright 1999 Academic Press.

The application of retrospective luminescence dosimetry in areas affected by fallout from the semipalatinsk nuclear test site: an evaluation of potential.

PubMed

Bailiff, I K; Stepanenko, V F; Göksu, H Y; Jungner, H; Balmukhanov, S B; Balmukhanov, T S; Khamidova, L G; Kisilev, V I; Kolyado, I B; Kolizshenkov, T V; Shoikhet, Y N; Tsyb, A F

2004-12-01

Luminescence retrospective dosimetry techniques have been applied with ceramic bricks to determine the cumulative external gamma dose due to fallout, primarily from the 1949 test, in populated regions lying NE of the Semipalatinsk Nuclear Test Site in Altai, Russia, and the Semipalatinsk region, Kazakhstan. As part of a pilot study, nine settlements were examined, three within the regions of highest predicted dose (Dolon in Kazakshstan; Laptev Log and Leshoz Topolinskiy in Russia) and the remainder of lower predicted dose (Akkol, Bolshaya Vladimrovka, Kanonerka, and Izvestka in Kazakshstan; Rubtsovsk and Kuria in Russia) within the lateral regions of the fallout trace due to the 1949 test. The settlement of Kainar, mainly affected by the 24 September 1951 nuclear test, was also examined. The bricks from this region were found to be generally suitable for use with the luminescence method. Estimates of cumulative absorbed dose in air due to fallout for Dolon and Kanonerka in Kazakshstan and Leshoz Topolinskiy were 475 +/- 110 mGy, 240 +/- 60 mGy, and 230 +/- 70 mGy, respectively. The result obtained in Dolon village is in agreement with published calculated estimates of dose normalized to Cs concentration in soil. At all the other locations (except Kainar) the experimental values of cumulative absorbed dose obtained indicated no significant dose due to fallout that could be detected within a margin of about 25 mGy. The results demonstrate the potential suitability of the luminescence method to map variations in cumulative dose within the relatively narrow corridor of fallout distribution from the 1949 test. Such work is needed to provide the basis for accurate dose reconstruction in settlements since the predominance of short-lived radionuclides in the fallout and a high degree of heterogeneity in the distribution of fallout are problematic for the application of conventional dosimetry techniques.

SU-F-T-06: Development of a Formalism for Practical Dose Measurements in Brachytherapy in the German Standard DIN 6803

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

Hensley, F; Chofor, N; Schoenfeld, A

2016-06-15

Purpose: In the steep dose gradients in the vicinity of a radiation source and due to the properties of the changing photon spectra, dose measurements in Brachytherapy usually have large uncertainties. Working group DIN 6803-3 is presently discussing recommendations for practical brachytherapy dosimetry incorporating recent theoretical developments in the description of brachytherapy radiation fields as well as new detectors and phantom materials. The goal is to prepare methods and instruments to verify dose calculation algorithms and for clinical dose verification with reduced uncertainties. Methods: After analysis of the distance dependent spectral changes of the radiation field surrounding brachytherapy sources, themore » energy dependent response of typical brachytherapy detectors was examined with Monte Carlo simulations. A dosimetric formalism was developed allowing the correction of their energy dependence as function of source distance for a Co-60 calibrated detector. Water equivalent phantom materials were examined with Monte Carlo calculations for their influence on brachytherapy photon spectra and for their water equivalence in terms of generating equivalent distributions of photon spectra and absorbed dose to water. Results: The energy dependence of a detector in the vicinity of a brachytherapy source can be described by defining an energy correction factor kQ for brachytherapy in the same manner as in existing dosimetry protocols which incorporates volume averaging and radiation field distortion by the detector. Solid phantom materials were identified which allow precise positioning of a detector together with small correctable deviations from absorbed dose to water. Recommendations for the selection of detectors and phantom materials are being developed for different measurements in brachytherapy. Conclusion: The introduction of kQ for brachytherapy sources may allow more systematic and comparable dose measurements. In principle, the corrections can be verified or even determined by measurement in a water phantom and comparison with dose distributions calculated using the TG43 dosimetry formalism. Project is supported by DIN Deutsches Institut fuer Normung.« less

Prediction of Normal Organ Absorbed Doses for [177Lu]Lu-PSMA-617 Using [44Sc]Sc-PSMA-617 Pharmacokinetics in Patients With Metastatic Castration Resistant Prostate Carcinoma.

PubMed

Khawar, Ambreen; Eppard, Elisabeth; Sinnes, Jean Phlippe; Roesch, Frank; Ahmadzadehfar, Hojjat; Kürpig, Stefan; Meisenheimer, Michael; Gaertner, Florian C; Essler, Markus; Bundschuh, Ralph A

2018-04-23

In vivo pharmacokinetic analysis of [Sc]Sc-PSMA-617 was used to determine the normal organ-absorbed doses that may result from therapeutic activity of [Lu]Lu-PSMA-617 and to predict the maximum permissible activity of [Lu]Lu-PSMA-617 for patients with metastatic castration-resistant prostate carcinoma. Pharmacokinetics of [Sc]Sc-PSMA-617 was evaluated in 5 patients with metastatic castration-resistant prostate carcinoma using dynamic PET/CT, followed by 3 static PET/CT acquisitions and blood sample collection over 19.5 hours, as well as urine sample collection at 2 time points. Total activity measured in source organs by PET imaging, as well as counts per milliliter measured in blood and urine samples, was decay corrected back to the time of injection using the half-life of Sc. Afterward, forward decay correction using the half-life of Lu was performed, extrapolating the pharmacokinetics of [Sc]Sc-PSMA-617 to that of [Lu]Lu-PSMA-617. Source organs residence times and organ-absorbed doses for [Lu]Lu-PSMA-617 were calculated using OLINDA/EXM software. Bone marrow self-dose was determined with indirect blood-based method, and urinary bladder contents residence time was estimated by trapezoidal approximation. The maximum permissible activity of [Lu]Lu-PSMA-617 was calculated for each patient considering external beam radiotherapy toxicity limits for radiation absorbed doses to kidneys, bone marrow, salivary glands, and whole body. The predicted mean organ-absorbed doses were highest in the kidneys (0.44 mSv/MBq), followed by the salivary glands (0.23 mSv/MBq). The maximum permissible activity was highly variable among patients; limited by whole body-absorbed dose (1 patient), marrow-absorbed dose (1 patient), and kidney-absorbed dose (3 patients). [Sc]Sc-PSMA-617 PET/CT imaging is feasible and allows theoretical extrapolation of the pharmacokinetics of [Sc]Sc-PSMA-617 to that of [Lu]Lu-PSMA-617, with the intent of predicting normal organ-absorbed doses and maximum permissible activity in patients scheduled for therapy with [Lu]Lu-PSMA-617.

SU-F-19A-10: Recalculation and Reporting Clinical HDR 192-Ir Head and Neck Dose Distributions Using Model Based Dose Calculation

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

Carlsson Tedgren, A; Persson, M; Nilsson, J

Purpose: To retrospectively re-calculate dose distributions for selected head and neck cancer patients, earlier treated with HDR 192Ir brachytherapy, using Monte Carlo (MC) simulations and compare results to distributions from the planning system derived using TG43 formalism. To study differences between dose to medium (as obtained with the MC code) and dose to water in medium as obtained through (1) ratios of stopping powers and (2) ratios of mass energy absorption coefficients between water and medium. Methods: The MC code Algebra was used to calculate dose distributions according to earlier actual treatment plans using anonymized plan data and CT imagesmore » in DICOM format. Ratios of stopping power and mass energy absorption coefficients for water with various media obtained from 192-Ir spectra were used in toggling between dose to water and dose to media. Results: Differences between initial planned TG43 dose distributions and the doses to media calculated by MC are insignificant in the target volume. Differences are moderate (within 4–5 % at distances of 3–4 cm) but increase with distance and are most notable in bone and at the patient surface. Differences between dose to water and dose to medium are within 1-2% when using mass energy absorption coefficients to toggle between the two quantities but increase to above 10% for bone using stopping power ratios. Conclusion: MC predicts target doses for head and neck cancer patients in close agreement with TG43. MC yields improved dose estimations outside the target where a larger fraction of dose is from scattered photons. It is important with awareness and a clear reporting of absorbed dose values in using model based algorithms. Differences in bone media can exceed 10% depending on how dose to water in medium is defined.« less

Measurements of LET distribution and dose equivalent onboard the Space Shuttle IML-2 (STS-65) and S/MM#4 (STS-79).

PubMed

Hayashi, T; Doke, T; Kikuchi, J; Sakaguchi, T; Takeuchi, R; Takashima, T; Kobayashi, M; Terasawa, K; Takahashi, K; Watanabe, A; Kyan, A; Hasebe, N; Kashiwagi, T; Ogura, K; Nagaoka, S; Kato, M; Nakano, T; Takahashi, S; Yamanaka, H; Yamaguchi, K; Badhwar, G D

1997-12-01

Space radiation dosimetry measurements have been made onboard the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2: 28.5 degrees x 300 km: 14.68 days) and the STS-79 in the 4th Shuttle MIR mission (S/MM#4: 51.6 degrees x 300-400km: 10.2 days). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called "Real-time Radiation Monitoring Device (RRMD-I for IML-2 and RRMD-II with improved triggering system for S/MM#4)" utilizing silicon semi-conductor detectors and the other detectors are conventional passive detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. The main contribution to dose equivalent for particles with LET > 5.0 keV/micrometer (IML-2) and LET > 3.5 keV/micrometer (S/MM#4) is seen to be due to galactic cosmic rays (GCRs) and the contribution of the South Atlantic Anomaly (SAA) is less than 5% (IML-2: 28.5 degrees x 300 km) and 15% (S/MM#4: 51.6 degrees x 400 km) in the above RRMD LET detection conditions. For the whole LET range (> 0.2 kev/micrometer) obtained by TLDs and CR-39 in these two typical orbits (a small inclination x low altitude and a large inclination x high altitude), absorbed dose rates range from 94 to 114 microGy/day, dose equivalent rates from 186 to 207 microSv/day and average quality factors from 1.82 to 2.00 depending on the locations and directions of detectors inside the Spacelab at the highly protected IML-2 orbit (28.5 degrees x 300 km), and also, absorbed dose rates range from 290 to 367 microGy/day, dose equivalent rates from 582 to 651 microSv/day and average quality factors from 1.78 to 2.01 depending on the dosimeter packages around the RRMD-II "Detector Unit" at the S/MM#4 orbit (5l.6 degrees x 400km). In general, it is seen that absorbed doses depend on the orbit altitude (SAA trapped particles contribution dominant) and dose equivalents on the orbit inclination (GCR contribution dominant). The LET distributions obtained by two different types of active and passive detectors, RRMDs and CR-39, are in good agreement for LET of 15 - 200 kev/micrometer and difference of these distributions in the regions of LET < 15 kev/micrometer and LET > 200 kev/micrometer can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks and chemical etching conditions.

Measurements of LET distribution and dose equivalent onboard the Space Shuttle IML-2 (STS-65) and S/MM#4 (STS-79)

NASA Technical Reports Server (NTRS)

Hayashi, T.; Doke, T.; Kikuchi, J.; Sakaguchi, T.; Takeuchi, R.; Takashima, T.; Kobayashi, M.; Terasawa, K.; Takahashi, K.; Watanabe, A.;

Accuracy of a dose-area product compared to an absorbed dose to water at a point in a 2 cm diameter field

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

Dufreneix, S.; Ostrowsky, A.; Rapp, B.

Purpose: Graphite calorimeters with a core diameter larger than the beam can be used to establish dosimetric references in small fields. The dose-area product (DAP) measured can theoretically be linked to an absorbed dose at a point by the determination of a profile correction. This study aims at comparing the DAP-based protocol to the usual absorbed dose at a point protocol in a 2 cm diameter field for which both references exist. Methods: Two calorimeters were used, respectively, with a sensitive volume of 0.6 cm (for the absorbed dose at a point measurement) and 3 cm diameter (for the DAPmore » measurement). Profile correction was calculated from a 2D dose mapping using three detectors: a PinPoint chamber, a synthetic diamond, and EBT3 films. A specific protocol to read EBT3 films was implemented and the dose-rate and energy dependences were studied to assure a precise measurement, especially in the penumbra and out-of-field regions. Results: EBT3 films were found independent on dose rates over the range studied but showed a strong under-response (18%) at low energies. Depending on the dosimeter used for calculating the profile correction, a deviation of 0.8% (PinPoint chamber), 0.9% (diamond), or 1.9% (EBT3 films) was observed between the calibration coefficient derived from DAP measurements and the one directly established in terms of absorbed dose to water at a point. Conclusions: The DAP method can currently be linked to the classical dosimetric reference system based in an absorbed dose at a point only with a confidence interval of 95% (k = 2). None of the detectors studied can be used to determine an absorbed dose to water at a point from a DAP measurement with an uncertainty smaller than 1.2%.« less

A Biodosimeter for Multiparametric Determination of Radiation Dose, Radiation Quality, and Radiation Risk

NASA Technical Reports Server (NTRS)

Richmond, Robert; Cruz, Angela; Jansen, Heather; Bors, Karen

2003-01-01

Predicting risk of human cancer following exposure of an individual or a population to ionizing radiation is challenging. To an approximation, this is because uncertainties of uniform absorption of dose and the uniform processing of dose-related damage at the cellular level within a complex set of biological variables degrade the confidence of predicting the delayed expression of cancer as a relatively rare event. Cellular biodosimeters that simultaneously report: 1) the quantity of absorbed dose after exposure to ionizing radiation, 2) the quality of radiation delivering that dose, and 3) the risk of developing cancer by the cells absorbing that dose would therefore be useful. An approach to such a multiparametric biodosimeter will be reported. This is the demonstration of a dose responsive field effect of enhanced expression of keratin 18 (K18) in cultures of human mammary epithelial cells irradiated with cesium-1 37 gamma-rays. Dose response of enhanced K18 expression was experimentally extended over a range of 30 to 90 cGy for cells evaluated at mid-log phase. K18 has been reported to be a marker for tumor staging and for apoptosis, and thereby serves as an example of a potential marker for cancer risk, where the reality of such predictive value would require additional experimental development. Since observed radiogenic increase in expression of K18 is a field effect, ie., chronically present in all cells of the irradiated population, it may be hypothesized that K18 expression in specific cells absorbing particulate irradiation, such as the high-LET-producing atomic nuclei of space radiation, will report on both the single-cell distributions of those particles amongst cells within the exposed population, and that the relatively high dose per cell delivered by densely ionizing tracks of those intersecting particles will lead to cell-specific high-expression levels of K18, thereby providing analytical end points that may be used to resolve both the quantity and the quality of the radiation dose absorbed by individual cells. The principal value of this reported potential multiparametric cellular biodosimeter is suggested to be that it justifies a search for similar but more robust radiogenic assays. That is, K18 is only one radiation dose-sensitive expressed protein, whereas analytical techniques of genomics and proteomics can be used to simultaneously analyze multiple gene and protein expressions resulting from radiation-dose absorption. The potential usefulness of multiparametric cellular biodosimeters will be best realized from quantitatively profiling these multiple markers using these modern techniques.

Evaluation of the absorbed dose to the breast using radiochromic film in a dedicated CT mammotomography system employing a quasi-monochromatic x-ray beam.

PubMed

Crotty, Dominic J; Brady, Samuel L; Jackson, D'Vone C; Toncheva, Greta I; Anderson, Colin E; Yoshizumi, Terry T; Tornai, Martin P

2011-06-01

A dual modality SPECT-CT prototype system dedicated to uncompressed breast imaging (mammotomography) has been developed. The computed tomography subsystem incorporates an ultrathick K-edge filtration technique producing a quasi-monochromatic x-ray cone beam that optimizes the dose efficiency of the system for lesion imaging in an uncompressed breast. Here, the absorbed dose in various geometric phantoms and in an uncompressed and pendant cadaveric breast using a normal tomographic cone beam imaging protocol is characterized using both thermoluminescent dosimeter (TLD) measurements and ionization chamber-calibrated radiochromic film. Initially, two geometric phantoms and an anthropomorphic breast phantom are filled in turn with oil and water to simulate the dose to objects that mimic various breast shapes having effective density bounds of 100% fatty and glandular breast compositions, respectively. Ultimately, an excised human cadaver breast is tomographically scanned using the normal tomographic imaging protocol, and the dose to the breast tissue is evaluated and compared to the earlier phantom-based measurements. Measured trends in dose distribution across all breast geometric and anthropomorphic phantom volumes indicate lower doses in the medial breast and more proximal to the chest wall, with consequently higher doses near the lateral peripheries and nipple regions. Measured doses to the oil-filled phantoms are consistently lower across all volume shapes due to the reduced mass energy-absorption coefficient of oil relative to water. The mean measured dose to the breast cadaver, composed of adipose and glandular tissues, was measured to be 4.2 mGy compared to a mean whole-breast dose of 3.8 and 4.5 mGy for the oil- and water-filled anthropomorphic breast phantoms, respectively. Assuming rotational symmetry due to the tomographic acquisition exposures, these results characterize the 3D dose distributions in an uncompressed human breast tissue volume for this dedicated breast imaging device and illustrate advantages of using the novel ultrathick K-edge filtered beam to minimize the dose to the breast during fully-3D imaging.

Evaluation of the absorbed dose to the breast using radiochromic film in a dedicated CT mammotomography system employing a quasi-monochromatic x-ray beam

PubMed Central

Crotty, Dominic J.; Brady, Samuel L.; Jackson, D’Vone C.; Toncheva, Greta I.; Anderson, Colin E.; Yoshizumi, Terry T.; Tornai, Martin P.

2011-01-01

Purpose: A dual modality SPECT-CT prototype system dedicated to uncompressed breast imaging (mammotomography) has been developed. The computed tomography subsystem incorporates an ultrathick K-edge filtration technique producing a quasi-monochromatic x-ray cone beam that optimizes the dose efficiency of the system for lesion imaging in an uncompressed breast. Here, the absorbed dose in various geometric phantoms and in an uncompressed and pendant cadaveric breast using a normal tomographic cone beam imaging protocol is characterized using both thermoluminescent dosimeter (TLD) measurements and ionization chamber-calibrated radiochromic film. Methods: Initially, two geometric phantoms and an anthropomorphic breast phantom are filled in turn with oil and water to simulate the dose to objects that mimic various breast shapes having effective density bounds of 100% fatty and glandular breast compositions, respectively. Ultimately, an excised human cadaver breast is tomographically scanned using the normal tomographic imaging protocol, and the dose to the breast tissue is evaluated and compared to the earlier phantom-based measurements. Results: Measured trends in dose distribution across all breast geometric and anthropomorphic phantom volumes indicate lower doses in the medial breast and more proximal to the chest wall, with consequently higher doses near the lateral peripheries and nipple regions. Measured doses to the oil-filled phantoms are consistently lower across all volume shapes due to the reduced mass energy-absorption coefficient of oil relative to water. The mean measured dose to the breast cadaver, composed of adipose and glandular tissues, was measured to be 4.2 mGy compared to a mean whole-breast dose of 3.8 and 4.5 mGy for the oil- and water-filled anthropomorphic breast phantoms, respectively. Conclusions: Assuming rotational symmetry due to the tomographic acquisition exposures, these results characterize the 3D dose distributions in an uncompressed human breast tissue volume for this dedicated breast imaging device and illustrate advantages of using the novel ultrathick K-edge filtered beam to minimize the dose to the breast during fully-3D imaging. PMID:21815398

Radiotherapy in the management of keloids. Clinical experience with electron beam irradiation and comparison with X-ray therapy.

PubMed

Maarouf, Mohammad; Schleicher, Ursula; Schmachtenberg, Axel; Ammon, Jürgen

2002-06-01

Aim of this study was to evaluate the advantages of electron beam irradiation compared to kilovoltage X-ray therapy in the treatment of keloids. Furthermore, the risk of developing malignancy following keloid radiotherapy was assessed. An automatic water phantom was used to evaluate the dose distribution in tissue. Furthermore, a series of measurements was done on the patients using thermoluminescence dosimeters (TLD) to estimate the doses absorbed by the organs at risk. We also report our clinical experience with electron beam radiation of 134 keloids following surgical excision. Electron beam irradiation offers a high control rate (84%) with minimal side effects for keloids. Electron irradiation provides better dose distribution in tissue, and therefore less radiation burden to the organs at risk. After a mean follow-up period of 7.2 years, no severe side effects or malignancies were observed after keloid radiotherapy. Electron radiation therapy is superior to kilovoltage irradiation for treating keloids due to better dose distribution in tissue. In agreement with the literature, no cases of malignancy were observed after keloid irradiation.

A feasibility study on the use of phantoms with statistical lung masses for determining the uncertainty in the dose absorbed by the lung from broad beams of incident photons and neutrons

PubMed Central

Khankook, Atiyeh Ebrahimi; Hakimabad, Hashem Miri

2017-01-01

Abstract Computational models of the human body have gradually become crucial in the evaluation of doses absorbed by organs. However, individuals may differ considerably in terms of organ size and shape. In this study, the authors sought to determine the energy-dependent standard deviations due to lung size of the dose absorbed by the lung during external photon and neutron beam exposures. One hundred lungs with different masses were prepared and located in an adult male International Commission on Radiological Protection (ICRP) reference phantom. Calculations were performed using the Monte Carlo N-particle code version 5 (MCNP5). Variation in the lung mass caused great uncertainty: ~90% for low-energy broad parallel photon beams. However, for high-energy photons, the lung-absorbed dose dependency on the anatomical variation was reduced to <1%. In addition, the results obtained indicated that the discrepancy in the lung-absorbed dose varied from 0.6% to 8% for neutron beam exposure. Consequently, the relationship between absorbed dose and organ volume was found to be significant for low-energy photon sources, whereas for higher energy photon sources the organ-absorbed dose was independent of the organ volume. In the case of neutron beam exposure, the maximum discrepancy (of 8%) occurred in the energy range between 0.1 and 5 MeV. PMID:28077627

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

Lau, A; Ahmad, S; Chen, Y

Purpose: To quantify the simulated mean absorbed dose per technique (cGy/mAs) from a commercially available microCT scanner using various filtration techniques. Methods: Monte Carlo simulations using the Geant4 toolkit (version 10) was used utilizing the standard electromagnetic physics model. The Quantum FX microCT scanner (PerkinElmer, Waltham, MA) was modeled incorporating measured energy spectra and spatial dimensions of nominal source-to-object (SOD) distances. The energy distribution was measured using a spectrometer (X-123CdTe, Amptek Inc., Bedford, USA) for the 90 kVp X-ray beams with various filters (including no filter, 1 mm, 2 mm, 3 mm, 4 mm Al and 0.2 mm Cu +more » 2.5 mm Al). The SOD was set to 154 mm, 104 mm, and 52 mm. A total of 10 million incident particles were processed per simulation. Cutout value was set to 0.1 mm for both photon and electron. The mean dose absorbed (cGy/per incident particle) in a PMMA phantom (length of 2 cm and radius of 3 cm) were recorded. Exposure measurements were taken using a Radcal 9095 system with a protocol of 90 kVp, 200 µA, and ∼12 s beam-On time for the various filters. Results: The mean absorbed dose per mAs for various filtrations and different SOD setups indicated that the dose decreased as the SOD increased and as the amount of filtration increased. For a given SOD, the dose was reduced by as much as ∼13.7% by varying the filter (from 0.2 mm Cu + 2.5 mm Al to no filter). The maximum dose was found to be 0.39 cGy/mAs (SOD of 5.196 cm, no filter) while the minimum dose value was 0.077 cGy/mAs (SOD of 15.4 cm, .2mm Cu + 2mm Al filter). Conclusion: This study estimates easily the mean dose for objects scanned with a microCT scanner with different filtration.« less

An optimized computational method for determining the beta dose distribution using a multiple-element thermoluminescent dosimeter system.

PubMed

Shen, L; Levine, S H; Catchen, G L

1987-07-01

This paper describes an optimization method for determining the beta dose distribution in tissue, and it describes the associated testing and verification. The method uses electron transport theory and optimization techniques to analyze the responses of a three-element thermoluminescent dosimeter (TLD) system. Specifically, the method determines the effective beta energy distribution incident on the dosimeter system, and thus the system performs as a beta spectrometer. Electron transport theory provides the mathematical model for performing the optimization calculation. In this calculation, parameters are determined that produce calculated doses for each of the chip/absorber components in the three-element TLD system. The resulting optimized parameters describe an effective incident beta distribution. This method can be used to determine the beta dose specifically at 7 mg X cm-2 or at any depth of interest. The doses at 7 mg X cm-2 in tissue determined by this method are compared to those experimentally determined using an extrapolation chamber. For a great variety of pure beta sources having different incident beta energy distributions, good agreement is found. The results are also compared to those produced by a commonly used empirical algorithm. Although the optimization method produces somewhat better results, the advantage of the optimization method is that its performance is not sensitive to the specific method of calibration.

Performance evaluation of an improved optical computed tomography polymer gel dosimeter system for 3D dose verification of static and dynamic phantom deliveries

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

Lopatiuk-Tirpak, O.; Langen, K. M.; Meeks, S. L.

2008-09-15

The performance of a next-generation optical computed tomography scanner (OCTOPUS-5X) is characterized in the context of three-dimensional gel dosimetry. Large-volume (2.2 L), muscle-equivalent, radiation-sensitive polymer gel dosimeters (BANG-3) were used. Improvements in scanner design leading to shorter acquisition times are discussed. The spatial resolution, detectable absorbance range, and reproducibility are assessed. An efficient method for calibrating gel dosimeters using the depth-dose relationship is applied, with photon- and electron-based deliveries yielding equivalent results. A procedure involving a preirradiation scan was used to reduce the edge artifacts in reconstructed images, thereby increasing the useful cross-sectional area of the dosimeter by nearly amore » factor of 2. Dose distributions derived from optical density measurements using the calibration coefficient show good agreement with the treatment planning system simulations and radiographic film measurements. The feasibility of use for motion (four-dimensional) dosimetry is demonstrated on an example comparing dose distributions from static and dynamic delivery of a single-field photon plan. The capability to visualize three-dimensional dose distributions is also illustrated.« less

Radiation Dose Optimization For Critical Organs

NASA Astrophysics Data System (ADS)

Khodadadegan, Yasaman

Ionizing radiation used in the patient diagnosis or therapy has negative effects on the patient body in short term and long term depending on the amount of exposure. More than 700,000 examinations are everyday performed on Interventional Radiology modalities, however; there is no patient-centric information available to the patient or the Quality Assurance for the amount of organ dose received. In this study, we are exploring the methodologies to systematically reduce the absorbed radiation dose in the Fluoroscopically Guided Interventional Radiology procedures. In the first part of this study, we developed a mathematical model which determines a set of geometry settings for the equipment and a level for the energy during a patient exam. The goal is to minimize the amount of absorbed dose in the critical organs while maintaining image quality required for the diagnosis. The model is a large-scale mixed integer program. We performed polyhedral analysis and derived several sets of strong inequalities to improve the computational speed and quality of the solution. Results present the amount of absorbed dose in the critical organ can be reduced up to 99% for a specific set of angles. In the second part, we apply an approximate gradient method to simultaneously optimize angle and table location while minimizing dose in the critical organs with respect to the image quality. In each iteration, we solve a sub-problem as a MIP to determine the radiation field size and corresponding X-ray tube energy. In the computational experiments, results show further reduction (up to 80%) of the absorbed dose in compare with previous method. Last, there are uncertainties in the medical procedures resulting imprecision of the absorbed dose. We propose a robust formulation to hedge from the worst case absorbed dose while ensuring feasibility. In this part, we investigate a robust approach for the organ motions within a radiology procedure. We minimize the absorbed dose for the critical organs across all input data scenarios which are corresponding to the positioning and size of the organs. The computational results indicate up to 26% increase in the absorbed dose calculated for the robust approach which ensures the feasibility across scenarios.

Effect of respiratory motion on internal radiation dosimetry

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

Xie, Tianwu; Zaidi, Habib, E-mail: habib.zaidi@hcuge.ch; Geneva Neuroscience Center, Geneva University, Geneva CH-1205

Purpose: Estimation of the radiation dose to internal organs is essential for the assessment of radiation risks and benefits to patients undergoing diagnostic and therapeutic nuclear medicine procedures including PET. Respiratory motion induces notable internal organ displacement, which influences the absorbed dose for external exposure to radiation. However, to their knowledge, the effect of respiratory motion on internal radiation dosimetry has never been reported before. Methods: Thirteen computational models representing the adult male at different respiratory phases corresponding to the normal respiratory cycle were generated from the 4D dynamic XCAT phantom. Monte Carlo calculations were performed using the MCNP transportmore » code to estimate the specific absorbed fractions (SAFs) of monoenergetic photons/electrons, the S-values of common positron-emitting radionuclides (C-11, N-13, O-15, F-18, Cu-64, Ga-68, Rb-82, Y-86, and I-124), and the absorbed dose of {sup 18}F-fluorodeoxyglucose ({sup 18}F-FDG) in 28 target regions for both the static (average of dynamic frames) and dynamic phantoms. Results: The self-absorbed dose for most organs/tissues is only slightly influenced by respiratory motion. However, for the lung, the self-absorbed SAF is about 11.5% higher at the peak exhale phase than the peak inhale phase for photon energies above 50 keV. The cross-absorbed dose is obviously affected by respiratory motion for many combinations of source-target pairs. The cross-absorbed S-values for the heart contents irradiating the lung are about 7.5% higher in the peak exhale phase than the peak inhale phase for different positron-emitting radionuclides. For {sup 18}F-FDG, organ absorbed doses are less influenced by respiratory motion. Conclusions: Respiration-induced volume variations of the lungs and the repositioning of internal organs affect the self-absorbed dose of the lungs and cross-absorbed dose between organs in internal radiation dosimetry. The dynamic anatomical model provides more accurate internal radiation dosimetry estimates for the lungs and abdominal organs based on realistic modeling of respiratory motion. This work also contributes to a better understanding of model-induced uncertainties in internal radiation dosimetry.« less

Dosimetric calculations for uranium miners for epidemiological studies.

PubMed

Marsh, J W; Blanchardon, E; Gregoratto, D; Hofmann, W; Karcher, K; Nosske, D; Tomásek, L

2012-05-01

Epidemiological studies on uranium miners are being carried out to quantify the risk of cancer based on organ dose calculations. Mathematical models have been applied to calculate the annual absorbed doses to regions of the lung, red bone marrow, liver, kidney and stomach for each individual miner arising from exposure to radon gas, radon progeny and long-lived radionuclides (LLR) present in the uranium ore dust and to external gamma radiation. The methodology and dosimetric models used to calculate these organ doses are described and the resulting doses for unit exposure to each source (radon gas, radon progeny and LLR) are presented. The results of dosimetric calculations for a typical German miner are also given. For this miner, the absorbed dose to the central regions of the lung is dominated by the dose arising from exposure to radon progeny, whereas the absorbed dose to the red bone marrow is dominated by the external gamma dose. The uncertainties in the absorbed dose to regions of the lung arising from unit exposure to radon progeny are also discussed. These dose estimates are being used in epidemiological studies of cancer in uranium miners.

Analysis of linear energy transfers and quality factors of charged particles produced by spontaneous fission neutrons from 252Cf and 244Pu in the human body.

PubMed

Endo, Akira; Sato, Tatsuhiko

2013-04-01

Absorbed doses, linear energy transfers (LETs) and quality factors of secondary charged particles in organs and tissues, generated via the interactions of the spontaneous fission neutrons from (252)Cf and (244)Pu within the human body, were studied using the Particle and Heavy Ion Transport Code System (PHITS) coupled with the ICRP Reference Phantom. Both the absorbed doses and the quality factors in target organs generally decrease with increasing distance from the source organ. The analysis of LET distributions of secondary charged particles led to the identification of the relationship between LET spectra and target-source organ locations. A comparison between human body-averaged mean quality factors and fluence-averaged radiation weighting factors showed that the current numerical conventions for the radiation weighting factors of neutrons, updated in ICRP103, and the quality factors for internal exposure are valid.

Physics of vascular brachytherapy.

PubMed

Jani, S K

1999-08-01

Basic physics plays an important role in understanding the clinical utility of radioisotopes in brachytherapy. Vascular brachytherapy is a very unique application of localized radiation in that dose levels very close to the source are employed to treat tissues within the arterial wall. This article covers basic physics of radioactivity and differentiates between beta and gamma radiations. Physical parameters such as activity, half-life, exposure and absorbed dose have been explained. Finally, the dose distribution around a point source and a linear source is described. The principles of basic physics are likely to play an important role in shaping the emerging technology and its application in vascular brachytherapy.

SU-E-T-433: Field-In-Field Irradiation for Breast Cancer with VERO-4DRT System: A Feasibility Study

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

Hayashi, N; Mizuno, T; Takada, Y

2015-06-15

Purpose: The Vero-4DRT system is a dedicated system for high precision radiation therapy. However, the field size is limited at 15 cm x 15 cm and shapes by using multi-leaf collimator (MLC) without X-Jaw and Y-Jaw. Therefore VERO-4DRT system is not available to simple wedged irradiation for breast cancer. In this study, we suppose FIF with ring and/or tilt/pan angles whole breast irradiation (FIFWBI). The purpose of this study is to verify the feasibility of FIFWBI with VERO-4DRT system. Methods: As fundamental evaluation, we performed commissioning test with phantom. The absorbed dose evaluation at several reference points and dose distributionmore » including split area were performed. We planned 10 demonstrative shapes in phantom for measuring these contents with i-plan workstation (BrainLAB). As clinical evaluation, the dose distribution and dose indexes were evaluated with actual patient data. Five patients with breast cancer were designed FIFWBI radiotherapy plan with split fields. Then, the dose distribution and dose indexes (including Dmax, Dmin, D95, D5 and Homogeneity index) were evaluated in these plans. Results: As the results of fundamental evaluation, all absorbed dose errors between calculated and measured doses were within 2%. The gamma passing rates with 2 mm/3% criteria in all cases were 96±2%. As the results of clinical evaluation, the values of Dmax, D95, D50, D5, and Homogeneity Index were 41.7±0.90 Gy, 49.4±0.34 Gy, 52.26±0.24 Gy, and 1.39±0.03, respectively. For Japanese breast cancer patients, this technique was feasible. However, the large split region was happened in FIFWBI in case of patient with large breast. Conclusion: We evaluated the FIFWBI technique with VERO-4DRT system. This technique is feasible for Japanese patients, but the patient with large breast should be disagreed with this technique.« less

Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators.

PubMed

Eichmann, Marion; Flühs, Dirk; Spaan, Bernhard

2009-10-01

The therapeutic outcome of the therapy with ophthalmic applicators is highly dependent on the application of a sufficient dose to the tumor, whereas the dose applied to the surrounding tissue needs to be minimized. The goal for the newly developed apparatus described in this work is the determination of the individual applicator surface dose rate distribution with a high spatial resolution and a high precision in dose rate with respect to time and budget constraints especially important for clinical procedures. Inhomogeneities of the dose rate distribution can be detected and taken into consideration for the treatment planning. In order to achieve this, a dose rate profile as well as a surface profile of the applicator are measured and correlated with each other. An instrumental setup has been developed consisting of a plastic scintillator detector system and a newly designed apparatus for guiding the detector across the applicator surface at a constant small distance. It performs an angular movement of detector and applicator with high precision. The measurements of surface dose rate distributions discussed in this work demonstrate the successful operation of the measuring setup. Measuring the surface dose rate distribution with a small distance between applicator and detector and with a high density of measuring points results in a complete and gapless coverage of the applicator surface, being capable of distinguishing small sized spots with high activities. The dosimetrical accuracy of the measurements and its analysis is sufficient (uncertainty in the dose rate in terms of absorbed dose to water is <7%), especially when taking the surgical techniques in positioning of the applicator on the eyeball into account. The method developed so far allows a fully automated quality assurance of eye applicators even under clinical conditions. These measurements provide the basis for future calculation of a full 3D dose rate distribution, which then can be used as input for a refined clinical treatment planning system. The improved dose rate measurements will facilitate a clinical study, which could correlate the therapeutic outcome of a brachytherapy treatment with an applicator and its individual dose rate distribution.

Development of a high precision dosimetry system for the measurement of surface dose rate distribution for eye applicators

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

Eichmann, Marion; Fluehs, Dirk; Spaan, Bernhard

2009-10-15

Purpose: The therapeutic outcome of the therapy with ophthalmic applicators is highly dependent on the application of a sufficient dose to the tumor, whereas the dose applied to the surrounding tissue needs to be minimized. The goal for the newly developed apparatus described in this work is the determination of the individual applicator surface dose rate distribution with a high spatial resolution and a high precision in dose rate with respect to time and budget constraints especially important for clinical procedures. Inhomogeneities of the dose rate distribution can be detected and taken into consideration for the treatment planning. Methods: Inmore » order to achieve this, a dose rate profile as well as a surface profile of the applicator are measured and correlated with each other. An instrumental setup has been developed consisting of a plastic scintillator detector system and a newly designed apparatus for guiding the detector across the applicator surface at a constant small distance. It performs an angular movement of detector and applicator with high precision. Results: The measurements of surface dose rate distributions discussed in this work demonstrate the successful operation of the measuring setup. Measuring the surface dose rate distribution with a small distance between applicator and detector and with a high density of measuring points results in a complete and gapless coverage of the applicator surface, being capable of distinguishing small sized spots with high activities. The dosimetrical accuracy of the measurements and its analysis is sufficient (uncertainty in the dose rate in terms of absorbed dose to water is <7%), especially when taking the surgical techniques in positioning of the applicator on the eyeball into account. Conclusions: The method developed so far allows a fully automated quality assurance of eye applicators even under clinical conditions. These measurements provide the basis for future calculation of a full 3D dose rate distribution, which then can be used as input for a refined clinical treatment planning system. The improved dose rate measurements will facilitate a clinical study, which could correlate the therapeutic outcome of a brachytherapy treatment with an applicator and its individual dose rate distribution.« less

Leuco-crystal-violet micelle gel dosimeters: Component effects on dose-rate dependence

NASA Astrophysics Data System (ADS)

Xie, J. C.; Katz, E. A. B.; Alexander, K. M.; Schreiner, L. J.; McAuley, K. B.

2017-05-01

Designed experiments were performed to produce empirical models for the dose sensitivity, initial absorbance, and dose-rate dependence respectively for leucocrystal violet (LCV) micelle gel dosimeters containing cetyltrimethylammonium bromide (CTAB) and 2,2,2-trichloroethanol (TCE). Previous gels of this type showed dose-rate dependent behaviour, producing an ˜18% increase in dose sensitivity between dose rates of 100 and 600 cGy min-1. Our models predict that the dose rate dependence can be reduced by increasing the concentration of TCE, CTAB and LCV. Increasing concentrations of LCV and CTAB produces a significant increase in dose sensitivity with a corresponding increase in initial absorbance. An optimization procedure was used to determine a nearly dose-rate independent gel which maintained high sensitivity and low initial absorbance. This gel which contains 33 mM CTAB, 1.25 mM LCV, and 96 mM TCE in 25 mM trichloroacetic acid and 4 wt% gelatin showed an increase in dose sensitivity of only 4% between dose rates of 100 and 600 cGy min-1, and provides an 80% greater dose sensitivity compared to Jordan’s standard gels with similar initial absorbance.

Collision-kerma conversion between dose-to-tissue and dose-to-water by photon energy-fluence corrections in low-energy brachytherapy

NASA Astrophysics Data System (ADS)

Giménez-Alventosa, Vicent; Antunes, Paula C. G.; Vijande, Javier; Ballester, Facundo; Pérez-Calatayud, José; Andreo, Pedro

2017-01-01

The AAPM TG-43 brachytherapy dosimetry formalism, introduced in 1995, has become a standard for brachytherapy dosimetry worldwide; it implicitly assumes that charged-particle equilibrium (CPE) exists for the determination of absorbed dose to water at different locations, except in the vicinity of the source capsule. Subsequent dosimetry developments, based on Monte Carlo calculations or analytical solutions of transport equations, do not rely on the CPE assumption and determine directly the dose to different tissues. At the time of relating dose to tissue and dose to water, or vice versa, it is usually assumed that the photon fluence in water and in tissues are practically identical, so that the absorbed dose in the two media can be related by their ratio of mass energy-absorption coefficients. In this work, an efficient way to correlate absorbed dose to water and absorbed dose to tissue in brachytherapy calculations at clinically relevant distances for low-energy photon emitting seeds is proposed. A correction is introduced that is based on the ratio of the water-to-tissue photon energy-fluences. State-of-the art Monte Carlo calculations are used to score photon fluence differential in energy in water and in various human tissues (muscle, adipose and bone), which in all cases include a realistic modelling of low-energy brachytherapy sources in order to benchmark the formalism proposed. The energy-fluence based corrections given in this work are able to correlate absorbed dose to tissue and absorbed dose to water with an accuracy better than 0.5% in the most critical cases (e.g. bone tissue).

Collision-kerma conversion between dose-to-tissue and dose-to-water by photon energy-fluence corrections in low-energy brachytherapy.

PubMed

Giménez-Alventosa, Vicent; Antunes, Paula C G; Vijande, Javier; Ballester, Facundo; Pérez-Calatayud, José; Andreo, Pedro

2017-01-07

The AAPM TG-43 brachytherapy dosimetry formalism, introduced in 1995, has become a standard for brachytherapy dosimetry worldwide; it implicitly assumes that charged-particle equilibrium (CPE) exists for the determination of absorbed dose to water at different locations, except in the vicinity of the source capsule. Subsequent dosimetry developments, based on Monte Carlo calculations or analytical solutions of transport equations, do not rely on the CPE assumption and determine directly the dose to different tissues. At the time of relating dose to tissue and dose to water, or vice versa, it is usually assumed that the photon fluence in water and in tissues are practically identical, so that the absorbed dose in the two media can be related by their ratio of mass energy-absorption coefficients. In this work, an efficient way to correlate absorbed dose to water and absorbed dose to tissue in brachytherapy calculations at clinically relevant distances for low-energy photon emitting seeds is proposed. A correction is introduced that is based on the ratio of the water-to-tissue photon energy-fluences. State-of-the art Monte Carlo calculations are used to score photon fluence differential in energy in water and in various human tissues (muscle, adipose and bone), which in all cases include a realistic modelling of low-energy brachytherapy sources in order to benchmark the formalism proposed. The energy-fluence based corrections given in this work are able to correlate absorbed dose to tissue and absorbed dose to water with an accuracy better than 0.5% in the most critical cases (e.g. bone tissue).

Influence of gamma radiation on the physicochemical and rheological properties of sterculia gum polysaccharides

NASA Astrophysics Data System (ADS)

Singh, Baljit; Sharma, Vikrant

2013-11-01

Keeping in view the influence of gamma radiation on the physiochemical properties of the polysaccharides and their importance in the food and pharmaceutical industry, in the present study attempt has been made to investigate the effects of absorbed dose on FTIR, XRD, SEMs, absorbance, pH, solubility, water absorption capacity, emulsion stability and rheology of sterculia gum. Increase in solubility and decrease in swellability of gum has been observed on increasing the absorbed dose. The emulsion stability has improved for the gum sample irradiated with total dose of 8.1±0.2 kGy. Apparent viscosity of gum solution first increased with increase in dose from 0 to 8.1±0.2 kGy than decreased with regular trends with further increase in total absorbed dose. Flow behavior of gum solution shifted to Newtonian from non-Newtonian with increasing the dose.

Evaluation of variations in absorbed dose and image noise according to patient forms in X-ray computed tomography.

PubMed

Matsubara, Kosuke; Koshida, Kichiro; Suzuki, Masayuki; Hayakawa, Mayumi; Tsujii, Hideo; Yamamoto, Tomoyuki

2005-12-20

Excessive radiation exposure in pediatric computed tomography (CT) scanning has become a serious problem, and it is difficult to select scan parameters for the scanning of small patients such as children. We investigated differences in absorbed dose and standard deviation (SD) in Hounsfield unit (HU) caused by differences in the form of the subject using a body-type phantom with removable body parts. Using four X-ray CT scanners, measurements were made with values from 50 mAs to 300 mAs, with slices of 50 mAs, using scan protocols that were assumed to perform thorough examinations. The results showed that the mAs values and absorbed doses were almost proportional, and the absorbed doses in the phantom without body parts were about 1.1-2.2-fold higher than those of the phantom with body parts at the same points. The SD values obtained indicated that the absorbed doses in the phantom with body parts were 0.3-0.6 times those of the phantom without body parts when the mAs values used were adjusted so that both SD values were the same. The absorbed doses in various patient forms can be estimated from these results, and they will become critical data for the selection of appropriate scan protocols.

A novel method for the evaluation of uncertainty in dose-volume histogram computation.

PubMed

Henríquez, Francisco Cutanda; Castrillón, Silvia Vargas

2008-03-15

Dose-volume histograms (DVHs) are a useful tool in state-of-the-art radiotherapy treatment planning, and it is essential to recognize their limitations. Even after a specific dose-calculation model is optimized, dose distributions computed by using treatment-planning systems are affected by several sources of uncertainty, such as algorithm limitations, measurement uncertainty in the data used to model the beam, and residual differences between measured and computed dose. This report presents a novel method to take them into account. To take into account the effect of associated uncertainties, a probabilistic approach using a new kind of histogram, a dose-expected volume histogram, is introduced. The expected value of the volume in the region of interest receiving an absorbed dose equal to or greater than a certain value is found by using the probability distribution of the dose at each point. A rectangular probability distribution is assumed for this point dose, and a formulation that accounts for uncertainties associated with point dose is presented for practical computations. This method is applied to a set of DVHs for different regions of interest, including 6 brain patients, 8 lung patients, 8 pelvis patients, and 6 prostate patients planned for intensity-modulated radiation therapy. Results show a greater effect on planning target volume coverage than in organs at risk. In cases of steep DVH gradients, such as planning target volumes, this new method shows the largest differences with the corresponding DVH; thus, the effect of the uncertainty is larger.

Absorbed radiation doses to staff after implementation of a radiopharmacy clean room.

PubMed

Ponto, James A

2014-12-01

In response to U.S. Pharmacopeia general chapter <797> standards, a clean room was constructed for our in-house radiopharmacy. Previously, most patient doses were prepared as needed just before injection. Currently, to minimize repeated entries into the clean room, most patient doses are prepared in batches; that is, early morning and noontime preparation of doses to be injected at various times throughout the morning and the afternoon, respectively. Because these patient doses may be prepared well before injection time, radioactive decay necessitates higher amounts of radioactivity to be handled for patient dose preparation. Hence, absorbed radiation doses to staff, all of whom rotate into the radiopharmacy clean room in addition to their regular patient-related activities, were retrospectively evaluated. Monthly dosimetry reports for body (chest badge) and extremities (finger ring) were retrospectively reviewed for each staff member for 12 mo before and 12 mo after implementation of the radiopharmacy clean room. Monthly data were evaluated for average and SD, and 12-mo groups were evaluated using a paired t test. Data for the second 12-mo period were also normalized to the same number of patient doses to account for an increase in procedure volume and were reevaluated. Before the radiopharmacy clean room had been implemented, average monthly absorbed radiation doses to body and extremities were 23 ± 15 mrem (0.23 ± 0.15 mSv) and 93 ± 59 mrem (0.93 ± 0.59 mSv), respectively. After the clean room had been implemented, average monthly absorbed radiation doses increased to 32 ± 16 mrem (0.32 ± 0.16 mSv) (P < 0.001) and 121 ± 89 mrem (1.21 ± 0.89 mSv) (P = 0.0015), respectively. When normalized for procedure volume, average monthly absorbed radiation doses after implementation of the clean room were still higher, at 29 ± 15 mrem (0.29 ± 0.15 mSv) (P = 0.001) and 110 ± 80 mrem (1.10 ± 0.80 mSv) (P = 0.039), respectively. After implementation of a radiopharmacy clean room, absorbed radiation doses to body and extremities increased by 26% and 18%, respectively, even after normalizing for procedure volume. Because absorbed radiation doses from other activities, such as patient dose administration and patient imaging, are assumed to remain relatively constant, these increases in absorbed radiation doses to staff are attributed to changes in work flow after implementation of the radiopharmacy clean room. © 2014 by the Society of Nuclear Medicine and Molecular Imaging, Inc.

Dose-specific transcriptional responses in thyroid tissue in mice after (131)I administration.

PubMed

Rudqvist, Nils; Schüler, Emil; Parris, Toshima Z; Langen, Britta; Helou, Khalil; Forssell-Aronsson, Eva

2015-03-01

In the present investigation, microarray analysis was used to monitor transcriptional activity in thyroids in mice 24 h after (131)I exposure. The aims of this study were to 1) assess the transcriptional patterns associated with (131)I exposure in normal mouse thyroid tissue and 2) propose biomarkers for (131)I exposure of the thyroid. Adult BALB/c nude mice were i.v. injected with 13, 130 or 260 kBq of (131)I and killed 24h after injection (absorbed dose to thyroid: 0.85, 8.5, or 17 Gy). Mock-treated mice were used as controls. Total RNA was extracted from thyroids and processed using the Illumina platform. In total, 497, 546, and 90 transcripts were regulated (fold change ≥1.5) in the thyroid after 0.85, 8.5, and 17 Gy, respectively. These were involved in several biological functions, e.g. oxygen access, inflammation and immune response, and apoptosis/anti-apoptosis. Approximately 50% of the involved transcripts at each absorbed dose level were dose-specific, and 18 transcripts were commonly detected at all absorbed dose levels. The Agpat9, Plau, Prf1, and S100a8 gene expression displayed a monotone decrease in regulation with absorbed dose, and further studies need to be performed to evaluate if they may be useful as dose-related biomarkers for 131I exposure. Distinct and substantial differences in gene expression and affected biological functions were detected at the different absorbed dose levels. The transcriptional profiles were specific for the different absorbed dose levels. We propose that the Agpat9, Plau, Prf1, and S100a8 genes might be novel potential absorbed dose-related biomarkers to (131)I exposure of thyroid. During the recent years, genomic techniques have been developed; however, they have not been fully utilized in nuclear medicine and radiation biology. We have used RNA microarrays to investigate genome-wide transcriptional regulations in thyroid tissue in mice after low, intermediate, and high absorbed doses from (131)I exposure in vivo. Using this approach, we have identified novel biological responses and potential absorbed dose-related biomarkers to (131)I exposure. Our research shows the importance of embracing technological advances and multi-disciplinary collaboration in order to apply them in radiation therapy, nuclear medicine, and radiation biology. This work may contribute with new knowledge of potential normal tissue effects or complications that may occur after exposure to ionizing radiation in diagnostic and therapeutic nuclear medicine, and due to radioactive fallout or accident with radionuclide spread. Copyright © 2014 Elsevier Inc. All rights reserved.

A feasibility study on the use of phantoms with statistical lung masses for determining the uncertainty in the dose absorbed by the lung from broad beams of incident photons and neutrons.

PubMed

Khankook, Atiyeh Ebrahimi; Hakimabad, Hashem Miri; Motavalli, Laleh Rafat

2017-05-01

Computational models of the human body have gradually become crucial in the evaluation of doses absorbed by organs. However, individuals may differ considerably in terms of organ size and shape. In this study, the authors sought to determine the energy-dependent standard deviations due to lung size of the dose absorbed by the lung during external photon and neutron beam exposures. One hundred lungs with different masses were prepared and located in an adult male International Commission on Radiological Protection (ICRP) reference phantom. Calculations were performed using the Monte Carlo N-particle code version 5 (MCNP5). Variation in the lung mass caused great uncertainty: ~90% for low-energy broad parallel photon beams. However, for high-energy photons, the lung-absorbed dose dependency on the anatomical variation was reduced to <1%. In addition, the results obtained indicated that the discrepancy in the lung-absorbed dose varied from 0.6% to 8% for neutron beam exposure. Consequently, the relationship between absorbed dose and organ volume was found to be significant for low-energy photon sources, whereas for higher energy photon sources the organ-absorbed dose was independent of the organ volume. In the case of neutron beam exposure, the maximum discrepancy (of 8%) occurred in the energy range between 0.1 and 5 MeV. © The Author 2017. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Natural gamma-radiation in the Aeolian volcanic arc.

PubMed

Chiozzi, P; Pasquale, V; Verdoya, M; Minato, S

2001-11-01

Pulse-height distributions of gamma-rays, obtained with a field NaI(Tl) scintillation spectrometer in numerous sites of the Lipari and Vulcano islands (Aeolian volcanic arc, Italy), were measured to determine the U, Th and K concentrations of the bedrock and the relative values of the air absorbed dose rate. U is spatially related to both Th and K and the Th/U ratio is on average 3.1-3.5. The magmatic evolution is reflected by the concentration of the three radioelements, as they are more abundant within the more felsic units of the volcanic series. The higher values of U (15.7-20.0 ppm) coincide with higher Th (48.3-65.9 ppm) and K (4.9-6.1%) concentrations associated with rhyolitic rocks of the third cycle (< 50 ky). The air absorbed dose rate varies from 20 to 470 nGy h(-1). The highest values (> 350 nGy h(-1)) are observed on outcrops of rhyolitic obsidian lava flows. The cosmic-ray contribution is also evaluated to estimate the total background radiation dose rate.

A retrospective study on annual evaluation of radiation processing for frozen bone allografts complying to quality system requirements.

PubMed

Ramalingam, Saravana; Mohd, Suhaili; Samsuddin, Sharifah Mazni; Min, N G Wuey; Yusof, Norimah; Mansor, Azura

2015-12-01

Bone allografts have been used widely to fill up essential void in orthopaedic surgeries. The benefit of using allografts to replace and reconstruct musculoskeletal injuries, fractures or disease has obtained overwhelming acceptance from orthopaedic surgeons worldwide. However, bacterial infection and disease transmission through bone allograft transplantation have always been a significant issue. Sterilization by radiation is an effective method to eliminate unwanted microorganisms thus assist in preventing life threatening allograft associated infections. Femoral heads procured from living donors and long bones (femur and tibia) procured from cadaveric donors were sterilized at 25 kGy in compliance with international standard ISO 11137. According to quality requirements, all records of bone banking were evaluated annually. This retrospective study was carried out on annual evaluation of radiation records from 1998 until 2012. The minimum doses absorbed by the bones were ranging from 25.3 to 38.2 kGy while the absorbed maximum doses were from 25.4 to 42.3 kGy. All the bones supplied by our UMMC Bone Bank were sterile at the required minimum dose of 25 kGy. Our analysis on dose variation showed that the dose uniformity ratios in 37 irradiated boxes of 31 radiation batches were in the range of 1.003-1.251, which indicated the doses were well distributed.

Fluctuations in energy loss and their implications for dosimetry and radiobiology

NASA Technical Reports Server (NTRS)

Baily, N. A.; Steigerwalt, J. E.

1972-01-01

Serious consideration of the physics of energy deposition indicates that a fundamental change in the interpretation of absorbed dose is required at least for considerations of effects in biological systems. In addition, theoretical approaches to radiobiology and microdosimetry seem to require statistical considerations incorporating frequency distributions of the magnitude of the event sizes within the volume of interest.

In-flight radiation measurements on STS-60

NASA Technical Reports Server (NTRS)

Badhwar, G. D.; Golightly, M. J.; Konradi, A.; Atwell, W.; Kern, J. W.; Cash, B.; Benton, E. V.; Frank, A. L.; Sanner, D.; Keegan, R. P.;

Skin Dosimetry in Breast Teletherapy on a Phantom Anthropomorphic and Anthropometric Phantom

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

Batista Nogueira, Luciana; Lemos Silva, Hugo Leonardo; Donato da Silva, Sabrina

This paper addresses the breast teletherapy dosimetry. The goal is to evaluate and compare absorbed doses in equivalent skin tissue, TE-skin, of an anthropomorphic and anthropometric breast phantom submitted to breast radiotherapy. The methodology involved the reproduction of a set of tomographic images of the phantom; the elaboration of conformational radiotherapy planning in the SOMAVISION and CadPlan (TPS) software; and the synthetic breast irradiation by parallel opposed fields in 3D conformal teletherapy at 6 MV linear accelerator Clinac-2100 C from VARIAN with prescribed dose (PD) of 180 cGy to the target volume (PTV), referent to the glandular tissue. Radiochromic filmsmore » EBT2 were selected as dosimeters. Two independent calibration processes of films with solid water Gammex 457 plates and water filled box were produced. Curves of optical density (OD) versus absorbed dose were produced. Dosimeters were positioned in the external region of the breast phantom in contact with TE-skin, area of 4.0 cm{sup 2} each. The irradiation process was prepared in duplicate to check the reproducibility of the technique. The radiochromic films were scanned and their response in RGB (Red, Green, Blue) analyzed by the ImageJ software. The optical density was obtained and converted to dose based on the calibration curves. Thus, the spatial dose distribution in the skin was reproduced. The absorbed doses measured on the radiochromic films in TE-skin showed values between upper and lower quadrants at 9 o'clock in the range of 54% of PD, between the upper and lower quadrants 3 o'clock in the range of 72% and 6 o'clock at the lower quadrant in the range of 68 % of PD. The values are ±64% (p <0.05) according to the TPS. It is concluded that the depth dose measured in solid water plates or water box reproduce equivalent dose values for both calibration processes of the radiochromic films. It was observed that the skin received doses ranging from 50% to 78% of the prescribed dose after two parallel opposed irradiation fields. (authors)« less

SU-F-T-222: Dose of Fetus and Infant Following Accidental Intakes of I-131 by the Mother

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

Wang, Y; Hu, P

Purpose: To estimate the calculation of absorbed dose to the fetus and infants from intakes of I-131 by the mother. Thus provide some advice to the radioprotection of radioactive accident. Methods: In this clinical case, a staff of nuclear medicine accidently intake I-131 during (10–12 weeks) and after pregnancy. The infant was born at full term, but both lobes of the thyroid gland were found to be absent (bilobar thyroid agenesis). It was suspected that the fetal thyroid agenesis may be related with mother’s contamination of I-131 during pregnancy. Urine samples for 24h were collected at different times after administeredmore » and radioactivity were measured to calculate the dose of intake I-131. Calculate the intake I-131 by the results of personal TLD dosimeter. We adopted the mean of two calculated results as the I-131 intake. According to the dose of intake I-131 by the mother, effective dose and absorbed dose of thyroid for mother, fetus and infant were calculated. Results: The intake of I-131 was estimated for 8.18 mCi. I-131 intake was calculated for 7.9 mCi based on data of TLD dosimeter. We adopted the mean of two results as the I-131 intake. The final result was 8.0 mCi. Effective dose and absorbed dose of thyroid for mother were 7.3Sv and 164 Gy, effective dose and absorbed dose of thyroid for fetus were 2.035 Sv and 40.7 Gy, effective dose and absorbed dose of thyroid for infant were 16.25 Sv and 355Gy. Conclusion: The intake during pregnancy was about 1mCi. The absorbed dose of thyroid of the mother was 19.5Gy, whereas the effective of infant was estimated for 40.7Gy. The function of the mother’s thyroid was normal after diagnosis. But the infant was diagnosed as bilobar thyroid agenesis.« less

ESR dosimetry for atomic bomb survivors and radiologic technologists

NASA Astrophysics Data System (ADS)

Tatsumi-Miyajima, Junko

1987-06-01

An individual absorbed dose for atomic bomb (A-bomb) survivors and radiologic technologists has been estimated using a new personal dosimetry. This dosimetry is based on the electron spin resonance (ESR) spectroscopy of the CO 33- radicals, which are produced in their teeth by radiation. Measurements were carried out to study the characteristics of the dosimetry; the ESR signals of the CO 33- radicals were stable and increased linearly with the radiation dose. In the evaluation of the absorbed dose, the ESR signals were considered to be a function of photon energy. The absorbed doses in ten cases of A-bomb victims and eight cases of radiologic technologists were determined. For A-bomb survivors, the adsorbed doses, which were estimated using the ESR dosimetry, were consistent with the ones obtained using the calculations of the tissue dose in air of A-bomb, and also with the ones obtained using the chromosome measurements. For radiologic technologists, the absorbed doses, which were estimated using the ESR dosimetry, agreed with the ones calculated using the information on the occupational history and conditions. The advantages of this method are that the absorbed dose can be directly estimated by measuring the ESR signals obtained from the teeth of persons, who are exposed to radiation. Therefore, the ESR dosimetry is useful to estimate the accidental exposure and the long term cumulative dose.

