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.

SU-F-19A-02: Comparison of Absorbed Dose to Water Standards for HDR Ir-192 Brachytherapy Between the LCR, Brazil and NRC, Canada

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

Salata, C; David, M; Almeida, C de

2014-06-15

Purpose: To compare absorbed dose to water standards for HDR brachytherapy dosimetry developed by the Radiological Science Laboratory of Rio de Janeiro State University (LCR) and the National Research Council, Canada (NRC). Methods: The two institutions have separately developed absorbed dose standards based on the Fricke dosimetry system. There are important differences between the two standards, including: preparation and read-out of the Fricke solution, irradiation geometry of the Fricke holder in relation to the Ir-192 source, and determination of the G-value to be used at Ir-192 energies. All measurements for both standards were made directly at the NRC laboratory (i.e.,more » no transfer instrument was used) using a single Ir-192 source (microSelectron v2). In addition, the NRC group has established a self-consistent method to determine the G-value for Ir-192, based on an interpolation between G-values obtained at Co-60 and 250kVp X-rays, and this measurement was repeated using the LCR Fricke solution to investigate possible systematic uncertainties. Results: G-values for Co-60 and 250 kVp x-rays, obtained using the LCR Fricke system, agreed with the NRC values within 0.5 % and 1 % respectively, indicating that the general assumption of universal G-values is appropriate in this case. The standard uncertainty in the determination of G for Ir-192 is estimated to be 0.6 %. For the comparison of absorbed dose measurements at the reference point for Ir-192 (1 cm depth in water, perpendicular to the seed long-axis), the ratio Dw(NRC)/Dw(LCR) was found to be 1.011 with a combined standard uncertainty of 1.7 %, k=1. Conclusion: The agreement in the absorbed dose to water values for the LCR and NRC systems is very encouraging. Combined with the lower uncertainty in this approach compared to the present air-kerma approach, these results reaffirm the use of Fricke solution as a potential primary standard for HDR Ir-192 brachytherapy.« 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.

A small-scale anatomical dosimetry model of the liver

NASA Astrophysics Data System (ADS)

Stenvall, Anna; Larsson, Erik; Strand, Sven-Erik; Jönsson, Bo-Anders

2014-07-01

Radionuclide therapy is a growing and promising approach for treating and prolonging the lives of patients with cancer. For therapies where high activities are administered, the liver can become a dose-limiting organ; often with a complex, non-uniform activity distribution and resulting non-uniform absorbed-dose distribution. This paper therefore presents a small-scale dosimetry model for various source-target combinations within the human liver microarchitecture. Using Monte Carlo simulations, Medical Internal Radiation Dose formalism-compatible specific absorbed fractions were calculated for monoenergetic electrons; photons; alpha particles; and 125I, 90Y, 211At, 99mTc, 111In, 177Lu, 131I and 18F. S values and the ratio of local absorbed dose to the whole-organ average absorbed dose was calculated, enabling a transformation of dosimetry calculations from macro- to microstructure level. For heterogeneous activity distributions, for example uptake in Kupffer cells of radionuclides emitting low-energy electrons (125I) or high-LET alpha particles (211At) the target absorbed dose for the part of the space of Disse, closest to the source, was more than eight- and five-fold the average absorbed dose to the liver, respectively. With the increasing interest in radionuclide therapy of the liver, the presented model is an applicable tool for small-scale liver dosimetry in order to study detailed dose-effect relationships in the liver.

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.

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 +

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.

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.

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

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.

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

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

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 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.

Strengths and Weaknesses of a Planar Whole-Body Method of 153Sm Dosimetry for Patients with Metastatic Osteosarcoma and Comparison with Three-Dimensional Dosimetry

PubMed Central

Plyku, Donika; Loeb, David M.; Prideaux, Andrew R.; Baechler, Sébastien; Wahl, Richard L.; Sgouros, George

2015-01-01

Abstract Purpose: Dosimetric accuracy depends directly upon the accuracy of the activity measurements in tumors and organs. The authors present the methods and results of a retrospective tumor dosimetry analysis in 14 patients with a total of 28 tumors treated with high activities of 153Sm-ethylenediaminetetramethylenephosphonate (153Sm-EDTMP) for therapy of metastatic osteosarcoma using planar images and compare the results with three-dimensional dosimetry. Materials and Methods: Analysis of phantom data provided a complete set of parameters for dosimetric calculations, including buildup factor, attenuation coefficient, and camera dead-time compensation. The latter was obtained using a previously developed methodology that accounts for the relative motion of the camera and patient during whole-body (WB) imaging. Tumor activity values calculated from the anterior and posterior views of WB planar images of patients treated with 153Sm-EDTMP for pediatric osteosarcoma were compared with the geometric mean value. The mean activities were integrated over time and tumor-absorbed doses were calculated using the software package OLINDA/EXM. Results: The authors found that it was necessary to employ the dead-time correction algorithm to prevent measured tumor activity half-lives from often exceeding the physical decay half-life of 153Sm. Measured half-lives so long are unquestionably in error. Tumor-absorbed doses varied between 0.0022 and 0.27 cGy/MBq with an average of 0.065 cGy/MBq; however, a comparison with absorbed dose values derived from a three-dimensional analysis for the same tumors showed no correlation; moreover, the ratio of three-dimensional absorbed dose value to planar absorbed dose value was 2.19. From the anterior and posterior activity comparisons, the order of clinical uncertainty for activity and dose calculations from WB planar images, with the present methodology, is hypothesized to be about 70%. Conclusion: The dosimetric results from clinical patient data indicate that absolute planar dosimetry is unreliable and dosimetry using three-dimensional imaging is preferable, particularly for tumors, except perhaps for the most sophisticated planar methods. The relative activity and patient kinetics derived from planar imaging show a greater level of reliability than the dosimetry. PMID:26560193

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

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.

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.;

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.

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.

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

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.

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

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

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.

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

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

Effect of improved TLD dosimetry on the determination of dose rate constants for {sup 125}I and {sup 103}Pd brachytherapy seeds

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

Rodriguez, M., E-mail: manuel.rodriguez@rmp.uhn.ca; Rogers, D. W. O.

Purpose: To more accurately account for the relative intrinsic energy dependence and relative absorbed-dose energy dependence of TLDs when used to measure dose rate constants (DRCs) for {sup 125}I and {sup 103}Pd brachytherapy seeds, to thereby establish revised “measured values” for all seeds and compare the revised values with Monte Carlo and consensus values. Methods: The relative absorbed-dose energy dependence, f{sup rel}, for TLDs and the phantom correction, P{sub phant}, are calculated for {sup 125}I and {sup 103}Pd seeds using the EGSnrc BrachyDose and DOSXYZnrc codes. The original energy dependence and phantom corrections applied to DRC measurements are replaced bymore » calculated (f{sup rel}){sup −1} and P{sub phant} values for 24 different seed models. By comparing the modified measured DRCs to the MC values, an appropriate relative intrinsic energy dependence, k{sub bq}{sup rel}, is determined. The new P{sub phant} values and relative absorbed-dose sensitivities, S{sub AD}{sup rel}, calculated as the product of (f{sup rel}){sup −1} and (k{sub bq}{sup rel}){sup −1}, are used to individually revise the measured DRCs for comparison with Monte Carlo calculated values and TG-43U1 or TG-43U1S1 consensus values. Results: In general, f{sup rel} is sensitive to the energy spectra and models of the brachytherapy seeds. Values may vary up to 8.4% among {sup 125}I and {sup 103}Pd seed models and common TLD shapes. P{sub phant} values depend primarily on the isotope used. Deduced (k{sub bq}{sup rel}){sup −1} values are 1.074 ± 0.015 and 1.084 ± 0.026 for {sup 125}I and {sup 103}Pd seeds, respectively. For (1 mm){sup 3} chips, this implies an overall absorbed-dose sensitivity relative to {sup 60}Co or 6 MV calibrations of 1.51 ± 1% and 1.47 ± 2% for {sup 125}I and {sup 103}Pd seeds, respectively, as opposed to the widely used value of 1.41. Values of P{sub phant} calculated here have much lower statistical uncertainties than literature values, but systematic uncertainties from density and composition uncertainties are significant. Using these revised values with the literature’s DRC measurements, the average discrepancies between revised measured values and Monte Carlo values are 1.2% and 0.2% for {sup 125}I and {sup 103}Pd seeds, respectively, compared to average discrepancies for the original measured values of 4.8%. On average, the revised measured values are 4.3% and 5.9% lower than the original measured values for {sup 103}Pd and {sup 125}I seeds, respectively. The average of revised DRCs and Monte Carlo values is 3.8% and 2.8% lower for {sup 125}I and {sup 103}Pd seeds, respectively, than the consensus values in TG-43U1 or TG-43U1S1. Conclusions: This work shows that f{sup rel} is TLD shape and seed model dependent suggesting a need to update the generalized energy response dependence, i.e., relative absorbed-dose sensitivity, measured 25 years ago and applied often to DRC measurements of {sup 125}I and {sup 103}Pd brachytherapy seeds. The intrinsic energy dependence for LiF TLDs deduced here is consistent with previous dosimetry studies and emphasizes the need to revise the DRC consensus values reported by TG-43U1 or TG-43U1S1.« less

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.

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.

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.

High resolution digital autoradiographic and dosimetric analysis of heterogeneous radioactivity distribution in xenografted prostate tumors.

PubMed

Timmermand, Oskar V; Nilsson, Jenny; Strand, Sven-Erik; Elgqvist, Jörgen

2016-12-01

The first main aim of this study was to illustrate the absorbed dose rate distribution from 177 Lu in sections of xenografted prostate cancer (PCa) tumors using high resolution digital autoradiography (DAR) and compare it with hypothetical identical radioactivity distributions of 90 Y or 7 MeV alpha-particles. Three dosimetry models based on either dose point kernels or Monte Carlo simulations were used and evaluated. The second and overlapping aim, was to perform DAR imaging and dosimetric analysis of the distribution of radioactivity, and hence the absorbed dose rate, in tumor sections at an early time point after injection during radioimmunotherapy using 177 Lu-h11B6, directed against the human kallikrein 2 antigen. Male immunodeficient BALB/c nude mice, aged 6-8 w, were inoculated by subcutaneous injection of ∼10 7 LNCaP cells in a 200 μl suspension of a 1:1 mixture of medium and Matrigel. The antibody h11B6 was conjugated with the chelator CHX-A″-DTPA after which conjugated h11B6 was mixed with 177 LuCl 3 . The incubation was performed at room temperature for 2 h, after which the labeling was terminated and the solution was purified on a NAP-5 column. About 20 MBq 177 Lu-h11B6 was injected intravenously in the tail vein. At approximately 10 h postinjection (hpi), the mice were sacrificed and one tumor was collected from each of the five animals and cryosectioned into 10 μm thick slices. The tumor slices were measured and imaged using the DAR MicroImager system and the M3Vision software. Then the absorbed dose rate was calculated using a dose point kernel generated with the Monte Carlo code gate v7.0. The DAR system produced high resolution images of the radioactivity distribution, close to the resolution of single PCa cells. The DAR images revealed a pronounced heterogeneous radioactivity distribution, i.e., count rate per area, in the tumors, indicated by the normalized intensity variations along cross sections as mean ± SD: 0.15 ± 0.15, 0.20 ± 0.18, 0.12 ± 0.17, 0.15 ± 0.16, and 0.23 ± 0.22, for each tumor section, respectively. The absorbed dose rate distribution for 177 Lu at the time of dissection 10 hpi showed a maximum value of 2.9 ± 0.4 Gy/h (mean ± SD), compared to 6.0 ± 0.9 and 159 ± 25 Gy/h for the hypothetical 90 Y and 7 MeV alpha-particle cases assuming the same count rate densities. Mean absorbed dose rate values were 0.13, 0.53, and 6.43 Gy/h for 177 Lu, 90 Y, and alpha-particles, respectively. The initial uptake of 177 Lu-h11B6 produces a high absorbed dose rate, which is important for a successful therapeutic outcome. The hypothetical 90 Y case indicates a less heterogeneous absorbed dose rate distribution and a higher mean absorbed dose rate compared to 177 Lu, although with a potentially increased irradiation of surrounding healthy tissue. The hypothetical alpha-particle case indicates the possibility of a higher maximum absorbed dose rate, although with a more heterogeneous absorbed dose rate distribution.

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.

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.

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.

Internal photon and electron dosimetry of the newborn patient—a hybrid computational phantom study

NASA Astrophysics Data System (ADS)

Wayson, Michael; Lee, Choonsik; Sgouros, George; Treves, S. Ted; Frey, Eric; Bolch, Wesley E.

2012-03-01

Estimates of radiation absorbed dose to organs of the nuclear medicine patient are a requirement for administered activity optimization and for stochastic risk assessment. Pediatric patients, and in particular the newborn child, represent that portion of the patient population where such optimization studies are most crucial owing to the enhanced tissue radiosensitivities and longer life expectancies of this patient subpopulation. In cases where whole-body CT imaging is not available, phantom-based calculations of radionuclide S values—absorbed dose to a target tissue per nuclear transformation in a source tissue—are required for dose and risk evaluation. In this study, a comprehensive model of electron and photon dosimetry of the reference newborn child is presented based on a high-resolution hybrid-voxel phantom from the University of Florida (UF) patient model series. Values of photon specific absorbed fraction (SAF) were assembled for both the reference male and female newborn using the radiation transport code MCNPX v2.6. Values of electron SAF were assembled in a unique and time-efficient manner whereby the collisional and radiative components of organ dose--for both self- and cross-dose terms—were computed separately. Dose to the newborn skeletal tissues were assessed via fluence-to-dose response functions reported for the first time in this study. Values of photon and electron SAFs were used to assemble a complete set of S values for some 16 radionuclides commonly associated with molecular imaging of the newborn. These values were then compared to those available in the OLINDA/EXM software. S value ratios for organ self-dose ranged from 0.46 to 1.42, while similar ratios for organ cross-dose varied from a low of 0.04 to a high of 3.49. These large discrepancies are due in large part to the simplistic organ modeling in the stylized newborn model used in the OLINDA/EXM software. A comprehensive model of internal dosimetry is presented in this study for the newborn nuclear medicine patient based upon the UF hybrid computational phantom. Photon dose response functions, photon and electron SAFs, and tables of radionuclide S values for the newborn child--both male and female--are given in a series of four electronic annexes available at stacks.iop.org/pmb/57/1433/mmedia. These values can be applied to optimization studies of image quality and stochastic risk for this most vulnerable class of pediatric patients.

ESR spectroscopy for detecting gamma-irradiated dried vegetables and estimating absorbed doses

NASA Astrophysics Data System (ADS)

Kwon, Joong-Ho; Chung, Hyung-Wook; Byun, Myung-Woo

2000-03-01

In view of an increasing demand for food irradiation technology, the development of a reliable means of detection for the control of irradiated foods has become necessary. Various vegetable food materials (dried cabbage, carrot, chunggyungchae, garlic, onion, and green onion), which can be legally irradiated in Korea, were subjected to a detection study using ESR spectroscopy. Correlation coefficients ( R2) between absorbed doses (2.5-15 kGy) and their corresponding ESR signals were identified from ESR signals. Pre-established threshold values were successfully applied to the detection of 54 coded unknown samples of dried clean vegetables ( chunggyungchae, Brassica camestris var. chinensis), both non-irradiated and irradiated. The ESR signals of irradiated chunggyungchae decreased over a longer storage time, however, even after 6 months of ambient storage, these signals were still distinguishable from those of non-irradiated samples. The most successful estimates of absorbed dose (5 and 8 kGy) were obtained immediately after irradiation using a quadratic fit with average values of 4.85 and 8.65 kGy being calculated.

Angular distributions of absorbed dose of Bremsstrahlung and secondary electrons induced by 18-, 28- and 38-MeV electron beams in thick targets.

PubMed

Takada, Masashi; Kosako, Kazuaki; Oishi, Koji; Nakamura, Takashi; Sato, Kouichi; Kamiyama, Takashi; Kiyanagi, Yoshiaki

2013-03-01

Angular distributions of absorbed dose of Bremsstrahlung photons and secondary electrons at a wide range of emission angles from 0 to 135°, were experimentally obtained using an ion chamber with a 0.6 cm(3) air volume covered with or without a build-up cap. The Bremsstrahlung photons and electrons were produced by 18-, 28- and 38-MeV electron beams bombarding tungsten, copper, aluminium and carbon targets. The absorbed doses were also calculated from simulated photon and electron energy spectra by multiplying simulated response functions of the ion chambers, simulated with the MCNPX code. Calculated-to-experimental (C/E) dose ratios obtained are from 0.70 to 1.57 for high-Z targets of W and Cu, from 15 to 135° and the C/E range from 0.6 to 1.4 at 0°; however, the values of C/E for low-Z targets of Al and C are from 0.5 to 1.8 from 0 to 135°. Angular distributions at the forward angles decrease with increasing angles; on the other hand, the angular distributions at the backward angles depend on the target species. The dependences of absorbed doses on electron energy and target thickness were compared between the measured and simulated results. The attenuation profiles of absorbed doses of Bremsstrahlung beams at 0, 30 and 135° were also measured.

Evaluation of the peripheral dose to uterus in breast carcinoma radiotherapy.

PubMed

Martín Rincón, C; Jerez Sainz, I; Modolell Farré, I; España López, M L; López Franco, P; Muñiz, J L; Romero, A M; Rodríguez, R

2002-01-01

The absorbed dose outside of the direct fields of radiotherapy treatment (or peripheral dose, PD) is responsible for radiation exposure of the fetus in pregnant women. Because the radiological protection of the unborn child is of particular concern in the early period of the pregnancy, the aim of this study is to estimate the PD in order to assess the absorbed dose in the uterus in a pregnant patient irradiated for breast carcinoma therapy. The treatment was simulated on an Alderson-Rando anthropomorphic phantom, and the radiation dose to the fetus was measured using an ionisation chamber and thermoluminescence dosemeters. Two similar treatments plans with and without wedges were delivered, using a 6 MV photon beam with two isocentric opposite tangential fields with a total dose of 50 Gy, in accordance with common established procedures. Average field parameters for more than 300 patients were studied. Measurements showed the fetal dose to be slightly lower than 50 mGy, a level at which the risk to the fetus is uncertain, although several authors consider this value as the dose threshold for deterministic effects. The planning system (PS) underestimated PD values and no significant influence was found with the use of wedge filters.

TU-H-CAMPUS-IeP1-05: A Framework for the Analytic Calculation of Patient-Specific Dose Distribution Due to CBCT Scan for IGRT

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

Youn, H; Jeon, H; Nam, J

Purpose: To investigate the feasibility of an analytic framework to estimate patients’ absorbed dose distribution owing to daily cone-beam CT scan for image-guided radiation treatment. Methods: To compute total absorbed dose distribution, we separated the framework into primary and scattered dose calculations. Using the source parameters such as voltage, current, and bowtie filtration, for the primary dose calculation, we simulated the forward projection from the source to each voxel of an imaging object including some inhomogeneous inserts. Then we calculated the primary absorbed dose at each voxel based on the absorption probability deduced from the HU values and Beer’s law.more » In sequence, all voxels constructing the phantom were regarded as secondary sources to radiate scattered photons for scattered dose calculation. Details of forward projection were identical to that of the previous step. The secondary source intensities were given by using scatter-to- primary ratios provided by NIST. In addition, we compared the analytically calculated dose distribution with their Monte Carlo simulation results. Results: The suggested framework for absorbed dose estimation successfully provided the primary and secondary dose distributions of the phantom. Moreover, our analytic dose calculations and Monte Carlo calculations were well agreed each other even near the inhomogeneous inserts. Conclusion: This work indicated that our framework can be an effective monitor to estimate a patient’s exposure owing to cone-beam CT scan for image-guided radiation treatment. Therefore, we expected that the patient’s over-exposure during IGRT might be prevented by our framework.« less

[An investigation of ionizing radiation dose in a manufacturing enterprise of ion-absorbing type rare earth ore].

PubMed

Zhang, W F; Tang, S H; Tan, Q; Liu, Y M

2016-08-20

Objective: To investigate radioactive source term dose monitoring and estimation results in a manufacturing enterprise of ion-absorbing type rare earth ore and the possible ionizing radiation dose received by its workers. Methods: Ionizing radiation monitoring data of the posts in the control area and supervised area of workplace were collected, and the annual average effective dose directly estimated or estimated using formulas was evaluated and analyzed. Results: In the control area and supervised area of the workplace for this rare earth ore, α surface contamination activity had a maximum value of 0.35 Bq/cm 2 and a minimum value of 0.01 Bq/cm 2 ; β radioactive surface contamination activity had a maximum value of 18.8 Bq/cm 2 and a minimum value of 0.22 Bq/cm 2 . In 14 monitoring points in the workplace, the maximum value of the annual average effective dose of occupational exposure was 1.641 mSv/a, which did not exceed the authorized limit for workers (5 mSv/a) , but exceeded the authorized limit for general personnel (0.25 mSv/a) . The radionuclide specific activity of ionic mixed rare earth oxides was determined to be 0.9. Conclusion: The annual average effective dose of occupational exposure in this enterprise does not exceed the authorized limit for workers, but it exceeds the authorized limit for general personnel. We should pay attention to the focus of the radiation process, especially for public works radiation.

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

Early Dose Response to Yttrium-90 Microsphere Treatment of Metastatic Liver Cancer by a Patient-Specific Method Using Single Photon Emission Computed Tomography and Positron Emission Tomography

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

Campbell, Janice M.; Department of Radiation Oncology, Wayne State University, Detroit, MI; Wong, C. Oliver

2009-05-01

Purpose: To evaluate a patient-specific single photon emission computed tomography (SPECT)-based method of dose calculation for treatment planning of yttrium-90 ({sup 90}Y) microsphere selective internal radiotherapy (SIRT). Methods and Materials: Fourteen consecutive {sup 90}Y SIRTs for colorectal liver metastasis were retrospectively analyzed. Absorbed dose to tumor and normal liver tissue was calculated by partition methods with two different tumor/normal liver vascularity ratios: an average 3:1 and a patient-specific ratio derived from pretreatment technetium-99m macroaggregated albumin SPECT. Tumor response was quantitatively evaluated from fluorine-18 fluoro-2-deoxy-D-glucose positron emission tomography scans. Results: Positron emission tomography showed a significant decrease in total tumor standardizedmore » uptake value (average, 52%). There was a significant difference in the tumor absorbed dose between the average and specific methods (p = 0.009). Response vs. dose curves fit by linear and linear-quadratic modeling showed similar results. Linear fit r values increased for all tumor response parameters with the specific method (+0.20 for mean standardized uptake value). Conclusion: Tumor dose calculated with the patient-specific method was more predictive of response in liver-directed {sup 90}Y SIRT.« less

Assessment of natural radionuclides and its radiological hazards from tiles made in Nigeria

NASA Astrophysics Data System (ADS)

Joel, E. S.; Maxwell, O.; Adewoyin, O. O.; Ehi-Eromosele, C. O.; Embong, Z.; Saeed, M. A.

2018-03-01

Activity concentration of 10 different brands of tiles made in Nigeria were analyzed using High purity Germanium gamma detector and its hazard indices such as absorbed dose rate, radium equivalent activity, external Hazard Index (Hex), internal Hazard Index (Hin), Annual Effective Dose (mSv/y), Gamma activity Index (Iγ) and Alpha Index (Iα) were determined. The result showed that the average activity concentrations of radionuclides (226Ra, 232Th and 40K) content are within the recommended limit. The average radium equivalent is within the recommended limit of 370 Bq/kg. The result obtained further showed that the mean values for the absorbed dose rate (D), external and internal hazard index, the annual effective dose (AEDR) equivalent, gamma activity index and Alpha Index were: 169.22 nGyh-1, 0.95 and 1.14, 1.59 mSv/y, 1.00 Sv yr-1 and 0.34 respectively. The result established that radiological hazards such as absorbed dose rate, internal hazard, annual effective dose rate, gamma activity index and Alpha Index for some samples are found to be slightly close or above international recommended values. The result for the present study was compared with tiles sample from others countries, it was observed that the concentration of tiles made in Nigeria and other countries are closer, however recommends proper radiation monitoring for some tiles made in Nigeria before usage due to the long term health effect.

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

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

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.

Redefining relative biological effectiveness in the context of the EQDX formalism: implications for alpha-particle emitter therapy.

PubMed

Hobbs, Robert F; Howell, Roger W; Song, Hong; Baechler, Sébastien; Sgouros, George

2014-01-01

Alpha-particle radiopharmaceutical therapy (αRPT) is currently enjoying increasing attention as a viable alternative to chemotherapy for targeting of disseminated micrometastatic disease. In theory, αRPT can be personalized through pre-therapeutic imaging and dosimetry. However, in practice, given the particularities of α-particle emissions, a dosimetric methodology that accurately predicts the thresholds for organ toxicity has not been reported. This is in part due to the fact that the biological effects caused by α-particle radiation differ markedly from the effects caused by traditional external beam (photon or electron) radiation or β-particle emitting radiopharmaceuticals. The concept of relative biological effectiveness (RBE) is used to quantify the ratio of absorbed doses required to achieve a given biological response with alpha particles versus a reference radiation (typically a beta emitter or external beam radiation). However, as conventionally defined, the RBE varies as a function of absorbed dose and therefore a single RBE value is limited in its utility because it cannot be used to predict response over a wide range of absorbed doses. Therefore, efforts are underway to standardize bioeffect modeling for different fractionation schemes and dose rates for both nuclear medicine and external beam radiotherapy. Given the preponderant use of external beams of radiation compared to nuclear medicine in cancer therapy, the more clinically relevant quantity, the 2 Gy equieffective dose, EQD2(α/β), has recently been proposed by the ICRU. In concert with EQD2(α/β), we introduce a new, redefined RBE quantity, named RBE2(α/β), as the ratio of the two linear coefficients that characterize the α particle absorbed dose-response curve and the low-LET megavoltage photon 2 Gy fraction equieffective dose-response curve. The theoretical framework for the proposed new formalism is presented along with its application to experimental data obtained from irradiation of a breast cancer cell line. Radiobiological parameters are obtained using the linear quadratic model to fit cell survival data for MDA-MB-231 human breast cancer cells that were irradiated with either α particles or a single fraction of low-LET (137)Cs γ rays. From these, the linear coefficient for both the biologically effective dose (BED) and the EQD2(α/β) response lines were derived for fractionated irradiation. The standard RBE calculation, using the traditional single fraction reference radiation, gave RBE values that ranged from 2.4 for a surviving fraction of 0.82-6.0 for a surviving fraction of 0.02, while the dose-independent RBE2(4.6) value was 4.5 for all surviving fraction values. Furthermore, bioeffect modeling with RBE2(α/β) and EQD2(α/β) demonstrated the capacity to predict the surviving fraction of cells irradiated with acute and fractionated low-LET radiation, α particles and chronic exponentially decreasing dose rates of low-LET radiation. RBE2(α/β) is independent of absorbed dose for α-particle emitters and it provides a more logical framework for data reporting and conversion to equieffective dose than the conventional dose-dependent definition of RBE. Moreover, it provides a much needed foundation for the ongoing development of an α-particle dosimetry paradigm and will facilitate the use of tolerance dose data available from external beam radiation therapy, thereby helping to develop αRPT as a single modality as well as for combination therapies.

Redefining Relative Biological Effectiveness in the Context of the EQDX Formalism: Implications for Alpha-Particle Emitter Therapy.

PubMed

Hobbs, Robert F; Howell, Roger W; Song, Hong; Baechler, Sébastien; Sgouros, George

2013-12-30

Alpha-particle radiopharmaceutical therapy (αRPT) is currently enjoying increasing attention as a viable alternative to chemotherapy for targeting of disseminated micrometastatic disease. In theory, αRPT can be personalized through pre-therapeutic imaging and dosimetry. However, in practice, given the particularities of α-particle emissions, a dosimetric methodology that accurately predicts the thresholds for organ toxicity has not been reported. This is in part due to the fact that the biological effects caused by α-particle radiation differ markedly from the effects caused by traditional external beam (photon or electron) radiation or β-particle emitting radiopharmaceuticals. The concept of relative biological effectiveness (RBE) is used to quantify the ratio of absorbed doses required to achieve a given biological response with alpha particles versus a reference radiation (typically a beta emitter or external beam radiation). However, as conventionally defined, the RBE varies as a function of absorbed dose and therefore a single RBE value is limited in its utility because it cannot be used to predict response over a wide range of absorbed doses. Therefore, efforts are underway to standardize bioeffect modeling for different fractionation schemes and dose rates for both nuclear medicine and external beam radiotherapy. Given the preponderant use of external beams of radiation compared to nuclear medicine in cancer therapy, the more clinically relevant quantity, the 2 Gy equieffective dose, EQD2(α/β), has recently been proposed by the ICRU. In concert with EQD2(α/β), we introduce a new, redefined RBE quantity, named RBE2(α/β), as the ratio of the two linear coefficients that characterize the α particle absorbed dose-response curve and the low-LET megavoltage photon 2 Gy fraction equieffective dose-response curve. The theoretical framework for the proposed new formalism is presented along with its application to experimental data obtained from irradiation of a breast cancer cell line. Radiobiological parameters are obtained using the linear quadratic model to fit cell survival data for MDA-MB-231 human breast cancer cells that were irradiated with either α particles or a single fraction of low-LET 137 Cs γ rays. From these, the linear coefficient for both the biologically effective dose (BED) and the EQD2(α/β) response lines were derived for fractionated irradiation. The standard RBE calculation, using the traditional single fraction reference radiation, gave RBE values that ranged from 2.4 for a surviving fraction of 0.82-6.0 for a surviving fraction of 0.02, while the dose-independent RBE2(4.6) value was 4.5 for all surviving fraction values. Furthermore, bioeffect modeling with RBE2(α/β) and EQD2(α/β) demonstrated the capacity to predict the surviving fraction of cells irradiated with acute and fractionated low-LET radiation, α particles and chronic exponentially decreasing dose rates of low-LET radiation. RBE2(α/β) is independent of absorbed dose for α-particle emitters and it provides a more logical framework for data reporting and conversion to equieffective dose than the conventional dose-dependent definition of RBE. Moreover, it provides a much needed foundation for the ongoing development of an α-particle dosimetry paradigm and will facilitate the use of tolerance dose data available from external beam radiation therapy, thereby helping to develop αRPT as a single modality as well as for combination therapies.

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

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.

Dosimetric study of mandible examinations performed with three cone-beam computed tomography scanners.

PubMed

Khoury, Helen J; Andrade, Marcos E; Araujo, Max Well; Brasileiro, Izabela V; Kramer, Richard; Huda, Amir

2015-07-01

The objective of this work was to evaluate the air kerma-area product (PKA) and the skin absorbed dose in the region of the eyes, salivary glands and thyroid of the patient from mandible examinations performed with three cone-beam computed tomography (CBCT) scanners, i.e. i-CAT classic, Gendex CB-500 and PreXion 3D. For the dosimetric evaluation, an anthropomorphic head phantom (model RS-250) was used to simulate an adult patient. The CBCT examinations were performed using standard and high-resolution protocols for mandible acquisitions for adult patients. During the phantom's exposure, the PKA was measured using an ionising chamber and the absorbed doses to the skin in the region of the eyes, thyroid and salivary glands were estimated using thermoluminescence dosemeters (TLDs) positioned on the phantom's surface. The PKA values estimated with the CBCT scanners varied from 26 to 138 µGy m(2). Skin absorbed doses in the region of the eyes varied from 0.07 to 0.34 mGy; at the parotid glands, from 1.31 to 5.93 mGy; at the submandibular glands, from 1.41 to 6.86 mGy; and at the thyroid, from 0.18 to 2.45 mGy. PKA and absorbed doses showed the highest values for the PreXion 3D scanner due to the use of the continuous exposure mode and a high current-time product. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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).

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.

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

Monte Carlo estimation of radiation dose in organs of female and male adult phantoms due to FDG-F18 absorbed in the lungs

NASA Astrophysics Data System (ADS)

Belinato, Walmir; Santos, William S.; Silva, Rogério M. V.; Souza, Divanizia N.

2014-03-01

The determination of dose conversion factors (S values) for the radionuclide fluorodeoxyglucose (18F-FDG) absorbed in the lungs during a positron emission tomography (PET) procedure was calculated using the Monte Carlo method (MCNPX version 2.7.0). For the obtained dose conversion factors of interest, it was considered a uniform absorption of radiopharmaceutical by the lung of a healthy adult human. The spectrum of fluorine was introduced in the input data file for the simulation. The simulation took place in two adult phantoms of both sexes, based on polygon mesh surfaces called FASH and MASH with anatomy and posture according to ICRP 89. The S values for the 22 internal organs/tissues, chosen from ICRP No. 110, for the FASH and MASH phantoms were compared with the results obtained from a MIRD V phantoms called ADAM and EVA used by the Committee on Medical Internal Radiation Dose (MIRD). We observed variation of more than 100% in S values due to structural anatomical differences in the internal organs of the MASH and FASH phantoms compared to the mathematical phantom.

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

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

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.

Impact of missing attenuation and scatter corrections on 99m Tc-MAA SPECT 3D dosimetry for liver radioembolization using the patient relative calibration methodology: A retrospective investigation on clinical images.