Dosimetry in differentiated thyroid carcinoma (12-1402R)

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

Minguez, Pablo; Genolla, Jose; Celeiro, Jose Javier

2013-01-15

Purpose: The aim of this study has been to perform a dosimetric study in the treatments of differentiated thyroid cancer (DTC) performed in our center in order to find a dose-effect correlation. Methods: Thirty patients treated for DTC with 3700 MBq of {sup 131}I have been included in this study. For reasons of radiological protection all of them spent two nights as inpatients. Dose rate at 1 m from all patients was measured approximately 20 and 44 h after the administration of the radioiodine and a whole body scan in the gamma camera was performed approximately 1 week later. Withmore » those measurements and by using a model of two compartments the activities in thyroid bed remnants and in the whole body were calculated as a function of time. The integration of both activities yields the corresponding cumulated activities. Absorbed doses to thyroid bed remnants and to the whole body can be calculated following the MIRDOSE method-that is, by multiplying the corresponding cumulated activities by the corresponding S factors. Results: The absorbed doses to thyroid bed remnants calculated in this study fall into a very wide range (13-1161 Gy) and showed the highest correlation factors with the following parameters: the absorbed dose rate to thyroid bed remnants, the cumulated activity in thyroid bed remnants, and the maximum radioiodine uptake in thyroid bed remnants. The absorbed doses to the whole body range from 0.12 to 0.23 Gy. The ablation was successful in all patients, and in spite of the wide range of absorbed doses to thyroid bed remnants obtained, no dose-effect correlation could be obtained. Conclusions: Facing DTC treatments from a dosimetric viewpoint in which a predosimetry to calculate the activity of {sup 131}I to be administered is performed is a subject difficult to handle. This statement is based on the fact that although a very wide range of absorbed doses to thyroid bed remnants was obtained (including several absorbed doses well below some dose thresholds previously published to achieve ablation of thyroid bed remnants), ablation of thyroid bed remnants was successful for all patients and therefore no dose-effect correlation could be determined.« less

Distribution of iodine into blood components of the Sprague-Dawley rat differs with the chemical form administered

NASA Technical Reports Server (NTRS)

Thrall, K. D.; Bull, R. J.; Sauer, R. L.

1992-01-01

It has been reported previously that radioactivity derived from iodine distributes differently in the Sprague-Dawley rat depending on the chemical form administered (Thrall and Bull, 1990). In the present communication we report the differential distribution of radioactivity derived from iodine (I2) and iodide (I-) into blood components. Twice as much radioiodine is in the form of I- in the plasma of animals treated with 125I- compared to 125I2-treated rats. No I2 could be detected in the plasma. With an increase in dose, increasing amounts of radioactivity derived from 125I2-treated animals distribute to whole blood compared to equivalent doses of 125I-, reaching a maxima at a dose of 15.8 mumol I/kg body weight. Most of the radioactivity derived from I2 associates with serum proteins and lipids, in particular with albumin and cholesteryl iodide. These data indicate a differential distribution of radioactivity depending on whether it is administered as iodide or iodine. This is inconsistent with the commonly held view that iodine (I2) is reduced to iodide (I-) before it is absorbed systemically from the gastrointestinal tract.

Dose response evaluation of a low-density normoxic polymer gel dosimeter using MRI

NASA Astrophysics Data System (ADS)

Haraldsson, P.; Karlsson, A.; Wieslander, E.; Gustavsson, H.; Bäck, S. Å. J.

2006-02-01

A low-density (~0.6 g cm-3) normoxic polymer gel, containing the antioxidant tetrakis (hydroxymethyl) phosponium (THP), has been investigated with respect to basic absorbed dose response characteristics. The low density was obtained by mixing the gel with expanded polystyrene spheres. The depth dose data for 6 and 18 MV photons were compared with Monte Carlo calculations. A large volume phantom was irradiated in order to study the 3D dose distribution from a 6 MV field. Evaluation of the gel was carried out using magnetic resonance imaging. An approximately linear response was obtained for 1/T2 versus dose in the dose range of 2 to 8 Gy. A small decrease in the dose response was observed for increasing concentrations of THP. A good agreement between measured and Monte Carlo calculated data was obained, both for test tubes and the larger 3D phantom. It was shown that a normoxic polymer gel with a reduced density could be obtained by adding expanded polystyrene spheres. In order to get reliable results, it is very important to have a uniform distribution of the gel and expanded polystyrene spheres in the phantom volume.

Two-dimensional dosimetry of radiotherapeutical proton beams using thermoluminescence foils.

PubMed

Czopyk, L; Klosowski, M; Olko, P; Swakon, J; Waligorski, M P R; Kajdrowicz, T; Cuttone, G; Cirrone, G A P; Di Rosa, F

2007-01-01

In modern radiation therapy such as intensity modulated radiation therapy or proton therapy, one is able to cover the target volume with improved dose conformation and to spare surrounding tissue with help of modern measurement techniques. Novel thermoluminescence dosimetry (TLD) foils, developed from the hot-pressed mixture of LiF:Mg,Cu,P (MCP TL) powder and ethylene-tetrafluoroethylene (ETFE) copolymer, have been applied for 2-D dosimetry of radiotherapeutical proton beams at INFN Catania and IFJ Krakow. A TLD reader with 70 mm heating plate and CCD camera was used to read the 2-D emission pattern of irradiated foils. The absorbed dose profiles were evaluated, taking into account correction factors specific for TLD such as dose and energy response. TLD foils were applied for measuring of dose distributions within an eye phantom and compared with predictions obtained from the MCNPX code and Eclipse Ocular Proton Planning (Varian Medical Systems) clinical radiotherapy planning system. We demonstrate the possibility of measuring 2-D dose distributions with point resolution of about 0.5 x 0.5 mm(2).

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

Baiden, H.N.; Ercanli-Huffman, F.G.

Bioavailability of zinc from sweet potato (SP) roots and leaves were determined, by extrinsic labeling technique, in rats fed control and zinc deficient diets. Weanling male Sprague Dawley (SD) rats (60-75g) were divided into 4 groups, and fed laboratory chow, a control diet (ad libitum and pair fed) and a zinc deficient diet, for 4 weeks. Each group then was divided into at least 2 sub groups, containing 6 rats, which were intubated with one of 3 tubing solutions extrinsically labeled with /sup 65/Zn; baked sweet potato roots (BSPR), raw sweet potato leaves (RSPL) and cooked sweet potato leaves (CSPL).more » Five hours after intubation the rats were sacrificed, blood, liver, testes, spleen, heart, brain, thymus and lungs were removed. Feces, urine, and GI tract contents were collected and their /sup 65/Zn activity was determined in a gamma counter. In all treatment groups zinc bioavailability from BSPR, RSPL or CSPL were not significantly different. Zinc deficient rats absorbed significantly more (P < 0.01) /sup 65/Zn (86-90% of the dose), regardless of type of tubing solution than the pairfed or control animals (35-58% of the dose). The highest retention of /sup 65/Zn was found in the liver (12-20% of absorbed dose), GI tract (6-17% of absorbed dose), kidney (2-8% of absorbed dose), and blood (1-5% of absorbed dose). The lowest retention was found in the brain, heart, thymus and testes. (< 1% of absorbed dose).« less

Fluence correction factors for graphite calorimetry in a low-energy clinical proton beam: I. Analytical and Monte Carlo simulations.

PubMed

Palmans, H; Al-Sulaiti, L; Andreo, P; Shipley, D; Lühr, A; Bassler, N; Martinkovič, J; Dobrovodský, J; Rossomme, S; Thomas, R A S; Kacperek, A

2013-05-21

The conversion of absorbed dose-to-graphite in a graphite phantom to absorbed dose-to-water in a water phantom is performed by water to graphite stopping power ratios. If, however, the charged particle fluence is not equal at equivalent depths in graphite and water, a fluence correction factor, kfl, is required as well. This is particularly relevant to the derivation of absorbed dose-to-water, the quantity of interest in radiotherapy, from a measurement of absorbed dose-to-graphite obtained with a graphite calorimeter. In this work, fluence correction factors for the conversion from dose-to-graphite in a graphite phantom to dose-to-water in a water phantom for 60 MeV mono-energetic protons were calculated using an analytical model and five different Monte Carlo codes (Geant4, FLUKA, MCNPX, SHIELD-HIT and McPTRAN.MEDIA). In general the fluence correction factors are found to be close to unity and the analytical and Monte Carlo codes give consistent values when considering the differences in secondary particle transport. When considering only protons the fluence correction factors are unity at the surface and increase with depth by 0.5% to 1.5% depending on the code. When the fluence of all charged particles is considered, the fluence correction factor is about 0.5% lower than unity at shallow depths predominantly due to the contributions from alpha particles and increases to values above unity near the Bragg peak. Fluence correction factors directly derived from the fluence distributions differential in energy at equivalent depths in water and graphite can be described by kfl = 0.9964 + 0.0024·zw-eq with a relative standard uncertainty of 0.2%. Fluence correction factors derived from a ratio of calculated doses at equivalent depths in water and graphite can be described by kfl = 0.9947 + 0.0024·zw-eq with a relative standard uncertainty of 0.3%. These results are of direct relevance to graphite calorimetry in low-energy protons but given that the fluence correction factor is almost solely influenced by non-elastic nuclear interactions the results are also relevant for plastic phantoms that consist of carbon, oxygen and hydrogen atoms as well as for soft tissues.

Measurement of Absorbed Dose from Radionuclide Solutions Mixed Intimately with the Fbx Dosimeter.

NASA Astrophysics Data System (ADS)

Benedetto, Anthony Richard

Chemical dosimeters are used widely for accurate measurement of large radiation doses due to external beam irradiation from radioisotope sources and from particle accelerators. Their use for measurement of absorbed doses from radioactive solutions mixed in the dosimeter solution was reported as early as 1952, but the large activities needed to produce suitable absorbance values in the relatively insensitive dosimeters of that time discouraged further work. This manuscript reports the results of an investigation into the suitability of the ferrous sulfate-benzoic acid -xylenol orange (FBX) dosimeter for measurement of small absorbed doses caused by radionuclide solutions dissolved in the dosimeter solution. The FBX dosimeter exhibited a linear dose response as a function of activity for two common radiopharmaceuticals, technetium-99m sodium pertechnetate and iodine-131 sodium iodide. Conditions under which the FBX dosimeter may be used with radionuclide solutions were studied and were found to be amenable to routine use by laboratories possessing relatively unsophisticated instrumentation. It appears likely that any radionuclide could be studied using this dosimeter. Finally, potential applications and future research work are suggested, including measurement of absorbed dose from radiopharmaceuticals using realistic human-like phantoms to assess the risk from clinical nuclear medicine studies.

Measurement of dose distribution in the spherical phantom onboard the ISS-KIBO module -MATROSHKA-R in KIBO-

NASA Astrophysics Data System (ADS)

Kodaira, Satoshi; Kawashima, Hajime; Kurano, Mieko; Uchihori, Yukio; Nikolaev, Igor; Ambrozova, Iva; Kitamura, Hisashi; Kartsev, Ivan; Tolochek, Raisa; Shurshakov, Vyacheslav

The measurement of dose equivalent and effective dose during manned space missions on the International Space Station (ISS) is important for evaluating the risk to astronaut health and safety when exposed to space radiation. The dosimetric quantities are constantly changing and strongly depend on the level of solar activity and the various spacecraft- and orbit-dependent parameters such as the shielding distribution in the ISS module, location of the spacecraft within its orbit relative to the Earth, the attitude (orientation) and altitude. Consequently, the continuous monitoring of dosimetric quantities is required to record and evaluate the personal radiation dose for crew members during spaceflight. The dose distributions in the phantom body and on its surface give crucial information to estimate the dose equivalent in the human body and effective dose in manned space mission. We have measured the absorbed dose and dose equivalent rates using passive dosimeters installed in the spherical phantom in Japanese Experiment Module (“KIBO”) of the ISS in the framework of Matroshka-R space experiment. The exposure duration was 114 days from May 21 to September 12, 2012. The phantom consists of tissue-equivalent material covered with a poncho jacket with 32 pockets on its surface and 20 container rods inside of the phantom. The phantom diameter is 35 cm and the mass is 32 kg. The passive dosimeters consisted of a combination of luminescent detectors of Al _{2}O _{3};C OSL and CaSO _{4}:Dy TLD and CR-39 plastic nuclear track detectors. As one of preliminary results, the dose distribution on the phantom surface measured with OSL detectors installed in the jacket pockets is found to be ranging from 340 muGy/day to 260 muGy/day. In this talk, we will present the detail dose distributions, and variations of LET spectra and quality factor obtained outside and inside of the spherical phantom installed in the ISS-KIBO.

Estimation of Organ Absorbed Doses in Patients from 99mTc-diphosphonate Using the Data of MIRDose Software

PubMed Central

Shahbazi-Gahrouei, Daryoush; Cheki, Mohsen; Moslehi, Masoud

2012-01-01

The purpose of this study was to compare estimation of radiation absorbed doses to patients following bone scans with technetium-99m-labeled methylene diphosphonate (MDP) with the estimates given in MIRDose software. In this study, each patient was injected 25 mCi of 99mTc-MDP. Whole-body images from thirty patients were acquired by gamma camera at 10, 60, 90, 180 minutes after 99mTc-MDP injection. To determine the amount of activity in each organ, conjugate view method was applied on images. MIRD equation was then used to estimate absorbed doses in different organs of patients. At the end, absorbed dose values obtained in this study were compared with the data of MIRDose software. The absorbed doses per unit of injected activity (mGy/MBq × 10–4) for liver, kidneys, bladder wall and spleen were 3.86 ± 1.1, 38.73 ± 4.7, 4.16 ± 1.8 and 3.91 ± 1.3, respectively. The results of this study may be useful to estimate the amount of activity that can be administered to the patient and also showed that methods used in the study for absorbed dose calculation is in good agreement with the data of MIRDose software and it is possible to use by a clinician. PMID:23724374

Cellular dosimetry calculations for Strontium-90 using Monte Carlo code PENELOPE.

PubMed

Hocine, Nora; Farlay, Delphine; Boivin, Georges; Franck, Didier; Agarande, Michelle

2014-11-01

To improve risk assessments associated with chronic exposure to Strontium-90 (Sr-90), for both the environment and human health, it is necessary to know the energy distribution in specific cells or tissue. Monte Carlo (MC) simulation codes are extremely useful tools for calculating deposition energy. The present work was focused on the validation of the MC code PENetration and Energy LOss of Positrons and Electrons (PENELOPE) and the assessment of dose distribution to bone marrow cells from punctual Sr-90 source localized within the cortical bone part. S-values (absorbed dose per unit cumulated activity) calculations using Monte Carlo simulations were performed by using PENELOPE and Monte Carlo N-Particle eXtended (MCNPX). Cytoplasm, nucleus, cell surface, mouse femur bone and Sr-90 radiation source were simulated. Cells are assumed to be spherical with the radii of the cell and cell nucleus ranging from 2-10 μm. The Sr-90 source is assumed to be uniformly distributed in cell nucleus, cytoplasm and cell surface. The comparison of S-values calculated with PENELOPE to MCNPX results and the Medical Internal Radiation Dose (MIRD) values agreed very well since the relative deviations were less than 4.5%. The dose distribution to mouse bone marrow cells showed that the cells localized near the cortical part received the maximum dose. The MC code PENELOPE may prove useful for cellular dosimetry involving radiation transport through materials other than water, or for complex distributions of radionuclides and geometries.

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

Real-time measurement and monitoring of absorbed dose for electron beams

NASA Astrophysics Data System (ADS)

Korenev, Sergey; Korenev, Ivan; Rumega, Stanislav; Grossman, Leon

2004-09-01

The real-time method and system for measurement and monitoring of absorbed dose for industrial and research electron accelerators is considered in the report. The system was created on the basis of beam parameters method. The main concept of this method consists in the measurement of dissipated kinetic energy of electrons in the irradiated product, determination of number of electrons and mass of irradiated product in the same cell by following calculation of absorbed dose in the cell. The manual and automation systems for dose measurements are described. The systems are acceptable for all types of electron accelerators.

A system for electron therapy dosimetry surveys with thermoluminescence dosimeters.

PubMed

Soares, C G; Ehrlich, M; Padikal, T N; Gromadzki, Z C

1982-11-01

Radiation-therapy dosimetry surveys employing thermoluminescence dosimeters (TLDs) are now being considered for high-energy electron beams. Using a system of individually calibrated pressed LiF TLDs in a water and a polystyrene phantom, we established that the distortions of depth-dose distributions in non-conducting materials previously observed at high absorbed doses and high dose rates were not detectable in the present geometry at doses and dose rates as much as 40 times higher than those employed in radiation therapy. The system was then used to measure TLD response in water and in polystyrene in the nominal electron-energy range from 7 to 18 MeV. In the water phantom, the well-known trend for TLD response to decrease with increasing electron energy was observed. In the polystyrene phantom, TLD response was found to be independent of electron energy.

Absorbed radiation dose in adults from iodine-131 and iodine-123 orthoiodohippurate and technetium-99m DTPA renography

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

Carlsen, O.

1988-03-01

A mathematic model for evaluation of absorbed dose in radionuclide renography has been developed and programmed for automatic calculation in the computer. Input data to the model are readily available from the results of the renography and, hence, the method described is suitable for individual dose determinations in adults. Apart from the situation with very considerable outflow obstructions (/sup 131/I)OIH single probe renography involves a 15-20 times smaller dose to radiation sensitive organs than (/sup 123/I)OIH gamma camera renography. Further, the latter examination results in a 2-10 times smaller dose than (/sup 99m/Tc)DTPA gamma camera renography under normal outflow conditions.more » Absorbed renal dose is large, approximately 70 mGy, in the three renographies in the borderline case with total outflow obstructions. For comparison, i.v. pyelography, which is the x-ray examination often used instead of radionuclide renography, involves an absorbed dose to ovaries 10-1000 times larger than in radionuclide renography« less

Patient-specific FDG dosimetry for adult males, adult females, and very low birth weight infants

NASA Astrophysics Data System (ADS)

Niven, Erin

Fluorodeoxyglucose is the most commonly used radiopharmaceutical in Positron Emission Tomography, with applications in neurology, cardiology, and oncology. Despite its routine use worldwide, the radiation absorbed dose estimates from FDG have been based primarily on data obtained from two dogs studied in 1977 and 11 adults (most likely males) studied in 1982. In addition, the dose estimates calculated for FDG have been centered on the adult male, with little or no mention of variations in the dose estimates due to sex, age, height, weight, nationality, diet, or pathological condition. Through an extensive investigation into the Medical Internal Radiation Dose schema for calculating absorbed doses, I have developed a simple patient-specific equation; this equation incorporates the parameters necessary for alterations to the mathematical values of the human model to produce an estimate more representative of the individual under consideration. I have used this method to determine the range of absorbed doses to FDG from the collection of a large quantity of biological data obtained in adult males, adult females, and very low birth weight infants. Therefore, a more accurate quantification of the dose to humans from FDG has been completed. My results show that per unit administered activity, the absorbed dose from FDG is higher for infants compared to adults, and the dose for adult women is higher than for adult men. Given an injected activity of approximately 3.7 MBq kg-1, the doses for adult men, adult women, and full-term newborns would be on the order of 5.5, 7.1, and 2.8 mSv, respectively. These absorbed doses are comparable to the doses received from other nuclear medicine procedures.

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

Evaluation of dosimetric properties of shielding disk used in intraoperative electron radiotherapy: A Monte Carlo study.

PubMed

Robatjazi, Mostafa; Baghani, Hamid Reza; Mahdavic, Seied Rabi; Felici, Giuseppe

2018-05-01

A shielding disk is used for IOERT procedures to absorb radiation behind the target and protect underlying healthy tissues. Setup variation of shielding disk can affect the corresponding in-vivo dose distribution. In this study, the changes of dosimetric parameters due to the disk setup variations is evaluated using EGSnrc Monte Carlo (MC) code. The results can help treatment team to decide about the level of accuracy in the setup procedure and delivered dose to the target volume during IOERT. Copyright © 2018 Elsevier Ltd. All rights reserved.

Measurement of the distribution of radiation in the area surrounding the target mass using optically stimulated luminescence technique.

PubMed

Tanır, A Güneş; Yedek, Hatice; Koç, Kemal; Bölükdemir, M Hicabi

2017-01-01

The scattered doses received by the area surrounding the target that has been subjected to x-rays were investigated. Two experiments were carried out: 1- Al 2 O 3 : C was used as dosimeter and the luminescence counts was measured using both the RisØ TL/OSL system and an ion chamber. 2- BeO aliquots were used and the counts were read using the IBEOX/OSL system. According to the results, the doses absorbed by the area surrounding the target are significantly amount. Copyright © 2016 Elsevier Ltd. All rights reserved.

A graphite calorimeter for absolute measurements of absorbed dose to water: application in medium-energy x-ray filtered beams.

PubMed

Pinto, M; Pimpinella, M; Quini, M; D'Arienzo, M; Astefanoaei, I; Loreti, S; Guerra, A S

2016-02-21

The Italian National Institute of Ionizing Radiation Metrology (ENEA-INMRI) has designed and built a graphite calorimeter that, in a water phantom, has allowed the determination of the absorbed dose to water in medium-energy x-rays with generating voltages from 180 to 250 kV. The new standard is a miniaturized three-bodies calorimeter, with a disc-shaped core of 21 mm diameter and 2 mm thickness weighing 1.134 g, sealed in a PMMA waterproof envelope with air-evacuated gaps. The measured absorbed dose to graphite is converted into absorbed dose to water by means of an energy-dependent conversion factor obtained from Monte Carlo simulations. Heat-transfer correction factors were determined by FEM calculations. At a source-to-detector distance of 100 cm, a depth in water of 2 g cm(-2), and at a dose rate of about 0.15 Gy min(-1), results of calorimetric measurements of absorbed dose to water, D(w), were compared to experimental determinations, D wK, obtained via an ionization chamber calibrated in terms of air kerma, according to established dosimetry protocols. The combined standard uncertainty of D(w) and D(wK) were estimated as 1.9% and 1.7%, respectively. The two absorbed dose to water determinations were in agreement within 1%, well below the stated measurement uncertainties. Advancements are in progress to extend the measurement capability of the new in-water-phantom graphite calorimeter to other filtered medium-energy x-ray qualities and to reduce the D(w) uncertainty to around 1%. The new calorimeter represents the first implementation of in-water-phantom graphite calorimetry in the kilovoltage range and, allowing independent determinations of D(w), it will contribute to establish a robust system of absorbed dose to water primary standards for medium-energy x-ray beams.

Materials Degradation in the Jovian Radiation Environment

NASA Technical Reports Server (NTRS)

Miloshevsky, Gennady; Caffrey, Jarvis A.; Jones, Jonathan E.; Zoladz, Thomas F.

2017-01-01

The radiation environment of Jupiter represents a significant hazard for Europa Lander deorbit stage components, and presents a significant potential mission risk. The radiolytic degradation of ammonium perchlorate (AP) oxidizer in solid propellants may affect its properties and performance. The Monte Carlo code MONSOL was used for modeling of laboratory experiments on the electron irradiation of propellant samples. An approach for flattening dose profiles along the depth of irradiated samples is proposed. Depth-dose distributions produced by Jovian electrons in multi-layer slabs of materials are calculated. It is found that the absorbed dose in a particular slab is significantly affected by backscattered electrons and photons from neighboring slabs. The dose and radiolytic decomposition of AP crystals are investigated and radiation-induced chemical yields and weight percent of radical products are reported.

Estimation of background radiation doses for the Peninsular Malaysia's population by ESR dosimetry of tooth enamel.

PubMed

Rodzi, Mohd; Zhumadilov, Kassym; Ohtaki, Megu; Ivannikov, Alexander; Bhattacharjee, Deborshi; Fukumura, Akifumi; Hoshi, Masaharu

2011-08-01

Background radiation dose is used in dosimetry for estimating occupational doses of radiation workers or determining radiation dose of an individual following accidental exposure. In the present study, the absorbed dose and the background radiation level are determined using the electron spin resonance (ESR) method on tooth samples. The effect of using different tooth surfaces and teeth exposed with single medical X-rays on the absorbed dose are also evaluated. A total of 48 molars of position 6-8 were collected from 13 district hospitals in Peninsular Malaysia. Thirty-six teeth had not been exposed to any excessive radiation, and 12 teeth had been directly exposed to a single X-ray dose during medical treatment prior to extraction. There was no significant effect of tooth surfaces and exposure with single X-rays on the measured absorbed dose of an individual. The mean measured absorbed dose of the population is 34 ± 6.2 mGy, with an average tooth enamel age of 39 years. From the slope of a regression line, the estimated annual background dose for Peninsular Malaysia is 0.6 ± 0.3 mGy y(-1). This value is slightly lower than the yearly background dose for Malaysia, and the radiation background dose is established by ESR tooth measurements on samples from India and Russia.

Monte Carlo calculation of dose rate conversion factors for external exposure to photon emitters in soil

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

Clovas, A.; Zanthos, S.; Antonopoulos-Domis, M.

2000-03-01

The dose rate conversion factors {dot D}{sub CF} (absorbed dose rate in air per unit activity per unit of soil mass, nGy h{sup {minus}1} per Bq kg{sup {minus}1}) are calculated 1 m above ground for photon emitters of natural radionuclides uniformly distributed in the soil. Three Monte Carlo codes are used: (1) The MCNP code of Los Alamos; (2) The GEANT code of CERN; and (3) a Monte Carlo code developed in the Nuclear Technology Laboratory of the Aristotle University of Thessaloniki. The accuracy of the Monte Carlo results is tested by the comparison of the unscattered flux obtained bymore » the three Monte Carlo codes with an independent straightforward calculation. All codes and particularly the MCNP calculate accurately the absorbed dose rate in air due to the unscattered radiation. For the total radiation (unscattered plus scattered) the {dot D}{sub CF} values calculated from the three codes are in very good agreement between them. The comparison between these results and the results deduced previously by other authors indicates a good agreement (less than 15% of difference) for photon energies above 1,500 keV. Antithetically, the agreement is not as good (difference of 20--30%) for the low energy photons.« less

Plasma Membrane Permeabilization by 60- and 600-ns Electric Pulses Is Determined by the Absorbed Dose

PubMed Central

Ibey, Bennett L.; Xiao, Shu; Schoenbach, Karl H.; Murphy, Michael R.; Pakhomov, Andrei G.

2008-01-01

We explored how the effect of plasma membrane permeabilization by nanosecond-duration electric pulses (nsEP) depends on the physical characteristics of exposure. The resting membrane resistance (Rm) and membrane potential (MP) were measured in cultured GH3 and CHO cells by conventional whole-cell patch-clamp technique. Intact cells were exposed to a single nsEP (60 or 600 ns duration, 0-22 kV/cm), followed by patch-clamp measurements after a 2-3 min delay. Consistent with earlier findings, nsEP caused long-lasting Rm decrease, accompanied by the loss of MP. The threshold for these effects was about 6 kV/cm for 60 ns pulses, and about 1 kV/cm for 600 ns pulses. Further analysis established that it was neither pulse duration nor the E-field amplitude per se, but the absorbed dose that determined the magnitude of the biological effect. In other words, exposure to nsEP at either pulse duration caused equal effects if the absorbed doses were equal. The threshold absorbed dose to produce plasma membrane effects in either GH3 or CHO cells at either pulse duration was found to be at or below 10 mJ/g. Despite being determined by the dose, the nsEP effect clearly is not thermal, as the maximum heating at the threshold dose is less than 0.01 °C. The use of the absorbed dose as a universal exposure metric may help to compare and quantify nsEP sensitivity of different cell types and of cells in different physiological conditions. The absorbed dose may also prove to be a more useful metric than the incident E-field in determining safety limits for high peak, lowaverage power EMF emissions. PMID:18839412

A calibration method for realistic neutron dosimetry in radiobiological experiments assisted by MCNP simulation.

PubMed

Shahmohammadi Beni, Mehrdad; Krstic, Dragana; Nikezic, Dragoslav; Yu, Kwan Ngok

2016-09-01

Many studies on biological effects of neutrons involve dose responses of neutrons, which rely on accurately determined absorbed doses in the irradiated cells or living organisms. Absorbed doses are difficult to measure, and are commonly surrogated with doses measured using separate detectors. The present work describes the determination of doses absorbed in the cell layer underneath a medium column (D A ) and the doses absorbed in an ionization chamber (D E ) from neutrons through computer simulations using the MCNP-5 code, and the subsequent determination of the conversion coefficients R (= D A /D E ). It was found that R in general decreased with increase in the medium thickness, which was due to elastic and inelastic scattering. For 2-MeV neutrons, conspicuous bulges in R values were observed at medium thicknesses of about 500, 1500, 2500 and 4000 μm, and these were attributed to carbon, oxygen and nitrogen nuclei, and were reflections of spikes in neutron interaction cross sections with these nuclei. For 0.1-MeV neutrons, no conspicuous bulges in R were observed (except one at ~2000 μm that was due to photon interactions), which was explained by the absence of prominent spikes in the interaction cross-sections with these nuclei for neutron energies <0.1 MeV. The ratio R could be increased by ~50% for small medium thickness if the incident neutron energy was reduced from 2 MeV to 0.1 MeV. As such, the absorbed doses in cells (D A ) would vary with the incident neutron energies, even when the absorbed doses shown on the detector were the same. © The Author 2016. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

A calibration method for realistic neutron dosimetry in radiobiological experiments assisted by MCNP simulation

PubMed Central

Shahmohammadi Beni, Mehrdad; Krstic, Dragana; Nikezic, Dragoslav; Yu, Kwan Ngok

2016-01-01

Many studies on biological effects of neutrons involve dose responses of neutrons, which rely on accurately determined absorbed doses in the irradiated cells or living organisms. Absorbed doses are difficult to measure, and are commonly surrogated with doses measured using separate detectors. The present work describes the determination of doses absorbed in the cell layer underneath a medium column (DA) and the doses absorbed in an ionization chamber (DE) from neutrons through computer simulations using the MCNP-5 code, and the subsequent determination of the conversion coefficients R (= DA/DE). It was found that R in general decreased with increase in the medium thickness, which was due to elastic and inelastic scattering. For 2-MeV neutrons, conspicuous bulges in R values were observed at medium thicknesses of about 500, 1500, 2500 and 4000 μm, and these were attributed to carbon, oxygen and nitrogen nuclei, and were reflections of spikes in neutron interaction cross sections with these nuclei. For 0.1-MeV neutrons, no conspicuous bulges in R were observed (except one at ~2000 μm that was due to photon interactions), which was explained by the absence of prominent spikes in the interaction cross-sections with these nuclei for neutron energies <0.1 MeV. The ratio R could be increased by ~50% for small medium thickness if the incident neutron energy was reduced from 2 MeV to 0.1 MeV. As such, the absorbed doses in cells (DA) would vary with the incident neutron energies, even when the absorbed doses shown on the detector were the same. PMID:27380801

ANALYSIS OF UNCERTAINTIES IN DOSE RECONSTRUCTION FROM BIOMARKERS: IMPACT ON STUDY DESIGN

EPA Science Inventory

The absorbed dose is defined as the quantity which has passed through the barriers (skin, GI tract, The absorbed dose of a pesticide can be estimated from its established urinary biomarker. ungs). For an exposure study, there are several options for biomarker collection, each w...

Monte Carlo MCNP-4B-based absorbed dose distribution estimates for patient-specific dosimetry.

PubMed

Yoriyaz, H; Stabin, M G; dos Santos, A

2001-04-01

This study was intended to verify the capability of the Monte Carlo MCNP-4B code to evaluate spatial dose distribution based on information gathered from CT or SPECT. A new three-dimensional (3D) dose calculation approach for internal emitter use in radioimmunotherapy (RIT) was developed using the Monte Carlo MCNP-4B code as the photon and electron transport engine. It was shown that the MCNP-4B computer code can be used with voxel-based anatomic and physiologic data to provide 3D dose distributions. This study showed that the MCNP-4B code can be used to develop a treatment planning system that will provide such information in a time manner, if dose reporting is suitably optimized. If each organ is divided into small regions where the average energy deposition is calculated with a typical volume of 0.4 cm(3), regional dose distributions can be provided with reasonable central processing unit times (on the order of 12-24 h on a 200-MHz personal computer or modest workstation). Further efforts to provide semiautomated region identification (segmentation) and improvement of marrow dose calculations are needed to supply a complete system for RIT. It is envisioned that all such efforts will continue to develop and that internal dose calculations may soon be brought to a similar level of accuracy, detail, and robustness as is commonly expected in external dose treatment planning. For this study we developed a code with a user-friendly interface that works on several nuclear medicine imaging platforms and provides timely patient-specific dose information to the physician and medical physicist. Future therapy with internal emitters should use a 3D dose calculation approach, which represents a significant advance over dose information provided by the standard geometric phantoms used for more than 20 y (which permit reporting of only average organ doses for certain standardized individuals)

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

Hobbs, R; Le, Y; Armour, E

Purpose: Dose-response studies in radiation therapy are typically using single response values for tumors across ensembles of tumors. Using the high dose rate (HDR) treatment plan dose grid and pre- and post-therapy FDG-PET images, we look for correlations between voxelized dose and FDG uptake response in individual tumors. Methods: Fifteen patients were treated for localized rectal cancer using 192Ir HDR brachytherapy in conjunction with surgery. FDG-PET images were acquired before HDR therapy and 6–8 weeks after treatment (prior to surgery). Treatment planning was done on a commercial workstation and the dose grid was calculated. The two PETs and the treatmentmore » dose grid were registered to each other using non-rigid registration. The difference in PET SUV values before and after HDR was plotted versus absorbed radiation dose for each voxel. The voxels were then separated into bins for every 400 cGy of absorbed dose and the bin average values plotted similarly. Results: Individual voxel doses did not correlate with PET response; however, when group into tumor subregions corresponding to dose bins, eighty percent of the patients showed a significant positive correlation (R2 > 0) between PET uptake difference in the targeted region and the absorbed dose. Conclusion: By considering larger ensembles of voxels, such as organ average absorbed dose or the dose bins considered here, valuable information may be obtained. The dose-response correlations as measured by FDG-PET difference potentially underlines the importance of FDG-PET as a measure of response, as well as the value of voxelized information.« 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

Female gonadal shielding with automatic exposure control increases radiation risks.

PubMed

Kaplan, Summer L; Magill, Dennise; Felice, Marc A; Xiao, Rui; Ali, Sayed; Zhu, Xiaowei

2018-02-01

Gonadal shielding remains common, but current estimates of gonadal radiation risk are lower than estimated risks to colon and stomach. A female gonadal shield may attenuate active automatic exposure control (AEC) sensors, resulting in increased dose to colon and stomach as well as to ovaries outside the shielded area. We assess changes in dose-area product (DAP) and absorbed organ dose when female gonadal shielding is used with AEC for pelvis radiography. We imaged adult and 5-year-old equivalent dosimetry phantoms using pelvis radiograph technique with AEC in the presence and absence of a female gonadal shield. We recorded DAP and mAs and measured organ absorbed dose at six internal sites using film dosimetry. Female gonadal shielding with AEC increased DAP 63% for the 5-year-old phantom and 147% for the adult phantom. Absorbed organ dose at unshielded locations of colon, stomach and ovaries increased 21-51% in the 5-year-old phantom and 17-100% in the adult phantom. Absorbed organ dose sampled under the shield decreased 67% in the 5-year-old phantom and 16% in the adult phantom. Female gonadal shielding combined with AEC during pelvic radiography increases absorbed dose to organs with greater radiation sensitivity and to unshielded ovaries. Difficulty in proper use of gonadal shields has been well described, and use of female gonadal shielding may be inadvisable given the risks of increasing radiation.

The Molecular Effect of Diagnostic Absorbed Doses from 131I on Papillary Thyroid Cancer Cells In Vitro.

PubMed

Stasiołek, Mariusz; Adamczewski, Zbigniew; Śliwka, Przemysław W; Puła, Bartosz; Karwowski, Bolesław; Merecz-Sadowska, Anna; Dedecjus, Marek; Lewiński, Andrzej

2017-06-15

Diagnostic whole-body scan is a standard procedure in patients with thyroid cancer prior to the application of a therapeutic dose of 131 I. Unfortunately, administration of the radioisotope in a diagnostic dose may decrease further radioiodine uptake-the phenomenon called "thyroid stunning". We estimated radiation absorbed dose-dependent changes in genetic material, in particular in the sodium iodide symporter (NIS) gene promoter, and the NIS protein level in a K1 cell line derived from the metastasis of a human papillary thyroid carcinoma exposed to 131 I in culture. The different activities applied were calculated to result in absorbed doses of 5, 10 and 20 Gy. Radioiodine did not affect the expression of the NIS gene at the mRNA level, however, we observed significant changes in the NIS protein level in K1 cells. The decrease of the NIS protein level observed in the cells subjected to the lowest absorbed dose was paralleled by a significant increase in 8-oxo-dG concentrations ( p < 0.01) and followed by late activation of the DNA repair pathways. Our findings suggest that the impact of 131 I radiation on thyroid cells, in the range compared to doses absorbed during diagnostic procedures, is not linear and depends on various factors including the cellular components of thyroid pathology.

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

Vostrotin, Vadim; Birchall, Alan; Zhdanov, Alexey

The distribution of calculated internal doses was determined for 8043 Mayak Production Associate (Mayak PA) workers according to the epidemiological cohorts and groups of raw data used as well as the type of industrial compounds of inhaled aerosols. Statistical characteristics of point estimates of accumulated doses to 17 different tissues and organs and the uncertainty ranges were calculated. Under the MWDS-2013 dosimetry system, the mean accumulated lung dose was 185585 mGy, with a median value of 31 mGy and a maximum of 8980 mGy maximum. The ranges of relative standard uncertainty were: from 40 to 2200% for accumulated lung dose,more » from 25-90% to 2600-3000% for accumulated dose to different regions of respiratory tract, from 13-18% to 2300-2500% for systemic organs and tissues. The Mayak PA workers accumulated internal plutonium lung dose is shown to be close to lognormal. The accumulated internal plutonium dose to systemic organs was close to a log-triangle. The dependency of uncertainty of accumulated absorbed lung and liver doses on the dose estimates itself is also shown. The accumulated absorbed doses to lung, alveolar-interstitial region, liver, bone surface cells and red bone marrow, calculated both with MWDS-2013 and MWDS-2008 have been compared. In general, the accumulated lung doses increased by a factor of 1.8 in median value, while the accumulated doses to systemic organs decreased by factor of 1.3-1.4 in median value. For the cases with identical initial data, accumulated lung doses increased by a factor of 2.1 in median value, while accumulated doses to systemic organs decreased by 8-13% in median value. For the cases with both identical initial data and all of plutonium activity in urine measurements above the decision threshold, accumulated lung doses increased by a factor of 2.8 in median value, while accumulated doses to systemic organs increased by 6-12% in median value.« less

Fluence-to-Absorbed Dose Conversion Coefficients for Use in Radiological Protection of Embryo and Foetus Against External Exposure to Muons from 20MeV to 50GeV

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

Chen Jing

2008-08-07

This study used the Monte-Carlo code MCNPX to determine mean absorbed doses to the embryo and foetus when the mother is exposed to external muon fields. Monoenergetic muons ranging from 20 MeV to 50 GeV were considered. The irradiation geometries include anteroposterior (AP), postero-anterior (PA), lateral (LAT), rotational (ROT), isotropic (ISO), and top-down (TOP). At each of these irradiation geometries, absorbed doses to the foetal body were calculated for the embryo of 8 weeks and the foetus of 3, 6 or 9 months, respectively. Muon fluence-to-absorbed-dose conversion coefficients were derived for the four prenatal ages. Since such conversion coefficients aremore » yet unknown, the results presented here fill a data gap.« less

Editor's choice--Use of disposable radiation-absorbing surgical drapes results in significant dose reduction during EVAR procedures.

PubMed

Kloeze, C; Klompenhouwer, E G; Brands, P J M; van Sambeek, M R H M; Cuypers, P W M; Teijink, J A W

2014-03-01

Because of the increasing number of interventional endovascular procedures with fluoroscopy and the corresponding high annual dose for interventionalists, additional dose-protecting measures are desirable. The purpose of this study was to evaluate the effect of disposable radiation-absorbing surgical drapes in reducing scatter radiation exposure for interventionalists and supporting staff during an endovascular aneurysm repair (EVAR) procedure. This was a randomized control trial in which 36 EVAR procedures were randomized between execution with and without disposable radiation-absorbing surgical drapes (Radpad: Worldwide Innovations & Technologies, Inc., Kansas City, US, type 5511A). Dosimetric measurements were performed on the interventionalist (hand and chest) and theatre nurse (chest) with and without the use of the drapes to obtain the dose reduction and effect on the annual dose caused by the drapes. Use of disposable radiation-absorbing surgical drapes resulted in dose reductions of 49%, 55%, and 48%, respectively, measured on the hand and chest of the interventionalist and the chest of the theatre nurse. The use of disposable radiation-absorbing surgical drapes significantly reduces scatter radiation exposure for both the interventionalist and the supporting staff during EVAR procedures. Copyright © 2013 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

A general model for stray dose calculation of static and intensity-modulated photon radiation.

PubMed

Hauri, Pascal; Hälg, Roger A; Besserer, Jürgen; Schneider, Uwe

2016-04-01

There is an increasing number of cancer survivors who are at risk of developing late effects caused by ionizing radiation such as induction of second tumors. Hence, the determination of out-of-field dose for a particular treatment plan in the patient's anatomy is of great importance. The purpose of this study was to analytically model the stray dose according to its three major components. For patient scatter, a mechanistic model was developed. For collimator scatter and head leakage, an empirical approach was used. The models utilize a nominal beam energy of 6 MeV to describe two linear accelerator types of a single vendor. The parameters of the models were adjusted using ionization chamber measurements registering total absorbed dose in simple geometries. Whole-body dose measurements using thermoluminescent dosimeters in an anthropomorphic phantom for static and intensity-modulated treatment plans were compared to the 3D out-of-field dose distributions calculated by a combined model. The absolute mean difference between the whole-body predicted and the measured out-of-field dose of four different plans was 11% with a maximum difference below 44%. Computation time of 36 000 dose points for one field was around 30 s. By combining the model-calculated stray dose with the treatment planning system dose, the whole-body dose distribution can be viewed in the treatment planning system. The results suggest that the model is accurate, fast and can be used for a wide range of treatment modalities to calculate the whole-body dose distribution for clinical analysis. For similar energy spectra, the mechanistic patient scatter model can be used independently of treatment machine or beam orientation.

Evaluation of effective dose with chest digital tomosynthesis system using Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Kim, Dohyeon; Jo, Byungdu; Lee, Youngjin; Park, Su-Jin; Lee, Dong-Hoon; Kim, Hee-Joung

2015-03-01

Chest digital tomosynthesis (CDT) system has recently been introduced and studied. This system offers the potential to be a substantial improvement over conventional chest radiography for the lung nodule detection and reduces the radiation dose with limited angles. PC-based Monte Carlo program (PCXMC) simulation toolkit (STUK, Helsinki, Finland) is widely used to evaluate radiation dose in CDT system. However, this toolkit has two significant limits. Although PCXMC is not possible to describe a model for every individual patient and does not describe the accurate X-ray beam spectrum, Geant4 Application for Tomographic Emission (GATE) simulation describes the various size of phantom for individual patient and proper X-ray spectrum. However, few studies have been conducted to evaluate effective dose in CDT system with the Monte Carlo simulation toolkit using GATE. The purpose of this study was to evaluate effective dose in virtual infant chest phantom of posterior-anterior (PA) view in CDT system using GATE simulation. We obtained the effective dose at different tube angles by applying dose actor function in GATE simulation which was commonly used to obtain the medical radiation dosimetry. The results indicated that GATE simulation was useful to estimate distribution of absorbed dose. Consequently, we obtained the acceptable distribution of effective dose at each projection. These results indicated that GATE simulation can be alternative method of calculating effective dose in CDT applications.

A new method for determining dose rate distribution from radioimmuno-therapy using radiochromic media

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

Mayer, R.; Dillehay, L.E.; Shao, Y.

The purpose of this study is to describe and evaluate a new, simple, inexpensive method for directly measuring the radiation dose and its spatial distribution generated from explanted tissues of animals previously injected with radiolabeled immunoconjugates or other agents. This technique uses the newly developed radiochromic dye medium (Gafchromic[trademark]) which responds reproducibly for therapeutic dose exposures, has high spatial resolution, does not require film processing, and is relatively insensitive to ambient light. The authors have evaluated the dose distribution from LS174T tumors and selected normal tissues in nude mice previously injected with [sup 90]Y labeled anti-carcinoembryonic antigen antibodies. Individual tissuesmore » from sacrificed animals are halved and the flat section of the tissue is placed onto the dosimetry media and then frozen. The dosimetry medium is exposed to beta and Bremsstrahlung radiation originating from the frozen tissues. The relative darkening of the dosimetry medium depends on the dose deposited in the film. The dosimetry medium is scanned with a commercial flatbed scanner and the image intensity is digitally stored and quantitatively analyzed. Isodose curves are generated and compared to the actual tissue outline. The absorbed dose distribution due to [sup 90]Y exposure show only slight gradients in the interior of the tissue, with a markedly decreasing dose near the edges of the tissue. In addition, the isodose curves follow the tissue outline except in regions having radii of curvature smaller than the range of the beta-particle (R90 = 5 mm). These results suggest that the shape of the tumor, and its curvature, are important in determining the minimum dose delivered to the tumor by radiation from [sup 90]Y monoclonal antibodies, and hence in evaluating the tumor response to the radiation. 28 refs., 8 figs.« less

Neutron skyshine measurements at Fermilab.

PubMed

Cossairt, J D; Coulson, L V

1985-02-01

Neutron skyshine has been a significant source of environmental radiation exposure at many high-energy proton accelerators. A particularly troublesome source of skyshine neutrons has existed at Fermilab during operation of the 400-GeV high-energy physics program. This paper reports on several measurements of this source made with a DePangher precision long counter at large distances. The spatial distribution of the neutron skyshine can approximately be described as an inverse square law dependence multiplied by an exponential with an approximate attenuation length of 1200 +/- 300 m. The absolute magnitude of the distributions can be matched directly to the conventionally measured absorbed dose distribution near the source.

Diamond detector in absorbed dose measurements in high-energy linear accelerator photon and electron beams.

PubMed

Ravichandran, Ramamoorthy; Binukumar, John Pichy; Al Amri, Iqbal; Davis, Cheriyathmanjiyil Antony

2016-03-08

Diamond detectors (DD) are preferred in small field dosimetry of radiation beams because of small dose profile penumbras, better spatial resolution, and tissue-equivalent properties. We investigated a commercially available 'microdiamond' detector in realizing absorbed dose from first principles. A microdiamond detector, type TM 60019 with tandem electrometer is used to measure absorbed doses in water, nylon, and PMMA phantoms. With sensitive volume 0.004 mm3, radius 1.1mm, thickness 1 x10(-3) mm, the nominal response is 1 nC/Gy. It is assumed that the diamond detector could collect total electric charge (nC) developed during irradiation at 0 V bias. We found that dose rate effect is less than 0.7% for changing dose rate by 500 MU/min. The reproducibility in obtaining readings with diamond detector is found to be ± 0.17% (1 SD) (n = 11). The measured absorbed doses for 6 MV and 15 MV photons arrived at using mass energy absorption coefficients and stop-ping power ratios compared well with Nd, water calibrated ion chamber measured absorbed doses within 3% in water, PMMA, and nylon media. The calibration factor obtained for diamond detector confirmed response variation is due to sensitivity due to difference in manufacturing process. For electron beams, we had to apply ratio of electron densities of water to carbon. Our results qualify diamond dosimeter as a transfer standard, based on long-term stability and reproducibility. Based on micro-dimensions, we recommend these detectors for pretreatment dose verifications in small field irradiations like stereotactic treatments with image guidance.

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.

Operating characteristics of tube-current-modulation techniques when scanning simple-shaped phantoms

NASA Astrophysics Data System (ADS)

Matsubara, Kosuke; Koshida, Kichiro; Lin, Pei-Jan Paul; Fukuda, Atsushi

2015-07-01

Our objective was to investigate the operating characteristics of tube current modulation (TCM) in computed tomography (CT) when scanning two types of simple-shaped phantoms. A tissueequivalent elliptical phantom and a homogeneous cylindrical step phantom comprising 16-, 24-, and 32-cm-diameter polymethyl methacrylate (PMMA) phantoms were scanned by using an automatic exposure control system with longitudinal (z-) and angular-longitudinal (xyz-) TCM and with a fixed tube current. The axial dose distribution throughout the elliptical phantom and the longitudinal dose distribution at the center of the cylindrical step phantom were measured by using a solid-state detector. Image noise was quantitatively measured at eight regions in the elliptical phantom and at 90 central regions in contiguous images over the full z extent of the cylindrical step phantom. The mean absorbed doses and the standard deviations in the elliptical phantom with z- and xyz-TCM were 12.3' 3.7 and 11.3' 3.5 mGy, respectively. When TCM was activated, some differences were observed in the absorbed doses of the left and the right measurement points. The average image noises in Hounsfield units (HU) and the standard deviations were 15.2' 2.4 and 15.9' 2.4 HU when using z- and xyz-TCM, respectively. With respect to the cylindrical step phantom under z-TCM, there were sudden decreases followed by increases in image noise at the interfaces with the 24- and 16-cm-diameter phantoms. The image noise of the 24-cm-diameter phantom was, relatively speaking, higher than those of the 16- and 32-cm-diameter phantoms. The simple-shaped phantoms used in this study can be employed to investigate the operating characteristics of automatic exposure control systems when specialized phantoms designed for that purpose are not available.

Assessment of an organ-based tube current modulation in thoracic computed tomography.

PubMed

Matsubara, Kosuke; Sugai, Mai; Toyoda, Asami; Koshida, Haruka; Sakuta, Keita; Takata, Tadanori; Koshida, Kichiro; Iida, Hiroji; Matsui, Osamu

2012-03-08

Recently, specific computed tomography (CT) scanners have been equipped with organ-based tube current modulation (TCM) technology. It is possible that organ-based TCM will replace the conventional dose-reduction technique of reducing the effective milliampere-second. The aim of this study was to determine if organ-based TCM could reduce radiation exposure to the breasts without compromising the image uniformity and beam hardening effect in thoracic CT examinations. Breast and skin radiation doses and the absorbed radiation dose distribution within a single section were measured with an anthropomorphic phantom and radiophotoluminescent glass dosimeters using four approaches to thoracic CT (reference, organ-based TCM, copper shielding, and the combination of the above two techniques, hereafter referred to as the combination technique). The CT value and noise level were measured using the same calibration phantom. Organ-based TCM and copper shielding reduced radiation doses to the breast by 23.7% and 21.8%, respectively. However, the CT value increased, especially in the anterior region, using copper shielding. In contrast, the CT value and noise level barely increased using organ-based TCM. The combination technique reduced the radiation dose to the breast by 38.2%, but greatly increased the absorbed radiation dose from the central to the posterior regions. Moreover, the CT value increased in the anterior region and the noise level increased by more than 10% in the entire region. Therefore, organ-based TCM can reduce radiation doses to breasts with only small increases in noise levels, making it preferable for specific groups of patients, such as children and young women.

Dosimetry in small-animal CT using Monte Carlo simulations

NASA Astrophysics Data System (ADS)

Lee, C.-L.; Park, S.-J.; Jeon, P.-H.; Jo, B.-D.; Kim, H.-J.

2016-01-01

Small-animal computed tomography (micro-CT) imaging devices are increasingly being used in biological research. While investigators are mainly interested in high-contrast, low-noise, and high-resolution anatomical images, relatively large radiation doses are required, and there is also growing concern over the radiological risk from preclinical experiments. This study was conducted to determine the radiation dose in a mouse model for dosimetric estimates using the GEANT4 application for tomographic emission simulations (GATE) and to extend its techniques to various small-animal CT applications. Radiation dose simulations were performed with the same parameters as those for the measured micro-CT data, using the MOBY phantom, a pencil ion chamber and an electrometer with a CT detector. For physical validation of radiation dose, absorbed dose of brain and liver in mouse were evaluated to compare simulated results with physically measured data using thermoluminescent dosimeters (TLDs). The mean difference between simulated and measured data was less than 2.9% at 50 kVp X-ray source. The absorbed doses of 37 brain tissues and major organs of the mouse were evaluated according to kVp changes. The absorbed dose over all of the measurements in the brain (37 types of tissues) consistently increased and ranged from 42.4 to 104.0 mGy. Among the brain tissues, the absorbed dose of the hypothalamus (157.8-414.30 mGy) was the highest for the beams at 50-80 kVp, and that of the corpus callosum (11.2-26.6 mGy) was the lowest. These results can be used as a dosimetric database to control mouse doses and preclinical targeted radiotherapy experiments. In addition, to accurately calculate the mouse-absorbed dose, the X-ray spectrum, detector alignment, and uncertainty in the elemental composition of the simulated materials must be accurately modeled.

Absorbed doses of lungs from radon retained in airway lumens of mice and rats.

PubMed

Sakoda, Akihiro; Ishimori, Yuu; Yamaoka, Kiyonori; Kataoka, Takahiro; Mitsunobu, Fumihiro

2013-08-01

This paper provides absorbed doses arising from radon gas in air retained in lung airway lumens. Because radon gas exposure experiments often use small animals, the calculation was performed for mice and rats. For reference, the corresponding computations were also done for humans. Assuming that radon concentration in airway lumens is the same as that in the environment, its progeny's production in and clearance from airways were simulated. Absorbed dose rates were obtained for three lung regions and the whole lung, considering that secretory and basal cells are sensitive to radiation. The results showed that absorbed dose rates for all lung regions and whole lung generally increase from mice to rats to humans. For example, the dose rates for the whole lung were 25.4 in mice, 41.7 in rats, and 59.9 pGy (Bq m⁻³)⁻¹ h⁻¹ in humans. Furthermore, these values were also compared with lung dose rates from two other types of exposures, that is, due to inhalation of radon or its progeny, which were already reported. It was confirmed that the direct inhalation of radon progeny in the natural environment, which is known as a cause of lung cancer, results in the highest dose rates for all species. Based on the present calculations, absorbed dose rates of the whole lung from radon gas were lower by a factor of about 550 (mice), 200 (rats), or 70 (humans) than those from radon progeny inhalation. The calculated dose rate values are comparatively small. Nevertheless, the present study is considered to contribute to our understanding of doses from inhalation of radon and its progeny.

Comparison of estimated human dose of (68)Ga-MAA with (99m)Tc-MAA based on rat data.

PubMed

Shanehsazzadeh, Saeed; Lahooti, Afsaneh; Yousefnia, Hassan; Geramifar, Parham; Jalilian, Amir Reza

2015-10-01

(99m)Tc macroaggregated albumin ((99m)Tc-MAA) that had been used as a perfusion agent has been evaluated. In this study, we tried to estimate human absorbed dose of ⁶⁸Ga-MAA via commercially available kit from Pars-Isotopes, based on biodistribution data in wild-type rats, and compare our estimation with the available absorbed dose data from (99m)Tc-MAA. For biodistribution of ⁶⁸Ga-MAA, three rats were sacrificed at each selected times after injection (15, 30, 45, 60, and 120 min) and the percentage of injected dose per gram of each organ was measured by direct counting from rats data from 11 harvested organs. The medical internal radiation dose formulation was applied to extrapolate from rats to human and to project the absorbed radiation dose for various organs in humans. The biodistribution data for ⁶⁸Ga-MAA showed that the most of the activity was taken up by the lung (more than 97 %) in no time. Our dose prediction shows that a 185-MBq injection of ⁶⁸Ga-MAA into humans might result in an estimated absorbed dose of 4.31 mGy in the whole body. The highest absorbed doses are observed in the adrenals, spleen, pancreas, and red marrow with 0.36, 0.34, 0.26, and 0.19 mGy, respectively. Since the (99m)Tc-MAA remains longer than ⁶⁸Ga-MAA in the lung and ⁶⁸Ga-MAA has good image qualities and results in lower amounts of dose delivery to the critical organs such as gonads, red marrow, and adrenals, the use of ⁶⁸Ga-MAA is recommended.

Calculation of Blood Dose in Patients Treated With 131I Using MIRD, Imaging, and Blood Sampling Methods

PubMed Central

Piruzan, Elham; Haghighatafshar, Mahdi; Faghihi, Reza; Entezarmahdi, Seyed Mohammad

2016-01-01

Abstract Radioiodine therapy is known as the most effective treatment of differentiated thyroid carcinoma (DTC) to ablate remnant thyroid tissue after surgery. In patients with DTC treated with radioiodine, internal radiation dosimetry of radioiodine is useful for radiation risk assessment. The aim of this study is to describe a method to estimate the absorbed dose to the blood using medical internal radiation dosimetry methods. In this study, 23 patients with DTC with different administrated activities, 3.7, 4.62, and 5.55 GBq after thyroidectomy, were randomly selected. Blood dosimetry of treated patients was performed with external whole body counting using a dual-head gamma camera imaging device and also with blood sample activity measurements using a dose calibrator. Absorbed dose to the blood was measured at 2, 6, 12, 24, 48, and 96 hours after the administration of radioiodine with the 2 methods. Based on the results of whole body counting and blood sample activity dose rate measurements, 96 hours after administration of 3.7, 4.62, and 5.55 GBq of radioiodine, absorbed doses to patients’ blood were 0.65 ± 0.20, 0.67 ± 0.18, 0.79 ± 0.51 Gy, respectively. Increasing radioiodine activity from 3.7 to 5.55 GBq increased blood dose significantly, while there was no significant difference in blood dose between radioiodine dosages of 3.7 and 4.62 GBq. Our results revealed a significant correlation between the blood absorbed dose and blood sample activity and between the blood absorbed dose and whole body counts 24 to 48 hours after the administration of radioiodine. PMID:26986171

Calculation of Blood Dose in Patients Treated With 131I Using MIRD, Imaging, and Blood Sampling Methods.

PubMed

Piruzan, Elham; Haghighatafshar, Mahdi; Faghihi, Reza; Entezarmahdi, Seyed Mohammad

2016-03-01

Radioiodine therapy is known as the most effective treatment of differentiated thyroid carcinoma (DTC) to ablate remnant thyroid tissue after surgery. In patients with DTC treated with radioiodine, internal radiation dosimetry of radioiodine is useful for radiation risk assessment. The aim of this study is to describe a method to estimate the absorbed dose to the blood using medical internal radiation dosimetry methods. In this study, 23 patients with DTC with different administrated activities, 3.7, 4.62, and 5.55 GBq after thyroidectomy, were randomly selected. Blood dosimetry of treated patients was performed with external whole body counting using a dual-head gamma camera imaging device and also with blood sample activity measurements using a dose calibrator. Absorbed dose to the blood was measured at 2, 6, 12, 24, 48, and 96 hours after the administration of radioiodine with the 2 methods. Based on the results of whole body counting and blood sample activity dose rate measurements, 96 hours after administration of 3.7, 4.62, and 5.55 GBq of radioiodine, absorbed doses to patients' blood were 0.65 ± 0.20, 0.67 ± 0.18, 0.79 ± 0.51 Gy, respectively. Increasing radioiodine activity from 3.7 to 5.55 GBq increased blood dose significantly, while there was no significant difference in blood dose between radioiodine dosages of 3.7 and 4.62 GBq. Our results revealed a significant correlation between the blood absorbed dose and blood sample activity and between the blood absorbed dose and whole body counts 24 to 48 hours after the administration of radioiodine.

A study on the application of Fourier series in IMRT treatment planning.

PubMed

Almeida-Trinidad, R; Garnica-Garza, H M

2007-12-01

In intensity-modulated radiotherapy, a set of x-ray fluence profiles is iteratively adjusted until a desired absorbed dose distribution is obtained. The purpose of this article is to present a method that allows the optimization of fluence profiles based on the Fourier series decomposition of an initial approximation to the profile. The method has the advantage that a new fluence profile can be obtained in a precise and controlled way with the tuning of only two parameters, namely the phase of the sine and cosine terms of one of the Fourier components, in contrast to the point-by-point tuning of the profile. Also, because the method uses analytical functions, the resultant profiles do not exhibit numerical artifacts. A test case consisting of a mathematical phantom with a target wrapped around a critical structure is discussed to illustrate the algorithm. It is shown that the degree of conformality of the absorbed dose distribution can be tailored by varying the number of Fourier terms made available to the optimization algorithm. For the test case discussed here, it is shown that the number of Fourier terms to be modified depends on the number of radiation beams incident on the target but it is in general in the order of 10 terms.

Absorbed dose measurement in low temperature samples:. comparative methods using simulated material

NASA Astrophysics Data System (ADS)

Garcia, Ruth; Harris, Anthony; Winters, Martell; Howard, Betty; Mellor, Paul; Patil, Deepak; Meiner, Jason

2004-09-01

There is a growing need to reliably measure absorbed dose in low temperature samples, especially in the pharmaceutical and tissue banking industries. All dosimetry systems commonly used in the irradiation industry are temperature sensitive. Radiation of low temperature samples, such as those packaged with dry ice, must therefore take these dosimeter temperature effects into consideration. This paper will suggest a method to accurately deliver an absorbed radiation dose using dosimetry techniques designed to abrogate the skewing effects of low temperature environments on existing dosimetry systems.

Study on the quality assurance of diagnostic X-ray machines and assessment of the absorbed dose to patients

NASA Astrophysics Data System (ADS)

Hassan, G. M.; Rabie, N.; Mustafa, K. A.; Abdel-Khalik, S. S.

2012-09-01

Radiation exposure and image quality in X-ray diagnostic radiology provide a clear understanding of the relationship between the radiation dose delivered to a patient and image quality in optimizing medical diagnostic radiology. Because a certain amount of radiation is unavoidably delivered to patients, this should be as low as reasonably achievable. Several X-ray diagnostic machines were used at different medical diagnostic centers in Egypt for studying the beam quality and the dose delivered to the patient. This article studies the factors affecting the beam quality, such as the kilo-volt peak (kVp), exposure time (mSc), tube current (mAs) and the absorbed dose in (μGy) for different examinations. The maximum absorbed dose measured per mAs was 594±239 and 12.5±3.7 μGy for the abdomen and the chest, respectively, while the absorbed dose at the elbow was 18±6 μGy, which was the minimum dose recorded. The compound and expanded uncertainties accompanying these measurements were 4±0.35% and 8±0.7%, respectively. The measurements were done through quality control tests as acceptance procedures.