PubMed

Botta, Francesca; Ferrari, Mahila; Chiesa, Carlo; Vitali, Sara; Guerriero, Francesco; Nile, Maria Chiara De; Mira, Marta; Lorenzon, Leda; Pacilio, Massimiliano; Cremonesi, Marta

2018-04-01

To investigate the clinical implication of performing pre-treatment dosimetry for 90 Y-microspheres liver radioembolization on 99m Tc-MAA SPECT images reconstructed without attenuation or scatter correction and quantified with the patient relative calibration methodology. Twenty-five patients treated with SIR-Spheres ® at Istituto Europeo di Oncologia and 31 patients treated with TheraSphere ® at Istituto Nazionale Tumori were considered. For each acquired 99m Tc-MAA SPECT, four reconstructions were performed: with attenuation and scatter correction (AC_SC), only attenuation (AC_NoSC), only scatter (NoAC_SC) and without corrections (NoAC_NoSC). Absorbed dose maps were calculated from the activity maps, quantified applying the patient relative calibration to the SPECT images. Whole Liver (WL) and Tumor (T) regions were drawn on CT images. Injected Liver (IL) region was defined including the voxels receiving absorbed dose >3.8 Gy/GBq. Whole Healthy Liver (WHL) and Healthy Injected Liver (HIL) regions were obtained as WHL = WL - T and HIL = IL - T. Average absorbed dose to WHL and HIL were calculated, and the injection activity was derived following each Institute's procedure. The values obtained from AC_NoSC, NoAC_SC and NoAC_NoSC images were compared to the reference value suggested by AC_SC images using Bland-Altman analysis and Wilcoxon paired test (5% significance threshold). Absorbed-dose maps were compared to the reference map (AC_SC) in global terms using the Voxel Normalized Mean Square Error (%VNMSE), and at voxel level by calculating for each voxel the normalized difference with the reference value. The uncertainty affecting absorbed dose at voxel level was accounted for in the comparison; to this purpose, the voxel counts fluctuation due to Poisson and reconstruction noise was estimated from SPECT images of a water phantom acquired and reconstructed as patient images. NoAC_SC images lead to activity prescriptions not significantly different from the reference AC_SC images; the individual differences (<0.1 GBq for all IEO patients, <0.6 GBq for all but one INT patients) were comparable to the uncertainty affecting activity measurement. AC_NoSC and NoAC_NoSC images, instead, yielded significantly different activity prescriptions and wider 95% confidence intervals in the Bland-Altman analysis. Concerning the absorbed dose map, AC_NoSC images had the smallest %VNMSE value and the highest fraction of voxels differing less than 2 standard deviations from AC_SC. The patient relative calibration methodology can compensate for the missing attenuation correction when performing healthy liver pre-treatment dosimetry: safe treatments can be planned even on NoAC_SC images, suggesting activities comparable to AC_SC images. Scatter correction is recommended due to its heavy impact on healthy liver dosimetry. © 2018 American Association of Physicists in Medicine.

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.

Validation of a Prototype Optical Computed Tomography System

PubMed Central

Zakariaee, Seyed Salman; Molazadeh, Mikaeil; Takavar, Abbas; Shirazi, Alireza; Mesbahi, Asghar; Zeinali, Ahad

2015-01-01

In radiation cancer treatments, the most of the side effects could be minimized using a proper dosimeter. Gel dosimeter is the only three-dimensional dosimeter and magnetic resonance imaging (MRI) is the gold standard method for gel dosimeter readout. Because of hard accessibility and high cost of sample reading by MRI systems, some other alternative methods were developed. The optical computed tomography (OCT) method could be considered as the most promising alternative method that has been studied widely. In the current study, gel dosimeter scanning using a prototype optical scanner and validation of this optical scanner was performed. Optical absorbance of the irradiated gel samples was determined by both of conventional spectrophotometer and the fabricated OCT system at 632 nm. Furthermore, these irradiated vials were scanned by a 1.5 T MRI. The slope of the curves was extracted as the dose-response sensitivity. The R2-dose sensitivity measured by MRI method was 0.1904 and 0.113 for NIPAM and PAGAT gels, respectively. The optical dose sensitivity obtained by conventional spectrophotometer and the fabricated optical scanner was 0.0453 and 0.0442 for NIPAM gels and 0.0244 and 0.0242 for PAGAT gels, respectively. The scanning results of the absorbed dose values showed that the new OCT and conventional spectrophotometer were in fair agreement. From the results, it could be concluded that the fabricated system is able to quantize the absorbed dose values in polymer gel samples with acceptable accuracy. PMID:26120572

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.

Radiochromic film calibration for the RQT9 quality beam

NASA Astrophysics Data System (ADS)

Costa, K. C.; Gomez, A. M. L.; Alonso, T. C.; Mourao, A. P.

2017-11-01

When ionizing radiation interacts with matter it generates energy deposition. Radiation dosimetry is important for medical applications of ionizing radiation due to the increasing demand for diagnostic radiology and radiotherapy. Different dosimetry methods are used and each one has its advantages and disadvantages. The film is a dose measurement method that records the energy deposition by the darkening of its emulsion. Radiochromic films have a little visible light sensitivity and respond better to ionizing radiation exposure. The aim of this study is to obtain the resulting calibration curve by the irradiation of radiochromic film strips, making it possible to relate the darkening of the film with the absorbed dose, in order to measure doses in experiments with X-ray beam of 120 kV, in computed tomography (CT). Film strips of GAFCHROMIC XR-QA2 were exposed according to RQT9 reference radiation, which defines an X-ray beam generated from a voltage of 120 kV. Strips were irradiated in "Laboratório de Calibração de Dosímetros do Centro de Desenvolvimento da Tecnologia Nuclear" (LCD / CDTN) at a dose range of 5-30 mGy, corresponding to the range values commonly used in CT scans. Digital images of the irradiated films were analyzed by using the ImageJ software. The darkening responses on film strips according to the doses were observed and they allowed obtaining the corresponding numeric values to the darkening for each specific dose value. From the numerical values of darkening, a calibration curve was obtained, which correlates the darkening of the film strip with dose values in mGy. The calibration curve equation is a simplified method for obtaining absorbed dose values using digital images of radiochromic films irradiated. With the calibration curve, radiochromic films may be applied on dosimetry in experiments on CT scans using X-ray beam of 120 kV, in order to improve CT acquisition image processes.

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.

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.

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

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.

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.

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.

Comparison of AAPM Addendum to TG-51, IAEA TRS-398, and JSMP 12: Calibration of photon beams in water.

PubMed

Kinoshita, Naoki; Oguchi, Hiroshi; Nishimoto, Yasuhiro; Adachi, Toshiki; Shioura, Hiroki; Kimura, Hirohiko; Doi, Kunio

2017-09-01

The American Association of Physicists in Medicine (AAPM) Working Group on TG-51 published an Addendum to the AAPM's TG-51 protocol (Addendum to TG-51) in 2014, and the Japan Society of Medical Physics (JSMP) published a new dosimetry protocol JSMP 12 in 2012. In this study, we compared the absorbed dose to water determined at the reference depth for high-energy photon beams following the recommendations given in AAPM TG-51 and the Addendum to TG-51, IAEA TRS-398, and JSMP 12. This study was performed using measurements with flattened photon beams with nominal energies of 6 and 10 MV. Three widely used ionization chambers with different compositions, Exradin A12, PTW 30013, and IBA FC65-P, were employed. Fully corrected charge readings obtained for the three chambers according to AAPM TG-51 and the Addendum to TG-51, which included the correction for the radiation beam profile (P rp ), showed variations of 0.2% and 0.3% at 6 and 10 MV, respectively, from the readings corresponding to IAEA TRS-398 and JSMP 12. The values for the beam quality conversion factor k Q obtained according to the three protocols agreed within 0.5%; the only exception was a 0.6% difference between the results obtained at 10 MV for Exradin A12 according to IAEA TRS-398 and AAPM TG-51 and the Addendum to TG-51. Consequently, the values for the absorbed dose to water obtained for the three protocols agreed within 0.4%; the only exception was a 0.6% difference between the values obtained at 10 MV for PTW 30013 according to AAPM TG-51 and the Addendum to TG-51, and JSMP 12. While the difference in the absorbed dose to water determined by the three protocols depends on the k Q and P rp values, the absorbed dose to water obtained according to the three protocols agrees within the relative uncertainties for the three protocols. © 2017 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.

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.

Individual dose reconstruction among residents living in the vicinity of the Semipalatinsk nuclear test site using EPR spectroscopy of tooth enamel.

PubMed

Ivannikov, A I; Zhumadilov, Zh; Gusev, B I; Miyazawa, Ch; Jiao, L; Skvortsov, V G; Stepanenko, V F; Takada, J; Hoshi, M

2002-08-01

Individual accumulated doses were determined by EPR spectroscopy of tooth enamel for 26 adult persons residing in territories adjacent to the Semipalatinsk Nuclear Test Site (SNTS). The absorbed dose values due to radiation from nuclear tests were obtained after subtracting the contribution of natural background radiation from the total accumulated dose. The determined dose values ranged up to 250 mGy, except for one person from Semipalatinsk city with a measured dose of 2.8 +/- 0.4 Gy. Increased dose values were determined for the individuals whose teeth were formed before 1962, the end of the atmospheric nuclear tests. These values were found to be significantly larger than those obtained for a group of younger residents of heavily exposed territories and the residents of territories not exposed to radioactive fallout. These increased dose values are consistent with those based on officially registered data for the Northeastern part of Kazakstan adjacent to SNTS, which was exposed to high levels of radioactive fallout from nuclear tests in period 1949-1962.

(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.

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.

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.

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.

High dose microCT does not contribute towards improved microPET/CT image quantitative accuracy and can limit longitudinal scanning of small animals

NASA Astrophysics Data System (ADS)

McDougald, Wendy A.; Collins, Richard; Green, Mark; Tavares, Adriana A. S.

2017-10-01

Obtaining accurate quantitative measurements in preclinical Positron Emission Tomography/Computed Tomography (PET/CT) imaging is of paramount importance in biomedical research and helps supporting efficient translation of preclinical results to the clinic. The purpose of this study was two-fold: (1) to investigate the effects of different CT acquisition protocols on PET/CT image quality and data quantification; and (2) to evaluate the absorbed dose associated with varying CT parameters. Methods: An air/water quality control CT phantom, tissue equivalent material phantom, an in-house 3D printed phantom and an image quality PET/CT phantom were imaged using a Mediso nanoPET/CT scanner. Collected data was analyzed using PMOD software, VivoQuant software and National Electric Manufactures Association (NEMA) software implemented by Mediso. Measured Hounsfield Unit (HU) in collected CT images were compared to the known HU values and image noise was quantified. PET recovery coefficients (RC), uniformity and quantitative bias were also measured. Results: Only less than 2% and 1% of CT acquisition protocols yielded water HU values < -80 and air HU values < -840, respectively. Four out of eleven CT protocols resulted in more than 100 mGy absorbed dose. Different CT protocols did not impact PET uniformity and RC, and resulted in <4% overall bias relative to expected radioactive concentration. Conclusion: Preclinical CT protocols with increased exposure times can result in high absorbed doses to the small animals. These should be avoided, as they do not contributed towards improved microPET/CT image quantitative accuracy and could limit longitudinal scanning of small animals.

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.

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.

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.

Intestinal pH and Absorption and Deposition of Ca 47 in the Rachitic Chick

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

Wasserman, R H; Taylor, A N

The effect of pH of the dosing solution on the relative tibia deposition of Ca 47 absorbed from the duodenum of rachitic and vit. D-treated chicks was examined. Vit. D had its usual enhancing effect on Ca 47 absorption; however, it was observed that the percent absorbed Ca47 deposited in tibia varied with intraduodenal pH and vit. D-status of the chick. At low pH values (1.9, 2.0), there were no differences in the percent of duodenally absorbed Ca 47 accumulated by tibia in rachitic or vit. D-treated chicks whereas, at high pH values, proportionally less of the absorbed Ca 47more » was deposited in rachitic tibia; pH was without effect on uptake of Ca 47 by tibia in the vit. D-treated birds.« less

Influence of gamma irradiation on the surface morphology, XRD and thermophysical properties of silicide hexoboride

NASA Astrophysics Data System (ADS)

Mirzayev, Matlab N.; Mehdiyeva, Ravan N.; Garibov, Ramin G.; Ismayilova, Narmin A.; Jabarov, Sakin H.

2018-05-01

In this study, compounds of B6Si were irradiated using a 60Co gamma source that have an energy line of 1.25 MeV at the absorbed dose rates from 14.6 kGy to 194.4 kGy. Surface morphology images of the sample obtained by Scanning Electron Microscope (SEM) show that the crystal structure at a high absorbed doses (D ≥ 145.8kGy) starts to be destroyed. X-ray diffraction studies revealed that with increasing radiation absorption dose, the spectrum intensity of the sample was decreased 1.96 times compared with the initial value. Thermal properties were studied by Differential scanning calorimetry (DSC) method in the temperature range of 30-1000∘C.

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

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

Assessment of human effective absorbed dose of 67 Ga-ECC based on biodistribution rat data.

PubMed

Shanehsazzadeh, Saeed; Yousefnia, Hassan; Lahooti, Afsaneh; Zolghadri, Samaneh; Jalilian, Amir Reza; Afarideh, Hossien

2015-02-01

In a diagnostic context, determination of absorbed dose is required before the introduction of a new radiopharmaceutical to the market to obtain marketing authorization from the relevant agencies. In this work, the absorbed dose of [67 Ga]-ethylenecysteamine cysteine [(67 Ga)ECC] to human organs was determined by using distribution data for rats. For biodistribution data, the animals were sacrificed by CO2 asphyxiation at selected times after injection (0.5, 2 and 48 h, n = 3 for each time interval), then the tissue (blood, heart, lung, brain, intestine, feces, skin, stomach, kidneys, liver, muscle and bone) were removed. The absorbed dose was determined by Medical Internal Radiation Dose (MIRD) method after calculating cumulated activities in each organ. Our prediction shows that a 185-MBq injection of (67)Ga-ECC into the humans might result in an estimated absorbed dose of 0.029 mGy in the whole body. The highest absorbed doses are observed in the spleen and liver with 33.766 and 16.847 mGy, respectively. The results show that this radiopharmaceutical can be a good SPECT tracer since it can be produced easily and also the absorbed dose in each organ is less than permitted absorbed dose.

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

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

Measurement of natural radioactivity and assessment of associated radiation hazards in soil around Baoji second coal-fired thermal power plant, China.

PubMed

Lu, Xinwei; Li, Xiaoxue; Yun, Pujun; Luo, Dacheng; Wang, Lijun; Ren, Chunhui; Chen, Cancan

2012-01-01

Activity concentrations of natural radionuclides (226)Ra, (232)Th and (40)K in soil around Baoji Second coal-fired thermal power plant of China were determined using gamma ray spectrometry. The mean activity concentrations of (226)Ra, (232)Th and (40)K in soil were found to be 40.3 ± 3.5, 59.6 ± 3.1 and 751.2 ± 12.4 Bq kg(-1), respectively, which are all higher than the corresponding average values in Shaanxi, Chinese and world soil. The radium equivalent activity (Ra(eq)), the air absorbed dose rate (D), the annual effective dose (E), the external hazard index (H(ex)) and internal hazard index (H(in)) were evaluated and compared with the internationally reported or reference values. All the soil samples have Ra(eq) lower than the limit of 370 Bq kg(-1) and H(ex) and H(in) less than unity. The overall mean outdoor terrestrial gamma air absorbed dose rate is ∼86.6 ± 3.4 nGy h(-1) and the corresponding outdoor annual effective dose is 0.106 ± 0.004 mSv, which is higher than the worldwide average (0.07 mSv y(-1)) for outdoor's annual effective dose.

Assessment of pharmacokinetic proportionality of levofloxacin and cyclosporine over a 100-fold dose range in healthy human volunteers.

PubMed

Lim, Mi-sun; Seong, Sook Jin; Park, Jeonghyeon; Seo, Jeong Ju; Lee, Joomi; Yu, Kyung-Sang; Lee, Hae Won; Yoon, Young-Ran

2012-04-01

Levofloxacin and cyclosporine show different pharmacokinetic properties, but are known to be dose proportional within the therapeutic range. The authors evaluated the pharmacokinetic proportionality of levofloxacin and cyclosporine over a 100-fold dose range in healthy human volunteers, by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Two independent, randomized, crossover studies were performed. For levofloxacin, eight volunteers were randomly assigned in a 1:1 ratio to receive a low dose (7.5 mg) orally or intravenously, followed by a 1-week washout period and administration via the alternate route. After another 1-week washout period, a therapeutic dose (750 mg) was administered to all eight subjects. For cyclosporine, another eight volunteers received a low dose (2 mg) or a therapeutic dose (200 mg) orally with a 1-week washout period. Drug concentrations were determined by LC-MS/MS. For levofloxacin, the mean values for dose-normalized C(max) and AUC(last) with the two doses were as follows: therapeutic dose, 15.2 ± 4.6 ng/ml/mg and 103.6 ± 15.5 ng·h/ml/mg, respectively; low dose, 17.1 ± 6.5 ng/ml/mg and 72.6 ± 8.7 ng·h/ml/mg, respectively. For cyclosporine, the mean values for dose-normalized C(max) and AUC(last) were as follows: therapeutic dose, 4.9 ± 1.5 ng/ml/mg and 15.4 ± 4.9 ng·h/ml/mg, respectively; low dose, 1.6 ± 0.6 ng/ml/mg and 9.3 ± 7.3 ng·h/ml/mg, respectively. In this study levofloxacin, which is completely absorbed and primarily eliminated renally without modification, showed better pharmacokinetic proportionality than cyclosporine, which is poorly absorbed and extensively metabolized.

Assessment of natural radioactivity levels in soil samples from some areas in Assiut, Egypt.

PubMed

El-Gamal, Hany; Farid, M El-Azab; Abdel Mageed, A I; Hasabelnaby, M; Hassanien, Hassanien M

2013-12-01

The natural radioactivity of soil samples from Assiut city, Egypt, was studied. The activity concentrations of 28 samples were measured with a NaI(Tl) detector. The radioactivity concentrations of (226)Ra, (232)Th, and (40)K showed large variations, so the results were classified into two groups (A and B) to facilitate the interpretation of the results. Group A represents samples collected from different locations in Assiut and characterized by low activity concentrations with average values of 46.15 ± 9.69, 30.57 ± 4.90, and 553.14 ± 23.19 for (226)Ra, (232)Th, and (40)K, respectively. Group B represents samples mainly collected from the area around Assiut Thermal Power Plant and characterized by very high activity concentrations with average values of 3,803 ± 145, 1,782 ± 98, and 1,377 ± 78 for (226)Ra, (232)Th, and (40)K, respectively. In order to evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity (Raeq), the absorbed dose rate (D), the annual effective dose rate (E), the external hazard index (H ex), and the annual gonadal dose equivalent (AGDE) have been calculated and compared with the internationally approved values. For group A, the calculated averages of these parameters are in good agreement with the international recommended values except for the absorbed dose rate and the AGDE values which are slightly higher than the international recommended values. However, for group B, all obtained averages of these parameters are much higher by several orders of magnitude than the international recommended values. The present work provides a background of radioactivity concentrations in the soil of Assiut.

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.

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.

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

PubMed

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

2014-01-01

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

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

Evaluation of external and internal irradiation on uranium mining enterprise staff by tooth enamel EPR spectroscopy

NASA Astrophysics Data System (ADS)

Zhumadilov, Kassym; Ivannikov, Alexander; Khailov, Artem; Orlenko, Sergei; Skvortsov, Valeriy; Stepanenko, Valeriy; Kuterbekov, Kairat; Toyoda, Shin; Kazymbet, Polat; Hoshi, Masaharu

2017-11-01

In order to estimate radiation effects on uranium enterprise staff and population teeth samples were collected for EPR tooth enamel dosimetry from population of Stepnogorsk city and staff of uranium mining enterprise in Shantobe settlment (Akmola region, North of Kazakhstan). By measurements of tooth enamel EPR spectra, the total absorbed dose in the enamel samples and added doses after subtraction of the contribution of natural background radiation are determined. For the population of Stepnogorsk city average added dose value of 4 +/- 11 mGy with variation of 51 mGy was obtained. For the staff of uranium mining enterprise in Shantobe settlment average value of added dose 95 +/- 20 mGy, with 85 mGy variation was obtained. Higher doses and the average value and a large variation for the staff, probably is due to the contribution of occupational exposure.

Assessment of reaction intermediates of gamma radiation-induced degradation of ofloxacin in aqueous solution.

PubMed

Changotra, Rahil; Guin, Jhimli Paul; Varshney, Lalit; Dhir, Amit

2018-06-01

Gamma radiolytic degradation of an antibiotic, ofloxacin (OFX) was investigated under different experimental conditions. The parameters such as initial OFX concentration, solution pH, absorbed dose and the concentrations of inorganic (CO 3 2- ) and organic (t-BuOH) additives were optimized to achieve the efficient degradation of OFX. The degradation dose constant values of OFX were calculated as 2.364, 1.159, 0.776 and 0.618 kGy -1 for the initial OFX concentrations of 0.05, 0.1, 0.15 and 0.2 mM with their corresponding (G (-OFX)) values of 0.481, 0.684, 1.755 and 1.971, respectively. Degradation rate of OFX was significantly increased with increase in the absorbed dose and decrease in the initial OFX concentration under acidic condition when compared to neutral or alkaline condition. Reaction of OFX in the presence of CO 3 2- and t-BuOH showed that the degradation was primarily caused by the reaction of OFX with radiolytically generated reactive hydroxyl radicals. Mineralization extent of OFX was determined in terms of percentage reduction in total organic carbon (TOC) and results revealed that the addition of H 2 O 2 enhanced the mineralization of OFX from 29% to 36.1% with H 2 O 2 dose of 0.5 mM at an absorbed dose of 3.0 kGy. Based on the LC-QTOF-MS analysis, gamma radiolytic degradation intermediates/products of OFX were identified and the possible degradation pathways of OFX were proposed. Cytotoxicity study of the irradiated OFX solutions showed that gamma radiation has potential to detoxify OFX. Copyright © 2018 Elsevier Ltd. All rights reserved.

Development of modern approach to absorbed dose assessment in radionuclide therapy, based on Monte Carlo method simulation of patient scintigraphy

NASA Astrophysics Data System (ADS)

Lysak, Y. V.; Klimanov, V. A.; Narkevich, B. Ya

2017-01-01

One of the most difficult problems of modern radionuclide therapy (RNT) is control of the absorbed dose in pathological volume. This research presents new approach based on estimation of radiopharmaceutical (RP) accumulated activity value in tumor volume, based on planar scintigraphic images of the patient and calculated radiation transport using Monte Carlo method, including absorption and scattering in biological tissues of the patient, and elements of gamma camera itself. In our research, to obtain the data, we performed modeling scintigraphy of the vial with administered to the patient activity of RP in gamma camera, the vial was placed at the certain distance from the collimator, and the similar study was performed in identical geometry, with the same values of activity of radiopharmaceuticals in the pathological target in the body of the patient. For correct calculation results, adapted Fisher-Snyder human phantom was simulated in MCNP program. In the context of our technique, calculations were performed for different sizes of pathological targets and various tumors deeps inside patient’s body, using radiopharmaceuticals based on a mixed β-γ-radiating (131I, 177Lu), and clear β- emitting (89Sr, 90Y) therapeutic radionuclides. Presented method can be used for adequate implementing in clinical practice estimation of absorbed doses in the regions of interest on the basis of planar scintigraphy of the patient with sufficient accuracy.

Investigation of the chamber correction factor (k(ch)) for the UK secondary standard ionization chamber (NE2561/NE2611) using medium-energy x-rays.

PubMed

Rosser, K E

1998-11-01

This paper evaluates the characteristics of ionization chambers for the measurement of absorbed dose to water for medium-energy x-rays. The values of the chamber correction factor, k(ch), used in the IPEMB code of practice for the UK secondary standard (NE2561/NE2611) ionization chamber are derived and their constituent factors examined. The comparison of the chambers' responses in air revealed that of the chambers tested only the NE2561, NE2571 and NE2505 exhibit a flat (within 5%) energy response in air. Under no circumstances should the NACP, Sanders electron chamber, or any chamber that has a wall made of high atomic number material, be used for medium-energy x-ray dosimetry. The measurements in water reveal that a chamber that has a substantial housing, such as the PTW Grenz chamber, should not be used to measure absorbed dose to water in this energy range. The value of k(ch) for an NE2561 chamber was determined by measuring the absorbed dose to water and comparing it with that for an NE2571 chamber, for which k(ch) data have been published. The chamber correction factor varies from 1.023 +/- 0.03 to 1.018 +/- 0.001 for x-ray beams with HVL between 0.15 and 4 mm Cu. The values agree with that for an NE2571 chamber within the experimental uncertainty. The corrections due to the stem, waterproof sleeve and replacement of the phantom material by the chamber for an NE2561 chamber are described.

Assessment of ionization chamber correction factors in photon beams using a time saving strategy with PENELOPE code.

PubMed

Reis, C Q M; Nicolucci, P

2016-02-01

The purpose of this study was to investigate Monte Carlo-based perturbation and beam quality correction factors for ionization chambers in photon beams using a saving time strategy with PENELOPE code. Simulations for calculating absorbed doses to water using full spectra of photon beams impinging the whole water phantom and those using a phase-space file previously stored around the point of interest were performed and compared. The widely used NE2571 ionization chamber was modeled with PENELOPE using data from the literature in order to calculate absorbed doses to the air cavity of the chamber. Absorbed doses to water at reference depth were also calculated for providing the perturbation and beam quality correction factors for that chamber in high energy photon beams. Results obtained in this study show that simulations with phase-space files appropriately stored can be up to ten times shorter than using a full spectrum of photon beams in the input-file. Values of kQ and its components for the NE2571 ionization chamber showed good agreement with published values in the literature and are provided with typical statistical uncertainties of 0.2%. Comparisons to kQ values published in current dosimetry protocols such as the AAPM TG-51 and IAEA TRS-398 showed maximum percentage differences of 0.1% and 0.6% respectively. The proposed strategy presented a significant efficiency gain and can be applied for a variety of ionization chambers and clinical photon beams. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Skeletal dosimetry in a voxel-based rat phantom for internal exposures to photons and electrons

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

Xie Tianwu; Han Dao; Liu Yang

2010-05-15

Purpose: The skeleton makes a significant contribution to the whole body absorbed dose evaluation of rats, since the bone marrow and bone surface in the skeleton express high radiosensitivity and are considered to be important dose-limiting tissues. The bone marrow can be categorized as red bone marrow (RBM) and yellow bone marrow (YBM). It is important to investigate the bone marrow in skeletal dosimetry. Methods: Cryosectional color images of the skeleton of a 156 g rat were segmented into mineral bone (including cortical bone and trabecular bone), RBM, and YBM. These three tissue types were identified at 40 different bonemore » sites and integrated into a previously developed voxel-based rat computational phantom. Photon and electron skeletal absorbed fractions were then calculated using the MCNPX Monte Carlo code. Results: Absorbed fraction (AF) and specific absorbed fraction (SAF) for mineral bone, RBM, and YBM at the 40 different bone sites were established for monoenergetic photon and electron sources placed in 18 organs and seven bone sites. Discrete photon energy was varied from 0.01 to 5.0 MeV in 21 discrete steps, while 21 discrete electron energies were studied, from 0.1 to 10.0 MeV. The trends and values found were consistent with the results of other researchers [M. G. Stabin, T. E. Peterson, G. E. Holburn, and M. A. Emmons, ''Voxel-based mouse and rat models for internal dose calculations,'' J. Nucl. Med. 47, 655-659 (2006)]. S-factors for the radionuclides {sup 169}Er, {sup 143}Pr, {sup 89}Sr, {sup 32}P, and {sup 90}Y, located in 18 organs and seven bone sites for the skeleton, were calculated and are provided in detail. Conclusions: For internal dose calculations, the AF data reveal that the mineral bone in the rat skeletal system is responsible for significant attenuation of gamma rays, especially at low energies. The photon SAF curves of RBM show that, for photon energies greater than 0.6 MeV, there is an increase in secondary photons emitted from the mineral bone as photon energy increases. The SAF values calculated in this study can also be used to determine the absorbed dose to the skeletal system of rats. The S-factors generated here will be useful in preclinical targeted radiotherapy experiments.« less

An example of problems in dose reconstruction from doses formed by electromagnetic irradiation by different energy sources.

PubMed

Kirillov, Vladimir; Kuchuro, Joseph; Tolstik, Sergey; Leonova, Tatyana

2010-02-01

Dose reconstruction for citizens of Belarus affected by the Chernobyl accident showed an unexpectedly wide range of doses. Using the EPR tooth enamel dosimetry method, it has been demonstrated that when the tooth enamel dose was formed due to x-rays with effective energy of 34 keV and the additional irradiation of enamel samples was performed by gamma radiation with mean energy of 1,250 keV, it led to a considerable increase in the reconstructed absorbed dose as compared with the applied. In the case when the dose was formed due to gamma radiation and the additional irradiation was performed by x-rays, it led to a considerable decrease in the reconstructed dose as compared with the applied. When the dose formation and the additional irradiation were carried out from external sources of electromagnetic radiation of equal energy, the reconstructed dose value was close to that of the applied. The obtained data show that for adequate reconstruction of individual absorbed doses by the EPR tooth enamel spectra, it is necessary to take into account the contribution from diagnostic x-ray examination of the teeth, jaw, and skull of some individuals who were exposed to a combined effect of the external gamma radiation and x-rays.

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.

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.

KEY COMPARISON: Comparison of the standards for absorbed dose to water of the ENEA-INMRI (Italy) and the BIPM for 60Co γ rays

NASA Astrophysics Data System (ADS)

Kessler, C.; Allisy-Roberts, P. J.; Burns, D. T.; Guerra, A. S.; Laitano, R. F.; Pimpinella, M.

2010-01-01

A comparison of the standards for absorbed dose to water of the Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti of the Ente per le Nuove Tecnologie, l'Energia e l'Ambiente, Italy (ENEA-INMRI), and of the Bureau International des Poids et Mesures (BIPM) has been made in 60Co gamma radiation under the auspices of the key comparison BIPM.RI(I)-K4. The comparison result, based on the calibration coefficients for three transfer standards and expressed as a ratio of the ENEA and the BIPM standards for absorbed dose to water, is 0.9999 (0.0044). The present 2007 result replaces the earlier ENEA value in this key comparison. The degrees of equivalence between the ENEA and the other participants in this comparison have been calculated and the results are given in the form of a matrix for the ten national metrology institutes (NMIs) that have published results in this ongoing comparison for absorbed dose to water. A graphical presentation is also given. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

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.

Estimate of S-values for children due to six positron emitting radionuclides used in PET examinations

NASA Astrophysics Data System (ADS)

Belinato, Walmir; Santos, William S.; Perini, Ana P.; Neves, Lucio P.; Caldas, Linda V. E.; Souza, Divanizia N.

2017-11-01

Positron emission tomography (PET) has revolutionized the diagnosis of cancer since its conception. When combined with computed tomography (CT), PET/CT performed in children produces highly accurate diagnoses from images of regions affected by malignant tumors. Considering the high risk to children when exposed to ionizing radiation, a dosimetric study for PET/CT procedures is necessary. Specific absorbed fractions (SAF) were determined for monoenergetic photons and positrons, as well as the S-values for six positron emitting radionuclides (11C, 13N, 18F, 68Ga, 82Rb, 15O), and 22 source organs. The study was performed for six pediatric anthropomorphic hybrid models, including the newborn and 1 year hermaphrodite, 5 and 10-year-old male and female, using the Monte Carlo N-Particle eXtended code (MCNPX, version 2.7.0). The results of the SAF in source organs and S-values for all organs showed to be inversely related to the age of the phantoms, which includes the variation of body weight. The results also showed that radionuclides with higher energy peak emission produces larger auto absorbed S-values due to local dose deposition by positron decay. The S-values for the source organs are considerably larger due to the interaction of tissue with non-penetrating particles (electrons and positrons) and present a linear relationship with the phantom body masses. The results of the S-values determined for positron-emitting radionuclides can be used to assess the radiation dose delivered to pediatric patients subjected to PET examination in clinical settings. The novelty of this work is associated with the determination of auto absorbed S-values, in six new pediatric virtual anthropomorphic phantoms, for six emitting positrons, commonly employed in PET exams.

Monte Carlo-based evaluation of S-values in mouse models for positron-emitting radionuclides

NASA Astrophysics Data System (ADS)

Xie, Tianwu; Zaidi, Habib

2013-01-01

In addition to being a powerful clinical tool, Positron emission tomography (PET) is also used in small laboratory animal research to visualize and track certain molecular processes associated with diseases such as cancer, heart disease and neurological disorders in living small animal models of disease. However, dosimetric characteristics in small animal PET imaging are usually overlooked, though the radiation dose may not be negligible. In this work, we constructed 17 mouse models of different body mass and size based on the realistic four-dimensional MOBY mouse model. Particle (photons, electrons and positrons) transport using the Monte Carlo method was performed to calculate the absorbed fractions and S-values for eight positron-emitting radionuclides (C-11, N-13, O-15, F-18, Cu-64, Ga-68, Y-86 and I-124). Among these radionuclides, O-15 emits positrons with high energy and frequency and produces the highest self-absorbed S-values in each organ, while Y-86 emits γ-rays with high energy and frequency which results in the highest cross-absorbed S-values for non-neighbouring organs. Differences between S-values for self-irradiated organs were between 2% and 3%/g difference in body weight for most organs. For organs irradiating other organs outside the splanchnocoele (i.e. brain, testis and bladder), differences between S-values were lower than 1%/g. These appealing results can be used to assess variations in small animal dosimetry as a function of total-body mass. The generated database of S-values for various radionuclides can be used in the assessment of radiation dose to mice from different radiotracers in small animal PET experiments, thus offering quantitative figures for comparative dosimetry research in small animal models.

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

Technical note: estimating absorbed doses to the thyroid in CT.

PubMed

Huda, Walter; Magill, Dennise; Spampinato, Maria V

2011-06-01

To describe a method for estimating absorbed doses to the thyroid in patients undergoing neck CT examinations. Thyroid doses in anthropomorphic phantoms were obtained for all 23 scanner dosimetry data sets in the ImPACT CT patient dosimetry calculator. Values of relative thyroid dose [R(thy)(L)], defined as the thyroid dose for a given scan length (L) divided by the corresponding thyroid dose for a whole body scan, were determined for neck CT scans. Ratios of the maximum thyroid dose to the corresponding CTDI(vol) and [D'(thy)], were obtained for two phantom diameters. The mass-equivalent water cylinder of any patient can be derived from the neck cross-sectional area and the corresponding average Hounsfield Unit, and compared to the 16.5-cm diameter water cylinder that models the ImPACT anthropomorphic phantom neck. Published values of relative doses in water cylinders of varying diameter were used to adjust thyroid doses in the anthropomorphic phantom to those of any sized patient. Relative thyroid doses R(thy)(L) increase to unity with increasing scan length and with very small difference between scanners. A 10-cm scan centered on the thyroid would result in a dose that is, nearly 90% of the thyroid dose from a whole body scan when performed using the constant radiographic techniques. At 120 kV, the average value of D'(thy) for the 16-cm diameter was 1.17 +/- 0.05 and was independent of CT vendor and year of CT scanner, and choice of x-ray tube voltage. The corresponding average value of D'(thy) in the 32-cm diameter phantom was 2.28 +/- 0.22 and showed marked variations depending on vendor, year of introduction into clinical practice as well as x-ray tube voltage. At 120 kV, a neck equivalent to a 10-cm diameter cylinder of water would have thyroid doses 36% higher than those in the ImPACT phantom, whereas a neck equivalent to a 25-cm cylinder diameter would have thyroid doses 35% lower. Patient thyroid doses can be estimated by taking into account the amount of radiation used to perform the CT examination (CTDI(vol)) and accounting for scan length and patient anatomy (i.e., neck diameter) at the thyroid location.

Detailed Distribution Map of Absorbed Dose Rate in Air in Tokatsu Area of Chiba Prefecture, Japan, Constructed by Car-Borne Survey 4 Years after the Fukushima Daiichi Nuclear Power Plant Accident.

PubMed

Inoue, Kazumasa; Arai, Moeko; Fujisawa, Makoto; Saito, Kyouko; Fukushi, Masahiro

2017-01-01

A car-borne survey was carried out in the northwestern, or Tokatsu, area of Chiba Prefecture, Japan, to make a detailed distribution map of absorbed dose rate in air four years after the Fukushima Daiichi Nuclear Power Plant accident. This area was chosen because it was the most heavily radionuclide contaminated part of Chiba Prefecture and it neighbors metropolitan Tokyo. Measurements were performed using a 3-in × 3-in NaI(Tl) scintillation spectrometer in June 2015. The survey route covered the whole Tokatsu area which includes six cities. A heterogeneous distribution of absorbed dose rate in air was observed on the dose distribution map. Especially, higher absorbed dose rates in air exceeding 80 nGy h-1 were observed along national roads constructed using high porosity asphalt, whereas lower absorbed dose rates in air were observed along local roads constructed using low porosity asphalt. The difference between these asphalt types resulted in a heterogeneous dose distribution in the Tokatsu area. The mean of the contribution ratio of artificial radionuclides to absorbed dose rate in air measured 4 years after the accident was 29% (9-50%) in the Tokatsu area. The maximum absorbed dose rate in air, 201 nGy h-1 was observed at Kashiwa City. Radiocesium was deposited in the upper 1 cm surface layer of the high porosity asphalt which was collected in Kashiwa City and the environmental half-life of the absorbed dose rate in air was estimated to be 1.7 years.

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.

Visible absorption properties of radiation exposed XR type-T radiochromic film.

PubMed

Butson, Martin J; Cheung, Tsang; Yu, Peter K N

2004-10-07

The visible absorption spectra of Gafchromic XR type-T radiochromic film have been investigated to analyse the dosimetry characteristics of the film with visible light densitometers. Common densitometers can use photospectrometry, fluorescent light (broad-band visible), helium neon (632 nm), light emitting diode (LED) or other specific bandwidth spectra. The visible absorption spectra of this film when exposed to photon radiation show peaks at 676 nm and 618 nm at 2 Gy absorbed doses which shift to slightly lower wavelengths (662 nm and 612 nm at 8 Gy absorbed dose) at higher doses. This is similar to previous models of Gafchromic film such as MD-55-2 and HS but XR type-T also includes a large absorption at lower visible wavelengths due to 'yellow' dyes placed within the film to aid with visible recognition of the film exposure level. The yellow dye band pass is produced at approximately 520 nm to 550 nm and absorbs wavelengths lower than this value within the visible spectrum. This accounts for the colour change from yellow to brown through the added absorption in the red wavelengths with radiation exposure. The film produces a relatively high dose sensitivity with up to 0.25 OD units per Gy change at 672 nm at 100 kVp x-ray energy. Variations in dose sensitivity can be achieved by varying wavelength analysis.

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).

Improvements in opti-chromic dosimeters for radiation processing

NASA Astrophysics Data System (ADS)

Humpherys, K. C.; Kantz, A. D.

"Opti-Chromic" dosimeters consisting of radiachromic dye in flourinated polymer tubing have been introduced as a dosimetry system in the range from 10 1 to 5 × 10 4 Gy. Batches of "Opti-Chromic" dosimeters have been produced to evaluate performance under large scale industrial conditions. A systematic study was undertaken to determine the effect of various dosimeter parameters on radiation sensitivity, shelf life, and response characteristics at the higher absorbed doses. These parameters were (A) Type of flourinated polymer tubing; (B) Organic solvent used to activate the radiachromic dye; (C) Concentration of radiachromic dye; (D) Additives to provide proper viscosity, color stability, and high-dose response. Prototype batches were produced and experimental dosimeters exposed to a range of absorbed doses and the response measured as a function of shelf life and dose. The results of the study are presented, and an improved formulation recommended for application to Food Processing. Other formulations may be of value in specific requirements of sensitivity or temperature.

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

Measurements of environmental terrestrial gamma radiation dose rate in three mountainous locations in the western region of Saudi Arabia

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

Al-Ghorabie, Fayez H.H.

2005-06-01

This paper describes measurements of external gamma radiation dose rate from terrestrial gamma-rays 1 m above the ground in three different mountainous locations in the western region of the Kingdom of Saudi Arabia. These locations are At-Taif city, Al-Hada village, and Ash-Shafa village. CaSO{sub 4}:Dy (TLD-900) thermoluminescent dosimeters were used for the detection of terrestrial gamma radiation at 40 different places in the three locations. The values of terrestrial gamma radiation dose rate measured ranged between 14 and 279 nGy h{sup -1} for the time interval from June 2001 to June 2002. The measured dose rate varied with the seasonmore » of the year. The average gamma radiation dose rates were 468, 541, and 781 {mu}Gy y{sup -1} for At-Taif city, Al-Hada village, and Ash-Shafa village, respectively. The corresponding average absorbed doses to the population of the three locations were 328, 379, and 547 {mu}Sv y{sup -1}, respectively. The quality factor of 0.7 Sv Gy{sup -1} was applied in the calculations of the absorbed dose to humans.« less

Analytical model for out-of-field dose in photon craniospinal irradiation

NASA Astrophysics Data System (ADS)

Taddei, Phillip J.; Jalbout, Wassim; Howell, Rebecca M.; Khater, Nabil; Geara, Fady; Homann, Kenneth; Newhauser, Wayne D.

2013-11-01

The prediction of late effects after radiotherapy in organs outside a treatment field requires accurate estimations of out-of-field dose. However, out-of-field dose is not calculated accurately by commercial treatment planning systems (TPSs). The purpose of this study was to develop and test an analytical model for out-of-field dose during craniospinal irradiation (CSI) from photon beams produced by a linear accelerator. In two separate evaluations of the model, we measured absorbed dose for a 6 MV CSI using thermoluminescent dosimeters placed throughout an anthropomorphic phantom and fit the measured data to an analytical model of absorbed dose versus distance outside of the composite field edge. These measurements were performed in two separate clinics—the University of Texas MD Anderson Cancer Center (MD Anderson) and the American University of Beirut Medical Center (AUBMC)—using the same phantom but different linear accelerators and TPSs commissioned for patient treatments. The measurement at AUBMC also included in-field locations. Measured dose values were compared to those predicted by TPSs and parameters were fit to the model in each setting. In each clinic, 95% of the measured data were contained within a factor of 0.2 and one root mean square deviation of the model-based values. The root mean square deviations of the mathematical model were 0.91 cGy Gy-1 and 1.67 cGy Gy-1 in the MD Anderson and AUBMC clinics, respectively. The TPS predictions agreed poorly with measurements in regions of sharp dose gradient, e.g., near the field edge. At distances greater than 1 cm from the field edge, the TPS underestimated the dose by an average of 14% ± 24% and 44% ± 19% in the MD Anderson and AUBMC clinics, respectively. The in-field measured dose values of the measurement at AUBMC matched the dose values calculated by the TPS to within 2%. Dose algorithms in TPSs systematically underestimated the actual out-of-field dose. Therefore, it is important to use an improved model based on measurements when estimating out-of-field dose. The model proposed in this study performed well for this purpose in two clinics and may be applicable in other clinics with similar treatment field configurations.

The influence of air humidity on an unsealed ionization chamber in a linear accelerator.

PubMed

Blad, B; Nilsson, P; Knöös, T

1996-11-01

The safe and accurate delivery of the prescribed absorbed dose is the central function of the dose monitoring and beam stabilization system in a medical linear accelerator. The absorbed dose delivered to the patient during radiotherapy is often monitored by a transmission ionization chamber. Therefore it is of utmost importance that the chamber behaves correctly. We have noticed that the sensitivity of an unsealed chamber in a Philips SL linear accelerator changes significantly, especially during and after the summer season. The reason for this is probably a corrosion effect of the conductive plates in the chamber due to the increased relative humidity during hot periods. We have found that the responses of the different ion chamber plates change with variations in air humidity and that they do not return to their original values when the air humidity is returned to ambient conditions.

Ozone pretreatment and fermentative hydrolysis of wheat straw

NASA Astrophysics Data System (ADS)

Ben'ko, E. M.; Chukhchin, D. G.; Lunin, V. V.

2017-11-01

Principles of the ozone pretreatment of wheat straw for subsequent fermentation into sugars are investigated. The optimum moisture contents of straw in the ozonation process are obtained from data on the kinetics of ozone absorbed by samples with different contents of water. The dependence of the yield of reducing sugars in the fermentative reaction on the quantity of absorbed ozone is established. The maximum conversion of polysaccharides is obtained at ozone doses of around 3 mmol/g of biomass, and it exceeds the value for nonozonated samples by an order of magnitude. The yield of sugar falls upon increasing the dose of ozone. The process of removing lignin from the cell walls of straw during ozonation is visualized by means of scanning electron microscopy.

Sci-Sat AM: Radiation Dosimetry and Practical Therapy Solutions - 06: Investigation of an absorbed dose to water formalism for a miniature low-energy x-ray source

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

Watson, Peter; Seuntjens, Jan

Purpose: We present a formalism for calculating the absorbed dose to water from a miniature x-ray source (The INTRABEAM system, Carl Zeiss), using a parallel-plate ionization chamber calibrated in terms of air-kerma. Monte Carlo calculations were performed to derive a chamber conversion factor (C{sub Q}) from reference air-kerma to dose to water for the INTRABEAM. C{sub Q} was investigated as a function of depth in water, and compared with the manufacturer’s reported value. The effect of chamber air cavity dimension tolerance was also investigated. Methods: Air-kerma (A{sub k}) from a reference beam was calculated using the EGSnrc user code cavity.more » Using egs-chamber, a model of a PTW 34013 parallel-plate ionization chamber was created according to manufacturer specifications. The dose to the chamber air cavity (D{sub gas}) was simulated both in-air (with reference beam) and in-water (with INTRABEAM source). Dose to a small water voxel (D{sub w}) was also calculated. C{sub Q} was derived from these quantities. Results: C{sub Q} was found to vary by up to 15% (1.30 vs 1.11) between chamber dimension extremes. The agreement between chamber C{sub Q} was found to improve with increasing depth in water. However, in all cases investigated, C{sub Q} was larger than the manufacturer reported value of 1.054. Conclusions: Our results show that cavity dimension tolerance has a significant effect on C{sub Q}, with differences as large as 15%. In all cases considered, C{sub Q} was found to be larger than the reported value of 1.054. This suggests that the recommended calculation underestimates the dose to water.« less

Assessment of natural radioactivity and radiological hazards in building materials used in Yan'an, China.

PubMed

Lu, Xinwei; Li, Nan; Yang, Guang; Zhao, Caifeng

2013-03-01

The concentration of natural radionuclides in commonly used building materials collected from Yan'an, China, was determined using gamma ray spectroscopy with a NaI(Tl) detector. The activity concentration of ²²⁶Ra, ²³²Th, and ⁴⁰K in the studied building materials ranges from 9.4-73.1, 11.5-86.9, and 258.9-1,055.1 Bq kg⁻¹, respectively. The concentrations for these natural radionuclides were compared with the reported data of other countries and the world mean values for soil. The radium equivalent activity (Raeq), external hazard index (Hex), internal hazard index (Hin), indoor air absorbed dose rate, and annual effective dose rate due to natural radionuclides in samples were estimated to assess radiological hazards for people living in dwellings made of the studied building materials. The calculated Raeq values of all building materials (75.7-222.1 Bq kg⁻¹) are lower than the limit of 370 Bq kg⁻¹. The values of Hex and Hin are less than unity. The mean values of indoor air absorbed dose rates of all building materials (101.0 ± 14.1-177.0 ± 6.8 nGy h⁻¹) are higher than the world population-weighted average of 84 nGy h⁻¹, while the mean values of annual effective dose range from 0.50 ± 0.07-0.87 ± 0.03 mSv y⁻¹, which are lower than the recommended limit of 1 mSv y⁻¹. It is found that these materials may be used safely as construction materials and do not pose significant radiation hazards to inhabitants.

Assessment of natural radioactivity in various commercial tiles used for building purposes in Nigeria.

PubMed

Joel, E S; Maxwell, O; Adewoyin, O O; Ehi-Eromosele, C O; Embong, Z; Oyawoye, F

2018-01-01

In this study, we evaluated the activity concentration of natural radionuclides ( 226 Ra, 232 Th and 40 K) for fifteen (15) different brands of tile samples used for building purposes in Nigeria. The tile samples were analyzed using High purity Germanium gamma detector. The mean activity concentrations of 226 Ra, 232 Th, and 40 K were observed to be 61.1 ± 5.5 Bq/kg, 70.2 ± 6.08 Bq/kg and 514.7 ± 59.8 Bq/kg respectively. Various hazard indices such as absorbed dose rate, external and internal hazard index, annual effective dose rate, Gamma activity Index (Iγ) and Alpha Index (Iα) were calculated. The obtained results showed that the mean radium equivalent activity (Raeq), the absorbed dose rate (D), external and internal hazard index, the annual effective dose (AEDR) equivalent, Gamma activity Index (Iγ) and Alpha Index (Iα) were: 204.42 Bq/kg, 177.61 nGyh -1 , 0.55, 0.77, 0.96 mSvyr -1 , 0.74 and 0.32 respectively. The average value of radium equivalent obtained in this study is less than that of the recommended value of 370 Bq/kg but the average values of the other radiological hazards for some samples are found to be slightly above international recommended values except H ex , H in and AEDE which are within the international reference value of unity. The measured concentrations of these radioactive materials were correlated with other previous result obtained from similar tile materials used in other countries and found to be in good agreement with the international standard, however, the tiles are recommended for decoration purposes in Nigeria.

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

Xie, Tianwu; Lee, Choonsik; Bolch, Wesley E.

Purpose: Nuclear cardiology plays an important role in clinical assessment and has enormous impact on the management of a variety of cardiovascular diseases. Pediatric patients at different age groups are exposed to a spectrum of radiation dose levels and associated cancer risks different from those of adults in diagnostic nuclear medicine procedures. Therefore, comprehensive radiation dosimetry evaluations for commonly used myocardial perfusion imaging (MPI) and viability radiotracers in target population (children and adults) at different age groups are highly desired. Methods: Using Monte Carlo calculations and biological effects of ionizing radiation VII model, we calculate the S-values for a numbermore » of radionuclides (Tl-201, Tc-99m, I-123, C-11, N-13, O-15, F-18, and Rb-82) and estimate the absorbed dose and effective dose for 12 MPI radiotracers in computational models including the newborn, 1-, 5-, 10-, 15-yr-old, and adult male and female computational phantoms. Results: For most organs, {sup 201}Tl produces the highest absorbed dose whereas {sup 82}Rb and {sup 15}O-water produce the lowest absorbed dose. For the newborn baby and adult patient, the effective dose of {sup 82}Rb is 48% and 77% lower than that of {sup 99m}Tc-tetrofosmin (rest), respectively. Conclusions: {sup 82}Rb results in lower effective dose in adults compared to {sup 99m}Tc-labeled tracers. However, this advantage is less apparent in children. The produced dosimetric databases for various radiotracers used in cardiovascular imaging, using new generation of computational models, can be used for risk-benefit assessment of a spectrum of patient population in clinical nuclear cardiology practice.« less

Detailed Distribution Map of Absorbed Dose Rate in Air in Tokatsu Area of Chiba Prefecture, Japan, Constructed by Car-Borne Survey 4 Years after the Fukushima Daiichi Nuclear Power Plant Accident

PubMed Central

Inoue, Kazumasa; Arai, Moeko; Fujisawa, Makoto; Saito, Kyouko; Fukushi, Masahiro

2017-01-01

A car-borne survey was carried out in the northwestern, or Tokatsu, area of Chiba Prefecture, Japan, to make a detailed distribution map of absorbed dose rate in air four years after the Fukushima Daiichi Nuclear Power Plant accident. This area was chosen because it was the most heavily radionuclide contaminated part of Chiba Prefecture and it neighbors metropolitan Tokyo. Measurements were performed using a 3-in × 3-in NaI(Tl) scintillation spectrometer in June 2015. The survey route covered the whole Tokatsu area which includes six cities. A heterogeneous distribution of absorbed dose rate in air was observed on the dose distribution map. Especially, higher absorbed dose rates in air exceeding 80 nGy h-1 were observed along national roads constructed using high porosity asphalt, whereas lower absorbed dose rates in air were observed along local roads constructed using low porosity asphalt. The difference between these asphalt types resulted in a heterogeneous dose distribution in the Tokatsu area. The mean of the contribution ratio of artificial radionuclides to absorbed dose rate in air measured 4 years after the accident was 29% (9–50%) in the Tokatsu area. The maximum absorbed dose rate in air, 201 nGy h-1 was observed at Kashiwa City. Radiocesium was deposited in the upper 1 cm surface layer of the high porosity asphalt which was collected in Kashiwa City and the environmental half-life of the absorbed dose rate in air was estimated to be 1.7 years. PMID:28129382

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.

Development of an abiraterone acetate formulation with improved oral bioavailability guided by absorption modeling based on in vitro dissolution and permeability measurements.

PubMed

Solymosi, Tamás; Ötvös, Zsolt; Angi, Réka; Ordasi, Betti; Jordán, Tamás; Semsey, Sándor; Molnár, László; Ránky, Soma; Filipcsei, Genovéva; Heltovics, Gábor; Glavinas, Hristos

2017-10-30

Particle size reduction of drug crystals in the presence of surfactants (often called "top-down" production methods) is a standard approach used in the pharmaceutical industry to improve bioavailability of poorly soluble drugs. Based on the mathematical model used to predict the fraction dose absorbed this formulation approach is successful when dissolution rate is the main rate limiting factor of oral absorption. In case compound solubility is also a major factor this approach might not result in an adequate improvement in bioavailability. Abiraterone acetate is poorly water soluble which is believed to be responsible for its very low bioavailability in the fasted state and its significant positive food effect. In this work, we have successfully used in vitro dissolution, solubility and permeability measurements in biorelevant media to describe the dissolution characteristics of different abiraterone acetate formulations. Mathematical modeling of fraction dose absorbed indicated that reducing the particle size of the drug cannot be expected to result in significant improvement in bioavailability in the fasted state. In the fed state, the same formulation approach can result in a nearly complete absorption of the dose; thereby, further increasing the food effect. Using a "bottom-up" formulation method we improved both the dissolution rate and the apparent solubility of the compound. In beagle dog studies, this resulted in a ≫>10-fold increase in bioavailability in the fasted state when compared to the marketed drug and the elimination of the food effect. Calculated values of fraction dose absorbed were in agreement with the observed relative bioavailability values in beagle dogs. Copyright © 2017 Elsevier B.V. All rights reserved.

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

Estimation of absorbed dose in clinical radiotherapy linear accelerator beams: Effect of ion chamber calibration and long-term stability

PubMed Central

Ravichandran, Ramamoorthy; Binukumar, Johnson Pichy; Davis, Cheriyathmanjiyil Antony

2013-01-01

The measured dose in water at reference point in phantom is a primary parameter for planning the treatment monitor units (MU); both in conventional and intensity modulated/image guided treatments. Traceability of dose accuracy therefore still depends mainly on the calibration factor of the ion chamber/dosimeter provided by the accredited Secondary Standard Dosimetry Laboratories (SSDLs), under International Atomic Energy Agency (IAEA) network of laboratories. The data related to Nd,water calibrations, thermoluminescent dosimetry (TLD) postal dose validation, inter-comparison of different dosimeter/electrometers, and validity of Nd,water calibrations obtained from different calibration laboratories were analyzed to find out the extent of accuracy achievable. Nd,w factors in Gray/Coulomb calibrated at IBA, GmBH, Germany showed a mean variation of about 0.2% increase per year in three Farmer chambers, in three subsequent calibrations. Another ion chamber calibrated in different accredited laboratory (PTW, Germany) showed consistent Nd,w for 9 years period. The Strontium-90 beta check source response indicated long-term stability of the ion chambers within 1% for three chambers. Results of IAEA postal TL “dose intercomparison” for three photon beams, 6 MV (two) and 15 MV (one), agreed well within our reported doses, with mean deviation of 0.03% (SD 0.87%) (n = 9). All the chamber/electrometer calibrated by a single SSDL realized absorbed doses in water within 0.13% standard deviations. However, about 1-2% differences in absorbed dose estimates observed when dosimeters calibrated from different calibration laboratories are compared in solid phantoms. Our data therefore imply that the dosimetry level maintained for clinical use of linear accelerator photon beams are within recommended levels of accuracy, and uncertainties are within reported values. PMID:24672156

Investigation of the Entrance Surface Dose and Dose to Different Organs in Lumbar Spine Imaging

PubMed Central

Sina, S; Zeinali, B; Karimipoorfard, M; Lotfalizadeh, F; Sadeghi, M; Zamani, E; Faghihi, R

2014-01-01

Background: Dose assessment using proper dosimeters is especially important in radiation protection optimization and imaging justification in diagnostic radiology. Objective: The aim of this study is to obtain the Entrance Skin Dose (ESD) of patients undergoing lumbar spine imaging using two thermoluminescence dosimeters TLD-100 (LiF: Mg, Ti) and GR-200 (LiF: Mg, Cu, P) and also to obtain the absorbed dose to different organs in lumbar spine imaging with several views. Methods: To measure the ESD values of the patients undergoing lumbar spine imaging, the two TLD types were put on their skin surface. The ESD values for different views of lumbar spine imaging were also measured by putting the TLDs at the surface of the Rando phantom. Several TLD chips were inserted inside different organs of Rando phantom to measure the absorbed dose to different organs in lumbar spine imaging. Results: The results indicate that there is a close agreement between the results of the two dosimeters. Based on the results of this experiment, the ESD dose of the 16 patients included in this study varied between 2.71 mGy and 26.29 mGy with the average of 11.89 mGy for TLD-100, and between 2.55 mGy and 27.41 mGy with the average of 12.32 mGy for GR-200 measurements. The ESDs obtained by putting the two types of TLDs at the surface of Rando phantom are in close agreement. Conclusion: According to the results, the GR200 has greater sensitivity than the TLD-100. PMID:25599058

The effect of gamma irradiation on rice protein aqueous solution

NASA Astrophysics Data System (ADS)

Baccaro, Stefania; Bal, Oya; Cemmi, Alessia; Di Sarcina, Ilaria

2018-05-01

The use of proteins as natural biopolymers are sensibly increasing in several application fields such as food industry, packaging and environment protection. In particular, rice proteins (RP) present good nutritional, hypoallergenic and healthful properties very interesting for human consumption. Since ionizing radiation can be successfully applied on protein containing systems involved in different industrial processes, this work aims to determine the effect of gamma radiation on 5 wt%-7.5 wt% RP aqueous solutions in a wide range of absorbed doses up to around 40 kGy. The changes of RP secondary and tertiary structures and their chemical composition were followed by UV-VIS absorbance spectroscopy, luminescence analysis and pH measurements. The experimental data showed the occurrence of the unfolding of RP chains with the increase of the absorbed dose and the formation of new molecules, due to the reaction among tryptophane and tyrosine amino acids and the radical species induced by gamma radiation. The results are also confirmed by the modification of the pH values measured for the irradiated solutions.

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.

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.

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.

Characteristics and issues of an EUVL mask applying phase-shifting thinner absorber for device fabrication

NASA Astrophysics Data System (ADS)

Seo, Hwan-Seok; Lee, Dong-Gun; Ahn, Byung-Sup; Han, Hakseung; Huh, Sungmin; Kang, In-Yong; Kim, Hoon; Kim, Dongwan; Kim, Seong-Sue; Cho, Han-Ku

2009-03-01

Phase-shifting EUVL masks applying thinner absorber are investigated to design optimum mask structure with less shadowing problems. Simulations using S-Litho show that H-V bias in Si capping structure is higher than that of Ru capping since the high n (= 0.999) of Si increases sensible absorber height. Phase differences obtained from the patterned masks using the EUV CSM are well-matched with the calculated values using the practical refractive index of absorber materials. Although the mask with 62.4-nm-thick absorber, among the in-house masks, shows the closest phase ΔΦ(= 176°) to the out-of-phase condition, higher NILS and contrast as well as lower H-V bias are obtained with 52.4-nm-thick absorber (ΔΦ = 151°) which has higher R/R0 ratio. MET results also show that lithography performances including MEEF, PW, and resist threshold (dose), are improved with thinner absorber structure. However, low OD in EUVL mask, especially in thinner absorber structure, results in light leakage from the neighboring exposure shots, and thus an appropriate light-shielding layer should be introduced.

Thyroid disorders in patients treated with radiotherapy for head-and-neck cancer: A retrospective analysis of seventy-three patients

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

Alterio, Daniela; Jereczek-Fossa, Barbara Alicja; University of Milan, Milan

2007-01-01

Purpose: To evaluate the incidence of thyroid disorders and dose distribution to the thyroid in patients treated with radiotherapy for head-and-neck carcinomas. Methods and Materials: A retrospective evaluation of data from 73 patients treated for head-and-neck cancers in our department was performed. Thyroid function was evaluated mainly by the measurement of thyrotropin (thyroid stimulating hormone [TSH]). A retrospective analysis of treatment plans was performed for 57 patients. Percentages of thyroid glandular volume absorbing 10, 30, and 50 Gy (V10, V30, and V50 respectively) were considered for statistical analysis. Results: A majority of patients (61%) had a normal thyroid function whereasmore » 19 patients (26%) had hypothyroidism. Mean thyroid volume was 30.39 cc. Point 3 (located at isthmus) absorbed lower doses compared with other points (p < 0.0001). Median values of V10, V30, and V50 were 92% (range, 57-100%), 75% (range, 28.5-100%), and 35% (range, 3-83%) respectively. Gender was associated with toxicity (presence of any kind of thyroid disorders) (p < 0.05), with females displaying higher levels of TSHr (relative TSH = patient's value/maximum value of the laboratory range) (p = 0.0005) and smaller thyroid volume (p 0.0012) compared with male population. TSHr values were associated with thyroid volume, and the presence of midline shielding block in the anterior field was associated with relative free thyroxine (FT4r = patient's value/maximum value of the laboratory range) values. Conclusions: Gender and thyroid volume seem to play an important role in the occurrence of thyroid toxicity, but further studies on dose-effect relationship for radiotherapy-induced thyroid toxicity are needed.« less

Fluence-to-dose conversion coefficients for heavy ions calculated using the PHITS code and the ICRP/ICRU adult reference computational phantoms.

PubMed

Sato, Tatsuhiko; Endo, Akira; Niita, Koji

2010-04-21

The fluence to organ-absorbed-dose and effective-dose conversion coefficients for heavy ions with atomic numbers up to 28 and energies from 1 MeV/nucleon to 100 GeV/nucleon were calculated using the PHITS code coupled to the ICRP/ICRU adult reference computational phantoms, following the instruction given in ICRP Publication 103 (2007 (Oxford: Pergamon)). The conversion coefficients for effective dose equivalents derived using the radiation quality factors of both Q(L) and Q(y) relationships were also estimated, utilizing the functions for calculating the probability densities of absorbed dose in terms of LET (L) and lineal energy (y), respectively, implemented in PHITS. The calculation results indicate that the effective dose can generally give a conservative estimation of the effective dose equivalent for heavy-ion exposure, although it is occasionally too conservative especially for high-energy lighter-ion irradiations. It is also found from the calculation that the conversion coefficients for the Q(y)-based effective dose equivalents are generally smaller than the corresponding Q(L)-based values because of the conceptual difference between LET and y as well as the numerical incompatibility between the Q(L) and Q(y) relationships. The calculated data of these dose conversion coefficients are very useful for the dose estimation of astronauts due to cosmic-ray exposure.

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.

[Variations of solar activity and radiation situation on board MIR station during the period 1986-1994].

PubMed

Bondarenko, V A; Mitrikas, V G; Tsetlin , V V

1995-01-01

This paper is dedicated to the analysis of the radiation situation onboard Mir station over a period of 1986-1994, there examined the main cosmophysics parameters and indices of the solar activity as well as the variations of the parameters of the earth's magnetic field and their association with the changes in the power of absorbed dose onboard the station. There noted the high levels of radiation exposure to the cosmonauts under terrestrial conditions when carrying out the roentgeno-radiologic examinations and procedures comparable or exceeding the absorbed doses during the flights. For revealing the regular associations of the radiation situation onboard the station with the parameters of solar activity there has been analyzed the time changes of average monthly values of dose power since the beginning of station functioning in 1986 until returning the fifteenth expedition to Earth. From the analyses of the results it might be assumed that the best statistical associations of average monthly power of the absorbed dose are found with the streams of protons of GCR. Wolff numbers and background stream of the radio emission of the Sun which reflects the existence of the radiation situation upon the phase of solar activity cycle. From this paper it transpires that calculating the dose loads during the period of the extreme phases of solar activity, it is possible to make between them the interpolations of time dependence by analogy with the dynamics in time of the background streams of GCR or Wolff numbers.

NOTE: Dose area product evaluations with Gafchromic® XR-R films and a flat-bed scanner

NASA Astrophysics Data System (ADS)

Rampado, O.; Garelli, E.; Deagostini, S.; Ropolo, R.

2006-12-01

Gafchromic® XR-R films are a useful tool to evaluate entrance skin dose in interventional radiology. Another dosimetric quantity of interest in diagnostic and interventional radiology is the dose area product (DAP). In this study, a method to evaluate DAP using Gafchromic® XR-R films and a flat-bed scanner was developed and tested. Film samples were exposed to an x-ray beam of 80 kVp over a dose range of 0 10 Gy. DAP measurements with films were obtained from the digitalization of a film sample positioned over the x-ray beam window during the exposure. DAP values obtained with this method were compared for 23 cardiological interventional procedures with DAP values displayed by the equipment. The overall one-sigma dose measurement uncertainty depended on the absorbed dose, with values below 6% for doses above 1 Gy. A maximum discrepancy of 16% was found, which is of the order of the differences in the DAP measurements that may occur with different calibration procedures. Based on the results presented, after an accurate calibration procedure and a thorough inspection of the relationship between the actual dose and the direct measured quantity (net optical density or net pixel value variation), Gafchromic® XR-R films can be used to assess the DAP.

A simple and fast physics-based analytical method to calculate therapeutic and stray doses from external beam, megavoltage x-ray therapy

PubMed Central

Wilson, Lydia J; Newhauser, Wayne D

2015-01-01

State-of-the-art radiotherapy treatment planning systems provide reliable estimates of the therapeutic radiation but are known to underestimate or neglect the stray radiation exposures. Most commonly, stray radiation exposures are reconstructed using empirical formulas or lookup tables. The purpose of this study was to develop the basic physics of a model capable of calculating the total absorbed dose both inside and outside of the therapeutic radiation beam for external beam photon therapy. The model was developed using measurements of total absorbed dose in a water-box phantom from a 6 MV medical linear accelerator to calculate dose profiles in both the in-plane and cross-plane direction for a variety of square field sizes and depths in water. The water-box phantom facilitated development of the basic physical aspects of the model. RMS discrepancies between measured and calculated total absorbed dose values in water were less than 9.3% for all fields studied. Computation times for 10 million dose points within a homogeneous phantom were approximately 4 minutes. These results suggest that the basic physics of the model are sufficiently simple, fast, and accurate to serve as a foundation for a variety of clinical and research applications, some of which may require that the model be extended or simplified based on the needs of the user. A potentially important advantage of a physics-based approach is that the model is more readily adaptable to a wide variety of treatment units and treatment techniques than with empirical models. PMID:26040833

A simple and fast physics-based analytical method to calculate therapeutic and stray doses from external beam, megavoltage x-ray therapy.

PubMed

Jagetic, Lydia J; Newhauser, Wayne D

2015-06-21

State-of-the-art radiotherapy treatment planning systems provide reliable estimates of the therapeutic radiation but are known to underestimate or neglect the stray radiation exposures. Most commonly, stray radiation exposures are reconstructed using empirical formulas or lookup tables. The purpose of this study was to develop the basic physics of a model capable of calculating the total absorbed dose both inside and outside of the therapeutic radiation beam for external beam photon therapy. The model was developed using measurements of total absorbed dose in a water-box phantom from a 6 MV medical linear accelerator to calculate dose profiles in both the in-plane and cross-plane direction for a variety of square field sizes and depths in water. The water-box phantom facilitated development of the basic physical aspects of the model. RMS discrepancies between measured and calculated total absorbed dose values in water were less than 9.3% for all fields studied. Computation times for 10 million dose points within a homogeneous phantom were approximately 4 min. These results suggest that the basic physics of the model are sufficiently simple, fast, and accurate to serve as a foundation for a variety of clinical and research applications, some of which may require that the model be extended or simplified based on the needs of the user. A potentially important advantage of a physics-based approach is that the model is more readily adaptable to a wide variety of treatment units and treatment techniques than with empirical models.