Topical Review: Polymer gel dosimetry

PubMed Central

Baldock, C; De Deene, Y; Doran, S; Ibbott, G; Jirasek, A; Lepage, M; McAuley, K B; Oldham, M; Schreiner, L J

2010-01-01

Polymer gel dosimeters are fabricated from radiation sensitive chemicals which, upon irradiation, polymerize as a function of the absorbed radiation dose. These gel dosimeters, with the capacity to uniquely record the radiation dose distribution in three-dimensions (3D), have specific advantages when compared to one-dimensional dosimeters, such as ion chambers, and two-dimensional dosimeters, such as film. These advantages are particularly significant in dosimetry situations where steep dose gradients exist such as in intensity-modulated radiation therapy (IMRT) and stereotactic radiosurgery. Polymer gel dosimeters also have specific advantages for brachytherapy dosimetry. Potential dosimetry applications include those for low-energy x-rays, high-linear energy transfer (LET) and proton therapy, radionuclide and boron capture neutron therapy dosimetries. These 3D dosimeters are radiologically soft-tissue equivalent with properties that may be modified depending on the application. The 3D radiation dose distribution in polymer gel dosimeters may be imaged using magnetic resonance imaging (MRI), optical-computerized tomography (optical-CT), x-ray CT or ultrasound. The fundamental science underpinning polymer gel dosimetry is reviewed along with the various evaluation techniques. Clinical dosimetry applications of polymer gel dosimetry are also presented. PMID:20150687

Relative Importance of Hip and Sacral Pain Among Long-Term Gynecological Cancer Survivors Treated With Pelvic Radiotherapy and Their Relationships to Mean Absorbed Doses

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

Waldenstroem, Ann-Charlotte, E-mail: ann-charlotte.waldenstrom@oncology.gu.se; Department of Oncology, Sahlgrenska University Hospital, Gothenburg; Olsson, Caroline

Purpose: To investigate the relative importance of patient-reported hip and sacral pain after pelvic radiotherapy (RT) for gynecological cancer and its relationship to the absorbed doses in these organs. Methods and Materials: We used data from a population-based study that included 650 long-term gynecological cancer survivors treated with pelvic RT in the Gothenburg and Stockholm areas in Sweden with a median follow-up of 6 years (range, 2-15) and 344 population controls. Symptoms were assessed through a study-specific postal questionnaire. We also analyzed the hip and sacral dose-volume histogram data for 358 of the survivors. Results: Of the survivors, one inmore » three reported having or having had hip pain after completing RT. Daily pain when walking was four times as common among the survivors compared to controls. Symptoms increased in frequency with a mean absorbed dose >37.5 Gy. Also, two in five survivors reported pain in the sacrum. Sacral pain also affected their walking ability and tended to increase with a mean absorbed dose >42.5 Gy. Conclusions: Long-term survivors of gynecological cancer treated with pelvic RT experience hip and sacral pain when walking. The mean absorbed dose was significantly related to hip pain and was borderline significantly related to sacral pain. Keeping the total mean absorbed hip dose below 37.5 Gy during treatment might lower the occurrence of long-lasting pain. In relation to the controls, the survivors had a lower occurrence of pain and pain-related symptoms from the hips and sacrum compared with what has previously been reported for the pubic bone.« 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

Absorbed Dose and Dose Equivalent Calculations for Modeling Effective Dose

NASA Technical Reports Server (NTRS)

Welton, Andrew; Lee, Kerry

2010-01-01

While in orbit, Astronauts are exposed to a much higher dose of ionizing radiation than when on the ground. It is important to model how shielding designs on spacecraft reduce radiation effective dose pre-flight, and determine whether or not a danger to humans is presented. However, in order to calculate effective dose, dose equivalent calculations are needed. Dose equivalent takes into account an absorbed dose of radiation and the biological effectiveness of ionizing radiation. This is important in preventing long-term, stochastic radiation effects in humans spending time in space. Monte carlo simulations run with the particle transport code FLUKA, give absorbed and equivalent dose data for relevant shielding. The shielding geometry used in the dose calculations is a layered slab design, consisting of aluminum, polyethylene, and water. Water is used to simulate the soft tissues that compose the human body. The results obtained will provide information on how the shielding performs with many thicknesses of each material in the slab. This allows them to be directly applicable to modern spacecraft shielding geometries.

Degradation mechanism of polysaccharides on irradiated sugarcane bagasse

NASA Astrophysics Data System (ADS)

Ribeiro, M. A.; Oikawa, H.; Mori, M. N.; Napolitano, C. M.; Duarte, C. L.

2013-03-01

Sugarcane bagasse is composed of cellulose, hemicelluloses, lignin, and a minor amount of protein and inorganic materials. Cellulose consists of linear macromolecular chains of glucose, linked by β-1,4-glucosidic bonds between the number one and the number four carbon atoms of the adjacent glucose units. Hemicelluloses are heterogeneous polymers, unlike cellulose, and are usually composed of 50-200 monomer units of pentose such as xylose and arabinose. Lignin is a complex polymer of p-hydroxyphenylpropanoid units connected by CC and COC links. Radiation-induced reactions in the macromolecules of the cellulose materials are known to be initiated through fast distribution of the absorbed energy within the molecules to produce long- and short-lived radicals. The present study was carried out using sugarcane bagasse samples irradiated by a Radiation Dynamics electron beam accelerator with 1.5 MeV and 37 kW, with the objective to evaluate the cleavage of the polysaccharides and the by-products formed as a result of the absorbed dose. The electron beam processing in 30 kGy of absorbed dose changed the sugarcane bagasse structure and composition, causing some cellulose and hemicelluloses cleavage. These cleavages were partial, forming oligosaccharides and liberating the sugars glucose and arabinose. The main by-product was acetic acid, originated from the de-acetylating of hemicelluloses.

Space Radiation Peculiarities in the Extra Vehicular Environment of the International Space Station (ISS)

NASA Astrophysics Data System (ADS)

Dachev, Tsvetan; Bankov, Nikolay; Tomov, Borislav; Matviichuk, Yury; Dimitrov, Plamen

2013-12-01

The space weather and the connected with it ionizing radiation were recognized as a one of the main health concern to the International Space Station (ISS) crew. Estimation the effects of radiation on humans in ISS requires at first order accurate knowledge of the accumulated by them absorbed dose rates, which depend of the global space radiation distribution and the local variations generated by the 3D surrounding shielding distribution. The R3DE (Radiation Risks Radiometer-Dosimeter (R3D) for the EXPOSE-E platform on the European Technological Exposure Facility (EuTEF) worked successfully outside of the European Columbus module between February 2008 and September 2009. Very similar instrument named R3DR for the EXPOSE-R platform worked outside Russian Zvezda module of ISS between March 2009 and August 2010. Both are Liulin type, Bulgarian build miniature spectrometers-dosimeters. They accumulated about 5 million measurements of the flux and absorbed dose rate with 10 seconds resolution behind less than 0.41 g cm-2 shielding, which is very similar to the Russian and American space suits [1-3] average shielding. That is why all obtained data can be interpreted as possible doses during Extra Vehicular Activities (EVA) of the cosmonauts and astronauts. The paper first analyses the obtained long-term results in the different radiation environments of: Galactic Cosmic Rays (GCR), inner radiation belt trapped protons in the region of the South Atlantic Anomaly (SAA) and outer radiation belt (ORB) relativistic electrons. The large data base was used for development of an empirical model for calculation of the absorbed dose rates in the extra vehicular environment of ISS at 359 km altitude. The model approximate the averaged in a grid empirical dose rate values to predict the values at required from the user geographical point, station orbit or area in geographic coordinate system. Further in the paper it is presented an intercomparison between predicted by the model dose rate values and data collected by the R3DE/R instruments and NASA Tissue Equivalent Proportional Counter (TEPC) during real cosmonauts and astronauts EVA in 79 the 2008-2010 time interval including large relativistic electrons doses during the magnetosphere enhancement in April 2010. The model was also used to be predicted the accumulated along the orbit of ISS galactic cosmic rays and inner radiation belt dose for 1 orbit (1.5 hours) and 4 consequences orbits (6 hours), which is the usual EVA continuation in dependence by the longitude of the ascending node of ISS. These predictions of the model could be used by space agencies medical and other not specialized in the radiobiology support staff for first approach in the ISS EVA time and space planning.

Radiation levels and image quality in patients undergoing chest X-ray examinations

NASA Astrophysics Data System (ADS)

de Oliveira, Paulo Márcio Campos; do Carmo Santana, Priscila; de Sousa Lacerda, Marco Aurélio; da Silva, Teógenes Augusto

2017-11-01

Patient dose monitoring for different radiographic procedures has been used as a parameter to evaluate the performance of radiology services; skin entrance absorbed dose values for each type of examination were internationally established and recommended aiming patient protection. In this work, a methodology for dose evaluation was applied to three diagnostic services: one with a conventional film and two with digital computerized radiography processing techniques. The x-ray beam parameters were selected and "doses" (specifically the entrance surface and incident air kerma) were evaluated based on images approved in European criteria during postero-anterior (PA) and lateral (LAT) incidences. Data were collected from 200 patients related to 200 PA and 100 LAT incidences. Results showed that doses distributions in the three diagnostic services were very different; the best relation between dose and image quality was found in the institution with the chemical film processing. This work contributed for disseminating the radiation protection culture by emphasizing the need of a continuous dose reduction without losing the quality of the diagnostic image.

MIRD Pamphlet No. 21: A Generalized Schema for Radiopharmaceutical Dosimetry-Standardization of Nomenclature

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

Bolch, W E; Eckerman, Keith F; Sgouros, George

2009-03-01

The internal dosimetry schema of the Medical Internal Radiation Dose (MIRD) Committee of the Society of Nuclear Medicine has provided a broad framework for assessment of the absorbed dose to whole organs, tissue subregions, voxelized tissue structures, and individual cellular compartments for use in both diagnostic and therapeutic nuclear medicine. The schema was originally published in 1968, revised in 1976, and republished in didactic form with comprehensive examples as the MIRD primer in 1988 and 1991. The International Commission on Radiological Protection (ICRP) is an organization that also supplies dosimetric models and technical data, for use in providing recommendations formore » limits on ionizing radiation exposure to workers and members of the general public. The ICRP has developed a dosimetry schema similar to that of the MIRD Committee but has used different terminology and symbols for fundamental quantities such as the absorbed fraction, specific absorbed fraction, and various dose coefficients. The MIRD Committee objectives for this pamphlet are 3-fold: to restate its schema for assessment of absorbed dose in a manner consistent with the needs of both the nuclear medicine and the radiation protection communities, with the goal of standardizing nomenclature; to formally adopt the dosimetry quantities equivalent dose and effective dose for use in comparative evaluations of potential risks of radiation-induced stochastic effects to patients after nuclear medicine procedures; and to discuss the need to identify dosimetry quantities based on absorbed dose that address deterministic effects relevant to targeted radionuclide therapy.« less

Model-Based Radiation Dose Correction for Yttrium-90 Microsphere Treatment of Liver Tumors With Central Necrosis

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

Liu, Ching-Sheng; Department of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; Lin, Ko-Han

Purpose: The objectives of this study were to model and calculate the absorbed fraction {phi} of energy emitted from yttrium-90 ({sup 90}Y) microsphere treatment of necrotic liver tumors. Methods and Materials: The tumor necrosis model was proposed for the calculation of {phi} over the spherical shell region. Two approaches, the semianalytic method and the probabilistic method, were adopted. In the former method, the range--energy relationship and the sampling of electron paths were applied to calculate the energy deposition within the target region, using the straight-ahead and continuous-slowing-down approximation (CSDA) method. In the latter method, the Monte Carlo PENELOPE code wasmore » used to verify results from the first method. Results: The fraction of energy, {phi}, absorbed from {sup 90}Y by 1-cm thickness of tumor shell from microsphere distribution by CSDA with complete beta spectrum was 0.832 {+-} 0.001 and 0.833 {+-} 0.001 for smaller (r{sub T} = 5 cm) and larger (r{sub T} = 10 cm) tumors (where r is the radii of the tumor [T] and necrosis [N]). The fraction absorbed depended mainly on the thickness of the tumor necrosis configuration, rather than on tumor necrosis size. The maximal absorbed fraction {phi} that occurred in tumors without central necrosis for each size of tumor was different: 0.950 {+-} 0.000, and 0.975 {+-} 0.000 for smaller (r{sub T} = 5 cm) and larger (r{sub T} = 10 cm) tumors, respectively (p < 0.0001). Conclusions: The tumor necrosis model was developed for dose calculation of {sup 90}Y microsphere treatment of hepatic tumors with central necrosis. With this model, important information is provided regarding the absorbed fraction applicable to clinical {sup 90}Y microsphere treatment.« less

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.

Graves' disease radioiodine-therapy: Choosing target absorbed doses for therapy planning

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

Willegaignon, J., E-mail: j.willegaignon@gmail.com; Sapienza, M. T.; Coura-Filho, G. B.

Purpose: The precise determination of organ mass (m{sub th}) and total number of disintegrations within the thyroid gland (A{sup ~}) are essential for thyroid absorbed-dose calculations for radioiodine therapy. Nevertheless, these parameters may vary according to the method employed for their estimation, thus introducing uncertainty in the estimated thyroid absorbed dose and in any dose–response relationship derived using such estimates. In consideration of these points, thyroid absorbed doses for Graves’ disease (GD) treatment planning were calculated using different approaches to estimating the m{sub th} and the A{sup ~}. Methods: Fifty patients were included in the study. Thyroid{sup 131}I uptake measurementsmore » were performed at 2, 6, 24, 48, 96, and 220 h postadministration of a tracer activity in order to estimate the effective half-time (T{sub eff}) of {sup 131}I in the thyroid; the thyroid cumulated activity was then estimated using the T{sub eff} thus determined or, alternatively, calculated by numeric integration of the measured time-activity data. Thyroid mass was estimated by ultrasonography (USG) and scintigraphy (SCTG). Absorbed doses were calculated with the OLINDA/EXM software. The relationships between thyroid absorbed dose and therapy response were evaluated at 3 months and 1 year after therapy. Results: The average ratio (±1 standard deviation) betweenm{sub th} estimated by SCTG and USG was 1.74 (±0.64) and that between A{sup ~} obtained by T{sub eff} and the integration of measured activity in the gland was 1.71 (±0.14). These differences affect the calculated absorbed dose. Overall, therapeutic success, corresponding to induction of durable hypothyroidism or euthyroidism, was achieved in 72% of all patients at 3 months and in 90% at 1 year. A therapeutic success rate of at least 95% was found in the group of patients receiving doses of 200 Gy (p = 0.0483) and 330 Gy (p = 0.0131) when m{sub th} was measured by either USG or SCTG and A{sup ~} was determined by the integration of measured {sup 131}I activity in the thyroid gland and based on T{sub eff}, respectively. No statistically significant relationship was found between therapeutic response and patients’ age, administered {sup 131}I activity (MBq), 24-h thyroid {sup 131}I uptake (%) or T{sub eff} (p ≥ 0.064); nonetheless, a good relationship was found between the therapeutic response and m{sub th} (p ≤ 0.035). Conclusions: According to the results of this study, the most effective thyroid absorbed dose to be targeted in GD therapy should not be based on a fixed dose but rather should be individualized based on the patient'sm{sub th} and A{sup ~}. To achieve a therapeutic success (i.e., durable euthyroidism or hypothyroidism) rate of at least 95%, a thyroid absorbed dose of 200 or 330 Gy is required depending on the methodology used for estimating m{sub th} and A{sup ~}.« less

Graves' disease radioiodine-therapy: Choosing target absorbed doses for therapy planning

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

Willegaignon, J., E-mail: j.willegaignon@gmail.com; Sapienza, M. T.; Coura-Filho, G. B.

2014-01-15

Purpose: The precise determination of organ mass (m{sub th}) and total number of disintegrations within the thyroid gland (A{sup ~}) are essential for thyroid absorbed-dose calculations for radioiodine therapy. Nevertheless, these parameters may vary according to the method employed for their estimation, thus introducing uncertainty in the estimated thyroid absorbed dose and in any dose–response relationship derived using such estimates. In consideration of these points, thyroid absorbed doses for Graves’ disease (GD) treatment planning were calculated using different approaches to estimating the m{sub th} and the A{sup ~}. Methods: Fifty patients were included in the study. Thyroid{sup 131}I uptake measurementsmore » were performed at 2, 6, 24, 48, 96, and 220 h postadministration of a tracer activity in order to estimate the effective half-time (T{sub eff}) of {sup 131}I in the thyroid; the thyroid cumulated activity was then estimated using the T{sub eff} thus determined or, alternatively, calculated by numeric integration of the measured time-activity data. Thyroid mass was estimated by ultrasonography (USG) and scintigraphy (SCTG). Absorbed doses were calculated with the OLINDA/EXM software. The relationships between thyroid absorbed dose and therapy response were evaluated at 3 months and 1 year after therapy. Results: The average ratio (±1 standard deviation) betweenm{sub th} estimated by SCTG and USG was 1.74 (±0.64) and that between A{sup ~} obtained by T{sub eff} and the integration of measured activity in the gland was 1.71 (±0.14). These differences affect the calculated absorbed dose. Overall, therapeutic success, corresponding to induction of durable hypothyroidism or euthyroidism, was achieved in 72% of all patients at 3 months and in 90% at 1 year. A therapeutic success rate of at least 95% was found in the group of patients receiving doses of 200 Gy (p = 0.0483) and 330 Gy (p = 0.0131) when m{sub th} was measured by either USG or SCTG and A{sup ~} was determined by the integration of measured {sup 131}I activity in the thyroid gland and based on T{sub eff}, respectively. No statistically significant relationship was found between therapeutic response and patients’ age, administered {sup 131}I activity (MBq), 24-h thyroid {sup 131}I uptake (%) or T{sub eff} (p ≥ 0.064); nonetheless, a good relationship was found between the therapeutic response and m{sub th} (p ≤ 0.035). Conclusions: According to the results of this study, the most effective thyroid absorbed dose to be targeted in GD therapy should not be based on a fixed dose but rather should be individualized based on the patient'sm{sub th} and A{sup ~}. To achieve a therapeutic success (i.e., durable euthyroidism or hypothyroidism) rate of at least 95%, a thyroid absorbed dose of 200 or 330 Gy is required depending on the methodology used for estimating m{sub th} and A{sup ~}.« less

Ionization chamber-based reference dosimetry of intensity modulated radiation beams.

PubMed

Bouchard, Hugo; Seuntjens, Jan

2004-09-01

The present paper addresses reference dose measurements using thimble ionization chambers for quality assurance in IMRT fields. In these radiation fields, detector fluence perturbation effects invalidate the application of open-field dosimetry protocol data for the derivation of absorbed dose to water from ionization chamber measurements. We define a correction factor C(Q)IMRT to correct the absorbed dose to water calibration coefficient N(D, w)Q for fluence perturbation effects in individual segments of an IMRT delivery and developed a calculation method to evaluate the factor. The method consists of precalculating, using accurate Monte Carlo techniques, ionization chamber, type-dependent cavity air dose, and in-phantom dose to water at the reference point for zero-width pencil beams as a function of position of the pencil beams impinging on the phantom surface. These precalculated kernels are convolved with the IMRT fluence distribution to arrive at the dose-to-water-dose-to-cavity air ratio [D(a)w (IMRT)] for IMRT fields and with a 10x10 cm2 open-field fluence to arrive at the same ratio D(a)w (Q) for the 10x10 cm2 reference field. The correction factor C(Q)IMRT is then calculated as the ratio of D(a)w (IMRT) and D(a)w (Q). The calculation method was experimentally validated and the magnitude of chamber correction factors in reference dose measurements in single static and dynamic IMRT fields was studied. The results show that, for thimble-type ionization chambers the correction factor in a single, realistic dynamic IMRT field can be of the order of 10% or more. We therefore propose that for accurate reference dosimetry of complete n-beam IMRT deliveries, ionization chamber fluence perturbation correction factors must explicitly be taken into account.

Diamond detector in absorbed dose measurements in high‐energy linear accelerator photon and electron beams

PubMed Central

Binukumar, John Pichy; Amri, Iqbal Al; Davis, Cheriyathmanjiyil Antony

2016-01-01

Diamond detectors (DD) are preferred in small field dosimetry of radiation beams because of small dose profile penumbras, better spatial resolution, and tissue‐equivalent properties. We investigated a commercially available ‘microdiamond’ detector in realizing absorbed dose from first principles. A microdiamond detector, type TM 60019 with tandem electrometer is used to measure absorbed doses in water, nylon, and PMMA phantoms. With sensitive volume 0.004 mm3, radius 1.1 mm, thickness 1×10−3mm, the nominal response is 1 nC/Gy. It is assumed that the diamond detector could collect total electric charge (nC) developed during irradiation at 0 V bias. We found that dose rate effect is less than 0.7% for changing dose rate by 500 MU/min. The reproducibility in obtaining readings with diamond detector is found to be ±0.17% (1 SD) (n=11). The measured absorbed doses for 6 MV and 15 MV photons arrived at using mass energy absorption coefficients and stopping power ratios compared well with Nd, water calibrated ion chamber measured absorbed doses within 3% in water, PMMA, and nylon media. The calibration factor obtained for diamond detector confirmed response variation is due to sensitivity due to difference in manufacturing process. For electron beams, we had to apply ratio of electron densities of water to carbon. Our results qualify diamond dosimeter as a transfer standard, based on long‐term stability and reproducibility. Based on micro‐dimensions, we recommend these detectors for pretreatment dose verifications in small field irradiations like stereotactic treatments with image guidance. PACS number(s): 87.56.Da PMID:27074452

Low dose reconstruction algorithm for differential phase contrast imaging.

PubMed

Wang, Zhentian; Huang, Zhifeng; Zhang, Li; Chen, Zhiqiang; Kang, Kejun; Yin, Hongxia; Wang, Zhenchang; Marco, Stampanoni

2011-01-01

Differential phase contrast imaging computed tomography (DPCI-CT) is a novel x-ray inspection method to reconstruct the distribution of refraction index rather than the attenuation coefficient in weakly absorbing samples. In this paper, we propose an iterative reconstruction algorithm for DPCI-CT which benefits from the new compressed sensing theory. We first realize a differential algebraic reconstruction technique (DART) by discretizing the projection process of the differential phase contrast imaging into a linear partial derivative matrix. In this way the compressed sensing reconstruction problem of DPCI reconstruction can be transformed to a resolved problem in the transmission imaging CT. Our algorithm has the potential to reconstruct the refraction index distribution of the sample from highly undersampled projection data. Thus it can significantly reduce the dose and inspection time. The proposed algorithm has been validated by numerical simulations and actual experiments.

Nickel absorption and kinetics in human volunteers.

PubMed

Sunderman, F W; Hopfer, S M; Sweeney, K R; Marcus, A H; Most, B M; Creason, J

1989-05-01

Mathematical modeling of the kinetics of nickel absorption, distribution, and elimination was performed in healthy human volunteers who ingested NiSO4 drinking water (Experiment 1) or added to food (Experiment 2). Nickel was analyzed by electrothermal atomic absorption spectrophotometry in serum, urine, and feces collected during 2 days before and 4 days after a specified NiSO4 dose (12 micrograms of nickel/kg, n = 4; 18 micrograms of nickel/kg, n = 4; or 50 micrograms of nickel/kg, n = 1). In Experiment 1, each of the subjects fasted 12 hr before and 3 hr after drinking one of the specified NiSO4 doses dissolved in water; in Experiment 2, the respective subjects fasted 12 hr before consuming a standard American breakfast that contained the identical dose of NiSO4 added to scrambled eggs. Kinetic analyses, using a compartmental model, provided excellent goodness-of-fit for paired data sets from all subjects. Absorbed nickel averaged 27 +/- 17% (mean +/- SD) of the dose ingested in water vs 0.7 +/- 0.4% of the same dose ingested in food (a 40-fold difference); rate constants for nickel absorption, transfer, and elimination were not significantly influenced by the oral vehicle. The elimination half-time for absorbed nickel averaged 28 +/- 9 hr. Renal clearance of nickel averaged 8.3 +/- 2.0 ml/min/1.73 m2 in Experiment 1 and 5.8 +/- 4.3 ml/min/1.73 m2 in Experiment 2. This study confirms that dietary constituents profoundly reduce the bioavailability of Ni2+ for alimentary absorption; approximately one-quarter of nickel ingested in drinking water after an over-night fast is absorbed from the human intestine and excreted in urine, compared with only 1% of nickel ingested in food. The compartmental model and kinetic parameters provided by this study will reduce the uncertainty of toxicologic risk assessments of human exposures to nickel in drinking water and food.

Radiation exposure and risk assessment for critical female body organs

NASA Technical Reports Server (NTRS)

Atwell, William; Weyland, Mark D.; Hardy, Alva C.

1991-01-01

Space radiation exposure limits for astronauts are based on recommendations of the National Council on Radiation Protection and Measurements. These limits now include the age at exposure and sex of the astronaut. A recently-developed computerized anatomical female (CAF) model is discussed in detail. Computer-generated, cross-sectional data are presented to illustrate the completeness of the CAF model. By applying ray-tracing techniques, shield distribution functions have been computed to calculate absorbed dose and dose equivalent values for a variety of critical body organs (e.g., breasts, lungs, thyroid gland, etc.) and mission scenarios. Specific risk assessments, i.e., cancer induction and mortality, are reviewed.

Radioactivity of peat mud used in therapy.

PubMed

Karpińska, Maria; Mnich, Krystian; Kapała, Jacek; Bielawska, Agnieszka; Kulesza, Grzegorz; Mnich, Stanisław

2016-02-01

The aim of the study was to determine the contents of natural and artificial isotopes in peat mud and to estimate the radiation dose absorbed via skin in patients during standard peat mud treatment. The analysis included 37 samples collected from 8 spas in Poland. The measurements of isotope concentration activity were conducted with the use of gamma spectrometry methods. The skin dose in a standard peat mud bath therapy is approximately 300 nSv. The effective dose of such therapy is considered to be 22 nSv. The doses absorbed during peat mud therapy are 5 orders of magnitude lower than effective annual dose absorbed from the natural radiation background by a statistical Pole (3.5 mSv). Neither therapeutic nor harmful effect is probable in case of such a small dose of ionising radiation. Copyright © 2015 Elsevier Ltd. All rights reserved.

In Vitro Dosimetry of Silver Nanoparticles

EPA Science Inventory

An important issue for interpreting in vitro nanomaterial testing is quantifying the dose absorbed by target cells. Considerations include the concentration added to the culture and the proportion of the applied dose that is absorbed by the target cells. Rapid and efficient techn...

Re-186 and Sm-153 dosimetry based on scintigraphic imaging data in skeletal metastasis palliative treatment and Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Andreou, M.; Lagopati, N.; Lyra, M.

2011-09-01

Optimum treatment planning of patients suffering from painful skeletal metastases requires accurate calculations concerning absorbed dose in metastatic lesions and critical organs, such as red marrow. Delivering high doses to tumor cells while limiting radiation dose to normal tissue, is the key for successful palliation treatment. The aim of this study is to compare the dosimetric calculations, obtained by Monte Carlo (MC) simulation and the MIRDOSE model, in therapeutic schemes of skeleton metastatic lesions, with Rhenium-186 (Sn) -HEDP and Samarium-153 -EDTMP. A bolus injection of 1295 MBq (35mCi) Re-186- HEDP was infused in 11 patients with multiple skeletal metastases. The administered dose for the 8 patients who received Sm-153 was 1 mCi /kg. Planar scintigraphic images for the two groups of patients were obtained, 24 h, 48 h and 72 h post injection, by an Elscint Apex SPX gamma camera. The images were processed, utilizing ROI quantitative methods, to determine residence times and radionuclide uptakes. Dosimetric calculations were performed using the patient specific scintigraphic data by the MIRDOSE3 code of MIRD. Also, MCNPX was employed, simulating the distribution of the radioisotope in the ROI and calculating the absorbed doses in the metastatic lesion, and in critical organs. Summarizing, there is a good agreement between the results, derived from the two pathways, the patient specific and the mathematical, with a deviation of less than 9% for planar scintigraphic data compared to MC, for both radiopharmaceuticals.

Radiation dose reduction efficiency of buildings after the accident at the Fukushima Daiichi Nuclear Power Station.

PubMed

Monzen, Satoru; Hosoda, Masahiro; Osanai, Minoru; Tokonami, Shinji

2014-01-01

Numerous radionuclides were released from the Fukushima Daiichi Nuclear Power Station (F1-NPS) in Japan following the magnitude 9.0 earthquake and tsunami on March 11, 2011. Local residents have been eager to calculate their individual radiation exposure. Thus, absorbed dose rates in the indoor and outdoor air at evacuation sites in the Fukushima Prefecture were measured using a gamma-ray measuring devices, and individual radiation exposure was calculated by assessing the radiation dose reduction efficiency (defined as the ratio of absorbed dose rate in the indoor air to the absorbed dose rate in the outdoor air) of wood, aluminum, and reinforced concrete buildings. Between March 2011 and July 2011, dose reduction efficiencies of wood, aluminum, and reinforced concrete buildings were 0.55 ± 0.04, 0.15 ± 0.02, and 0.19 ± 0.04, respectively. The reduction efficiency of wood structures was 1.4 times higher than that reported by the International Atomic Energy Agency. The efficiency of reinforced concrete was similar to previously reported values, whereas that of aluminum structures has not been previously reported. Dose reduction efficiency increased in proportion to the distance from F1-NPS at 8 of the 18 evacuation sites. Time variations did not reflect dose reduction efficiencies at evacuation sites although absorbed dose rates in the outdoor air decreased. These data suggest that dose reduction efficiency depends on structure types, levels of contamination, and evacuee behaviors at evacuation sites.

Estimation of whole-body radiation exposure from brachytherapy for oral cancer using a Monte Carlo simulation.

PubMed

Ozaki, Y; Watanabe, H; Kaida, A; Miura, M; Nakagawa, K; Toda, K; Yoshimura, R; Sumi, Y; Kurabayashi, T

2017-07-01

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. © The Author 2017. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Absolute x-ray dosimetry on a synchrotron medical beam line with a graphite calorimeter.

PubMed

Harty, P D; Lye, J E; Ramanathan, G; Butler, D J; Hall, C J; Stevenson, A W; Johnston, P N

2014-05-01

The absolute dose rate of the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter. The calorimetry results were compared to measurements from the existing free-air chamber, to provide a robust determination of the absolute dose in the synchrotron beam and provide confidence in the first implementation of a graphite calorimeter on a synchrotron medical beam line. The graphite calorimeter has a core which rises in temperature when irradiated by the beam. A collimated x-ray beam from the synchrotron with well-defined edges was used to partially irradiate the core. Two filtration sets were used, one corresponding to an average beam energy of about 80 keV, with dose rate about 50 Gy/s, and the second filtration set corresponding to average beam energy of 90 keV, with dose rate about 20 Gy/s. The temperature rise from this beam was measured by a calibrated thermistor embedded in the core which was then converted to absorbed dose to graphite by multiplying the rise in temperature by the specific heat capacity for graphite and the ratio of cross-sectional areas of the core and beam. Conversion of the measured absorbed dose to graphite to absorbed dose to water was achieved using Monte Carlo calculations with the EGSnrc code. The air kerma measurements from the free-air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. Absolute measurements of the IMBL dose rate were made using the graphite calorimeter and compared to measurements with the free-air chamber. The measurements were at three different depths in graphite and two different filtrations. The calorimetry measurements at depths in graphite show agreement within 1% with free-air chamber measurements, when converted to absorbed dose to water. The calorimetry at the surface and free-air chamber results show agreement of order 3% when converted to absorbed dose to water. The combined standard uncertainty is 3.9%. The good agreement of the graphite calorimeter and free-air chamber results indicates that both devices are performing as expected. Further investigations at higher dose rates than 50 Gy/s are planned. At higher dose rates, recombination effects for the free-air chamber are much higher and expected to lead to much larger uncertainties. Since the graphite calorimeter does not have problems associated with dose rate, it is an appropriate primary standard detector for the synchrotron IMBL x rays and is the more accurate dosimeter for the higher dose rates expected in radiotherapy applications.

Estimation of Second Primary Cancer Risk After Treatment with Radioactive Iodine for Differentiated Thyroid Carcinoma.

PubMed

Corrêa, Nilton Lavatori; de Sá, Lidia Vasconcellos; de Mello, Rossana Corbo Ramalho

2017-02-01

An increase in the incidence of second primary cancers is the late effect of greatest concern that could occur in differentiated thyroid carcinoma (DTC) patients treated with radioactive iodine (RAI). The decision to treat a patient with RAI should therefore incorporate a careful risk-benefit analysis. The objective of this work was to adapt the risk-estimation models developed by the Biological Effects of Ionizing Radiation Committee to local epidemiological characteristics in order to assess the carcinogenesis risk from radiation in a population of Brazilian DTC patients treated with RAI. Absorbed radiation doses in critical organs were also estimated to determine whether they exceeded the thresholds for deterministic effects. A total of 416 DTC patients treated with RAI were retrospectively studied. Four organs were selected for absorbed dose estimation and subsequent calculation of carcinogenic risk: the kidney, stomach, salivary glands, and bone marrow. Absorbed doses were calculated by dose factors (absorbed dose per unit activity administered) previously established and based on standard human models. The lifetime attributable risk (LAR) of incidence of cancer as a function of age, sex, and organ-specific dose was estimated, relating it to the activity of RAI administered in the initial treatment. The salivary glands received the greatest absorbed doses of radiation, followed by the stomach, kidney, and bone marrow. None of these, however, surpassed the threshold for deterministic effects for a single administration of RAI. Younger patients received the same level of absorbed dose in the critical organs as older patients did. The lifetime attributable risk for stomach cancer incidence was by far the highest, followed in descending order by salivary-gland cancer, leukemia, and kidney cancer. RAI in a single administration is safe in terms of deterministic effects because even high-administered activities do not result in absorbed doses that exceed the thresholds for significant tissue reactions. The Biological Effects of Ionizing Radiation Committee mathematical models are a practical method of quantifying the risks of a second primary cancer, demonstrating a marked decrease in risk for younger patients with the administration of lower RAI activities and suggesting that only the smallest activities necessary to promote an effective ablation should be administered in low-risk DTC patients.

Radiation absorbed dose to bladder walls from positron emitters in the bladder content.

PubMed

Powell, G F; Chen, C T

1987-01-01

A method to calculate absorbed doses at depths in the walls of a static spherical bladder from a positron emitter in the bladder content has been developed. The beta ray dose component is calculated for a spherical model by employing the solutions to the integration of Loevinger and Bochkarev point source functions over line segments and a line segment source array technique. The gamma ray dose is determined using the specific gamma ray constant. As an example, absorbed radiation doses to the bladder walls from F-18 in the bladder content are presented for static spherical bladder models having radii of 2.0 and 3.5 cm, respectively. Experiments with ultra-thin thermoluminescent dosimeters (TLD's) were performed to verify the results of the calculations. Good agreement between TLD measurements and calculations was obtained.

IMAGE-GUIDED TREATMENT USING AN X-RAY THERAPY UNIT AND GOLD NANOPARTICLES: TEST OF CONCEPT.

PubMed

Le Loirec, Cindy; Chambellan, Dominique; Tisseur, David

2016-06-01

Gold nanoparticles (GNPs) have the potential to enhance the radiation dose locally in conjunction with kV X-rays used for radiation therapy. As for other radiotherapy modalities, the absorbed dose needs to be controlled. To do that, it is an advantage to know the distribution of GNPs. However, no effective imaging tool exists to determine the GNP distribution in vivo. Various approaches have been proposed to determine the concentration of GNPs and its distribution in a tumour and in other organs and tissues. X-ray fluorescence computed tomography (XFCT) is a promising imaging technique to do that. A new experimental device based on the XFCT technique allowing the in vivo control of GNP radiotherapy treatments is proposed. As a test of concept, experimental acquisitions and Monte Carlo simulations were performed to determine the performance that a XFCT detector has to fulfil. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Randomized comparison of operator radiation exposure comparing transradial and transfemoral approach for percutaneous coronary procedures: rationale and design of the minimizing adverse haemorrhagic events by TRansradial access site and systemic implementation of angioX - RAdiation Dose study (RAD-MATRIX).

PubMed

Sciahbasi, Alessandro; Calabrò, Paolo; Sarandrea, Alessandro; Rigattieri, Stefano; Tomassini, Francesco; Sardella, Gennaro; Zavalloni, Dennis; Cortese, Bernardo; Limbruno, Ugo; Tebaldi, Matteo; Gagnor, Andrea; Rubartelli, Paolo; Zingarelli, Antonio; Valgimigli, Marco

2014-06-01

Radiation absorbed by interventional cardiologists is a frequently under-evaluated important issue. Aim is to compare radiation dose absorbed by interventional cardiologists during percutaneous coronary procedures for acute coronary syndromes comparing transradial and transfemoral access. The randomized multicentre MATRIX (Minimizing Adverse Haemorrhagic Events by TRansradial Access Site and Systemic Implementation of angioX) trial has been designed to compare the clinical outcome of patients with acute coronary syndromes treated invasively according to the access site (transfemoral vs. transradial) and to the anticoagulant therapy (bivalirudin vs. heparin). Selected experienced interventional cardiologists involved in this study have been equipped with dedicated thermoluminescent dosimeters to evaluate the radiation dose absorbed during transfemoral or right transradial or left transradial access. For each access we evaluate the radiation dose absorbed at wrist, at thorax and at eye level. Consequently the operator is equipped with three sets (transfemoral, right transradial or left transradial access) of three different dosimeters (wrist, thorax and eye dosimeter). Primary end-point of the study is the procedural radiation dose absorbed by operators at thorax. An important secondary end-point is the procedural radiation dose absorbed by operators comparing the right or left radial approach. Patient randomization is performed according to the MATRIX protocol for the femoral or radial approach. A further randomization for the radial approach is performed to compare right and left transradial access. The RAD-MATRIX study will probably consent to clarify the radiation issue for interventional cardiologist comparing transradial and transfemoral access in the setting of acute coronary syndromes. Copyright © 2014 Elsevier Inc. All rights reserved.

Case control study to assess the possibility of decrease the risk of osteoradionecrosis in relation to the dose of radiation absorbed by the jaw

PubMed Central

Carini, Fabrizio; Bucalo, Concetta; Saggese, Vito; Monai, Dario; Porcaro, Gianluca

2012-01-01

Summary Aims the assessment of the limit dose for the organs at risk in external radiotherapy is a fundamental step to guarantee an optimal risk-benefit ratio. The aim of this study was to assess, through contouring the single dental cavities, the absorbed radiation dose on irradiated alveolar bones during the treatment of cervico-facial tumours, so as to test the correlation between the absorbed dose of radiation at alveolar level and the level of individual surgical risk for osteonecrosis. Materials and methods we selected 45 out of 89 patients on the basis of different exclusion criteria. Nine of these patients showed evidence of osteoradionecrosis. The patients were treated either with 3D conformational radiation therapy (3D-CRT) or with intensity-modulated radiation therapy (IMRT), there after alveolar bones were contoured using computed axial tomography (CAT scans) carried out following oncological and dental treatment. The dose-volume histograms (DVH) were obtained on the basis of such data, which included those relating to the dental cavities in addition to those inherent to the tumours and the organs at risk. Results all patients, irrespective of type of treatment, received an average of 60 to 70 grays in 30/35 sittings. The patients treated with IMRT showed higher variation in absorbed radiation dose than those treated with 3D-CRT. The alveolar encirclement allowed the assessment of the absorbed radiation dose, and consequently it also allowed to assess the individual surgical risk for osteonecrosis in patients with head and neck tumours who underwent radiography treatment. Conclusions the study of DVH allows the assessment of limit dose and the detection of the areas at greater risk for osteoradionecrosis before dental surgery. PMID:23285316

Visible photoluminescence of color centers in LiF crystals for absorbed dose evaluation in clinical dosimetry

NASA Astrophysics Data System (ADS)

Villarreal-Barajas, J. E.; Piccinini, M.; Vincenti, M. A.; Bonfigli, F.; Khan, R. F.; Montereali, R. M.

2015-04-01

Among insulating materials, lithium fluoride (LiF) has been successfully used as ionizing radiation dosemeter for more than 60 years. Thermoluminescence (TL) has been the most commonly used reading technique to evaluate the absorbed dose. Lately, optically stimulated luminescence (OSL) of visible emitting color centers (CCs) has also been explored in pure and doped LiF. This work focuses on the experimental behaviour of nominally pure LiF crystals dosemeters for 6 MV x rays at low doses based on photoluminescence (PL) of radiation induced CCs. Polished LiF crystals were irradiated using 6 MV x rays produced by a clinical linear accelerator. The doses (absorbed dose to water) covered the 1-100 Gy range. Optical absorption spectra show stable formation of primary F defects up to a maximum concentration of 2×1016 cm-3, while no significant M absorption band at around 450 nm was detected. On the other hand, under Argon laser excitation at 458 nm, PL spectra of the irradiated LiF crystals clearly exhibited the characteristic F2 and F+3 visible broad emission bands. Their sum intensity is linearly proportional to the absorbed dose in the investigated range. PL integrated intensity was also measured using a conventional fluorescence optical microscope under blue lamp illumination. The relationship between the absorbed dose and the integrated F2 and F+3 PL intensities, represented by the net average pixel number in the optical fluorescence images, is also fairly linear. Even at the low point defect densities obtained at the investigated doses, these preliminary experimental results are encouraging for further investigation of CCs PL in LiF crystals for clinical dosimetry.

ORGAN-SPECIFIC EXTERNAL DOSE COEFFICIENTS AND PROTECTIVE APRON TRANSMISSION FACTORS FOR HISTORICAL DOSE RECONSTRUCTION FOR MEDICAL PERSONNEL

PubMed Central

Simon, Steven L.

2014-01-01

While radiation absorbed dose (Gy) to the skin or other organs is sometimes estimated for patients from diagnostic radiologic examinations or therapeutic procedures, rarely is occupationally-received radiation absorbed dose to individual organs/tissues estimated for medical personnel, e.g., radiologic technologists or radiologists. Generally, for medical personnel, equivalent or effective radiation doses are estimated for compliance purposes. In the very few cases when organ doses to medical personnel are reconstructed, the data is usually for the purpose of epidemiologic studies, e.g., a study of historical doses and risks to a cohort of about 110,000 radiologic technologists presently underway at the U.S. National Cancer Institute. While ICRP and ICRU have published organ-specific external dose conversion coefficients (DCCs), i.e., absorbed dose to organs and tissues per unit air kerma and dose equivalent per unit air kerma, those factors have been primarily published for mono-energetic photons at selected energies. This presents two related problems for historical dose reconstruction, both of which are addressed here. It is necessary to derive conversion factors values for (i) continuous distributions of energy typical of diagnostic medical x rays (bremsstrahlung radiation), and (ii) for energies of particular radioisotopes used in medical procedures, neither of which are presented in published tables. For derivation of DCCs for bremsstrahlung radiation, combinations of x-ray tube potentials and filtrations were derived for different time periods based on a review of relevant literature. Three peak tube potentials (70 kV, 80 kV, and 90 kV) with four different amounts of beam filtration were determined to be applicable for historic dose reconstruction. The probability of these machine settings were assigned to each of the four time periods (earlier than 1949, 1949-1954, 1955-1968, and after 1968). Continuous functions were fit to each set of discrete values of the ICRP/ICRU mono-energetic DCCs and the functions integrated over the air-kerma weighted photon fluence of the 12 defined x-ray spectra. The air kerma-weighted DCCs in this work were developed specifically for an irradiation geometry of anterior to posterior (AP) and for the following tissues: thyroid, breast, ovary, lens of eye, lung, colon, testes, heart, skin (anterior side only), red bone marrow (RBM), heart, and brain. In addition, a series of functional relationships to predict DT per Ka values for RBM dependent on body mass index [BMI (kg m−2) ≡ weight per height2] and average photon energy were derived from a published analysis. Factors to account for attenuation of radiation by protective lead aprons were also developed. Because lead protective aprons often worn by radiology personnel not only reduce the intensity of x-ray exposure but also appreciably harden the transmitted fluence of bremsstrahlung x rays, DCCs were separately calculated for organs possibly protected by lead aprons by considering three cases: no apron, 0.25 mm Pb apron, and 0.5 mm Pb apron. For estimation of organ doses from conducting procedures with radioisotopes, continuous functions of the reported mono-energetic values were developed and DCCs were derived by estimation of the function at relevant energies. By considering the temporal changes in primary exposure-related parameters, e.g., energy distribution, the derived DCCs and transmission factors presented here allow for more realistic historical dose reconstructions for medical personnel when monitoring badge readings are the primary data on which estimation of an individual's organ doses are based. PMID:21617389

Organ-specific external dose coefficients and protective apron transmission factors for historical dose reconstruction for medical personnel.

PubMed

Simon, Steven L

2011-07-01

While radiation absorbed dose (Gy) to the skin or other organs is sometimes estimated for patients from diagnostic radiologic examinations or therapeutic procedures, rarely is occupationally-received radiation absorbed dose to individual organs/tissues estimated for medical personnel; e.g., radiologic technologists or radiologists. Generally, for medical personnel, equivalent or effective radiation doses are estimated for compliance purposes. In the very few cases when organ doses to medical personnel are reconstructed, the data is usually for the purpose of epidemiologic studies; e.g., a study of historical doses and risks to a cohort of about 110,000 radiologic technologists presently underway at the U.S. National Cancer Institute. While ICRP and ICRU have published organ-specific external dose conversion coefficients (DCCs) (i.e., absorbed dose to organs and tissues per unit air kerma and dose equivalent per unit air kerma), those factors have been published primarily for mono-energetic photons at selected energies. This presents two related problems for historical dose reconstruction, both of which are addressed here. It is necessary to derive conversion factor values for (1) continuous distributions of energy typical of diagnostic medical x-rays (bremsstrahlung radiation), and (2) energies of particular radioisotopes used in medical procedures, neither of which are presented in published tables. For derivation of DCCs for bremsstrahlung radiation, combinations of x-ray tube potentials and filtrations were derived for different time periods based on a review of relevant literature. Three peak tube potentials (70 kV, 80 kV, and 90 kV) with four different amounts of beam filtration were determined to be applicable for historic dose reconstruction. The probabilities of these machine settings were assigned to each of the four time periods (earlier than 1949, 1949-1954, 1955-1968, and after 1968). Continuous functions were fit to each set of discrete values of the ICRP/ICRU mono-energetic DCCs and the functions integrated over the air-kerma weighted photon fluence of the 12 defined x-ray spectra. The air kerma-weighted DCCs in this work were developed specifically for an irradiation geometry of anterior to posterior (AP) and for the following tissues: thyroid, breast, ovary, lens of eye, lung, colon, testes, heart, skin (anterior side only), red bone marrow (RBM), and brain. In addition, a series of functional relationships to predict DT Ka-1 values for RBM dependent on body mass index [BMI (kg m-2) ≡ weight per height] and average photon energy were derived from a published analysis. Factors to account for attenuation of radiation by protective lead aprons were also developed. Because lead protective aprons often worn by radiology personnel not only reduce the intensity of x-ray exposure but also appreciably harden the transmitted fluence of bremsstrahlung x-rays, DCCs were separately calculated for organs possibly protected by lead aprons by considering three cases: no apron, 0.25 mm Pb apron, and 0.5 mm Pb apron. For estimation of organ doses from conducting procedures with radioisotopes, continuous functions of the reported mono-energetic values were developed, and DCCs were derived by estimation of the function at relevant energies. By considering the temporal changes in primary exposure-related parameters (e.g., energy distribution), the derived DCCs and transmission factors presented here allow for more realistic historical dose reconstructions for medical personnel when monitoring badge readings are the primary data on which estimation of an individual's organ doses are based.

Analysis of Plane-Parallel Electron Beam Propagation in Different Media by Numerical Simulation Methods

NASA Astrophysics Data System (ADS)

Miloichikova, I. A.; Bespalov, V. I.; Krasnykh, A. A.; Stuchebrov, S. G.; Cherepennikov, Yu. M.; Dusaev, R. R.

2018-04-01

Simulation by the Monte Carlo method is widely used to calculate the character of ionizing radiation interaction with substance. A wide variety of programs based on the given method allows users to choose the most suitable package for solving computational problems. In turn, it is important to know exactly restrictions of numerical systems to avoid gross errors. Results of estimation of the feasibility of application of the program PCLab (Computer Laboratory, version 9.9) for numerical simulation of the electron energy distribution absorbed in beryllium, aluminum, gold, and water for industrial, research, and clinical beams are presented. The data obtained using programs ITS and Geant4 being the most popular software packages for solving the given problems and the program PCLab are presented in the graphic form. A comparison and an analysis of the results obtained demonstrate the feasibility of application of the program PCLab for simulation of the absorbed energy distribution and dose of electrons in various materials for energies in the range 1-20 MeV.

Absorbed organ and effective doses from digital intra-oral and panoramic radiography applying the ICRP 103 recommendations for effective dose estimations

PubMed Central

Thilander-Klang, Anne; Ylhan, Betȕl; Lofthag-Hansen, Sara; Ekestubbe, Annika

2016-01-01

Objective: During dental radiography, the salivary and thyroid glands are at radiation risk. In 2007, the International Commission on Radiological Protection (ICRP) updated the methodology for determining the effective dose, and the salivary glands were assigned tissue-specific weighting factors for the first time. The aims of this study were to determine the absorbed dose to the organs and to calculate, applying the ICRP publication 103 tissue-weighting factors, the effective doses delivered during digital intraoral and panoramic radiography. Methods: Thermoluminescent dosemeter measurements were performed on an anthropomorphic head and neck phantom. The organ-absorbed doses were measured at 30 locations, representing different radiosensitive organs in the head and neck, and the effective dose was calculated according to the ICRP recommendations. Results: The salivary glands and the oral mucosa received the highest absorbed doses from both intraoral and panoramic radiography. The effective dose from a full-mouth intraoral examination was 15 μSv and for panoramic radiography, the effective dose was in the range of 19–75 μSv, depending on the panoramic equipment used. Conclusion: The effective dose from a full-mouth intraoral examination is lower and that from panoramic radiography is higher than previously reported. Clinicians should be aware of the higher effective dose delivered during panoramic radiography and the risk–benefit profile of this technique must be assessed for the individual patient. Advances in knowledge: The effective dose of radiation from panoramic radiography is higher than previously reported and there is large variability in the delivered radiation dosage among the different types of equipment used. PMID:27452261

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

Cederkrantz, Elin; Andersson, Håkan; Bernhardt, Peter

Purpose: Ovarian cancer is often diagnosed at an advanced stage with dissemination in the peritoneal cavity. Most patients achieve clinical remission after surgery and chemotherapy, but approximately 70% eventually experience recurrence, usually in the peritoneal cavity. To prevent recurrence, intraperitoneal (i.p.) targeted α therapy has been proposed as an adjuvant treatment for minimal residual disease after successful primary treatment. In the present study, we calculated absorbed and relative biological effect (RBE)-weighted (equivalent) doses in relevant normal tissues and estimated the effective dose associated with i.p. administration of {sup 211}At-MX35 F(ab'){sub 2}. Methods and Materials: Patients in clinical remission after salvage chemotherapymore » for peritoneal recurrence of ovarian cancer underwent i.p. infusion of {sup 211}At-MX35 F(ab'){sub 2}. Potassium perchlorate was given to block unwanted accumulation of {sup 211}At in thyroid and other NIS-containing tissues. Mean absorbed doses to normal tissues were calculated from clinical data, including blood and i.p. fluid samples, urine, γ-camera images, and single-photon emission computed tomography/computed tomography images. Extrapolation of preclinical biodistribution data combined with clinical blood activity data allowed us to estimate absorbed doses in additional tissues. The equivalent dose was calculated using an RBE of 5 and the effective dose using the recommended weight factor of 20. All doses were normalized to the initial activity concentration of the infused therapy solution. Results: The urinary bladder, thyroid, and kidneys (1.9, 1.8, and 1.7 mGy per MBq/L) received the 3 highest estimated absorbed doses. When the tissue-weighting factors were applied, the largest contributors to the effective dose were the lungs, stomach, and urinary bladder. Using 100 MBq/L, organ equivalent doses were less than 10% of the estimated tolerance dose. Conclusion: Intraperitoneal {sup 211}At-MX35 F(ab'){sub 2} treatment is potentially a well-tolerated therapy for locally confined microscopic ovarian cancer. Absorbed doses to normal organs are low, but because the effective dose potentially corresponds to a risk of treatment-induced carcinogenesis, optimization may still be valuable.« less

NOTE: On the need to revise the arm structure in stylized anthropomorphic phantoms in lateral photon irradiation geometry

NASA Astrophysics Data System (ADS)

Lee, Choonsik; Lee, Choonik; Lee, Jai-Ki

2006-11-01

Distributions of radiation absorbed dose within human anatomy have been estimated through Monte Carlo radiation transport techniques implemented for two different classes of computational anthropomorphic phantoms: (1) mathematical equation-based stylized phantoms and (2) tomographic image-based voxel phantoms. Voxel phantoms constructed from tomographic images of real human anatomy have been actively developed since the late 1980s to overcome the anatomical approximations necessary with stylized phantoms, which themselves have been utilized since the mid 1960s. However, revisions of stylized phantoms have also been pursued in parallel to the development of voxel phantoms since voxel phantoms (1) are initially restricted to the individual-specific anatomy of the person originally imaged, (2) must be restructured on an organ-by-organ basis to conform to reference individual anatomy and (3) cannot easily represent very fine anatomical structures and tissue layers that are thinner than the voxel dimensions of the overall phantom. Although efforts have been made to improve the anatomic realism of stylized phantoms, most of these efforts have been limited to attempts to alter internal organ structures. Aside from the internal organs, the exterior shapes, and especially the arm structures, of stylized phantoms are also far from realistic descriptions of human anatomy, and may cause dosimetry errors in the calculation of organ-absorbed doses for external irradiation scenarios. The present study was intended to highlight the need to revise the existing arm structure within stylized phantoms by comparing organ doses of stylized adult phantoms with those from three adult voxel phantoms in the lateral photon irradiation geometry. The representative stylized phantom, the adult phantom of the Oak Ridge National Laboratory (ORNL) series and two adult male voxel phantoms, KTMAN-2 and VOXTISS8, were employed for Monte Carlo dose calculation, and data from another voxel phantom, VIP-Man, were obtained from literature sources. The absorbed doses for lungs, oesophagus, liver and kidneys that could be affected by arm structures in the lateral irradiation geometry were obtained for both classes of phantoms in lateral monoenergetic photon irradiation geometries. As expected, those organs in the ORNL phantoms received apparently higher absorbed doses than those in the voxel phantoms. The overestimation is mainly attributed to the relatively poor representation of the arm structure in the ORNL phantom in which the arm bones are embedded within the regions describing the phantom's torso. The results of this study suggest that the overestimation of organ doses, due to unrealistic arm representation, should be taken into account when stylized phantoms are employed for equivalent or effective dose estimates, especially in the case of an irradiation scenario with dominating lateral exposure. For such a reason, the stylized phantom arm structure definition should be revised in order to obtain more realistic evaluations.

SU-E-T-204: Comparison of Absorbed-Dose to Water in High-Energy Photon Beams Based On Addendum AAPM TG-51, IAEA TRS-398, and JSMP 12

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

Kinoshita, N; Kita, A; Yoshioka, C

Purpose: Several clinical reference dosimetry protocols for absorbed-dose to water have recently been published: The American Association of Physicists in Medicine (AAPM) published an Addendum to the AAPM’s TG-51 (Addendum TG-51) in April 2014, and the Japan Society of Medical Physics (JSMP) published the Japan Society of Medical Physics 12 (JSMP12), a clinical reference dosimetry protocol, in September 2012. This investigation compared and evaluated the absorbed-dose to water of high-energy photon beams according to Addendum TG-51, International Atomic Energy Agency Technical Report Series No. 398 (TRS-398), and JSMP12. Methods: Differences in the respective beam quality conversion factors with Addendum TG-51,more » TRS-398, and JSMP12 were analyzed and the absorbed-dose to water using 6- and 10-MV photon beams was measured according to the protocols recommended in Addendum TG-51, TRS-398, and JSMP12. The measurements were conducted using two Farmer-type ionization chambers, Exradin A12 and PTW 30013. Results: The beam quality conversion factors for both the 6- and 10-MV photon beams with Addendum TG-51 were within 0.6%, in agreement with the beam quality conversion factors with TRS-398 and JSMP12. The Exradin A12 provided an absorbed-dose to water ratio from 1.003 to 1.006 with TRS-398 / Addendum TG-51 and from 1.004 to 1.005 with JSMP 12 / Addendum TG-51, whereas the PTW 30013 provided a ratio of 1.001 with TRS-398 / Addendum TG-51 and a range from 0.997 to 0.999 with JSMP 12 / Addendum TG-51. Conclusion: Despite differences in the beam quality conversion factor, no major differences were seen in the absorbed-dose to water with Addendum TG-51, TRS-398, and JSMP12. However, Addendum TG-51 provides the most recent data for beam quality conversion factors based on Monte Carlo simulation and greater detail for the measurement protocol. Therefore, the absorbed-dose to water measured with Addendum TG-51 is an estimate with less uncertainty.« less

Analysis of localised dose distribution in human body by Monte Carlo code system for photon irradiation.

PubMed

Ohnishi, S; Odano, N; Nariyama, N; Saito, K

2004-01-01

In usual personal dosimetry, whole body irradiation is assumed. However, the opportunity of partial irradiation is increasing and the tendencies of protection quantities caused under those irradiation conditions are different. The code system has been developed and effective dose and organ absorbed doses have been calculated in the case of horizontal narrow photon beam irradiated from various directions at three representative body sections, 40, 50 and 60 cm originating from the top of the head. This work covers 24 beam directions, each 15 degrees angle ranging from 0 degrees to 345 degrees, three energy levels, 45 keV, 90 keV and 1.25 MeV, and three beam diameters of 1, 2 and 4 cm. These results show that the beam injected from diagonally front or other specific direction causes peak dose in the case of partial irradiation.

Comparison of dosimetric properties among four commercial multi-detector computed tomography scanners.

PubMed

Ohno, Takeshi; Araki, Fujio; Onizuka, Ryota; Hatemura, Masahiro; Shimonobou, Toshiaki; Sakamoto, Takashi; Okumura, Shuichiro; Ideguchi, Daichi; Honda, Keiichi; Kawata, Kenji

2017-03-01

This study compared dosimetric properties among four commercial multi-detector CT (MDCT) scanners. The X-ray beam characteristics were obtained from photon intensity attenuation curves of aluminum and off-center ratio (OCR) profiles in air, which were measured with four commercial MDCT scanners. The absorbed dose for MDCT scanners was evaluated with Farmer ionization chamber measurements at the center and four peripheral points in the body- and head-type cylindrical water phantoms. Measured collected charge was converted to absorbed dose using a 60 Co absorbed dose-to-water calibration factor and Monte Carlo (MC)-calculated correction factors. Four MDCT scanners were modeled to correspond with measured X-ray beam characteristics using GMctdospp (IMPS, Germany) software. Al half-value layers (Al-HVLs) with a body-bowtie filter determined from measured Al-attenuation curves ranged 7.2‒9.1mm at 120kVp and 6.1‒8.0mm at 100kVp. MC-calculated Al-HVLs and OCRs in air were in acceptable agreement within 0.5mm and 5% of measured values, respectively. The percentage difference between nominal and actual beam width was greater with decreasing collimation width. The absorbed doses for MDCT scanners at 120kVp ranged 5.1‒7.1mGy and 10.8‒17.5mGy per 100mAs at the center in the body- and head-type water phantoms, respectively. Measured doses at four peripheral points were within 5% agreement of MC-calculated values. The absorbed dose at the center in both water phantoms increased with decreasing Al-HVL for the same charge on the focus. In this study the X-ray beam characteristics and the absorbed dose were measured and compared with calculated values for four MDCT scanners. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Preclinical Study of 68Ga-DOTATOC: Biodistribution Assessment in Syrian Rats and Evaluation of Absorbed Dose in Human Organs.