Radiosensitivity of Prostate Cancer Cell Lines for Irradiation from Beta Particle-emitting Radionuclide ¹⁷⁷Lu Compared to Alpha Particles and Gamma Rays.

PubMed

Elgqvist, Jörgen; Timmermand, Oskar Vilhelmsson; Larsson, Erik; Strand, Sven-Erik

2016-01-01

The purpose of the present study was to investigate the radiosensitivity of the prostate cancer cell lines LNCaP, DU145, and PC3 when irradiated with beta particles emitted from (177)Lu, and to compare the effect with irradiation using alpha particles or gamma rays. Cells were irradiated with beta particles emitted from (177)Lu, alpha particles from (241)Am, or gamma rays from (137)Cs. A non-specific polyclonal antibody was labeled with (177)Lu and used to irradiate cells in suspension with beta particles. A previously described in-house developed alpha-particle irradiator based on a (241)Am source was used to irradiate cells with alpha particles. External gamma-ray irradiation was achieved using a standard (137)Cs irradiator. Cells were irradiated to absorbed doses equal to 0, 0.5, 1, 2, 4, 6, 8, or 10 Gy. The absorbed doses were calculated as mean absorbed doses. For evaluation of cell survival, the tetrazolium-based WST-1 assay was used. After irradiation, WST-1 was added to the cell solutions, incubated, and then measured for level of absorbance at 450 nm, indicating the live and viable cells. LNCaP, DU145, and PC3 cell lines all had similar patterns of survival for the different radiation types. No significant difference in surviving fractions were observed between cells treated with beta-particle and gamma-ray irradiation, represented for example by the surviving fraction values (mean±SD) at 2, 6, and 10 Gy (SF2, SF6, and SF10) for DU145 after beta-particle irradiation: 0.700±0.090, 0.186±0.050 and 0.056±0.010, respectively. A strong radiosensitivity to alpha particles was observed, with SF2 values of 0.048±0.008, 0.018±0.006 and 0.015±0.005 for LNCaP, DU145, and PC3, respectively. The surviving fractions after irradiation using beta particles or gamma rays did not differ significantly at the absorbed dose levels and dose rates used. Irradiation using alpha particles led to a high level of cell killing. The results show that the beta-particle emitter (177)Lu as well as alpha-particles are both good candidates for radionuclide-therapy applications in the treatment of prostate cancer. Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

[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.

Radioiodine treatment of hyperthyroidism in a pregnant women.

PubMed

Berg, G E; Nyström, E H; Jacobsson, L; Lindberg, S; Lindstedt, R G; Mattsson, S; Niklasson, C A; Norén, A H; Westphal, O G

1998-02-01

We describe the effects of radioiodine treatment of a pregnant thyrotoxic woman. The woman received 500 MBq of (131)I in her 20th gestational week. The pregnancy was discovered 10 days after radioiodine administration. A gamma camera examination of the abdomen at that time showed a distinct focus of activity, which was interpreted as the fetal thyroid. Gamma camera examinations of the mother and fetus were performed at 10, 11, 12, 13 and 18 days after administration of the therapeutic activity and were the basis of dose calculations. The child was examined by hormone tests and mental performance tests, up to 8 yr after birth. The uptake at 24 hr postadministration was calculated to be 10 MBq (2%) in the fetal thyroid gland. The effective half-life was 2.5 days, giving a calculated absorbed dose to the fetal thyroid gland of 600 Gy, which is considered to be an ablative dose. The calculated absorbed dose to the fetal body, including brain, was about 100 mGy, and 40 mGy to the fetal gonads. Doses were estimated taking contributions from radioiodine in the mother, the fetal body and the fetal thyroid into consideration. The woman was encouraged to continue her pregnancy and received levothyroxine in a dose to render her slightly thyrotoxic. At full term, an apparently healthy boy, having markedly raised cord blood serum thyroid-stimulating hormone concentration and subnormal thyroxine (T4) and low-normal triiodothyronine (T3) concentrations, was born. Treatment with thyroxine was initiated from the age of 14 days, when the somatosensoric evoked potential latency time increased to a pathological value and hormonal laboratory tests repeatedly confirmed the hypothyroid state. At 8 yr of age, the child attends regular school. A neuropsychological pediatric examination showed that the mental performance was within normal limits, but with an uneven profile. He has a low attention score and displays evidently subnormal capacity regarding figurative memory. Radioiodine treatment in pregnancy in the 20th gestational week does not give a total absorbed dose to the fetal body that justifies termination of pregnancy. A high absorbed dose to the fetal thyroid, however, should be the basis of the management of the pregnancy and offspring.

[Gonad protective effect of radiation protective apron in chest radiography].

PubMed

Hashimoto, Masatoshi; Kato, Hideyuki; Fujibuchi, Toshiou; Ochi, Shigehiro; Morita, Fuminori

2004-12-01

Depending on the facility, a radiation protective apron (protector) is used to protect the gonad from radiation exposure in chest radiography. To determine the necessity of using a protector during chest radiography, we measured the effect of the protector on the gonad in this study. First, using a human body phantom, we measured the absorbed dose of the female gonad with and without the protector, using a thermoluminescence dosimeter (TLD), and confirmed its protective effect. Using the protector, the absorbed dose was reduced to 28+/-2% and 39+/-4% for field sizes of 14 x 17 inch and 14 x 14 inch, respectively. Next, we used Monte Carlo simulation and confirmed, not only the validity of the actual measurement values, but also the fact that the influence of radiation on the absorbed dose of the gonad was mostly from scattered radiation from inside the body for the 14 x 17 inch field size, and also from the X-ray tube for the 14 x 14 inch field size. Although a certain protective effect is achieved by using the protector, the radiation dose to the gonad is only a few microGy even without a protector. Thus, the risk of a genetic effect would be as small as 10(-8). Given that acceptable risk is below 10(-6), we conclude the use of a radiation protective apron is not necessary for diagnostic chest radiography.

Natural and anthropogenic radionuclides in rocks and beach sands from Ezine region (Canakkale), Western Anatolia, Turkey.

PubMed

Orgün, Y; Altinsoy, N; Sahin, S Y; Güngör, Y; Gültekin, A H; Karahan, G; Karacik, Z

2007-06-01

This paper represents the first reports on the natural and anthropogenic radionuclides in Kestanbol granitic pluton and surrounding rocks, and coastal region of the Ezine town. To assess the radiological hazard of the natural radioactivity, the radium equivalent activity, the absorbed dose rate and the external hazard index were calculated, and in situ gamma dose rates were measured. The high-activity concentrations were measured in the pluton and sands, which was originated mainly from the pluton, due to the presence of zircon, allanite, monazite, thorite, uranothorite and apatite. The average activity concentrations of (238)U, (232)Th and (40)K are 174.78, 204.69 and 1171.95 Bq kg(-1) for pluton, and 290.36, 532.04 and 1160.75 Bq kg(-1) for sands, respectively. (137)Cs in Ezine region ranged from 0-6.57 Bq kg(-1). The average absorbed dose rate for the granitic and sand samples were calculated to be 251.6 and 527.92 nGy h(-1), respectively. The maximum contribution to the total absorbed gamma dose rate in air was due to the (232)Th (52.3% for pluton and 67.1% for sands). The Raeq activities of the pluton and sands are higher than the recommended maximum value of 370 Bq kg(-1) criterion limit of Raeq activity for building materials.

A Novel Simple Phantom for Verifying the Dose of Radiation Therapy

PubMed Central

Lee, J. H.; Chang, L. T.; Shiau, A. C.; Chen, C. W.; Liao, Y. J.; Li, W. J.; Lee, M. S.; Hsu, S. M.

2015-01-01

A standard protocol of dosimetric measurements is used by the organizations responsible for verifying that the doses delivered in radiation-therapy institutions are within authorized limits. This study evaluated a self-designed simple auditing phantom for use in verifying the dose of radiation therapy; the phantom design, dose audit system, and clinical tests are described. Thermoluminescent dosimeters (TLDs) were used as postal dosimeters, and mailable phantoms were produced for use in postal audits. Correction factors are important for converting TLD readout values from phantoms into the absorbed dose in water. The phantom scatter correction factor was used to quantify the difference in the scattered dose between a solid water phantom and homemade phantoms; its value ranged from 1.084 to 1.031. The energy-dependence correction factor was used to compare the TLD readout of the unit dose irradiated by audit beam energies with 60Co in the solid water phantom; its value was 0.99 to 1.01. The setup-condition factor was used to correct for differences in dose-output calibration conditions. Clinical tests of the device calibrating the dose output revealed that the dose deviation was within 3%. Therefore, our homemade phantoms and dosimetric system can be applied for accurately verifying the doses applied in radiation-therapy institutions. PMID:25883980

In-situ intestinal rat perfusions for human Fabs prediction and BCS permeability class determination: Investigation of the single-pass vs. the Doluisio experimental approaches.

PubMed

Lozoya-Agullo, Isabel; Zur, Moran; Wolk, Omri; Beig, Avital; González-Álvarez, Isabel; González-Álvarez, Marta; Merino-Sanjuán, Matilde; Bermejo, Marival; Dahan, Arik

2015-03-01

Intestinal drug permeability has been recognized as a critical determinant of the fraction dose absorbed, with direct influence on bioavailability, bioequivalence and biowaiver. The purpose of this research was to compare intestinal permeability values obtained by two different intestinal rat perfusion methods: the single-pass intestinal perfusion (SPIP) model and the Doluisio (closed-loop) rat perfusion method. A list of 15 model drugs with different permeability characteristics (low, moderate, and high, as well as passively and actively absorbed) was constructed. We assessed the rat intestinal permeability of these 15 model drugs in both SPIP and the Doluisio methods, and evaluated the correlation between them. We then evaluated the ability of each of these methods to predict the fraction dose absorbed (Fabs) in humans, and to assign the correct BCS permeability class membership. Excellent correlation was obtained between the two experimental methods (r(2)=0.93). An excellent correlation was also shown between literature Fabs values and the predictions made by both rat perfusion techniques. Similar BCS permeability class membership was designated by literature data and by both SPIP and Doluisio methods for all compounds. In conclusion, the SPIP model and the Doluisio (closed-loop) rat perfusion method are both equally useful for obtaining intestinal permeability values that can be used for Fabs prediction and BCS classification. Copyright © 2015 Elsevier B.V. All rights reserved.

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

PubMed

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

2018-04-05

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

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

NASA Astrophysics Data System (ADS)

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

2018-04-01

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

Health risk profile for terrestrial radionuclides in soil around artisanal gold mining area at Alsopag, Sudan

NASA Astrophysics Data System (ADS)

Idriss, Hajo; Salih, Isam; Alaamer, Abdulaziz S.; AL-Rajhi, M. A.; Osman, Alshfia; Adreani, Tahir Elamin; Abdelgalil, M. Y.; Ali, Nagi I.

2018-06-01

This study shows the assessment of radiation hazard parameters due to terrestrial radionuclides in the soil around artisanal gold mining for addressing the issue of natural radioactivity in mining areas. Hence, the levels 238U, 232Th, 40K and 226Ra in soil (using gamma spectrometry), 222Rn in soil and 222Rn in air were determined. Radiation hazard parameters were then computed. These include absorbed dose D, annual effective dose E, radium equivalent activity Raeq, external hazard H ex, annual gonadal dose equivalent hazard index AGDE and excess lifetime cancer risk ELCR due to the inhalation of radon (222Rn) and consumption of radium (226Ra) in vegetation. Uranium (238U), thorium (232Th) and potassium (40K) averages were, respectively, 26, 36 and 685 Becquerel per kilogram (Bq kg-1). Soil radon (4671 Bq m-3) and radon in air (14.77 Bq m-3) were found to be less than worldwide data. Nevertheless, the average 40K concentration was 685 Bq kg-1. This is slightly higher than the United Nations Scientific Committee on the Effects of Atomic Radiation average value of 412 Bq kg-1. The obtained result indicates that some of the radiation hazard parameters seem unsavory. The mean value of absorbed dose rate (62.49 nGy h-1) was slightly higher than average value of 57 nGy h-1 ( 45% from 40K), and that of AGDE (444 μSv year-1) was higher than worldwide average reported value (300 μSv year-1). This study highlights the necessity to launch extensive nationwide radiation protection program in the mining areas for regulatory control.

RESPONSE OF THE GREEK EARLY WARNING SYSTEM REUTER-STOKES IONIZATION CHAMBERS TO TERRESTRIAL AND COSMIC RADIATION EVALUATED IN COMPARISON WITH SPECTROSCOPIC DATA AND TIME SERIES ANALYSIS.

PubMed

Leontaris, F; Clouvas, A; Xanthos, S; Maltezos, A; Potiriadis, C; Kiriakopoulos, E; Guilhot, J

2018-02-01

The Telemetric Early Warning System Network of the Greek Atomic Energy Commission consists mainly of a network of 24 Reuter-Stokes high-pressure ionization chambers (HPIC) for gamma dose rate measurements and covers all Greece. In the present work, the response of the Reuter-Stokes HPIC to terrestrial and cosmic radiation was evaluated in comparison with spectroscopic data obtained by in situ gamma spectrometry measurements with portable hyper pure Germanium detectors (HPGe), near the Reuter-Stokes detectors and time series analysis. For the HPIC detectors, a conversion factor for the measured absorbed dose rate in air (in nGy h-1) to the total ambient dose equivalent rate Ḣ*(10), due to terrestrial and cosmic component, was deduced by the field measurements. Time series analysis of the mean monthly dose rate (measured by the Reuter-Stokes detector in Thessaloniki, northern Greece, from 2001 to 2016) was performed with advanced statistical methods (Fast Fourier Analysis and Zhao Atlas Marks Transform). Fourier analysis reveals several periodicities (periodogram). The periodogram of the absorbed dose rate in air values was compared with the periodogram of the values measured for the same period (2001-16) and in the same location with a NaI (Tl) detector which in principle is not sensitive to cosmic radiation. The obtained results are presented and discussed. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Comparison of the IAEA TRS-398 and AAPM TG-51 absorbed dose to water protocols in the dosimetry of high-energy photon and electron beams

NASA Astrophysics Data System (ADS)

Saiful Huq, M.; Andreo, Pedro; Song, Haijun

2001-11-01

The International Atomic Energy Agency (IAEA TRS-398) and the American Association of Physicists in Medicine (AAPM TG-51) have published new protocols for the calibration of radiotherapy beams. These protocols are based on the use of an ionization chamber calibrated in terms of absorbed dose to water in a standards laboratory's reference quality beam. This paper compares the recommendations of the two protocols in two ways: (i) by analysing in detail the differences in the basic data included in the two protocols for photon and electron beam dosimetry and (ii) by performing measurements in clinical photon and electron beams and determining the absorbed dose to water following the recommendations of the two protocols. Measurements were made with two Farmer-type ionization chambers and three plane-parallel ionization chamber types in 6, 18 and 25 MV photon beams and 6, 8, 10, 12, 15 and 18 MeV electron beams. The Farmer-type chambers used were NE 2571 and PTW 30001, and the plane-parallel chambers were a Scanditronix-Wellhöfer NACP and Roos, and a PTW Markus chamber. For photon beams, the measured ratios TG-51/TRS-398 of absorbed dose to water Dw ranged between 0.997 and 1.001, with a mean value of 0.999. The ratios for the beam quality correction factors kQ were found to agree to within about +/-0.2% despite significant differences in the method of beam quality specification for photon beams and in the basic data entering into kQ. For electron beams, dose measurements were made using direct ND,w calibrations of cylindrical and plane-parallel chambers in a 60Co gamma-ray beam, as well as cross-calibrations of plane-parallel chambers in a high-energy electron beam. For the direct ND,w calibrations the ratios TG-51/TRS-398 of absorbed dose to water Dw were found to lie between 0.994 and 1.018 depending upon the chamber and electron beam energy used, with mean values of 0.996, 1.006, and 1.017, respectively, for the cylindrical, well-guarded and not well-guarded plane-parallel chambers. The Dw ratios measured for the cross-calibration procedures varied between 0.993 and 0.997. The largest discrepancies for electron beams between the two protocols arise from the use of different data for the perturbation correction factors pwall and pdis of cylindrical and plane-parallel chambers, all in 60Co. A detailed analysis of the reasons for the discrepancies is made which includes comparing the formalisms, correction factors and the quantities in the two protocols.

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.

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.

Research on radiation exposure from CT part of hybrid camera and diagnostic CT

NASA Astrophysics Data System (ADS)

Solný, Pavel; Zimák, Jaroslav

2014-11-01

Research on radiation exposure from CT part of hybrid camera in seven different Departments of Nuclear Medicine (DNM) was conducted. Processed data and effective dose (E) estimations led to the idea of phantom verification and comparison of absorbed doses and software estimation. Anonymous data from about 100 examinations from each DNM was gathered. Acquired data was processed and utilized by dose estimation programs (ExPACT, ImPACT, ImpactDose) with respect to the type of examination and examination procedures. Individual effective doses were calculated using enlisted programs. Preserving the same procedure in dose estimation process allows us to compare the resulting E. Some differences and disproportions during dose estimation led to the idea of estimated E verification. Consequently, two different sets of about 100 of TLD 100H detectors were calibrated for measurement inside the Aldersnon RANDO Anthropomorphic Phantom. Standard examination protocols were examined using a 2 Slice CT- part of hybrid SPECT/CT. Moreover, phantom exposure from body examining protocol for 32 Slice and 64 Slice diagnostic CT scanner was also verified. Absorbed dose (DT,R) measured using TLD detectors was compared with software estimation of equivalent dose HT values, computed by E estimation software. Though, only limited number of cavities for detectors enabled measurement within the regions of lung, liver, thyroid and spleen-pancreas region, some basic comparison is possible.

[Characterization of a diode system for in vivo dosimetry with electron beams].

PubMed

Ragona, R; Rossetti, V; Lucio, F; Anglesio, S; Giglioli, F R

2001-10-01

Current quality assurance regulation stresses the basic role of in vivo dosimetry. Our study evaluates the usefulness and reliability of semiconductor diodes in determining the electron absorbed dose. P-type EDE semiconductor detectors were irradiated with electron beams of different energies produced by a CGR Saturn Therac 20. The diode and ionization chamber response were compared, and effect of energy value, collimator opening, source skin distance and gantry angle on diode response was studied. Measurements show a maximum increment of about 20% in diode response increasing the beam energy (6-20 MeV). The response also increases with: collimator opening, reaching 5% with field sizes larger than 10x10 cm2 (with the exception of 20 MeV energy); SSD increase (with a maximum of 8% for 20 MeV); transversal gantry incidence, compared with the diode longitudinal axis; it does not affect the response in the interval of +/- 45 degrees. Absorbed dose attenuation at dmax, due to the presence of diode on the axis of the beam as a function of electron energy was also determined : the maximum attenuation value is 15% in 6 MeV electron beams. A dose calculation algorithm, taking into account diode response dependence was outlined. In vivo dosimetry was performed in 92 fields for 80 patients, with an agreement of +/-4 % (1 SD) between prescribed and measured dose. It is possible to use the EDE semiconductor detectors on a quality control program of dose delivery for electron beam therapy, but particular attention should be paid to the beam incidence angle and diode dose attenuation.

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

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.

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.

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.

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

Evaluating health risks from occupational exposure to pesticides and the regulatory response.

PubMed Central

Woodruff, T J; Kyle, A D; Bois, F Y

1994-01-01

In this study, we used measurements of occupational exposures to pesticides in agriculture to evaluate health risks and analyzed how the federal regulatory program is addressing these risks. Dose estimates developed by the State of California from measured occupational exposures to 41 pesticides were compared to standard indices of acute toxicity (LD50) and chronic effects (reference dose). Lifetime cancer risks were estimated using cancer potencies. Estimated absorbed daily doses for mixers, loaders, and applicators of pesticides ranged from less than 0.0001% to 48% of the estimated human LD50 values, and doses for 10 of 40 pesticides exceeded 1% of the estimated human LD50 values. Estimated lifetime absorbed daily doses ranged from 0.1% to 114,000% of the reference doses developed by the U.S. Environmental Protection Agency, and doses for 13 of 25 pesticides were above them. Lifetime cancer risks ranged from 1 per million to 1700 per million, and estimates for 12 of 13 pesticides were above 1 per million. Similar results were obtained for field workers and flaggers. For the pesticides examined, exposures pose greater risks of chronic effects than acute effects. Exposure reduction measures, including use of closed mixing systems and personal protective equipment, significantly reduced exposures. Proposed regulations rely primarily on requirements for personal protective equipment and use restrictions to protect workers. Chronic health risks are not considered in setting these requirements. Reviews of pesticides by the federal pesticide regulatory program have had little effect on occupational risks. Policy strategies that offer immediate protection for workers and that are not dependent on extensive review of individual pesticides should be pursued. Images Figure 1. PMID:7713022

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.

WE-D-17A-06: Optically Stimulated Luminescence Detectors as ‘LET-Meters’ in Proton Beams

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

Granville, D; Sahoo, N; Sawakuchi, GO

Purpose: To demonstrate and evaluate the potential of optically stimulated luminescence (OSL) detectors (OSLDs) for measurements of linear energy transfer (LET) in therapeutic proton beams. Methods: Batches of Al2O2:C OSLDs were irradiated with an absorbed dose of 0.2 Gy in un-modulated proton beams of varying LET (0.67 keV/μm to 2.58 keV/μm). The OSLDs were read using continuous wave (CW-OSL) and pulsed (P-OSL) stimulation modes. We parameterized and calibrated three characteristics of the OSL signals as functions of LET: CW-OSL curve shape, P-OSL curve shape and the ratio of the two OSL emission band intensities (ultraviolet/blue ratio). Calibration curves were createdmore » for each of these characteristics to describe their behaviors as functions of LET. The true LET values were determined using a validated Monte Carlo model of the proton therapy nozzle used to irradiate the OSLDs. We then irradiated batches of OSLDs with an absorbed dose of 0.2 Gy at various depths in two modulated proton beams (140 MeV, 4 cm wide spread-out Bragg peak (SOBP) and 250 MeV, 10 cm wide SOBP). The LET values were calculated using the OSL response and the calibration curves. Finally, measured LET values were compared to the true values determined using Monte Carlo simulations. Results: The CW-OSL curve shape, P-OSL curve shape and the ultraviolet/blue-ratio provided proton LET estimates within 12.4%, 5.7% and 30.9% of the true values, respectively. Conclusion: We have demonstrated that LET can be measured within 5.7% using Al2O3:C OSLDs in the therapeutic proton beams used in this investigation. From a single OSLD readout, it is possible to measure both the absorbed dose and LET. This has potential future applications in proton therapy quality assurance, particularly for treatment plans based on optimization of LET distributions. This research was partially supported by the Natural Sciences and Engineering Research Council of Canada.« 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.

Theoretical study of the influence of a heterogeneous activity distribution on intratumoral absorbed dose distribution.

PubMed

Bao, Ande; Zhao, Xia; Phillips, William T; Woolley, F Ross; Otto, Randal A; Goins, Beth; Hevezi, James M

2005-01-01

Radioimmunotherapy of hematopoeitic cancers and micrometastases has been shown to have significant therapeutic benefit. The treatment of solid tumors with radionuclide therapy has been less successful. Previous investigations of intratumoral activity distribution and studies on intratumoral drug delivery suggest that a probable reason for the disappointing results in solid tumor treatment is nonuniform intratumoral distribution coupled with restricted intratumoral drug penetrance, thus inhibiting antineoplastic agents from reaching the tumor's center. This paper describes a nonuniform intratumoral activity distribution identified by limited radiolabeled tracer diffusion from tumor surface to tumor center. This activity was simulated using techniques that allowed the absorbed dose distributions to be estimated using different intratumoral diffusion capabilities and calculated for tumors of varying diameters. The influences of these absorbed dose distributions on solid tumor radionuclide therapy are also discussed. The absorbed dose distribution was calculated using the dose point kernel method that provided for the application of a three-dimensional (3D) convolution between a dose rate kernel function and an activity distribution function. These functions were incorporated into 3D matrices with voxels measuring 0.10 x 0.10 x 0.10 mm3. At this point fast Fourier transform (FFT) and multiplication in frequency domain followed by inverse FFT (iFFT) were used to effect this phase of the dose calculation process. The absorbed dose distribution for tumors of 1, 3, 5, 10, and 15 mm in diameter were studied. Using the therapeutic radionuclides of 131I, 186Re, 188Re, and 90Y, the total average dose, center dose, and surface dose for each of the different tumor diameters were reported. The absorbed dose in the nearby normal tissue was also evaluated. When the tumor diameters exceed 15 mm, a much lower tumor center dose is delivered compared with tumors between 3 and 5 mm in diameter. Based on these findings, the use of higher beta-energy radionuclides, such as 188Re and 90Y is more effective in delivering a higher absorbed dose to the tumor center at tumor diameters around 10 mm.

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

NASA Astrophysics Data System (ADS)

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

2003-08-01

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

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.

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).

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.

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.

Radiodine therapy of the autonomous thyroid nodule in patients with or without visible extranodular activity

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

Clerc, J.; Dagousset, F.; Izembart, M.

1995-02-01

Patients with an autonomously functioning throid nodule (ATN) may present with various clinical, biochemical and scintigraphic features. To optimize 1 dose planning and treatment timing in these patients, relationships between dosimetric data and clinical follow-up events must be established. The authors retrospectively reviewed the records of 88 patients who received 1 (intended dose of 80 Gy) for an ATN, of whom 39 had evidence of extranodular activity (ENA) and 76 presented with overt thyrotoxicosis. In all of the patients, dosage calculation was monitored to estimate precisely both beta and gamma absorbed doses received by the ATN and the nodule-free lobe.more » The mean duration of follow-up was 75 mo (max 180) and always included biochemical thyroid tests. Finally, they compared the dosimetric profiles of four dosage schemes which had been normalized by simulation to ensure that the same absorbed dose threshold value was always delivered to the ATN. About 75% of the patients were cured at 6 mo for a mean 305 MBq administered. The absorbed doses delivered to the nodule-free lobe to the ATN, mainly in the form of beta irradiation. Life-table estimates for hypothyroidism and death were 9.6% and 22% at 75 mo, respectively. Hypothyroidism mainly developed in patients with nonsuppressed TSH levels but regardless of ENA, which often accounted for multifocal disease. The authors suggest that fixed doses bordering on 370 MBq are advisable in younger individuals and in patients with mild thyrotoxocosis, while 555 MBq-740 MBq can be administered in other patients and that ENA indicates multifocal autonomy in patients with toxic ATN and is a further indication for radioiodine treatment which should be begun as soon as possible to avoid the development of cardiac complications. 27 refs., 5 tabs.« less

Response functions for computing absorbed dose to skeletal tissues from photon irradiation—an update

NASA Astrophysics Data System (ADS)

Johnson, Perry B.; Bahadori, Amir A.; Eckerman, Keith F.; Lee, Choonsik; Bolch, Wesley E.

2011-04-01

A comprehensive set of photon fluence-to-dose response functions (DRFs) is presented for two radiosensitive skeletal tissues—active and total shallow marrow—within 15 and 32 bone sites, respectively, of the ICRP reference adult male. The functions were developed using fractional skeletal masses and associated electron-absorbed fractions as reported for the UF hybrid adult male phantom, which in turn is based upon micro-CT images of trabecular spongiosa taken from a 40 year male cadaver. The new DRFs expand upon both the original set of seven functions produced in 1985, and a 2007 update calculated under the assumption of secondary electron escape from spongiosa. In this study, it is assumed that photon irradiation of the skeleton will yield charged particle equilibrium across all spongiosa regions at energies exceeding 200 keV. Kerma coefficients for active marrow, inactive marrow, trabecular bone and spongiosa at higher energies are calculated using the DRF algorithm setting the electron-absorbed fraction for self-irradiation to unity. By comparing kerma coefficients and DRF functions, dose enhancement factors and mass energy-absorption coefficient (MEAC) ratios for active marrow to spongiosa were derived. These MEAC ratios compared well with those provided by the NIST Physical Reference Data Library (mean difference of 0.8%), and the dose enhancement factors for active marrow compared favorably with values calculated in the well-known study published by King and Spiers (1985 Br. J. Radiol. 58 345-56) (mean absolute difference of 1.9 percentage points). Additionally, dose enhancement factors for active marrow were shown to correlate well with the shallow marrow volume fraction (R2 = 0.91). Dose enhancement factors for the total shallow marrow were also calculated for 32 bone sites representing the first such derivation for this target tissue.

Response functions for computing absorbed dose to skeletal tissues from photon irradiation--an update.

PubMed

Johnson, Perry B; Bahadori, Amir A; Eckerman, Keith F; Lee, Choonsik; Bolch, Wesley E

2011-04-21

A comprehensive set of photon fluence-to-dose response functions (DRFs) is presented for two radiosensitive skeletal tissues-active and total shallow marrow-within 15 and 32 bone sites, respectively, of the ICRP reference adult male. The functions were developed using fractional skeletal masses and associated electron-absorbed fractions as reported for the UF hybrid adult male phantom, which in turn is based upon micro-CT images of trabecular spongiosa taken from a 40 year male cadaver. The new DRFs expand upon both the original set of seven functions produced in 1985, and a 2007 update calculated under the assumption of secondary electron escape from spongiosa. In this study, it is assumed that photon irradiation of the skeleton will yield charged particle equilibrium across all spongiosa regions at energies exceeding 200 keV. Kerma coefficients for active marrow, inactive marrow, trabecular bone and spongiosa at higher energies are calculated using the DRF algorithm setting the electron-absorbed fraction for self-irradiation to unity. By comparing kerma coefficients and DRF functions, dose enhancement factors and mass energy-absorption coefficient (MEAC) ratios for active marrow to spongiosa were derived. These MEAC ratios compared well with those provided by the NIST Physical Reference Data Library (mean difference of 0.8%), and the dose enhancement factors for active marrow compared favorably with values calculated in the well-known study published by King and Spiers (1985 Br. J. Radiol. 58 345-56) (mean absolute difference of 1.9 percentage points). Additionally, dose enhancement factors for active marrow were shown to correlate well with the shallow marrow volume fraction (R(2) = 0.91). Dose enhancement factors for the total shallow marrow were also calculated for 32 bone sites representing the first such derivation for this target tissue.

RESPONSE FUNCTIONS FOR COMPUTING ABSORBED DOSE TO SKELETAL TISSUES FROM PHOTON IRRADIATION – AN UPDATE

PubMed Central

Johnson, Perry; Bahadori, Amir; Eckerman, Keith; Lee, Choonsik; Bolch, Wesley E.

2014-01-01

A comprehensive set of photon fluence-to-dose response functions (DRFs) are presented for two radiosensitive skeletal tissues – active and total shallow marrow – within 15 and 32 bones sites, respectively, of the ICRP reference adult male. The functions were developed using fractional skeletal masses and associated electron absorbed fractions as reported for the UF hybrid adult male phantom, which in turn is based upon microCT images of trabecular spongiosa taken from a 40-year male cadaver. The new DRFs expand upon both the original set of seven functions produced in 1985, as well as a 2007 update calculated under the assumption of secondary electron escape from spongiosa. In the present study, it is assumed that photon irradiation of the skeleton will yield charged particle equilibrium across all spongiosa regions at energies exceeding 200 keV. Kerma factors for active marrow, inactive marrow, trabecular bone, and spongiosa at higher energies are calculated using the DRF algorithm setting the electron absorbed fraction for self-irradiation to unity. By comparing kerma factors and DRF functions, dose enhancement factors and mass energy-absorption coefficient (MEAC) ratios for active marrow to spongiosa were derived. These MEAC ratios compared well with those provided by the NIST Physical Reference Data Library (mean difference of 0.8%), and the dose enhancement factors for active marrow compared favorably with values calculated in the well-known study published by King and Spiers (1985) (mean absolute difference of 1.9 percentage points). Additionally, dose enhancement factors for active marrow were shown to correlate well with the shallow marrow volume fraction (R2 = 0.91). Dose enhancement factors for the total shallow marrow were also calculated for 32 bone sites PMID:21427484

Cell engineering: nanometric grafting of poly-N-isopropylacrylamide onto polystyrene film by different doses of gamma radiation

PubMed Central

Biazar, Esmaeil; Zeinali, Reza; Montazeri, Naser; Pourshamsian, Khalil; Behrouz, Mahmoud Jabarvand; Asefnejad, Azadeh; Khoshzaban, Ahad; Shahhosseini, Gholamreza; Najafabadi, Mostafa Soleimannejad; Abyani, Reza; Jamalzadeh, Hamidreza; Fouladi, Mahdi; Hagh, Sasan Rahbar F; Khamaneh, Aylar Shams; Kabiri, Soudabeh; Keshel, Saeed Heidari; Mansourkiaei, Ana

2010-01-01

Poly-N-isopropylacrylamide was successfully grafted onto a polystyrene cell culture dish and γ-preirradiated in air. In this study, the effect of a γ-pre-irradiation dose of radiation (radiation absorbed dosages of 10, 20, 30, 40 KGy) under appropriate temperature and grafting conditions was investigated. The Fourier transform infrared spectroscopy analysis showed the existence of the graft poly-N-isopropylacrylamide (PNIPAAm) on the substrate. The optimal value of the dose for grafting was 40 KGy at 50°C. The scanning electron microscopy and atomic force microscopy (AFM) images clearly showed that increasing the absorbed dose of radiation would increase the amount of grafting. Surface topography and graft thickness in AFM images of the radiated samples showed that the PNIPAAm at the absorbed dose of radiation was properly grafted. The thickness of these grafts was about 50–100 nm. The drop water contact angles of the best grafted sample at 37°C and 10°C were 55.3 ± 1.2° and 61.2 ± 0.9° respectively, which showed the hydrophilicity and hydrophobicity of the grafted surfaces. Differential scanning calorimetry analysis also revealed the low critical solution temperature of the grafted sample to be 32°C. Thermoresponsive polymers were grafted to dishes covalently which allowed fibroblast cells to attach and proliferate at 37°C; the cells also detached spontaneously without using enzymes when the temperature dropped below 32°C. This characteristic proves that this type of grafted material has potential as a biomaterial for cell sheet engineering. PMID:20957116

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

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

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.

An EGSnrc Monte Carlo study of the microionization chamber for reference dosimetry of narrow irregular IMRT beamlets.

PubMed

Capote, Roberto; Sánchez-Doblado, Francisco; Leal, Antonio; Lagares, Juan Ignacio; Arráns, Rafael; Hartmann, Günther H

2004-09-01

Intensity modulated radiation therapy (IMRT) has evolved toward the use of many small radiation fields, or "beamlets," to increase the resolution of the intensity map. The size of smaller beamlets can be typically about 1-5 cm2. Therefore small ionization chambers (IC) with sensitive volumes < or = 0.1 cm3 are generally used for dose verification of IMRT treatment. The dosimetry of these narrow photon beams pertains to the so-called nonreference conditions for beam calibration. The use of ion chambers for such narrow beams remains questionable due to the lack of electron equilibrium in most of the field. The present contribution aims to estimate, by the Monte Carlo (MC) method, the total correction needed to convert the IBA-Wellhöfer NAC007 micro IC measured charge in such radiation field to the absolute dose to water. Detailed geometrical simulation of the microionization chamber was performed. The ion chamber was always positioned at a 10 cm depth in water, parallel to the beam axis. The delivered doses to air and water cavity were calculated using the CAVRZ EGSnrc user code. The 6 MV phase-spaces for Primus Clinac (Siemens) used as an input to the CAVRZnrc code were derived by BEAM/EGS4 modeling of the treatment head of the machine along with the multileaf collimator [Sánchez-Doblado et al., Phys. Med. Biol. 48, 2081-2099 (2003)] and contrasted with experimental measurements. Dose calculations were carried out for two irradiation geometries, namely, the reference 10x10 cm2 field and an irregular (approximately 2x2 cm2) IMRT beamlet. The dose measured by the ion chamber is estimated by MC simulation as a dose averaged over the air cavity inside the ion-chamber (Dair). The absorbed dose to water is derived as the dose deposited inside the same volume, in the same geometrical position, filled and surrounded by water (Dwater) in the absence of the ionization chamber. Therefore, the Dwater/Dair dose ratio is a MC direct estimation of the total correction factor needed to convert the absorbed dose in air to absorbed dose to water. The dose ratio was calculated for several chamber positions, starting from the penumbra region around the beamlet along the two diagonals crossing the radiation field. For this quantity from 0 up to a 3% difference is observed between the dose ratio values obtained within the small irregular IMRT beamlet in comparison with the dose ratio derived for the reference 10x10 cm2 field. Greater differences from the reference value up to 9% were obtained in the penumbra region of the small IMRT beamlet.

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.

Dual-energy computed tomography of the head: a phantom study assessing axial dose distribution, eye lens dose, and image noise level

NASA Astrophysics Data System (ADS)

Matsubara, Kosuke; Kawashima, Hiroki; Hamaguchi, Takashi; Takata, Tadanori; Kobayashi, Masanao; Ichikawa, Katsuhiro; Koshida, Kichiro

2016-03-01

The aim of this study was to propose a calibration method for small dosimeters to measure absorbed doses during dual- source dual-energy computed tomography (DECT) and to compare the axial dose distribution, eye lens dose, and image noise level between DE and standard, single-energy (SE) head CT angiography. Three DE (100/Sn140 kVp 80/Sn140 kVp, and 140/80 kVp) and one SE (120 kVp) acquisitions were performed using a second-generation dual-source CT device and a female head phantom, with an equivalent volumetric CT dose index. The axial absorbed dose distribution at the orbital level and the absorbed doses for the eye lens were measured using radiophotoluminescent glass dosimeters. CT attenuation numbers were obtained in the DE composite images and the SE images of the phantom at the orbital level. The doses absorbed at the orbital level and in the eye lens were lower and standard deviations for the CT attenuation numbers were slightly higher in the DE acquisitions than those in the SE acquisition. The anterior surface dose was especially higher in the SE acquisition than that in the DE acquisitions. Thus, DE head CT angiography can be performed with a radiation dose lower than that required for a standard SE head CT angiography, with a slight increase in the image noise level. The 100/Sn140 kVp acquisition revealed the most balanced axial dose distribution. In addition, our proposed method was effective for calibrating small dosimeters to measure absorbed doses in DECT.

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

Reconstruction of Absorbed Doses to Fibroglandular Tissue of the Breast of Women undergoing Mammography (1960 to the Present)

PubMed Central

Thierry-Chef, Isabelle; Simon, Steven L.; Weinstock, Robert M.; Kwon, Deukwoo; Linet, Martha S.

2013-01-01

The assessment of potential benefits versus harms from mammographic examinations as described in the controversial breast cancer screening recommendations of the U.S. Preventive Task Force included limited consideration of absorbed dose to the fibroglandular tissue of the breast (glandular tissue dose), the tissue at risk for breast cancer. Epidemiological studies on cancer risks associated with diagnostic radiological examinations often lack accurate information on glandular tissue dose, and there is a clear need for better estimates of these doses. Our objective was to develop a quantitative summary of glandular tissue doses from mammography by considering sources of variation over time in key parameters including imaging protocols, x-ray target materials, voltage, filtration, incident air kerma, compressed breast thickness, and breast composition. We estimated the minimum, maximum, and mean values for glandular tissue dose for populations of exposed women within 5-year periods from 1960 to the present, with the minimum to maximum range likely including 90% to 95% of the entirety of the dose range from mammography in North America and Europe. Glandular tissue dose from a single view in mammography is presently about 2 mGy, about one-sixth the dose in the 1960s. The ratio of our estimates of maximum to minimum glandular tissue doses for average-size breasts was about 100 in the 1960s compared to a ratio of about 5 in recent years. Findings from our analysis provide quantitative information on glandular tissue doses from mammographic examinations which can be used in epidemiologic studies of breast cancer. PMID:21988547

Alternative chitosan-based EPR dosimeter applicable for a relatively wide range of gamma radiation doses

NASA Astrophysics Data System (ADS)

Piroonpan, Thananchai; Katemake, Pichayada; Panritdam, Eagkapong; Pasanphan, Wanvimol

2017-12-01

Chitosan biopolymer is proposed as an alternative EPR dosimeter. Its ability to be EPR dosimeter was studied in comparison with the conventional alanine, sugars (i.e., glucose and sucrose), formate derivatives (i.e., lithium (Li), magnesium (Mg), and calcium (Ca) formate). Ethylene vinyl acetate (EVA) and paraffin were used as binder for the preparation of composite EPR dosimeter. Dose responses of all materials were investigated in a wide dose range of radiation doses, i.e., low-level (0-1 kGy), medium-level (1-10 kGy) and high-level (10-100 kGy). The EPR dosimeter properties were studied under different parameters, i.e., microwave power, materials contents, absorbed doses, storage conditions and post-irradiation effects. Li-formate showed a simple EPR spectrum and exhibited superior radiation response for low-dose range; whereas chitosan and sucrose exhibited linear dose response in all studied dose ranges. The EPR signals of chitosan exhibited similar stability as glucose, Li-formate and alanine at ambient temperature after irradiation as long as a year. All EPR signals of the studied materials were affected post-irradiation temperature and humidity after gamma irradiation. The EPR signal of chitosan exhibited long-term stability and it was not sensitive to high storage temperatures and humidity values after irradiation. Chitosan has a good merit as the alternative bio-based material for a stable EPR dosimeter in a wide range of radiation-absorbed doses.

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

PubMed

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

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

RESPONSE FUNCTIONS FOR COMPUTING ABSORBED DOSE TO SKELETAL TISSUES FROM NEUTRON IRRADIATION

PubMed Central

Bahadori, Amir A.; Johnson, Perry; Jokisch, Derek W.; Eckerman, Keith F.; Bolch, Wesley E.

2016-01-01

Spongiosa in the adult human skeleton consists of three tissues - active marrow (AM), inactive marrow (IM), and trabecularized mineral bone (TB). Active marrow is considered to be the target tissue for assessment of both long-term leukemia risk and acute marrow toxicity following radiation exposure. The total shallow marrow (TM50), defined as all tissues laying within the first 50 μm the bone surfaces, is considered to be the radiation target tissue of relevance for radiogenic bone cancer induction. For irradiation by sources external to the body, kerma to homogeneous spongiosa has been used as a surrogate for absorbed dose to both of these tissues, as direct dose calculations are not possible using computational phantoms with homogenized spongiosa. Recent microCT imaging of a 40-year-old male cadaver has allowed for the accurate modeling of the fine microscopic structure of spongiosa in many regions of the adult skeleton [Hough et al PMB (2011)]. This microstructure, along with associated masses and tissue compositions, was used to compute specific absorbed fractions (SAF) values for protons originating in axial and appendicular bone sites [Jokisch et al PMB (submitted)]. These proton SAFs, bone masses, tissue compositions, and proton production cross-sections, were subsequently used to construct neutron dose response functions (DRFs) for both AM and TM50 targets in each bone of the reference adult male. Kerma conditions were assumed for other resultant charged particles. For comparison, active marrow, total shallow marrow, and spongiosa kerma coefficients were also calculated. At low incident neutron energies, AM kerma coefficients for neutrons correlate well with values of the AM DRF, while total marrow (TM) kerma coefficients correlate well with values of the TM50 DRF. At high incident neutron energies, all kerma coefficients and DRFs tend to converge as charged particle equilibrium (CPE) is established across the bone site. In the range of 10 eV to 100 MeV, substantial differences are observed among the kerma coefficients and DRF. As a result, it is recommended that the AM kerma coefficient be used to estimate the AM DRF, and that the TM kerma coefficient be used to estimate the TM50 DRF below 10 eV. Between 10 eV and 100 MeV, the appropriate DRF should be used as presented in this study. Above 100 MeV, spongiosa kerma coefficients apply well for estimating skeletal tissue doses. DRF values for each bone site as a function of energy are provided in an electronic annex to this article. PMID:21983525

[ESTIMATION OF IONIZING RADIATION EFFECTIVE DOSES IN THE INTERNATIONAL SPACE STATION CREWS BY THE METHOD OF CALCULATION MODELING].

PubMed

Mitrikas, V G

2015-01-01

Monitoring of the radiation loading on cosmonauts requires calculation of absorbed dose dynamics with regard to the stay of cosmonauts in specific compartments of the space vehicle that differ in shielding properties and lack means of radiation measurement. The paper discusses different aspects of calculation modeling of radiation effects on human body organs and tissues and reviews the effective dose estimates for cosmonauts working in one or another compartment over the previous period of the International space station operation. It was demonstrated that doses measured by a real or personal dosimeters can be used to calculate effective dose values. Correct estimation of accumulated effective dose can be ensured by consideration for time course of the space radiation quality factor.

Monte Carlo calculations of electron beam quality conversion factors for several ion chamber types.

PubMed

Muir, B R; Rogers, D W O

2014-11-01

To provide a comprehensive investigation of electron beam reference dosimetry using Monte Carlo simulations of the response of 10 plane-parallel and 18 cylindrical ion chamber types. Specific emphasis is placed on the determination of the optimal shift of the chambers' effective point of measurement (EPOM) and beam quality conversion factors. The EGSnrc system is used for calculations of the absorbed dose to gas in ion chamber models and the absorbed dose to water as a function of depth in a water phantom on which cobalt-60 and several electron beam source models are incident. The optimal EPOM shifts of the ion chambers are determined by comparing calculations of R50 converted from I50 (calculated using ion chamber simulations in phantom) to R50 calculated using simulations of the absorbed dose to water vs depth in water. Beam quality conversion factors are determined as the calculated ratio of the absorbed dose to water to the absorbed dose to air in the ion chamber at the reference depth in a cobalt-60 beam to that in electron beams. For most plane-parallel chambers, the optimal EPOM shift is inside of the active cavity but different from the shift determined with water-equivalent scaling of the front window of the chamber. These optimal shifts for plane-parallel chambers also reduce the scatter of beam quality conversion factors, kQ, as a function of R50. The optimal shift of cylindrical chambers is found to be less than the 0.5 rcav recommended by current dosimetry protocols. In most cases, the values of the optimal shift are close to 0.3 rcav. Values of kecal are calculated and compared to those from the TG-51 protocol and differences are explained using accurate individual correction factors for a subset of ion chambers investigated. High-precision fits to beam quality conversion factors normalized to unity in a beam with R50 = 7.5 cm (kQ (')) are provided. These factors avoid the use of gradient correction factors as used in the TG-51 protocol although a chamber dependent optimal shift in the EPOM is required when using plane-parallel chambers while no shift is needed with cylindrical chambers. The sensitivity of these results to parameters used to model the ion chambers is discussed and the uncertainty related to the practical use of these results is evaluated. These results will prove useful as electron beam reference dosimetry protocols are being updated. The analysis of this work indicates that cylindrical ion chambers may be appropriate for use in low-energy electron beams but measurements are required to characterize their use in these beams.

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.

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.

A dosimetry study comparing NCS report-5, IAEA TRS-381, AAPM TG-51 and IAEA TRS-398 in three clinical electron beam energies

NASA Astrophysics Data System (ADS)

Palmans, Hugo; Nafaa, Laila; de Patoul, Nathalie; Denis, Jean-Marc; Tomsej, Milan; Vynckier, Stefaan

2003-05-01

New codes of practice for reference dosimetry in clinical high-energy photon and electron beams have been published recently, to replace the air kerma based codes of practice that have determined the dosimetry of these beams for the past twenty years. In the present work, we compared dosimetry based on the two most widespread absorbed dose based recommendations (AAPM TG-51 and IAEA TRS-398) with two air kerma based recommendations (NCS report-5 and IAEA TRS-381). Measurements were performed in three clinical electron beam energies using two NE2571-type cylindrical chambers, two Markus-type plane-parallel chambers and two NACP-02-type plane-parallel chambers. Dosimetry based on direct calibrations of all chambers in 60Co was investigated, as well as dosimetry based on cross-calibrations of plane-parallel chambers against a cylindrical chamber in a high-energy electron beam. Furthermore, 60Co perturbation factors for plane-parallel chambers were derived. It is shown that the use of 60Co calibration factors could result in deviations of more than 2% for plane-parallel chambers between the old and new codes of practice, whereas the use of cross-calibration factors, which is the first recommendation in the new codes, reduces the differences to less than 0.8% for all situations investigated here. The results thus show that neither the chamber-to-chamber variations, nor the obtained absolute dose values are significantly altered by changing from air kerma based dosimetry to absorbed dose based dosimetry when using calibration factors obtained from the Laboratory for Standard Dosimetry, Ghent, Belgium. The values of the 60Co perturbation factor for plane-parallel chambers (katt . km for the air kerma based and pwall for the absorbed dose based codes of practice) that are obtained from comparing the results based on 60Co calibrations and cross-calibrations are within the experimental uncertainties in agreement with the results from other investigators.

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.

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

Analysis of the Body Distribution of Absorbed Dose in the Organs of Three Species of Fish from Sepetiba Bay

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 body distribution of Polonium-210 in three fishes from the Sepetiba Bay (Macrodon ancylodon, Micropogonias furnieri and Mugil curema) has been studied under the approach of the Department of Energy of the United States of America (DOE) that set the limit of absorbed dose rate in biota equal to 3.5x10{sup 3} {mu}Gy/y, and that also established the relation between dose rate (D) and radionuclide concentration (c) on a fish muscle fresh weight basis, as follows: D = 5.05 ExNxC, assuming that the radionuclide distribution is homogenous among organs. Two hypotheses were tested here, using statistical tools: 1) is the bodymore » distribution of absorbed dose homogenous among organs? and 2) is the body distribution of absorbed dose identical among studied fishes? It was concluded, as expected, that the distribution among organs is heterogeneous; but, unexpectedly, that the three fishes display identical body distribution pattern, although they belong to different trophic levels. Hence, concerning absorbed dose calculation, the statement that data distribution is homogenous must be understood merely as an approximation, at least in the case of Polonium-210.« less

SU-F-19A-06: Experimental Investigation of the Energy Dependence of TLD Sensitivity in Low-Energy Photon Beams

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

Chen, Z; Nath, R

Purpose: To measure the energy dependence of TLD sensitivity in lowenergy photon beams with equivalent mono-energetic energy matching those of 103Pd, 125I and 131Cs brachytherapy sources. Methods: A Pantek DXT 300 x-ray unit (Precision X-ray, Branford, CT), with stable digital voltage control down to 20 kV, was used to establish three lowenergy photon beams with narrow energy spread and equivalent monoenergetic energies matching those of 103Pd, 125I and 131Cs brachytherapy sources. The low-energy x-ray beams and a reference 6 MV photon beam were calibrated according to the AAPM TG-61 and TG-51 protocols, respectively, using a parallel-plate low-energy chamber and amore » Farmer cylindrical chamber with NIST traceable calibration factors. The dose response of model TLD-100 micro-cubes (1×1×1 mm{sup 3}) in each beam was measured for five different batches of TLDs (each contained approximately 100 TLDs) that have different histories of irradiation and usage. Relative absorbed dose sensitivity was determined as the quotient of the slope of dose response for a beam-of-interest to that of the reference beam. Results: Equivalent mono-energetic photon energies of the low-energy beams established for 103Pd, 125I and 131Cs sources were 20.5, 27.5, and 30.1 keV, respectively. Each beam exhibited narrow spectral spread with energyhomogeneity index close to 90%. The relative absorbed-dose sensitivity was found to vary between different batches of TLD with maximum differences of up to 8%. The mean and standard deviation determined from the five TLD batches was 1.453 ± 0.026, 1.541 ± 0.035 and 1.529 ± 0.051 for the simulated 103P, 125I and 131Cs beams, respectively. Conclusion: Our measured relative absorbed-dose sensitivities are greater than the historically measured value of 1.41. We find that the relative absorbed-dose sensitivity of TLD in the 103P beam is approximately 5% lower than that of 125I and 131Cs beams. Comparison of our results with other studies will be presented.« less

Absorption of ethanol, acetone, benzene and 1,2-dichloroethane through human skin in vitro: a test of diffusion model predictions

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

Gajjar, Rachna M.; Kasting, Gerald B., E-mail: Gerald.Kasting@uc.edu

The overall goal of this research was to further develop and improve an existing skin diffusion model by experimentally confirming the predicted absorption rates of topically-applied volatile organic compounds (VOCs) based on their physicochemical properties, the skin surface temperature, and the wind velocity. In vitro human skin permeation of two hydrophilic solvents (acetone and ethanol) and two lipophilic solvents (benzene and 1,2-dichloroethane) was studied in Franz cells placed in a fume hood. Four doses of each {sup 14}C-radiolabed compound were tested — 5, 10, 20, and 40 μL cm{sup −2}, corresponding to specific doses ranging in mass from 5.0 tomore » 63 mg cm{sup −2}. The maximum percentage of radiolabel absorbed into the receptor solutions for all test conditions was 0.3%. Although the absolute absorption of each solvent increased with dose, percentage absorption decreased. This decrease was consistent with the concept of a stratum corneum deposition region, which traps small amounts of solvent in the upper skin layers, decreasing the evaporation rate. The diffusion model satisfactorily described the cumulative absorption of ethanol; however, values for the other VOCs were underpredicted in a manner related to their ability to disrupt or solubilize skin lipids. In order to more closely describe the permeation data, significant increases in the stratum corneum/water partition coefficients, K{sub sc}, and modest changes to the diffusion coefficients, D{sub sc}, were required. The analysis provided strong evidence for both skin swelling and barrier disruption by VOCs, even by the minute amounts absorbed under these in vitro test conditions. - Highlights: • Human skin absorption of small doses of VOCs was measured in vitro in a fume hood. • The VOCs tested were ethanol, acetone, benzene and 1,2-dichloroethane. • Fraction of dose absorbed for all compounds at all doses tested was less than 0.3%. • The more aggressive VOCs absorbed at higher levels than diffusion model predictions. • We conclude that even small exposures to VOCs temporarily alter skin permeability.« less

RADIOLOGICAL IMPACTS ASSESSMENT FOR WORKERS IN CERAMIC INDUSTRY IN SERBIA.

PubMed

Todorovic, Nataša; Mrda, Dušan; Hansman, Jan; Todorovic, Slavko; Nikolov, Jovana; Krmar, Miodrag

2017-11-01

Studies have been carried out to determine the natural radioactivity in some materials used in ceramic industry (zircon, zirkosil, Zircobit MO/S, zircon silicate, zirklonil frit, hematite, bentonite, wollastonite, raw kaolin, kaolinized granite, sileks ball, feldspar, pigment, white base serigraphic, engobe) and their associated radiation hazard. The external hazard index, Hex, values, radium equivalent activity, Raeq, total absorbed dose rates, D and annual effective dose, De were derived for all measured materials and compared with the recommended values to assess the external radiation hazards to workers who worked in ceramic industries in Serbia. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

A safety radiation marker in the cardiac catheterization lab.

PubMed

Kostakou, Peggy M; Damaskos, Dimitris S; Dagre, Anna G; Makavos, Georgios A; Olympios, Christophoros D

2016-04-01

Nowadays, in order to deal with cardiovascular disease, coronary angiography (CRA) is the best tool and gold standard for diagnosis and assessment. CRA inevitably exposes both patient and operator to radiation. The purpose of this study was to calculate the radiation exposure in association with the radiation absorbed by interventional cardiologists, in order to estimate a safety radiation marker in the catheterization laboratory. In 794 successive patients undergoing CRA and in three interventional cardiologists the following parameters were examined: radioscopy duration, radiation exposure during fluoroscopy, total radiation exposure and the number of stents per procedure. Every interventional cardiologist was exposed to 562,936 μGym2 of total radiation during CRA procedures, to 833,371 μGym2 during elective CRA + percutaneous coronary intervention (PCI) procedures and to 328,250 μGym2 during primary CRA + PCI. Hence, the total amount of radiation that every angiographer was exposed to amounted to 1,724,557.5 μGym2 (median values). During the same period, the average radiation that every angiographer absorbed was 15,253 while the average dose of radiation absorbed during one procedure was 0.06 mSv for each operator. Therefore, the ratio between radiation exposure and the radiation finally absorbed by every operator was 113:1 μGym2/mSv. The present study, indicating the ratio above, offers a safety marker in order to realistically estimate the dose absorbed by interventional cardiologists, suggesting a specified number of permitted procedures and an effective level of radiation use protection tools.

RADIOLOGICAL HAZARD INDICES OF GRANITIC ROCKS USED FOR THE CONSTRUCTION OF BUILDINGS FROM NUBA MOUNTAINS SUDAN.

PubMed

Fadol, Nooreldin; Idriss, Hajo; Salih, Isam; Ragab, Nserdin A; Osman, Safa; Sam, Adam K

2018-06-01

This study was conducted to assess the level of radioactivity and the radiation hazards associated with granite rocks used for construction of buildings. The measurement of radioactivity content of the rock samples was performed with gamma-spectrometry equipped with Nal (TI) detector. From the results obtained in this study the average activity concentrations of 226Ra, 232Th and 40K were 20.64, 30.50 and 295.19 Bq kg-1, respectively. The absorbed dose rate in air at 1 m above ground level, the annual effective dose and the gamma index were determined with the aim to assess the possible radiological impact on inhabitants of dwellings built using such rocks. The mean value of the absorbed dose rate, the annual effective dose and the gamma index (Iγ) was 36.36 nGy h-1, 40.79 μSv y-1 and 0.51 μSv y-1, respectively. Radium equivalent activities, and external and internal hazard indices, were also calculated. These data indicated that the area of study lies within areas recognized as normal background radiation and the granite rocks are safe to be used as building material and other structural purposes.

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.

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

Does the lead apron and collar always reduce radiation dose?

PubMed

Nortje, C J; Harris, A M; Lackovic, K P; Wood, R E

2001-11-01

The possibility that personal lead shielding devices can increase absorption of radiation has not been entertained. The purpose of the present investigation specifically was to determine whether pituitary dose might be increased when a leaded apron and thyroid collar are used. Thermoluminescent dosimeters (TLDs) were used to measure absorbed dose. They were calibrated at the kVp used in the clinical situation and a calibration curve relating light output to dose was generated. Lithium fluoride TLD discs were placed in the pituitary gland region of a Rando-Alderson female human phantom. The equivalent of 100 transpharyngeal exposures were delivered. The resultant light output from recovered dosimeters was converted to a uGy value using the calibration curve. The experiment was repeated using a 0.25 mm lead equivalent collar and apron fitted to the phantom in the customary manner. The entire process was repeated in order to have 30 dosimeters for the unshielded and 30 dosimeters for the shielded conditions. A further 30 dosimeters were sham irradiated and served as controls. A statistical comparison between unshielded and shielded conditions was performed. When the leaded apron and thyroid collar were used the absorbed dose to the pituitary gland was increased significantly (P < 0.05). Following this a second group, using a different dosimetry system and a male phantom repeated the experiment. In both cases, the shielded phantom received significantly higher dose to the pituitary region than the unshielded.

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.

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

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.

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...

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.

On the need for quality assurance in superficial kilovoltage radiotherapy.

PubMed

Austerlitz, C; Mota, H; Gay, H; Campos, D; Allison, R; Sibata, C

2008-01-01

External auditing of beam output and energy qualities of four therapeutic X-ray machines were performed in three radiation oncology centres in northeastern Brazil. The output and half-value layers (HVLs) were determined using a parallel-plate ionisation chamber and high-purity aluminium foils, respectively. The obtained values of absorbed dose to water and energy qualities were compared with those obtained by the respective institutions. The impact on the prescribed dose was analysed by determining the half-value depth (D(1/2)). The beam outputs presented percent differences ranging from -13 to +25%. The ratio between the HVL in use by the institution and the measurements obtained in this study ranged from 0.75 to 2.33. Such deviations in HVL result in percent differences in dose at D(1/2) ranging from -52 to +8%. It was concluded that dosimetric quality audit programmes in radiation therapy should be expanded to include dermatological radiation therapy and such audits should include HVL verification.

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.

Study of a non-diffusing radiochromic gel dosimeter for 3D radiation dose imaging

NASA Astrophysics Data System (ADS)

Marsden, Craig Michael

2000-12-01

This thesis investigates the potential of a new radiation gel dosimeter, based on nitro-blue tetrazolium (NBTZ) suspended in a gelatin mold. Unlike all Fricke based gel dosimeters this dosimeter does not suffer from diffusive loss of image stability. Images are obtained by an optical tomography method. Nitro blue tetrazolium is a common biological indicator that when irradiated in an aqueous medium undergoes reduction to a highly colored formazan, which has an absorbance maximum at 525nm. Tetrazolium is water soluble while the formazan product is insoluble. The formazan product sticks to the gelatin matrix and the dose image is maintained for three months. Methods to maximize the sensitivity of the system were evaluated. It was found that a chemical detergent, Triton X-100, in combination with sodium formate, increased the dosimeter sensitivity significantly. An initial G-value of formazan production for a dosimeter composed of 1mM NBTZ, gelatin, and water was on the order of 0.2. The addition of Triton and formate produced a G-value in excess of 5.0. The effects of NBTZ, triton, formate, and gel concentration were all investigated. All the gels provided linear dose vs. absorbance plots for doses from 0 to >100 Gy. It was determined that gel concentration had minimal if any effect on sensitivity. Sensitivity increased slightly with increasing NBTZ concentration. Triton and formate individually and together provided moderate to large increases in dosimeter sensitivity. The dosimeter described in this work can provide stable 3D radiation dose images for all modalities of radiation therapy equipment. Methods to increase sensitivity are developed and discussed.

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

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.

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

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

Tsuji, S; Oita, M; Narihiro, N

2016-06-15

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

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.

NATURAL RADIOACTIVITY IN SEDIMENTS AND RIVER BANK SOIL OF KALLADA RIVER OF KERALA, SOUTH INDIA AND ASSOCIATED RADIOLOGICAL RISK.

PubMed

Venunathan, N; Kaliprasad, C S; Narayana, Y

2016-10-01

The paper presents the activity concentrations of 232 Th, 226 Ra and 40 K in the sediments and river bank soil samples collected from the Kallada river environs of coastal Kerala. The radiological risks associated with these radionuclides were calculated. The samples were processed following standard procedure, and activity was counted using a high-efficiency 5″ × 5″ NaI (Tl) detector coupled to GSPEC gamma spectroscopy system. The mean values of measured activities of 232 Th, 226 Ra and 40 K in soil samples were found to be 98.1 ± 0.4, 60.3 ± 1.1 and 343.4 ± 1.8 Bq kg -1 , respectively, which results in an average absorbed dose rate of 103 nGy h -1 The corresponding values for sediment samples were found to be 88.0 ± 0.4, 48.6 ± 0.9 and 423.2 ± 2.0 Bq kg -1 , respectively, with a resulting absorbed dose rate of 95 nGy h -1 Radium equivalent activity, annual effective dose equivalent, the external and internal hazard indices were determined and compared with recommended limits. The results of the work provide background data on natural radioactive isotopes, which are useful in the assessment of human radiation exposure from natural environment. The accumulation of information on natural radiation is of great value for radiation protection. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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.

An organ-based approach to dose calculation in the assessment of dose-dependent biological effects of ionising radiation in Arabidopsis thaliana.

PubMed

Biermans, Geert; Horemans, Nele; Vanhoudt, Nathalie; Vandenhove, Hildegarde; Saenen, Eline; Van Hees, May; Wannijn, Jean; Vives i Batlle, Jordi; Cuypers, Ann

2014-07-01

There is a need for a better understanding of biological effects of radiation exposure in non-human biota. Correct description of these effects requires a more detailed model of dosimetry than that available in current risk assessment tools, particularly for plants. In this paper, we propose a simple model for dose calculations in roots and shoots of Arabidopsis thaliana seedlings exposed to radionuclides in a hydroponic exposure setup. This model is used to compare absorbed doses for three radionuclides, (241)Am (α-radiation), (90)Sr (β-radiation) and (133)Ba (γ radiation). Using established dosimetric calculation methods, dose conversion coefficient values were determined for each organ separately based on uptake data from the different plant organs. These calculations were then compared to the DCC values obtained with the ERICA tool under equivalent geometry assumptions. When comparing with our new method, the ERICA tool appears to overestimate internal doses and underestimate external doses in the roots for all three radionuclides, though each to a different extent. These observations might help to refine dose-response relationships. The DCC values for (90)Sr in roots are shown to deviate the most. A dose-effect curve for (90)Sr β-radiation has been established on biomass and photosynthesis endpoints, but no significant dose-dependent effects are observed. This indicates the need for use of endpoints at the molecular and physiological scale. Copyright © 2013 Elsevier Ltd. All rights reserved.

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

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.

Optimization strategies for radiation induced grafting of 4-vinylpyridine onto poly(ethylene-co-tetraflouroethene) film using Box-Behnken design

NASA Astrophysics Data System (ADS)

Mahmoud Nasef, Mohamed; Shamsaei, Ezzatollah; Ghassemi, Payman; Ahmed Aly, Amgad; Hamid Yahaya, Abdul

2012-04-01

The radiation induced grafting of 4-vinylpyridine (4-VP) onto poly(ethylene-co-tetrafluoroethene) (ETFE) was optimized using the Box-Behnken factorial design available in the response surface method (RSM). The optimized grafting parameters; absorbed dose, monomer concentration, grafting time and reaction temperature were varied in four levels to quantify their effect on the grafting yield (GY). The validity of the statistical model was supported by the small deviation between the predicted (GY=61%) and experimental (GY=57%) values. The optimum conditions for enhancing GY were determined at the following values: monomer concentration of 48 vol%, absorbed dose of 64 kGy, reaction time of 4 h and temperature of 68 °C. A comparison was made between the optimization model developed for the present grafting system and that for grafting of 1-vinylimidazole (1-VIm) onto ETFE to confirm the validly and reliability of the Box-Behnken for the optimization of various radiation induced grafting reactions. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD) were used to investigate the properties of the obtained films and provide evidence for grafting.

Radiation Effect on Human Tissue

NASA Technical Reports Server (NTRS)

Richmond, Robert C.; Cruz, Angela; Bors, Karen; Curreri, Peter A. (Technical Monitor)

2002-01-01

Predicting the occurrence of human cancer following exposure of an epidemiologic population to any agent causing genetic damage is a difficult task. To an approximation, this is because the uncertainty of uniform exposure to the damaging agent, and the uncertainty of uniform processing of that damage within a complex set of biological variables, degrade the confidence of predicting the delayed expression of cancer as a relatively rare event within clinically normal individuals. This situation begs the need for alternate controlled experimental models that are predictive for the development of human cancer following exposures to agents causing genetic damage. Such models historically have not been of substantial proven value. It is more recently encouraging, however, that developments in molecular and cell biology have led to an expanded knowledge of human carcinogenesis, and of molecular markers associated with that process. It is therefore appropriate to consider new laboratory models developed to accomodate that expanded knowledge in order to assess the cancer risks associated with exposures to genotoxic agents. When ionizing radiation of space is the genotoxic agent, then a series of additional considerations for human cancer risk assessment must also be applied. These include the dose of radiation absorbed by tissue at different locations in the body, the quality of the absorbed radiation, the rate at which absorbed dose accumulates in tissue, the way in which absorbed dose is measured and calculated, and the alterations in incident radiation caused by shielding materials. It is clear that human cancer risk assessment for damage caused by ionizing radiation is a multidisciplinary responsibility, and that within this responsibility no single discipline can hold disproportionate sway if a risk assessment model of radiation-induced human cancer is to be developed that has proven value. Biomolecular and cellular markers from the work reported here are considered for use in assessing human cancer risk related to exposure to space radiation. This potential use must be integrated within the specified multidisciplinary context in order to create a new tool of molecular epidemiology that can hopefully then realistically assess this cancer risk.