PubMed

Naderi, Mojdeh; Zolghadri, Samaneh; Yousefnia, Hassan; Ramazani, Ali; Jalilian, Amir Reza

2016-01-01

Gallium-68 DOTA-DPhe 1 -Tyr 3 -Octreotide ( 68 Ga-DOTATOC) has been applied by several European centers for the treatment of a variety of human malignancies. Nevertheless, definitive dosimetric data are yet unavailable. According to the Society of Nuclear Medicine and Molecular Imaging, researchers are investigating the safety and efficacy of this radiotracer to meet Food and Drug Administration requirements. The aim of this study was to introduce the optimized procedure for 68 Ga-DOTATOC preparation, using a novel germanium-68 ( 68 Ge)/ 68 Ga generator in Iran and evaluate the absorbed doses in numerous organs with high accuracy. The optimized conditions for preparing the radiolabeled complex were determined via several experiments by changing the ligand concentration, pH, temperature and incubation time. Radiochemical purity of the complex was assessed, using high-performance liquid chromatography and instant thin-layer chromatography. The absorbed dose of human organs was evaluated, based on biodistribution studies on Syrian rats via Radiation Absorbed Dose Assessment Resource Method. 68 Ga-DOTATOC was prepared with radiochemical purity of >98% and specific activity of 39.6 MBq/nmol. The complex demonstrated great stability at room temperature and in human serum at 37°C at least two hours after preparation. Significant uptake was observed in somatostatin receptor-positive tissues such as pancreatic and adrenal tissues (12.83 %ID/g and 0.91 %ID/g, respectively). Dose estimations in human organs showed that the pancreas, kidneys and adrenal glands received the maximum absorbed doses (0.105, 0.074 and 0.010 mGy/MBq, respectively). Also, the effective absorbed dose was estimated at 0.026 mSv/MBq for 68 Ga-DOTATOC. The obtained results showed that 68 Ga-DOTATOC can be considered as an effective agent for clinical PET imaging in Iran.

Dosimetric results in treatments of neuroblastoma and neuroendocrine tumors with {sup 131}I-metaiodobenzylguanidine with implications for the activity to administer

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

Mínguez, Pablo, E-mail: pablo.minguezgabina@osakidetza.net; Flux, Glenn; Genollá, José

2015-07-15

Purpose: The aim was to investigate whole-body and red marrow absorbed doses in treatments of neuroblastoma (NB) and adult neuroendocrine tumors (NETs) with {sup 131}I-metaiodobenzylguanidine and to propose a simple method for determining the activity to administer when dosimetric data for the individual patient are not available. Methods: Nine NB patients and six NET patients were included, giving in total 19 treatments as four patients were treated twice. Whole-body absorbed doses were determined from dose-rate measurements and planar gamma-camera imaging. For six NB and five NET treatments, red marrow absorbed doses were also determined using the blood-based method. Results: Dosimetricmore » data from repeated administrations in the same patient were consistent. In groups of NB and NET patients, similar whole-body residence times were obtained, implying that whole-body absorbed dose per unit of administered activity could be reasonably well described as a power function of the patient mass. For NB, this functional form was found to be consistent with dosimetric data from previously published studies. The whole-body to red marrow absorbed dose ratio was similar among patients, with values of 1.4 ± 0.6–1.7 ± 0.7 (1 standard deviation) in NB treatments and between 1.5 ± 0.6 and 1.7 ± 0.7 (1 standard deviation) in NET treatments. Conclusions: The consistency of dosimetric results between administrations for the same patient supports prescription of the activity based on dosimetry performed in pretreatment studies, or during the first administration in a fractionated schedule. The expressions obtained for whole-body absorbed doses per unit of administered activity as a function of patient mass for NB and NET treatments are believed to be a useful tool to estimate the activity to administer at the stage when the individual patient biokinetics has not yet been measured.« less

Preclinical Study of 68Ga-DOTATOC: Biodistribution Assessment in Syrian Rats and Evaluation of Absorbed Dose in Human Organs

PubMed Central

Naderi, Mojdeh; Zolghadri, Samaneh; Yousefnia, Hassan; Ramazani, Ali; Jalilian, Amir Reza

2016-01-01

Objective(s): Gallium-68 DOTA-DPhe1-Tyr3-Octreotide (68Ga-DOTATOC) has been applied by several European centers for the treatment of a variety of human malignancies. Nevertheless, definitive dosimetric data are yet unavailable. According to the Society of Nuclear Medicine and Molecular Imaging, researchers are investigating the safety and efficacy of this radiotracer to meet Food and Drug Administration requirements. The aim of this study was to introduce the optimized procedure for 68Ga-DOTATOC preparation, using a novel germanium-68 (68Ge)/68Ga generator in Iran and evaluate the absorbed doses in numerous organs with high accuracy. Methods: The optimized conditions for preparing the radiolabeled complex were determined via several experiments by changing the ligand concentration, pH, temperature and incubation time. Radiochemical purity of the complex was assessed, using high-performance liquid chromatography and instant thin-layer chromatography. The absorbed dose of human organs was evaluated, based on biodistribution studies on Syrian rats via Radiation Absorbed Dose Assessment Resource Method. Results: 68Ga-DOTATOC was prepared with radiochemical purity of >98% and specific activity of 39.6 MBq/nmol. The complex demonstrated great stability at room temperature and in human serum at 37°C at least two hours after preparation. Significant uptake was observed in somatostatin receptor-positive tissues such as pancreatic and adrenal tissues (12.83 %ID/g and 0.91 %ID/g, respectively). Dose estimations in human organs showed that the pancreas, kidneys and adrenal glands received the maximum absorbed doses (0.105, 0.074 and 0.010 mGy/MBq, respectively). Also, the effective absorbed dose was estimated at 0.026 mSv/MBq for 68Ga-DOTATOC. Conclusion: The obtained results showed that 68Ga-DOTATOC can be considered as an effective agent for clinical PET imaging in Iran. PMID:27904870

Assessment of background gamma radiation levels using airborne gamma ray spectrometer data over uranium deposits, Cuddapah Basin, India - A comparative study of dose rates estimated by AGRS and PGRS.

PubMed

Srinivas, D; Ramesh Babu, V; Patra, I; Tripathi, Shailesh; Ramayya, M S; Chaturvedi, A K

2017-02-01

The Atomic Minerals Directorate for Exploration and Research (AMD) has conducted high-resolution airborne gamma ray spectrometer (AGRS), magnetometer and time domain electromagnetic (TDEM) surveys for uranium exploration, along the northern margins of Cuddapah Basin. The survey area includes well known uranium deposits such as Lambapur-Peddagattu, Chitrial and Koppunuru. The AGRS data collected for uranium exploration is utilised for estimating the average absorbed rates in air due to radio-elemental (potassium in %, uranium and thorium in ppm) distribution over these known deposit areas. Further, portable gamma ray spectrometer (PGRS) was used to acquire data over two nearby locations one from Lambapur deposit, and the other from known anomalous zone and subsequently average gamma dose rates were estimated. Representative in-situ rock samples were also collected from these two areas and subjected to radio-elemental concentration analysis by gamma ray spectrometer (GRS) in the laboratory and then dose rates were estimated. Analyses of these three sets of results complement one another, thereby providing a comprehensive picture of the radiation environment over these deposits. The average absorbed area wise dose rate level is estimated to be 130 ± 47 nGy h -1 in Lambapur-Peddagattu, 186 ± 77 nGy h -1 in Chitrial and 63 ± 22 nGy h -1 in Koppunuru. The obtained average dose levels are found to be higher than the world average value of 54 nGy h -1 . The gamma absorbed dose rates in nGy h -1 were converted to annual effective dose rates in mSv y -1 as proposed by the United Nations Scientific Committee on the Effect of Atomic Radiation (UNSCEAR). The annual average effective dose rates for the entire surveyed area is 0.12 mSv y -1 , which is much lower than the recommended limit of 1 mSv y -1 by International Commission on Radiation protection (ICRP). It may be ascertained here that the present study establishes a reference data set (baseline) in these areas to assess any changes in gamma radiation levels due to mining and milling activities in future. Copyright © 2016 Elsevier Ltd. All rights reserved.

Rational evaluation of the therapeutic effect and dosimetry of auger electrons for radionuclide therapy in a cell culture model.

PubMed

Shinohara, Ayaka; Hanaoka, Hirofumi; Sakashita, Tetsuya; Sato, Tatsuhiko; Yamaguchi, Aiko; Ishioka, Noriko S; Tsushima, Yoshito

2018-02-01

Radionuclide therapy with low-energy auger electron emitters may provide high antitumor efficacy while keeping the toxicity to normal organs low. Here we evaluated the usefulness of an auger electron emitter and compared it with that of a beta emitter for tumor treatment in in vitro models and conducted a dosimetry simulation using radioiodine-labeled metaiodobenzylguanidine (MIBG) as a model compound. We evaluated the cellular uptake of 125 I-MIBG and the therapeutic effects of 125 I- and 131 I-MIBG in 2D and 3D PC-12 cell culture models. We used a Monte Carlo simulation code (PHITS) to calculate the absorbed radiation dose of 125 I or 131 I in computer simulation models for 2D and 3D cell cultures. In the dosimetry calculation for the 3D model, several distribution patterns of radionuclide were applied. A higher cumulative dose was observed in the 3D model due to the prolonged retention of MIBG compared to the 2D model. However, 125 I-MIBG showed a greater therapeutic effect in the 2D model compared to the 3D model (respective EC 50 values in the 2D and 3D models: 86.9 and 303.9 MBq/cell), whereas 131 I-MIBG showed the opposite result (respective EC 50 values in the 2D and 3D models: 49.4 and 30.2 MBq/cell). The therapeutic effect of 125 I-MIBG was lower than that of 131 I-MIBG in both models, but the radionuclide-derived difference was smaller in the 2D model. The dosimetry simulation with PHITS revealed the influence of the radiation quality, the crossfire effect, radionuclide distribution, and tumor shape on the absorbed dose. Application of the heterogeneous distribution series dramatically changed the radiation dose distribution of 125 I-MIBG, and mitigated the difference between the estimated and measured therapeutic effects of 125 I-MIBG. The therapeutic effect of 125 I-MIBG was comparable to that of 131 I-MIBG in the 2D model, but the efficacy was inferior to that of 131 I-MIBG in the 3D model, since the crossfire effect is negligible and the homogeneous distribution of radionuclides was insufficient. Thus, auger electrons would be suitable for treating small-sized tumors. The design of radiopharmaceuticals with auger electron emitters requires particularly careful consideration of achieving a homogeneous distribution of the compound in the tumor.

Poster — Thur Eve — 33: The Influence of a Modeled Treatment Couch on Dose Distributions During IMRT and RapidArc Treatment Delivery

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

Aldosary, Ghada; Nobah, Ahmad; Al-Zorkani, Faisal

2014-08-15

Treatment couches have been known to perturb dose delivery in patients. This effect is most pronounced in techniques such as IMRT and RapidArc. Although modern treatment planning systems (TPS) include data for a “default” treatment couch, actual couches are not manufactured identically. Thus, variations in their Hounsfield Unit (HU) values may exist. This study demonstrates a practical and simple method of acquiring reliable HU data for any treatment couch. We also investigate the effects of both the default and modeled treatment couches on absorbed dose. Experimental verifications show that by neglecting to incorporate the treatment couch in the TPS, dosemore » differences of up to 9.5% and 7.3% were present for 4 MV and 10 MV photon beams, respectively. Furthermore, a clinical study based on a cohort of 20 RapidArc and IMRT (brain, pelvis and abdominal) cases is performed. 2D dose distributions show that without the couch in the planning phase, differences ≤ 4.6% and 5.9% for RapidArc and IMRT cases are present for the same cases that the default couch was added to. Additionally, in comparison to the default couch, employing the modeled couch in the calculation process influences dose distributions by ≤ 2.7% and 8% for RapidArc and IMRT cases, respectively. This result was found to be site specific; where an accurate couch proves to be preferable for IMRT brain plans. As such, adding the couch during dose calculation decreases dose calculation errors, and a precisely modeled treatment couch offers higher dose delivery accuracy for brain treatment using IMRT.« less

Optimization of permanent breast seed implant dosimetry incorporating tissue heterogeneity

NASA Astrophysics Data System (ADS)

Mashouf, Shahram

Seed brachytherapy is currently used for adjuvant radiotherapy of early stage prostate and breast cancer patients. The current standard for calculation of dose around brachytherapy sources is based on the AAPM TG43 formalism, which generates the dose in homogeneous water medium. Recently, AAPM task group no. 186 (TG186) emphasized the importance of accounting for heterogeneities. In this work we introduce an analytical dose calculation algorithm in heterogeneous media using CT images. The advantages over other methods are computational efficiency and the ease of integration into clinical use. An Inhomogeneity Correction Factor (ICF) is introduced as the ratio of absorbed dose in tissue to that in water medium. ICF is a function of tissue properties and independent of the source structure. The ICF is extracted using CT images and the absorbed dose in tissue can then be calculated by multiplying the dose as calculated by the TG43 formalism times ICF. To evaluate the methodology, we compared our results with Monte Carlo simulations as well as experiments in phantoms with known density and atomic compositions. The dose distributions obtained through applying ICF to TG43 protocol agreed very well with those of Monte Carlo simulations and experiments in all phantoms. In all cases, the mean relative error was reduced by at least a factor of two when ICF correction factor was applied to the TG43 protocol. In conclusion we have developed a new analytical dose calculation method, which enables personalized dose calculations in heterogeneous media using CT images. The methodology offers several advantages including the use of standard TG43 formalism, fast calculation time and extraction of the ICF parameters directly from Hounsfield Units. The methodology was implemented into our clinical treatment planning system where a cohort of 140 patients were processed to study the clinical benefits of a heterogeneity corrected dose.

Decomposition byproducts induced by gamma radiation and their toxicity: the case of 2-nitrophenol.

PubMed

Alsager, Omar A; Basfar, Ahmed A; Muneer, Majid

2018-04-01

The induced degradation and detoxification of 2-nitrophenol (2-NP) in aqueous media by gamma irradiation were carefully evaluated in this study. Gamma radiation at absorbed doses as low as 20 kGy was able to degrade 2-NP to reach a removal of at least 85% across the investigated range of concentration (50-150 ppm). 2-NP breaks down to aromatic-based compounds with increasing number of byproducts upon increasing the radiation treatment from the absorbed dose of 50% decomposition (D 50 ) to the absorbed dose of 90% decomposition (D 90 ), after which no byproducts could be detected, indicating the formation of undetectable aliphatic hydrocarbons, insoluble, or volatile byproducts. Toxicology studies showed that the degradation of 2-NP under absorbed doses up to D 90 resulted in a more toxic byproduct than the parent compound, and a remarkable reduction in the toxicity was observed with the irradiated samples with absorbed doses above D 90 . Varying the pH of the media to acidic or basic conditions did not significantly alter the degradation behavior of 2-NP. However, a notable improvement of the detoxification was associated with the samples of acidic pH. Adding 0.5% of H 2 O 2 to 2-NP solutions had a positive effect by reducing D 90 by a factor of nine and diminishing the toxicity by twofolds.

Nicotine pharmacokinetics and its application to intake from smoking.

PubMed Central

Feyerabend, C; Ings, R M; Russel, M A

1985-01-01

Five subjects were given 25 micrograms/kg nicotine intravenously over 1 min, before and after a loading period involving the smoking of six cigarettes. Plasma nicotine concentrations declined in a biphasic manner, the half-lives of the initial and terminal phases averaging 9 min and 133 min respectively. Terminal half-lives before and after the loading period were essentially the same suggesting the absence of saturation kinetics at nicotine concentrations that build up during smoking. The plasma clearance of nicotine and the volume of distribution were very high averaging 915 ml/min and 1731, respectively. Two approaches were used to calculate the nicotine intake from smoking. The average dose of nicotine absorbed from one cigarette was 1.06 mg which was 82% of the standard machine-smoked yield of 1.3 mg. To illustrate their potential use in 'nicotine titration' studies, these approaches were used to compare nicotine intake from smoking a high (2.4 mg) and low (0.6 mg) nicotine cigarette. The dose of nicotine absorbed averaged 1.14 mg and 0.86 mg per cigarette respectively, being 48% and 143% of the machine-smoked yields. PMID:3986082

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

Boyd, G.S.; Merrick, M.V.; Monks, R.

Four selenium-labeled free bile acids and four selenium-labeled conjugated bile acids, labeled with Se-75 at the C-19, C-22, C-23, or C-24 position, have been synthesized and their absorption and excretion compared with that of (24-14C)cholic acid, following both oral and intravenous administration. All but one of the compounds is absorbed and excreted in bile to a significant extent. One compound, SeHCAT, has been selected for particular study. It is quantitatively absorbed from the gut at the same rate as cholic acid, and both are excreted into the bile at the same rate. It remains almost entirely confined to the enterohepaticmore » circulation (the gut, liver, and biliary tree) and excretion is exclusively fecal. Whole-body retention, measured for 41 days, and tissue distributions suggest that the absorbed radiation dose would be small compared with that in many established tests. Such a compound offers the possibility of a simple, novel, and aesthetically acceptable method of investigating small-bowel disease. It therefore merits further investigation.« less

Accuracy of megavolt radiation dosimetry using thermoluminescent lithium fluoride.

PubMed

Rudén, B I; Bengtsson, L G

1977-04-01

The relative light output per Gy in polystyrene for roentgen beams of 6 and 42 MV and electrons between 2.2 and 34.5 MeV relative to 60Co gamma radiation is reported for different kinds of LiF dosemeters. The distribution of the absorbed dose inside a 0.25 and 0.4 mm thick LiF-teflon disc surrounded by polystyrene and irradiated with 60Co, 42 MV roentgen radiation and 39 MeV electrons was measured using 0.01 and 0.02 mm thick Lif-teflon discs. The measurements show that the absorbed dose distribution in the dosemeter depends on the energy of the radiation. When flat dosemeters were used, differences between the signals measured at the two orientations possible during read-out could easily amount to several per cent, and for this reason 0.4 mm and 0.5 mm LiF-Teflon discs were not trusted when the highest accuracy was required. The cavity theory by Burlin does not account for the phenomena caused by differences in electron scattering properties of the dosemeter and the phantom material. Some suggestions are presented for a different cavity theory for flat dosemeters dealing also with these phenomena. It describes the results to about the same degree of approximation as the Burlin theory, and fails to explain the observed energy dependence for electrons.

Photon spectrum and absorbed dose in brain tumor.

PubMed

Vega-Carrillo, Hector Rene; Silva-Sanchez, Angeles; Rivera-Montalvo, Teodoro

2016-11-01

Using Monte Carlo methods a BOMAB phantom inside a treatment hall with a brain tumor nearby the pituitary gland was treated with photons produced by a Varian 6MV linac. The photon spectrum and the absorbed dose were calculated in the tumor, pituitary gland and the head. The treatment beam was collimated to illuminate only the tumor volume; however photons were noticed in the gland. Photon fluence reaching the tumor is and 15.7 times larger than the fluence in the pituitary gland, on the other hand the absorbed dose in the tumor is 37.1 times larger than the dose in the gland because photons that reach the pituitary gland are scattered, by the head and the tumor, through Compton effect. Copyright © 2016 Elsevier Ltd. All rights reserved.

Absorbed dose measurements on external surface of Kosmos-satellites with glass thermoluminescent detectors.

PubMed

Akatov YuA; Arkhangelsky, V V; Kovalev, E E; Spurny, F; Votochkova, I

1989-01-01

In this paper we present absorbed dose measurements with glass thermoluminescent detectors on external surface of satellites of Kosmos-serie flying in 1983-87. Experiments were performed with thermoluminescent aluminophosphate glasses of thicknesses 0.1, 0.3, 0.4, 0.5, and 1 mm. They were exposed in sets of total thickness between 5 and 20 mm, which were protected against sunlight with thin aluminized foils. In all missions, extremely high absorbed dose values were observed in the first layers of detectors, up to the thickness of 0.2 to 0.5 gcm-2. These experimental results confirm that, during flights at 250 to 400 km, doses on the surface of the satellites are very high, due to the low energy component of the proton and electron radiation.

The Effect of Diagnostic Absorbed Doses from 131I on Human Thyrocytes in Vitro.

PubMed

Adamczewski, Zbigniew; Stasiołek, Mariusz; Karwowski, Bolesław; Dedecjus, Marek; Orszulak-Michalak, Daria; Merecz, Anna; Śliwka, Przemysław W; Puła, Bartosz; Lewiński, Andrzej

2015-06-29

Administration of diagnostic activities of 131I, performed in order to detect thyroid remnants after surgery and/or thyroid cancer recurrence/metastases, may lead to reduction of iodine uptake. This phenomenon is called "thyroid stunning". We estimated radiation absorbed dose-dependent changes in genetic material, in particular in sodium iodide symporter (NIS) gene promoter, and NIS protein level in human thyrocytes (HT). We used unmodified HT isolated from patients subjected to thyroidectomy exposed to 131I in culture. The different 131I activities applied were calculated to result in absorbed doses of 5, 10, and 20 Gy. According to flow cytometry analysis and comet assay, 131I did not influence the HT viability in culture. Temporary increase of 8-oxo-dG concentration in HT directly after 24 h (p < 0.05) and increase in the number of AP-sites 72 h after termination of exposition to 20 Gy dose (p < 0.0001) were observed. The signs of dose-dependent DNA damage were not associated with essential changes in the NIS expression on mRNA and protein levels. Our observation constitutes a first attempt to evaluate the effect of the absorbed dose of 131I on HT. The results have not confirmed the theory that the "thyroid stunning" reduces the NIS protein synthesis.

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.

Fast skin dose estimation system for interventional radiology

PubMed Central

Takata, Takeshi; Kotoku, Jun’ichi; Maejima, Hideyuki; Kumagai, Shinobu; Arai, Norikazu; Kobayashi, Takenori; Shiraishi, Kenshiro; Yamamoto, Masayoshi; Kondo, Hiroshi; Furui, Shigeru

2018-01-01

Abstract To minimise the radiation dermatitis related to interventional radiology (IR), rapid and accurate dose estimation has been sought for all procedures. We propose a technique for estimating the patient skin dose rapidly and accurately using Monte Carlo (MC) simulation with a graphical processing unit (GPU, GTX 1080; Nvidia Corp.). The skin dose distribution is simulated based on an individual patient’s computed tomography (CT) dataset for fluoroscopic conditions after the CT dataset has been segmented into air, water and bone based on pixel values. The skin is assumed to be one layer at the outer surface of the body. Fluoroscopic conditions are obtained from a log file of a fluoroscopic examination. Estimating the absorbed skin dose distribution requires calibration of the dose simulated by our system. For this purpose, a linear function was used to approximate the relation between the simulated dose and the measured dose using radiophotoluminescence (RPL) glass dosimeters in a water-equivalent phantom. Differences of maximum skin dose between our system and the Particle and Heavy Ion Transport code System (PHITS) were as high as 6.1%. The relative statistical error (2 σ) for the simulated dose obtained using our system was ≤3.5%. Using a GPU, the simulation on the chest CT dataset aiming at the heart was within 3.49 s on average: the GPU is 122 times faster than a CPU (Core i7–7700K; Intel Corp.). Our system (using the GPU, the log file, and the CT dataset) estimated the skin dose more rapidly and more accurately than conventional methods. PMID:29136194

Fast skin dose estimation system for interventional radiology.

PubMed

Takata, Takeshi; Kotoku, Jun'ichi; Maejima, Hideyuki; Kumagai, Shinobu; Arai, Norikazu; Kobayashi, Takenori; Shiraishi, Kenshiro; Yamamoto, Masayoshi; Kondo, Hiroshi; Furui, Shigeru

2018-03-01

To minimise the radiation dermatitis related to interventional radiology (IR), rapid and accurate dose estimation has been sought for all procedures. We propose a technique for estimating the patient skin dose rapidly and accurately using Monte Carlo (MC) simulation with a graphical processing unit (GPU, GTX 1080; Nvidia Corp.). The skin dose distribution is simulated based on an individual patient's computed tomography (CT) dataset for fluoroscopic conditions after the CT dataset has been segmented into air, water and bone based on pixel values. The skin is assumed to be one layer at the outer surface of the body. Fluoroscopic conditions are obtained from a log file of a fluoroscopic examination. Estimating the absorbed skin dose distribution requires calibration of the dose simulated by our system. For this purpose, a linear function was used to approximate the relation between the simulated dose and the measured dose using radiophotoluminescence (RPL) glass dosimeters in a water-equivalent phantom. Differences of maximum skin dose between our system and the Particle and Heavy Ion Transport code System (PHITS) were as high as 6.1%. The relative statistical error (2 σ) for the simulated dose obtained using our system was ≤3.5%. Using a GPU, the simulation on the chest CT dataset aiming at the heart was within 3.49 s on average: the GPU is 122 times faster than a CPU (Core i7-7700K; Intel Corp.). Our system (using the GPU, the log file, and the CT dataset) estimated the skin dose more rapidly and more accurately than conventional methods.

Absorbed dose rates in tissue from prompt gamma emissions from near-thermal neutron absorption

DOE PAGES

Schwahn, Scott O.

2015-10-01

Prompt gamma emission data from the International Atomic Energy Agency s Prompt Gamma-ray Neutron Activation Analysis database are analyzed to determine the absorbed dose rates in tissue to be expected when natural elements are exposed in a near-thermal neutron environment.

Development of an objective dose distribution analysis method for OSL dating and pilot studies for planetary applications

NASA Astrophysics Data System (ADS)

Lepper, Kenneth Errol

Scope and method of study. Part I: In its simplest expression a luminescence age is the natural absorbed radiation dose (De) divided by the in-situ dose rate. The experimental techniques of Optically Stimulated Luminescence (OSL) dating have evolved to the point were hundreds of Des, and therefore depositional ages can be quickly and conveniently determined for a single sediment sample. The first major objective of this research was to develop an objective analysis method for analyzing dose distribution data and selecting an age-representative dose (Dp). The analytical method was developed based on dose data sets collected from 3 eolian and 3 fluvial sediment samples from Central Oklahoma. Findings and conclusions. Part I: An objective method of presenting the dose distribution data, and a mathematically rigorous means of determining the Dp, as well as a statistically meaningful definition of the uncertainty in Dp have been proposed. The concept of experimental error deconvolution was introduced. In addition a set of distribution shape parameters to facilitate comparison among samples have been defined. These analytical techniques hold the potential to greatly enhance the accuracy and utility of OSL dating for young fluvial sediments. Scope and method of study. Part II: The second major objective of this research was to propose the application of luminescence dating to sediments on Mars. A set of fundamental luminescence dating properties was evaluated for a martian surface materials analog and a polar deposit contextual analog. Findings and conclusions. Part II: The luminescence signals measured from the analogs were found to have a wide dynamic dose response range with no unusual or prohibitive short-term instabilities and were readily reset by exposure to sunlight. These properties form a stable base for continued investigations toward the development of luminescence dating instruments and procedures for Mars.

PLASTIC SCINTILLATOR FOR RADIATION DOSIMETRY.

PubMed

Kim, Yewon; Yoo, Hyunjun; Kim, Chankyu; Lim, Kyung Taek; Moon, Myungkook; Kim, Jongyul; Cho, Gyuseong

2016-09-01

Inorganic scintillators, composed of high-atomic-number materials such as the CsI(Tl) scintillator, are commonly used in commercially available a silicon diode and a scintillator embedded indirect-type electronic personal dosimeters because the light yield of the inorganic scintillator is higher than that of an organic scintillator. However, when it comes to tissue-equivalent dose measurements, a plastic scintillator such as polyvinyl toluene (PVT) is a more appropriate material than an inorganic scintillator because of the mass energy absorption coefficient. To verify the difference in the absorbed doses for each scintillator, absorbed doses from the energy spectrum and the calculated absorbed dose were compared. From the results, the absorbed dose of the plastic scintillator was almost the same as that of the tissue for the overall photon energy. However, in the case of CsI, it was similar to that of the tissue only for a photon energy from 500 to 4000 keV. Thus, the values and tendency of the mass energy absorption coefficient of the PVT are much more similar to those of human tissue than those of the CsI. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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.

SU-E-T-408: Determination of KQ,Q0-Factors From Water and Graphite Calorimetry in a 60 MeV Proton Beam

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

Rossomme, S; Renaud, J; Sarfehnia, A

2014-06-01

Purpose: To reduce the uncertainty of the beam quality correction factor k Q,Q0, for scattered proton beams (SPB). This factor is used in dosimetry protocols, to determine absorbed dose-to-water with ionization chambers. For the Roos plane parallel chambers (RPPICs), the IAEA TRS-398 protocol estimates k Q,Q0-factor to be 1.004(for a beam quality Rres=2 g.cm{sup 2}), with an uncertainty of 2.1%. Methods: A graphite calorimeter (GCal), a water calorimeter (WCal) and RPPICs were exposed, in a single experiment, to a 60 MeV non-modulated SPB. RPPICs were calibrated in terms of absorbed dose-to-water in a 20 MeV electron beam. The calibration coefficientmore » is traceable to NPL's absorbed dose standards. Chamber measurements were corrected for environmental conditions, recombination and polarity. The WCal corrections include heat loss, heat defect and vessel perturbation. The GCal corrections include heat loss and absorbed dose conversion. Except for heat loss correction and its uncertainty in the WCal system, all major corrections were included in the analysis. Other minor corrections, such as beam profile non-uniformity, are still to be evaluated. Experimental k Q,Q0-factors were derived by comparing the results obtained with both calorimeters and ionometry. Results: The absorbed dose-to-water from both calorimeters was found to be within 1.3% with an uncertainty of 1.2%. k Q,Q0-factor for a RPPIC was found to be 0.998 and 1.011, with a standard uncertainty of 1.4% and 0.9% when the dose is based on the GCal and the WCal, respectively. Conclusion: Results suggest the possibility to determine k Q,Q0-values for PPICs in SPB with a lower uncertainty than specified in the TRS-398 thereby helping to reduce uncertainty on absorbed dose-to-water. The agreement between calorimeters confirms the possibility to use GCal or WCal as primary standard in SPB. Because of the dose conversion, the use of GCal may lead to slightly higher uncertainty, but is, at present, considerably easier to operate.« less

Solar particle dose rate buildup and distribution in critical body organs

NASA Technical Reports Server (NTRS)

Atwell, William; Weyland, Mark D.; Simonsen, Lisa C.

1993-01-01

Human body organs have varying degrees of radiosensitivity as evidenced by radioepidemiologic tables. The major critical organs for both the male and female that have been identified include the lung, thyroid, stomach, and breast (female). Using computerized anatomical models of the 50th percentile United States Air Force male and female, we present the self-shielding effects of these various body organs and how the shielding effects change as the location (dose point) in the body varies. Several major solar proton events from previous solar cycles and several events from the current 22nd solar cycle have been analyzed. The solar particle event rise time, peak intensity, and decay time vary considerably from event to event. Absorbed dose and dose equivalent rate calculations and organ risk assessment data are presented for each critical body organ. These data are compared with the current NASA astronaut dose limits as recommended by the National Council on Radiation Protection and Measurements.

Validation of a MOSFET dosemeter system for determining the absorbed and effective radiation doses in diagnostic radiology.

PubMed

Manninen, A-L; Kotiaho, A; Nikkinen, J; Nieminen, M T

2015-04-01

This study aimed to validate a MOSFET dosemeter system for determining absorbed and effective doses (EDs) in the dose and energy range used in diagnostic radiology. Energy dependence, dose linearity and repeatability of the dosemeter were examined. The absorbed doses (ADs) were compared at anterior-posterior projection and the EDs were determined at posterior-anterior, anterior-posterior and lateral projections of thoracic imaging using an anthropomorphic phantom. The radiation exposures were made using digital radiography systems. This study revealed that the MOSFET system with high sensitivity bias supply set-up is sufficiently accurate for AD and ED determination. The dosemeter is recommended to be calibrated for energies <60 and >80 kVp. The entrance skin dose level should be at least 5 mGy to minimise the deviation of the individual dosemeter dose. For ED determination, dosemeters should be implanted perpendicular to the surface of the phantom to prevent the angular dependence error. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Developability assessment of clinical drug products with maximum absorbable doses.

PubMed

Ding, Xuan; Rose, John P; Van Gelder, Jan

2012-05-10

Maximum absorbable dose refers to the maximum amount of an orally administered drug that can be absorbed in the gastrointestinal tract. Maximum absorbable dose, or D(abs), has proved to be an important parameter for quantifying the absorption potential of drug candidates. The purpose of this work is to validate the use of D(abs) in a developability assessment context, and to establish appropriate protocol and interpretation criteria for this application. Three methods for calculating D(abs) were compared by assessing how well the methods predicted the absorption limit for a set of real clinical candidates. D(abs) was calculated for these clinical candidates by means of a simple equation and two computer simulation programs, GastroPlus and an program developed at Eli Lilly and Company. Results from single dose escalation studies in Phase I clinical trials were analyzed to identify the maximum absorbable doses for these compounds. Compared to the clinical results, the equation and both simulation programs provide conservative estimates of D(abs), but in general D(abs) from the computer simulations are more accurate, which may find obvious advantage for the simulations in developability assessment. Computer simulations also revealed the complex behavior associated with absorption saturation and suggested in most cases that the D(abs) limit is not likely to be achieved in a typical clinical dose range. On the basis of the validation findings, an approach is proposed for assessing absorption potential, and best practices are discussed for the use of D(abs) estimates to inform clinical formulation development strategies. Copyright © 2012 Elsevier B.V. All rights reserved.

Prediction of Therapy Tumor-Absorbed Dose Estimates in I-131 Radioimmunotherapy Using Tracer Data Via a Mixed-Model Fit to Time Activity

PubMed Central

Koral, Kenneth F.; Avram, Anca M.; Kaminski, Mark S.; Dewaraja, Yuni K.

2012-01-01

Abstract Background For individualized treatment planning in radioimmunotherapy (RIT), correlations must be established between tracer-predicted and therapy-delivered absorbed doses. The focus of this work was to investigate this correlation for tumors. Methods The study analyzed 57 tumors in 19 follicular lymphoma patients treated with I-131 tositumomab and imaged with SPECT/CT multiple times after tracer and therapy administrations. Instead of the typical least-squares fit to a single tumor's measured time-activity data, estimation was accomplished via a biexponential mixed model in which the curves from multiple subjects were jointly estimated. The tumor-absorbed dose estimates were determined by patient-specific Monte Carlo calculation. Results The mixed model gave realistic tumor time-activity fits that showed the expected uptake and clearance phases even with noisy data or missing time points. Correlation between tracer and therapy tumor-residence times (r=0.98; p<0.0001) and correlation between tracer-predicted and therapy-delivered mean tumor-absorbed doses (r=0.86; p<0.0001) were very high. The predicted and delivered absorbed doses were within±25% (or within±75 cGy) for 80% of tumors. Conclusions The mixed-model approach is feasible for fitting tumor time-activity data in RIT treatment planning when individual least-squares fitting is not possible due to inadequate sampling points. The good correlation between predicted and delivered tumor doses demonstrates the potential of using a pretherapy tracer study for tumor dosimetry-based treatment planning in RIT. PMID:22947086

Absolute Bioavailability of Osimertinib in Healthy Adults.

PubMed

Vishwanathan, Karthick; So, Karen; Thomas, Karen; Bramley, Alex; English, Stephen; Collier, Jo

2018-04-23

Osimertinib is a third-generation, central nervous system-active, epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKI) selective for EGFR-TKI sensitizing and T790M resistance mutations. This phase 1, open-label study (NCT02491944) investigated absolute bioavailability and pharmacokinetics (PK) of oral and intravenous (IV) osimertinib. Ten healthy subjects (21-61 years) received a single oral 80-mg dose concomitantly with a 100 μg (containing 1 μCi) IV microtracer dose of [ 14 C]osimertinib. Oral and IV PK were determined simultaneously for osimertinib and its active metabolites, AZ5104 and AZ7550. High-performance liquid chromatography and accelerator mass spectrometry were used to characterize IV dose PK. Geometric mean absolute oral bioavailability of osimertinib was 69.8% (90% confidence interval, 66.7, 72.9). Oral osimertinib was slowly absorbed (median time to maximum plasma concentration [t max ] 7.0 hours). Following t max , plasma concentrations fell in an apparent monophasic manner. IV clearance and volume of distribution were 16.8 L/h and 1285 L, respectively. Arithmetic mean elimination half-life estimates were 59.7, 52.6, and 72.6 hours for osimertinib, AZ5104, and AZ7550, respectively (oral dosing), and 54.9, 68.4, and 99.7 hours for [ 14 C]osimertinib, [ 14 C]AZ5104, and [ 14 C]AZ7550, respectively (IV dosing). Oral osimertinib was well absorbed. Simultaneous IV and oral PK analysis proved useful for complete understanding of osimertinib PK and showed that the first-pass effect was minimal for osimertinib. © 2018, The American College of Clinical Pharmacology.

SU-F-18C-09: Assessment of OSL Dosimeter Technology in the Validation of a Monte Carlo Radiation Transport Code for CT Dosimetry

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

Carver, D; Kost, S; Pickens, D

Purpose: To assess the utility of optically stimulated luminescent (OSL) dosimeter technology in calibrating and validating a Monte Carlo radiation transport code for computed tomography (CT). Methods: Exposure data were taken using both a standard CT 100-mm pencil ionization chamber and a series of 150-mm OSL CT dosimeters. Measurements were made at system isocenter in air as well as in standard 16-cm (head) and 32-cm (body) CTDI phantoms at isocenter and at the 12 o'clock positions. Scans were performed on a Philips Brilliance 64 CT scanner for 100 and 120 kVp at 300 mAs with a nominal beam width ofmore » 40 mm. A radiation transport code to simulate the CT scanner conditions was developed using the GEANT4 physics toolkit. The imaging geometry and associated parameters were simulated for each ionization chamber and phantom combination. Simulated absorbed doses were compared to both CTDI{sub 100} values determined from the ion chamber and to CTDI{sub 100} values reported from the OSLs. The dose profiles from each simulation were also compared to the physical OSL dose profiles. Results: CTDI{sub 100} values reported by the ion chamber and OSLs are generally in good agreement (average percent difference of 9%), and provide a suitable way to calibrate doses obtained from simulation to real absorbed doses. Simulated and real CTDI{sub 100} values agree to within 10% or less, and the simulated dose profiles also predict the physical profiles reported by the OSLs. Conclusion: Ionization chambers are generally considered the standard for absolute dose measurements. However, OSL dosimeters may also serve as a useful tool with the significant benefit of also assessing the radiation dose profile. This may offer an advantage to those developing simulations for assessing radiation dosimetry such as verification of spatial dose distribution and beam width.« less

Estimated human absorbed dose of ¹⁷⁷Lu-BPAMD based on mice data: Comparison with ¹⁷⁷Lu-EDTMP.

PubMed

Yousefnia, Hassan; Zolghadri, Samaneh; Shanehsazzadeh, Saeed

2015-10-01

In this work, the absorbed dose of human organs for (177)Lu-BPAMD was evaluated based on biodistribution studies into the Syrian mice by RADAR method and was compared with (177)Lu-EDTMP as the only clinically used Lu-177 bone-seeking agent. The highest absorbed dose for both (177)Lu-BPAMD and (177)Lu-EDTMP is observed on the bone surface with 8.007 and 4.802 mSv/MBq. Generally, (177)Lu-BPAMD has considerable characteristics compared with (177)Lu-EDTMP and can be considered as a promising agent for the bone pain palliation therapy. Copyright © 2015 Elsevier Ltd. All rights reserved.

Assessment of an organ‐based tube current modulation in thoracic computed tomography

PubMed Central

Sugai, Mai; Toyoda, Asami; Koshida, Haruka; Sakuta, Keita; Takata, Tadanori; Koshida, Kichiro; Iida, Hiroji; Matsui, Osamu

2012-01-01

Recently, specific computed tomography (CT) scanners have been equipped with organ‐based tube current modulation (TCM) technology. It is possible that organ‐based TCM will replace the conventional dose‐reduction technique of reducing the effective milliampere‐second. The aim of this study was to determine if organ‐based TCM could reduce radiation exposure to the breasts without compromising the image uniformity and beam hardening effect in thoracic CT examinations. Breast and skin radiation doses and the absorbed radiation dose distribution within a single section were measured with an anthropomorphic phantom and radiophotoluminescent glass dosimeters using four approaches to thoracic CT (reference, organ‐based TCM, copper shielding, and the combination of the above two techniques, hereafter referred to as the combination technique). The CT value and noise level were measured using the same calibration phantom. Organ‐based TCM and copper shielding reduced radiation doses to the breast by 23.7% and 21.8%, respectively. However, the CT value increased, especially in the anterior region, using copper shielding. In contrast, the CT value and noise level barely increased using organ‐based TCM. The combination technique reduced the radiation dose to the breast by 38.2%, but greatly increased the absorbed radiation dose from the central to the posterior regions. Moreover, the CT value increased in the anterior region and the noise level increased by more than 10% in the entire region. Therefore, organ‐based TCM can reduce radiation doses to breasts with only small increases in noise levels, making it preferable for specific groups of patients, such as children and young women. PACS numbers: 87.53.Bn; 87.57.Q‐; 87.57.qp PMID:22402390

Multiparametric Determination of Radiation Risk

NASA Technical Reports Server (NTRS)

Richmond, Robert C.

2003-01-01

Predicting risk of human cancer following exposure to ionizing space radiation is challenging in part because of uncertainties of low-dose distribution amongst cells, of unknown potentially synergistic effects of microgravity upon cellular protein-expression, and of processing dose-related damage within cells to produce rare and late-appearing malignant transformation, degrade the confidence of cancer risk-estimates. The NASA- specific responsibility to estimate the risks of radiogenic cancer in a limited number of astronauts is not amenable to epidemiologic study, thereby increasing this challenge. Developing adequately sensitive cellular biodosimeters that simultaneously report 1) the quantity of absorbed close after exposure to ionizing radiation, 2) the quality of radiation delivering that dose, and 3) the risk of developing malignant transformation by the cells absorbing that dose could be useful for resolving these challenges. Use of a multiparametric cellular biodosimeter is suggested using analyses of gene-expression and protein-expression whereby large datasets of cellular response to radiation-induced damage are obtained and analyzed for expression-profiles correlated with established end points and molecular markers predictive for cancer-risk. Analytical techniques of genomics and proteomics may be used to establish dose-dependency of multiple gene- and protein- expressions resulting from radiation-induced cellular damage. Furthermore, gene- and protein-expression from cells in microgravity are known to be altered relative to cells grown on the ground at 1g. Therefore, hypotheses are proposed that 1) macromolecular expression caused by radiation-induced damage in cells in microgravity may be different than on the ground, and 2) different patterns of macromolecular expression in microgravity may alter human radiogenic cancer risk relative to radiation exposure on Earth. A new paradigm is accordingly suggested as a national database wherein genomic and proteomic datasets are registered and interrogated in order to provide statistically significant dose-dependent risk estimation of radiogenic cancer in astronauts.

Estimation of dose delivered to accelerator devices from stripping of 18.5 MeV/n 238U ions using the FLUKA code

NASA Astrophysics Data System (ADS)

Oranj, Leila Mokhtari; Lee, Hee-Seock; Leitner, Mario Santana

2017-12-01

In Korea, a heavy ion accelerator facility (RAON) has been designed for production of rare isotopes. The 90° bending section of this accelerator includes a 1.3- μm-carbon stripper followed by two dipole magnets and other devices. An incident beam is 18.5 MeV/n 238U33+,34+ ions passing through the carbon stripper at the beginning of the section. The two dipoles are tuned to transport 238U ions with specific charge states of 77+, 78+, 79+, 80+ and 81+. Then other ions will be deflected at the bends and cause beam losses. These beam losses are a concern to the devices of transport/beam line. The absorbed dose in devices and prompt dose in the tunnel were calculated using the FLUKA code in order to estimate radiation damage of such devices located at the 90° bending section and for the radiation protection. A novel method to transport multi-charged 238U ions beam was applied in the FLUKA code by using charge distribution of 238U ions after the stripper obtained from LISE++ code. The calculated results showed that the absorbed dose in the devices is influenced by the geometrical arrangement. The maximum dose was observed at the coils of first, second, fourth and fifth quadruples placed after first dipole magnet. The integrated doses for 30 years of operation with 9.5 p μA 238U ions were about 2 MGy for those quadrupoles. In conclusion, the protection of devices particularly, quadruples would be necessary to reduce the damage to devices. Moreover, results showed that the prompt radiation penetrated within the first 60 - 120 cm of concrete.

Hepatic radioembolization with yttrium-90 containing glass microspheres: Preliminary results and clinical follow-up

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

Andrews, J.C.; Walker, S.C.; Ackermann, R.J.

1994-10-01

The treatment of hepatic tumors remains unsatisfactory. These lesions receive most of their blood supply from the hepatic artery, therefore the hepatic artery administration of beta-emitting particulate radiopharmaceuticals is an attractive approach to deliver therapeutic irradiation to the liver and differentially to tumors within the liver. A Phase 1 dose escalation study of the hepatic tolerance to radiation delivered by {sup 90}Y containing glass microspheres was carried out in 24 patients with hepatic malignancy. Doses of {sup 90}Y microspheres to achieve an estimated whole-liver nominal absorbed radiation dose of 5000 cGy (two patients), 7500cGy (six patients), 10,000 cGy (seven patients),more » 12,500 cGy (six patients), and 15,000 cGy (three patients) were administered via the hepatic artery. The administered nominal absorbed radiation dose (NARD) was estimated based on liver volume determined from CT scans and the assumption of uniform distribution of microspheres throughout the liver. No hematologic, hepatic or pulmonary toxicity was encountered in the dose range examined during a mean follow-up period of up to 53 mo. Reversible gastritis or duodenitis was encountered in four patients without imaging or biopsy evidence for extra-hepatic deposition of microspheres. Response data, based on CT scans obtained 16 wk after treatment, showed progressive disease in eight patients, stable disease in seven patients, minimal response in four patients and partial response in five patients. Subsequent follow-up revealed three long-term survivors at 204, 216 and 228 wk. These preliminary data demonstrates that in the examined dose range, radiation may be safely delivered to liver tumors by means of {sup 90}Y glass microspheres with encouraging response data. 39 refs., 3 figs., 1 tab.« less

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.

A Geant4 model of backscatter security imaging systems

NASA Astrophysics Data System (ADS)

Leboffe, Eric Matthew

The operating characteristics of x ray security scanner systems that utilize backscatter signal in order to distinguish person borne threats have never been made fully available to the general public. By designing a model using Geant4, studies can be performed which will shed light on systems such as security scanners and allow for analysis of the performance and safety of the system without access to any system data. Despite the fact that the systems are no longer in use at airports in the United States, the ability to design and validate detector models and phenomena is an important capability that can be applied to many current real world applications. The model presented provides estimates for absorbed dose, effective dose and dose depth distribution that are comparable to previously published work and explores imaging capabilities for the system embodiment modeled.

Measurement of absorbed dose with a bone-equivalent extrapolation chamber.

PubMed

DeBlois, François; Abdel-Rahman, Wamied; Seuntjens, Jan P; Podgorsak, Ervin B

2002-03-01

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water and bone-equivalent material was used for determining absorbed dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain absorbed dose in bone for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC by 0.7% to approximately 2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dose measurement in the Solid Water PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). In conjunction with appropriate correction factors determined with Monte Carlo techniques, the uncalibrated hybrid PEEC can be used for measuring absorbed dose in bone material to within 2% for high-energy photon and electron beams.

Neutron fluence-to-dose conversion coefficients for embryo and fetus.

PubMed

Chen, Jing; Meyerhof, Dorothy; Vlahovich, Slavica

2004-01-01

A problem of concern in radiation protection is the exposure of pregnant women to ionising radiation, because of the high radiosensitivity of the embryo and fetus. External neutron exposure is of concern when pregnant women travel by aeroplane. Dose assessments for neutrons frequently rely on fluence-to-dose conversion coefficients. While neutron fluence-to-dose conversion coefficients for adults are recommended in International Commission on Radiological Protection publications and International Commission on Radiological Units and Measurements reports, conversion coefficients for embryos and fetuses are not given in the publications. This study undertakes Monte Carlo calculations to determine the mean absorbed doses to the embryo and fetus when the mother is exposed to neutron fields. A new set of mathematical models for the embryo and fetus has been developed at Health Canada and is used together with mathematical phantoms of a pregnant female developed at Oak Ridge National Laboratory. Monoenergetic neutrons from 1 eV to 10 MeV are considered in this study. The irradiation geometries include antero-posterior (AP), postero-anterior (PA), lateral (LAT), rotational (ROT) and isotropic (ISO) geometries. At each of these standard irradiation geometries, absorbed doses to the fetal brain and body are calculated; for the embryo at 8 weeks and the fetus at 3, 6 or 9 months. Neutron fluence-to-absorbed dose conversion coefficients are derived for the four age groups. Neutron fluence-to-equivalent dose conversion coefficients are given for the AP irradiations which yield the highest radiation dose to the fetal body in the neutron energy range considered here. The results indicate that for neutrons <10 MeV more protection should be given to pregnant women in the first trimester due to the higher absorbed dose per unit neutron fluence to the fetus.

Paired organs--Should they be treated jointly or separately in internal dosimetry?

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

Parach, Ali-Asghar; Rajabi, Hossein; Askari, Mohammad-Ali

2011-10-15

Purpose: Size, shape, and the position of paired organs are different in abdomen. However, the counterpart organs are conventionally treated jointly together in internal dosimetry. This study was performed to quantify the difference of specific absorbed fraction of organs in considering paired organs jointly like single organs or as two separate organs. Methods: Zubal phantom and GATE Monte Carlo package were used to calculate the SAF for the self-absorption and cross-irradiation of the lungs, kidneys, adrenal glands (paired organs), liver, spleen, stomach, and pancreas (single organs). The activity was assumed uniformly distributed in the organs, and simulation was performed formore » monoenergetic photons of 10, 50, 100, 500, 1000 keV and mono-energetic electrons of 350, 500, 690, 935, 1200 keV. Results: The results demonstrated that self-absorption of left and right counterpart organs may be different depending upon the differences in their masses. The cross-irradiations between left-to-right and right-to-left counterpart organs are always equal irrespective of difference in their masses. Cross-irradiation from the left and right counterpart organs to other organs are different (4-24 times in Zubal phantom) depending on the photon energy and organs. The irradiation from a single source organ to the left and right counterpart paired organs is always different irrespective of activity concentration. Conclusions: Left and right counterpart organs always receive different absorbed doses from target organs and deliver different absorbed doses to target organs. Therefore, in application of radiopharmaceuticals in which the dose to the organs plays a role, counterpart organs should be treated separately as two separate organs.« less

Dosimetric and microdosimetric analyses for blood exposed to reactor-derived thermal neutrons.

PubMed

Ali, F; Atanackovic, J; Boyer, C; Festarini, A; Kildea, J; Paterson, L C; Rogge, R; Stuart, M; Richardson, R B

2018-06-06

Thermal neutrons are found in reactor, radiotherapy, aircraft, and space environments. The purpose of this study was to characterise the dosimetry and microdosimetry of thermal neutron exposures, using three simulation codes, as a precursor to quantitative radiobiological studies using blood samples. An irradiation line was designed employing a pyrolytic graphite crystal or-alternatively-a super mirror to expose blood samples to thermal neutrons from the National Research Universal reactor to determine radiobiological parameters. The crystal was used when assessing the relative biological effectiveness for dicentric chromosome aberrations, and other biomarkers, in lymphocytes over a low absorbed dose range of 1.2-14 mGy. Higher exposures using a super mirror will allow the additional quantification of mitochondrial responses. The physical size of the thermal neutron fields and their respective wavelength distribution was determined using the McStas Monte Carlo code. Spinning the blood samples produced a spatially uniform absorbed dose as determined from Monte Carlo N-Particle version 6 simulations. The major part (71%) of the total absorbed dose to blood was determined to be from the 14 N(n,p) 14 C reaction and the remainder from the 1 H(n,γ) 2 H reaction. Previous radiobiological experiments at Canadian Nuclear Laboratories involving thermal neutron irradiation of blood yielded a relative biological effectiveness of 26 ± 7. Using the Particle and Heavy Ion Transport Code System, a similar value of ∼19 for the quality factor of thermal neutrons initiating the 14 N(n,p) 14 C reaction in soft tissue was determined by microdosimetric simulations. This calculated quality factor is of similar high value to the experimentally-derived relative biological effectiveness, and indicates the potential of thermal neutrons to induce deleterious health effects in superficial organs such as cataracts of the eye lens.

Absorbed radiation dosimetry of the D3-specific PET radioligand [18F]FluorTriopride estimated using rodent and nonhuman primate.

PubMed

Laforest, Richard; Karimi, Morvarid; Moerlein, Stephen M; Xu, Jinbin; Flores, Hubert P; Bognar, Christopher; Li, Aixiao; Mach, Robert H; Perlmutter, Joel S; Tu, Zhude

2016-01-01

[ 18 F]FluorTriopride ([ 18 F]FTP) is a dopamine D 3 -receptor preferring radioligand with potential for investigation of neuropsychiatric disorders including Parkinson disease, dystonia and schizophrenia. Here we estimate human radiation dosimetry for [ 18 F]FTP based on the ex-vivo biodistribution in rodents and in vivo distribution in nonhuman primates. Biodistribution data were generated using male and female Sprague-Dawley rats injected with ~370 KBq of [ 18 F]FTP and euthanized at 5, 30, 60, 120, and 240 min. Organs of interest were dissected, weighed and assayed for radioactivity content. PET imaging studies were performed in two male and one female macaque fascicularis administered 143-190 MBq of [ 18 F]FTP and scanned whole-body in sequential sections. Organ residence times were calculated based on organ time activity curves (TAC) created from regions of Interest. OLINDA/EXM 1.1 was used to estimate human radiation dosimetry based on scaled organ residence times. In the rodent, the highest absorbed radiation dose was the upper large intestines (0.32-0.49 mGy/MBq), with an effective dose of 0.07 mSv/MBq in males and 0.1 mSv/MBq in females. For the nonhuman primate, however, the gallbladder wall was the critical organ (1.81 mGy/MBq), and the effective dose was 0.02 mSv/MBq. The species discrepancy in dosimetry estimates for [ 18 F]FTP based on rat and primate data can be attributed to the slower transit of tracer through the hepatobiliary track of the primate compared to the rat, which lacks a gallbladder. Out findings demonstrate that the nonhuman primate model is more appropriate model for estimating human absorbed radiation dosimetry when hepatobiliary excretion plays a major role in radiotracer elimination.

Organ dose measurement using Optically Stimulated Luminescence Detector (OSLD) during CT examination

NASA Astrophysics Data System (ADS)

Yusuf, Muhammad; Alothmany, Nazeeh; Abdulrahman Kinsara, Abdulraheem

2017-10-01

This study provides detailed information regarding the imaging doses to patient radiosensitive organs from a kilovoltage computed tomography (CT) scan procedure using OSLD. The study reports discrepancies between the measured dose and the calculated dose from the ImPACT scan, as well as a comparison with the dose from a chest X-ray radiography procedure. OSLDs were inserted in several organs, including the brain, eyes, thyroid, lung, heart, spinal cord, breast, spleen, stomach, liver and ovaries, of the RANDO phantom. Standard clinical scanning protocols were used for each individual site, including the brain, thyroid, lung, breast, stomach, liver and ovaries. The measured absorbed doses were then compared with the simulated dose obtained from the ImPACT scan. Additionally, the equivalent doses for each organ were calculated and compared with the dose from a chest X-ray radiography procedure. Absorbed organ doses measured by OSLD in the RANDO phantom of up to 17 mGy depend on the organ scanned and the scanning protocols used. A maximum 9.82% difference was observed between the target organ dose measured by OSLD and the results from the ImPACT scan. The maximum equivalent organ dose measured during this experiment was equal to 99.899 times the equivalent dose from a chest X-ray radiography procedure. The discrepancies between the measured dose with the OSLD and the calculated dose from the ImPACT scan were within 10%. This report recommends the use of OSLD for measuring the absorbed organ dose during CT examination.

Neutron dose estimation in a zero power nuclear reactor

NASA Astrophysics Data System (ADS)

Triviño, S.; Vedelago, J.; Cantargi, F.; Keil, W.; Figueroa, R.; Mattea, F.; Chautemps, A.; Santibañez, M.; Valente, M.

2016-10-01

This work presents the characterization and contribution of neutron and gamma components to the absorbed dose in a zero power nuclear reactor. A dosimetric method based on Fricke gel was implemented to evaluate the separation between dose components in the mixed field. The validation of this proposed method was performed by means of direct measurements of neutron flux in different positions using Au and Mg-Ni activation foils. Monte Carlo simulations were conversely performed using the MCNP main code with a dedicated subroutine to incorporate the exact complete geometry of the nuclear reactor facility. Once nuclear fuel elements were defined, the simulations computed the different contributions to the absorbed dose in specific positions inside the core. Thermal/epithermal contributions of absorbed dose were assessed by means of Fricke gel dosimetry using different isotopic compositions aimed at modifying the sensitivity of the dosimeter for specific dose components. Clear distinctions between gamma and neutron capture dose were obtained. Both Monte Carlo simulations and experimental results provided reliable estimations about neutron flux rate as well as dose rate during the reactor operation. Simulations and experimental results are in good agreement in every positions measured and simulated in the core.

Radiation exposure from work-related medical X-rays at the Portsmouth Naval Shipyard.

PubMed

Daniels, Robert D; Kubale, Travis L; Spitz, Henry B

2005-03-01

Previous analyses suggest that worker radiation dose may be significantly increased by routine occupational X-ray examinations. Medical exposures are investigated for 570 civilian workers employed at the Portsmouth Naval Shipyard (PNS) at Kittery, Maine. The research objective was to determine the radiation exposure contribution of work-related chest X-rays (WRX) relative to conventional workplace radiation sources. Methods were developed to estimate absorbed doses to the active (hematopoietic) bone marrow from X-ray examinations and workplace exposures using data extracted from worker dosimetry records (8,468) and health records (2,453). Dose distributions were examined for radiation and non-radiation workers. Photofluorographic chest examinations resulted in 82% of the dose from medical sources. Radiation workers received 26% of their collective dose from WRX and received 66% more WRX exposure than non-radiation workers. WRX can result in a significant fraction of the total dose, especially for radiation workers who were more likely to be subjected to routine medical monitoring. Omission of WRX from the total dose is a likely source of bias that can lead to dose category misclassification and may skew the epidemiologic dose-response assessment for cancers induced by the workplace.

Comparative study of nuclear magnetic resonance and UV-visible spectroscopy dose-response of polymer gel based on N-(Isobutoxymethyl) acrylamide

NASA Astrophysics Data System (ADS)

Lotfy, S.; Basfar, A. A.; Moftah, B.; Al-Moussa, A. A.

2017-12-01

A comparative study of nuclear magnetic resonance and UV-visible spectroscopy of dose-response for polymer gel dosimeters was performed. Dosimeters were prepared using N-(Isobutoxymethyl) acrylamide (NIBMA) as a new monomer via radiation induced polymerization for use in radiotherapy planning. The prepared dosimeters were irradiated with doses up to 30 Gy at a constant dose rate of 600 MU/min. Using a medical linear accelerator at irradiation energies of 6, 10 and 18 MV photon beam. The nuclear magnetic resonance (NMR), via spin-spin relaxation rate (R2) for water proton surrounding the polymer formulation and UV-Visible spectroscopy, via the optical absorbance measurements of irradiated dosimeters at selected wavelengths of 500 nm, was used to investigate the dose response of NIBMAGAT gel dosimeters. Scavenge of oxygen was done using tetrakis (hydroxymethyl) phosphonium chloride (THPC). The THPC optimum concentration in the dosimeters formulations were 5 and 10 mM for the NMR and optical absorbance measurements respectively. The quantitative investigation of the dosimeters components reveals the selective formulations based on 4% w/w gelatin, 1% w/w NIBMA, 3% w/w BisAAm, 5 or 10 mM THPC and 17% w/w glycerol which significantly increase the dosimeters dose response. The prepared dosimeters were found to be dose rate and photon beam irradiation energy independent. The stability study shows no change in the relaxation rate or in the optical absorbance of the gel dosimeters up to 8 days post-irradiation. The prepared polymer gel dosimeters at the energies of 6, 10 and 18 MV photon beam irradiation in the range of 1-30 Gy have the linearity of the dose response function in the case of R2 is better than in the case of absorbance measurements; correlation coefficient (r2) equals 0.995 and 0.991, respectively. Dose sensitivity, R2 of NIBMAGAT dosimeters (0.0775 s-1 Gy-1). The absorption band intensity increases linearly with a dose sensitivity of 0.016 cm-1 Gy-1. The detection limit of the present dosimeter analyzed by R2 and absorbance measurements is 1 Gy and 2 Gy respectively. The overall uncertainty measurements of dose approve that by using the absorbance measurements the gel is not useful as a dosimeter like as R2 measurements. It could be a new composition of dosimeters successfully utilized for MRI (Magnetic Resonance Imaging) for radiotherapy treatment planning.

Pharmacokinetics of plasma enfuvirtide after subcutaneous administration to patients with human immunodeficiency virus: Inverse Gaussian density absorption and 2-compartment disposition.