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

PubMed

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

2018-05-19

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

Natural radioactivity investigation in Dam sediments of northeast Algeria using gamma spectroscopy

NASA Astrophysics Data System (ADS)

Benrachi, Fatima; Bouhila, Ghania; Saadi, Asma; Ramdhane, Mourad

2017-09-01

Current research paper intends to estimate the natural radioactivity levels in sediments samples collected from Beni Haroun Dam in the northeast Algeria, using high resolution HPGe detector. The mean activity concentrations values measured for the radionuclides 232Th, 226Ra and 40K are 18.9 ± 1.9, 37.3 ± 2.7 and 149.9 ± 5.5 Bq/kg, respectively. The 137Cs anthropogenic radionuclide has been observed with maximum activity concentration value of 0.8 ± 0.4 Bq/kg, which is considered an insignificant amount. In order to assess the radiological threat of gamma radiations emitted by these radionuclides on the health of the population, absorbed dose rate, annual effective dose equivalent and radiation hazard indices were had been calculated. The obtained values are compared with the world wide average ones.

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.

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.

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.

Photon-Fluence-Weighted let for Radiation Fields Subjected to Epidemiological Studies.

PubMed

Sasaki, Michiya

2017-08-01

In order to estimate the uncertainty of the radiation risk associated with the photon energy in epidemiological studies, photon-fluence-weighted LET values were quantified for photon radiation fields with the target organs and irradiation conditions taken into consideration. The photon fluences giving a unit absorbed dose to the target organ were estimated by using photon energy spectra together with the dose conversion coefficients given in ICRP Publication 116 for the target organs of the colon, bone marrow, stomach, lung, skin and breast with three irradiation geometries. As a result, it was demonstrated that the weighted LET values did not show a clear difference among the photon radiation fields subjected to epidemiological studies, regardless of the target organ and the irradiation geometry.

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.

COMPILATION OF CONVERSION COEFFICIENTS FOR THE DOSE TO THE LENS OF THE EYE

PubMed Central

2017-01-01

Abstract A compilation of fluence-to-absorbed dose conversion coefficients for the dose to the lens of the eye is presented. The compilation consists of both previously published data and newly calculated values: photon data (5 keV–50 MeV for both kerma approximation and full electron transport), electron data (10 keV–50 MeV), and positron data (1 keV–50 MeV) – neutron data will be published separately. Values are given for angles of incidence from 0° up to 90° in steps of 15° and for rotational irradiation. The data presented can be downloaded from this article's website and they are ready for use by Report Committee (RC) 26. This committee has been set up by the International Commission on Radiation Units and Measurements (ICRU) and is working on a ‘proposal for a redefinition of the operational quantities for external radiation exposure’. PMID:27542816

Evaluation of the effect of low tube voltage on radiation dose and image quality

NASA Astrophysics Data System (ADS)

Norhasrina Nik Din, Nik; Zainon, Rafidah; Rahman, A. T. Abdul

2017-05-01

Number of Computed Tomography (CT) examinations performed worldwide is increasing. In 2010, the FDA issued an initiative to reduce unnecessary radiation exposure from CT imaging. The aim of this study is to evaluate the effect of low tube voltage on radiation dose and image quality using CTDI phantom. The CTDI phantom was scanned with dual energy CT at 80 kV and 120 kV with the tube current from 150 mAs to 350 mAs. Pitch was 1.0 while slice thickness was 1 mm and 5 mm. Results show if mAs was increased, the SNR values also will be increased. The 5 mm slice thickness shows higher SNR value compared to 1 mm slice thickness. As the voltage and tube current increased, the amount of dose absorbed is also increased because current is proportional to photon flux.

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

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.

Fluence-to-absorbed-dose conversion coefficients for neutron beams from 0.001 eV to 100 GeV calculated for a set of pregnant female and fetus models

NASA Astrophysics Data System (ADS)

Taranenko, Valery; Xu, X. George

2008-03-01

Protection of fetuses against external neutron exposure is an important task. This paper reports a set of absorbed dose conversion coefficients for fetal and maternal organs for external neutron beams using the RPI-P pregnant female models and the MCNPX code. The newly developed pregnant female models represent an adult female with a fetus including its brain and skeleton at the end of each trimester. The organ masses were adjusted to match the reference values within 1%. For the 3 mm cubic voxel size, the models consist of 10-15 million voxels for 35 organs. External monoenergetic neutron beams of six standard configurations (AP, PA, LLAT, RLAT, ROT and ISO) and source energies 0.001 eV-100 GeV were considered. The results are compared with previous data that are based on simplified anatomical models. The differences in dose depend on source geometry, energy and gestation periods: from 20% up to 140% for the whole fetus, and up to 100% for the fetal brain. Anatomical differences are primarily responsible for the discrepancies in the organ doses. For the first time, the dependence of mother organ doses upon anatomical changes during pregnancy was studied. A maximum of 220% increase in dose was observed for the placenta in the nine months model compared to three months, whereas dose to the pancreas, small and large intestines decreases by 60% for the AP source for the same models. Tabulated dose conversion coefficients for the fetus and 27 maternal organs are provided.

Response functions for computing absorbed dose to skeletal tissues from neutron irradiation

NASA Astrophysics Data System (ADS)

Bahadori, Amir A.; Johnson, Perry; Jokisch, Derek W.; Eckerman, Keith F.; Bolch, Wesley E.

2011-11-01

Spongiosa in the adult human skeleton consists of three tissues—active marrow (AM), inactive marrow (IM) and trabecularized mineral bone (TB). AM is considered to be the target tissue for assessment of both long-term leukemia risk and acute marrow toxicity following radiation exposure. The total shallow marrow (TM50), defined as all tissues lying within the first 50 µm of the bone surfaces, is considered to be the radiation target tissue of relevance for radiogenic bone cancer induction. For irradiation by sources external to the body, kerma to homogeneous spongiosa has been used as a surrogate for absorbed dose to both of these tissues, as direct dose calculations are not possible using computational phantoms with homogenized spongiosa. Recent micro-CT imaging of a 40 year old male cadaver has allowed for the accurate modeling of the fine microscopic structure of spongiosa in many regions of the adult skeleton (Hough et al 2011 Phys. Med. Biol. 56 2309-46). This microstructure, along with associated masses and tissue compositions, was used to compute specific absorbed fraction (SAF) values for protons originating in axial and appendicular bone sites (Jokisch et al 2011 Phys. Med. Biol. 56 6857-72). These proton SAFs, bone masses, tissue compositions and proton production cross sections, were subsequently used to construct neutron dose-response functions (DRFs) for both AM and TM50 targets in each bone of the reference adult male. Kerma conditions were assumed for other resultant charged particles. For comparison, AM, TM50 and spongiosa kerma coefficients were also calculated. At low incident neutron energies, AM kerma coefficients for neutrons correlate well with values of the AM DRF, while total marrow (TM) kerma coefficients correlate well with values of the TM50 DRF. At high incident neutron energies, all kerma coefficients and DRFs tend to converge as charged-particle equilibrium is established across the bone site. In the range of 10 eV to 100 MeV, substantial differences are observed among the kerma coefficients and DRF. As a result, it is recommended that the AM kerma coefficient be used to estimate the AM DRF, and that the TM kerma coefficient be used to estimate the TM50 DRF below 10 eV. Between 10 eV and 100 MeV, the appropriate DRF should be used as presented in this study. Above 100 MeV, spongiosa kerma coefficients apply well for estimating skeletal tissue doses. DRF values for each bone site as a function of energy are provided in an electronic annex to this article available at http://stacks.iop.org/0031-9155/56/6873/mmedia.

Response functions for computing absorbed dose to skeletal tissues from neutron irradiation.

PubMed

Bahadori, Amir A; Johnson, Perry; Jokisch, Derek W; Eckerman, Keith F; Bolch, Wesley E

2011-11-07

Spongiosa in the adult human skeleton consists of three tissues-active marrow (AM), inactive marrow (IM) and trabecularized mineral bone (TB). AM is considered to be the target tissue for assessment of both long-term leukemia risk and acute marrow toxicity following radiation exposure. The total shallow marrow (TM(50)), defined as all tissues lying within the first 50 µm of the bone surfaces, is considered to be the radiation target tissue of relevance for radiogenic bone cancer induction. For irradiation by sources external to the body, kerma to homogeneous spongiosa has been used as a surrogate for absorbed dose to both of these tissues, as direct dose calculations are not possible using computational phantoms with homogenized spongiosa. Recent micro-CT imaging of a 40 year old male cadaver has allowed for the accurate modeling of the fine microscopic structure of spongiosa in many regions of the adult skeleton (Hough et al 2011 Phys. Med. Biol. 56 2309-46). This microstructure, along with associated masses and tissue compositions, was used to compute specific absorbed fraction (SAF) values for protons originating in axial and appendicular bone sites (Jokisch et al 2011 Phys. Med. Biol. 56 6857-72). These proton SAFs, bone masses, tissue compositions and proton production cross sections, were subsequently used to construct neutron dose-response functions (DRFs) for both AM and TM(50) targets in each bone of the reference adult male. Kerma conditions were assumed for other resultant charged particles. For comparison, AM, TM(50) and spongiosa kerma coefficients were also calculated. At low incident neutron energies, AM kerma coefficients for neutrons correlate well with values of the AM DRF, while total marrow (TM) kerma coefficients correlate well with values of the TM(50) DRF. At high incident neutron energies, all kerma coefficients and DRFs tend to converge as charged-particle equilibrium is established across the bone site. In the range of 10 eV to 100 MeV, substantial differences are observed among the kerma coefficients and DRF. As a result, it is recommended that the AM kerma coefficient be used to estimate the AM DRF, and that the TM kerma coefficient be used to estimate the TM(50) DRF below 10 eV. Between 10 eV and 100 MeV, the appropriate DRF should be used as presented in this study. Above 100 MeV, spongiosa kerma coefficients apply well for estimating skeletal tissue doses. DRF values for each bone site as a function of energy are provided in an electronic annex to this article available at http://stacks.iop.org/0031-9155/56/6873/mmedia.

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

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.

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

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

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

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.

RECONSTRUCTION OF INDIVIDUAL DOSES DUE TO MEDICAL EXPOSURES FOR MEMBERS OF THE TECHA RIVER COHORT

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

Shagina, N. B.; Golikov, V.; Degteva, M. O.

Purpose: To describe a methodology for reconstruction of doses due to medical exposures for members of the Techa River Cohort (TRC) who received diagnostic radiation at the clinic of the Urals Research Center for Radiation Medicine (URCRM) in 1952–2005. To calculate doses of medical exposure for the TRC members and compare with the doses that resulted from radioactive contamination of the Techa River. Material and Methods: Reconstruction of individual medical doses is based on data on x-ray diagnostic procedures available for each person examined at the URCRM clinics and values of absorbed dose in 12 organs per typical x-ray proceduremore » calculated with the use of a mathematical phantom. Personal data on x-ray diagnostic examinations have been complied in the computerized “Registry of x-ray diagnostic procedures.” Sources of information are archival registry books from the URCRM x-ray room (available since 1956) and records on x-ray diagnostic procedures in patient-case histories (since 1952). The absorbed doses for 12 organs of interest have been evaluated per unit typical x-ray procedure with account taken of the x-ray examination parameters characteristic for the diagnostic machines used at the URCRM clinics. These parameters have been evaluated from published data on technical characteristics of the x-ray diagnostic machines used at the URCRM clinics in 1952–1988 and taken from the x-ray room for machines used at the URCRM in 1989–2005. Absorbed doses in the 12 organs per unit typical x-ray procedure have been calculated with use of a special computer code, EDEREX, developed at the Saint-Petersburg Research Institute of Radiation Hygiene after Professor P.V. Ramzaev. Individual accumulated doses of medical exposure have been calculated with a computer code, MEDS (Medical Exposure Dosimetry System), specifically developed at the URCRM. Results: At present, the “Registry of x-ray diagnostic procedures” contains information on individual x-ray examinations for over 9,500 persons including 6,415 TRC members. Statistical analysis of the Registry data showed that the more frequent types of examinations were fluoroscopy and radiography of the chest and fluoroscopy of the stomach and the esophagus. Average absorbed doses accumulated by year 2005 calculated for the 12 organs varied from 4 mGy for testes to 40 mGy for bone surfaces. Maximum individual medical doses could reach 500–650 mGy and in some cases exceeded doses from exposure at the Techa River. Conclusions: For the first time the doses of medical exposure were calculated and analyzed for members of the Techa River Cohort who received diagnostic radiation at the URCRM clinics. These results are being used in radiation-risk analysis to adjust for this source of confounding exposure in the TRC.« less

Methodology comparison for gamma-heating calculations in material-testing reactors

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

Lemaire, M.; Vaglio-Gaudard, C.; Lyoussi, A.

2015-07-01

The Jules Horowitz Reactor (JHR) is a Material-Testing Reactor (MTR) under construction in the south of France at CEA Cadarache (French Alternative Energies and Atomic Energy Commission). It will typically host about 20 simultaneous irradiation experiments in the core and in the beryllium reflector. These experiments will help us better understand the complex phenomena occurring during the accelerated ageing of materials and the irradiation of nuclear fuels. Gamma heating, i.e. photon energy deposition, is mainly responsible for temperature rise in non-fuelled zones of nuclear reactors, including JHR internal structures and irradiation devices. As temperature is a key parameter for physicalmore » models describing the behavior of material, accurate control of temperature, and hence gamma heating, is required in irradiation devices and samples in order to perform an advanced suitable analysis of future experimental results. From a broader point of view, JHR global attractiveness as a MTR depends on its ability to monitor experimental parameters with high accuracy, including gamma heating. Strict control of temperature levels is also necessary in terms of safety. As JHR structures are warmed up by gamma heating, they must be appropriately cooled down to prevent creep deformation or melting. Cooling-power sizing is based on calculated levels of gamma heating in the JHR. Due to these safety concerns, accurate calculation of gamma heating with well-controlled bias and associated uncertainty as low as possible is all the more important. There are two main kinds of calculation bias: bias coming from nuclear data on the one hand and bias coming from physical approximations assumed by computer codes and by general calculation route on the other hand. The former must be determined by comparison between calculation and experimental data; the latter by calculation comparisons between codes and between methodologies. In this presentation, we focus on this latter kind of bias. Nuclear heating is represented by the physical quantity called absorbed dose (energy deposition induced by particle-matter interactions, divided by mass). Its calculation with Monte Carlo codes is possible but computationally expensive as it requires transport simulation of charged particles, along with neutrons and photons. For that reason, the calculation of another physical quantity, called KERMA, is often preferred, as KERMA calculation with Monte Carlo codes only requires transport of neutral particles. However, KERMA is only an estimator of the absorbed dose and many conditions must be fulfilled for KERMA to be equal to absorbed dose, including so-called condition of electronic equilibrium. Also, Monte Carlo computations of absorbed dose still present some physical approximations, even though there is only a limited number of them. Some of these approximations are linked to the way how Monte Carlo codes apprehend the transport simulation of charged particles and the productive and destructive interactions between photons, electrons and positrons. There exists a huge variety of electromagnetic shower models which tackle this topic. Differences in the implementation of these models can lead to discrepancies in calculated values of absorbed dose between different Monte Carlo codes. The magnitude of order of such potential discrepancies should be quantified for JHR gamma-heating calculations. We consequently present a two-pronged plan. In a first phase, we intend to perform compared absorbed dose / KERMA Monte Carlo calculations in the JHR. This way, we will study the presence or absence of electronic equilibrium in the different JHR structures and experimental devices and we will give recommendations for the choice of KERMA or absorbed dose when calculating gamma heating in the JHR. In a second phase, we intend to perform compared TRIPOLI4 / MCNP absorbed dose calculations in a simplified JHR-representative geometry. For this comparison, we will use the same nuclear data library for both codes (the European library JEFF3.1.1 and photon library EPDL97) so as to isolate the effects from electromagnetic shower models on absorbed dose calculation. This way, we hope to get insightful feedback on these models and their implementation in Monte Carlo codes. (authors)« less

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...

Early Biochemical Effects of an Organic Mercury Fungicide on Infants: ``Dose Makes the Poison''

NASA Astrophysics Data System (ADS)

Gotelli, Carlos A.; Astolfi, Emilio; Cox, Christopher; Cernichiari, Elsa; Clarkson, Thomas W.

1985-02-01

Phenylmercury absorbed through the skin from contaminated diapers affected urinary excretion in infants in Buenos Aires. The effects were reversible and quantitatively related to the concentration of urinary mercury. Excretion of γ -glutamyl transpeptidase, an enzyme in the brush borders of renal tubular cells, increased in a dose-dependent manner when mercury excretion exceeded a ``threshold'' value. Urine volume also increased but at a higher threshold with respect to mercury. The results support the threshold concept of the systemic toxicity of metals. γ -Glutamyl transpeptidase is a useful and sensitive marker for preclinical effects of toxic metals.

Dose to 'water-like' media or dose to tissue in MV photons radiotherapy treatment planning: still a matter of debate.

PubMed

Andreo, Pedro

2015-01-07

The difference between Monte Carlo Treatment Planning (MCTP) based on the assumption of 'water-like' tissues with densities obtained from CT procedures, or on tissue compositions derived from CT-determined densities, have been investigated. Stopping powers and electron fluences have been calculated for a range of media and body tissues for 6 MV photon beams, including changes in their physical data (density and stopping powers). These quantities have been used to determine absorbed doses using cavity theory. It is emphasized that tissue compositions given in ICRU or ICRP reports should not be given the standing of physical constants as they correspond to average values obtained for a limited number of human-body samples. It has been shown that mass stopping-power ratios to water are more dependent on patient-to-patient composition differences, and therefore on their mean excitation energies (I-values), than on mass density. Electron fluence in different media are also more dependent on media composition (and their I-values) than on density. However, as a consequence of the balance between fluence and stopping powers, doses calculated from their product are more constant than what the independent stopping powers and fluence variations suggest. Additionally, cancelations in dose ratios minimize the differences between the 'water-like' and 'tissue' approaches, yielding practically identical results except for bone, and to a lesser extent for adipose tissue. A priori, changing from one approach to another does not seem to be justified considering the large number of approximations and uncertainties involved throughout the treatment planning tissue segmentation and dose calculation procedures. The key issue continues to be the composition of tissues and their I-values, and as these cannot be obtained for individual patients, whatever approach is selected does not lead to significant differences from a water reference dose, the maximum of these being of the order of 5% for bone tissues. Considering, however, current developments in advanced dose calculation methods, planning in terms of dose-to-tissue should be the preferred choice, under the expectancy that progress in the field will gradually improve some of the crude approximations included in MCTP and numerical transport methods. The small differences obtained also show that a retrospective conversion from dose-to-tissue to dose-to-water, based on a widely used approach, would mostly increase the final uncertainty of the treatment planning process. It is demonstrated that, due to the difference between electron fluence distributions in water and in body tissues, the conversion requires an additional fluence correction that has so far been neglected. An improved expression for the conversion and data for the fluence correction factor are provided. These will be necessary even in a dose-to-tissue environment, for the normalization of the treatment plan to the reference dosimetry of the treatment unit, always calibrated in terms of absorbed dose to water.

Dose to ‘water-like’ media or dose to tissue in MV photons radiotherapy treatment planning: still a matter of debate

NASA Astrophysics Data System (ADS)

Andreo, Pedro

2015-01-01

The difference between Monte Carlo Treatment Planning (MCTP) based on the assumption of ‘water-like’ tissues with densities obtained from CT procedures, or on tissue compositions derived from CT-determined densities, have been investigated. Stopping powers and electron fluences have been calculated for a range of media and body tissues for 6 MV photon beams, including changes in their physical data (density and stopping powers). These quantities have been used to determine absorbed doses using cavity theory. It is emphasized that tissue compositions given in ICRU or ICRP reports should not be given the standing of physical constants as they correspond to average values obtained for a limited number of human-body samples. It has been shown that mass stopping-power ratios to water are more dependent on patient-to-patient composition differences, and therefore on their mean excitation energies (I-values), than on mass density. Electron fluence in different media are also more dependent on media composition (and their I-values) than on density. However, as a consequence of the balance between fluence and stopping powers, doses calculated from their product are more constant than what the independent stopping powers and fluence variations suggest. Additionally, cancelations in dose ratios minimize the differences between the ‘water-like’ and ‘tissue’ approaches, yielding practically identical results except for bone, and to a lesser extent for adipose tissue. A priori, changing from one approach to another does not seem to be justified considering the large number of approximations and uncertainties involved throughout the treatment planning tissue segmentation and dose calculation procedures. The key issue continues to be the composition of tissues and their I-values, and as these cannot be obtained for individual patients, whatever approach is selected does not lead to significant differences from a water reference dose, the maximum of these being of the order of 5% for bone tissues. Considering, however, current developments in advanced dose calculation methods, planning in terms of dose-to-tissue should be the preferred choice, under the expectancy that progress in the field will gradually improve some of the crude approximations included in MCTP and numerical transport methods. The small differences obtained also show that a retrospective conversion from dose-to-tissue to dose-to-water, based on a widely used approach, would mostly increase the final uncertainty of the treatment planning process. It is demonstrated that, due to the difference between electron fluence distributions in water and in body tissues, the conversion requires an additional fluence correction that has so far been neglected. An improved expression for the conversion and data for the fluence correction factor are provided. These will be necessary even in a dose-to-tissue environment, for the normalization of the treatment plan to the reference dosimetry of the treatment unit, always calibrated in terms of absorbed dose to water.

Absorbed fractions in a voxel-based phantom calculated with the MCNP-4B code.

PubMed

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

2000-07-01

A new approach for calculating internal dose estimates was developed through the use of a more realistic computational model of the human body. The present technique shows the capability to build a patient-specific phantom with tomography data (a voxel-based phantom) for the simulation of radiation transport and energy deposition using Monte Carlo methods such as in the MCNP-4B code. MCNP-4B absorbed fractions for photons in the mathematical phantom of Snyder et al. agreed well with reference values. Results obtained through radiation transport simulation in the voxel-based phantom, in general, agreed well with reference values. Considerable discrepancies, however, were found in some cases due to two major causes: differences in the organ masses between the phantoms and the occurrence of organ overlap in the voxel-based phantom, which is not considered in the mathematical phantom.

Radon survey and soil gamma doses in primary schools of Batman, Turkey.

PubMed

Damla, Nevzat; Aldemir, Kamuran

2014-06-01

A survey was conducted to evaluate levels of indoor radon and gamma doses in 42 primary schools located in Batman, southeastern Anatolia, Turkey. Indoor radon measurements were carried out using CR-39 solid-state nuclear track detector-based radon dosimeters. The overall mean annual (222)Rn activity in the surveyed area was found to be 49 Bq m(-3) (equivalent to an annual effective dose of 0.25 mSv). However, in one of the districts (Besiri) the maximum radon value turned out to be 307 Bq m(-3). The estimated annual effective doses are less than the recommended action level (3-10 mSv). It is found that the radon concentration decreases with increasing floor number. The concentrations of natural and artificial radioisotopes were determined using gamma-ray spectroscopy for soil samples collected in close vicinity of the studied schools. The mean gamma activity concentrations in the soil samples were 31, 25, 329 and 12 Bq kg(-1) for (226)Ra, (232)Th, (40)K and (137)Cs, respectively. The radiological parameters such as the absorbed dose rate in air and the annual effective dose equivalent were calculated. These radiological parameters were evaluated and compared with the internationally recommended values.

MONTE CARLO STUDY OF THE CARDIAC ABSORBED DOSE DURING X-RAY EXAMINATION OF AN ADULT PATIENT.

PubMed

Kadri, O; Manai, K; Alfuraih, A

2016-12-01

The computational voxel phantom 'High-Definition Reference Korean-Man (HDRK-Man)' was implemented into the Monte Carlo transport toolkit Geant4. The voxel model, adjusted to the Reference Korean Man, is 171 cm in height and 68 kg in weight and composed of ∼30 million voxels whose size is 1.981 × 1.981 × 2.0854 mm 3 The Geant4 code is then utilised to compute the dose conversion coefficients (DCCs) expressed in absorbed dose per air kerma free in air for >30 tissues and organs, including almost all organs required in the new recommendation of the ICRP 103, due to a broad parallel beam of monoenergetic photons impinging in antero-postero direction with energy ranging from 10 to 150 keV. The computed DCCs of different organs are found to be in good agreement with data published using other simulation codes. Also, the influence of patient size on DCC values was investigated for a representative body size of the adult Korean patient population. The study was performed using five different sizes covering the range of 0.8-1.2 magnification order of the original HDRK-Man. It focussed on the computation of DCC for the human heart. Moreover, the provided DCCs were used to present an analytical parameterisation for the calculation of the cardiac absorbed dose for any arbitrary X-ray spectrum and for those patient sizes. Thus, the present work can be considered as an enhancement of the continuous studies performed by medical physicist as part of quality control tests and radiation protection dosimetry. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Absorbed dose estimates from a single measurement one to three days after the administration of 177Lu-DOTATATE/-TOC.

PubMed

Hänscheid, Heribert; Lapa, Constantin; Buck, Andreas K; Lassmann, Michael; Werner, Rudolf A

2017-01-01

To retrospectively analyze the accuracy of absorbed dose estimates from a single measurement of the activity concentrations in tumors and relevant organs one to three days after the administration of 177 Lu-DOTA-TATE/TOC assuming tissue specific effective half-lives. Activity kinetics in 54 kidneys, 30 neuroendocrine tumor lesions, 25 livers, and 27 spleens were deduced from series of planar images in 29 patients. After adaptation of mono- or bi-exponential fit functions to the measured data, it was analyzed for each fit function how precise the time integral can be estimated from fixed tissue-specific half-lives and a single measurement at 24, 48, or 72 h after the administration. For the kidneys, assuming a fixed tissue-specific half-life of 50 h, the deviations of the estimate from the actual integral were median (5 % percentile, 95 % percentile): -3 °% (-15 %>; +16 °%) for measurements after 24 h, +2 %> (-9 %>; +12 %>) for measurements after 48 h, and 0 % (-2 %; +12 %) for measurements after 72 h. The corresponding values for the other tissues, assuming fixed tissue-specific half-lives of 67 h for liver and spleen and 77 h for tumors, were +2 % (-25 %; +20 %) for measurements after 24 h, +2 °% (-16 %>; +17 %>) for measurements after 48 h, and +2 %> (-11 %>; +10 %>) for measurements after 72 h. Especially for the kidneys, which often represent the dose limiting organ, but also for liver, spleen, and neuroendocrine tumors, a meaningful absorbed dose estimate is possible from a single measurement after 2, more preferably 3 days after the administration of 177 Lu-DOTA-TATE/-TOC assuming fixed tissue specific effective half-lives. Schattauer GmbH.

Assessment of radiation-induced secondary cancer risk in the Brazilian population from left-sided breast-3D-CRT using MCNPX.

PubMed

Mendes, Bruno Melo; Trindade, Bruno Machado; Fonseca, Telma Cristina Ferreira; de Campos, Tarcisio Passos Ribeiro

2017-12-01

The aim of this work was to simulate a 6MV conventional breast 3D conformational radiation therapy (3D-CRT) with physical wedges (50 Gy/25#) in the left breast, calculate the mean absorbed dose in the body organs using robust models and computational tools and estimate the secondary cancer-incidence risk to the Brazilian population. The VW female phantom was used in the simulations. Planning target volume (PTV) was defined in the left breast. The 6MV parallel-opposed fields breast-radiotherapy (RT) protocol was simulated with MCNPx code. The absorbed doses were evaluated in all the organs. The secondary cancer-incidence risk induced by radiotherapy was calculated for different age groups according to the BEIR VII methodology. RT quality indexes indicated that the protocol was properly simulated. Significant absorbed dose values in red bone marrow, RBM (0.8 Gy) and stomach (0.6 Gy) were observed. The contralateral breast presented the highest risk of incidence of a secondary cancer followed by leukaemia, lung and stomach. The risk of a secondary cancer-incidence by breast-RT, for the Brazilian population, ranged between 2.2-1.7% and 0.6-0.4%. RBM and stomach, usually not considered as OAR, presented high second cancer incidence risks of 0.5-0.3% and 0.4-0.1%, respectively. This study may be helpful for breast-RT risk/benefit assessment. Advances in knowledge: MCNPX-dosimetry was able to provide the scatter radiation and dose for all body organs in conventional breast-RT. It was found a relevant risk up to 2.2% of induced-cancer from breast-RT, considering the whole thorax organs and Brazilian cancer-incidence.

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.

EUV lithography reticles fabricated without the use of a patterned absorber

DOEpatents

Stearns, Daniel G.; Sweeney, Donald W.; Mirkarimi, Paul B.

2006-05-23

Absorber material used in conventional EUVL reticles is eliminated by introducing a direct modulation in the complex-valued reflectance of the multilayer. A spatially localized energy source such as a focused electron or ion beam directly writes a reticle pattern onto the reflective multilayer coating. Interdiffusion is activated within the film by an energy source that causes the multilayer period to contract in the exposed regions. The contraction is accurately determined by the energy dose. A controllable variation in the phase and amplitude of the reflected field in the reticle plane is produced by the spatial modulation of the multilayer period. This method for patterning an EUVL reticle has the advantages (1) avoiding the process steps associated with depositing and patterning an absorber layer and (2) providing control of the phase and amplitude of the reflected field with high spatial resolution.

Method for fabricating reticles for EUV lithography without the use of a patterned absorber

DOEpatents

Stearns, Daniel G [Los Altos, CA; Sweeney, Donald W [San Ramon, CA; Mirkarimi, Paul B [Sunol, CA

2003-10-21

Absorber material used in conventional EUVL reticles is eliminated by introducing a direct modulation in the complex-valued reflectance of the multilayer. A spatially localized energy source such as a focused electron or ion beam directly writes a reticle pattern onto the reflective multilayer coating. Interdiffusion is activated within the film by an energy source that causes the multilayer period to contract in the exposed regions. The contraction is accurately determined by the energy dose. A controllable variation in the phase and amplitude of the reflected field in the reticle plane is produced by the spatial modulation of the multilayer period. This method for patterning an EUVL reticle has the advantages of (1) avoiding the process steps associated with depositing and patterning an absorber layer and (2) providing control of the phase and amplitude of the reflected field with high spatial resolution.

In vivo percutaneous absorption of boric acid, borax, and disodium octaborate tetrahydrate in humans compared to in vitro absorption in human skin from infinite and finite doses.

PubMed

Wester, R C; Hui, X; Hartway, T; Maibach, H I; Bell, K; Schell, M J; Northington, D J; Strong, P; Culver, B D

1998-09-01

Literature from the first half of this century report concern for toxicity from topical use of boric acid, but assessment of percutaneous absorption has been impaired by lack of analytical sensitivity. Analytical methods in this study included inductively coupled plasma-mass spectrometry which now allows quantitation of percutaneous absorption of 10B in 10B-enriched boric acid, borax, and disodium octaborate tetrahydrate (DOT) in biological matrices. This made it possible, in the presence of comparatively large natural dietary boron intakes for the in vivo segment of this study, to quantify the boron passing through skin. Human volunteers were dosed with 10B-enriched boric acid, 5.0%, borax, 5.0%, or disodium octaborate tetrahydrate, 10%, in aqueous solutions. Urinalysis, for boron and changes in boron isotope ratios, was used to measure absorption. Boric acid in vivo percutaneous absorption was 0.226 (SD = 0.125) mean percentage dose, with flux and permeability constant (Kp) calculated at 0.009 microgram/cm2/h and 1.9 x 10(-7) cm/h, respectively. Borax absorption was 0.210 (SD = 0.194) mean percentage of dose, with flux and Kp calculated at 0.009 microgram/cm2/h and 1.8 x 10(-7) cm/h, respectively. DOT absorption was 0.122 (SD = 0.108) mean percentage, with flux and Kp calculated at 0.01 microgram/cm2/h and 1.0 x 10(-7) cm/h, respectively. Pretreatment with the potential skin irritant 2% sodium lauryl sulfate had no effect on boron skin absorption. In vitro human skin percentage of doses of boric acid absorbed were 1.2 for a 0.05% solution, 0.28 for a 0.5% solution, and 0.70 for a 5.0% solution. These absorption amounts translated into flux values of, respectively, 0.25, 0.58, and 14.58 micrograms/cm2/h and permeability constants (Kp) of 5.0 x 10(-4), 1.2 x 10(-4), and 2.9 x 10(-4) cm/h for the 0.05, 0.5, and 5.0% solutions. The above in vitro doses were at infinite, 1000 microliters/cm2 volume. At 2 microliters/cm2 (the in vivo dosing volume), flux decreased some 200-fold to 0.07 microgram/cm2/h and Kp of 1.4 x 10(-6) cm/h, while percentage of dose absorbed was 1.75%. Borax dosed at 5.0%/1000 microliters/cm2 had 0.41% dose absorbed, flux at 8.5 micrograms/cm2/h, and Kp was 1.7 x 10(-4) cm/h. Disodium octaborate tetrahydrate (DOT) dosed at 10%/1000 microliters/cm2 was 0.19% dose absorbed, flux at 7.9 micrograms/cm2/h, and Kp was 0.8 x 10(-4) cm/h. These in vitro results from infinite doses (1000 microliters/cm2) were 1000-fold greater than those obtained in the companion in vivo study. The results from the finite (2 microliters/cm2) dosing were closer (10-fold difference) to the in vivo results. General application of infinite dose percutaneous absorption values for risk assessment is questioned by these results. These in vivo results show that percutaneous absorption of boron, as boric acid, borax, and disodium octaborate tetrahydrate, through intact human skin, is low and is significantly less than the average daily dietary intake. This very low boron skin absorption makes it apparent that, for the borates tested, the use of gloves to prevent systemic uptake is unnecessary. These findings do not apply to abraded or otherwise damaged skin.

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.

Dose conversion coefficients for electron exposure of the human eye lens: calculations including a whole body phantom.

PubMed

Behrens, R

2013-07-01

In this work, conversion coefficients from electron fluence to absorbed dose to the eye lens were calculated using Monte Carlo simulations based on a detailed stylised eye model and a very simple but whole body phantom. These data supersede and complement data published earlier based on the simulation of only a single stylised eye. The new data differ from the old ones by not more than 3, 4, 7 and 16 % for angles of radiation incidence of α=0°, 15°, 30° and 45°, respectively, due to the inclusion of the whole body phantom. The data presented in the present work also complement those of a recent report of the International Commission on Radiological Protection (ICRP) (ICRP Publication 116), where conversion coefficients from electron fluence to absorbed dose to the lens of the eye are shown for solely 0°, 180° and isotropic radiation incidence (but for a much broader range of energies). In this article, values are provided for angles of incidence of 0° up to 180° in steps of 15° and for rotational geometry; no systematic deviation was observed from the values given in ICRP Publication 116 for 0° (based on the application of a bare eye) and 180° (based on the application of a voxel whole body phantom). Data are given for monoenergetic electrons from 0.1 up to 10 MeV and for a broad parallel beam geometry in vacuum.

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.

Measurement of the terrestrial and anthropogenic radionuclide concentrations in Bafra Kizilirmak delta (bird sanctuary) in Turkey.

PubMed

Mutuk, Halil; Gümüs, Hasan; Turhan, Seref

2014-01-01

In this study, the activity concentrations of terrestrial and anthropogenic radionuclides in the soil samples collected from Bafra Kızılırmak Delta were measured by using gamma spectrometry with an NaI(Tl) detector. The average values of activity concentrations of (238)U, (232)Th and (40)K were found to be 37.2±2.8, 33.7±3.1 and 413.0±59.8 Bq kg(-1), respectively. (137)Cs was also measured in some samples. It has a mean value of 13.8±1.0 Bq kg(-1). From the activity concentrations, the absorbed gamma dose rates in outdoor and the corresponding annual effective dose rates and external hazard index (Hex) were estimated.

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

Dosimetric characteristics of the University of Washington Clinical Neutron Therapy System

NASA Astrophysics Data System (ADS)

Moffitt, Gregory B.; Stewart, Robert D.; Sandison, George A.; Goorley, John T.; Argento, David C.; Jevremovic, Tatjana; Emery, Robert; Wootton, Landon S.; Parvathaneni, Upendra; Laramore, George E.

2018-05-01

The University of Washington (UW) Clinical Neutron Therapy System (CNTS), which generates high linear energy transfer fast neutrons through interactions of 50.5 MeV protons incident on a Be target, has depth-dose characteristics similar to 6 MV x-rays. In contrast to the fixed beam angles and primitive blocking used in early clinical trials of neutron therapy, the CNTS has a gantry with a full 360° of rotation, internal wedges, and a multi-leaf collimator (MLC). Since October of 1984, over 3178 patients have received conformal neutron therapy treatments using the UW CNTS. In this work, the physical and dosimetric characteristics of the CNTS are documented through comparisons of measurements and Monte Carlo simulations. A high resolution computed tomography scan of the model 17 ionization chamber (IC-17) has also been used to improve the accuracy of simulations of the absolute calibration geometry. The response of the IC-17 approximates well the kinetic energy released per unit mass (KERMA) in water for neutrons and photons for energies from a few tens of keV up to about 20 MeV. Above 20 MeV, the simulated model 17 ion chamber response is 20%–30% higher than the neutron KERMA in water. For CNTS neutrons, simulated on- and off-axis output factors in water match measured values within ~2%  ±  2% for rectangular and irregularly shaped field with equivalent square areas ranging in a side dimension from 2.8 cm to 30.7 cm. Wedge factors vary by less than 1.9% of the measured dose in water for clinically relevant field sizes. Simulated tissue maximum ratios in water match measured values within 3.3% at depths up to 20 cm. Although the absorbed dose for water and adipose tissue are within 2% at a depth of 1.7 cm, the absorbed dose in muscle and bone can be as much as 12 to 40% lower than the absorbed dose in water. The reported studies are significant from a historical perspective and as additional validation of a new tool for patient quality assurance and as an aid in ongoing efforts to clinically implement advanced treatment techniques, such as intensity modulated neutron therapy, at the UW.

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)

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

Measurements of radioactivity and dose assessments in some building materials in Bitlis, Turkey.

PubMed

Kayakökü, Halime; Karatepe, Şule; Doğru, Mahmut

2016-09-01

In this study, samples of perlite, pumice and Ahlat stones (Ignimbrite) extracted from mines in Bitlis and samples of other building materials produced in facilities in Bitlis were collected and analyzed. Activity concentrations of (226)Ra, (232)Th and (40)K in samples of building materials were measured using NaI detector (NaI(Tl)) with an efficiency of 24%. The radon measurements of building material samples were determined using CR-39 nuclear track detectors. (226)Ra, (232)Th and (40)K radioactivity concentrations ranged from (29.6±5.9 to 228.2±38.1Bq/kg), (10.8±5.4 to 95.5±26.1Bq/kg) and (249.3±124.7 to 2580.1±266.9Bq/kg), respectively. Radon concentration, radium equivalent activities, absorbed dose rate, excess lifetime cancer risk and the values of hazard indices were calculated for the measured samples to assess the radiation hazards arising from using those materials in the construction of dwellings. Radon concentration ranged between 89.2±12.0Bq/m(3) and 1141.0±225.0Bq/m(3). It was determined that Raeq values of samples conformed to world standards except for perlite and single samples of brick and Ahlat stone. Calculated values of absorbed dose rate ranged from 81.3±20.5 to 420.6±42.8nGy/h. ELCR values ranged from (1.8±0.3)×10(-3) to (9.0±1.0)×10(-3). All samples had ELCR values higher than the world average. The values of Hin and Hex varied from 0.35±0.11 to 1.78±0.18 and from 0.37±0.09 to 1.17±0.13, respectively. The results were compared with standard radioactivity values determined by international organizations and with similar studies. There would be a radiation risk for people living in buildings made of perlite, Ahlat-1 and Brick-3. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

Evaluation of radiation dose to anthropomorphic paediatric models from positron-emitting labelled tracers

NASA Astrophysics Data System (ADS)

Xie, Tianwu; Zaidi, Habib

2014-03-01

PET uses specific molecules labelled with positron-emitting radionuclides to provide valuable biochemical and physiological information. However, the administration of radiotracers to patients exposes them to low-dose ionizing radiation, which is a concern in the paediatric population since children are at a higher cancer risk from radiation exposure than adults. Therefore, radiation dosimety calculations for commonly used positron-emitting radiotracers in the paediatric population are highly desired. We evaluate the absorbed dose and effective dose for 19 positron-emitting labelled radiotracers in anthropomorphic paediatric models including the newborn, 1-, 5-, 10- and 15-year-old male and female. This is achieved using pre-calculated S-values of positron-emitting radionuclides of UF-NCI paediatric phantoms and published biokinetic data for various radiotracers. The influence of the type of anthropomorphic model, tissue weight factors and direct human- versus mouse-derived biokinetic data on the effective dose for paediatric phantoms was also evaluated. In the case of 18F-FDG, dosimetry calculations of reference paediatric patients from various dose regimens were also calculated. Among the considered radiotracers, 18F-FBPA and 15O-water resulted in the highest and lowest effective dose in the paediatric phantoms, respectively. The ICRP 103 updated tissue-weighting factors decrease the effective dose in most cases. Substantial differences of radiation dose were observed between direct human- versus mouse-derived biokinetic data. Moreover, the effect of using voxel- versus MIRD-type models on the calculation of the effective dose was also studied. The generated database of absorbed organ dose and effective dose for various positron-emitting labelled radiotracers using new generation computational models and the new ICRP tissue-weighting factors can be used for the assessment of radiation risks to paediatric patients in clinical practice. This work also contributes to a better understanding of the factors influencing patient-specific radiation dose calculation.

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

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

Reference dosimetry of proton pencil beams based on dose-area product: a proof of concept.

PubMed

Gomà, Carles; Safai, Sairos; Vörös, Sándor

2017-06-21

This paper describes a novel approach to the reference dosimetry of proton pencil beams based on dose-area product ([Formula: see text]). It depicts the calibration of a large-diameter plane-parallel ionization chamber in terms of dose-area product in a 60 Co beam, the Monte Carlo calculation of beam quality correction factors-in terms of dose-area product-in proton beams, the Monte Carlo calculation of nuclear halo correction factors, and the experimental determination of [Formula: see text] of a single proton pencil beam. This new approach to reference dosimetry proves to be feasible, as it yields [Formula: see text] values in agreement with the standard and well-established approach of determining the absorbed dose to water at the centre of a broad homogeneous field generated by the superposition of regularly-spaced proton pencil beams.

Dosimetric characterization of GafChromic EBT film and its implication on film dosimetry quality assurance.

PubMed

Fuss, Martina; Sturtewagen, Eva; De Wagter, Carlos; Georg, Dietmar

2007-07-21

The suitability of radiochromic EBT film was studied for high-precision clinical quality assurance (QA) by identifying the dose response for a wide range of irradiation parameters typically modified in highly-conformal treatment techniques. In addition, uncertainties associated with varying irradiation conditions were determined. EBT can be used for dose assessment of absorbed dose levels as well as relative dosimetry when compared to absolute absorbed dose calibrated using ionization chamber results. For comparison, a silver halide film (Kodak EDR-2) representing the current standard in film dosimetry was included. As an initial step a measurement protocol yielding accurate and precise results was established for a flatbed transparency scanner (Epson Expression 1680 Pro) that was utilized as a film reading instrument. The light transmission measured by the scanner was found to depend on the position of the film on the scanner plate. For three film pieces irradiated with doses of 0 Gy, approximately 1 Gy and approximately 7 Gy, the pixel values measured in portrait or landscape mode differed by 4.7%, 6.2% and 10.0%, respectively. A study of 200 film pieces revealed an excellent sheet-to-sheet uniformity. On a long time scale, the optical development of irradiated EBT film consisted of a slow but steady increase of absorbance which was not observed to cease during 4 months. Sensitometric curves of EBT films obtained under reference conditions (SSD = 95 cm, FS = 5 x 5 cm(2), d = 5 cm) for 6, 10 and 25 MV photon beams did not show any energy dependence. The average separation between all curves was only 0.7%. The variation of the depth d (range 2-25 cm) in the phantom did not affect the dose response of EBT film. Also the influence of the radiation field size (range 3 x 3-40 x 40 cm(2)) on the sensitometric curve was not significant. For EDR-2 films maximum differences between the calibration curves reached 7-8% for X6MV and X25MV. Radiochromic EBT film, in combination with a flatbed scanner, presents a versatile system for high-precision dosimetry in two dimensions, provided that the intrinsic behaviour of the film reading device is taken into account. EBT film itself presents substantial improvements on formerly available models of radiographic and a radiochromic film and its dosimetric characteristics allow us to measure absorbed dose levels in a large variety of situations with a single calibration curve.

Dosimetric characterization of GafChromic EBT film and its implication on film dosimetry quality assurance

NASA Astrophysics Data System (ADS)

Fuss, Martina; Sturtewagen, Eva; DeWagter, Carlos; Georg, Dietmar

2007-07-01

The suitability of radiochromic EBT film was studied for high-precision clinical quality assurance (QA) by identifying the dose response for a wide range of irradiation parameters typically modified in highly-conformal treatment techniques. In addition, uncertainties associated with varying irradiation conditions were determined. EBT can be used for dose assessment of absorbed dose levels as well as relative dosimetry when compared to absolute absorbed dose calibrated using ionization chamber results. For comparison, a silver halide film (Kodak EDR-2) representing the current standard in film dosimetry was included. As an initial step a measurement protocol yielding accurate and precise results was established for a flatbed transparency scanner (Epson Expression 1680 Pro) that was utilized as a film reading instrument. The light transmission measured by the scanner was found to depend on the position of the film on the scanner plate. For three film pieces irradiated with doses of 0 Gy, ~1 Gy and ~7 Gy, the pixel values measured in portrait or landscape mode differed by 4.7%, 6.2% and 10.0%, respectively. A study of 200 film pieces revealed an excellent sheet-to-sheet uniformity. On a long time scale, the optical development of irradiated EBT film consisted of a slow but steady increase of absorbance which was not observed to cease during 4 months. Sensitometric curves of EBT films obtained under reference conditions (SSD = 95 cm, FS = 5 × 5 cm2, d = 5 cm) for 6, 10 and 25 MV photon beams did not show any energy dependence. The average separation between all curves was only 0.7%. The variation of the depth d (range 2-25 cm) in the phantom did not affect the dose response of EBT film. Also the influence of the radiation field size (range 3 × 3-40 × 40 cm2) on the sensitometric curve was not significant. For EDR-2 films maximum differences between the calibration curves reached 7-8% for X6MV and X25MV. Radiochromic EBT film, in combination with a flatbed scanner, presents a versatile system for high-precision dosimetry in two dimensions, provided that the intrinsic behaviour of the film reading device is taken into account. EBT film itself presents substantial improvements on formerly available models of radiographic and a radiochromic film and its dosimetric characteristics allow us to measure absorbed dose levels in a large variety of situations with a single calibration curve.

[Use of lithium carbonate as a leukocyte stimulant in acute radiation sickness in humans].

PubMed

Konchalovskiĭ, M V; Shishkova, T V; Chotiĭ, V G; Baranov, A E

1989-03-01

A total of 50 patients, who had suffered from acute radiation sickness (I-III degree of severity) as a result of the accident at the Chernobyl Nuclear Power Plant, were followed up for hematological changes. The absorbed dose of relatively even gamma-irradiation assessed by karyometry fluctuated from 0.5 to 5.7 Gy. In 17 of the patients the influence of lithium carbonate on the course of radiation neutropenia was evaluated. No appreciable effect of the agent administration in a dose of 900 mg/patient/day was recorder from 9 to 42 day after irradiation. The authors have also considered the correlations of the values of irradiation doses calculated by varying methods of biological dosimetry.

Unexplained overexposures on physical dosimetry reported by biological dosimetry.

PubMed

Montoro, A; Almonacid, M; Villaescusa, J I; Verdu, G

2009-01-01

The Medical Service of the Radiation Protection Service from the University Hospital La Fe (Valencia, Spain), carries out medical examinations of the workers occupationally exposed to ionising radiation. The Biological Dosimetry Laboratory is developing its activity since 2001. Up to now, the activities have been focused in performing biological dosimetry studies of Interventionists workers from La Fe Hospital. Recently, the Laboratory has been authorized by the Health Authority in the Valencian Community. Unexplained overexposures of workers and patients are also studied. Workers suspected of being overexposed to ionising radiation were referred for investigation by cytogenetic analysis. Two of these were from Hospitals of the Valencian Community and one belonged to an uranium mine from Portugal. Hospital workers had a physical dose by thermoluminiscence dosimeters (TLD) that exceeded the established limit. The worker of the uranium mine received a dose from a lost source of Cesium 137 with an activity of 170 mCi. All three cases showed normal values after the hematological analysis. Finally, the aim of this study consist to determine whether the dose showed by the dosimeter is reliable or not. In the case of workers that wore dosimeter, it is concluded that the doses measured by dosimeter are not corresponding to real doses. Hospital worker with a physical dose of 2.6 Sv and 0.269 Sv had an estimated absorbed dose by biological dosimetry of 0.076 Gy (0-0.165 Gy) and 0 Gy (0-0.089 Gy), respectively. In case of the mine worker an estimated absorbed dose of 0.073 Gy (0-0.159 Gy) was obtained by biological dosimetry. In all cases we used the odds ratio to present the results due to a very low frequency of observed aberrations [1].

Calibration and error analysis of metal-oxide-semiconductor field-effect transistor dosimeters for computed tomography radiation dosimetry.

PubMed

Trattner, Sigal; Prinsen, Peter; Wiegert, Jens; Gerland, Elazar-Lars; Shefer, Efrat; Morton, Tom; Thompson, Carla M; Yagil, Yoad; Cheng, Bin; Jambawalikar, Sachin; Al-Senan, Rani; Amurao, Maxwell; Halliburton, Sandra S; Einstein, Andrew J

2017-12-01

Metal-oxide-semiconductor field-effect transistors (MOSFETs) serve as a helpful tool for organ radiation dosimetry and their use has grown in computed tomography (CT). While different approaches have been used for MOSFET calibration, those using the commonly available 100 mm pencil ionization chamber have not incorporated measurements performed throughout its length, and moreover, no previous work has rigorously evaluated the multiple sources of error involved in MOSFET calibration. In this paper, we propose a new MOSFET calibration approach to translate MOSFET voltage measurements into absorbed dose from CT, based on serial measurements performed throughout the length of a 100-mm ionization chamber, and perform an analysis of the errors of MOSFET voltage measurements and four sources of error in calibration. MOSFET calibration was performed at two sites, to determine single calibration factors for tube potentials of 80, 100, and 120 kVp, using a 100-mm-long pencil ion chamber and a cylindrical computed tomography dose index (CTDI) phantom of 32 cm diameter. The dose profile along the 100-mm ion chamber axis was sampled in 5 mm intervals by nine MOSFETs in the nine holes of the CTDI phantom. Variance of the absorbed dose was modeled as a sum of the MOSFET voltage measurement variance and the calibration factor variance, the latter being comprised of three main subcomponents: ionization chamber reading variance, MOSFET-to-MOSFET variation and a contribution related to the fact that the average calibration factor of a few MOSFETs was used as an estimate for the average value of all MOSFETs. MOSFET voltage measurement error was estimated based on sets of repeated measurements. The calibration factor overall voltage measurement error was calculated from the above analysis. Calibration factors determined were close to those reported in the literature and by the manufacturer (~3 mV/mGy), ranging from 2.87 to 3.13 mV/mGy. The error σ V of a MOSFET voltage measurement was shown to be proportional to the square root of the voltage V: σV=cV where c = 0.11 mV. A main contributor to the error in the calibration factor was the ionization chamber reading error with 5% error. The usage of a single calibration factor for all MOSFETs introduced an additional error of about 5-7%, depending on the number of MOSFETs that were used to determine the single calibration factor. The expected overall error in a high-dose region (~30 mGy) was estimated to be about 8%, compared to 6% when an individual MOSFET calibration was performed. For a low-dose region (~3 mGy), these values were 13% and 12%. A MOSFET calibration method was developed using a 100-mm pencil ion chamber and a CTDI phantom, accompanied by an absorbed dose error analysis reflecting multiple sources of measurement error. When using a single calibration factor, per tube potential, for different MOSFETs, only a small error was introduced into absorbed dose determinations, thus supporting the use of a single calibration factor for experiments involving many MOSFETs, such as those required to accurately estimate radiation effective dose. © 2017 American Association of Physicists in Medicine.

Characterization and optical studies of 90/10 (wt/wt%) PVA/β-chitin blend irradiated with γ-rays.

PubMed

Abd El-Kader, F H; Gaafer, S A; Abd El-Kader, M F H

2014-10-15

X-ray diffraction, IR spectroscopy and UV/visible spectra were studied as a function of gamma irradiation doses (5-100kGy) for 90/10 (wt/wt%) PVA/β-chitin. A new intense reflection peak at 2θ=21.5° appeared in the X-ray spectrum of the sample irradiated at 50kGy γ-dose. Besides, the band centered at 2931cm(-1) in IR spectrum splits into two clearly separated bands around 2919 and 2941cm(-1) for the sample irradiated at 10kGy γ-dose. The disappearance of the absorption band at 280nm of PVA in the blend sample indicates that the ligand PVA becomes opaque in the UV region and provides evidence for the miscibility between homopolymers. The value of absorbance, in UV/visible range, at 10kGy γ-dose was the highest one compared to the other γ-doses. The location of the γ-doses on the chromaticity diagram was different, indicating the change in the spectral colors of the investigated blend. In addition, the absorption edge, band tail and color parameters values were determined as a function of γ-doses. Copyright © 2014 Elsevier B.V. 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.

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

Reconstruction of Internal Doses for the Alpha-Risk Case-Control Study of Lung Cancer and Leukaemia Among European Nuclear Workers.

PubMed

Bingham, Derek; Bérard, Philippe; Birchall, Alan; Bull, Richard; Cardis, Elisabeth; Challeton-de Vathaire, Cécile; Grellier, James; Hurtgen, Christian; Puncher, Matthew; Riddell, Anthony; Thierry-Chef, Isabelle

2017-05-01

The Alpha-Risk study required the reconstruction of doses to lung and red bone marrow for lung cancer and leukaemia cases and their matched controls from cohorts of nuclear workers in the UK, France and Belgium. The dosimetrists and epidemiologists agreed requirements regarding the bioassay data, biokinetic and dosimetric models and dose assessment software to be used and doses to be reported. The best values to use for uncertainties on the monitoring data, setting of exposure regimes and characteristics of the exposure material, including lung solubility, were the responsibility of the dosimetrist responsible for each cohort. Among 1721 subjects, the median absorbed dose to the lung from alpha radiations was 2.1 mGy, with a maximum dose of 316 mGy. The lung doses calculated reflect the higher levels of exposure seen among workers in the early years of the nuclear industry compared to today. © Crown copyright 2016.

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.

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.

The influence of neutron contamination on dosimetry in external photon beam radiotherapy

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

Horst, Felix, E-mail: felix.ernst.horst@kmub.thm.de; Czarnecki, Damian; Zink, Klemens

Purpose: Photon fields with energies above ∼7 MeV are contaminated by neutrons due to photonuclear reactions. Their influence on dosimetry—although considered to be very low—is widely unexplored. Methods: In this work, Monte Carlo based investigations into this issue performed with FLUKA and EGSNRC are presented. A typical Linac head in 18 MV-X mode was modeled equivalently within both codes. EGSNRC was used for the photon and FLUKA for the neutron production and transport simulation. Water depth dose profiles and the response of different detectors (Farmer chamber, TLD-100, TLD-600H, and TLD-700H chip) in five representative depths were simulated and the neutrons’more » impact (neutron absorbed dose relative to photon absorbed dose) was calculated. To take account of the neutrons’ influence, a theoretically required correction factor was defined and calculated for five representative water depths. Results: The neutrons’ impact on the absorbed dose to water was found to be below 0.1% for all depths and their impact on the response of the Farmer chamber and the TLD-700H chip was found to be even less. For the TLD-100 and the TLD-600H chip it was found to be up to 0.3% and 0.7%, respectively. The theoretical correction factors to be applied to absorbed dose to water values measured with these four detectors in a depth different from the reference/calibration depth were calculated and found to be below 0.05% for the Farmer chamber and the TLD-700H chip, but up to 0.15% and 0.35% for the TLD-100 and TLD-600H chips, respectively. In thermoluminescence dosimetry the neutrons’ influence (and therefore the additional inaccuracy in measurement) was found to be higher for TLD materials whose {sup 6}Li fraction is high, such as TLD-100 and TLD-600H, resulting from the thermal neutron capture reaction on {sup 6}Li. Conclusions: The impact of photoneutrons on the absorbed dose to water and on the response of a typical ionization chamber as well as three different types of TLD chips was quantified and was as expected found to be very low relative to that of the primary photons. For most practical reasons the neutrons’ influence on dosimetry might be neglected while for absolute precise thermoluminescence dosimetry in high energy photon fields, the use of TLD-700H (<0.03% {sup 6}Li) instead of the commonly used TLD-100 (7.4% {sup 6}Li) or even the extra neutron sensitive TLD-600H is recommended (95.6% {sup 6}Li) due to the additional inaccuracy in measurement for TLD materials with a high {sup 6}Li fraction.« less

The influence of neutron contamination on dosimetry in external photon beam radiotherapy.

PubMed

Horst, Felix; Czarnecki, Damian; Zink, Klemens

2015-11-01

Photon fields with energies above ∼7 MeV are contaminated by neutrons due to photonuclear reactions. Their influence on dosimetry-although considered to be very low-is widely unexplored. In this work, Monte Carlo based investigations into this issue performed with fluka and egsnrc are presented. A typical Linac head in 18 MV-X mode was modeled equivalently within both codes. egsnrc was used for the photon and fluka for the neutron production and transport simulation. Water depth dose profiles and the response of different detectors (Farmer chamber, TLD-100, TLD-600H, and TLD-700H chip) in five representative depths were simulated and the neutrons' impact (neutron absorbed dose relative to photon absorbed dose) was calculated. To take account of the neutrons' influence, a theoretically required correction factor was defined and calculated for five representative water depths. The neutrons' impact on the absorbed dose to water was found to be below 0.1% for all depths and their impact on the response of the Farmer chamber and the TLD-700H chip was found to be even less. For the TLD-100 and the TLD-600H chip it was found to be up to 0.3% and 0.7%, respectively. The theoretical correction factors to be applied to absorbed dose to water values measured with these four detectors in a depth different from the reference/calibration depth were calculated and found to be below 0.05% for the Farmer chamber and the TLD-700H chip, but up to 0.15% and 0.35% for the TLD-100 and TLD-600H chips, respectively. In thermoluminescence dosimetry the neutrons' influence (and therefore the additional inaccuracy in measurement) was found to be higher for TLD materials whose 6Li fraction is high, such as TLD-100 and TLD-600H, resulting from the thermal neutron capture reaction on 6Li. The impact of photoneutrons on the absorbed dose to water and on the response of a typical ionization chamber as well as three different types of TLD chips was quantified and was as expected found to be very low relative to that of the primary photons. For most practical reasons the neutrons' influence on dosimetry might be neglected while for absolute precise thermoluminescence dosimetry in high energy photon fields, the use of TLD-700H (<0.03% 6Li) instead of the commonly used TLD-100 (7.4% 6Li) or even the extra neutron sensitive TLD-600H is recommended (95.6% 6Li) due to the additional inaccuracy in measurement for TLD materials with a high 6Li fraction.

KEY COMPARISON: Final report of the SIM 60Co absorbed-dose-to-water comparison SIM.RI(I)-K4

NASA Astrophysics Data System (ADS)

Ross, C. K.; Shortt, K. R.; Saravi, M.; Meghzifene, A.; Tovar, V. M.; Barbosa, R. A.; da Silva, C. N.; Carrizales, L.; Seltzer, S. M.

2008-01-01

Transfer chambers were used to compare the standards for 60Co absorbed dose to water maintained by seven laboratories. Six of the laboratories were members of the Sistema Interamericano de Metrología (SIM) regional metrology organization while the seventh was the International Atomic Energy Agency (IAEA) laboratory in Vienna. The National Research Council (NRC) acted as the pilot laboratory for the comparison. Because of the participation of laboratories holding primary standards, the comparison results could be linked to the key comparison reference value maintained by the Bureau International des Poids et Mesures (BIPM). The results for all laboratories were within the expanded uncertainty (two standard deviations) of the reference value. The estimated relative standard uncertainty on the comparison between any pair of laboratories ranged from 0.6% to 1.4%. The largest discrepancy between any two laboratories was 1.3%. Main text. To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/. The final report has been peer-reviewed and approved for publication by the CCRI Section I, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).

The effect of systematic set-up deviations on the absorbed dose distribution for left-sided breast cancer treated with respiratory gating

NASA Astrophysics Data System (ADS)

Edvardsson, A.; Ceberg, S.

2013-06-01

The aim of this study was 1) to investigate interfraction set-up uncertainties for patients treated with respiratory gating for left-sided breast cancer, 2) to investigate the effect of the inter-fraction set-up on the absorbed dose-distribution for the target and organs at risk (OARs) and 3) optimize the set-up correction strategy. By acquiring multiple set-up images the systematic set-up deviation was evaluated. The effect of the systematic set-up deviation on the absorbed dose distribution was evaluated by 1) simulation in the treatment planning system and 2) measurements with a biplanar diode array. The set-up deviations could be decreased using a no action level correction strategy. Not using the clinically implemented adaptive maximum likelihood factor for the gating patients resulted in better set-up. When the uncorrected set-up deviations were simulated the average mean absorbed dose was increased from 1.38 to 2.21 Gy for the heart, 4.17 to 8.86 Gy to the left anterior descending coronary artery and 5.80 to 7.64 Gy to the left lung. Respiratory gating can induce systematic set-up deviations which would result in increased mean absorbed dose to the OARs if not corrected for and should therefore be corrected for by an appropriate correction strategy.

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.

An evaluation of in-plane shields during thoracic CT.

PubMed

Foley, S J; McEntee, M F; Rainford, L A

2013-08-01

The object of this study was to compare organ dose and image quality effects of using bismuth and barium vinyl in-plane shields with standard and low tube current thoracic CT protocols. A RANDO phantom was scanned using a 64-slice CT scanner and three different thoracic protocols. Thermoluminescent dosemeters were positioned in six locations to record surface and absorbed breast and lung doses. Image quality was assessed quantitatively using region of interest measurements. Scanning was repeated using bismuth and barium vinyl in-plane shields to cover the breasts and the results were compared with standard and reduced dose protocols. Dose reductions were most evident in the breast, skin and anterior lung when shielding was used, with mean reductions of 34, 33 and 10 % for bismuth and 23, 18 and 11 % for barium, respectively. Bismuth was associated with significant increases in both noise and CT attenuation values for all the three protocols, especially anteriorly and centrally. Barium shielding had a reduced impact on image quality. Reducing the overall tube current reduced doses in all the locations by 20-27 % with similar increases in noise as shielding, without impacting on attenuation values. Reducing the overall tube current best optimises dose with minimal image quality impact. In-plane shields increase noise and attenuation values, while reducing anterior organ doses primarily. Shielding remains a useful optimisation tool in CT and barium is an effective alternative to bismuth especially when image quality is of concern.

Characterization and implementation of OSL dosimeters for use in evaluating the efficacy of organ-based tube current modulation for CT scans of the face and orbits

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

Marsh, R. M.; Silosky, M., E-mail: michael.silosky@ucdenver.edu

Purpose: The purpose of this work was to characterize commercially available optically stimulated luminescent (OSL) dosimeters for general clinical applications and apply the results to the development of a method to evaluate the efficacy of a vendor-specific organ-based tube current modulation application for both phantom and clinical computed tomography (CT) scans of the face and orbits. Methods: This study consisted of three components: (1) thorough characterization of the dosimeters for CT scans in phantom, including evaluations of depletion, fading, angular dependence, and conversion from counts to absorbed dose; (2) evaluation of the efficacy of using plastic glasses to position themore » dosimeters over the eyes in both phantom and clinical studies; and (3) preliminary dosimetry measurements made using organ-based tube current modulation in computed tomography dose index (CTDI) and anthropomorphic phantom studies. Results: (1) Depletion effects were found to have a linear relationship with the output of the OSL dosimeters (R{sup 2} = 0.96). Fading was found to affect dosimeter readings during the first two hours following exposure but had no effect during the remaining 60-h period observed. No significant angular dependence was observed for the exposure conditions used in this study (with p-values ranging from 0.9 to 0.26 for all t-tests). Dosimeter counts varied linearly with absorbed dose when measured in the center and 12 o’clock positions of the CTDI phantoms. These linear models of counts versus absorbed dose had overlapping 95% confidence intervals for the intercepts but not for the slopes. (2) When dosimeters were positioned using safety glasses, there was no adverse effect on image quality, and there was no statistically significant difference between this placement and placement of the dosimeters directly on the eyes of the phantom (p = 0.24). (3) When using organ-based tube current modulation, the dose to the lens of the eye was reduced between 19% and 43%, depending on the scan protocol used and the positioning of the phantom. Furthermore, the amount of dose reduction was significantly affected by the vertical position of the phantom, with the largest reduction in dose seen when the phantom was centered in the gantry. Conclusions: (1) An appropriate correction factor, specific to CT scanning, was developed to account for depletion and fading characteristics of the dosimeters. Additionally, an equation to convert dosimeter counts to absorbed dose was established. (2) The use of plastic safety glasses was validated as an appropriate positioning device when measuring dose to the lens of the eye. (3) The use of organ-based tube current modulation can reduce dose to the lens of the eye during CT scanning. The amount of dose reduction, however, is largely influenced by the positioning of the anatomy in the gantry.« less

Characterization and implementation of OSL dosimeters for use in evaluating the efficacy of organ-based tube current modulation for CT scans of the face and orbits.

PubMed

Marsh, R M; Silosky, M

2015-04-01

The purpose of this work was to characterize commercially available optically stimulated luminescent (OSL) dosimeters for general clinical applications and apply the results to the development of a method to evaluate the efficacy of a vendor-specific organ-based tube current modulation application for both phantom and clinical computed tomography (CT) scans of the face and orbits. This study consisted of three components: (1) thorough characterization of the dosimeters for CT scans in phantom, including evaluations of depletion, fading, angular dependence, and conversion from counts to absorbed dose; (2) evaluation of the efficacy of using plastic glasses to position the dosimeters over the eyes in both phantom and clinical studies; and (3) preliminary dosimetry measurements made using organ-based tube current modulation in computed tomography dose index (CTDI) and anthropomorphic phantom studies. (1) Depletion effects were found to have a linear relationship with the output of the OSL dosimeters (R(2) = 0.96). Fading was found to affect dosimeter readings during the first two hours following exposure but had no effect during the remaining 60-h period observed. No significant angular dependence was observed for the exposure conditions used in this study (with p-values ranging from 0.9 to 0.26 for all t-tests). Dosimeter counts varied linearly with absorbed dose when measured in the center and 12 o'clock positions of the CTDI phantoms. These linear models of counts versus absorbed dose had overlapping 95% confidence intervals for the intercepts but not for the slopes. (2) When dosimeters were positioned using safety glasses, there was no adverse effect on image quality, and there was no statistically significant difference between this placement and placement of the dosimeters directly on the eyes of the phantom (p = 0.24). (3) When using organ-based tube current modulation, the dose to the lens of the eye was reduced between 19% and 43%, depending on the scan protocol used and the positioning of the phantom. Furthermore, the amount of dose reduction was significantly affected by the vertical position of the phantom, with the largest reduction in dose seen when the phantom was centered in the gantry. (1) An appropriate correction factor, specific to CT scanning, was developed to account for depletion and fading characteristics of the dosimeters. Additionally, an equation to convert dosimeter counts to absorbed dose was established. (2) The use of plastic safety glasses was validated as an appropriate positioning device when measuring dose to the lens of the eye. (3) The use of organ-based tube current modulation can reduce dose to the lens of the eye during CT scanning. The amount of dose reduction, however, is largely influenced by the positioning of the anatomy in the gantry.