PubMed

Zhang, Xiaoping; Nieforth, Keith; Lang, Jean-Marie; Rouzier-Panis, Regine; Reynes, Jacques; Dorr, Albert; Kolis, Stanley; Stiles, Mark R; Kinchelow, Tosca; Patel, Indravadan H

2002-07-01

Enfuvirtide (T-20) is the first of a novel class of human immunodeficiency virus (HIV) drugs that block gp41-mediated viral fusion to host cells. The objectives of this study were to develop a structural pharmacokinetic model that would adequately characterize the absorption and disposition of enfuvirtide pharmacokinetics after both intravenous and subcutaneous administration and to evaluate the dose proportionality of enfuvirtide pharmacokinetic parameters at a subcutaneous dose higher than that currently used in phase III studies. Twelve patients with HIV infection received 4 single doses of enfuvirtide separated by a 1-week washout period in an open-label, randomized, 4-way crossover fashion. The doses studied were 90 mg (intravenous) and 45 mg, 90 mg, and 180 mg (subcutaneous). Serial blood samples were collected up to 48 hours after each dose. Plasma enfuvirtide concentrations were measured with use of a validated liquid chromatography-tandem mass spectrometry method. Enfuvirtide plasma concentration-time data after subcutaneous administration were well described by an inverse Gaussian density function-input model linked to a 2-compartment open distribution model with first-order elimination from the central compartment. The model-derived mean pharmacokinetic parameters (+/-SD) were volume of distribution of the central compartment (3.8 +/- 0.8 L), volume of distribution of the peripheral compartment (1.7 +/- 0.6 L), total clearance (1.44 +/- 0.30 L/h), intercompartmental distribution (2.3 +/- 1.1 L/h), bioavailability (89% +/- 11%), and mean absorption time (7.26 hours, 8.65 hours, and 9.79 hours for the 45-mg, 90-mg, and 180-mg dose groups, respectively). The terminal half-life increased from 3.46 to 4.35 hours for the subcutaneous dose range from 45 to 180 mg. An inverse Gaussian density function-input model linked to a 2-compartment open distribution model with first-order elimination from the central compartment was appropriate to describe complex absorption and disposition kinetics of enfuvirtide plasma concentration-time data after subcutaneous administration to patients with HIV infection. Enfuvirtide was nearly completely absorbed from subcutaneous depot, and pharmacokinetic parameters were linear up to a dose of 180 mg in this study.

Absorbed dose in AgBr in direct film for photon energies ( < 150 keV): relation to optical density. Theoretical calculation and experimental evaluation.

PubMed

Helmrot, E; Alm Carlsson, G

1996-01-01

In the radiological process it is necessary to develop tools so as to explore how X-rays can be used in the most effective way. Evaluation of models to derive measures of image quality and risk-related parameters is one possibility of getting such a tool. Modelling the image receptor, an important part of the imaging chain, is then required. The aim of this work was to find convenient and accurate ways of describing the blackening of direct dental films by X-rays. Since the beginning of the 20th century, the relation between optical density and photon interactions in the silver bromide in X-ray films has been investigated by many authors. The first attempts used simple quantum theories with no consideration of underlying physical interaction processes. The theories were gradually made more realistic by the introduction of dosimetric concepts and cavity theory. A review of cavity theories for calculating the mean absorbed dose in the AgBr grains of the film emulsion is given in this work. The cavity theories of GREENING (15) and SPIERS-CHARLTON (37) were selected for calculating the mean absorbed dose in the AgBr grains relative to the air collision kerma (Kc,air) of the incident photons of Ultra-speed and Ektaspeed (intraoral) films using up-to-date values of interaction coefficients. GREENING'S theory is a multi-grain theory and the results depend on the relative amounts of silver bromide and gelatine in the emulsion layer. In the single grain theory of SPIERS-CHARLTON, the shape and size of the silver bromide grain are important. Calculations of absorbed dose in the silver bromide were compared with measurements of optical densities in Ultra-speed and Ektaspeed films for a broad range (25-145 kV) of X-ray energy. The calculated absorbed dose values were appropriately averaged over the complete photon energy spectrum, which was determined experimentally using a Compton spectrometer. For the whole range of tube potentials used, the measured optical densities of the films were found to be proportional to the mean absorbed dose in the AgBr grains calculated according to GREENING'S theory. They were also found to be proportional to the collision kerma in silver bromide (Kc,AgBr) indicating proportionality between Kc,AgBr and the mean absorbed dose in silver bromide. While GREENING'S theory shows that the quotient of the mean absorbed dose in silver bromide and Kc,AgBr varies with photon energy, this is not apparent when averaged over the broad (diagnostic) X-ray energy spectra used here. Alternatively, proportionality between Kc,AgBr and the mean absorbed dose in silver bromide can be interpreted as resulting from a combination of the SPIERS-CHARLTON theory, valid at low photon energies ( < 30 keV) and GREENING'S theory, which is strictly valid at energies above 50 keV. This study shows that the blackening of non-screen films can be related directly to the energy absorbed in the AgBr grains of the emulsion layer and that, for the purpose of modelling the imaging chain in intraoral radiography, film response can be represented by Kc,AgBr (at the position of the film) independent of photon energy. The importance of taking the complete X-ray energy spectrum into full account in deriving Kc,AgBr is clearly demonstrated, showing that the concept of effective energy must be used with care.

Pharmacokinetics, tissue distribution, and excretion of zinc oxide nanoparticles

PubMed Central

Baek, Miri; Chung, Hae-Eun; Yu, Jin; Lee, Jung-A; Kim, Tae-Hyun; Oh, Jae-Min; Lee, Won-Jae; Paek, Seung-Min; Lee, Jong Kwon; Jeong, Jayoung; Choy, Jin-Ho; Choi, Soo-Jin

2012-01-01

Background This study explored the pharmacokinetics, tissue distribution, and excretion profile of zinc oxide (ZnO) nanoparticles with respect to their particle size in rats. Methods Two ZnO nanoparticles of different size (20 nm and 70 nm) were orally administered to male and female rats, respectively. The area under the plasma concentration-time curve, tissue distribution, excretion, and the fate of the nanoparticles in organs were analyzed. Results The plasma zinc concentration of both sizes of ZnO nanoparticles increased during the 24 hours after administration in a dose-dependent manner. They were mainly distributed to organs such as the liver, lung, and kidney within 72 hours without any significant difference being found according to particle size or rat gender. Elimination kinetics showed that a small amount of ZnO nanoparticles was excreted via the urine, while most of nanoparticles were excreted via the feces. Transmission electron microscopy and x-ray absorption spectroscopy studies in the tissues showed no noticeable ZnO nanoparticles, while new Zn-S bonds were observed in tissues. Conclusion ZnO nanoparticles of different size were not easily absorbed into the bloodstream via the gastrointestinal tract after a single oral dose. The liver, lung, and kidney could be possible target organs for accumulation and toxicity of ZnO nanoparticles was independent of particle size or gender. ZnO nanoparticles appear to be absorbed in the organs in an ionic form rather than in a particulate form due to newly formed Zn-S bonds. The nanoparticles were mainly excreted via the feces, and smaller particles were cleared more rapidly than the larger ones. ZnO nanoparticles at a concentration below 300 mg/kg were distributed in tissues and excreted within 24 hours. These findings provide crucial information on possible acute and chronic toxicity of ZnO nanoparticles in potential target organs. PMID:22811602

The Effect of Diagnostic Absorbed Doses from 131I on Human Thyrocytes in Vitro

PubMed Central

Adamczewski, Zbigniew; Stasiołek, Mariusz; Karwowski, Bolesław; Dedecjus, Marek; Orszulak-Michalak, Daria; Merecz, Anna; Śliwka, Przemysław W.; Puła, Bartosz; Lewiński, Andrzej

2015-01-01

Background: Administration of diagnostic activities of 131I, performed in order to detect thyroid remnants after surgery and/or thyroid cancer recurrence/metastases, may lead to reduction of iodine uptake. This phenomenon is called “thyroid stunning”. We estimated radiation absorbed dose-dependent changes in genetic material, in particular in sodium iodide symporter (NIS) gene promoter, and NIS protein level in human thyrocytes (HT). Materials and Methods: We used unmodified HT isolated from patients subjected to thyroidectomy exposed to 131I in culture. The different 131I activities applied were calculated to result in absorbed doses of 5, 10, and 20 Gy. Results: According to flow cytometry analysis and comet assay, 131I did not influence the HT viability in culture. Temporary increase of 8-oxo-dG concentration in HT directly after 24 h (p < 0.05) and increase in the number of AP-sites 72 h after termination of exposition to 20 Gy dose (p < 0.0001) were observed. The signs of dose-dependent DNA damage were not associated with essential changes in the NIS expression on mRNA and protein levels. Conclusions: Our observation constitutes a first attempt to evaluate the effect of the absorbed dose of 131I on HT. The results have not confirmed the theory that the “thyroid stunning” reduces the NIS protein synthesis. PMID:26132566

An international dosimetry exchange for boron neutron capture therapy. Part I: Absorbed dose measurements.

PubMed

Binns, P J; Riley, K J; Harling, O K; Kiger, W S; Munck af Rosenschöld, P M; Giusti, V; Capala, J; Sköld, K; Auterinen, I; Serén, T; Kotiluoto, P; Uusi-Simola, J; Marek, M; Viererbl, L; Spurny, F

2005-12-01

An international collaboration was organized to undertake a dosimetry exchange to enable the future combination of clinical data from different centers conducting neutron capture therapy trials. As a first step (Part I) the dosimetry group from the Americas, represented by MIT, visited the clinical centers at Studsvik (Sweden), VTT Espoo (Finland), and the Nuclear Research Institute (NRI) at Rez (Czech Republic). A combined VTT/NRI group reciprocated with a visit to MIT. Each participant performed a series of dosimetry measurements under equivalent irradiation conditions using methods appropriate to their clinical protocols. This entailed in-air measurements and dose versus depth measurements in a large water phantom. Thermal neutron flux as well as fast neutron and photon absorbed dose rates were measured. Satisfactory agreement in determining absorbed dose within the experimental uncertainties was obtained between the different groups although the measurement uncertainties are large, ranging between 3% and 30% depending upon the dose component and the depth of measurement. To improve the precision in the specification of absorbed dose amongst the participants, the individually measured dose components were normalized to the results from a single method. Assuming a boron concentration of 15 microg g(-1) that is typical of concentrations realized clinically with the boron delivery compound boronophenylalanine-fructose, systematic discrepancies in the specification of the total biologically weighted dose of up to 10% were apparent between the different groups. The results from these measurements will be used in future to normalize treatment plan calculations between the different clinical dosimetry protocols as Part II of this study.

Measurement of LET distribution and dose equivalent on board the space shuttle STS-65

NASA Technical Reports Server (NTRS)

Hayashi, T.; Doke, T.; Kikuchi, J.; Takeuchi, R.; Hasebe, N.; Ogura, K.; Nagaoka, S.; Kato, M.; Badhwar, G. D.

1996-01-01

Space radiation dosimetry measurements have been made on board the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called "Real-time Radiation Monitoring Device (RRMD)" utilizing silicon semi-conductor detectors and others are conventional detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. Using the RRMD detector, the first attempt of real-time monitoring of space radiation has been achieved successfully for a continuous period of 251.3 h, giving the temporal variations of LET distribution, particle count rates, and rates of absorbed dose and dose equivalent. The RRMD results indicate that a clear enhancement of the number of trapped particles is seen at the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent, while some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions for galactic cosmic ray particles (GCRs). Therefore, the main contribution to dose equivalent is seen to be due to GCRs in this low altitude mission (300 km). Also, the dose equivalent rates obtained by TLDs and CR-39 ranged from 146.9 to 165.2 microSv/day and the average quality factors from 1.45 to 1.57 depending on the locations and directions of detectors inside the Space-lab at this highly protected orbit for space radiation with a small inclination (28.5 degrees) and a low altitude (300 km). The LET distributions obtained by two different detectors, RRMD and CR-39, are in good agreement in the region of 15-200 keV/mm and difference of these distributions in the regions of LET < 15 keV/mm and LET > 200 keV/mm can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks.

Measurement of LET distribution and dose equivalent on board the space shuttle STS-65.

PubMed

Hayashi, T; Doke, T; Kikuchi, J; Takeuchi, R; Hasebe, N; Ogura, K; Nagaoka, S; Kato, M; Badhwar, G D

1996-11-01

Space radiation dosimetry measurements have been made on board the Space Shuttle STS-65 in the Second International Microgravity Laboratory (IML-2). In these measurements, three kinds of detectors were used; one is a newly developed active detector telescope called "Real-time Radiation Monitoring Device (RRMD)" utilizing silicon semi-conductor detectors and others are conventional detectors of thermoluminescence dosimeters (TLDs) and CR-39 plastic track detectors. Using the RRMD detector, the first attempt of real-time monitoring of space radiation has been achieved successfully for a continuous period of 251.3 h, giving the temporal variations of LET distribution, particle count rates, and rates of absorbed dose and dose equivalent. The RRMD results indicate that a clear enhancement of the number of trapped particles is seen at the South Atlantic Anomaly (SAA) without clear enhancement of dose equivalent, while some daily periodic enhancements of dose equivalent due to high LET particles are seen at the lower geomagnetic cutoff regions for galactic cosmic ray particles (GCRs). Therefore, the main contribution to dose equivalent is seen to be due to GCRs in this low altitude mission (300 km). Also, the dose equivalent rates obtained by TLDs and CR-39 ranged from 146.9 to 165.2 microSv/day and the average quality factors from 1.45 to 1.57 depending on the locations and directions of detectors inside the Space-lab at this highly protected orbit for space radiation with a small inclination (28.5 degrees) and a low altitude (300 km). The LET distributions obtained by two different detectors, RRMD and CR-39, are in good agreement in the region of 15-200 keV/mm and difference of these distributions in the regions of LET < 15 keV/mm and LET > 200 keV/mm can be explained by considering characteristics of CR-39 etched track formation especially for the low LET tracks.

Primary DNA damage assessed with the comet assay and comparison to the absorbed dose of diagnostic X-rays in children.

PubMed

Milkovic, Durdica; Garaj-Vrhovac, Vera; Ranogajec-Komor, Mária; Miljanic, Saveta; Gajski, Goran; Knezevic, Zeljka; Beck, Natko

2009-01-01

The aim of this work is to assess DNA damage in peripheral blood lymphocytes of children prior to and following airway X-ray examinations of the chest using the alkaline comet assay and to compare data with the measured absorbed dose. Twenty children with pulmonary diseases, between the ages of 5 and 14 years, are assessed. Absorbed dose measurements are conducted for posterior-anterior projection on the forehead, thyroid gland, gonads, chest, and back. Doses are measured using thermoluminescent and radiophotoluminescent dosimetry systems. Differences between tail lengths, tail intensity, and tail moments as well as for the long-tailed nuclei before and after exposures are statistically significant and are dependent on the individual. The results demonstrate the usefulness of the comet assay as a measure of X-ray damage to lymphocytes in a clinical setting. Doses measured with both dosimeters show satisfactory agreement (0.01 mSv) and are suitable for dosimetric measurements in X-ray diagnostics.

Heavy-ion-induced sucrose radicals investigated using EPR and UV spectroscopy

PubMed Central

Nakagawa, Kouichi; Karakirova, Yordanka; Yordanov, Nicola D.

2015-01-01

The potential use of a sucrose dosimeter for estimating both linear energy transfer (LET) and the absorbed dose of heavy ion and X-ray radiation was investigated. The stable free radicals were produced when sucrose was irradiated with heavy ions, such as helium, carbon, silicon and neon ions, and when the X-ray radiation was similar to the obtained electron paramagnetic resonance (EPR) spectra, which were ∼7 mT wide and composed of several hyperfine structures. In addition, the total spin concentration resulting from heavy-ion irradiation increased linearly as the absorbed dose increased, and decreased logarithmically as the LET increased. These empirical relations imply that the LET at a certain dose can be determined from the spin concentration. For sucrose and alanine, both cross-sections following C-ion irradiation with a 50 Gy dose were ∼1.3 × 10−12 [μm2], taking into account the molecular size of the samples. The values of these cross-sections imply that multiple ionizing particles were involved in the production of stable radicals. Furthermore, UV absorbance at 267 nm of an aqueous solution of irradiated sucrose was found to linearly increase with increasing absorbed dose. Therefore, the EPR and UV results suggest that sucrose can be a useful dosimeter for heavy-ion irradiation. PMID:25480828

Space dosimetry with the application of a 3D silicon detector telescope: response function and inverse algorithm.

PubMed

Pázmándi, Tamás; Deme, Sándor; Láng, Edit

2006-01-01

One of the many risks of long-duration space flights is the excessive exposure to cosmic radiation, which has great importance particularly during solar flares and higher sun activity. Monitoring of the cosmic radiation on board space vehicles is carried out on the basis of wide international co-operation. Since space radiation consists mainly of charged heavy particles (protons, alpha and heavier particles), the equivalent dose differs significantly from the absorbed dose. A radiation weighting factor (w(R)) is used to convert absorbed dose (Gy) to equivalent dose (Sv). w(R) is a function of the linear energy transfer of the radiation. Recently used equipment is suitable for measuring certain radiation field parameters changing in space and over time, so a combination of different measurements and calculations is required to characterise the radiation field in terms of dose equivalent. The objectives of this project are to develop and manufacture a three-axis silicon detector telescope, called Tritel, and to develop software for data evaluation of the measured energy deposition spectra. The device will be able to determine absorbed dose and dose equivalent of the space radiation.

Abdominal Pediatric Cancer Surveillance using Serial CT: Evaluation of Organ Absorbed Dose and Effective Dose

PubMed Central

Lam, Diana; Wootton-Gorges, Sandra L.; McGahan, John P.; Stern, Robin; Boone, John M.

2012-01-01

Computed tomography (CT) is used extensively in cancer diagnosis, staging, evaluation of response to treatment, and in active surveillance for cancer reoccurrence. A review of CT technology is provided, at a level of detail appropriate for a busy clinician to review. The basis of x-ray CT dosimetry is also discussed, and concepts of absorbed dose and effective dose are distinguished. Absorbed dose is a physical quantity (measured in milliGray) equal to the x-ray energy deposited in a mass of tissue, whereas effective dose utilizes an organ-specific weighting method which converts organ doses to effective dose measured in milliSieverts. The organ weighting values carry with them a measure of radiation risk, and so effective dose (in mSv) is not a physical dose metric but rather is one that conveys radiation risk. The use of CT in a cancer surveillance protocol was used as an example of a pediatric patient who had kidney cancer, with surgery and radiation therapy. The active use of CT for cancer surveillance along with diagnostic CT scans led to a total of 50 CT scans performed on this child in a 7 year period. It was estimated that the patient received an average organ dose of 431 mGy from these CT scans. By comparison, the radiation therapy was performed and delivered 50.4 Gy to the patient’s abdomen. Thus, the total dose from CT represented only 0.8% of the patients radiation dose. PMID:21362521

Olive oil phenolics are dose-dependently absorbed in humans.

PubMed

Visioli, F; Galli, C; Bornet, F; Mattei, A; Patelli, R; Galli, G; Caruso, D

2000-02-25

Olive oil phenolic constituents have been shown, in vitro, to be endowed with potent biological activities including, but not limited to, an antioxidant action. To date, there is no information on the absorption and disposition of such compounds in humans. We report that olive oil phenolics, namely tyrosol and hydroxytyrosol, are dose-dependently absorbed in humans after ingestion and that they are excreted in the urine as glucuronide conjugates. Furthermore, an increase in the dose of phenolics administered increased the proportion of conjugation with glucuronide.

A new tissue segmentation method to calculate 3D dose in small animal radiation therapy.

PubMed

Noblet, C; Delpon, G; Supiot, S; Potiron, V; Paris, F; Chiavassa, S

2018-02-26

In pre-clinical animal experiments, radiation delivery is usually delivered with kV photon beams, in contrast to the MV beams used in clinical irradiation, because of the small size of the animals. At this medium energy range, however, the contribution of the photoelectric effect to absorbed dose is significant. Accurate dose calculation therefore requires a more detailed tissue definition because both density (ρ) and elemental composition (Z eff ) affect the dose distribution. Moreover, when applied to cone beam CT (CBCT) acquisitions, the stoichiometric calibration of HU becomes inefficient as it is designed for highly collimated fan beam CT acquisitions. In this study, we propose an automatic tissue segmentation method of CBCT imaging that assigns both density (ρ) and elemental composition (Z eff ) in small animal dose calculation. The method is based on the relationship found between CBCT number and ρ*Z eff product computed from known materials. Monte Carlo calculations were performed to evaluate the impact of ρZ eff variation on the absorbed dose in tissues. These results led to the creation of a tissue database composed of artificial tissues interpolated from tissue values published by the ICRU. The ρZ eff method was validated by measuring transmitted doses through tissue substitute cylinders and a mouse with EBT3 film. Measurements were compared to the results of the Monte Carlo calculations. The study of the impact of ρZ eff variation over the range of materials, from ρZ eff  = 2 g.cm - 3 (lung) to 27 g.cm - 3 (cortical bone) led to the creation of 125 artificial tissues. For tissue substitute cylinders, the use of ρZ eff method led to maximal and average relative differences between the Monte Carlo results and the EBT3 measurements of 3.6% and 1.6%. Equivalent comparison for the mouse gave maximal and average relative differences of 4.4% and 1.2%, inside the 80% isodose area. Gamma analysis led to a 94.9% success rate in the 10% isodose area with 4% and 0.3 mm criteria in dose and distance. Our new tissue segmentation method was developed for 40kVp CBCT images. Both density and elemental composition are assigned to each voxel by using a relationship between HU and the product ρZ eff . The method, validated by comparing measurements and calculations, enables more accurate small animal dose distribution calculated on low energy CBCT images.

Modified radiotherapy technique in the treatment of medulloblastoma

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

Dewit, L.; Van Dam, J.; Rijnders, A.

1984-02-01

Craniospinal irradiation is a standard treatment technique in patients who receive surgery for medulloblastoma. In most centers megavoltage photon irradiation is used, resulting in significant irradiation exposure to critical organs. In order to overcome this difficulty, the authors recently modified the technique applied in their center, by using high energy electrons (20 MeV) for irradiation of the spinal cord. The reliability of this technique was checked by performing dosimetry in a specially constructed wax phantom. Attention was focused upon dose variations at the junction of fields. Furthermore, the influence of vertebrae on the absorbed dose distribution of high energy electronsmore » is presented. This technique seems to be safe and reliable in selected patients (children and teenagers).« less

The pharmacokinetics of a new benzamide drug clebopride, in the rat and the dog.

PubMed

Segura, J; García, I; Borja, L; Tarrús, E; Bakke, O M

1981-04-01

After intravenous, intramuscular and oral administration of clebopride in the rat and the dog its apparent volume of distribution is high (1.6-3.2 1 kg-1) and it has a longer biological half-life than metoclopramide in both species. High clearance values and concentrations of metabolites in plasma after oral administration indicate that the drug is subjected to an extensive first pass metabolism in the rat. Thus, clebopride administered orally gives relatively low concentrations in the systemic circulation in rats even though it is rapidly absorbed. The metabolic processes appear to become saturated at high doses which is reflected in dose-dependent kinetics. Linear kinetics were observed in the dog, although enterohepatic recycling could occur.

Uptake and retention of radio-caesium in earthworms cultured in soil contaminated by the Fukushima nuclear power plant accident.

PubMed

Fujiwara, K; Takahashi, T; Nguyen, P; Kubota, Y; Gamou, S; Sakurai, S; Takahashi, S

2015-01-01

To understand the effects of radionuclides on non-human biota and the environment, it is essential to study the intake and metabolism of radio-isotopes in earthworms which are among the most important soil organisms, and Eisenia fetida, which were used in this study, are known to be sufficiently sensitive to chemicals and representative of common earthworms. In this study, we assessed the concentration ratios, uptake and retention, absorbed dose rate, and distribution of radio-caesium in earthworms. The concentration ratios of (137)Cs (i.e., the concentrations of radio-caesium in earthworms relative to those in dry soil) were higher early in the culturing period and decreased gradually over the experimental period. (137)Cs taken up by E. fetida was cleared rapidly after the worms were cultured in radio-caesium-free soil, suggesting that the metabolism of radio-caesium in earthworms is very rapid. Autoradiography demonstrated that the concentration of radio-caesium within the digestive tract was as high as that in the soil, while radio-caesium in the body tissue was lower than radio-caesium in the soil and was almost uniformly distributed among earthworm tissues. The highest absorbed dose rate of total exposure to radio-caesium ((137)Cs + (134)Cs) was calculated to be 1.9 × 10(3) (μGy/day) in the earthworms. Copyright © 2014 Elsevier Ltd. All rights reserved.

Dose Calculations for [131I] Meta-Iodobenzylguanidine-Induced Bystander Effects

PubMed Central

Gow, M. D.; Seymour, C. B.; Boyd, M.; Mairs, R. J.; Prestiwch, W. V.; Mothersill, C. E.

2014-01-01

Targeted radiotherapy is a potentially useful treatment for some cancers and may be potentiated by bystander effects. However, without estimation of absorbed dose, it is difficult to compare the effects with conventional external radiation treatment. Methods: Using the Vynckier – Wambersie dose point kernel, a model for dose rate evaluation was created allowing for calculation of absorbed dose values to two cell lines transfected with the noradrenaline transporter (NAT) gene and treated with [131I]MIBG. Results: The mean doses required to decrease surviving fractions of UVW/NAT and EJ138/NAT cells, which received medium from [131I]MIBG-treated cells, to 25 – 30% were 1.6 and 1.7 Gy respectively. The maximum mean dose rates achieved during [131I]MIBG treatment were 0.09 – 0.75 Gy/h for UVW/NAT and 0.07 – 0.78 Gy/h for EJ138/NAT. These were significantly lower than the external beam gamma radiation dose rate of 15 Gy/h. In the case of control lines which were incapable of [131I]MIBG uptake the mean absorbed doses following radiopharmaceutical were 0.03 – 0.23 Gy for UVW and 0.03 – 0.32 Gy for EJ138. Conclusion: [131I]MIBG treatment for ICCM production elicited a bystander dose-response profile similar to that generated by external beam gamma irradiation but with significantly greater cell death. PMID:24659931

Dose distribution in the thyroid gland following radiation therapy of breast cancer--a retrospective study.

PubMed

Johansen, S; Reinertsen, K V; Knutstad, K; Olsen, D R; Fosså, S D

2011-06-09

To relate the development of post-treatment hypothyroidism with the dose distribution within the thyroid gland in breast cancer (BC) patients treated with loco-regional radiotherapy (RT). In two groups of BC patients postoperatively irradiated by computer tomography (CT)-based RT, the individual dose distributions in the thyroid gland were compared with each other; Cases developed post-treatment hypothyroidism after multimodal treatment including 4-field RT technique. Matched patients in Controls remained free for hypothyroidism. Based on each patient's dose volume histogram (DVH) the volume percentages of the thyroid absorbing respectively 20, 30, 40 and 50 Gy were then estimated (V20, V30, V40 and V50) together with the individual mean thyroid dose over the whole gland (MeanTotGy). The mean and median thyroid dose for the included patients was about 30 Gy, subsequently the total volume of the thyroid gland (VolTotGy) and the absolute volumes (cm3) receiving respectively <30 Gy and ≥30 Gy were calculated (Vol<30 and Vol≥30) and analyzed. No statistically significant inter-group differences were found between V20, V30, V40 and V50Gy or the median of MeanTotGy. The median VolTotGy in Controls was 2.3 times above VolTotGy in Cases (ρ=0.003), with large inter-individual variations in both groups. The volume of the thyroid gland receiving<30 Gy in Controls was almost 2.5 times greater than the comparable figure in Cases. We concluded that in patients with small thyroid glands after loco-radiotherapy of BC, the risk of post-treatment hypothyroidism depends on the volume of the thyroid gland.

An estimate by two methods of thyroid absorbed doses due to BRAVO fallout in several Northern Marshall Islands.

PubMed

Musolino, S V; Greenhouse, N A; Hull, A P

1997-10-01

Estimates of the thyroid absorbed doses due to fallout originating from the 1 March 1954 BRAVO thermonuclear test on Bikini Atoll have been made for several inhabited locations in the Northern Marshall Islands. Rongelap, Utirik, Rongerik and Ailinginae Atolls were also inhabited on 1 March 1954, where retrospective thyroid absorbed doses have previously been reconstructed. The current estimates are based primarily on external exposure data, which were recorded shortly after each nuclear test in the Castle Series, and secondarily on soil concentrations of 137Cs in samples collected in 1978 and 1988, along with aerial monitoring done in 1978. The external exposures and 137Cs soil concentrations were representative of the atmospheric transport and deposition patterns of the entire Castle Series tests and show that the BRAVO test was the major contributor to fallout exposure during the Castle series and other test series which were carried out in the Marshall Islands. These data have been used as surrogates for fission product radioiodines and telluriums in order to estimate the range of thyroid absorbed doses that may have occurred throughout the Marshall Islands. Dosimetry based on these two sets of estimates agreed within a factor of 4 at the locations where BRAVO was the dominant contributor to the total exposure and deposition. Both methods indicate that thyroid absorbed doses in the range of 1 Gy (100 rad) may have been incurred in some of the northern locations, whereas the doses at southern locations did not significantly exceed levels comparable to those from worldwide fallout. The results of these estimates indicate that a systematic medical survey for thyroid disease should be conducted, and that a more definitive dose reconstruction should be made for all the populated atolls and islands in the Northern Marshall Islands beyond Rongelap, Utirik, Rongerik and Ailinginae, which were significantly contaminated by BRAVO fallout.

Jet Fuel Exposure and Neurological Health in Military Personnel

DTIC Science & Technology

2011-07-01

and dermal samples E Absorbed Dose measure: Exhaled breath, urine , blood F Lifestyle factors (smoking), use of protective equipment (gloves...toluene, ethylbenzene, xylene, and naphthalene. To assess personal absorbed dose levels to JP8 components, exhaled breath and urine samples were...the following primary analytes of interest were measured: benzene, toluene, ethylbenzene, xylene, and naphthalene. Pre- and post- shift urine samples

Grain boundary resistance to amorphization of nanocrystalline silicon carbide

PubMed Central

Chen, Dong; Gao, Fei; Liu, Bo

2015-01-01

Under the C displacement condition, we have used molecular dynamics simulation to examine the effects of grain boundaries (GBs) on the amorphization of nanocrystalline silicon carbide (nc-SiC) by point defect accumulation. The results show that the interstitials are preferentially absorbed and accumulated at GBs that provide the sinks for defect annihilation at low doses, but also driving force to initiate amorphization in the nc-SiC at higher doses. The majority of surviving defects are C interstitials, as either C-Si or C-C dumbbells. The concentration of defect clusters increases with increasing dose, and their distributions are mainly observed along the GBs. Especially these small clusters can subsequently coalesce and form amorphous domains at the GBs during the accumulation of carbon defects. A comparison between displacement amorphized nc-SiC and melt-quenched single crystal SiC shows the similar topological features. At a dose of 0.55 displacements per atom (dpa), the pair correlation function lacks long range order, demonstrating that the nc-SiC is fully amorphilized. PMID:26558694

Grain boundary resistance to amorphization of nanocrystalline silicon carbide.

PubMed

Chen, Dong; Gao, Fei; Liu, Bo

2015-11-12

Under the C displacement condition, we have used molecular dynamics simulation to examine the effects of grain boundaries (GBs) on the amorphization of nanocrystalline silicon carbide (nc-SiC) by point defect accumulation. The results show that the interstitials are preferentially absorbed and accumulated at GBs that provide the sinks for defect annihilation at low doses, but also driving force to initiate amorphization in the nc-SiC at higher doses. The majority of surviving defects are C interstitials, as either C-Si or C-C dumbbells. The concentration of defect clusters increases with increasing dose, and their distributions are mainly observed along the GBs. Especially these small clusters can subsequently coalesce and form amorphous domains at the GBs during the accumulation of carbon defects. A comparison between displacement amorphized nc-SiC and melt-quenched single crystal SiC shows the similar topological features. At a dose of 0.55 displacements per atom (dpa), the pair correlation function lacks long range order, demonstrating that the nc-SiC is fully amorphilized.

Tolrestat kinetics

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

Hicks, D.R.; Kraml, M.; Cayen, M.N.

The kinetics of tolrestat, a potent inhibitor of aldose reductase, were examined. Serum concentrations of tolrestat and of total /sup 14/C were measured after dosing normal subjects and subjects with diabetes with /sup 14/C-labeled tolrestat. In normal subjects, tolrestat was rapidly absorbed and disappearance from serum was biphasic. Distribution and elimination t 1/2s were approximately 2 and 10 to 12 hr, respectively, after single and multiple doses. Unchanged tolrestat accounted for the major portion of /sup 14/C in serum. Radioactivity was rapidly and completely excreted in urine and feces in an approximate ratio of 2:1. Findings were much the samemore » in subjects with diabetes. In normal subjects, the kinetics of oral tolrestat were independent of dose in the 10 to 800 mg range. Repetitive dosing did not result in unexpected cumulation. Tolrestat was more than 99% bound to serum protein; it did not compete with warfarin for binding sites but was displaced to some extent by high concentrations of tolbutamide or salicylate.« less

Microdosimetric intercomparison of BNCT beams at BNL and MIT.

PubMed

Burmeister, Jay; Riley, Kent; Coderre, Jeffrey A; Harling, Otto K; Ma, Ruimei; Wielopolski, Lucian; Kota, Chandrasekhar; Maughan, Richard L

2003-08-01

Microdosimetric measurements have been performed at the clinical beam intensities in two epithermal neutron beams, the Brookhaven Medical Research Reactor and the M67 beam at the Massachusetts Institute of Technology Research Reactor, which have been used to treat patients with Boron Neutron Capture Therapy (BNCT). These measurements offer an independent assessment of the dosimetry used at these two facilities, as well as provide information about the radiation quality not obtainable from conventional macrodosimetric techniques. Moreover, they provide a direct measurement of the absorbed dose resulting from the BNC reaction. BNC absorbed doses measured within this study are approximately 15% lower than those estimated using foil activation at both MIT and BNL. Finally, an intercomparison of the characteristics and radiation quality of these two clinical beams is presented. The techniques described here allow an accurate quantitative comparison of the physical absorbed dose as well as a measure of the biological effectiveness of the absorbed dose delivered by different epithermal beams. No statistically significant differences were observed in the predicted RBEs of these two beams. The methodology presented here can help to facilitate the effective sharing of clinical results in an effort to demonstrate the clinical utility of BNCT.

Concentrations of 226Ra, 232Th and 40K in industrial kaolinized granite.

PubMed

Todorović, Nataša; Hansman, Jan; Mrđa, Dušan; Nikolov, Jovana; Kardos, Richárd; Krmar, Miodrag

2017-03-01

Activity concentrations of 226 Ra, 232 Th and 4 0 K in 120 kaolinized granite samples imported in Serbia from the Motajica mine, Bosnia and Herzegovina, were measured. The 226 Ra concentration ranged from 61 to 319 Bq kg -1 , the 232 Th from 44 to 272 Bq kg -1 , and the 4 0 K from 590 to 1470 Bq kg -1 . The frequency distribution of 4 0 K concentrations was near-Gaussian, where those of 226 Ra and 232 Th were right-skewed. In 6 samples, the gamma index, I, was higher than 2, which exceeds the exemption dose criterion (0.3 mSv y -1 ). The absorbed dose rate and annual effective doses for workers in the ceramic industries in Serbia who worked with kaolinized granite were below levels of concern. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evaluation of human body irradiation caused by radionuclides deposited in the filtration unit of gas mask.

PubMed

Cerny, R; Johnova, K; Otahal, P; Thinova, L; Kluson, J

2017-12-01

Radioactive aerosol particles represent a serious risk for people facing the consequences of nuclear accident of any kind. The first responders to emergency situation need to be protected by personal protective equipment which includes radiation protection suit supplemented with gas mask. The purpose of this work is to estimate the dose to the organs of responder's body as a result of radionuclide deposition in the filtration unit of the gas mask. The problem was analyzed using Monte Carlo simulations. The dose absorbed by different organs for five representative radionuclides and the dose distribution over the responder's body are presented in this paper. Based on presented MC simulations, we suggest a method of evaluating the irradiation of the responder by the radionuclides deposited in the filtration unit of the gas mask. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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.

External radiation in Dolon village due to local fallout from the first USSR atomic bomb test in 1949.

PubMed

Imanaka, Tetsuji; Fukutani, Satoshi; Yamamoto, Masayoshi; Sakaguchi, Aya; Hoshi, Masaharu

2006-02-01

Dolon village, located about 60 km from the border of the Semipalatinsk Nuclear Test Site, is known to be heavily contaminated by local fallout from the first USSR atomic bomb test in 1949. External radiation in Dolon was evaluated based on recent 137Cs data in soil and calculation of temporal change in the fission product composition. After fitting a log-normal distribution to the soil data, a 137Cs deposition of 32 kBq m-2, which corresponds to the 90th-percentile of the distribution, was tentatively chosen as a value to evaluate the radiation situation in 1949. Our calculation indicated that more than 95% of the cumulative dose for 50 y had been delivered within 1 y after the deposition. The resulting cumulative dose for 1 y after the deposition, normalized to the initial contamination containing 1 kBq m-2 of 137Cs, was 15.6 mGy, assuming a fallout arrival time of 3 h and a medium level of fractionation. Finally, 0.50 Gy of absorbed dose in air was derived as our tentative estimate for 1-year cumulative external dose in Dolon due to local fallout from the first USSR test in 1949.

Dose conversion coefficients for monoenergetic electrons incident on a realistic human eye model with different lens cell populations

NASA Astrophysics Data System (ADS)

Nogueira, P.; Zankl, M.; Schlattl, H.; Vaz, P.

2011-11-01

The radiation-induced posterior subcapsular cataract has long been generally accepted to be a deterministic effect that does not occur at doses below a threshold of at least 2 Gy. Recent epidemiological studies indicate that the threshold for cataract induction may be much lower or that there may be no threshold at all. A thorough study of this subject requires more accurate dose estimates for the eye lens than those available in ICRP Publication 74. Eye lens absorbed dose per unit fluence conversion coefficients for electron irradiation were calculated using a geometrical model of the eye that takes into account different cell populations of the lens epithelium, together with the MCNPX Monte Carlo radiation transport code package. For the cell population most sensitive to ionizing radiation—the germinative cells—absorbed dose per unit fluence conversion coefficients were determined that are up to a factor of 4.8 higher than the mean eye lens absorbed dose conversion coefficients for electron energies below 2 MeV. Comparison of the results with previously published values for a slightly different eye model showed generally good agreement for all electron energies. Finally, the influence of individual anatomical variability was quantified by positioning the lens at various depths below the cornea. A depth difference of 2 mm between the shallowest and the deepest location of the germinative zone can lead to a difference between the resulting absorbed doses of up to nearly a factor of 5000 for electron energy of 0.7 MeV.

Dose conversion coefficients for monoenergetic electrons incident on a realistic human eye model with different lens cell populations.

PubMed

Nogueira, P; Zankl, M; Schlattl, H; Vaz, P

2011-11-07

The radiation-induced posterior subcapsular cataract has long been generally accepted to be a deterministic effect that does not occur at doses below a threshold of at least 2 Gy. Recent epidemiological studies indicate that the threshold for cataract induction may be much lower or that there may be no threshold at all. A thorough study of this subject requires more accurate dose estimates for the eye lens than those available in ICRP Publication 74. Eye lens absorbed dose per unit fluence conversion coefficients for electron irradiation were calculated using a geometrical model of the eye that takes into account different cell populations of the lens epithelium, together with the MCNPX Monte Carlo radiation transport code package. For the cell population most sensitive to ionizing radiation-the germinative cells-absorbed dose per unit fluence conversion coefficients were determined that are up to a factor of 4.8 higher than the mean eye lens absorbed dose conversion coefficients for electron energies below 2 MeV. Comparison of the results with previously published values for a slightly different eye model showed generally good agreement for all electron energies. Finally, the influence of individual anatomical variability was quantified by positioning the lens at various depths below the cornea. A depth difference of 2 mm between the shallowest and the deepest location of the germinative zone can lead to a difference between the resulting absorbed doses of up to nearly a factor of 5000 for electron energy of 0.7 MeV.

Dose computation for therapeutic electron beams

NASA Astrophysics Data System (ADS)

Glegg, Martin Mackenzie

The accuracy of electron dose calculations performed by two commercially available treatment planning computers, Varian Cadplan and Helax TMS, has been assessed. Measured values of absorbed dose delivered by a Varian 2100C linear accelerator, under a wide variety of irradiation conditions, were compared with doses calculated by the treatment planning computers. Much of the motivation for this work was provided by a requirement to verify the accuracy of calculated electron dose distributions in situations encountered clinically at Glasgow's Beatson Oncology Centre. Calculated dose distributions are required in a significant minority of electron treatments, usually in cases involving treatment to the head and neck. Here, therapeutic electron beams are subject to factors which may cause non-uniformity in the distribution of dose, and which may complicate the calculation of dose. The beam shape is often irregular, the beam may enter the patient at an oblique angle or at an extended source to skin distance (SSD), tissue inhomogeneities can alter the dose distribution, and tissue equivalent material (such as wax) may be added to reduce dose to critical organs. Technological advances have allowed the current generation of treatment planning computers to implement dose calculation algorithms with the ability to model electron beams in these complex situations. These calculations have, however, yet to be verified by measurement. This work has assessed the accuracy of calculations in a number of specific instances. Chapter two contains a comparison of measured and calculated planar electron isodose distributions. Three situations were considered: oblique incidence, incidence on an irregular surface (such as that which would be arise from the use of wax to reduce dose to spinal cord), and incidence on a phantom containing a small air cavity. Calculations were compared with measurements made by thermoluminescent dosimetry (TLD) in a WTe electron solid water phantom. Chapter three assesses the planning computers' ability to model electron beam penumbra at extended SSD. Calculations were compared with diode measurements in a water phantom. Further measurements assessed doses in the junction region produced by abutting an extended SSD electron field with opposed photon fields. Chapter four describes an investigation of the size and shape of the region enclosed by the 90% isodose line when produced by limiting the electron beam with square and elliptical apertures. The 90% isodose line was chosen because clinical treatments are often prescribed such that a given volume receives at least 90% dose. Calculated and measured dose distributions were compared in a plane normal to the beam central axis. Measurements were made by film dosimetry. While chapters two to four examine relative doses, chapter five assesses the accuracy of absolute dose (or output) calculations performed by the planning computers. Output variation with SSD and field size was examined. Two further situations already assessed for the distribution of relative dose were also considered: an obliquely incident field, and a field incident on an irregular surface. The accuracy of calculations was assessed against criteria stipulated by the International Commission on Radiation Units and Measurement (ICRU). The Varian Cadplan and Helax TMS treatment planning systems produce acceptable accuracy in the calculation of relative dose from therapeutic electron beams in most commonly encountered situations. When interpreting clinical dose distributions, however, knowledge of the limitations of the calculation algorithm employed by each system is required in order to identify the minority of situations where results are not accurate. The calculation of absolute dose is too inaccurate to implement in a clinical environment. (Abstract shortened by ProQuest.).

γ-H2AX/53BP1/pKAP-1 foci and their linear tracks induced by in vitro exposure to radon and its progeny in human peripheral blood lymphocytes

PubMed Central

Ding, Defang; Zhang, Yaping; Wang, Jing; Wang, Xufei; Fan, Dunhuang; He, Linfeng; Zhang, Xuxia; Gao, Yun; Li, Qiang; Chen, Honghong

2016-01-01

The biodosimetric information is critical for evaluating the human health hazards caused by radon and its progeny. Here, we demonstrated that the formation of phosphorylated histone variant H2AX (γ-H2AX), p53-binding protein 1 (53BP1) and phosphorylated KRAB-associated protein 1 (pKAP-1) foci and their linear tracks in human peripheral blood lymphocytes (HPBLs) in vitro exposed to radon and its progeny were dependent on the cumulative absorbed dose of radon exposure but was unrelated to the concentration of radon. Among them, γ-H2AX foci and its linear tracks were the most sensitive indicators with the lowest estimable cumulative absorbed dose of 1.74 mGy from their linear dose-response curves and sustained for 12 h after termination of radon exposure. In addition, three types of foci showed an overdispersed non-Poisson distribution in HPBLs. The ratios of pKAP-1/γ-H2AX foci co-localization, 53BP1/γ-H2AX foci co-localization and 53BP1/pKAP-1 foci co-localization were significantly increased in HPBLs exposed to radon while they were unrelated to the cumulative dose of radon exposure, suggesting that γ-H2AX, pKAP-1 and 53BP1 play an important role in the repair of heterochromatic double-strand breaks. Altogether, our findings provide an experimental basis for estimating the biological dose of internal α-particle irradiation from radon and its progeny exposure in humans. PMID:27922110

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

Exact analytic flux distributions for two-dimensional solar concentrators.

PubMed

Fraidenraich, Naum; Henrique de Oliveira Pedrosa Filho, Manoel; Vilela, Olga C; Gordon, Jeffrey M

2013-07-01

A new approach for representing and evaluating the flux density distribution on the absorbers of two-dimensional imaging solar concentrators is presented. The formalism accommodates any realistic solar radiance and concentrator optical error distribution. The solutions obviate the need for raytracing, and are physically transparent. Examples illustrating the method's versatility are presented for parabolic trough mirrors with both planar and tubular absorbers, Fresnel reflectors with tubular absorbers, and V-trough mirrors with planar absorbers.

Applying an analytical method to study neutron behavior for dosimetry

NASA Astrophysics Data System (ADS)

Shirazi, S. A. Mousavi

2016-12-01

In this investigation, a new dosimetry process is studied by applying an analytical method. This novel process is associated with a human liver tissue. The human liver tissue has compositions including water, glycogen and etc. In this study, organic compound materials of liver are decomposed into their constituent elements based upon mass percentage and density of every element. The absorbed doses are computed by analytical method in all constituent elements of liver tissue. This analytical method is introduced applying mathematical equations based on neutron behavior and neutron collision rules. The results show that the absorbed doses are converged for neutron energy below 15MeV. This method can be applied to study the interaction of neutrons in other tissues and estimating the absorbed dose for a wide range of neutron energy.

Energetic properties' investigation of removing flattening filter at phantom surface: Monte Carlo study using BEAMnrc code, DOSXYZnrc code and BEAMDP code

NASA Astrophysics Data System (ADS)

Bencheikh, Mohamed; Maghnouj, Abdelmajid; Tajmouati, Jaouad

2017-11-01

The Monte Carlo calculation method is considered to be the most accurate method for dose calculation in radiotherapy and beam characterization investigation, in this study, the Varian Clinac 2100 medical linear accelerator with and without flattening filter (FF) was modelled. The objective of this study was to determine flattening filter impact on particles' energy properties at phantom surface in terms of energy fluence, mean energy, and energy fluence distribution. The Monte Carlo codes used in this study were BEAMnrc code for simulating linac head, DOSXYZnrc code for simulating the absorbed dose in a water phantom, and BEAMDP for extracting energy properties. Field size was 10 × 10 cm2, simulated photon beam energy was 6 MV and SSD was 100 cm. The Monte Carlo geometry was validated by a gamma index acceptance rate of 99% in PDD and 98% in dose profiles, gamma criteria was 3% for dose difference and 3mm for distance to agreement. In without-FF, the energetic properties was as following: electron contribution was increased by more than 300% in energy fluence, almost 14% in mean energy and 1900% in energy fluence distribution, however, photon contribution was increased 50% in energy fluence, and almost 18% in mean energy and almost 35% in energy fluence distribution. The removing flattening filter promotes the increasing of electron contamination energy versus photon energy; our study can contribute in the evolution of removing flattening filter configuration in future linac.

MO-AB-BRA-03: Calorimetry-Based Absorbed Dose to Water Measurements Using Interferometry

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

Flores-Martinez, E; Malin, M; DeWerd, L

2015-06-15

Purpose: Interferometry-based calorimetry is a novel technique to measure radiation-induced temperature changes allowing the measurement of absorbed dose to water (ADW). There are no mechanical components in the field. This technique also has the possibility of obtaining 2D dose distributions. The goal of this investigation is to calorimetrically-measure doses between 2.5 and 5 Gy over a single projection in a photon beam using interferometry and compare the results with doses calculated using the TG-51 linac calibration. Methods: ADW was determined by measuring radiation-induced phase shifts (PSs) of light passing through water irradiated with a 6 MV photon beam. A 9×9×9more » cm{sup 3} glass phantom filled with water and placed in an arm of a Michelson interferometer was irradiated with 300, 400, 500 and 600 monitor units. The whole system was thermally insulated to achieve sufficient passive temperature control. The depth of measurement was 4.5 cm with a field size of 7×7 cm{sup 2}. The intensity of the fringe pattern was monitored with a photodiode and used to calculate the time-dependent PS curve. Data was acquired 60 s before and after the irradiation. The radiation-induced PS was calculated by taking the difference in the pre- and post-irradiation drifts extrapolated to the midpoint of the irradiation. Results were compared to computed doses. Results: Average comparison of calculated ADW values with interferometry-measured values showed an agreement to within 9.5%. k=1 uncertainties were 4.3% for calculations and 14.7% for measurements. The dominant source of uncertainty for the measurements was a temperature drift of about 30 µK/s caused by heat conduction from the interferometer’s surroundings. Conclusion: This work presented the first absolute ADW measurements using interferometry in the dose range of linac-based radiotherapy. Future work to improve measurements’ reproducibility includes the implementation of active thermal control techniques.« less

Effect of low dose and moderate dose gamma irradiation on the mechanical properties of bone and soft tissue allografts.

PubMed

Balsly, Colleen R; Cotter, Andrew T; Williams, Lisa A; Gaskins, Barton D; Moore, Mark A; Wolfinbarger, Lloyd

2008-12-01

The increased use of allograft tissue for musculoskeletal repair has brought more focus to the safety of allogenic tissue and the efficacy of various sterilization techniques. Gamma irradiation is an effective method for providing terminal sterilization to biological tissue, but it is also reported to have deleterious effects on tissue mechanics in a dose-dependent manner. At irradiation ranges up to 25 kGy, a clear relationship between mechanical strength and dose has yet to be established. The aim of this study was to investigate the mechanical properties of bone and soft tissue allografts, irradiated on dry ice at a low absorbed dose (18.3-21.8 kGy) and a moderate absorbed dose (24.0-28.5 kGy), using conventional compressive and tensile testing, respectively. Bone grafts consisted of Cloward dowels and iliac crest wedges, while soft tissue grafts consisted of patellar tendons, anterior tibialis tendons, semitendinosus tendons, and fascia lata. There were no statistical differences in mechanical strength or modulus of elasticity for any graft irradiated at a low absorbed dose, compared to control groups. Also, bone allografts and two soft tissue allografts (anterior tibialis and semitendinosus tendon) that were irradiated at a moderate dose demonstrated similar strength and modulus of elasticity values to control groups. The results of this study support the use of low dose and moderate dose gamma irradiation of bone grafts. For soft tissue grafts, the results support the use of low dose irradiation.

[Absorbed dose and the effective dose of panoramic temporo mandibular joint radiography].

PubMed

Matsuo, Ayae; Okano, Tsuneichi; Gotoh, Kenichi; Yokoi, Midori; Hirukawa, Akiko; Okumura, Shinji; Koyama, Syuji

2011-01-01

This study measured the radiation doses absorbed by the patient during Panoramic temporo mandibular joint radiography (Panoramic TMJ), Schüllers method and Orbitoramus projection. The dose of the frontal view in Panoramic TMJ was compared to that with Orbitoramus projection and the lateral view in Panoramic TMJ was compared to that with Schüllers method. We measured the doses received by various organs and calculated the effective doses using the guidelines of the International Commission on Radiological Protection in Publication 103. Organ absorbed doses were measured using an anthropomorphic phantom, loaded with thermoluminescent dosimeters (TLD), located at 160 sensitive sites. The dose shows the sum value of irradiation on both the right and left sides. In addition, we set a few different exposure field sizes. The effective dose for a frontal view in Panoramic TMJ was 11 µSv, and that for the lateral view was 14 µSv. The lens of the Orbitoramus projection was 40 times higher than the frontal view in Panoramic TMJ. Although the effective dose of the lateral view in Panoramic TMJ was 3 times higher than that of the small exposure field (10×10 cm on film) in Schüller's method, it was the same as that of a mid-sized exposure field. When the exposure field in the inferior 1/3 was reduced during panoramic TMJ, the effective doses could be decreased. Therefore we recommend that the size of the exposure field in Panoramic TMJ be decreased.

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

Leichner, P.K.

This report summarizes research in beta-particle dosimetry, quantitative single-photon emission computed tomography (SPECT), the clinical implementation of these two areas of research in radioimmunotherapy (RIT), and postgraduate training provided since the inception of this grant on July 15, 1989. To improve beta-particle dosimetry, a point source function was developed that is valid for a wide range of beta emitters. Analytical solutions for beta-particle dose rates within out outside slabs of finite thickness were validated in experimental tumors and are now being used in clinical RIT. Quantitative SPECT based on the circular harmonic transform (CHT) algorithm was validated in phantom, experimental,more » and clinical studies. This has led to improved macrodosimetry in clinical RIT. In dosimetry at the multi-cellular level studies were made of the HepG2 human hepatoblastoma grown subcutaneously in nude mice. Histologic sections and autoradiographs were prepared to quantitate activity distributions of radiolabeled antibodies. Absorbed-dose calculations are being carried out for {sup 131}I and {sup 90}Y beta particles for these antibody distributions.« less

UVPROM dosimetry, microdosimetry and applications to SEU and extreme value theory

NASA Astrophysics Data System (ADS)

Scheick, Leif Zebediah

A new method is described for characterizing a device in terms of the statistical distribution of first failures. The method is based on the erasure of a commercial Ultra- Violet erasable Programmable Read Only Memory (UVPROM). The method of readout would be used on a spacecraft or in other restrictive radiation environments. The measurement of the charge remaining on the floating gate is used to determine absorbed dose. The method of determining dose does not require the detector to be destroyed or erased nor does it effect the ability for taking further measurements. This is compared to extreme value theory applied to the statistical distributions that apply to this device. This technique predicts the threshold of Single Event Effects (SEE), like anomalous changes in erasure time in programmable devices due to high microdose energy-deposition events. This technique also allows for advanced non-destructive, screening of a single microelectronic devices for predictable response in a stressful, i.e. radiation, environments.

The MATROSHKA experiment: results and comparison from extravehicular activity (MTR-1) and intravehicular activity (MTR-2A/2B) exposure.

PubMed

Berger, Thomas; Bilski, Paweł; Hajek, Michael; Puchalska, Monika; Reitz, Günther

2013-12-01

Astronauts working and living in space are exposed to considerably higher doses and different qualities of ionizing radiation than people on Earth. The multilateral MATROSHKA (MTR) experiment, coordinated by the German Aerospace Center, represents the most comprehensive effort to date in radiation protection dosimetry in space using an anthropomorphic upper-torso phantom used for radiotherapy treatment planning. The anthropomorphic upper-torso phantom maps the radiation distribution as a simulated human body installed outside (MTR-1) and inside different compartments (MTR-2A: Pirs; MTR-2B: Zvezda) of the Russian Segment of the International Space Station. Thermoluminescence dosimeters arranged in a 2.54 cm orthogonal grid, at the site of vital organs and on the surface of the phantom allow for visualization of the absorbed dose distribution with superior spatial resolution. These results should help improve the estimation of radiation risks for long-term human space exploration and support benchmarking of radiation transport codes.

Radionuclides and Radiation Indices of High Background Radiation Area in Chavara-Neendakara Placer Deposits (Kerala, India)

PubMed Central

Derin, Mary Thomas; Vijayagopal, Perumal; Venkatraman, Balasubramaniam; Chaubey, Ramesh Chandra; Gopinathan, Anilkumar

2012-01-01

The present paper describes a detailed study on the distribution of radionuclides along Chavara – Neendakara placer deposit, a high background radiation area (HBRA) along the Southwest coast of India (Kerala). Judged from our studies using HPGe gamma spectrometric detector, it becomes evident that Uranium (238U), Thorium (232Th) and Potassium (40K) are the major sources for radioactivity prevailing in the area. Our statistical analyses reveal the existence of a high positive correlation between 238U and 232Th, implicating that the levels of these elements are interdependent. Our SEM-EDAX analyses reveal that titanium (Ti) and zircon (Zr) are the major trace elements in the sand samples, followed by aluminum, copper, iron, ruthenium, magnesium, calcium, sulphur and lead. This is first of its kind report on the radiation hazard indices on this placer deposit. The average absorbed dose rates (9795 nGy h−1) computed from the present study is comparable with the top-ranking HBRAs in the world, thus offering the Chavara-Neendakara placer the second position, after Brazil; pertinently, this value is much higher than the World average. The perceptibly high absorbed gamma dose rates, entrained with the high annual external effective dose rates (AEED) and average annual gonadal dose equivalent (AGDE) values existing in this HBRA, encourage us to suggest for a candid assessment of the impact of the background radiation, if any, on the organisms that inhabit along this placer deposit. Future research could effectively address the issue of the possible impact of natural radiation on the biota inhabiting this HBRA. PMID:23185629

Sci—Fri PM: Dosimetry—01: Radiation-induced refraction artefacts in the optical CT readout of polymer gel dosimeters

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

Campbell, Warren G; Jirasek, Andrew; Wells, Derek M

2014-08-15

Polymer gel dosimeters (PGDs) are a desirable tool for the verification of advanced radiotherapy treatments. Fully 3D, deformable, and tissue-equivalent, the PGD polymerizes wherever it absorbs dose. To measure the dose absorbed by a PGD, optical computed tomography (CT) can be used to evaluate, in full 3D, the opacity distribution that coincides with polymerization. In addition to an increase in opacity with dose, an increase in refractive index (RI) is also known to occur in irradiated polymer gels. The increase in RI is slight and was previously assumed insignificant. This work reveals the effects that radiation-induced RI changes can havemore » on the optical CT readout of PGDs. A fan-beam optical CT scanner was used to image a cylindrical PGD irradiated by a pair of 3×3 cm{sup 2}, 6 MV photon beams in an orthogonal arrangement. Investigative scans were performed to evaluate refraction errors occurring: i) within the plane, and ii) out of the plane of the fan-beam. In-plane refraction was shown to cause distinct streaking artefacts along dose gradients (i.e. RI gradients) due to higher intensity rays being refracted into more opaque regions. Out-of-plane refraction was shown to produce severe, widespread artefacts due to rays missing the detector array. An iterative Savitzky-Golay filtering technique was developed to reduce both types of artefacts by specifically targeting structured errors in sinogram space. Results introduce a new category of imaging artefacts to be aware of when using optical CT for PGD readout.« less

The development of fetal dosimetry and its application to A-bomb survivors exposed in utero.

PubMed

Chen, Jing

2012-03-01

The cohort of the atomic bomb survivors of Hiroshima and Nagasaki comprises the major basis for investigations of health effects induced by ionising radiation in humans. To study the health effects associated with radiation exposure before birth, fetal dosimetry is needed if significant differences exist between the fetal absorbed dose and the mother's uterine dose. Combining total neutron and gamma ray free-in-air fluences at 1 m above ground with fluence-to-absorbed dose conversion coefficients, fetal doses were calculated for various exposure orientations at the ground distance of 1500 m from the hypocentres in Hiroshima and Nagasaki. The results showed that the mother's uterine dose can serve as a good surrogate for the dose of the embryo and fetus in the first trimester. However, significant differences exist between doses of the fetus of different ages. If the mother's uterine dose were used as a surrogate, doses to the fetus in the last two trimesters could be overestimated by more than 20 % for exposure orientations facing towards and away from the hypocentre while significantly underestimated for lateral positions relative to the hypocentre. In newer fetal models, the brain is modelled for all fetal ages. Brain doses to the 3-month fetus are generally higher than those to an embryo and fetus of other ages. In most cases, brain absorbed doses differ significantly from the doses to the entire fetal body. In order to accurately assess radiation effects to the fetal brain, it is necessary to determine brain doses separately.

Organ biodistribution of Germanium-68 in rat in the presence and absence of [68Ga]Ga-DOTA-TOC for the extrapolation to the human organ and whole-body radiation dosimetry

PubMed Central

Velikyan, Irina; Antoni, Gunnar; Sörensen, Jens; Estrada, Sergio

2013-01-01

Positron Emission Tomography (PET) and in particular gallium-68 (68Ga) applications are growing exponentially worldwide contributing to the expansion of nuclear medicine and personalized management of patients. The significance of 68Ga utility is reflected in the implementation of European Pharmacopoeia monographs. However, there is one crucial point in the monographs that might limit the use of the generators and consequently expansion of 68Ga applications and that is the limit of 0.001% of Germanium-68 (68Ge(IV)) radioactivity content in a radiopharmaceutical. We have investigated the organ distribution of 68Ge(IV) in rat and estimated human dosimetry parameters in order to provide experimental evidence for the determination and justification of the 68Ge(IV) limit. Male and female rats were injected in the tail vein with formulated [68Ge]GeCl4 in the absence or presence of [68Ga]Ga-DOTA-TOC. The tissue radioactivity distribution data was extrapolated for the estimation of human organ equivalent doses and total effective dose using Organ Level Internal Dose Assessment Code software (OLINDA/EXM). 68Ge(IV) was evenly distributed among the rat organs and fast renal excretion prevailed. Human organ equivalent dose and total effective dose estimates indicated that the kidneys were the dose-limiting organs (185±54 μSv/MBq for female and 171±38 μSv/MBq for male) and the total effective dose was 15.5±0.1 and 10.7±1.2 μSv/MBq, respectively for female and male. The results of this dosimetry study conclude that the 68Ge(IV) limit currently recommended by monographs could be increased considerably (>100 times) without exposing the patient to harm given the small absorbed doses to normal organs and fast excretion. PMID:23526484

Radioactivity concentrations in soils in the Qingdao area, China.

PubMed

Qu, Limei; Yao, De; Cong, Pifu; Xia, Ning

2008-10-01

The specific activity concentrations of radionuclides (238)U, (232)Th, and (40)K of 2300 sampling points in the Qingdao area were measured by an FD-3022 gamma-ray spectrometer. The radioactivity concentrations of (238)U, (232)Th, and (40)K ranged from 3.3 to 185.3, from 6.9 to 157.2, and from 115.8 to 7834.4 Bq kg(-1), respectively. The air-absorbed dose at 1 meter above ground, effective annual dose, external hazard index, and radium equivalent activity were also calculated to systematically evaluate the radiological hazards of the natural radioactivity in Qingdao. The air-absorbed dose, effective annual dose, external hazard index, and radium equivalent activity in the study area were 98.6 nGy h(-1), 0.12 mSv, 0.56, 197 Bq kg(-1), respectively. Compared with the worldwide value, the air-absorbed dose is slightly high, but the other factors are all lower than the recommended value. The natural external exposure will not pose significant radiological threat to the population. In conclusion, the Qingdao area is safe with regard to the radiological level and suitable for living.

Deterministic absorbed dose estimation in computed tomography using a discrete ordinates method

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

Norris, Edward T.; Liu, Xin, E-mail: xinliu@mst.edu; Hsieh, Jiang

Purpose: Organ dose estimation for a patient undergoing computed tomography (CT) scanning is very important. Although Monte Carlo methods are considered gold-standard in patient dose estimation, the computation time required is formidable for routine clinical calculations. Here, the authors instigate a deterministic method for estimating an absorbed dose more efficiently. Methods: Compared with current Monte Carlo methods, a more efficient approach to estimating the absorbed dose is to solve the linear Boltzmann equation numerically. In this study, an axial CT scan was modeled with a software package, Denovo, which solved the linear Boltzmann equation using the discrete ordinates method. Themore » CT scanning configuration included 16 x-ray source positions, beam collimators, flat filters, and bowtie filters. The phantom was the standard 32 cm CT dose index (CTDI) phantom. Four different Denovo simulations were performed with different simulation parameters, including the number of quadrature sets and the order of Legendre polynomial expansions. A Monte Carlo simulation was also performed for benchmarking the Denovo simulations. A quantitative comparison was made of the simulation results obtained by the Denovo and the Monte Carlo methods. Results: The difference in the simulation results of the discrete ordinates method and those of the Monte Carlo methods was found to be small, with a root-mean-square difference of around 2.4%. It was found that the discrete ordinates method, with a higher order of Legendre polynomial expansions, underestimated the absorbed dose near the center of the phantom (i.e., low dose region). Simulations of the quadrature set 8 and the first order of the Legendre polynomial expansions proved to be the most efficient computation method in the authors’ study. The single-thread computation time of the deterministic simulation of the quadrature set 8 and the first order of the Legendre polynomial expansions was 21 min on a personal computer. Conclusions: The simulation results showed that the deterministic method can be effectively used to estimate the absorbed dose in a CTDI phantom. The accuracy of the discrete ordinates method was close to that of a Monte Carlo simulation, and the primary benefit of the discrete ordinates method lies in its rapid computation speed. It is expected that further optimization of this method in routine clinical CT dose estimation will improve its accuracy and speed.« less

Neutron dosimetry in organs of an adult human phantom using linacs with multileaf collimator in radiotherapy treatments

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

Martinez-Ovalle, S. A.; Barquero, R.; Gomez-Ros, J. M.

Purpose: To calculate absorbed doses due to neutrons in 87 organs/tissues for anthropomorphic phantoms, irradiated in position supine (head first into the gantry) with orientations anteroposterior (AP) and right-left (RLAT) with a 18 MV accelerator. Conversion factors from monitor units to {mu}Gy per neutron in organs, equivalent doses in organs/tissues, and effective doses, which permit to quantify stochastic risks, are estimated. Methods: MAX06 and FAX06 phantoms were modeled with MCNPX and irradiated with a 18 MV Varian Clinac 2100C/D accelerator whose geometry included a multileaf collimator. Two actual fields of a pelvic treatment were simulated using electron-photon-neutron coupled transport. Absorbedmore » doses due to neutrons were estimated from kerma. Equivalent doses were estimated using the radiation weighting factor corresponding to an average incident neutron energy 0.47 MeV. Statistical uncertainties associated to absorbed doses, as calculated by MCNPX, were also obtained. Results: Largest doses were absorbed in shallowest (with respect to the neutron pathway) organs. In {mu}GyMU{sup -1}, values of 2.66 (for penis) and 2.33 (for testes) were found in MAX06, and 1.68 (for breasts), 1.05 (for lenses of eyes), and 0.94 (for sublingual salivary glands) in FAX06, in AP orientation. In RLAT, the largest doses were found for bone tissues (leg) just at the entrance of the beam in the body (right side in our case). Values, in {mu}GyMU{sup -1}, of 1.09 in upper leg bone right spongiosa, for MAX06, and 0.63 in mandible spongiosa, for FAX06, were found. Except for gonads, liver, and stomach wall, equivalent doses found for FAX06 were, in both orientations, higher than for MAX06. Equivalent doses in AP are higher than in RLAT for all organs/tissues other than brain and liver. Effective doses of 12.6 and 4.1 {mu}SvMU{sup -1} were found for AP and RLAT, respectively. The organs/tissues with larger relative contributions to the effective dose were testes and breasts, in AP, and breasts and red marrow, in RLAT. Equivalent and effective doses obtained for MAX06/FAX06 were smaller (between 2 and 20 times) than those quoted for the mathematical phantoms ADAM/EVA in ICRP-74. Conclusions: The new calculations of conversion coefficients for neutron irradiation in AP and RLAT irradiation geometries show a reduction in the values of effective dose by factors 7 (AP) and 6 (RLAT) with respect to the old data obtained with mathematical phantoms. The existence of tissues or anatomical regions with maximum absorbed doses, such as penis, lens of eyes, fascia (part of connective tissue), etc., organs/tissues that classic mathematical phantoms did not include because they were not considered for the study of stochastic effects, has been revealed. Absorbed doses due to photons, obtained following the same simulation methodology, are larger than those due to neutrons, reaching values 100 times larger as the primary beam is approached. However, for organs far from the treated volume, absorbed photon doses can be up to three times smaller than neutron ones. Calculations using voxel phantoms permitted to know the organ dose conversion coefficients per MU due to secondary neutrons in the complete anatomy of a patient.« less

Dosimetric Comparison in Breast Radiotherapy of 4 MV and 6 MV on Physical Chest Simulator

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

Donato da Silva, Sabrina; Passos Ribeiro Campos, Tarcisio; Batista Nogueira, Luciana

2015-07-01

According to the World Health Organization (2014) breast cancer is the main cause of death by cancer in women worldwide. The biggest challenge of radiotherapy in the treatment of cancer is to deposit the entire prescribed dose homogeneously in the breast, sparing the surrounding tissue. In this context, this paper aimed at evaluating and comparing internal dose distribution in the mammary gland based on experimental procedures submitted to two distinct energy spectra produced in breast cancer radiotherapy. The methodology consisted of reproducing opposite parallel fields used in the treatment of breast tumors in a chest phantom. This simulator with syntheticmore » breast, composed of equivalent tissue material (TE), was previously developed by the NRI Research Group (UFMG). The computer tomography (CT) scan of the simulator was obtained antecedently. The radiotherapy planning systems (TPS) in the chest phantom were performed in the ECLIPSE system from Varian Medical Systems and CAT 3D system from MEVIS. The irradiations were reproduced in the Varian linear accelerator, model SL- 20 Precise, 6 MV energy and Varian linear accelerator, 4 MV Clinac 6x SN11 model. Calibrations of the absorbed dose versus optical density from radiochromic films were generated in order to obtain experimental dosimetric distribution at the films positioned within the glandular and skin equivalent tissues of the chest phantom. The spatial dose distribution showed equivalence with the TPS on measurement data performed in the 6 MV spectrum. The average dose found in radiochromic films placed on the skin ranged from 49 to 79%, and from 39 to 49% in the mammary areola, for the prescribed dose. Dosimetric comparisons between the spectra of 4 and 6 MV, keeping the constant geometry of the fields applied in the same phantom, will be presented showing their equivalence in breast radiotherapy, as well as the variations will be discussed. To sum up, the dose distribution has reached the value expected in the breast dose of the 180 cGy in a wide range of the film in the glandular TE in both spectra. (authors)« less

Dosimetry for nonuniform activity distributions: a method for the calculation of 3D absorbed-dose distribution without the use of voxel S-values, point kernels, or Monte Carlo simulations.

PubMed

Traino, A C; Marcatili, S; Avigo, C; Sollini, M; Erba, P A; Mariani, G

2013-04-01

Nonuniform activity within the target lesions and the critical organs constitutes an important limitation for dosimetric estimates in patients treated with tumor-seeking radiopharmaceuticals. The tumor control probability and the normal tissue complication probability are affected by the distribution of the radionuclide in the treated organ/tissue. In this paper, a straightforward method for calculating the absorbed dose at the voxel level is described. This new method takes into account a nonuniform activity distribution in the target/organ. The new method is based on the macroscopic S-values (i.e., the S-values calculated for the various organs, as defined in the MIRD approach), on the definition of the number of voxels, and on the raw-count 3D array, corrected for attenuation, scatter, and collimator resolution, in the lesion/organ considered. Starting from these parameters, the only mathematical operation required is to multiply the 3D array by a scalar value, thus avoiding all the complex operations involving the 3D arrays. A comparison with the MIRD approach, fully described in the MIRD Pamphlet No. 17, using S-values at the voxel level, showed a good agreement between the two methods for (131)I and for (90)Y. Voxel dosimetry is becoming more and more important when performing therapy with tumor-seeking radiopharmaceuticals. The method presented here does not require calculating the S-values at the voxel level, and thus bypasses the mathematical problems linked to the convolution of 3D arrays and to the voxel size. In the paper, the results obtained with this new simplified method as well as the possibility of using it for other radionuclides commonly employed in therapy are discussed. The possibility of using the correct density value of the tissue/organs involved is also discussed.

Evaluation of lens absorbed dose with Cone Beam IGRT procedures.

PubMed

Palomo, R; Pujades, M C; Gimeno-Olmos, J; Carmona, V; Lliso, F; Candela-Juan, C; Vijande, J; Ballester, F; Perez-Calatayud, J

2015-12-01

The purpose of this work is to evaluate the absorbed dose to the eye lenses due to the cone beam computed tomography (CBCT) system used to accurately position the patient during head-and-neck image guided procedures. The on-board imaging (OBI) systems (v.1.5) of Clinac iX and TrueBeam (Varian) accelerators were used to evaluate the imparted dose to the eye lenses and some additional points of the head. All CBCT scans were acquired with the Standard-Dose Head protocol from Varian. Doses were measured using thermoluminescence dosimeters (TLDs) placed in an anthropomorphic phantom. TLDs were calibrated at the beam quality used to reduce their energy dependence. Average dose to the lens due to the OBI systems of the Clinac iX and the TrueBeam were 0.71  ±  0.07 mGy/CBCT and 0.70  ±  0.08 mGy/CBCT, respectively. The extra absorbed dose received by the eye lenses due to one CBCT acquisition with the studied protocol is far below the 500 mGy threshold established by ICRP for cataract formation (ICRP 2011 Statement on Tissue Reactions). However, the incremental effect of several CBCT acquisitions during the whole treatment should be taken into account.

Detection and quantification of 223Ra uptake in bone metastases of patients with castration resistant prostate carcinoma, with the aim of determining the absorbed dose in the metastases.

PubMed

Mínguez, P; Gómez de Iturriaga, A; Fernández, I L; Rodeño, E

To obtain the necessary acquisition and calibration parameters in order to evaluate the possibility of detecting and quantifying 223 Ra uptake in bone metastases of patients treated for castration resistant prostate carcinoma. Furthermore, in the cases in which the activity can be quantified, to determine the absorbed dose. Acquisitions from a Petri dish filled with 223 Ra were performed in the gamma camera. Monte Carlo simulations were also performed to study the partial volume effect. Formulae to obtain the detection and quantification limits of 223 Ra uptake were applied to planar images of two patients 7 days post-administration of 55kBq/kg of 223 Ra. In order to locate the lesions in advance, whole-body scans and SPECT/CT images were acquired after injecting 99m Tc-HDP. The optimal energy window was found to be at 82keV with a medium-energy collimator MEGP. Of the lesions found in the patients, only those that had been detected in both the AP and PA projections could be quantified. These lesions were those which had shown a higher 99m Tc-HDP uptake. The estimated values of absorbed doses ranged between 0.7Gy and 7.8Gy. Of the lesions that can be detected, it is not possible to quantify the activity uptake in some of them, which means that the absorbed dose cannot be determined either. This does not mean that the absorbed dose in these lesions can be regarded as negligible. Copyright © 2017 Elsevier España, S.L.U. y SEMNIM. All rights reserved.

Extravasation of radiopharmaceuticals - a study of its frequency and estimation of absorbed doses in diagnosis and therapy

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

Strand, S.E.; Grafstroem, G.; Kontestabile, E.

In all injection procedures exists a risk for extravasation. For radiopharmaceuticals, the absorbed dose at the injection site can be high because of high activity concentrations. In radionuclide therapy (RNT), this can cause deterministic effects such as tissue necrosis. To estimate the risk for extravasation, we studied various injection techniques at two nuclear medicine clinics. The frequency and magnitude of extravasations was studied in randomly selected patients. Clinic A used peripheral venous cathethers (PVC), and clinic B used direct injections with injection needles (IN). At clinic A 203 patients were investigated and at clinic B 90. All of these patientsmore » were injected with either 99mTc-DTPA, 99mTc-MAA, 99mTc-MDP or pertechnetate. Both arms were imaged with a scintillation camera as soon as possible after the injection. In the case of an extravasation, the retention time at the injection site was determined with multiple imaging, together with volume estimates. The results for PVC injected patients showed one complete extravasation. We also found that in 8% of these patients the remaining activity at the injection site was up to 2%. For the IN injected patients there was none with complete extravasation. However, in 33% of these patients the remaining activity was up to 18%. The locally absorbed doses in these diagnostically investigated patients were estimated with the MIRD formalism to be up to 0.1 Sv (10 rem). Transforming these results to the RNT, the absorbed doses can be up to 1000 times higher. In addition to the calculated absorbed doses, radionuclides localizing to the cell nucleus could enhance the effects.« less

Comparison of absorbed-dose-to-water units for Co-60 and high-energy x-rays between PTB and LNE-LNHB

NASA Astrophysics Data System (ADS)

Delaunay, F.; Kapsch, R.-P.; Gouriou, J.; Illemann, J.; Krauss, A.; Le Roy, M.; Ostrowsky, A.; Sommier, L.; Vermesse, D.

2012-10-01

During the Euramet project JRP7 ‘External Beam Cancer Therapy’, PTB and LNE-LNHB used primary standards to determine the absorbed dose to water under IMRT conditions (in small fields). PTB used a water calorimeter to determine the absorbed-dose-to-water references in 6 MV and 10 MV beams for field sizes of 10 cm × 10 cm and 3 cm × 3 cm while LNE-LNHB used graphite calorimeters in 6 MV and 12 MV beams for field sizes of 10 cm × 10 cm, 4 cm × 4 cm and 2 cm × 2 cm. The purpose of this study is to compare PTB and LNE-LNHB new absorbed-dose-to-water references. LNE-LNHB sent an Exradin A1SL ionization chamber traceable to its primary standard to the PTB for calibration in 60Co and in linac beams and PTB sent a PTW 31010 ionization chamber traceable to its primary standard to LNE-LNHB for calibration in 60Co and in linac beams. Calculated Sw,air will be used as beam quality specifier for the ionization chamber comparison at different field sizes. The standard uncertainties (k = 1) of PTB and LNE-LNHB calibration coefficients lie respectively between 0.25% (60Co) and 0.40% (linac) and between 0.29% and 0.46%. PTB and LNE-LNHB absorbed-dose-to-water references developed for this project, based respectively on water calorimetry and on graphite calorimetry, agree within 1.5 standard deviations for field size of 10 cm × 10 cm down to 2 cm × 2 cm and for beams of 6 MV to 10 MV.

Assessment of the actual light dose in photodynamic therapy.

PubMed

Schaberle, Fabio A

2018-06-09

Photodynamic therapy (PDT) initiates with the absorption of light, which depends on the spectral overlap between the light source emission and the photosensitizer absorption, resulting in the number of photons absorbed, the key parameter starting PDT processes. Most papers report light doses regardless if the light is only partially absorbed or shifted relatively to the absorption peak, misleading the actual light dose value and not allowing quantitative comparisons between photosensitizers and light sources. In this manuscript a method is presented to calculate the actual light dose delivered by any light source for a given photosensitizer. This method allows comparing light doses delivered for any combination of light source (broad or narrow band or daylight) and photosensitizer. Copyright © 2018. Published by Elsevier B.V.

Comparison of the ionizing radiation effects on cochineal, annatto and turmeric natural dyes

NASA Astrophysics Data System (ADS)

Cosentino, Helio M.; Takinami, Patricia Y. I.; del Mastro, Nelida L.

2016-07-01

As studies on radiation stability of food dyes are scarce, commercially important natural food grade dyes were evaluated in terms of their sensitivity against gamma ionizing radiation. Cochineal, annatto and turmeric dyes with suitable concentrations were subjected to increasing doses up to 32 kGy and analyzed by spectrophotometry and capillary electrophoresis. The results showed different pattern of absorbance versus absorbed dose for the three systems. Carmine, the glucosidal coloring matter from the scale insect Coccus cacti L., Homoptera (cochineal) remained almost unaffected by radiation up to doses of about 32 kGy (absorbance at 494 nm). Meanwhile, at that dose, a plant-derived product annatto or urucum (Bixa orellana L.) tincture presented a nearly 58% reduction in color intensity. Tincture of curcumin (diferuloylmethane) the active ingredient in the eastern spice turmeric (Curcuma longa) showed to be highly sensitive to radiation when diluted. These data shall be taken in account whenever food products containing these food colors were going to undergo radiation processing.

A feasibility study to calculate unshielded fetal doses to pregnant patients in 6-MV photon treatments using Monte Carlo methods and anatomically realistic phantoms

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

Bednarz, Bryan; Xu, X. George

2008-07-15

A Monte Carlo-based procedure to assess fetal doses from 6-MV external photon beam radiation treatments has been developed to improve upon existing techniques that are based on AAPM Task Group Report 36 published in 1995 [M. Stovall et al., Med. Phys. 22, 63-82 (1995)]. Anatomically realistic models of the pregnant patient representing 3-, 6-, and 9-month gestational stages were implemented into the MCNPX code together with a detailed accelerator model that is capable of simulating scattered and leakage radiation from the accelerator head. Absorbed doses to the fetus were calculated for six different treatment plans for sites above the fetusmore » and one treatment plan for fibrosarcoma in the knee. For treatment plans above the fetus, the fetal doses tended to increase with increasing stage of gestation. This was due to the decrease in distance between the fetal body and field edge with increasing stage of gestation. For the treatment field below the fetus, the absorbed doses tended to decrease with increasing gestational stage of the pregnant patient, due to the increasing size of the fetus and relative constant distance between the field edge and fetal body for each stage. The absorbed doses to the fetus for all treatment plans ranged from a maximum of 30.9 cGy to the 9-month fetus to 1.53 cGy to the 3-month fetus. The study demonstrates the feasibility to accurately determine the absorbed organ doses in the mother and fetus as part of the treatment planning and eventually in risk management.« less

Dosimetric evaluation of nanotargeted (188)Re-liposome with the MIRDOSE3 and OLINDA/EXM programs.

PubMed

Chang, Chih-Hsien; Chang, Ya-Jen; Lee, Te-Wei; Ting, Gann; Chang, Kwo-Ping

2012-06-01

The OLINDA/EXM computer code was created as a replacement for the widely used MIRDOSE3 code for radiation dosimetry in nuclear medicine. A dosimetric analysis with these codes was performed to evaluate nanoliposomes as carriers of radionuclides ((188)Re-liposomes) in colon carcinoma-bearing mice. Pharmacokinetic data for (188)Re-N, N-bis (2-mercaptoethyl)-N',N'-diethylethylenediamine ((188)Re-BMEDA) and (188)Re-liposome were obtained for estimation of absorbed doses in normal organs. Radiation dose estimates for normal tissues were calculated using the MIRDOSE3 and OLINDA/EXM programs for a colon carcinoma solid tumor mouse model. Mean absorbed doses derived from(188)Re-BMEDA and (188)Re-liposome in normal tissues were generally similar as calculated by MIRDOSE3 and OLINDA/EXM programs. One notable exception to this was red marrow, wherein MIRDOSE3 resulted in higher absorbed doses than OLINDA/EXM (1.53- and 1.60-fold for (188)Re-BMEDA and (188)Re-liposome, respectively). MIRDOSE3 and OLINDA have very similar residence times and organ doses. Bone marrow doses were estimated by designating cortical bone rather than bone marrow as a source organ. The bone marrow doses calculated by MIRDOSE3 are higher than those by OLINDA. If the bone marrow is designated as a source organ, the doses estimated by MIRDOSE3 and OLINDA programs will be very similar.

Image quality and absorbed dose comparison of single- and dual-source cone-beam computed tomography.

PubMed

Miura, Hideharu; Ozawa, Shuichi; Okazue, Toshiya; Kawakubo, Atsushi; Yamada, Kiyoshi; Nagata, Yasushi

2018-05-01

Dual-source cone-beam computed tomography (DCBCT) is currently available in the Vero4DRT image-guided radiotherapy system. We evaluated the image quality and absorbed dose for DCBCT and compared the values with those for single-source CBCT (SCBCT). Image uniformity, Hounsfield unit (HU) linearity, image contrast, and spatial resolution were evaluated using a Catphan phantom. The rotation angle for acquiring SCBCT and DCBCT images is 215° and 115°, respectively. The image uniformity was calculated using measurements obtained at the center and four peripheral positions. The HUs of seven materials inserted into the phantom were measured to evaluate HU linearity and image contrast. The Catphan phantom was scanned with a conventional CT scanner to measure the reference HU for each material. The spatial resolution was calculated using high-resolution pattern modules. Image quality was analyzed using ImageJ software ver. 1.49. The absorbed dose was measured using a 0.6-cm 3 ionization chamber with a 16-cm-diameter cylindrical phantom, at the center and four peripheral positions of the phantom, and calculated using weighted cone-beam CT dose index (CBCTDI w ). Compared with that of SCBCT, the image uniformity of DCBCT was slightly reduced. A strong linear correlation existed between the measured HU for DCBCT and the reference HU, although the linear regression slope was different from that of the reference HU. DCBCT had poorer image contrast than did SCBCT, particularly with a high-contrast material. There was no significant difference between the spatial resolutions of SCBCT and DCBCT. The absorbed dose for DCBCT was higher than that for SCBCT, because in DCBCT, the two x-ray projections overlap between 45° and 70°. We found that the image quality was poorer and the absorbed dose was higher for DCBCT than for SCBCT in the Vero4DRT. © 2018 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

A modified microdosimetric kinetic model for relative biological effectiveness calculation

NASA Astrophysics Data System (ADS)

Chen, Yizheng; Li, Junli; Li, Chunyan; Qiu, Rui; Wu, Zhen

2018-01-01

In the heavy ion therapy, not only the distribution of physical absorbed dose, but also the relative biological effectiveness (RBE) weighted dose needs to be taken into account. The microdosimetric kinetic model (MKM) can predict the RBE value of heavy ions with saturation-corrected dose-mean specific energy, which has been used in clinical treatment planning at the National Institute of Radiological Sciences. In the theoretical assumption of the MKM, the yield of the primary lesion is independent of the radiation quality, while the experimental data shows that DNA double strand break (DSB) yield, considered as the main primary lesion, depends on the LET of the particle. Besides, the β parameter of the MKM is constant with LET resulting from this assumption, which also differs from the experimental conclusion. In this study, a modified MKM was developed, named MMKM. Based on the experimental DSB yield of mammalian cells under the irradiation of ions with different LETs, a RBEDSB (RBE for the induction of DSB)-LET curve was fitted as the correction factor to modify the primary lesion yield in the MKM, and the variation of the primary lesion yield with LET is considered in the MMKM. Compared with the present the MKM, not only the α parameter of the MMKM for mono-energetic ions agree with the experimental data, but also the β parameter varies with LET and the variation trend of the experimental result can be reproduced on the whole. Then a spread-out Bragg peaks (SOBP) distribution of physical dose was simulated with Geant4 Monte Carlo code, and the biological and clinical dose distributions were calculated, under the irradiation of carbon ions. The results show that the distribution of clinical dose calculated with the MMKM is closed to the distribution with the MKM in the SOBP, while the discrepancy before and after the SOBP are both within 10%. Moreover, the MKM might overestimate the clinical dose at the distal end of the SOBP more than 5% because of its constant β value, while a minimal value of β is calculated with the MMKM at this position. Besides, the discrepancy of the averaged cell survival fraction in the SOBP calculated with the two models is more than 15% at the high dose level. The MMKM may provide a reference for the accurate calculation of the RBE value in heavy ion therapy.

Gamma ray induced decomposition of double nitrates of lanthanum and cerium with some mono and bivalent cations in solid state

NASA Astrophysics Data System (ADS)

Kulkarni, S. P.; Garg, A. N.

Gamma ray induced decomposition of two series of double nitrates; 2M INO 3⋯Ln(NO 3) 3⋯ x H 2O (where MI = NH+4, Na+, K+, Rb+, Cs+; LnIII = La3+, Ce3+ and x = 2 or 4) and 3M II(NO 3) 2·2Ln III(NO 3) 3⋯24H 2O (where MII = Mg2+, Co2+, Zn2+; LnIII = La3+, Ce3+) has been studied in solid state over a wide absorbed dose range at room temperature. G(NO -2) values have been found to depend on the absorbed dose and the nature of cation in both the series of double salts. Radiation sensitivity of lanthanum double nitrates with monovalent cations at an absorbed dose of 158 kGy follows the order NH +4 < Rb + ≅ Cs + < Na + < K + and those of cerium NH +4 < Rb +

Comparative dosimetric evaluation of nanotargeted (188)Re-(DXR)-liposome for internal radiotherapy.

PubMed

Chang, Chih-Hsien; Stabin, Michael G; Chang, Ya-Jen; Chen, Liang-Cheng; Chen, Min-Hua; Chang, Tsui-Jung; Lee, Te-Wei; Ting, Gann

2008-12-01

A dosimetric analysis was performed to evaluate nanoliposomes as carriers of radionuclides ((188)Re-liposomes) and radiochemotherapeutic drugs [(188)Re-doxorubicin (DXR)-liposomes] in internal radiotherapy for colon carcinoma, as evaluated in mice. Pharmacokinetic data for (188)Re-N, N-bis (2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA), (188)Re-liposome, and (188)Re-DXR-liposome were obtained for the estimation of absorbed doses in tumors and normal organs. Two colon carcinoma mouse models were employed: subcutaneous growing solid tumor and malignant ascites pervading tumor models. Radiation-dose estimates for normal tissues and tumors were calculated by using the OLINDA/EXM program. An evaluation of a recommended maximum administered activity (MAA) for the nanotargeted drugs was also made. Mean absorbed doses derived from (188)Re-liposome and (188)Re-DXR-liposome in normal tissues were generally similar to those from (188)Re-BMEDA in intraperitoneal and intravenous administration. Tissue-absorbed dose in the liver was 0.24-0.40 and 0.17-0.26 (mGy/MBq) and in red marrow was 0.033-0.050 and 0.038-0.046 (mGy/MBq), respectively, for (188)Re-liposome and (188)Re-DXR-liposome. Tumor-absorbed doses for the nanotargeted (188)Re-liposome and (188)Re-DXR-liposome were higher than those of (188)Re-BMEDA for both routes of administration (4-26-fold). Dose to red marrow defined the recommended MAA. Our results suggest that radionuclide and chemoradiotherapeutic passive targeting delivery, using nanoliposomes as the carrier, is feasible and promising in systemic-targeted radionuclide therapy.

[The main radionuclides and dose formation in fish of the Chernobyl NPP exclusion zone].

PubMed

Gudkov, D I; Kaglian, A E; Kireev, S I; Nazarov, A B; Klenus, V G

2008-01-01

The results of the researches of spices-specificity, accumulation dynamics and distribution of 90Sr, of 137Cs and of transuranic elements in fish of the Chernobyl NPP exclusion zone are analysed. The data of estimations of absorbed doze rate from incorporated radionuclides for pray fish and predatory species are given. For the fish from the lake of the left-bank floodplain of the Pripyat River the increase of 90Sr specific activity is registered which is presumably connected with the dynamics of the physical-chemical forms of the radionuclide in soils and their wash out in water bodies from the catchment basin. Now about 90% of internal dose rate of fish from closed aquatic ecosystems within the Chernobyl NPP exclusion zone is caused by 90Sr incorporation.

The effect of poorly absorbed solute on intestinal absorption.

PubMed

Menzies, I S; Jenkins, A P; Heduan, E; Catt, S D; Segal, M B; Creamer, B

1990-12-01

To determine the effects of poorly absorbed solute on intestinal absorption, the urinary recovery of ingested lactulose, L-rhamnose, D-xylose, and 3-O-methyl-D-glucose was measured after simultaneous ingestion of various 'loads' of mannitol given in iso-osmolar solution. Mannitol reduced intestinal uptake of the poorly absorbed test sugars, lactulose and L-rhamnose; uptake of D-xylose and 3-O-methyl-D-glucose, which are absorbed by carrier-mediated transport largely from the jejunum, was less affected. The dose-response effect of mannitol on the absorption of L-rhamnose was approximately exponential; doses of 5, 10, and 20 g mannitol reduced the average urinary excretion of L-rhamnose by 34.7%, 51.7%, and 61.2%, respectively. In this respect, an osmotically equivalent load of lactulose, ingested as 'solute', was approximately twice as effective as mannitol in reducing L-rhamnose absorption, probably because lactulose is more poorly absorbed than mannitol (less than 1.0% versus 32-41%). Ingestion of other poorly absorbed solutes such as raffinose, sorbitol, xylitol, magnesium sulphate, and sodium sulphate also significantly depressed the absorption of L-rhamnose; in contrast, more efficiently absorbed solutes, such as sodium chloride, glucose, glycerol, and urea had little effect.

The impact of emollients on phototherapy: a review.

PubMed

Asztalos, Manuela L; Heller, Misha M; Lee, Eric S; Koo, John

2013-05-01

When treating psoriasis, various topical emollients exist that can affect the penetration of ultraviolet radiation in phototherapy. Compared with normal-appearing skin with a reflectance of 4% to 5%, psoriatic skin has higher reflectance as a result of its increased air-to-corneocyte interfaces. Studies have tested the effect of emollients on light penetration by assessing psoriatic plaque clearance, differences in minimal erythema dose, and physical properties of the emollient (eg, monochromatic protection factor and absorbance). Psoriatic plaque clearance was found to improve with serous (thin liquid)-based emollients (eg, Vaseline oil [Unilever, Blackfriars, London, UK], mineral oil, and glycerol), whereas clearance decreased with salicylic acid and viscous-based emollients (eg, petrolatum). Emollients with high ultraviolet absorbance properties increased minimal erythema dose, and those with low absorbance properties decreased minimal erythema dose. Interestingly, when a liquid emollient with a refractive index close to that of normal-appearing skin was applied, there was a net increase in light absorption, or a reduction in reflection that exceeded the emollient's innate ability to absorb light. Copyright © 2012 American Academy of Dermatology, Inc. Published by Mosby, Inc. All rights reserved.

Estimation of absorbed doses from paediatric cone-beam CT scans: MOSFET measurements and Monte Carlo simulations.

PubMed

Kim, Sangroh; Yoshizumi, Terry T; Toncheva, Greta; Frush, Donald P; Yin, Fang-Fang

2010-03-01

The purpose of this study was to establish a dose estimation tool with Monte Carlo (MC) simulations. A 5-y-old paediatric anthropomorphic phantom was computed tomography (CT) scanned to create a voxelised phantom and used as an input for the abdominal cone-beam CT in a BEAMnrc/EGSnrc MC system. An X-ray tube model of the Varian On-Board Imager((R)) was built in the MC system. To validate the model, the absorbed doses at each organ location for standard-dose and low-dose modes were measured in the physical phantom with MOSFET detectors; effective doses were also calculated. In the results, the MC simulations were comparable to the MOSFET measurements. This voxelised phantom approach could produce a more accurate dose estimation than the stylised phantom method. This model can be easily applied to multi-detector CT dosimetry.

Internal dosimetry with the Monte Carlo code GATE: validation using the ICRP/ICRU female reference computational model

NASA Astrophysics Data System (ADS)

Villoing, Daphnée; Marcatili, Sara; Garcia, Marie-Paule; Bardiès, Manuel

2017-03-01

The purpose of this work was to validate GATE-based clinical scale absorbed dose calculations in nuclear medicine dosimetry. GATE (version 6.2) and MCNPX (version 2.7.a) were used to derive dosimetric parameters (absorbed fractions, specific absorbed fractions and S-values) for the reference female computational model proposed by the International Commission on Radiological Protection in ICRP report 110. Monoenergetic photons and electrons (from 50 keV to 2 MeV) and four isotopes currently used in nuclear medicine (fluorine-18, lutetium-177, iodine-131 and yttrium-90) were investigated. Absorbed fractions, specific absorbed fractions and S-values were generated with GATE and MCNPX for 12 regions of interest in the ICRP 110 female computational model, thereby leading to 144 source/target pair configurations. Relative differences between GATE and MCNPX obtained in specific configurations (self-irradiation or cross-irradiation) are presented. Relative differences in absorbed fractions, specific absorbed fractions or S-values are below 10%, and in most cases less than 5%. Dosimetric results generated with GATE for the 12 volumes of interest are available as supplemental data. GATE can be safely used for radiopharmaceutical dosimetry at the clinical scale. This makes GATE a viable option for Monte Carlo modelling of both imaging and absorbed dose in nuclear medicine.

Pharmacokinetics in Wistar Rats of 5-[(4-Carboxybutanoyl)Amino]-2-Hydroxybenzoic Acid: A Novel Synthetic Derivative of 5-Aminosalicylic Acid (5-ASA) with Possible Anti-Inflammatory Activity

PubMed Central

Correa-Basurto, José; Rosales Hernández, Martha Cecilia; Padilla Martínez, Itzia Irene; Mendieta-Wejebe, Jessica Elena

2016-01-01

5-[(4-carboxybutanoyl)amino]-2-hydroxybenzoic acid (C2) is a novel synthetic derivative of 5-aminosalicylic acid (5-ASA), which is currently being evaluated ex vivo as an anti-inflammatory agent and has shown satisfactory results. This study aimed to obtain the pharmacokinetic profiles, tissue distribution and plasma protein binding of C2 in Wistar Rats. Additionally, an HPLC method was developed and validated to quantify C2 in rat plasma. The pharmacokinetic profiles of intragastric, intravenous and intraperitoneal administration routes at singles doses of 100, 50, and 100 mg/kg, respectively, were studied in Wistar rats. The elimination half-life of intravenously administered C2 was approximately 33 min. The maximum plasma level of C2 was reached approximately 24 min after intragastric administration, with a Cmax value of 2.5 g/mL and an AUCtot value of 157 μg min-1/mL; the oral bioavailability was approximately 13%. Following a single intragastric or oral dose (100 mg/kg), C2 was distributed and detected in all examined tissues (including the brain and colon). The results showed that C2 accumulates over time. The plasma protein binding results indicated that the unbound fraction of C2 at concentrations of 1 to 20 μg/mL ranged from 89.8% to 92.5%, meaning that this fraction of C2 is available to cross tissues. Finally, the blood-plasma partitioning (BP ratio) of C2 in rat plasma was 0.71 and 0.6 at concentrations of 5 and 10 μg/mL, respectively, which indicates that C2 is free in the plasmatic phase and not inside blood cells. The results of this study suggest that a fraction of the administered C2 dose is absorbed in the stomach, and the fraction that is not absorbed reaches the small intestine and colon. This distribution constitutes the main advantage of C2 compared with 5-ASA for the treatment of ulcerative colitis (UC) and Crohn's disease (CD). PMID:27454774

Unglazed transpired solar collector having a low thermal-conductance absorber

DOEpatents

Christensen, Craig B.; Kutscher, Charles F.; Gawlik, Keith M.

1997-01-01

An unglazed transpired solar collector using solar radiation to heat incoming air for distribution, comprising an unglazed absorber formed of low thermal-conductance material having a front surface for receiving the solar radiation and openings in the unglazed absorber for passage of the incoming air such that the incoming air is heated as it passes towards the front surface of the absorber and the heated air passes through the openings in the absorber for distribution.

Unglazed transpired solar collector having a low thermal-conductance absorber

DOEpatents

Christensen, C.B.; Kutscher, C.F.; Gawlik, K.M.

1997-12-02

An unglazed transpired solar collector using solar radiation to heat incoming air for distribution, comprises an unglazed absorber formed of low thermal-conductance material having a front surface for receiving the solar radiation and openings in the unglazed absorber for passage of the incoming air such that the incoming air is heated as it passes towards the front surface of the absorber and the heated air passes through the openings in the absorber for distribution. 3 figs.

Patient dose, gray level and exposure index with a computed radiography system

NASA Astrophysics Data System (ADS)

Silva, T. R.; Yoshimura, E. M.

2014-02-01

Computed radiography (CR) is gradually replacing conventional screen-film system in Brazil. To assess image quality, manufactures provide the calculation of an exposure index through the acquisition software of the CR system. The objective of this study is to verify if the CR image can be used as an evaluator of patient absorbed dose too, through a relationship between the entrance skin dose and the exposure index or the gray level values obtained in the image. The CR system used for this study (Agfa model 30-X with NX acquisition software) calculates an exposure index called Log of the Median (lgM), related to the absorbed dose to the IP. The lgM value depends on the average gray level (called Scan Average Level (SAL)) of the segmented pixel value histogram of the whole image. A Rando male phantom was used to simulate a human body (chest and head), and was irradiated with an X-ray equipment, using usual radiologic techniques for chest exams. Thermoluminescent dosimeters (LiF, TLD100) were used to evaluate entrance skin dose and exit dose. The results showed a logarithm relation between entrance dose and SAL in the image center, regardless of the beam filtration. The exposure index varies linearly with the entrance dose, but the angular coefficient is beam quality dependent. We conclude that, with an adequate calibration, the CR system can be used to evaluate the patient absorbed dose.

Calculation of Absorbed Dose in Target Tissue and Equivalent Dose in Sensitive Tissues of Patients Treated by BNCT Using MCNP4C

NASA Astrophysics Data System (ADS)

Zamani, M.; Kasesaz, Y.; Khalafi, H.; Pooya, S. M. Hosseini

Boron Neutron Capture Therapy (BNCT) is used for treatment of many diseases, including brain tumors, in many medical centers. In this method, a target area (e.g., head of patient) is irradiated by some optimized and suitable neutron fields such as research nuclear reactors. Aiming at protection of healthy tissues which are located in the vicinity of irradiated tissue, and based on the ALARA principle, it is required to prevent unnecessary exposure of these vital organs. In this study, by using numerical simulation method (MCNP4C Code), the absorbed dose in target tissue and the equiavalent dose in different sensitive tissues of a patiant treated by BNCT, are calculated. For this purpose, we have used the parameters of MIRD Standard Phantom. Equiavelent dose in 11 sensitive organs, located in the vicinity of target, and total equivalent dose in whole body, have been calculated. The results show that the absorbed dose in tumor and normal tissue of brain equal to 30.35 Gy and 0.19 Gy, respectively. Also, total equivalent dose in 11 sensitive organs, other than tumor and normal tissue of brain, is equal to 14 mGy. The maximum equivalent doses in organs, other than brain and tumor, appear to the tissues of lungs and thyroid and are equal to 7.35 mSv and 3.00 mSv, respectively.

Imaging tooth enamel using zero echo time (ZTE) magnetic resonance imaging

NASA Astrophysics Data System (ADS)

Rychert, Kevin M.; Zhu, Gang; Kmiec, Maciej M.; Nemani, Venkata K.; Williams, Benjamin B.; Flood, Ann B.; Swartz, Harold M.; Gimi, Barjor

2015-03-01

In an event where many thousands of people may have been exposed to levels of radiation that are sufficient to cause the acute radiation syndrome, we need technology that can estimate the absorbed dose on an individual basis for triage and meaningful medical decision making. Such dose estimates may be achieved using in vivo electron paramagnetic resonance (EPR) tooth biodosimetry, which measures the number of persistent free radicals that are generated in tooth enamel following irradiation. However, the accuracy of dose estimates may be impacted by individual variations in teeth, especially the amount and distribution of enamel in the inhomogeneous sensitive volume of the resonator used to detect the radicals. In order to study the relationship between interpersonal variations in enamel and EPR-based dose estimates, it is desirable to estimate these parameters nondestructively and without adding radiation to the teeth. Magnetic Resonance Imaging (MRI) is capable of acquiring structural and biochemical information without imparting additional radiation, which may be beneficial for many EPR dosimetry studies. However, the extremely short T2 relaxation time in tooth structures precludes tooth imaging using conventional MRI methods. Therefore, we used zero echo time (ZTE) MRI to image teeth ex vivo to assess enamel volumes and spatial distributions. Using these data in combination with the data on the distribution of the transverse radio frequency magnetic field from electromagnetic simulations, we then can identify possible sources of variations in radiation-induced signals detectable by EPR. Unlike conventional MRI, ZTE applies spatial encoding gradients during the RF excitation pulse, thereby facilitating signal acquisition almost immediately after excitation, minimizing signal loss from short T2 relaxation times. ZTE successfully provided volumetric measures of tooth enamel that may be related to variations that impact EPR dosimetry and facilitate the development of analytical procedures for individual dose estimates.

Study of the absorption spectra of Fricke Xylenol Orange gel dosimeters

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

Gambarini, Grazia; Artuso, Emanuele; Liosi, Giulia Maria

2015-07-01

A systematic study of the absorption spectra of Fricke Xylenol Orange gel dosimeters has been performed, in the wavelength range from 300 nm to 700 nm. The spectrum of Xylenol Orange (without ferrous sulphate solution) has been achieved, in order to subtract its contribution from the absorption spectra of the irradiated Fricke Xylenol Orange gel dosimeters. The absorbance due to ferric ions chelated by Xylenol Orange has been studied for various irradiation doses. Two absorbance peaks are visible, mainly at low doses: the first peak increases with the dose more slowly than the second one. This effect can explain themore » apparent threshold dose that was frequently evidenced. (authors)« less

Absorbed dose evaluation of Auger electron-emitting radionuclides: impact of input decay spectra on dose point kernels and S-values

NASA Astrophysics Data System (ADS)

Falzone, Nadia; Lee, Boon Q.; Fernández-Varea, José M.; Kartsonaki, Christiana; Stuchbery, Andrew E.; Kibédi, Tibor; Vallis, Katherine A.

2017-03-01

The aim of this study was to investigate the impact of decay data provided by the newly developed stochastic atomic relaxation model BrIccEmis on dose point kernels (DPKs - radial dose distribution around a unit point source) and S-values (absorbed dose per unit cumulated activity) of 14 Auger electron (AE) emitting radionuclides, namely 67Ga, 80mBr, 89Zr, 90Nb, 99mTc, 111In, 117mSn, 119Sb, 123I, 124I, 125I, 135La, 195mPt and 201Tl. Radiation spectra were based on the nuclear decay data from the medical internal radiation dose (MIRD) RADTABS program and the BrIccEmis code, assuming both an isolated-atom and condensed-phase approach. DPKs were simulated with the PENELOPE Monte Carlo (MC) code using event-by-event electron and photon transport. S-values for concentric spherical cells of various sizes were derived from these DPKs using appropriate geometric reduction factors. The number of Auger and Coster-Kronig (CK) electrons and x-ray photons released per nuclear decay (yield) from MIRD-RADTABS were consistently higher than those calculated using BrIccEmis. DPKs for the electron spectra from BrIccEmis were considerably different from MIRD-RADTABS in the first few hundred nanometres from a point source where most of the Auger electrons are stopped. S-values were, however, not significantly impacted as the differences in DPKs in the sub-micrometre dimension were quickly diminished in larger dimensions. Overestimation in the total AE energy output by MIRD-RADTABS leads to higher predicted energy deposition by AE emitting radionuclides, especially in the immediate vicinity of the decaying radionuclides. This should be taken into account when MIRD-RADTABS data are used to simulate biological damage at nanoscale dimensions.

Coupling Monte Carlo simulations with thermal analysis for correcting microdosimetric spectra from a novel micro-calorimeter

NASA Astrophysics Data System (ADS)

Fathi, K.; Galer, S.; Kirkby, K. J.; Palmans, H.; Nisbet, A.

2017-11-01

The high uncertainty in the Relative Biological Effectiveness (RBE) values of particle therapy beam, which are used in combination with the quantity absorbed dose in radiotherapy, together with the increase in the number of particle therapy centres worldwide necessitate a better understating of the biological effect of such modalities. The present novel study is part of performance testing and development of a micro-calorimeter based on Superconducting QUantum Interference Devices (SQUIDs). Unlike other microdosimetric detectors that are used for investigating the energy distribution, this detector provides a direct measurement of energy deposition at the micrometre scale, that can be used to improve our understanding of biological effects in particle therapy application, radiation protection and environmental dosimetry. Temperature rises of less than 1μK are detectable and when combined with the low specific heat capacity of the absorber at cryogenic temperature, extremely high energy deposition sensitivity of approximately 0.4 eV can be achieved. The detector consists of 3 layers: tissue equivalent (TE) absorber, superconducting (SC) absorber and silicon substrate. Ideally all energy would be absorbed in the TE absorber and heat rise in the superconducting layer would arise due to heat conduction from the TE layer. However, in practice direct particle absorption occurs in all 3 layers and must be corrected for. To investigate the thermal behaviour within the detector, and quantify any possible correction, particle tracks were simulated employing Geant4 (v9.6) Monte Carlo simulations. The track information was then passed to the COMSOL Multiphysics (Finite Element Method) software. The 3D heat transfer within each layer was then evaluated in a time-dependent model. For a statistically reliable outcome, the simulations had to be repeated for a large number of particles. An automated system has been developed that couples Geant4 Monte Carlo output to COMSOL for determining the expected distribution of proton tracks and their thermal contribution within the detector. The correction factor for a 3.8 MeV proton pencil beam was determined and applied to the expected spectra. The corrected microdosimetric spectra was shown to have a good agreement with the ideal spectra.

Dose equations for tube current modulation in CT scanning and the interpretation of the associated CTDI{sub vol}

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

Dixon, Robert L.; Boone, John M.

2013-11-15

Purpose: The scanner-reported CTDI{sub vol} for automatic tube current modulation (TCM) has a different physical meaning from the traditional CTDI{sub vol} at constant mA, resulting in the dichotomy “CTDI{sub vol} of the first and second kinds” for which a physical interpretation is sought in hopes of establishing some commonality between the two.Methods: Rigorous equations are derived to describe the accumulated dose distributions for TCM. A comparison with formulae for scanner-reported CTDI{sub vol} clearly identifies the source of their differences. Graphical dose simulations are also provided for a variety of TCM tube current distributions (including constant mA), all having the samemore » scanner-reported CTDI{sub vol}.Results: These convolution equations and simulations show that the local dose at z depends only weakly on the local tube current i(z) due to the strong influence of scatter from all other locations along z, and that the “local CTDI{sub vol}(z)” does not represent a local dose but rather only a relative i(z) ≡ mA(z). TCM is a shift-variant technique to which the CTDI-paradigm does not apply and its application to TCM leads to a CTDI{sub vol} of the second kind which lacks relevance.Conclusions: While the traditional CTDI{sub vol} at constant mA conveys useful information (the peak dose at the center of the scan length), CTDI{sub vol} of the second kind conveys no useful information about the associated TCM dose distribution it purportedly represents and its physical interpretation remains elusive. On the other hand, the total energy absorbed E (“integral dose”) as well as its surrogate DLP remain robust between variable i(z) TCM and constant current i{sub 0} techniques, both depending only on the total mAs = t{sub 0}=i{sub 0} t{sub 0} during the beam-on time t{sub 0}.« less

Effect of Gold Nanoparticles on Prostate Dose Distribution under Ir-192 Internal and 18 MV External Radiotherapy Procedures Using Gel Dosimetry and Monte Carlo Method.

PubMed

Khosravi, H; Hashemi, B; Mahdavi, S R; Hejazi, P

2015-03-01

Gel polymers are considered as new dosimeters for determining radiotherapy dose distribution in three dimensions. The ability of a new formulation of MAGIC-f polymer gel was assessed by experimental measurement and Monte Carlo (MC) method for studying the effect of gold nanoparticles (GNPs) in prostate dose distributions under the internal Ir-192 and external 18MV radiotherapy practices. A Plexiglas phantom was made representing human pelvis. The GNP shaving 15 nm in diameter and 0.1 mM concentration were synthesized using chemical reduction method. Then, a new formulation of MAGIC-f gel was synthesized. The fabricated gel was poured in the tubes located at the prostate (with and without the GNPs) and bladder locations of the phantom. The phantom was irradiated to an Ir-192 source and 18 MV beam of a Varian linac separately based on common radiotherapy procedures used for prostate cancer. After 24 hours, the irradiated gels were read using a Siemens 1.5 Tesla MRI scanner. The absolute doses at the reference points and isodose curves resulted from the experimental measurement of the gels and MC simulations following the internal and external radiotherapy practices were compared. The mean absorbed doses measured with the gel in the presence of the GNPs in prostate were 15% and 8 % higher than the corresponding values without the GNPs under the internal and external radiation therapies, respectively. MC simulations also indicated a dose increase of 14 % and 7 % due to presence of the GNPs, for the same experimental internal and external radiotherapy practices, respectively. There was a good agreement between the dose enhancement factors (DEFs) estimated with MC simulations and experiment gel measurements due to the GNPs. The results indicated that the polymer gel dosimetry method as developed and used in this study, can be recommended as a reliable method for investigating the DEF of GNPs in internal and external radiotherapy practices.

SU-F-T-477: Investigation of DEFGEL Dosimetry Using MRI

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

Matrosic, C; McMillan, A; Bednarz, B

Purpose: The DEFGEL dosimeter/phantom allows for the measurement of 3D dose distributions while maintaining tissue equivalence and deformability. Although DEFGEL is traditionally read out with optical CT, the use of MRI would permit the measurement of 3D dose distributions in optically interfering configurations, like while embedded in a phantom. To the knowledge of the authors, this work is the first investigation that uses MRI to measure dose distributions in DEFGEL dosimeters. Methods: The DEFGEL (6%T) formula was used to create 1 cm thick, 4.5 cm diameter cylindrical dosimeters. The dosimeters were irradiated using a Varian Clinac 21EX linac. The MRImore » based transverse relaxation rate (R2) of the gel was measured in a central slice of the dosimeter with a Spin-Echo (SE) pulse sequence on a 3T GE SIGNA PET/MR scanner. The R2 values were fit to a monoexponential dose response equation using in-house software (MATLAB). Results: The data was well fit using a monoexponential fit for R2 as a function of absorbed dose (R{sup 2} = 0.9997). The fitting parameters of the monoexponential fit resulted in a 0.1229 Gy{sub −1}s{sub −1} slope. The data also resulted in an average standard deviation of 1.8% for the R2 values within the evaluated ROI. Conclusion: The close fit for the dose response curve shows that a DEFGEL based dosimeter can be paired with a SE MRI acquisition. The Type A uncertainty of the MRI method shows adequate precision, while the slope of the fit curve is large enough that R2 differences between different gel doses are distinguishable. These results suggest that the gel could potentially be used in configurations where an optical readout is not viable, such as measurements with the gel dosimeter positioned inside larger or optically opaque phantoms. This work is partially funded by NIH grant R01CA190298.« less

Posture-specific phantoms representing female and male adults in Monte Carlo-based simulations for radiological protection

NASA Astrophysics Data System (ADS)

Cassola, V. F.; Kramer, R.; Brayner, C.; Khoury, H. J.

2010-08-01

Does the posture of a patient have an effect on the organ and tissue absorbed doses caused by x-ray examinations? This study aims to find the answer to this question, based on Monte Carlo (MC) simulations of commonly performed x-ray examinations using adult phantoms modelled to represent humans in standing as well as in the supine posture. The recently published FASH (female adult mesh) and MASH (male adult mesh) phantoms have the standing posture. In a first step, both phantoms were updated with respect to their anatomy: glandular tissue was separated from adipose tissue in the breasts, visceral fat was separated from subcutaneous fat, cartilage was segmented in ears, nose and around the thyroid, and the mass of the right lung is now 15% greater than the left lung. The updated versions are called FASH2_sta and MASH2_sta (sta = standing). Taking into account the gravitational effects on organ position and fat distribution, supine versions of the FASH2 and the MASH2 phantoms have been developed in this study and called FASH2_sup and MASH2_sup. MC simulations of external whole-body exposure to monoenergetic photons and partial-body exposure to x-rays have been made with the standing and supine FASH2 and MASH2 phantoms. For external whole-body exposure for AP and PA projection with photon energies above 30 keV, the effective dose did not change by more than 5% when the posture changed from standing to supine or vice versa. Apart from that, the supine posture is quite rare in occupational radiation protection from whole-body exposure. However, in the x-ray diagnosis supine posture is frequently used for patients submitted to examinations. Changes of organ absorbed doses up to 60% were found for simulations of chest and abdomen radiographs if the posture changed from standing to supine or vice versa. A further increase of differences between posture-specific organ and tissue absorbed doses with increasing whole-body mass is to be expected.

Radiological assessment of target materials for accelerator transmutation of waste (ATW) applications

NASA Astrophysics Data System (ADS)

Vickers, Linda Diane

This dissertation issues the first published document of the radiation absorbed dose rate (rad-h-1) to tissue from radioactive spallation products in Ta, W, Pb, Bi, and LBE target materials used in Accelerator Transmutation of Waste (ATW) applications. No previous works have provided an estimate of the absorbed dose rate (rad-h-1) from activated targets for ATW applications. The results of this dissertation are useful for planning the radiological safety assessment to personnel, and for the design, construction, maintenance, and disposition of target materials of high-energy particle accelerators for ATW applications (Charlton, 1996). In addition, this dissertation provides the characterization of target materials of high-energy particle accelerators for the parameters of: (1) spallation neutron yield (neutrons/proton), (2) spallation products yield (nuclides/proton), (3) energy-dependent spallation neutron fluence distribution, (4) spallation neutron flux, (5) identification of radioactive spallation products for consideration in safety of personnel to high radiation dose rates, and (6) identification of the optimum geometrical dimensions for the target applicable to the maximum radial spallation neutron leakage from the target. Pb and Bi target materials yielded the lowest absorbed dose rates (rad-h -1) for a 10-year irradiation/50-year decay scheme, and would be the preferred target materials for consideration of the radiological safety of personnel during ATW operations. A beneficial characteristic of these target materials is that they do not produce radioactive transuranic isotopes, which have very long half-lives and require special handling and disposition requirements. Furthermore, the targets are not considered High-Level Waste (HLW) such as reactor spent fuel for disposal purposes. It is a basic ATW system requirement that the spallation target after it has been expended should be disposable as Class C low-level radioactive waste. Therefore, the disposal of Pb and Bi targets would be optimally beneficial to the economy and environment. Future studies should relate the target performance to other system parameters, specifically solid and liquid blanket systems that contain the radioactive waste to be transmuted. The methodology of this dissertation may be applied to any target material of a high-energy particle accelerator.

Comparative Monte Carlo study on the performance of integration- and list-mode detector configurations for carbon ion computed tomography

NASA Astrophysics Data System (ADS)

Meyer, Sebastian; Gianoli, Chiara; Magallanes, Lorena; Kopp, Benedikt; Tessonnier, Thomas; Landry, Guillaume; Dedes, George; Voss, Bernd; Parodi, Katia

2017-02-01

Ion beam therapy offers the possibility of a highly conformal tumor-dose distribution; however, this technique is extremely sensitive to inaccuracies in the treatment procedures. Ambiguities in the conversion of Hounsfield units of the treatment planning x-ray CT to relative stopping power (RSP) can cause uncertainties in the estimated ion range of up to several millimeters. Ion CT (iCT) represents a favorable solution allowing to directly assess the RSP. In this simulation study we investigate the performance of the integration-mode configuration for carbon iCT, in comparison with a single-particle approach under the same set-up. The experimental detector consists of a stack of 61 air-filled parallel-plate ionization chambers, interleaved with 3 mm thick PMMA absorbers. By means of Monte Carlo simulations, this design was applied to acquire iCTs of phantoms of tissue-equivalent materials. An optimization of the acquisition parameters was performed to reduce the dose exposure, and the implications of a reduced absorber thickness were assessed. In order to overcome limitations of integration-mode detection in the presence of lateral tissue heterogeneities a dedicated post-processing method using a linear decomposition of the detector signal was developed and its performance was compared to the list-mode acquisition. For the current set-up, the phantom dose could be reduced to below 30 mGy with only minor image quality degradation. By using the decomposition method a correct identification of the components and a RSP accuracy improvement of around 2.0% was obtained. The comparison of integration- and list-mode indicated a slightly better image quality of the latter, with an average median RSP error below 1.8% and 1.0%, respectively. With a decreased absorber thickness a reduced RSP error was observed. Overall, these findings support the potential of iCT for low dose RSP estimation, showing that integration-mode detectors with dedicated post-processing strategies can provide a RSP accuracy comparable to list-mode configurations.

42 CFR 81.4 - Definition of terms used in this part.

Code of Federal Regulations, 2011 CFR

2011-10-01

...]. (e) Equivalent dose means the absorbed dose in a tissue or organ multiplied by a radiation weighting... dose means the portion of the equivalent dose that is received from radiation sources outside of the... pattern and level of radiation exposure. (h) Internal dose means the portion of the equivalent dose that...

Study of the optical properties and the carbonaceous clusters in DAM-ADC solid state nuclear track detectors

NASA Astrophysics Data System (ADS)

Rammah, Y. S.; Abdalla, A. M.

2017-12-01

The optical properties of DAM-ADC solid state nuclear track detectors (SSNTDs) were investigated. Samples of DAM-ADC detector were irradiated at room temperature with gamma doses in the range of 100-500 kGy using 1.25 MeV 60Co source of dose rate 4 kGy/h. The optical characterization of these detectors have been studied through the measurements of UV-visible absorption spectra of blank and γ- irradiated samples. The optical energy band gaps, Eg for the detectors were obtained from the direct and the indirect allowed transitions in K-space using two methods (Tauc's model and absorption spectrum fitting (ASF) method). The absorbance of DAM-ADC detector was found to increase with increasing of the gamma absorbed dose. The width of the tail of localized states in the band gap, Eu was evaluated with the Urbach's method. The number of carbon atoms per conjugated length (N), the number of carbon atoms per cluster (M), and refractive index (n) for the present samples were determined. Both of the direct and the indirect band gaps of DAM-ADC detector decrease with increasing of the gamma absorbed dose. Urbach's energy decreased significantly for the detector. An increase in N, M, and n with increasing of the gamma absorbed dose was noticed. Results shed light on the effect of gamma irradiations of DAM-ADC SSNTDs to suitable industrial applications and to modify the optical properties through gamma-induced modifications of the polymer structure.

Absorbed Dose Rate Due to Intake of Natural Radionuclides by Tilapia Fish (Tilapia nilotica,Linnaeus, 1758) Estimated Near Uranium Mining at Caetité, Bahia, Brazil

NASA Astrophysics Data System (ADS)

Pereira, Wagner de S.; Kelecom, Alphonse; Py Júnior, Delcy de Azevedo

2008-08-01

The uranium mining at Caetité (Uranium Concentrate Unit—URA) is in its operational phase. Aiming to estimate the radiological environmental impact of the URA, a monitoring program is underway. In order to preserve the biota of the deleterious effects from radiation and to act in a pro-active way as expected from a licensing body, the present work aims to use an environmental protection methodology based on the calculation of absorbed dose rate in biota. Thus, selected target organism was the Tilapia fish (Tilapia nilotica, Linnaeus, 1758) and the radionuclides were: uranium (U-238), thorium (Th-232), radium (Ra-226 and Ra-228) and lead (Pb-210). As, in Brazil there are no radiation exposure limits adopted for biota the value proposed by the Department of Energy (DOE) of the United States of 3.5×103 μGy y-1 has been used. The derived absorbed dose rate calculated for Tilapia was 2.51×100 μGy y-1, that is less than 0.1% of the dose limit established by DOE. The critical radionuclide was Ra-226, with 56% of the absorbed dose rate, followed by U-238 with 34% and Th-232 with 9%. This value of 0.1% of the limit allows to state that, in the operational conditions analyzed, natural radionuclides do not represent a radiological problem to biota.

Absorbed Dose Rate Due to Intake of Natural Radionuclides by Tilapia Fish (Tilapia nilotica,Linnaeus, 1758) Estimated Near Uranium Mining at Caetite, Bahia, Brazil

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

Pereira, Wagner de S; Universidade Federal Fluminense, Programa de Pos-graduacao em Biologia Marinha; Kelecom, Alphonse

2008-08-07

The uranium mining at Caetite (Uranium Concentrate Unit--URA) is in its operational phase. Aiming to estimate the radiological environmental impact of the URA, a monitoring program is underway. In order to preserve the biota of the deleterious effects from radiation and to act in a pro-active way as expected from a licensing body, the present work aims to use an environmental protection methodology based on the calculation of absorbed dose rate in biota. Thus, selected target organism was the Tilapia fish (Tilapia nilotica, Linnaeus, 1758) and the radionuclides were: uranium (U-238), thorium (Th-232), radium (Ra-226 and Ra-228) and lead (Pb-210).more » As, in Brazil there are no radiation exposure limits adopted for biota the value proposed by the Department of Energy (DOE) of the United States of 3.5x10{sup 3} {mu}Gy y{sup -1} has been used. The derived absorbed dose rate calculated for Tilapia was 2.51x10{sup 0} {mu}Gy y{sup -1}, that is less than 0.1% of the dose limit established by DOE. The critical radionuclide was Ra-226, with 56% of the absorbed dose rate, followed by U-238 with 34% and Th-232 with 9%. This value of 0.1% of the limit allows to state that, in the operational conditions analyzed, natural radionuclides do not represent a radiological problem to biota.« less

Heavy-ion-induced sucrose radicals investigated using EPR and UV spectroscopy.

PubMed

Nakagawa, Kouichi; Karakirova, Yordanka; Yordanov, Nicola D

2015-05-01

The potential use of a sucrose dosimeter for estimating both linear energy transfer (LET) and the absorbed dose of heavy ion and X-ray radiation was investigated. The stable free radicals were produced when sucrose was irradiated with heavy ions, such as helium, carbon, silicon and neon ions, and when the X-ray radiation was similar to the obtained electron paramagnetic resonance (EPR) spectra, which were ∼7 mT wide and composed of several hyperfine structures. In addition, the total spin concentration resulting from heavy-ion irradiation increased linearly as the absorbed dose increased, and decreased logarithmically as the LET increased. These empirical relations imply that the LET at a certain dose can be determined from the spin concentration. For sucrose and alanine, both cross-sections following C-ion irradiation with a 50 Gy dose were ∼1.3 × 10(-12) [μm(2)], taking into account the molecular size of the samples. The values of these cross-sections imply that multiple ionizing particles were involved in the production of stable radicals. Furthermore, UV absorbance at 267 nm of an aqueous solution of irradiated sucrose was found to linearly increase with increasing absorbed dose. Therefore, the EPR and UV results suggest that sucrose can be a useful dosimeter for heavy-ion irradiation. © The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Monte Carlo Analysis of Pion Contribution to Absorbed Dose from Galactic Cosmic Rays

NASA Technical Reports Server (NTRS)

Aghara, S.K.; Battnig, S.R.; Norbury, J.W.; Singleterry, R.C.

2009-01-01

Accurate knowledge of the physics of interaction, particle production and transport is necessary to estimate the radiation damage to equipment used on spacecraft and the biological effects of space radiation. For long duration astronaut missions, both on the International Space Station and the planned manned missions to Moon and Mars, the shielding strategy must include a comprehensive knowledge of the secondary radiation environment. The distribution of absorbed dose and dose equivalent is a function of the type, energy and population of these secondary products. Galactic cosmic rays (GCR) comprised of protons and heavier nuclei have energies from a few MeV per nucleon to the ZeV region, with the spectra reaching flux maxima in the hundreds of MeV range. Therefore, the MeV - GeV region is most important for space radiation. Coincidentally, the pion production energy threshold is about 280 MeV. The question naturally arises as to how important these particles are with respect to space radiation problems. The space radiation transport code, HZETRN (High charge (Z) and Energy TRaNsport), currently used by NASA, performs neutron, proton and heavy ion transport explicitly, but it does not take into account the production and transport of mesons, photons and leptons. In this paper, we present results from the Monte Carlo code MCNPX (Monte Carlo N-Particle eXtended), showing the effect of leptons and mesons when they are produced and transported in a GCR environment.

SU-F-T-474: Evaluation of Dose Perturbation, Temperature and Sensitivity Variation With Accumulated Dose of MOSFET Detector

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

Ganesan, B; Prakasarao, A; Singaravelu, G

Purpose: The use of mega voltage gamma and x-ray sources with their skin sparring qualities in radiation therapy has been a boon in relieving patient discomfort and allowing high tumor doses to be given with fewer restrictions due to radiation effects in the skin. However, high doses given to deep tumors may require careful consideration of dose distribution in the buildup region in order to avoid irreparable damage to the skin. Methods: To measure the perturbation of MOSFET detector in Co60,6MV and 15MV the detector was placed on the surface of the phantom covered with the brass build up cap.more » To measure the effect of temperature the MOSFET detector was kept on the surface of hot water polythene container and the radiation was delivere. In order to measure the sensitivity variation with accumulated dose Measurements were taken by delivering the dose of 200 cGy to MOSFET until the MOSFET absorbed dose comes to 20,000 cGy Results: the Measurement was performed by positioning the bare MOSFET and MOSFET with brass build up cap on the top surface of the solid water phantom for various field sizes in order to find whether there is any attenuation caused in the dose distribution. The response of MOSFET was monitored for temperature ranging from 42 degree C to 22 degree C. The integrated dose dependence of MOSFET dosimeter sensitivity over different energy is not well characterized. This work investigates the dual-bias MOSFET dosimeter sensitivity response to 6 MV and 15 MV beams. Conclusion: From this study it is observed that unlike diode, bare MOSFET does not perturb the radiation field.. It is observed that the build-up influences the temperature dependency of MOSFET and causes some uncertainty in the readings. In the case of sensitivity variation with accumulated dose MOSFET showed higher sensitivity with dose accumulation for both the energies.« less

Microdosimetric Modeling of Biological Effectiveness for Boron Neutron Capture Therapy Considering Intra- and Intercellular Heterogeneity in 10B Distribution.

PubMed

Sato, Tatsuhiko; Masunaga, Shin-Ichiro; Kumada, Hiroaki; Hamada, Nobuyuki

2018-01-17

We here propose a new model for estimating the biological effectiveness for boron neutron capture therapy (BNCT) considering intra- and intercellular heterogeneity in 10 B distribution. The new model was developed from our previously established stochastic microdosimetric kinetic model that determines the surviving fraction of cells irradiated with any radiations. In the model, the probability density of the absorbed doses in microscopic scales is the fundamental physical index for characterizing the radiation fields. A new computational method was established to determine the probability density for application to BNCT using the Particle and Heavy Ion Transport code System PHITS. The parameters used in the model were determined from the measured surviving fraction of tumor cells administrated with two kinds of 10 B compounds. The model quantitatively highlighted the indispensable need to consider the synergetic effect and the dose dependence of the biological effectiveness in the estimate of the therapeutic effect of BNCT. The model can predict the biological effectiveness of newly developed 10 B compounds based on their intra- and intercellular distributions, and thus, it can play important roles not only in treatment planning but also in drug discovery research for future BNCT.

A lead isotope distribution study in swine tissue using ICP-MS

USGS Publications Warehouse

May, T.W.; Wiedmeyer, Ray H.; Brown, L.D.; Casteel, S.W.

1999-01-01

In the United States lead is an ubiquitous environmental pollutant that is a serious human health hazard, especially for women of childbearing age, developing fetuses, and young children. Information concerning the uptake and distribution of lead to maternal and fetal tissues during pregnancy is poorly documented. A study was designed using domestic swine and lead isotope enrichment methodology to focus on maternal absorption and distribution of lead into bone and soft tissues, including the fetal compartment, under varying conditions of oral lead exposure and during altered physiological states (pregnant vs unbred). Total lead levels and Pb207/Pb206 ratios in bone (femur and vertebra), blood, and soft tissues (liver, kidney, brain) were determined by ICP-MS. Lead in fetal tissues derived from maternal bone could be differentiated from that derived from exogenous dosing. Unbred swine absorbed much less lead than pregnant females receiving the same dose. The accuracy and precision of ICP-MS at the instrumental level and for the entire method (sample collection, digestion, and analysis) were evaluated for both Pb207/Pb206 ratios and total lead. Several changes were suggested in method design to improve both instrumental and total method precision.

Calculation of out-of-field dose distribution in carbon-ion radiotherapy by Monte Carlo simulation.

PubMed

Yonai, Shunsuke; Matsufuji, Naruhiro; Namba, Masao

2012-08-01

Recent radiotherapy technologies including carbon-ion radiotherapy can improve the dose concentration in the target volume, thereby not only reducing side effects in organs at risk but also the secondary cancer risk within or near the irradiation field. However, secondary cancer risk in the low-dose region is considered to be non-negligible, especially for younger patients. To achieve a dose estimation of the whole body of each patient receiving carbon-ion radiotherapy, which is essential for risk assessment and epidemiological studies, Monte Carlo simulation plays an important role because the treatment planning system can provide dose distribution only in∕near the irradiation field and the measured data are limited. However, validation of Monte Carlo simulations is necessary. The primary purpose of this study was to establish a calculation method using the Monte Carlo code to estimate the dose and quality factor in the body and to validate the proposed method by comparison with experimental data. Furthermore, we show the distributions of dose equivalent in a phantom and identify the partial contribution of each radiation type. We proposed a calculation method based on a Monte Carlo simulation using the PHITS code to estimate absorbed dose, dose equivalent, and dose-averaged quality factor by using the Q(L)-L relationship based on the ICRP 60 recommendation. The values obtained by this method in modeling the passive beam line at the Heavy-Ion Medical Accelerator in Chiba were compared with our previously measured data. It was shown that our calculation model can estimate the measured value within a factor of 2, which included not only the uncertainty of this calculation method but also those regarding the assumptions of the geometrical modeling and the PHITS code. Also, we showed the differences in the doses and the partial contributions of each radiation type between passive and active carbon-ion beams using this calculation method. These results indicated that it is essentially important to include the dose by secondary neutrons in the assessment of the secondary cancer risk of patients receiving carbon-ion radiotherapy with active as well as passive beams. We established a calculation method with a Monte Carlo simulation to estimate the distribution of dose equivalent in the body as a first step toward routine risk assessment and an epidemiological study of carbon-ion radiotherapy at NIRS. This method has the advantage of being verifiable by the measurement.

Diagnostic x-ray dosimetry using Monte Carlo simulation.

PubMed

Ioppolo, J L; Price, R I; Tuchyna, T; Buckley, C E

2002-05-21

An Electron Gamma Shower version 4 (EGS4) based user code was developed to simulate the absorbed dose in humans during routine diagnostic radiological procedures. Measurements of absorbed dose using thermoluminescent dosimeters (TLDs) were compared directly with EGS4 simulations of absorbed dose in homogeneous, heterogeneous and anthropomorphic phantoms. Realistic voxel-based models characterizing the geometry of the phantoms were used as input to the EGS4 code. The voxel geometry of the anthropomorphic Rando phantom was derived from a CT scan of Rando. The 100 kVp diagnostic energy x-ray spectra of the apparatus used to irradiate the phantoms were measured, and provided as input to the EGS4 code. The TLDs were placed at evenly spaced points symmetrically about the central beam axis, which was perpendicular to the cathode-anode x-ray axis at a number of depths. The TLD measurements in the homogeneous and heterogenous phantoms were on average within 7% of the values calculated by EGS4. Estimates of effective dose with errors less than 10% required fewer numbers of photon histories (1 x 10(7)) than required for the calculation of dose profiles (1 x 10(9)). The EGS4 code was able to satisfactorily predict and thereby provide an instrument for reducing patient and staff effective dose imparted during radiological investigations.

Diagnostic x-ray dosimetry using Monte Carlo simulation

NASA Astrophysics Data System (ADS)

Ioppolo, J. L.; Price, R. I.; Tuchyna, T.; Buckley, C. E.

2002-05-01

An Electron Gamma Shower version 4 (EGS4) based user code was developed to simulate the absorbed dose in humans during routine diagnostic radiological procedures. Measurements of absorbed dose using thermoluminescent dosimeters (TLDs) were compared directly with EGS4 simulations of absorbed dose in homogeneous, heterogeneous and anthropomorphic phantoms. Realistic voxel-based models characterizing the geometry of the phantoms were used as input to the EGS4 code. The voxel geometry of the anthropomorphic Rando phantom was derived from a CT scan of Rando. The 100 kVp diagnostic energy x-ray spectra of the apparatus used to irradiate the phantoms were measured, and provided as input to the EGS4 code. The TLDs were placed at evenly spaced points symmetrically about the central beam axis, which was perpendicular to the cathode-anode x-ray axis at a number of depths. The TLD measurements in the homogeneous and heterogenous phantoms were on average within 7% of the values calculated by EGS4. Estimates of effective dose with errors less than 10% required fewer numbers of photon histories (1 × 107) than required for the calculation of dose profiles (1 × 109). The EGS4 code was able to satisfactorily predict and thereby provide an instrument for reducing patient and staff effective dose imparted during radiological investigations.

Determination of absorbed dose to water from a miniature kilovoltage x-ray source using a parallel-plate ionization chamber

NASA Astrophysics Data System (ADS)

Watson, Peter G. F.; Popovic, Marija; Seuntjens, Jan

2018-01-01

Electronic brachytherapy sources are widely accepted as alternatives to radionuclide-based systems. Yet, formal dosimetry standards for these devices to independently complement the dose protocol provided by the manufacturer are lacking. This article presents a formalism for calculating and independently verifying the absorbed dose to water from a kV x-ray source (The INTRABEAM System) measured in a water phantom with an ionization chamber calibrated in terms of air-kerma. This formalism uses a Monte Carlo (MC) calculated chamber conversion factor, CQ , to convert air-kerma in a reference beam to absorbed dose to water in the measurement beam. In this work CQ was determined for a PTW 34013 parallel-plate ionization chamber. Our results show that CQ was sensitive to the chamber plate separation tolerance, with differences of up to 15%. CQ was also found to have a depth dependence which varied with chamber plate separation (0 to 10% variation for the smallest and largest cavity height, over 3 to 30 mm depth). However for all chamber dimensions investigated, CQ was found to be significantly larger than the manufacturer reported value, suggesting that the manufacturer recommended method of dose calculation could be underestimating the dose to water.

Whole-body biodistribution and estimation of radiation-absorbed doses of the dopamine D1 receptor radioligand 11C-NNC 112 in humans.

PubMed

Cropley, Vanessa L; Fujita, Masahiro; Musachio, John L; Hong, Jinsoo; Ghose, Subroto; Sangare, Janet; Nathan, Pradeep J; Pike, Victor W; Innis, Robert B

2006-01-01

The present study estimated radiation-absorbed doses of the dopamine D(1) receptor radioligand [(11)C]((+)-8-chloro-5-(7-benzofuranyl)-7-hydroxy-3-methyl-2,3,4,5-tetrahydro-1H-3-benzazepine) (NNC 112) in humans, based on dynamic whole-body PET in healthy subjects. Whole-body PET was performed on 7 subjects after injection of 710 +/- 85 MBq of (11)C-NNC 112. Fourteen frames were acquired for a total of 120 min in 7 segments of the body. Regions of interest were drawn on compressed planar images of source organs that could be identified. Radiation dose estimates were calculated from organ residence times using the OLINDA 1.0 program. The organs with the highest radiation-absorbed doses were the gallbladder, liver, lungs, kidneys, and urinary bladder wall. Biexponential fitting of mean bladder activity demonstrated that 15% of activity was excreted via the urine. With a 2.4-h voiding interval, the effective dose was 5.7 microSv/MBq (21.1 mrem/mCi). (11)C-NNC 112 displays a favorable radiation dose profile in humans and would allow multiple PET examinations per year to be performed on the same subject.

A potential role for endogenous proteins as sacrificial sunscreens and antioxidants in human tissues.

PubMed

Hibbert, Sarah A; Watson, Rachel E B; Gibbs, Neil K; Costello, Patrick; Baldock, Clair; Weiss, Anthony S; Griffiths, Christopher E M; Sherratt, Michael J

2015-08-01

Excessive ultraviolet radiation (UVR) exposure of the skin is associated with adverse clinical outcomes. Although both exogenous sunscreens and endogenous tissue components (including melanins and tryptophan-derived compounds) reduce UVR penetration, the role of endogenous proteins in absorbing environmental UV wavelengths is poorly defined. Having previously demonstrated that proteins which are rich in UVR-absorbing amino acid residues are readily degraded by broadband UVB-radiation (containing UVA, UVB and UVC wavelengths) here we hypothesised that UV chromophore (Cys, Trp and Tyr) content can predict the susceptibility of structural proteins in skin and the eye to damage by physiologically relevant doses (up to 15.4 J/cm(2)) of solar UVR (95% UVA, 5% UVB). We show that: i) purified suspensions of UV-chromophore-rich fibronectin dimers, fibrillin microfibrils and β- and γ-lens crystallins undergo solar simulated radiation (SSR)-induced aggregation and/or decomposition and ii) exposure to identical doses of SSR has minimal effect on the size or ultrastructure of UV chromophore-poor tropoelastin, collagen I, collagen VI microfibrils and α-crystallin. If UV chromophore content is a factor in determining protein stability in vivo, we would expect that the tissue distribution of Cys, Trp and Tyr-rich proteins would correlate with regional UVR exposure. From bioinformatic analysis of 244 key structural proteins we identified several biochemically distinct, yet UV chromophore-rich, protein families. The majority of these putative UV-absorbing proteins (including the late cornified envelope proteins, keratin associated proteins, elastic fibre-associated components and β- and γ-crystallins) are localised and/or particularly abundant in tissues that are exposed to the highest doses of environmental UVR, specifically the stratum corneum, hair, papillary dermis and lens. We therefore propose that UV chromophore-rich proteins are localised in regions of high UVR exposure as a consequence of an evolutionary pressure to express sacrificial protein sunscreens which reduce UVR penetration and hence mitigate tissue damage. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Absorbed radiation dosimetry of the D3-specific PET radioligand [18F]FluorTriopride estimated using rodent and nonhuman primate

PubMed Central

Laforest, Richard; Karimi, Morvarid; Moerlein, Stephen M; Xu, Jinbin; Flores, Hubert P; Bognar, Christopher; Li, Aixiao; Mach, Robert H; Perlmutter, Joel S; Tu, Zhude

2016-01-01

[18F]FluorTriopride ([18F]FTP) is a dopamine D3-receptor preferring radioligand with potential for investigation of neuropsychiatric disorders including Parkinson disease, dystonia and schizophrenia. Here we estimate human radiation dosimetry for [18F]FTP based on the ex-vivo biodistribution in rodents and in vivo distribution in nonhuman primates. Biodistribution data were generated using male and female Sprague-Dawley rats injected with ~370 KBq of [18F]FTP and euthanized at 5, 30, 60, 120, and 240 min. Organs of interest were dissected, weighed and assayed for radioactivity content. PET imaging studies were performed in two male and one female macaque fascicularis administered 143-190 MBq of [18F]FTP and scanned whole-body in sequential sections. Organ residence times were calculated based on organ time activity curves (TAC) created from regions of Interest. OLINDA/EXM 1.1 was used to estimate human radiation dosimetry based on scaled organ residence times. In the rodent, the highest absorbed radiation dose was the upper large intestines (0.32-0.49 mGy/MBq), with an effective dose of 0.07 mSv/MBq in males and 0.1 mSv/MBq in females. For the nonhuman primate, however, the gallbladder wall was the critical organ (1.81 mGy/MBq), and the effective dose was 0.02 mSv/MBq. The species discrepancy in dosimetry estimates for [18F]FTP based on rat and primate data can be attributed to the slower transit of tracer through the hepatobiliary track of the primate compared to the rat, which lacks a gallbladder. Out findings demonstrate that the nonhuman primate model is more appropriate model for estimating human absorbed radiation dosimetry when hepatobiliary excretion plays a major role in radiotracer elimination. PMID:28078183

A potential role for endogenous proteins as sacrificial sunscreens and antioxidants in human tissues

PubMed Central

Hibbert, Sarah A.; Watson, Rachel E.B.; Gibbs, Neil K.; Costello, Patrick; Baldock, Clair; Weiss, Anthony S.; Griffiths, Christopher E.M.; Sherratt, Michael J.

2015-01-01

Excessive ultraviolet radiation (UVR) exposure of the skin is associated with adverse clinical outcomes. Although both exogenous sunscreens and endogenous tissue components (including melanins and tryptophan-derived compounds) reduce UVR penetration, the role of endogenous proteins in absorbing environmental UV wavelengths is poorly defined. Having previously demonstrated that proteins which are rich in UVR-absorbing amino acid residues are readily degraded by broadband UVB-radiation (containing UVA, UVB and UVC wavelengths) here we hypothesised that UV chromophore (Cys, Trp and Tyr) content can predict the susceptibility of structural proteins in skin and the eye to damage by physiologically relevant doses (up to 15.4 J/cm2) of solar UVR (95% UVA, 5% UVB). We show that: i) purified suspensions of UV-chromophore-rich fibronectin dimers, fibrillin microfibrils and β- and γ-lens crystallins undergo solar simulated radiation (SSR)-induced aggregation and/or decomposition and ii) exposure to identical doses of SSR has minimal effect on the size or ultrastructure of UV chromophore-poor tropoelastin, collagen I, collagen VI microfibrils and α-crystallin. If UV chromophore content is a factor in determining protein stability in vivo, we would expect that the tissue distribution of Cys, Trp and Tyr-rich proteins would correlate with regional UVR exposure. From bioinformatic analysis of 244 key structural proteins we identified several biochemically distinct, yet UV chromophore-rich, protein families. The majority of these putative UV-absorbing proteins (including the late cornified envelope proteins, keratin associated proteins, elastic fibre-associated components and β- and γ-crystallins) are localised and/or particularly abundant in tissues that are exposed to the highest doses of environmental UVR, specifically the stratum corneum, hair, papillary dermis and lens. We therefore propose that UV chromophore-rich proteins are localised in regions of high UVR exposure as a consequence of an evolutionary pressure to express sacrificial protein sunscreens which reduce UVR penetration and hence mitigate tissue damage. PMID:25911998

SU-F-J-08: Quantitative SPECT Imaging of Ra-223 in a Phantom

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

Yue, J; Hobbs, R; Sgouros, G

Purpose: Ra-223 therapy of prostate cancer bone metastases is being used to treat patients routinely. However, the absorbed dose distribution at the macroscopic and microscopic scales remains elusive, due to the inability to image the small activities injected. Accurate activity quantification through imaging is essential to calculate the absorbed dose in organs and sub-units in radiopharmaceutical therapy, enabling personalized absorbed dose-based treatment planning methodologies and more effective and optimal treatments. Methods: A 22 cm diameter by 20 cm long cylindrical phantom, containing a 3.52 cm diameter sphere, was used. A total of 2.01 MBq of Ra-223 was placed in themore » phantom with 177.6 kBq in the sphere. Images were acquired on a dual-head Siemens Symbia T16 gamma camera using three 20% full-width energy windows and centered at 84, 154, and 269 keV (120 projections, 360° rotation, 45 s per view). We have implemented reconstruction of Ra-223 SPECT projections using OS-EM (up to 20 iterations of 10 subsets) with compensation for attenuation using CT-based attenuation maps, collimator-detector response (CDR) (including septal penetration, scatter and Pb x-ray modeling), and scatter in the patient using the effective source scatter estimation (ESSE) method. The CDR functions and scatter kernels required for ESSE were computed using the SIMIND MC simulation code. All Ra-223 photon emissions as well as gamma rays from the daughters Rn-219 and Bi-211 were modeled. Results: The sensitivity of the camera in the three combined windows was 107.3 cps/MBq. The visual quality of the SPECT images was reasonably good and the activity in the sphere was 27% smaller than the true activity. This underestimation is likely due to partial volume effect. Conclusion: Absolute quantitative Ra-223 SPECT imaging is achievable with careful attention to compensate for image degrading factors and system calibration.« less

Establishment of a γ-H2AX foci-based assay to determine biological dose of radon to red bone marrow in rats

PubMed Central

Wang, Jing; He, Linfeng; Fan, Dunhuang; Ding, Defang; Wang, Xufei; Gao, Yun; Zhang, Xuxia; Li, Qiang; Chen, Honghong

2016-01-01

The biodosimetric information is critical for assessment of cancer risk in populations exposed to high radon. However, no tools are available for biological dose estimation following radon exposure. Here, we established a γ-H2AX foci-based assay to determine biological dose to red bone marrow (RBM) in radon-inhaled rats. After 1–3 h of in vitro radon exposure, a specific pattern of γ-H2AX foci, linear tracks with individual p-ATM and p-DNA-PKcs foci, was observed, and the yield of γ-H2AX foci and its linear tracks displayed a linear dose-response manner in both rat peripheral blood lymphocytes (PBLs) and bone-marrow lymphocytes (BMLs). When the cumulative doses of radon inhaled by rats reached 14, 30 and 60 working level months (WLM), the yields of three types of foci markedly increased in both PBLs and BMLs, and γ-H2AX foci-based dose estimates to RBM were 0.97, 2.06 and 3.94 mGy, respectively. Notably, BMLs displayed a more profound increase of three types of foci than PBLs, and the absorbed dose ratio between BMLs and PBLs was similar between rats exposed to 30 and 60 WLM of radon. Taken together, γ-H2AX foci quantitation in PBLs is able to estimate RBM-absorbed doses with the dose-response curve of γ-H2AX foci after in vitro radon exposure and the ratio of RBM- to PBL-absorbed doses in rats following radon exposure. PMID:27445126

Establishment of a γ-H2AX foci-based assay to determine biological dose of radon to red bone marrow in rats

NASA Astrophysics Data System (ADS)

Wang, Jing; He, Linfeng; Fan, Dunhuang; Ding, Defang; Wang, Xufei; Gao, Yun; Zhang, Xuxia; Li, Qiang; Chen, Honghong

2016-07-01

The biodosimetric information is critical for assessment of cancer risk in populations exposed to high radon. However, no tools are available for biological dose estimation following radon exposure. Here, we established a γ-H2AX foci-based assay to determine biological dose to red bone marrow (RBM) in radon-inhaled rats. After 1-3 h of in vitro radon exposure, a specific pattern of γ-H2AX foci, linear tracks with individual p-ATM and p-DNA-PKcs foci, was observed, and the yield of γ-H2AX foci and its linear tracks displayed a linear dose-response manner in both rat peripheral blood lymphocytes (PBLs) and bone-marrow lymphocytes (BMLs). When the cumulative doses of radon inhaled by rats reached 14, 30 and 60 working level months (WLM), the yields of three types of foci markedly increased in both PBLs and BMLs, and γ-H2AX foci-based dose estimates to RBM were 0.97, 2.06 and 3.94 mGy, respectively. Notably, BMLs displayed a more profound increase of three types of foci than PBLs, and the absorbed dose ratio between BMLs and PBLs was similar between rats exposed to 30 and 60 WLM of radon. Taken together, γ-H2AX foci quantitation in PBLs is able to estimate RBM-absorbed doses with the dose-response curve of γ-H2AX foci after in vitro radon exposure and the ratio of RBM- to PBL-absorbed doses in rats following radon exposure.

Cerium nanoparticle effect on sensitivity of Fricke gel dosimeter: Initial investigation

NASA Astrophysics Data System (ADS)

Ebenezer Suman Babu, S.; Peace Balasingh, S. Timothy; Benedicta Pearlin, R.; Rabi Raja Singh, I.; Ravindran, B. Paul

2017-05-01

Fricke gel dosimeters (FXGs) have been the preferred dosimeters because of its ease in preparation and water and tissue equivalency. Visible changes happen three dimensionally in the dosimeter as the ferrous (Fe2+) ions change into ferric (Fe3+) ions upon irradiation and the measure of this change can be correlated to the dose absorbed. Nanoparticles are promising entities that can improve the sensitivity of the gel dosimeter. Cerium Oxide nanoparticle was investigated for possible enhancement of absorbed dose in the FXG. Various concentrations of the nanoparticle based gel dosimeters were prepared and irradiated for a clinical dose range of 0-3 Gy in a telegamma unit. The optimal concentration of 0.1 mM nanoparticle incorporated in the FXG enhances the radiation sensitivity of the unmodified FXG taken as reference without modifying the background absorbance prior to irradiation. The gel recipe consisted of 5% (wt) gelatin, 50 mM Sulphuric acid, 0.05 mM Xylenol Orange, 0.5 mM Ferrous Ammonium Sulphate and 0.1 mM Cerium (IV) Oxide nanoparticle (< 25 nm particle size) and triple distilled water. The FXGs with nanoparticle showed linear dose response in the dose range tested.

Development of a portable graphite calorimeter for radiation dosimetry.

PubMed

Sakama, Makoto; Kanai, Tatsuaki; Fukumura, Akifumi

2008-01-01

We developed and performance-tested a portable graphite calorimeter designed to measure the absolute dosimetry of various beams including heavy-ion beams, based on a flexible and convenient means of measurement. This measurement system is fully remote-controlled by the GPIB system. This system uses a digital PID (Proportional, Integral, Derivative) control method based on the LabVIEW software. It was possible to attain stable conditions in a shorter time by this system. The standard deviation of the measurements using the calorimeter was 0.79% at a dose rate of 0.8 Gy/min in 17 calorimeter runs for a (60)Co photon beam. The overall uncertainties for the absorbed dose to graphite and water of the (60)Co photon beam using the developed calorimeter were 0.89% and 1.35%, respectively. Estimations of the correction factors due to vacuum gaps, impurities in the core, the dose gradient and the radiation profile were included in the uncertainties. The absorbed doses to graphite and water irradiated by the (60)Co photon beam were compared with dosimetry measurements obtained using three ionization chambers. The absorbed doses to graphite and water estimated by the two dosimetry methods agreed within 0.1% and 0.3%, respectively.

Modeling gamma radiation dose in dwellings due to building materials.

PubMed

de Jong, Peter; van Dijk, Willem

2008-01-01

A model is presented that calculates the absorbed dose rate in air of gamma radiation emitted by building materials in a rectangular body construction. The basis for these calculations is formed by a fixed set of specific absorbed dose rates (the dose rate per Bq kg(-1) 238U, 232Th, and 40K), as determined for a standard geometry with the dimensions 4 x 5 x 2.8 m3. Using the computer codes Marmer and MicroShield, correction factors are assessed that quantify the influence of several room and material related parameters on the specific absorbed dose rates. The investigated parameters are the position in the construction; the thickness, density, and dimensions of the construction parts; the contribution from the outer leave; the presence of doors and windows; the attenuation by internal partition walls; the contribution from building materials present in adjacent rooms; and the effect of non-equilibrium due to 222Rn exhalation. To verify the precision, the proposed method is applied to three Dutch reference dwellings, i.e., a row house, a coupled house, and a gallery apartment. The averaged difference with MCNP calculations is found to be 4%.

[Analysis of the importance of cosmonaut's location and orientation onboard the International space station to levels of visceral irradiation during traverse of the region of the South Atlantic Anomaly].

PubMed

Drobyshev, S G; Benghin, V V

2015-01-01

Parametric analysis of absorbed radiation dose to the cosmonaut working in the Service module (SM) of the International space station (ISS) was made with allowance for anisotropy of the radiation field of the South Atlantic Anomaly. Calculation data show that in weakly shielded SM compartments the radiation dose to poorly shielded viscera may depend essentially on cosmonaut's location and orientation relative to the ISS shell. Difference of the lens absorbed dose can be as high as 5 times depending on orientation of the cosmonaut and the ISS. The effect is less pronounced on the deep seated hematopoietic system; however, it may increase up to 2.5 times during the extravehicular activities. When the cosmonaut is outside on the ISS SM side presented eastward, the absorbed dose can be affected noticeably by remoteness from the SM. At a distance less than 1.5 meters away from the SM east side in the course of ascending circuits, the calculated lens dose is approximately half as compared with the situation when the cosmonaut is not shielded by the ISS material.

SU-E-CAMPUS-I-05: Internal Dosimetric Calculations for Several Imaging Radiopharmaceuticals in Preclinical Studies and Quantitative Assessment of the Mouse Size Impact On Them. Realistic Monte Carlo Simulations Based On the 4D-MOBY Model

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

Kostou, T; Papadimitroulas, P; Kagadis, GC

2014-06-15

Purpose: Commonly used radiopharmaceuticals were tested to define the most important dosimetric factors in preclinical studies. Dosimetric calculations were applied in two different whole-body mouse models, with varying organ size, so as to determine their impact on absorbed doses and S-values. Organ mass influence was evaluated with computational models and Monte Carlo(MC) simulations. Methods: MC simulations were executed on GATE to determine dose distribution in the 4D digital MOBY mouse phantom. Two mouse models, 28 and 34 g respectively, were constructed based on realistic preclinical exams to calculate the absorbed doses and S-values of five commonly used radionuclides in SPECT/PETmore » studies (18F, 68Ga, 177Lu, 111In and 99mTc).Radionuclide biodistributions were obtained from literature. Realistic statistics (uncertainty lower than 4.5%) were acquired using the standard physical model in Geant4. Comparisons of the dosimetric calculations on the two different phantoms for each radiopharmaceutical are presented. Results: Dose per organ in mGy was calculated for all radiopharmaceuticals. The two models introduced a difference of 0.69% in their brain masses, while the largest differences were observed in the marrow 18.98% and in the thyroid 18.65% masses.Furthermore, S-values of the most important target-organs were calculated for each isotope. Source-organ was selected to be the whole mouse body.Differences on the S-factors were observed in the 6.0–30.0% range. Tables with all the calculations as reference dosimetric data were developed. Conclusion: Accurate dose per organ and the most appropriate S-values are derived for specific preclinical studies. The impact of the mouse model size is rather high (up to 30% for a 17.65% difference in the total mass), and thus accurate definition of the organ mass is a crucial parameter for self-absorbed S values calculation.Our goal is to extent the study for accurate estimations in small animal imaging, whereas it is known that there is a large variety in the anatomy of the organs.« less

Radiation environment on the Mir orbital station during solar minimum.

PubMed

Badhwar, G D; Atwell, W; Cash, B; Petrov, V M; Akatov YuA; Tchernykh, I V; Shurshakov, V A; Arkhangelsky, V A

1998-01-01

The Mir station has been in a 51.65 degrees inclination orbit since March 1986. In March 1995, the first US astronaut flew on the Mir-18 mission and returned on the Space Shuttle in July 1995. Since then three additional US astronauts have stayed on orbit for up to 6 months. Since the return of the first US astronaut, both the Spektr and Priroda modules have docked with Mir station, altering the mass shielding distribution. Radiation measurements, including the direct comparison of US and Russian absorbed dose rates in the Base Block of the Mir station, were made during the Mir-18 and -19 missions. There is a significant variation of dose rates across the core module; the six locations sampled showed a variation of a factor of nearly two. A tissue equivalent proportional counter (TEPC) measured a total absorbed dose rate of 300 microGy/day, roughly equally divided between the rate due to trapped protons from the South Atlantic Anomaly (SAA) and galactic cosmic radiation (GCR). This dose rate is about a factor of two lower than the rate measured by the thinly shielded (0.5 g cm-2 of Al) operational ion chamber (R-16), and about 3/2 of the rate of the more heavily shielded (3.5 g cm-2 of Al) ion chamber. This is due to the differences in the mass shielding properties at the location of these detectors. A comparison of integral linear energy transfer (LET) spectra measured by TEPC and plastic nuclear track detectors (PNTDs) deployed side by side are in remarkable agreement in the LET region of 15-1000 keV/micrometer, where the PNTDs are fully efficient. The average quality factor, using the ICRP-26 definition, was 2.6, which is higher than normally used. There is excellent agreement between the measured GCR dose rate and model calculations, but this is not true for trapped protons. The measured Mir-18 crew skin dose equivalent rate was 1133 microSv/day. Using the skin dose rate and anatomical models, we have estimated the blood-forming organ (BFO) dose rate and the maximum stay time in orbit for International Space Station crew members.

Absorption and distribution of lycopene in rat colon.

PubMed

Oshima, S; Inakuma, T; Narisawa, T

1999-01-01

Colonic absorption and distribution of lycopene, which inhibited rat colon carcinogenesis in our previous studies, were investigated in Sprague-Dawley rats. Three groups of six rats each with or without a single-barreled colostomy at the mid colon were given a single intragastric or intracolonic dose of 0.2 mL of corn oil containing 12 mg of lycopene. Twenty-four hours later, all rats were sacrificed and the blood and some tissues were collected. The contents of lycopene in the samples were assayed by HPLC. Lycopene was detected in an appreciable amount in the liver, but only in trace amount in the serum of all rats treated with an intracolonic dose of lycopene and in rats with an intragastric dose. After an intragastric lycopene treatment, lycopene was detected in the mucosa of the proximal colon and of the distal colon of the colostomized rats, whose distal colon had been excluded from the fecal stream. A large amount of lycopene was recovered in the feces. None was detected in any sample from the control rats treated with an intragastric or intracolonic dose of plain corn oil. The results suggest that lycopene is absorbed from the colon and also from the small intestine. It might be concluded that both ways of absorption contribute to a comparative amount of lycopene accumulation in the colon mucosa after ingestion of this carotenoid.

Pharmacokinetics of S-3-(4-acetylamino-phenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethyl-phenyl)-propionamide in rats, a non-steroidal selective androgen receptor modulator

PubMed Central

KEARBEY, J. D.; WU, D.; GAO, W.; MILLER, D. D.; DALTON, J. T.

2007-01-01

1. S-3-(4-acetylamino-phenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethyl-phenyl)-propionamide (also known as S-4) is a non-steroidal selective androgen receptor modulator demonstrating tissue-selective androgenic and anabolic effects. The purpose of the present study was to examine the systemic pharmacokinetics, elimination and oral bioavailability of S-4 in rats. 2. Thirty-five male Sprague–Dawley rats weighing approximately 250 g were randomly assigned to one of seven treatment groups. Intravenous doses of 0.5, 1, 10, and 30 mg kg−1 were given via a jugular catheter. Oral doses of 1, 10 and 30 mg kg−1 were administered via gavage. Plasma concentrations were determined using a validated high-performance liquid chromatography or by a high-performance liquid chromatography/mass spectrometry method. 3. Clearances ranged between 1.0 and 2.1 ml min−1 kg−1 and varied with dose. The volume of distribution was approximately 0.448 l kg−1 in all treatment groups. Oral bioavailability was also dose dependent, with the lower doses showing complete oral bioavailability. The half-life of S-4 over the dose range tested was between 2.6 and 5.3 h. 4. It was demonstrated that S-4 is rapidly absorbed, slowly cleared, and has a moderate volume of distribution in rats. The pharmacokinetics and oral bioavailability of S-4 indicate that it is an excellent candidate for clinical development. PMID:15204699

Dose estimation for astronauts using dose conversion coefficients calculated with the PHITS code and the ICRP/ICRU adult reference computational phantoms.

PubMed

Sato, Tatsuhiko; Endo, Akira; Sihver, Lembit; Niita, Koji

2011-03-01

Absorbed-dose and dose-equivalent rates for astronauts were estimated by multiplying fluence-to-dose conversion coefficients in the units of Gy.cm(2) and Sv.cm(2), respectively, and cosmic-ray fluxes around spacecrafts in the unit of cm(-2) s(-1). The dose conversion coefficients employed in the calculation were evaluated using the general-purpose particle and heavy ion transport code system PHITS coupled to the male and female adult reference computational phantoms, which were released as a common ICRP/ICRU publication. The cosmic-ray fluxes inside and near to spacecrafts were also calculated by PHITS, using simplified geometries. The accuracy of the obtained absorbed-dose and dose-equivalent rates was verified by various experimental data measured both inside and outside spacecrafts. The calculations quantitatively show that the effective doses for astronauts are significantly greater than their corresponding effective dose equivalents, because of the numerical incompatibility between the radiation quality factors and the radiation weighting factors. These results demonstrate the usefulness of dose conversion coefficients in space dosimetry. © Springer-Verlag 2010

Absorbed dose to water based dosimetry versus air kerma based dosimetry for high-energy photon beams: an experimental study.

PubMed

Palmans, Hugo; Nafaa, Laila; De, Jans Jo; Gillis, Sofie; Hoornaert, Marie-Thérèse; Martens, Chantal; Piessens, Marleen; Thierens, Hubert; Van der Plaetsen, Ann; Vynckier, Stefaan

2002-02-07

In recent years, a change has been proposed from air kerma based reference dosimetry to absorbed dose based reference dosimetry for all radiotherapy beams of ionizing radiation. In this paper, a dosimetry study is presented in which absorbed dose based dosimetry using recently developed formalisms was compared with air kerma based dosimetry using older formalisms. Three ionization chambers of each of three different types were calibrated in terms of absorbed dose to water and air kerma and sent to five hospitals. There, reference dosimetry with all the chambers was performed in a total of eight high-energy clinical photon beams. The selected chamber types were the NE2571, the PTW-30004 and the Wellhöfer-FC65G (previously Wellhöfer-IC70). Having a graphite wall, they exhibit a stable volume and the presence of an aluminium electrode ensures the robustness of these chambers. The data were analysed with the most important recommendations for clinical dosimetry: IAEA TRS-398, AAPM TG-51, IAEA TRS-277, NCS report-2 (presently recommended in Belgium) and AAPM TG-21. The necessary conversion factors were taken from those protocols, or calculated using the data in the different protocols if data for a chamber type are lacking. Polarity corrections were within 0.1% for all chambers in all beams. Recombination corrections were consistent with theoretical predictions, did not vary within a chamber type and only slightly between different chamber types. The maximum chamber-to-chamber variations of the dose obtained with the different formalisms within the same chamber type were between 0.2% and 0.6% for the NE2571, between 0.2% and 0.6% for the PTW-30004 and 0.1% and 0.3% for the Wellhöfer-FC65G for the different beams. The absorbed dose results for the NE2571 and Wellhöfer-FC65G chambers were in good agreement for all beams and all formalisms. The PTW-30004 chambers gave a small but systematically higher result compared to the result for the NE2571 chambers (on the average 0.1% for IAEA TRS-277, 0.3% for NCS report-2 and AAPM TG-21 and 0.4% for IAEA TRS-398 and AAPM TG-51). Within the air kerma based protocols, the results obtained with the TG-21 protocol were 0.4-0.8% higher mainly due to the differences in the data used. Both absorbed dose to water based formalisms resulted in consistent values within 0.3%. The change from old to new formalisms is discussed together with the traceability of calibration factors obtained at the primary absorbed dose and air kerma standards in the reference beams (60Co). For the particular situation in Belgium (calibrations at the Laboratory for Standard Dosimetry of Ghent) the change amounts to 0.1-0.6%. This is similar to the magnitude of the change determined in other countries.

Helium ions for radiotherapy? Physical and biological verifications of a novel treatment modality

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

Krämer, Michael, E-mail: m.kraemer@gsi.de; Scifoni, Emanuele; Schuy, Christoph

Purpose: Modern facilities for actively scanned ion beam radiotherapy allow in principle the use of helium beams, which could present specific advantages, especially for pediatric tumors. In order to assess the potential use of these beams for radiotherapy, i.e., to create realistic treatment plans, the authors set up a dedicated {sup 4}He beam model, providing base data for their treatment planning system TRiP98, and they have reported that in this work together with its physical and biological validations. Methods: A semiempirical beam model for the physical depth dose deposition and the production of nuclear fragments was developed and introduced inmore » TRiP98. For the biological effect calculations the last version of the local effect model was used. The model predictions were experimentally verified at the HIT facility. The primary beam attenuation and the characteristics of secondary charged particles at various depth in water were investigated using {sup 4}He ion beams of 200 MeV/u. The nuclear charge of secondary fragments was identified using a ΔE/E telescope. 3D absorbed dose distributions were measured with pin point ionization chambers and the biological dosimetry experiments were realized irradiating a Chinese hamster ovary cells stack arranged in an extended target. Results: The few experimental data available on basic physical processes are reproduced by their beam model. The experimental verification of absorbed dose distributions in extended target volumes yields an overall agreement, with a slight underestimation of the lateral spread. Cell survival along a 4 cm extended target is reproduced with remarkable accuracy. Conclusions: The authors presented a simple simulation model for therapeutical {sup 4}He beams which they introduced in TRiP98, and which is validated experimentally by means of physical and biological dosimetries. Thus, it is now possible to perform detailed treatment planning studies with {sup 4}He beams, either exclusively or in combination with other ion modalities.« less

The application of polymer gel dosimeters to dosimetry for targeted radionuclide therapy

NASA Astrophysics Data System (ADS)

Gear, J. I.; Flux, G. D.; Charles-Edwards, E.; Partridge, M.; Cook, G.; Ott, R. J.

2006-07-01

There is a lack of standardized methodology to perform dose calculations for targeted radionuclide therapy and at present no method exists to objectively evaluate the various approaches employed. The aim of the work described here was to investigate the practicality and accuracy of calibrating polymer gel dosimeters such that dose measurements resulting from complex activity distributions can be verified. Twelve vials of the polymer gel dosimeter, 'MAGIC', were uniformly mixed with varying concentrations of P-32 such that absorbed doses ranged from 0 to 30 Gy after a period of 360 h before being imaged on a magnetic resonance scanner. In addition, nine vials were prepared and irradiated using an external 6 MV x-ray beam. Magnetic resonance transverse relaxation time, T2, maps were obtained using a multi-echo spin echo sequence and converted to R2 maps (where T2 = 1/R2). Absorbed doses for P-32 irradiated gel were calculated according to the medical internal radiation dose schema using EGSnrc Monte Carlo simulations. Here the energy deposited in cylinders representing the irradiated vials was scored. A relationship between dose and R2 was determined. Effects from oxygen contamination were present in the internally irradiated vials. An increase in O2 sensitivity over those gels irradiated externally was thought to be a result of the longer irradiation period. However, below the region of contamination dose response appeared homogenous. Due do a drop-off of dose at the periphery of the internally irradiated vials, magnetic resonance ringing artefacts were observed. The ringing did not greatly affect the accuracy of calibration, which was comparable for both methods. The largest errors in calculated dose originated from the initial activity measurements, and were approximately 10%. Measured R2 values ranged from 5-35 s-1 with an average standard deviation of 1%. A clear relationship between R2 and dose was observed, with up to 40% increased sensitivity for internally irradiated gels. Curve fits to the calibration data followed a single exponential function. The correlation coefficients for internally and externally irradiated gels were 0.991 and 0.985, respectively. With the ability to accurately calibrate internally dosed polymer gels, this technology shows promise as a means to evaluate dosimetry methods, particularly in cases of non-uniform uptake of a radionuclide.

Dose heterogeneity correction for low-energy brachytherapy sources using dual-energy CT images

NASA Astrophysics Data System (ADS)

Mashouf, S.; Lechtman, E.; Lai, P.; Keller, B. M.; Karotki, A.; Beachey, D. J.; Pignol, J. P.

2014-09-01

Permanent seed implant brachytherapy is currently used for adjuvant radiotherapy of early stage prostate and breast cancer patients. The current standard for calculation of dose around brachytherapy sources is based on the AAPM TG-43 formalism, which generates the dose in a homogeneous water medium. Recently, AAPM TG-186 emphasized the importance of accounting for tissue heterogeneities. We have previously reported on a methodology where the absorbed dose in tissue can be obtained by multiplying the dose, calculated by the TG-43 formalism, by an inhomogeneity correction factor (ICF). In this work we make use of dual energy CT (DECT) images to extract ICF parameters. The advantage of DECT over conventional CT is that it eliminates the need for tissue segmentation as well as assignment of population based atomic compositions. DECT images of a heterogeneous phantom were acquired and the dose was calculated using both TG-43 and TG-43 × \\text{ICF} formalisms. The results were compared to experimental measurements using Gafchromic films in the mid-plane of the phantom. For a seed implant configuration of 8 seeds spaced 1.5 cm apart in a cubic structure, the gamma passing score for 2%/2 mm criteria improved from 40.8% to 90.5% when ICF was applied to TG-43 dose distributions.

131I-tositumomab myeloablative radioimmunotherapy for non-Hodgkin’s lymphoma: radiation dose to the testes

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

Hattori, Naoya; Gopal, Ajay K.; Shields, Andrew T.

Purpose: To investigate radiation doses to the testes delivered by a radiolabeled anti-CD20 antibody and its effects on male sex hormone levels. Materials and methods: Testicular uptake and retention of 131I-tositumomab were measured, and testicular absorbed doses were calculated for 67 male patients (54+/-11 years of age) with non-Hodgkin's lymphoma who had undergone myeloablative radioimmunotherapy (RIT) using 131I-tositumomab. Time-activity curves for the major organs, testes, and whole body were generated from planar imaging studies. In a subset of patients, male sex hormones were measured before and 1 year after the therapy. Results: The absorbed dose to the testes showed considerablemore » variability (range=4.4-70.2 Gy). Pretherapy levels of total testosterone were below the lower limit of the reference range, and post-therapy evaluation demonstrated further reduction [4.6+/-1.8 nmol/l (pre-RIT) vs. 3.8+/-2.9 nmol/l (post-RIT), P<0.05]. Patients receiving higher radiation doses to the testes (>=25 Gy) showed a greater reduction [4.7+/-1.6 nmol/l (pre-RIT) vs. 3.3+/-2.7 nmol/l (post-RIT), P<0.05] compared with patients receiving lower doses (<25 Gy), who showed no significant change in total testosterone levels. Conclusion: The testicular radiation absorbed dose varied highly among individual patients. Finally, patients receiving higher doses to the testes were more likely to show post-RIT suppression of testosterone levels.« less

SU-G-201-08: Energy Response of Thermoluminescent Microcube Dosimeters in Water for Kilovoltage X-Ray Beams

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

Di Maso, L; Lawless, M; Culberson, W

Purpose: To characterize the energy dependence for TLD-100 microcubes in water at kilovoltage energies. Methods: TLD-100 microcubes with dimensions of (1 × 1 × 1) mm{sup 3} were irradiated with kilovoltage x-rays in a custom-built thin-window liquid water phantom. The TLD-100 microcubes were held in Virtual Water™ probes and aligned at a 2 cm depth in water. Irradiations were performed using the M-series x-ray beams of energies ranging from 50-250 kVp and normalized to a {sup 60}Co beam located at the UWADCL. Simulations using the EGSnrc Monte Carlo Code System were performed to model the x-ray beams, the {sup 60}Comore » beam, the water phantom and the dosimeters in the phantom. The egs-chamber user code was used to tally the dose to the TLDs and the dose to water. The measurements and calculations were used to determine the intrinsic energy dependence, absorbed-dose energy dependence, and absorbed-dose sensitivity. These values were compared to TLD-100 chips with dimensions of (3.2 × 0.9 × 0.9) mm{sup 3}. Results: The measured TLD-100 microcube response per dose to water among all investigated x-ray energies had a maximum percent difference of 61% relative to {sup 60}Co. The simulated ratio of dose to water to the dose to TLD had a maximum percent difference of 29% relative to {sup 60}Co. The ratio of dose to TLD to the TLD output had a maximum percent difference of 13% relative to {sup 60}Co. The maximum percent difference for the absorbed-dose sensitivity was 15% more than the used value of 1.41. Conclusion: These results confirm that differences in beam quality have a significant effect on TLD response when irradiated in water. These results also indicated a difference in TLD-100 response between microcube and chip geometries. The intrinsic energy dependence and the absorbed-dose energy dependence deviated up to 10% between TLD-100 microcubes and chips.« less

Accuracy and optimal timing of activity measurements in estimating the absorbed dose of radioiodine in the treatment of Graves' disease

NASA Astrophysics Data System (ADS)

Merrill, S.; Horowitz, J.; Traino, A. C.; Chipkin, S. R.; Hollot, C. V.; Chait, Y.

2011-02-01

Calculation of the therapeutic activity of radioiodine 131I for individualized dosimetry in the treatment of Graves' disease requires an accurate estimate of the thyroid absorbed radiation dose based on a tracer activity administration of 131I. Common approaches (Marinelli-Quimby formula, MIRD algorithm) use, respectively, the effective half-life of radioiodine in the thyroid and the time-integrated activity. Many physicians perform one, two, or at most three tracer dose activity measurements at various times and calculate the required therapeutic activity by ad hoc methods. In this paper, we study the accuracy of estimates of four 'target variables': time-integrated activity coefficient, time of maximum activity, maximum activity, and effective half-life in the gland. Clinical data from 41 patients who underwent 131I therapy for Graves' disease at the University Hospital in Pisa, Italy, are used for analysis. The radioiodine kinetics are described using a nonlinear mixed-effects model. The distributions of the target variables in the patient population are characterized. Using minimum root mean squared error as the criterion, optimal 1-, 2-, and 3-point sampling schedules are determined for estimation of the target variables, and probabilistic bounds are given for the errors under the optimal times. An algorithm is developed for computing the optimal 1-, 2-, and 3-point sampling schedules for the target variables. This algorithm is implemented in a freely available software tool. Taking into consideration 131I effective half-life in the thyroid and measurement noise, the optimal 1-point time for time-integrated activity coefficient is a measurement 1 week following the tracer dose. Additional measurements give only a slight improvement in accuracy.

An Open-Label Investigation of the Pharmacokinetics and Tolerability of Oral Cysteamine in Adults with Cystic Fibrosis.

PubMed

Devereux, Graham; Steele, Sandra; Griffiths, Kairen; Devlin, Edward; Fraser-Pitt, Douglas; Cotton, Seonaidh; Norrie, John; Chrystyn, Henry; O'Neil, Deborah

2016-08-01

Cysteamine is licensed for use in nephropathic cystinosis but preclinical data suggest a role in managing cystic fibrosis (CF). This study aimed to determine whether oral cysteamine is absorbed in adult CF patients and enters the bronchial secretions. Tolerability outcomes were also explored. Patients ≥18 years of age, weighing >50 kg with stable CF lung disease were commenced on oral cysteamine bitartrate (Cystagon(®)) 450 mg once daily, increased weekly to 450 mg four times daily. Serial plasma cysteamine concentrations were measured for 24 h after the first dose. Participants were reviewed every week for 6 weeks, except at 4 weeks. Plasma cysteamine concentrations were measured 8 h after dosing when reviewed at 1, 2 and 3 weeks and 6 h after dosing when reviewed at 5 weeks. Sputum cysteamine concentration was also quantified at the 5-week assessment. Seven of the ten participants reported adverse reactions typical of cysteamine, two participants discontinued intervention. Following the first 450-mg dose, mean (SD) maximum concentration (C max) was 2.86 (1.96) mg/l, the time corresponding to C max (T max) was 1.2 (0.7) h, the half-life (t ½) was 3.7 (1.7) h, clearance (CL/F) 89.9 (30.5) L/h and volume of distribution (V d/F) 427 (129) L. Cysteamine appeared to accumulate in sputum with a median (interquartile range) sputum:plasma cysteamine concentration ratio of 4.2 (0.98-8.84). Oral cysteamine is absorbed and enters the bronchial secretions in patients with CF. Although adverse reactions were common, the majority of patients continued with cysteamine. Further trials are required to establish the risk benefit ratio of cysteamine therapy in CF.

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

Influence of Exposure and Toxicokinetics on Measures of Aquatic Toxicity for Organic Contaminants: A Case Study Review

PubMed Central

Landrum, Peter F; Chapman, Peter M; Neff, Jerry; Page, David S

2013-01-01

This theoretical and case study review of dynamic exposures of aquatic organisms to organic contaminants examines variables important for interpreting exposure and therefore toxicity. The timing and magnitude of the absorbed dose change when the dynamics of exposure change. Thus, the dose metric for interpreting toxic responses observed during such exposure conditions is generally limited to the specific experiment and cannot be extrapolated to either other experiments with different exposure dynamics or to field exposures where exposure dynamics usually are different. This is particularly true for mixture exposures, for which the concentration and composition and, therefore, the timing and magnitude of exposure to individual components of different potency and potentially different mechanisms of action can vary. Aquatic toxicology needs studies that develop temporal thresholds for absorbed toxicant doses to allow for better extrapolation between conditions of dynamic exposure. Improved experimental designs are required that include high-quality temporal measures of both the exposure and the absorbed dose to allow better interpretation of data. For the short term, initial water concentration can be considered a conservative measure of exposure, although the extent to which this is true cannot be estimated specifically unless the dynamics of exposure as well as the toxicokinetics of the chemicals in the exposure scenario for the organism of interest are known. A better, but still limited, metric for interpreting the exposure and, therefore, toxicity is the peak absorbed dose, although this neglects toxicodynamics, requires appropriate temporal measures of accumulated dose to determine the peak concentration, and requires temporal thresholds for critical body residue for each component of the mixture. Integr Environ Assess Manag 2013; 9: 196–210. © 2012 SETAC PMID:23229376

Assessment of exposure to pesticides during mixing/loading and spraying of tomatoes in the open field.

PubMed

Aprea, Maria Cristina; Bosi, Anna; Manara, Michele; Mazzocchi, Barbara; Pompini, Alessandra; Sormani, Francesca; Lunghini, Liana; Sciarra, Gianfranco

2016-01-01

Some evidence of exposure-response of metolachlor and pendimethalin for lung cancer and an association of metribuzin with risk of glioma have been reported. The primary objectives in this study were to evaluate exposure and occupational risk during mixing/loading of pesticides and during their application to tomatoes cultivated in open fields. Sixteen farmers were sampled. Respiratory exposure was estimated by personal air sampling using fiberglass filters in a IOM device. Dermal exposure was assessed using skin pads and hand washing. Absorbed doses were estimated assuming 100% lung retention, and 50% or 10% skin absorption for metribuzin, and pendimethalin and metolachlor, respectively. The three pesticides were quantified by gas chromatography tandem mass spectrometry in all matrices. Metolachlor was used as a tracer of contamination of clothes and tractors unrelated to the exposure monitored. Respiratory exposure to metribuzin, used in granular form, was on average more than one order of magnitude higher than exposure to pendimethalin, used in the form of microencapsulated liquid. The actual doses were 0.067-8.08 µg/kg bw, 0.420-12.6 µg/kg bw, and 0.003-0.877 µg/kg bw for pendimethalin, metribuzin, and metolachlor, respectively. Dermal exposure was about 88% of the actual dose for metribuzin and more than 95%, for pendimethalin and metolachlor. For risk assessment, the total absorbed doses (sum of respiratory and skin absorbed doses) were compared with the AOEL for each compound. The actual and absorbed doses of the three pesticides were always lower than the acceptable operator exposure level (AOEL), which are reported to be 234 µg/kg bw, 20 µg/kg bw, and 150 µg/kg bw for pendimethalin, metribuzin, and metolachlor, respectively. In any case, personal protective equipment and spraying devices should be chosen with care to minimize exposure.

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

Whole-remnant and maximum-voxel SPECT/CT dosimetry in {sup 131}I-NaI treatments of differentiated thyroid cancer

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

Mínguez, Pablo, E-mail: pablo.minguezgabina@osakid

Purpose: To investigate the possible differences between SPECT/CT based whole-remnant and maximum-voxel dosimetry in patients receiving radio-iodine ablation treatment of differentiated thyroid cancer (DTC). Methods: Eighteen DTC patients were administered 1.11 GBq of {sup 131}I-NaI after near-total thyroidectomy and rhTSH stimulation. Two patients had two remnants, so in total dosimetry was performed for 20 sites. Three SPECT/CT scans were performed for each patient at 1, 2, and 3–7 days after administration. The activity, the remnant mass, and the maximum-voxel activity were determined from these images and from a recovery-coefficient curve derived from experimental phantom measurements. The cumulated activity was estimatedmore » using trapezoidal-exponential integration. Finally, the absorbed dose was calculated using S-values for unit-density spheres in whole-remnant dosimetry and S-values for voxels in maximum-voxel dosimetry. Results: The mean absorbed dose obtained from whole-remnant dosimetry was 40 Gy (range 2–176 Gy) and from maximum-voxel dosimetry 34 Gy (range 2–145 Gy). For any given patient, the activity concentrations for each of the three time-points were approximately the same for the two methods. The effective half-lives varied (R = 0.865), mainly due to discrepancies in estimation of the longer effective half-lives. On average, absorbed doses obtained from whole-remnant dosimetry were 1.2 ± 0.2 (1 SD) higher than for maximum-voxel dosimetry, mainly due to differences in the S-values. The method-related differences were however small in comparison to the wide range of absorbed doses obtained in patients. Conclusions: Simple and consistent procedures for SPECT/CT based whole-volume and maximum-voxel dosimetry have been described, both based on experimentally determined recovery coefficients. Generally the results from the two approaches are consistent, although there is a small, systematic difference in the absorbed dose due to differences in the S-values, and some variability due to differences in the estimated effective half-lives, especially when the effective half-life is long. Irrespective of the method used, the patient absorbed doses obtained span over two orders of magnitude.« less

Skeletal dosimetry based on µCT images of trabecular bone: update and comparisons

NASA Astrophysics Data System (ADS)

Kramer, R.; Cassola, V. F.; Vieira, J. W.; Khoury, H. J.; de Oliveira Lira, C. A. B.; Robson Brown, K.

2012-06-01

Two skeletal dosimetry methods using µCT images of human bone have recently been developed: the paired-image radiation transport (PIRT) model introduced by researchers at the University of Florida (UF) in the US and the systematic-periodic cluster (SPC) method developed by researchers at the Federal University of Pernambuco in Brazil. Both methods use µCT images of trabecular bone (TB) to model spongiosa regions of human bones containing marrow cavities segmented into soft tissue volumes of active marrow (AM), trabecular inactive marrow and the bone endosteum (BE), which is a 50 µm thick layer of marrow on all TB surfaces and on cortical bone surfaces next to TB as well as inside the medullary cavities. With respect to the radiation absorbed dose, the AM and the BE are sensitive soft tissues for the induction of leukaemia and bone cancer, respectively. The two methods differ mainly with respect to the number of bone sites and the size of the µCT images used in Monte Carlo calculations and they apply different methods to simulate exposure from radiation sources located outside the skeleton. The PIRT method calculates dosimetric quantities in isolated human bones while the SPC method uses human bones embedded in the body of a phantom which contains all relevant organs and soft tissues. Consequently, the SPC method calculates absorbed dose to the AM and to the BE from particles emitted by radionuclides concentrated in organs or from radiation sources located outside the human body in one calculation step. In order to allow for similar calculations of AM and BE absorbed doses using the PIRT method, the so-called dose response functions (DRFs) have been developed based on absorbed fractions (AFs) of energy for electrons isotropically emitted in skeletal tissues. The DRFs can be used to transform the photon fluence in homogeneous spongiosa regions into absorbed dose to AM and BE. This paper will compare AM and BE AFs of energy from electrons emitted in skeletal tissues calculated with the SPC and the PIRT method and AM and BE absorbed doses and AFs calculated with PIRT-based DRFs and with the SPC method. The results calculated with the two skeletal dosimetry methods agree well if one takes the differences between the two models properly into account. Additionally, the SPC method will be updated with larger µCT images of TB.

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

COBALT-60 Gamma Irradiation of Shrimp.

NASA Astrophysics Data System (ADS)

Sullivan, Nancy L. B.

Meta- and ortho-tyrosine were measured using high performance liquid chromatography (HPLC) in conjunction with electrochemical detection in shrimp irradiated using cobalt-60 gamma radiation in the absorbed dose range 0.8 to 6.0 kGy, in nonirradiated shrimp, and in bovine serum albumin (BSA) irradiated in dilute aqueous solution at 25.0 kGy. Ortho-tyrosine was measured in nonirradiated BSA. Para-, meta-, and ortho-tyrosine were measured using HPLC in conjunction with uv-absorption detection in dilute aqueous solutions of phenylalanine irradiated in the absorbed dose range 16.0 to 195.0 kGy. The measured yields of tyrosine isomers were approximately linear as a function of absorbed dose in shrimp, and in irradiated solutions of phenylalanine up to 37.0 kGy. The occurrence of meta- and ortho-tyrosine, which had formerly been considered unique radiolytic products, has not previously been reported in nonirradiated shrimp or BSA. The conventional hydrolyzation and analytical techniques used in the present study to measure meta- and ortho-tyrosine may provide the basis for a method to detect and determine the dose used in food irradiation.

Dose- and LET-painting with particle therapy.

PubMed

Bassler, Niels; Jäkel, Oliver; Søndergaard, Christian Skou; Petersen, Jørgen B

2010-10-01

Tumour hypoxia is one of the limiting factors in obtaining tumour control in radiotherapy. The high-LET region of a beam of heavy charged particles such as carbon ions is located in the distal part of the Bragg peak. A modulated or spread out Bragg peak (SOBP) is a weighted function of several Bragg peaks at various energies, which however results in a dilution of the dose-average LET in the target volume. Here, we investigate the possibility to redistribute the LET by dedicated treatment plan optimisation, in order to maximise LET in the target volume. This may be a strategy to potentially overcome hypoxia along with dose escalation or dose painting. The high-LET region can be shaped in very different ways, while maintaining the distribution of the absorbed dose or biological effective dose. Treatment plans involving only carbon ion beams, show very different LET distributions depending on how the fields are arranged. Alternatively, a LET boost can be applied in multi-modal treatment planning, such as combining carbon ions with protons and/or photons. For such mixed radiation modalities, significant "LET boosts" can be achieved at nearly arbitrary positions within the target volume. Following the general understanding of the relationship between hypoxia, LET and the oxygen enhancement ratio (OER), we conclude, that an additional therapeutic advantage can be achieved by confining the high-LET part of the radiation in hypoxic compartments of the tumour, and applying low-LET radiation to the normoxic tissue. We also anticipate that additional advantages may be achieved by deliberate sparing of normal tissue from high LET regions. Consequently, treatment planning based on simultaneous dose and LET optimisation has a potential to achieve higher tumour control and/or reduced normal tissue control probability (NTCP).

Tumour control probability derived from dose distribution in homogeneous and heterogeneous models: assuming similar pharmacokinetics, 125Sn-177Lu is superior to 90Y-177Lu in peptide receptor radiotherapy

NASA Astrophysics Data System (ADS)

Walrand, Stephan; Hanin, François-Xavier; Pauwels, Stanislas; Jamar, François

2012-07-01

Clinical trials on 177Lu-90Y therapy used empirical activity ratios. Radionuclides (RN) with larger beta maximal range could favourably replace 90Y. Our aim is to provide RN dose-deposition kernels and to compare the tumour control probability (TCP) of RN combinations. Dose kernels were derived by integration of the mono-energetic beta-ray dose distributions (computed using Monte Carlo) weighted by their respective beta spectrum. Nine homogeneous spherical tumours (1-25 mm in diameter) and four spherical tumours including a lattice of cold, but alive, spheres (1, 3, 5, 7 mm in diameter) were modelled. The TCP for 93Y, 90Y and 125Sn in combination with 177Lu in variable proportions (that kept constant the renal cortex biological effective dose) were derived by 3D dose kernel convolution. For a mean tumour-absorbed dose of 180 Gy, 2 mm homogeneous tumours and tumours including 3 mm diameter cold alive spheres were both well controlled (TCP > 0.9) using a 75-25% combination of 177Lu and 90Y activity. However, 125Sn-177Lu achieved a significantly better result by controlling 1 mm-homogeneous tumour simultaneously with tumours including 5 mm diameter cold alive spheres. Clinical trials using RN combinations should use RN proportions tuned to the patient dosimetry. 125Sn production and its coupling to somatostatin analogue appear feasible. Assuming similar pharmacokinetics 125Sn is the best RN for combination with 177Lu in peptide receptor radiotherapy justifying pharmacokinetics studies in rodent of 125Sn-labelled somatostatin analogues.

Contact radiotherapy using a 50 kV X-ray system: Evaluation of relative dose distribution with the Monte Carlo code PENELOPE and comparison with measurements

NASA Astrophysics Data System (ADS)

Croce, Olivier; Hachem, Sabet; Franchisseur, Eric; Marcié, Serge; Gérard, Jean-Pierre; Bordy, Jean-Marc

2012-06-01

This paper presents a dosimetric study concerning the system named "Papillon 50" used in the department of radiotherapy of the Centre Antoine-Lacassagne, Nice, France. The machine provides a 50 kVp X-ray beam, currently used to treat rectal cancers. The system can be mounted with various applicators of different diameters or shapes. These applicators can be fixed over the main rod tube of the unit in order to deliver the prescribed absorbed dose into the tumor with an optimal distribution. We have analyzed depth dose curves and dose profiles for the naked tube and for a set of three applicators. Dose measurements were made with an ionization chamber (PTW type 23342) and Gafchromic films (EBT2). We have also compared the measurements with simulations performed using the Monte Carlo code PENELOPE. Simulations were performed with a detailed geometrical description of the experimental setup and with enough statistics. Results of simulations are made in accordance with experimental measurements and provide an accurate evaluation of the dose delivered. The depths of the 50% isodose in water for the various applicators are 4.0, 6.0, 6.6 and 7.1 mm. The Monte Carlo PENELOPE simulations are in accordance with the measurements for a 50 kV X-ray system. Simulations are able to confirm the measurements provided by Gafchromic films or ionization chambers. Results also demonstrate that Monte Carlo simulations could be helpful to validate the future applicators designed for other localizations such as breast or skin cancers. Furthermore, Monte Carlo simulations could be a reliable alternative for a rapid evaluation of the dose delivered by such a system that uses multiple designs of applicators.

Optimizing a readout protocol for low dose retrospective OSL-dosimetry using household salt.

PubMed

Christiansson, Maria; Mattsson, Sören; Bernhardsson, Christian; Rääf, Christopher L

2012-06-01

The authors' aim has been to find a single aliquot regenerative dose (SAR) protocol that accurately recovers an unknown absorbed dose in the region between 1-250 mGy in household salt. The main investigation has been conducted on a specific mine salt (>98.5% NaCl) intended for household use, using optical stimulation by blue LED (λ = 462 nm). The most accurate dose recovery for this brand of salt is found to be achieved when using Peak Signal Summing (PSS) of the OSL-decay and a preheat temperature of 200°C after the test dose. A SAR protocol for the household salt with preset values of regenerative doses (R1--R5) and a test dose (TED) of 17 mGy is also suggested here. Under laboratory conditions, the suggested protocol recovers unknown absorbed doses in this particular brand within 5% (2 SD) in the dose range between 1-250 mGy. This is a very promising result for low dose applications of household salt as a retrospective dosimeter after a nuclear or radiological event.

Absorption, Distribution, and Excretion of 14C-APX001 after Single-Dose Administration to Rats and Monkeys

PubMed Central

Mansbach, Robert; Shaw, Karen J; Hodges, Michael R; Coleman, Samantha; Fitzsimmons, Michael E

2017-01-01

Abstract Background APX001 is a small-molecule therapeutic agent in clinical development for the treatment of invasive fungal infections (IFI). Methods The absorption, distribution and excretion profiles of [14C]APX001-derived radioactivity were determined in rats (albino and pigmented) and monkeys. Rats (some implanted with bile duct cannulae) were administered a single 100 mg/kg oral dose or a 30 mg/kg intravenous (IV) dose. Monkeys were administered a single 6 mg/kg IV dose. Samples of blood, urine, feces and bile, as well as carcasses, were collected through 168 hours after dosing. Samples were analyzed for total radioactivity content by liquid scintillation counting, and carcasses were analyzed by quantitative whole-body autoradiography. Results [14C]APX001-derived radioactivity was rapidly and extensively absorbed and extensively distributed to most tissues for both routes of administration in both species. In rats, tissues with the highest radioactivity Cmax values included bile, abdominal fat, reproductive fat, subcutaneous fat, and liver, but radioactivity was also detected in tissues associated with IFI, including lung, brain and eye. In monkeys, the highest Cmax values were in bile, urine, uveal tract, bone marrow, abdominal fat, liver, and kidney cortex. Liver and kidney were the tissues with highest radioactivity, but as in the rat, radioactivity was also detected in lung, brain and eye tissues. In pigmented rats, radiocarbon was densely distributed into pigmented tissue and more slowly cleared than from other tissues. Mean recovery of radioactivity in rats was approximately 95–100%. In bile duct-intact rats, >90% of radioactivity was recovered in feces. In cannulated rats, biliary excretion of radioactivity was the major route of elimination and accounted for 88.8% of the dose, whereas urinary and fecal excretion of radioactivity was minor and accounted for 2.56% and 5.42% of the dose, respectively. In monkeys, the overall recovery of radioactivity was 87.6%, and was eliminated in feces (49.8% of dose) and to a lesser extent in urine (20.6% of dose). Conclusion Together, the results indicate that APX001-related radioactivity is extensively distributed to major tissues (including tissues relevant to IFI) in both rats and monkeys and cleared primarily by biliary/fecal excretion. Disclosures R. Mansbach, Amplyx Pharmaceuticals Inc.: Consultant, Consulting fee; K. J. Shaw, Amplyx Pharmaceuticals Inc.: Employee, Salary; M. R. Hodges, Amplyx Pharmaceuticals: Employee, Salary; S. Coleman, Covance Laboratories: Employee, Salary; M. E. Fitzsimmons, Covance Laboratories: Employee, Salary

The FLUKA Monte Carlo code coupled with the NIRS approach for clinical dose calculations in carbon ion therapy

NASA Astrophysics Data System (ADS)

Magro, G.; Dahle, T. J.; Molinelli, S.; Ciocca, M.; Fossati, P.; Ferrari, A.; Inaniwa, T.; Matsufuji, N.; Ytre-Hauge, K. S.; Mairani, A.

2017-05-01

Particle therapy facilities often require Monte Carlo (MC) simulations to overcome intrinsic limitations of analytical treatment planning systems (TPS) related to the description of the mixed radiation field and beam interaction with tissue inhomogeneities. Some of these uncertainties may affect the computation of effective dose distributions; therefore, particle therapy dedicated MC codes should provide both absorbed and biological doses. Two biophysical models are currently applied clinically in particle therapy: the local effect model (LEM) and the microdosimetric kinetic model (MKM). In this paper, we describe the coupling of the NIRS (National Institute for Radiological Sciences, Japan) clinical dose to the FLUKA MC code. We moved from the implementation of the model itself to its application in clinical cases, according to the NIRS approach, where a scaling factor is introduced to rescale the (carbon-equivalent) biological dose to a clinical dose level. A high level of agreement was found with published data by exploring a range of values for the MKM input parameters, while some differences were registered in forward recalculations of NIRS patient plans, mainly attributable to differences with the analytical TPS dose engine (taken as reference) in describing the mixed radiation field (lateral spread and fragmentation). We presented a tool which is being used at the Italian National Center for Oncological Hadrontherapy to support the comparison study between the NIRS clinical dose level and the LEM dose specification.

The leaded apron revisited: does it reduce gonadal radiation dose in dental radiology?

PubMed

Wood, R E; Harris, A M; van der Merwe, E J; Nortjé, C J

1991-05-01

A tissue-equivalent anthropomorphic human phantom was used with a lithium fluoride thermoluminescent dosimetry system to evaluate the radiation absorbed dose to the ovarian and testicular region during dental radiologic procedures. Measurements were made with and without personal lead shielding devices consisting of thyroid collar and apron of 0.25 mm lead thickness equivalence. The radiation absorbed dose with or without lead shielding did not differ significantly from control dosimeters in vertex occlusal and periapical views (p greater than 0.05). Personal lead shielding devices did reduce gonadal dose in the case of accidental exposure (p less than 0.05). A leaded apron of 0.25 mm lead thickness equivalent was permeable to radiation in direct exposure testing.

In Vitro comparison of 213Bi- and 177Lu-radiation for peptide receptor radionuclide therapy.

PubMed

Chan, Ho Sze; de Blois, Erik; Morgenstern, Alfred; Bruchertseifer, Frank; de Jong, Marion; Breeman, Wouter; Konijnenberg, Mark

2017-01-01

Absorbed doses for α-emitters are different from those for β-emitters, as the high linear energy transfer (LET) nature of α-particles results in a very dense energy deposition over a relatively short path length near the point of emission. This highly localized and therefore high energy deposition can lead to enhanced cell-killing effects at absorbed doses that are non-lethal in low-LET type of exposure. Affinities of DOTA-DPhe1-Tyr3-octreotate (DOTATATE), 115In-DOTATATE, 175Lu-DOTATATE and 209Bi-DOTATATE were determined in the K562-SST2 cell line. Two other cell lines were used for radiation response assessment; BON and CA20948, with a low and high expression of somatostatin receptors, respectively. Cellular uptake kinetics of 111In-DOTATATE were determined in CA20948 cells. CA20948 and BON were irradiated with 137Cs, 177Lu-DTPA, 177Lu-DOTATATE, 213Bi-DTPA and 213Bi-DOTATATE. Absorbed doses were calculated using the MIRDcell dosimetry method for the specific binding and a Monte Carlo model of a cylindrical 6-well plate geometry for the exposure by the radioactive incubation medium. Absorbed doses were compared to conventional irradiation of cells with 137Cs and the relative biological effect (RBE) at 10% survival was calculated. IC50 of (labelled) DOTATATE was in the nM range. Absorbed doses up to 7 Gy were obtained by 5.2 MBq 213Bi-DOTATATE, in majority the dose was caused by α-particle radiation. Cellular internalization determined with 111In-DOTATATE showed a linear relation with incubation time. Cell survival after exposure of 213Bi-DTPA and 213Bi-DOTATATE to BON or CA20948 cells showed a linear-exponential relation with the absorbed dose, confirming the high LET character of 213Bi. The survival of CA20948 after exposure to 177Lu-DOTATATE and the reference 137Cs irradiation showed the typical curvature of the linear-quadratic model. 10% Cell survival of CA20948 was reached at 3 Gy with 213Bi-DOTATATE, a factor 6 lower than the 18 Gy found for 177Lu-DOTATATE and also below the 5 Gy after 137Cs external exposure. 213Bi-DTPA and 213Bi-DOTATATE lead to a factor 6 advantage in cell killing compared to 177Lu-DOTATATE. The RBE at 10% survival by 213Bi-ligand compared to 137Cs was 2.0 whereas the RBE for 177Lu-DOTATATE was 0.3 in the CA20948 in vitro model.

In Vitro comparison of 213Bi- and 177Lu-radiation for peptide receptor radionuclide therapy

PubMed Central

de Blois, Erik; Morgenstern, Alfred; Bruchertseifer, Frank; de Jong, Marion; Breeman, Wouter; Konijnenberg, Mark

2017-01-01

Background Absorbed doses for α-emitters are different from those for β-emitters, as the high linear energy transfer (LET) nature of α-particles results in a very dense energy deposition over a relatively short path length near the point of emission. This highly localized and therefore high energy deposition can lead to enhanced cell-killing effects at absorbed doses that are non-lethal in low-LET type of exposure. Affinities of DOTA-DPhe1-Tyr3-octreotate (DOTATATE), 115In-DOTATATE, 175Lu-DOTATATE and 209Bi-DOTATATE were determined in the K562-SST2 cell line. Two other cell lines were used for radiation response assessment; BON and CA20948, with a low and high expression of somatostatin receptors, respectively. Cellular uptake kinetics of 111In-DOTATATE were determined in CA20948 cells. CA20948 and BON were irradiated with 137Cs, 177Lu-DTPA, 177Lu-DOTATATE, 213Bi-DTPA and 213Bi-DOTATATE. Absorbed doses were calculated using the MIRDcell dosimetry method for the specific binding and a Monte Carlo model of a cylindrical 6-well plate geometry for the exposure by the radioactive incubation medium. Absorbed doses were compared to conventional irradiation of cells with 137Cs and the relative biological effect (RBE) at 10% survival was calculated. Results IC50 of (labelled) DOTATATE was in the nM range. Absorbed doses up to 7 Gy were obtained by 5.2 MBq 213Bi-DOTATATE, in majority the dose was caused by α-particle radiation. Cellular internalization determined with 111In-DOTATATE showed a linear relation with incubation time. Cell survival after exposure of 213Bi-DTPA and 213Bi-DOTATATE to BON or CA20948 cells showed a linear-exponential relation with the absorbed dose, confirming the high LET character of 213Bi. The survival of CA20948 after exposure to 177Lu-DOTATATE and the reference 137Cs irradiation showed the typical curvature of the linear-quadratic model. 10% Cell survival of CA20948 was reached at 3 Gy with 213Bi-DOTATATE, a factor 6 lower than the 18 Gy found for 177Lu-DOTATATE and also below the 5 Gy after 137Cs external exposure. Conclusion 213Bi-DTPA and 213Bi-DOTATATE lead to a factor 6 advantage in cell killing compared to 177Lu-DOTATATE. The RBE at 10% survival by 213Bi-ligand compared to 137Cs was 2.0 whereas the RBE for 177Lu-DOTATATE was 0.3 in the CA20948 in vitro model. PMID:28732021

The advantages of absorbed-dose calibration factors.

PubMed

Rogers, D W

1992-01-01

A formalism for clinical external beam dosimetry based on use of ion chamber absorbed-dose calibration factors is outlined in the context and notation of the AAPM TG-21 protocol. It is shown that basing clinical dosimetry on absorbed-dose calibration factors ND leads to considerable simplification and reduced uncertainty in dose measurement. In keeping with a protocol which is used in Germany, a quantity kQ is defined which relates an absorbed-dose calibration factor in a beam of quality Q0 to that in a beam of quality Q. For 38 cylindrical ion chambers, two sets of values are presented for ND/NX and Ngas/ND and for kQ for photon beams with beam quality specified by the TPR20(10) ratio. One set is based on TG-21's protocol to allow the new formalism to be used while maintaining equivalence to the TG-21 protocol. To demonstrate the magnitude of the overall error in the TG-21 protocol, the other set uses corrected versions of the TG-21 equations and the more consistent physical data of the IAEA Code of Practice. Comparisons are made to procedures based on air-kerma or exposure calibration factors and it is shown that accuracy and simplicity are gained by avoiding the determination of Ngas from NX. It is also shown that the kQ approach simplifies the use of plastic phantoms in photon beams since kQ values change by less than 0.6% compared to those in water although an overall correction factor of 0.973 is needed to go from absorbed dose in water calibration factors to those in PMMA or polystyrene. Values of kQ calculated using the IAEA Code of Practice are presented but are shown to be anomalous because of the way the effective point of measurement changes for 60Co beams. In photon beams the major difference between the IAEA Code of Practice and the corrected AAPM TG-21 protocol is shown to be the Prepl correction factor. Calculated kQ curves and three parameter equations for them are presented for each wall material and are shown to represent accurately the kQ curve for all ion chambers in this study with a wall of that specified material and a thickness less than 0.25 g/cm2. Values of kQ can be measured using the primary standards for absorbed dose in photon beams.

SU-E-T-507: Internal Dosimetry in Nuclear Medicine Using GATE and XCAT Phantom: A Simulation Study

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

Fallahpoor, M; Abbasi, M; Sen, A

Purpose Monte Carlo simulations are routinely used for internal dosimetry studies. These studies are conducted with humanoid phantoms such as the XCAT phantom. In this abstract we present the absorbed doses for various pairs of source and target organs using three common radiotracers in nuclear medicine. Methods The GATE software package is used for the Monte Carlo simulations. A typical female XCAT phantom is used as the input. Three radiotracers 153Sm, 131I and 99mTc are studied. The Specific Absorbed Fraction (SAF) for gamma rays (99mTc, 153Sm and 131I) and Specific Fraction (SF) for beta particles (153Sm and 131I) are calculatedmore » for all 100 pairs of source target organs including brain, liver, lung, pancreas, kidney, adrenal, spleen, rib bone, bladder and ovaries. Results The source organs themselves gain the highest absorbed dose as compared to other organs. The dose is found to be inversely proportional to distance from the source organ. In SAF results of 153Sm, when the source organ is lung, the rib bone, gain 0.0730 (Kg-1) that is more than lung itself. Conclusion The absorbed dose for various organs was studied in terms of SAF and SF. Such studies hold importance for future therapeutic procedures and optimization of induced radiotracer.« less

Study the Characterization of Spectral Absorbance on Irradiated Milk Protein

NASA Astrophysics Data System (ADS)

Fohely, F.; Suardi, N.

2018-04-01

The milk has been adopted as a structural nature food for a long era since it is containing most of the growth factors, protective agents, and enzymes needed for the body. a few attempts have been conducted to treat the dairy products especially raw milk by the means of ionizing radiation. as its production has been an expanding industry for many years due to the high demands from the consumers worldwide, there is still some doubt about preserving these products by irradiation. In this work, a preliminary effort to describe the influences of ionizing radiation on raw milk’s protein will be devoted to measuring the spectral absorbance of the total protein (after subjected to varied radiation doses) by UV-VIS-NIR spectroscopy analysis. The absorbance spectrum then analyzed based on absorbance spectra of organic compounds. A comparison is made between the effects of different radiation doses to estimate the influence in milk’s structure.

Space Radiation and its Associated Health Consequences

NASA Technical Reports Server (NTRS)

Wu, Honglu

2007-01-01

During space travel, astronauts are exposed to energetic particles of a complex composition and energy distribution. For the same amount of absorbed dose, these particles can be much more effective than X- or gamma rays in the induction of biological effects, including cell inactivation, genetic mutations, cataracts, and cancer induction. Several of the biological consequences of space radiation exposure have already been observed in astronauts. This presentation will introduce the space radiation environment and discuss its associated health risks. Accurate assessment of the radiation risks and development of respective countermeasures are essential for the success of future exploration missions to the Moon and Mars.

Microionization chamber for reference dosimetry in IMRT verification: clinical implications on OAR dosimetric errors

NASA Astrophysics Data System (ADS)

Sánchez-Doblado, Francisco; Capote, Roberto; Leal, Antonio; Roselló, Joan V.; Lagares, Juan I.; Arráns, Rafael; Hartmann, Günther H.

2005-03-01

Intensity modulated radiotherapy (IMRT) has become a treatment of choice in many oncological institutions. Small fields or beamlets with sizes of 1 to 5 cm2 are now routinely used in IMRT delivery. Therefore small ionization chambers (IC) with sensitive volumes <=0.1 cm3are generally used for dose verification of an IMRT treatment. The measurement conditions during verification may be quite different from reference conditions normally encountered in clinical beam calibration, so dosimetry of these narrow photon beams pertains to the so-called non-reference conditions for beam calibration. This work aims at estimating the error made when measuring the organ at risk's (OAR) absolute dose by a micro ion chamber (μIC) in a typical IMRT treatment. The dose error comes from the assumption that the dosimetric parameters determining the absolute dose are the same as for the reference conditions. We have selected two clinical cases, treated by IMRT, for our dose error evaluations. Detailed geometrical simulation of the μIC and the dose verification set-up was performed. The Monte Carlo (MC) simulation allows us to calculate the dose measured by the chamber as a dose averaged over the air cavity within the ion-chamber active volume (Dair). The absorbed dose to water (Dwater) is derived as the dose deposited inside the same volume, in the same geometrical position, filled and surrounded by water in the absence of the ion chamber. Therefore, the Dwater/Dair dose ratio is the MC estimator of the total correction factor needed to convert the absorbed dose in air into the absorbed dose in water. The dose ratio was calculated for the μIC located at the isocentre within the OARs for both clinical cases. The clinical impact of the calculated dose error was found to be negligible for the studied IMRT treatments.

Use of computer code for dose distribution studies in A 60CO industrial irradiator

NASA Astrophysics Data System (ADS)

Piña-Villalpando, G.; Sloan, D. P.

1995-09-01

This paper presents a benchmark comparison between calculated and experimental absorbed dose values tor a typical product, in a 60Co industrial irradiator, located at ININ, México. The irradiator is a two levels, two layers system with overlapping product configuration with activity around 300kCi. Experimental values were obtanied from routine dosimetry, using red acrylic pellets. Typical product was Petri dishes packages, apparent density 0.13 g/cm3; that product was chosen because uniform size, large quantity and low density. Minimum dose was fixed in 15 kGy. Calculated values were obtained from QAD-CGGP code. This code uses a point kernel technique, build-up factors fitting was done by geometrical progression and combinatorial geometry is used for system description. Main modifications for the code were related with source sumilation, using punctual sources instead of pencils and an energy and anisotropic emission spectrums were included. Results were, for maximum dose, calculated value (18.2 kGy) was 8% higher than experimental average value (16.8 kGy); for minimum dose, calculated value (13.8 kGy) was 3% higher than experimental average value (14.3 kGy).

Gamma-Ray Dose Measurement with Radio-Photoluminescence Glass Dosimeter in Mixed Radiation Field for BNCT

NASA Astrophysics Data System (ADS)

Hiramatsu, K.; Yoshihashi, S.; Kusaka, S.; Sato, F.; Hoashi, E.; Murata, I.

2017-09-01

Accelerator based neutron sources (ABNS) are being developed as the next generation neutron irradiation system for BNCT. From the ABNS, unnecessary gamma-rays will be generated by neutron capture reactions, as well as fast neutrons. To control the whole-body radiation dose to the patient, measurement of gamma-ray dose in the irradiation room is necessary. In this study, the objective is to establish a method to measure gamma-ray dose separately in a neutron/gamma mixed field by using RPL glass dosimeter. For this purpose, we proposed a lead filter method which uses a pair of RPL glasses with and without a lead filter outside. In order to realize this method, the basic characteristics of glass dosimeter was verified in the gamma-ray field, before adapting it in the mixture field. From the result of the experiment using the lead filter, the simulation result especially for the case with a lead filter overestimated the absorbed does obtained from measurement. We concluded that the reason of the discrepancy is caused by existence of gradient of the dose distribution in the glass, and the difference of sensitivity to low-energy photon between measurement and theory.

Computational assessment of effective dose and patient specific doses for kilovoltage stereotactic radiosurgery of wet age-related macular degeneration

NASA Astrophysics Data System (ADS)

Hanlon, Justin Mitchell

Age-related macular degeneration (AMD) is a leading cause of vision loss and a major health problem for people over the age of 50 in industrialized nations. The current standard of care, ranibizumab, is used to help slow and in some cases stabilize the process of AMD, but requires frequent invasive injections into the eye. Interest continues for stereotactic radiosurgery (SRS), an option that provides a non-invasive treatment for the wet form of AMD, through the development of the IRay(TM) (Oraya Therapeutics, Inc., Newark, CA). The goal of this modality is to destroy choroidal neovascularization beneath the pigment epithelium via delivery of three 100 kVp photon beams entering through the sclera and overlapping on the macula delivering up to 24 Gy of therapeutic dose over a span of approximately 5 minutes. The divergent x-ray beams targeting the fovea are robotically positioned and the eye is gently immobilized by a suction-enabled contact lens. Device development requires assessment of patient effective dose, reference patient mean absorbed doses to radiosensitive tissues, and patient specific doses to the lens and optic nerve. A series of head phantoms, including both reference and patient specific, was derived from CT data and employed in conjunction with the MCNPX 2.5.0 radiation transport code to simulate treatment and evaluate absorbed doses to potential tissues-at-risk. The reference phantoms were used to evaluate effective dose and mean absorbed doses to several radiosensitive tissues. The optic nerve was modeled with changeable positions based on individual patient variability seen in a review of head CT scans gathered. Patient specific phantoms were used to determine the effect of varying anatomy and gaze. The results showed that absorbed doses to the non-targeted tissues were below the threshold levels for serious complications; specifically the development of radiogenic cataracts and radiation induced optic neuropathy (RON). The effective dose determined (0.29 mSv) is comparable to diagnostic procedures involving the head, such as an x-ray or CT scan. Thus, the computational assessment performed indicates that a previously established therapeutic dose can be delivered effectively to the macula with IRay(TM) without the potential for secondary complications.

Development of a dual phantom technique for measuring the fast neutron component of dose in boron neutron capture therapy.

PubMed

Sakurai, Yoshinori; Tanaka, Hiroki; Kondo, Natsuko; Kinashi, Yuko; Suzuki, Minoru; Masunaga, Shinichiro; Ono, Koji; Maruhashi, Akira

2015-11-01

Research and development of various accelerator-based irradiation systems for boron neutron capture therapy (BNCT) is underway throughout the world. Many of these systems are nearing or have started clinical trials. Before the start of treatment with BNCT, the relative biological effectiveness (RBE) for the fast neutrons (over 10 keV) incident to the irradiation field must be estimated. Measurements of RBE are typically performed by biological experiments with a phantom. Although the dose deposition due to secondary gamma rays is dominant, the relative contributions of thermal neutrons (below 0.5 eV) and fast neutrons are virtually equivalent under typical irradiation conditions in a water and/or acrylic phantom. Uniform contributions to the dose deposited from thermal and fast neutrons are based in part on relatively inaccurate dose information for fast neutrons. This study sought to improve the accuracy in the dose estimation for fast neutrons by using two phantoms made of different materials in which the dose components can be separated according to differences in the interaction cross sections. The development of a "dual phantom technique" for measuring the fast neutron component of dose is reported. One phantom was filled with pure water. The other phantom was filled with a water solution of lithium hydroxide (LiOH) capitalizing on the absorbing characteristics of lithium-6 (Li-6) for thermal neutrons. Monte Carlo simulations were used to determine the ideal mixing ratio of Li-6 in LiOH solution. Changes in the depth dose distributions for each respective dose component along the central beam axis were used to assess the LiOH concentration at the 0, 0.001, 0.01, 0.1, 1, and 10 wt. % levels. Simulations were also performed with the phantom filled with 10 wt. % 6LiOH solution for 95%-enriched Li-6. A phantom was constructed containing 10 wt. % 6LiOH solution based on the simulation results. Experimental characterization of the depth dose distributions of the neutron and gamma-ray components along the central axis was performed at Heavy Water Neutron Irradiation Facility installed at Kyoto University Reactor using activation foils and thermoluminescent dosimeters, respectively. Simulation results demonstrated that the absorbing effect for thermal neutrons occurred when the LiOH concentration was over 1%. The most effective Li-6 concentration was determined to be enriched 6LiOH with a solubility approaching its upper limit. Experiments confirmed that the thermal neutron flux and secondary gamma-ray dose rate decreased substantially; however, the fast neutron flux and primary gamma-ray dose rate were hardly affected in the 10%-6LiOH phantom. It was confirmed that the dose contribution of fast neutrons is improved from approximately 10% in the pure water phantom to approximately 50% in the 10%-6LiOH phantom. The dual phantom technique using the combination of a pure water phantom and a 10%-6LiOH phantom developed in this work provides an effective method for dose estimation of the fast neutron component in BNCT. Improvement in the accuracy achieved with the proposed technique results in improved RBE estimation for biological experiments and clinical practice.

Radiometric surveying for the assessment of radiation dose and radon specific exhalation in underground environment

NASA Astrophysics Data System (ADS)

Bochiolo, M.; Verdoya, M.; Chiozzi, P.; Pasquale, V.

2012-08-01

We performed a radiometric survey for evaluating the natural radioactivity and the related potential hazard level both outdoor and indoor a mine tunnel. The mine is located in a zone of uranium enrichment in the Western Alps (Italy). At first, a γ-ray spectrometry survey of the area surrounding the mine was carried out to define the extent of the ore deposit. Then, spectrometric measurements were performed in the tunnel and rock samples were collected for laboratory analyses. The results point to significant heterogeneity in uranium concentration and consequently in the absorbed dose rate spatial distribution. Spectrometric results in situ and in the laboratory, together with radon air concentration measurements, were used to infer the radon specific exhalation and flow from the mine rocks. The specific exhalation is positively related to the activity concentration of uranium.

Monte Carlo based dosimetry for neutron capture therapy of brain tumors

NASA Astrophysics Data System (ADS)

Zaidi, Lilia; Belgaid, Mohamed; Khelifi, Rachid

2016-11-01

Boron Neutron Capture Therapy (BNCT) is a biologically targeted, radiation therapy for cancer which combines neutron irradiation with a tumor targeting agent labeled with a boron10 having a high thermal neutron capture cross section. The tumor area is subjected to the neutron irradiation. After a thermal neutron capture, the excited 11B nucleus fissions into an alpha particle and lithium recoil nucleus. The high Linear Energy Transfer (LET) emitted particles deposit their energy in a range of about 10μm, which is of the same order of cell diameter [1], at the same time other reactions due to neutron activation with body component are produced. In-phantom measurement of physical dose distribution is very important for BNCT planning validation. Determination of total absorbed dose requires complex calculations which were carried out using the Monte Carlo MCNP code [2].

Electron absorbed fractions of energy and S-values in an adult human skeleton based on µCT images of trabecular bone

NASA Astrophysics Data System (ADS)

Kramer, R.; Richardson, R. B.; Cassola, V. F.; Vieira, J. W.; Khoury, H. J.; Lira, C. A. B. de O.; Robson Brown, K.

2011-03-01

When the human body is exposed to ionizing radiation, among the soft tissues at risk are the active marrow (AM) and the bone endosteum (BE) located in tiny, irregular cavities of trabecular bone. Determination of absorbed fractions (AFs) of energy or absorbed dose in the AM and the BE represent one of the major challenges of dosimetry. Recently, at the Department of Nuclear Energy at the Federal University of Pernambuco, a skeletal dosimetry method based on µCT images of trabecular bone introduced into the spongiosa voxels of human phantoms has been developed and applied mainly to external exposure to photons. This study uses the same method to calculate AFs of energy and S-values (absorbed dose per unit activity) for electron-emitting radionuclides known to concentrate in skeletal tissues. The modelling of the skeletal tissue regions follows ICRP110, which defines the BE as a 50 µm thick sub-region of marrow next to the bone surfaces. The paper presents mono-energetic AFs for the AM and the BE for eight different skeletal regions for electron source energies between 1 keV and 10 MeV. The S-values are given for the beta emitters 14C, 59Fe, 131I, 89Sr, 32P and 90Y. Comparisons with results from other investigations showed good agreement provided that differences between methodologies and trabecular bone volume fractions were properly taken into account. Additionally, a comparison was made between specific AFs of energy in the BE calculated for the actual 50 µm endosteum and the previously recommended 10 µm endosteum. The increase in endosteum thickness leads to a decrease of the endosteum absorbed dose by up to 3.7 fold when bone is the source region, while absorbed dose increases by ~20% when the beta emitters are in marrow.

CT dose equilibration and energy absorption in polyethylene cylinders with diameters from 6 to 55 cm

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

Li, Xinhua; Zhang, Da; Liu, Bob, E-mail: bliu7@mgh.harvard.edu

2015-06-15

Purpose: ICRU Report No. 87 Committee and AAPM Task Group 200 designed a three-sectional polyethylene phantom of 30 cm in diameter and 60 cm in length for evaluating the midpoint dose D{sub L}(0) and its rise-to-the-equilibrium curve H(L) = D{sub L}(0)/D{sub eq} from computed tomography (CT) scanning, where D{sub eq} is the equilibrium dose. To aid the use of the phantom in radiation dose assessment and to gain an understanding of dose equilibration and energy absorption in polyethylene, the authors evaluated the short (20 cm) to long (60 cm) phantom dose ratio with a polyethylene diameter of 30 cm, assessedmore » H(L) in polyethylene cylinders of 6–55 cm in diameters, and examined energy absorption in these cylinders. Methods: A GEANT4-based Monte Carlo program was used to simulate the single axial scans of polyethylene cylinders (diameters 6–55 cm and length 90 cm, as well as diameter 30 cm and lengths 20 and 60 cm) on a clinical CT scanner (Somatom Definition dual source CT, Siemens Healthcare). Axial dose distributions were computed on the phantom central and peripheral axes. An average dose over the central 23 or 100 mm region was evaluated for modeling dose measurement using a 0.6 cm{sup 3} thimble chamber or a 10 cm long pencil ion chamber, respectively. The short (20 cm) to long (90 cm) phantom dose ratios were calculated for the 30 cm diameter polyethylene phantoms scanned at four tube voltages (80–140 kV) and a range of beam apertures (1–25 cm). H(L) was evaluated using the dose integrals computed with the 90 cm long phantoms. The resultant H(L) data were subsequently used to compute the fraction of the total energy absorbed inside or outside the scan range (E{sub in}/E or E{sub out}/E) on the phantom central and peripheral axes, where E = LD{sub eq} was the total energy absorbed along the z axis. Results: The midpoint dose in the 60 cm long polyethylene phantom was equal to that in the 90 cm long polyethylene phantom. The short-to-long phantom dose ratios changed with beam aperture and phantom axis but were insensitive to tube voltage. H(L) was insensitive to tube voltage and CT scanner model. As phantom diameter increased from 6 to 55 cm, E{sub in}/E generally decreased but asymptotically approached constant levels on the peripheral axes of large phantoms. The curve of E{sub in}/E versus scan length was almost identical to that of H(L). Similarly, E{sub out}/E increased with scan length and asymptotically approached the equilibrium for large scan lengths. E{sub out}/D{sub eq} was much less than the equilibrium length L{sub eq} where H(L) = 0.98, even with scan lengths much larger than L{sub eq}. Conclusions: The polyethylene phantom designed by ICRU Report No. 87 Committee and AAPM Task Group 200 is adequately long for assessing the midpoint dose and its equilibration in CT scanning. The short-to-long phantom dose ratios and the H(L) data provided in this paper allow easy evaluations of the midpoint dose, longitudinal dose distribution, and energy absorption in polyethylene phantoms. The results of dose equilibration and energy absorption presented herein may be insightful for the clinical CT scans with various subject sizes and scan lengths.« less

Developmental toxicity study of D-tagatose in rats.

PubMed

Kruger, C L; Whittaker, M H; Frankos, V H; Schroeder, R E

1999-04-01

D-tagatose is a low-calorie sweetener that tastes like sucrose. The developmental toxicity of D-tagatose was investigated in Crl:CD(SD)BR rats administered D-tagatose at three dose levels (4000, 12,000, and 20,000 mg/kg body wt/day) via gastric intubation on days 6-15 of gestation. No compound-related toxicity was seen among any of the maternal groups. No treatment-related clinical effects were seen in the maternal animals at the 4000 mg/kg/day dose level. At the mid- and high-dose levels, most maternal animals had unformed or watery stools; this effect was most prominent early in the treatment period (Gestation Days 6-8). This effect was attributed to the osmotic effect of the large amount of D-tagatose given to the animals at these doses. Since D-tagatose is not digested or absorbed to a large extent, most of the sugar passes into the colon where it absorbs water and is fermented by colonic bacteria. Mean weight gain for the low- and mid-dose animals was comparable to the control; however, the high-dose group experienced a mean weight loss over the Gestation Day 6-9 interval. Over the entire treatment interval, however, mean weight gain for the high-dose animals was comparable to control. The decreased weight gain in the high-dose animals during the Gestation Day 6-9 interval was considered to be a direct result of laxation. In addition to the effect of laxation on body weight, reduced food consumption also contributed to the decreased weight gain. In the low-dose animals, no effect on food consumption was seen; however, both mid- and high-dose animals had food consumption values that were statistically significantly lower than the control. Food consumption was lowest during the Gestation Day 6-9 interval, the period when laxation was most prominent. Food consumption rebounded and was statistically significantly higher than the control for the mid- and high-dose animals during the posttreatment interval. Maternal liver weight for the low-dose animals was comparable to the control. However, a statistically significant increase in mean maternal liver weight was noted for the mid-and high-dose animals. Based on a lack of any corresponding histopathology, the increased liver weights were not considered toxicologically significant. There were no adverse effects on reproductive performance noted in any treatment group. No adverse treatment-related fetal effects on fetal weight, sex distribution, liver weight, or external, skeletal, or visceral malformations were noted at any dose level. Copyright 1999 Academic Press.

Absolute dosimetry on a dynamically scanned sample for synchrotron radiotherapy using graphite calorimetry and ionization chambers

NASA Astrophysics Data System (ADS)

Lye, J. E.; Harty, P. D.; Butler, D. J.; Crosbie, J. C.; Livingstone, J.; Poole, C. M.; Ramanathan, G.; Wright, T.; Stevenson, A. W.

2016-06-01

The absolute dose delivered to a dynamically scanned sample in the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter anticipated to be established as a primary standard for synchrotron dosimetry. The calorimetry was compared to measurements using a free-air chamber (FAC), a PTW 31 014 Pinpoint ionization chamber, and a PTW 34 001 Roos ionization chamber. The IMBL beam height is limited to approximately 2 mm. To produce clinically useful beams of a few centimetres the beam must be scanned in the vertical direction. In practice it is the patient/detector that is scanned and the scanning velocity defines the dose that is delivered. The calorimeter, FAC, and Roos chamber measure the dose area product which is then converted to central axis dose with the scanned beam area derived from Monte Carlo (MC) simulations and film measurements. The Pinpoint chamber measures the central axis dose directly and does not require beam area measurements. The calorimeter and FAC measure dose from first principles. The calorimetry requires conversion of the measured absorbed dose to graphite to absorbed dose to water using MC calculations with the EGSnrc code. Air kerma measurements from the free air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. The two ionization chambers are secondary standards requiring calibration with kilovoltage x-ray tubes. The Roos and Pinpoint chambers were calibrated against the Australian primary standard for air kerma at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Agreement of order 2% or better was obtained between the calorimetry and ionization chambers. The FAC measured a dose 3-5% higher than the calorimetry, within the stated uncertainties.

Evaluation of factors to convert absorbed dose calibrations from graphite to water for the NPL high-energy photon calibration service.

PubMed

Nutbrown, R F; Duane, S; Shipley, D R; Thomas, R A S

2002-02-07

The National Physical Laboratory (NPL) provides a high-energy photon calibration service using 4-19 MV x-rays and 60Co gamma-radiation for secondary standard dosemeters in terms of absorbed dose to water. The primary standard used for this service is a graphite calorimeter and so absorbed dose calibrations must be converted from graphite to water. The conversion factors currently in use were determined prior to the launch of this service in 1988. Since then, it has been found that the differences in inherent filtration between the NPL LINAC and typical clinical machines are large enough to affect absorbed dose calibrations and, since 1992, calibrations have been performed in heavily filtered qualities. The conversion factors for heavily filtered qualities were determined by interpolation and extrapolation of lightly filtered results as a function of tissue phantom ratio 20,10 (TPR20,10). This paper aims to evaluate these factors for all mega-voltage photon energies provided by the NPL LINAC for both lightly and heavily filtered qualities and for 60Co y-radiation in two ways. The first method involves the use of the photon fluence-scaling theorem. This states that if two blocks of different material are irradiated by the same photon beam, and if all dimensions are scaled in the inverse ratio of the electron densities of the two media, then, assuming that all photon interactions occur by Compton scatter the photon attenuation and scatter factors at corresponding scaled points of measurement in the phantom will be identical. The second method involves making in-phantom measurements of chamber response at a constant target-chamber distance. Monte Carlo techniques are then used to determine the corresponding dose to the medium in order to determine the chamber calibration factor directly. Values of the ratio of absorbed dose calibration factors in water and in graphite determined in these two ways agree with each other to within 0.2% (1sigma uncertainty). The best fit to both sets of results agrees with values determined in previous work to within 0.3% (1sigma uncertainty). It is found that the conversion factor is not sensitive to beam filtration.

Errors in the absorbed and the administered 131I therapeutic dose in patients with Graves' disease. A suggested more precise technique.

PubMed

Chen, Yangchun; Huang, Jincheng; Wang, Yuehui; Xie, Sipei; He, Fang

2017-01-01

The aim of this study was to evaluate the relative error (RE) in the thyroid absorbed dose (TD) of iodine-131 ( 131 I) in patients with Graves' disease comparing the simplified Quimby-Marinelli-Hine formula method (sQMHF) and the Standard Operational Procedures for dosimetry (SOPD) recommended by the European Association of Nuclear Medicine. This study included 45 patients with Graves' disease 12 men and 33 women; age 44.1±12.8 years. Thyroid mass (TM) was measured using ultrasound. Uptake of 131 I (RAIU) was tested at 2, 4-6, 24, 48-72, and 96-168h after its administration and the half-life (T 1/2eff ) and resident time (RT) of 131 I were computed. According to the sQMHF, a prescribed TD of 75Gy required 3.7MBq/g of 131 I, correction based on the RAIU 24h and T 1/2eff . Subsequently, the therapeutic TD was computed according to the SOPD and the RE was recorded. The data were analyzed using t-tests. The TM, RAIU 24h , therapeutic TD, and RE were 36.5±23.9g, 0.54±0.14, 89.4±9.4Gy, and -0.01±0.02, respectively. There was a significant difference (t-value 9.84, P<0.01) between the prescribed and therapeutic TD because the sQMHF ignores the absorbed dose deposited in the thyroid during the first 24h, which is included in the SOPD. In addition, the RE was significantly smaller than the variable coefficient (VC) of the therapeutic TD (t=-39.6, P<0.01). When the activity of 131 I was calculated using the simplified Q-M-H formula, the therapeutic absorbed thyroid dose was significantly higher than what was expected for the prescribed dose. Precision of the individualized therapeutic absorbed dose could be improved by computing the activity of 131 I using the standard operational procedures for dosimetry of the EANM.

Pathogen-Reduced, Plasmalyte-Extended Stored Platelets (PREPS)

DTIC Science & Technology

2013-10-01

if the 1:1:1 strategy is failing, the use of warm FWB is permitted. Such intensive plasma-based therapy early in resuscitation has led to a 50...radiolabeled with 51Cr or 111In. On that day, the subject will return to the Blood Center and provide a 43 mL fresh blood sample. Platelets from...will be infused. The total radiation dose is approximately 40 µCi for a total body absorbed dose of 0.0273 rad (0.273 mSv) and a splenic absorbed

Energy deposition at the bone-tissue interface from nuclear fragments produced by high-energy nucleons

NASA Technical Reports Server (NTRS)

Cucinotta, Francis A.; Hajnal, Ferenc; Wilson, John W.

1990-01-01

The transport of nuclear fragmentation recoils produced by high-energy nucleons in the region of the bone-tissue interface is considered. Results for the different flux and absorbed dose for recoils produced by 1 GeV protons are presented in a bidirectional transport model. The energy deposition in marrow cavities is seen to be enhanced by recoils produced in bone. Approximate analytic formulae for absorbed dose near the interface region are also presented for a simplified range-energy model.

Continuing education: online monitoring of haemodialysis dose.

PubMed

Vartia, Aarne

2018-01-25

Kt/V urea reflects the efficacy of haemodialysis scaled to patient size (urea distribution volume). The guidelines recommend monthly Kt/V measurements based on blood samples. Modern haemodialysis machines are equipped with accessories monitoring the dose online at every session without extra costs, blood samples and computers. To describe the principles, devices, benefits and shortcomings of online monitoring of haemodialysis dose. A critical literature overview and discussion. UV absorbance methods measure Kt/V, ionic dialysance Kt (product of clearance and treatment time; cleared volume without scaling). Both are easy and useful methods, but comparison is difficult due to problems in scaling of the dialysis dose to the patient's size. The best dose estimation method is the one which predicts the quality of life and survival most accurately. There is some evidence on the predictive value of ionic dialysance Kt, but more documentation is required on the UV method. Online monitoring is a useful tool in everyday quality assurance, but blood samples are still required for more accurate kinetic modelling. After reading this article the reader should be able to: Understand the elements of the Kt/V equation for dialysis dose. Compare and contrast different methods of measurement of dialysis dose. Reflect on the importance of adequate dialysis dose for patient survival and life quality. © 2018 European Dialysis and Transplant Nurses Association/European Renal Care Association.

Ascending-dose study of noribogaine in healthy volunteers: pharmacokinetics, pharmacodynamics, safety, and tolerability.

PubMed

Glue, Paul; Lockhart, Michelle; Lam, Fred; Hung, Noelyn; Hung, Cheung-Tak; Friedhoff, Lawrence

2015-02-01

Noribogaine is the active metabolite of the naturally occurring psychoactive substance ibogaine, and may help suppress withdrawal symptoms in opioid-dependent subjects. The objectives of this Phase I study were to assess the safety, tolerability, pharmacokinetic, and pharmacodynamic profiles of noribogaine. In this ascending single-dose, placebo-controlled, randomized, double-blind, parallel-group study in 36 healthy drug-free male volunteers, 4 cohorts (n = 9) received oral doses of 3, 10, 30, or 60 mg or matching placebo, with intensive safety and pharmacokinetic assessments out to 216 hours, along with pharmacodynamic assessments sensitive to the effects of mu-opioid agonists. Noribogaine was rapidly absorbed, with peak concentrations occurring 2-3 hours after oral dosing, and showed dose-linear increases of area under the concentration-time curve (AUC) and Cmax between 3 and 60 mg. The drug was slowly eliminated, with mean half-life estimates of 28-49 hours across dose groups. Apparent volume of distribution was high (mean 1417-3086 L across dose groups). No safety or tolerability issues were identified in any cohort. No mu-opioid agonist pharmacodynamic effects were noted in pupillometry or cold-pressor testing. Single oral doses of noribogaine 3-60 mg were safe and well tolerated in healthy volunteers. © 2014, The American College of Clinical Pharmacology.

Distribution of Absorbed Dose in Cone-Beam Breast Computed Tomography: A Phantom Study With Radiochromic Films

NASA Astrophysics Data System (ADS)

Russo, Paolo; Coppola, Teresa; Mettivier, Giovanni

2010-08-01

Cone-Beam Breast Computed Tomography (CBBCT) of the pendant breast with dedicated scanners is an experimental 3D X-ray imaging technique for breast cancer diagnosis under evaluation in comparison to conventional two-view 2-D mammography of the compressed breast. In CBBCT it is generally assumed that a more uniform distribution of the radiation dose to the breast volume can be obtained, with respect to mammography, at equal Mean Glandular Dose (MGD) levels. In fact, in CBBCT the X-ray beam rotates for 360 deg around the breast, while in each mammography view the breast is irradiated from one side only. Using a CBBCT laboratory scanner developed by our group, we have measured the distribution of the radiation dose in a hemi-ellipsoidal PMMA breast phantom of 14 cm diameter simulating the average uncompressed breast, using radiochromic films type XR-SP inserted at mid-plane in the phantom. The technique factors were 80 kVp (5.6 mm Al Half Value Layer), tube load in the range 23-100 mAs, for an air kerma at isocenter in the range 4.7-20 mGy, for a calculated MGD in the range 3.5-15 mGy for a 14 cm diameter breast of 50% glandularity. Results indicate that the dose decreases from the periphery to the center of the phantom, and that along a transverse profile, the relative dose variation Δ = ((edge-center)/center) is up to (25 ±4)% at a distance of 80 mm from the nipple. As for the relative dose variation along the phantom longitudinal axis, the maximum value at middle of the phantom measured is δ = ((nipple-chest wall)/chest wall) = -(15 ±4)%, indicating that the dose decreases from the chest wall toward the nipple. The values of the parameters Δ and δ depend also on the height of the X-ray tube focal spot with respect to the phantom vertex (nipple). Results are in rough agreement with similar previous determinations using thermoluminescence dosimeters.

Simulation of Earth-Moon-Mars Environments for the Assessment of Organ Doses

NASA Astrophysics Data System (ADS)

Kim, M. Y.; Schwadron, N. A.; Townsend, L.; Cucinotta, F. A.

2010-12-01

Space radiation environments for historically large solar particle events (SPE) and galactic cosmic rays (GCR) at solar minimum and solar maximum are simulated in order to characterize exposures to radio-sensitive organs for missions to low-Earth orbit (LEO), moon, and Mars. Primary and secondary particles for SPE and GCR are transported through the respective atmosphere of Earth or Mars, space vehicle, and astronaut’s body tissues using the HZETRN/QMSFRG computer code. In LEO, exposures are reduced compared to deep space because particles are deflected by the Earth’s magnetic field and absorbed by the solid body of the Earth. Geomagnetic transmission function as a function of altitude was applied for the particle flux of charged particles, and the shift of the organ exposures to higher velocity or lower stopping powers compared to those in deep space was analyzed. In the transport through Mars atmosphere, a vertical distribution of atmospheric thickness was calculated from the temperature and pressure data of Mars Global Surveyor, and the directional cosine distribution was implemented to describe the spherically distributed atmospheric distance along the slant path at each altitude. The resultant directional shielding by Mars atmosphere at solar minimum and solar maximum was used for the particle flux simulation at various altitudes on the Martian surface. Finally, atmospheric shielding was coupled with vehicle and body shielding for organ dose estimates. We made predictions of radiation dose equivalents and evaluated acute symptoms at LEO, moon, and Mars at solar minimum and solar maximum.

Phantom torso experiment on the international space station; flight measurements and calculations

NASA Astrophysics Data System (ADS)

Atwell, W.; Semones, E.; Cucinotta, F.

The Phantom Torso Experiment (PTE) first flew on the 10-day Space Shuttle mission STS-91 in June 1998 during a period near solar minimum. The PTE was re- f l o w n on the I ternational Space Station (ISS) Increment 2 mission from April-n A u g u s t 2001 during a period near solar maximum. The experiment was located with a suite of other radiation experiments in the US Lab module Human Research Facility (HRF) rack. The objective of the experiment was to measure space radiation exposures at several radiosensitive critical body organs (brain, thyroid, heart/lung, stomach and colon) and two locations on the surface (skin) of a modified RandoTM phantom. Prior to flight, active solid -state silicon dosimeters were located at the RandoTM critical body organ locations and passive dosimeters were placed at the two surface locations. Using a mathematically modified Computerized Anatomical Male (CAM) model, shielding distributions were generated for the five critical body organ and two skin locations. These shielding distributions were then combined with the ISS HRF rack shielding distribution to account for the total shielding "seen" by the PTE. Using the trapped proton and galactic cosmic radiation environment models and high -energy particle transport codes, absorbed dose, dose equivalent, and LET (linear energy transfer) values were computed for the seven dose point locations of interest. The results of these computations are compared with the actual flight measurements.

Outdoor solar UVA dose assessment with EBT2 radiochromic film using spectrophotometer and densitometer measurements.

PubMed

Abukassem, I; Bero, M A

2015-04-01

Direct measurements of solar ultraviolet radiations (UVRs) have an important role in the protection of humans against UVR hazard. This work presents simple technique based on the application of EBT2 GAFCHROMIC(®) film for direct solar UVA dose assessment. It demonstrates the effects of different parts of the solar spectrum (UVB, visible and infrared) on performed UVA field measurements and presents the measurement uncertainty budget. The gradient of sunlight exposure level permitted the authors to establish the mathematical relationships between the measured solar UVA dose and two measured quantities: the first was the changes in spectral absorbance at the wavelength 633 nm (A633) and the second was the optical density (OD). The established standard relations were also applied to calculate the solar UVA dose variations during the whole day; 15 min of exposure each hour between 8:00 and 17:00 was recorded. Results show that both applied experimental methods, spectrophotometer absorbance and densitometer OD, deliver comparable figures for EBT2 solar UVA dose assessment with relative uncertainty of 11% for spectral absorbance measurements and 15% for OD measurements. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

An MCNP-based model for the evaluation of the photoneutron dose in high energy medical electron accelerators.

PubMed

Carinou, Eleutheria; Stamatelatos, Ion Evangelos; Kamenopoulou, Vassiliki; Georgolopoulou, Paraskevi; Sandilos, Panayotis

The development of a computational model for the treatment head of a medical electron accelerator (Elekta/Philips SL-18) by the Monte Carlo code mcnp-4C2 is discussed. The model includes the major components of the accelerator head and a pmma phantom representing the patient body. Calculations were performed for a 14 MeV electron beam impinging on the accelerator target and a 10 cmx10 cm beam area at the isocentre. The model was used in order to predict the neutron ambient dose equivalent at the isocentre level and moreover the neutron absorbed dose distribution within the phantom. Calculations were validated against experimental measurements performed by gold foil activation detectors. The results of this study indicated that the equivalent dose at tissues or organs adjacent to the treatment field due to photoneutrons could be up to 10% of the total peripheral dose, for the specific accelerator characteristics examined. Therefore, photoneutrons should be taken into account when accurate dose calculations are required to sensitive tissues that are adjacent to the therapeutic X-ray beam. The method described can be extended to other accelerators and collimation configurations as well, upon specification of treatment head component dimensions, composition and nominal accelerating potential.

The effect of dose enhancement near metal interfaces on synthetic diamond based X-ray dosimeters

NASA Astrophysics Data System (ADS)

Alamoudi, D.; Lohstroh, A.; Albarakaty, H.

2017-11-01

This study investigates the effects of dose enhancement on the photocurrent performance at metallic interfaces in synthetic diamond detectors based X-ray dosimeters as a function of bias voltages. Monte Carlo (MC) simulations with the BEAMnrc code were carried out to simulate the dose enhancement factor (DEF) and compared against the equivalent photocurrent ratio from experimental investigations. The MC simulation results show that the sensitive region for the absorbed dose distribution covers a few micrometers distances from the interface. Experimentally, two single crystals (SC) and one polycrystalline (PC) synthetic diamond samples were fabricated into detectors with carbon based electrodes by boron and carbon ion implantation. Subsequently; the samples were each mounted inside a tissue equivalent encapsulation to minimize unintended fluence perturbation. Dose enhancement was generated by placing copper, lead or gold near the active volume of the detectors using 50 kVp and 100 kVp X-rays relevant for medical dosimetry. The results show enhancement in the detectors' photocurrent performance when different metals are butted up to the diamond bulk as expected. The variation in the photocurrent measurement depends on the type of diamond samples, their electrodes' fabrication and the applied bias voltages indicating that the dose enhancement near the detector may modify their electronic performance.

A comparison of simple and realistic eye models for calculation of fluence to dose conversion coefficients in a broad parallel beam incident of protons

NASA Astrophysics Data System (ADS)

Sakhaee, Mahmoud; Vejdani-Noghreiyan, Alireza; Ebrahimi-Khankook, Atiyeh

2015-01-01

Radiation induced cataract has been demonstrated among people who are exposed to ionizing radiation. To evaluate the deterministic effects of ionizing radiation on the eye lens, several papers dealing with the eye lens dose have been published. ICRP Publication 103 states that the lens of the eye may be more radiosensitive than previously considered. Detailed investigation of the response of the lens showed that there are strong differences in sensitivity to ionizing radiation exposure with respect to cataract induction among the tissues of the lens of the eye. This motivated several groups to look deeper into issue of the dose to a sensitive cell population within the lens, especially for radiations with low energy penetrability that have steep dose gradients inside the lens. Two sophisticated mathematical models of the eye including the inner structure have been designed for the accurate dose estimation in recent years. This study focuses on the calculations of the absorbed doses of different parts of the eye using the stylized models located in UF-ORNL phantom and comparison with the data calculated with the reference computational phantom in a broad parallel beam incident of protons with energies between 20 MeV and 10 GeV. The obtained results indicate that the total lens absorbed doses of reference phantom has good compliance with those of the more sensitive regions of stylized models. However, total eye absorbed dose of these models greatly differ with each other for lower energies.