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.

EYE LENS DOSIMETRY FOR FLUOROSCOPICALLY GUIDED CLINICAL PROCEDURES: PRACTICAL APPROACHES TO PROTECTION AND DOSE MONITORING.

PubMed

Martin, Colin J

2016-06-01

Doses to the eye lenses of clinicians undertaking fluoroscopically guided procedures can exceed the dose annual limit of 20 mSv, so optimisation of radiation protection is essential. Ceiling-suspended shields and disposable radiation absorbing pads can reduce eye dose by factors of 2-7. Lead glasses that shield against exposures from the side can lower doses by 2.5-4.5 times. Training in effective use of protective devices is an essential element in achieving good protection and acceptable eye doses. Effective methods for dose monitoring are required to identify protection issues. Dosemeters worn adjacent to the eye provide the better option for interventional clinicians, but an unprotected dosemeter worn at the neck will give an indication of eye dose that is adequate for most interventional staff. Potential requirements for protective devices and dose monitoring can be determined from risk assessments using generic values for dose linked to examination workload. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Simulation of computed tomography dose based on voxel phantom

NASA Astrophysics Data System (ADS)

Liu, Chunyu; Lv, Xiangbo; Li, Zhaojun

2017-01-01

Computed Tomography (CT) is one of the preferred and the most valuable imaging tool used in diagnostic radiology, which provides a high-quality cross-sectional image of the body. It still causes higher doses of radiation to patients comparing to the other radiological procedures. The Monte-Carlo method is appropriate for estimation of the radiation dose during the CT examinations. The simulation of the Computed Tomography Dose Index (CTDI) phantom was developed in this paper. Under a similar conditions used in physical measurements, dose profiles were calculated and compared against the measured values that were reported. The results demonstrate a good agreement between the calculated and the measured doses. From different CT exam simulations using the voxel phantom, the highest absorbed dose was recorded for the lung, the brain, the bone surface. A comparison between the different scan type shows that the effective dose for a chest scan is the highest one, whereas the effective dose values during abdomen and pelvis scan are very close, respectively. The lowest effective dose resulted from the head scan. Although, the dose in CT is related to various parameters, such as the tube current, exposure time, beam energy, slice thickness and patient size, this study demonstrates that the MC simulation is a useful tool to accurately estimate the dose delivered to any specific organs for patients undergoing the CT exams and can be also a valuable technique for the design and the optimization of the CT x-ray source.

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.

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.

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.

Red marrow and blood dosimetry in 131I treatment of metastatic thyroid carcinoma: pre-treatment versus in-therapy results

NASA Astrophysics Data System (ADS)

Giostra, A.; Richetta, E.; Pasquino, M.; Miranti, A.; Cutaia, C.; Brusasco, G.; Pellerito, R. E.; Stasi, M.

2016-06-01

Treatment with radioiodine is a standard procedure for patients with well-differentiated thyroid cancer, but the main approach to the therapy is still empiric, consisting of the administration of fixed activities. A predictive individualized dosimetric study may represent an important tool for physicians to determine the best activity to prescribe. The aim of this work is to compare red marrow and blood absorbed dose values obtained in the pre-treatment (PT) dosimetry phase with those obtained in the in-treatment (IT) dosimetry phase in order to estimate the predictive power of PT trial doses and to determine if they can be used as a decision-making tool to safely administer higher 131I activity to potentially increase the efficacy of treatment. The PT and IT dosimetry for 50 patients has been evaluated using three different dosimetric approaches. In all three approaches blood and red marrow doses, are calculated as the sum of two components, the dose from 131I activity in the blood and the dose from 131I activity located in the remainder of the body (i.e. the blood and whole-body contributions to the total dose). PT and IT dose values to blood and red marrow appear to be well correlated irrespective of the dosimetric approach used. Linear regression analyses of PT and IT total doses, for blood and red marrow, and the whole-body contribution to these doses, showed consistent best fit slope and correlation coefficient values of approximately 0.9 and 0.6, respectively: analyses of the blood dose contribution to the total doses also yielded similar values for the best fit slope but with correlation coefficient values of approximately 0.4 reflecting the greater variance in these dose estimates. These findings suggest that pre-treatment red marrow dose assessments may represent an important tool to personalize metastatic thyroid cancer treatment, removing the constraints of a fixed activity approach and permitting potentially more effective higher 131I activities to be safely used in-treatment.

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

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.

Human exposure to large solar particle events in space

NASA Technical Reports Server (NTRS)

Townsend, L. W.; Wilson, J. W.; Shinn, J. L.; Curtis, S. B.

1992-01-01

Whenever energetic solar protons produced by solar particle events traverse bulk matter, they undergo various nuclear and atomic collision processes which significantly alter the physical characteristics and biologically important properties of their transported radiation fields. These physical interactions and their effect on the resulting radiation field within matter are described within the context of a recently developed deterministic, coupled neutron-proton space radiation transport computer code (BRYNTRN). Using this computer code, estimates of human exposure in interplanetary space, behind nominal (2 g/sq cm) and storm shelter (20 g/sq cm) thicknesses of aluminum shielding, are made for the large solar proton event of August 1972. Included in these calculations are estimates of cumulative exposures to the skin, ocular lens, and bone marrow as a function of time during the event. Risk assessment in terms of absorbed dose and dose equivalent is discussed for these organs. Also presented are estimates of organ exposures for hypothetical, worst-case flare scenarios. The rate of dose equivalent accumulation places this situation in an interesting region of dose rate between the very low values of usual concern in terrestrial radiation environments and the high-dose-rate values prevalent in radiation therapy.

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

New Radiation Dosimetry Estimates for [18F]FLT based on Voxelized Phantoms.

PubMed

Mendes, B M; Ferreira, A V; Nascimento, L T C; Ferreira, S M Z M D; Silveira, M B; Silva, J B

2018-04-25

3'-Deoxy-3-[ 18 F]fluorothymidine, or [ 18 F]FLT, is a positron emission tomography (PET) tracer used in clinical studies for noninvasive assessment of proliferation activity in several types of cancer. Although the use of this PET tracer is expanding, to date, few studies concerning its dosimetry have been published. In this work, new [ 18 F]FLT dosimetry estimates are determined for human and mice using Monte Carlo simulations. Modern voxelized male and female phantoms and [ 18 F]FLT biokinetic data, both published by the ICRP, were used for simulations of human cases. For most human organs/tissues the absorbed doses were higher than those reported in ICRP Publication 128. An effective dose of 1.70E-02 mSv/MBq to the whole body was determined, which is 13.5% higher than the ICRP reference value. These new human dosimetry estimates obtained using more realistic human phantoms represent an advance in the knowledge of [ 18 F]FLT dosimetry. In addition, mice biokinetic data were obtained experimentally. These data and a previously developed voxelized mouse phantom were used for simulations of animal cases. Concerning animal dosimetry, absorbed doses for organs/tissues ranged from 4.47 ± 0.75 to 155.74 ± 59.36 mGy/MBq. The obtained set of organ/tissue radiation doses for healthy Swiss mice is a useful tool for application in animal experiment design.

COMPILATION OF CONVERSION COEFFICIENTS FOR THE DOSE TO THE LENS OF THE EYE.

PubMed

Behrens, R

2017-04-28

A compilation of fluence-to-absorbed dose conversion coefficients for the dose to the lens of the eye is presented. The compilation consists of both previously published data and newly calculated values: photon data (5 keV-50 MeV for both kerma approximation and full electron transport), electron data (10 keV-50 MeV), and positron data (1 keV-50 MeV) - neutron data will be published separately. Values are given for angles of incidence from 0° up to 90° in steps of 15° and for rotational irradiation. The data presented can be downloaded from this article's website and they are ready for use by Report Committee (RC) 26. This committee has been set up by the International Commission on Radiation Units and Measurements (ICRU) and is working on a 'proposal for a redefinition of the operational quantities for external radiation exposure'. © The Author 2016. Published by Oxford University Press.

Air kerma calibration factors and chamber correction values for PTW soft x-ray, NACP and Roos ionization chambers at very low x-ray energies.

PubMed

Ipe, N E; Rosser, K E; Moretti, C J; Manning, J W; Palmer, M J

2001-08-01

This paper evaluates the characteristics of ionization chambers for the measurement of absorbed dose to water using very low-energy x-rays. The values of the chamber correction factor, k(ch), used in the IPEMB 1996 code of practice for the UK secondary standard ionization chambers (PTW type M23342 and PTW type M23344), the Roos (PTW type 34001) and NACP electron chambers are derived. The responses in air of the small and large soft x-ray chambers (PTW type M23342 and PTW type M23344) and the NACP and Roos electron ionization chambers were compared. Besides the soft x-ray chambers, the NACP and Roos chambers can be used for very low-energy x-ray dosimetry provided that they are used in the restricted energy range for which their response does not change by more than 5%. The chamber correction factor was found by comparing the absorbed dose to water determined using the dosimetry protocol recommended for low-energy x-rays with that for very low-energy x-rays. The overlap energy range was extended using data from Grosswendt and Knight. Chamber correction factors given in this paper are chamber dependent, varying from 1.037 to 1.066 for a PTW type M23344 chamber, which is very different from a value of unity given in the IPEMB code. However, the values of k(ch) determined in this paper agree with those given in the DIN standard within experimental uncertainty. The authors recommend that the very low-energy section of the IPEMB code is amended to include the most up-to-date values of k(ch).

A pragmatic approach to determine the optimal kVp in cone beam CT: balancing contrast-to-noise ratio and radiation dose

PubMed Central

Silkosessak, O; Jacobs, R; Bogaerts, R; Bosmans, H; Panmekiate, S

2014-01-01

Objectives: To determine the optimal kVp setting for a particular cone beam CT (CBCT) device by maximizing technical image quality at a fixed radiation dose. Methods: The 3D Accuitomo 170 (J. Morita Mfg. Corp., Kyoto, Japan) CBCT was used. The radiation dose as a function of kVp was measured in a cylindrical polymethyl methacrylate (PMMA) phantom using a small-volume ion chamber. Contrast-to-noise ratio (CNR) was measured using a PMMA phantom containing four materials (air, aluminium, polytetrafluoroethylene and low-density polyethylene), which was scanned using 180 combinations of kVp/mA, ranging from 60/1 to 90/8. The CNR was measured for each material using PMMA as background material. The pure effect of kVp and mAs on the CNR values was analysed. Using a polynomial fit for CNR as a function of mA for each kVp value, the optimal kVp was determined at five dose levels. Results: Absorbed doses ranged between 0.034 mGy mAs−1 (14 × 10 cm, 60 kVp) and 0.108 mGy mAs−1 (14 × 10 cm, 90 kVp). The relation between kVp and dose was quasilinear (R2 > 0.99). The effect of mA and kVp on CNR could be modelled using a second-degree polynomial. At a fixed dose, there was a tendency for higher CNR values at increasing kVp values, especially at low dose levels. A dose reduction through mA was more efficient than an equivalent reduction through kVp in terms of image quality deterioration. Conclusions: For the investigated CBCT model, the most optimal contrast at a fixed dose was found at the highest available kVp setting. There is great potential for dose reduction through mA with a minimal loss in image quality. PMID:24708447

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.

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.

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

Biodistribution and Radiation Dosimetry of the Integrin Marker 64Cu-BaBaSar-RGD2 Determined from Whole-Body PET/CT in a Non-Human Primate

NASA Astrophysics Data System (ADS)

Liu, Shuanglong; Vorobyova, Ivetta; Park, Ryan; Conti, Peter S.

2017-10-01

Introduction: 64Cu-BaBaSar-RGD2 is a positron emission radiotracer taken up by integrin αvβ3, which is overexpressed in many malignancies. The aim of this study was to evaluate the biodistribution of 64Cu-BaBaSar-RGD2 in a non-human primate with positron emission tomography and to estimate the absorbed doses in major organs for human. Materials and methods: Whole-body PET imaging was done in a Siemens Biograph scanner in a male macaque monkey. After an i.v. injection of 13.1–19.7 MBq/kg of 64Cu-BaBaSar-RGD2, whole body scan was collected for a total duration of 180 min. Attenuation and scatter corrections were applied to reconstruction of the whole-body emission scan. After image reconstruction, three-dimensional volumes of interest (VOI) were hand-drawn on the PET transaxial or coronal slices of the frame where the organ was most conspicuous. Time-activity curves for each VOI were obtained, and residence time of each organ was calculated by integration of the time-activity curves. Human absorbed doses were estimated using the standard human model in OLINDA/EXM software. Results: Injection of 64Cu-BaBaSar-RGD2 was well tolerated in the macaque monkey, with no serious tracer-related adverse events observed. 64Cu-BaBaSar-RGD2 was cleared rapidly from the blood pool, with a 12.1-min biological half-time. Increased 64Cu-BaBaSar-RGD2 uptake was observed in the kidneys, and bladder, with mean percentage injected dose (ID%) values at 1 h after injection approximately 35.50 ± 6.47 and 36.89 ± 5.48, respectively. The calculated effective dose was 15.30 ± 2.21 µSv/MBq, and the kidneys had the highest absorbed dose at 108.43 ± 16.41 µGy/MBq using the non-voiding model. For an injected activity of 925 MBq 64Cu for human, the effective dose would be 14.2 ± 2.1 mSv. Discussion: Due to the limitation of the monkey number, we evaluated 64Cu-BaBaSar-RGD2 in the same monkey of three imaging sessions. Measured absorbed doses and effective doses of 64Cu-BaBaSar-RGD2 are comparable to other reported RGD-derived radiopharmaceuticals labeled with 64Cu and 18F. Therefore, 64Cu-BaBaSar-RGD2 can be safely injected into humans for studying integrin αvβ3 expression non-invasively.

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.

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.

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.

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.

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.

An analytical model of leakage neutron equivalent dose for passively-scattered proton radiotherapy and validation with measurements.

PubMed

Schneider, Christopher; Newhauser, Wayne; Farah, Jad

2015-05-18

Exposure to stray neutrons increases the risk of second cancer development after proton therapy. Previously reported analytical models of this exposure were difficult to configure and had not been investigated below 100 MeV proton energy. The purposes of this study were to test an analytical model of neutron equivalent dose per therapeutic absorbed dose  at 75 MeV and to improve the model by reducing the number of configuration parameters and making it continuous in proton energy from 100 to 250 MeV. To develop the analytical model, we used previously published H/D values in water from Monte Carlo simulations of a general-purpose beamline for proton energies from 100 to 250 MeV. We also configured and tested the model on in-air neutron equivalent doses measured for a 75 MeV ocular beamline. Predicted H/D values from the analytical model and Monte Carlo agreed well from 100 to 250 MeV (10% average difference). Predicted H/D values from the analytical model also agreed well with measurements at 75 MeV (15% average difference). The results indicate that analytical models can give fast, reliable calculations of neutron exposure after proton therapy. This ability is absent in treatment planning systems but vital to second cancer risk estimation.

Crystal-liquid Fugacity Ratio as a Surrogate Parameter for Intestinal Permeability.

PubMed

Zakeri-Milani, Parvin; Fasihi, Zohreh; Akbari, Jafar; Jannatabadi, Ensieh; Barzegar-Jalali, Mohammad; Loebenberg, Raimar; Valizadeh, Hadi

We assessed the feasibility of using crystal-liquid fugacity ratio (CLFR) as an alternative parameter for intestinal permeability in the biopharmaceutical classification (BCS) of passively absorbed drugs. Dose number, fraction of dose absorbed, intestinal permeability, and intrinsic dissolution rate were used as the input parameters. CLFR was determined using thermodynamic parameters i.e., melting point, molar fusion enthalpy, and entropy of drug molecules obtained using differential scanning calorimetry. The CLFR values were in the range of 0.06-41.76 mole percent. There was a close relationship between CLFR and in vivo intestinal permeability (r > 0.8). CLFR values of greater than 2 mole percent corresponded to complete intestinal absorption. Applying CLFR versus dose number or intrinsic dissolution rate, more than 92% of tested drugs were correctly classified with respect to the reported classification system on the basis of human intestinal permeability and solubility. This investigation revealed that the CLFR might be an appropriate parameter for quantitative biopharmaceutical classification. This could be attributed to the fact that CLFR could be a measure of solubility of compounds in lipid bilayer which was found in this study to be directly proportional to the intestinal permeability of compounds. This classification enables researchers to define characteristics for intestinal absorption of all four BCS drug classes using suitable cutoff points for both intrinsic dissolution rate and crystal-liquid fugacity ratio. Therefore, it may be used as a surrogate for permeability studies. This article is open to POST-PUBLICATION REVIEW. Registered readers (see "For Readers") may comment by clicking on ABSTRACT on the issue's contents page.

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.

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.

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.

Clinical in vivo dosimetry using optical fibers.

PubMed

Gripp, S; Haesing, F W; Bueker, H; Schmitt, G

1998-01-01

Discoloring of glass due to ionizing radiation depends on the absorbed dose. The radiation-induced light attenuation in optical fibers may be used as a measure of the dose. In high-energy photon beams (6 MV X rays), a lead-doped silica fiber can be calibrated. A dosimeter based on an optical fiber was developed for applications in radiation therapy. The diameter of the mounted fiber is 0.25 mm, whereas the length depends on the sensitivity required. To demonstrate the applicability, a customized fiber device was used to determine scattered radiation close to the lens of the eye. Measurements were compared with TLDs (LiF) in an anthropomorphic phantom. The comparison with TLD measurements shows good agreement. In contrast to TLD, optical fibers provide immediate dose values, and the readout procedure is much easier. Owing to its small size and diameter, interesting invasive dose measurements are feasible.

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.

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

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.

Optimization of reaction parameters of radiation induced grafting of 1-vinylimidazole onto poly(ethylene-co-tetraflouroethene) using response surface method

NASA Astrophysics Data System (ADS)

Nasef, Mohamed Mahmoud; Aly, Amgad Ahmed; Saidi, Hamdani; Ahmad, Arshad

2011-11-01

Radiation induced grafting of 1-vinylimidazole (1-VIm) onto poly(ethylene-co-tetraflouroethene) (ETFE) was investigated. The grafting parameters such as absorbed dose, monomer concentration, grafting time and temperature were optimized using response surface method (RSM). The Box-Behnken module available in the design expert software was used to investigate the effect of reaction conditions (independent parameters) varied in four levels on the degree of grafting ( G%) (response parameter). The model yielded a polynomial equation that relates the linear, quadratic and interaction effects of the independent parameters to the response parameter. The analysis of variance (ANOVA) was used to evaluate the results of the model and detect the significant values for the independent parameters. The optimum parameters to achieve a maximum G% were found to be monomer concentration of 55 vol%, absorbed dose of 100 kGy, time in the range of 14-20 h and a temperature of 61 °C. Fourier transform infrared (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to investigate the properties of the obtained films and provide evidence for grafting.

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.

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

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.

Variability of surface and center position radiation dose in MDCT: Monte Carlo simulations using CTDI and anthropomorphic phantoms

PubMed Central

Zhang, Di; Savandi, Ali S.; Demarco, John J.; Cagnon, Chris H.; Angel, Erin; Turner, Adam C.; Cody, Dianna D.; Stevens, Donna M.; Primak, Andrew N.; McCollough, Cynthia H.; McNitt-Gray, Michael F.

2009-01-01

The larger coverage afforded by wider z-axis beams in multidetector CT (MDCT) creates larger cone angles and greater beam divergence, which results in substantial surface dose variation for helical and contiguous axial scans. This study evaluates the variation of absorbed radiation dose in both cylindrical and anthropomorphic phantoms when performing helical or contiguous axial scans. The approach used here was to perform Monte Carlo simulations of a 64 slice MDCT. Simulations were performed with different radiation profiles (simulated beam widths) for a given collimation setting (nominal beam width) and for different pitch values and tube start angles. The magnitude of variation at the surface was evaluated under four different conditions: (a) a homogeneous CTDI phantom with different combinations of pitch and simulated beam widths, (b) a heterogeneous anthropomorphic phantom with one measured beam collimation and various pitch values, (c) a homogeneous CTDI phantom with fixed beam collimation and pitch, but with different tube start angles, and (d) pitch values that should minimize variations of surface dose—evaluated for both homogeneous and heterogeneous phantoms. For the CTDI phantom simulations, peripheral dose patterns showed variation with percent ripple as high as 65% when pitch is 1.5 and simulated beam width is equal to the nominal collimation. For the anterior surface dose on an anthropomorphic phantom, the percent ripple was as high as 40% when the pitch is 1.5 and simulated beam width is equal to the measured beam width. Low pitch values were shown to cause beam overlaps which created new peaks. Different x-ray tube start angles create shifts of the peripheral dose profiles. The start angle simulations showed that for a given table position, the surface dose could vary dramatically with minimum values that were 40% of the peak when all conditions are held constant except for the start angle. The last group of simulations showed that an “ideal” pitch value can be determined which reduces surface dose variations, but this pitch value must take into account the measured beam width. These results reveal the complexity of estimating surface dose and demonstrate a range of dose variability at surface positions for both homogeneous cylindrical and heterogeneous anthropomorphic phantoms. These findings have potential implications for small-sized dosimeter measurements in phantoms, such as with TLDs or small Farmer chambers. PMID:19378763

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.

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.

Dosimetry applications in GATE Monte Carlo toolkit.

PubMed

Papadimitroulas, Panagiotis

2017-09-01

Monte Carlo (MC) simulations are a well-established method for studying physical processes in medical physics. The purpose of this review is to present GATE dosimetry applications on diagnostic and therapeutic simulated protocols. There is a significant need for accurate quantification of the absorbed dose in several specific applications such as preclinical and pediatric studies. GATE is an open-source MC toolkit for simulating imaging, radiotherapy (RT) and dosimetry applications in a user-friendly environment, which is well validated and widely accepted by the scientific community. In RT applications, during treatment planning, it is essential to accurately assess the deposited energy and the absorbed dose per tissue/organ of interest, as well as the local statistical uncertainty. Several types of realistic dosimetric applications are described including: molecular imaging, radio-immunotherapy, radiotherapy and brachytherapy. GATE has been efficiently used in several applications, such as Dose Point Kernels, S-values, Brachytherapy parameters, and has been compared against various MC codes which are considered as standard tools for decades. Furthermore, the presented studies show reliable modeling of particle beams when comparing experimental with simulated data. Examples of different dosimetric protocols are reported for individualized dosimetry and simulations combining imaging and therapy dose monitoring, with the use of modern computational phantoms. Personalization of medical protocols can be achieved by combining GATE MC simulations with anthropomorphic computational models and clinical anatomical data. This is a review study, covering several dosimetric applications of GATE, and the different tools used for modeling realistic clinical acquisitions with accurate dose assessment. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

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.

Intervention effects of five cations and their correction on hemolytic activity of tentacle extract from the jellyfish Cyanea capillata

PubMed Central

2017-01-01

Cations have generally been reported to prevent jellyfish venom-induced hemolysis through multiple mechanisms by spectrophotometry. Little attention has been paid to the potential interaction between cations and hemoglobin, potentially influencing the antagonistic effect of cations. Here, we explored the effects of five reported cations, La3+, Mn2+, Zn2+, Cu2+ and Fe2+, on a hemolytic test system and the absorbance of hemoglobin, which was further used to measure their effects on the hemolysis of tentacle extract (TE) from the jellyfish Cyanea capillata. All the cations displayed significant dose-dependent inhibitory effects on TE-induced hemolysis with various dissociation equilibrium constant (Kd) values as follows: La3+ 1.5 mM, Mn2+ 93.2 mM, Zn2+ 38.6 mM, Cu2+ 71.9 μM and Fe2+ 32.8 mM. The transparent non-selective pore blocker La3+ did not affect the absorbance of hemoglobin, while Mn2+ reduced it slightly. Other cations, including Zn2+, Cu2+ and Fe2+, greatly decreased the absorbance with Kd values of 35.9, 77.5 and 17.6 mM, respectively. After correction, the inhibitory Kd values were 1.4 mM, 45.8 mM, 128.5 μM and 53.1 mM for La3+, Zn2+, Cu2+ and Fe2+, respectively. Mn2+ did not inhibit TE-induced hemolysis. Moreover, the inhibitory extent at the maximal given dose of all cations except La3+ was also diminished. These corrected results from spectrophotometry were further confirmed by direct erythrocyte counting under microscopy. Our results indicate that the cations, except for La3+, can interfere with the absorbance of hemoglobin, which should be corrected when their inhibitory effects on hemolysis by jellyfish venoms are examined. The variation in the inhibitory effects of cations suggests that the hemolysis by jellyfish venom is mainly attributed to the formation of non-selective cation pore complexes over other potential mechanisms, such as phospholipases A2 (PLA2), polypeptides, protease and oxidation. Blocking the pore-forming complexes may be a primary strategy to improve the in vivo damage and mortality from jellyfish stings due to hemolytic toxicity. PMID:28503385

Evaluation of [18F]Mefway biodistribution and dosimetry based on whole-body PET imaging of mice.

PubMed

Constantinescu, Cristian C; Sevrioukov, Evgueni; Garcia, Adriana; Pan, Min-Liang; Mukherjee, Jogeshwar

2013-04-01

[(18)F]Mefway is a novel radiotracer specific to the serotonin 5-HT1A receptor class. In preparation for using this tracer in humans, we have performed whole-body PET studies in mice to evaluate the biodistribution and dosimetry of [(18)F]Mefway. Six mice (three females and three males) received IV injections of [(18)F]Mefway and were scanned for 2 h in an Inveon-dedicated PET scanner. Each animal also received a high-resolution CT scan using an Inveon CT. The CT images were used to draw volume of interest on the following organs: the brain, large intestine, stomach, heart, kidneys, liver, lungs, pancreas, bone, spleen, testes, thymus, gallbladder, uterus, and urinary bladder. All organ time-activity curves without decay correction were normalized to the injected activity. The area under the normalized curves was then used to compute the residence times in each organ. Data were analyzed using PMOD and Matlab software. The absorbed doses in mouse organs were computed using the RAdiation Dose Assessment Resource animal models for dose assessment. The residence times in mouse organs were converted to human values using scale factors based on differences between organ and body weights. OLINDA/EXM 1.1 software was used to compute the absorbed human doses in multiple organs for both female and male phantoms. The highest mouse residence times were found in the liver, urinary bladder, and kidneys. The largest doses in mice were found in the urinary bladder (critical organ), kidney, and liver for both females and males, indicating primary elimination via urinary system. The projected human effective doses were 1.21E - 02 mSv/MBq for the adult female model and 1.13E - 02 mSv/MBq for the adult male model. The estimated human biodistribution of [(18)F]Mefway was similar to that of [(11)C]WAY 100,635, a 5-HT1A tracer for which dosimetry has been evaluated in humans. The elimination of radiotracer was primarily via the kidney and urinary bladder with the urinary bladder being the critical organ. Whole-body mouse imaging can be used as a preclinical tool to provide initial estimates of the absorbed doses of [(18)F]Mefway in humans.

MO-FG-CAMPUS-IeP1-05: New Ionization Chamber Dosimetry of Absorbed Dose to Water in Diagnostic KV X-Ray Beams

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

Araki, F; Ohno, T

Purpose: To develop new ionization chamber dosimetry of absorbed dose to water in diagnostic kV x-ray beams, by using a beam quality conversion factor, kQ, for Co-60 to kV x-ray and an ionization conversion factor for a water-substitute plastic phantom. Methods: kQ was calculated for aluminum half value-layers (Al-HVLs) of 1.5 mm to 8 mm which were generated by kV x-ray beams of 50 to 120 kVp. Twenty-two energy spectra for ten effective energies (Eeff) were calculated by a SpecCalc program. Depth doses in water were calculated at 5 × 5 to 30 × 30 cm{sup 2} fields. Output factorsmore » were also obtained from the dose ratio for a 10 × 10 cm{sup 2} field. kQ was obtained for a PTW30013 Former ion chamber. In addition, an ionization conversion factor of the PWDT phantom to water was calculated. All calculations were performed with EGSnrc/cavity code and egs-chamber codes. Results: The x-ray beam energies for 1.5 mm to 8 mm Al-HVLs ranged in Eeff of 25.7 to 54.3 keV. kQ for 1.5 mm to 8 mm Al-HVLs were 0.831 to 0.897, at 1 and 2 cm depths for a 10 × 10 cm2 field. Similarly, output factors for 5 × 5 to 30 × 30 cm{sup 2} fields were 0.937 to 1.033 for 25.7 keV and 0.857 to 1.168 for 54.3 keV. The depth dose in a PWDT phantom decreased up to 5% compared to that in water at depth of ten percent of maximum dose for 1.5 mm Al-HVL. The ionization ratios of water/PWDT phantoms for the PTW30013 chamber were 1.012 to 1.007 for 1.5 mm to 8 mm Al-HVLs at 1 cm depth. Conclusion: It became possible to directly measure the absorbed dose to water with the ionization chamber in diagnostic kV x-ray beams, by using kQ and the PWDT phantom.« less

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).

Gamma Radiation Dose Rate in Air due to Terrestrial Radionuclides in Southern Brazil: Synthesis by Geological Units and Lithotypes Covered by the Serra do Mar Sul Aero-Geophysical Project

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

Bastos, Rodrigo O.; Appoloni, Carlos R.; Pinese, Jose P. P.

2008-08-07

The absorbed dose rates in air due to terrestrial radionuclides were estimated from aerial gamma spectrometric data for an area of 48,600 km{sup 2} in Southern Brazil. The source data was the Serra do Mar Sul Aero-Geophysical Project back-calibrated in a cooperative work among the Geological Survey of Brazil, the Geological Survey of Canada, and Paterson, Grant and Watson Ltd. The concentrations of eU (ppm), eTh (ppm) and K (%) were converted to dose rates in air (nGy{center_dot}h{sup -1}) by accounting for the contribution of each element's concentration. Regional variation was interpreted according to lithotypes and a synthesis was performedmore » according to the basic geological units present in the area. Higher values of total dose were estimated for felsic igneous and metamorphic rocks, with average values varying up to 119{+-}24 nGy{center_dot}h{sup -1}, obtained by Anitapolis syenite body. Sedimentary, metasedimentary and metamafic rocks presented the lower dose levels, and some beach deposits reached the lowest average total dose, 18.5{+-}8.2 nGy{center_dot}h{sup -1}. Thorium gives the main average contribution in all geological units, the highest value being reached by the nebulitic gneisses of Atuba Complex, 71{+-}23 nGy{center_dot}h{sup -1}. Potassium presents the lowest average contribution to dose rate in 53 of the 72 units analyzed, the highest contribution being obtained by intrusive alkaline bodies (28{+-}12 nGy{center_dot}h{sup -1}). The general pattern of geographic dose distribution respects well the hypotheses on geo-physicochemical behavior of radioactive elements.« less

Electrosynthesis of magnetoresponsive microrobot for targeted drug delivery using calcium alginate.

PubMed

Chengzhi Hu; Riederer, Katharina; Klemmer, Michael; Pane, Salvador; Nelson, Bradley J

2016-08-01

Targeted drug delivery systems deliver drugs precisely to a specific targeted site inside the body, and can also release the drugs with controlled kinetics to prolong the efficacy of single dose administration. The advantageous properties of hydrogels make them attractive for use in the area of drug delivery. Calcium alginate is a pH sensitive hydrogel stable in acidic media and soluble in basic media. This enables the hydrogel to absorb and release aqueous solutions at certain ranges of pH values. By absorbing an aqueous solution containing a drug, an active drug release can be triggered at a specified range of pH value. In this paper, we combined calcium alginate with cobalt nickel (CoNi) in a cylindrical hybrid micro robot by electrodeposition. The designed microrobot can be wirelessly actuated with an external magnetic manipulation system and, hence, targeted to a specific location in the human body. At this specific location, characterized by its pH range, the absorbed drug will be released. Here, the fabrication steps of the specified microrobot are characterized, namely the production of a template on a silicon chip and the subsequent template-assisted electrodeposition of CoNi and alginate. Additionally, the dynamics of drug release of calcium alginate is studied.

Characterization of low temperature metallic magnetic calorimeters having gold absorbers with implanted 163Ho ions

NASA Astrophysics Data System (ADS)

Gastaldo, L.; Ranitzsch, P. C.-O.; von Seggern, F.; Porst, J.-P.; Schäfer, S.; Pies, C.; Kempf, S.; Wolf, T.; Fleischmann, A.; Enss, C.; Herlert, A.; Johnston, K.

2013-05-01

For the first time we have investigated the behavior of fully micro-fabricated low temperature metallic magnetic calorimeters (MMCs) after undergoing an ion-implantation process. This experiment had the aim to show the possibility to perform a high precision calorimetric measurement of the energy spectrum following the electron capture of 163Ho using MMCs having the radioactive 163Ho ions implanted in the absorber. The isotope 163Ho decays through electron capture to 163Dy and features the smallest known QEC value. This peculiarity makes 163Ho a very interesting candidate to investigate the value of the electron neutrino mass by the analysis of the energy spectrum. The implantation of 163Ho ions was performed at ISOLDE-CERN. The performance of a detector that underwent an ion-implantation process is compared to the one of a detector without implanted ions. The results show that the implantation dose of ions used in this experiment does not compromise the properties of the detector. Moreover the performance of the detector prototype having the 163Ho ions implanted in the absorber is already close to the requirements needed for an experiment with sub-eV sensitivity to the electron neutrino mass. Based on these results, an optimized detector design for future 163Ho experiments is presented.

Reduction in radiation dose with reconstruction technique in the brain perfusion CT

NASA Astrophysics Data System (ADS)

Kim, H. J.; Lee, H. K.; Song, H.; Ju, M. S.; Dong, K. R.; Chung, W. K.; Cho, M. S.; Cho, J. H.

2011-12-01

The principal objective of this study was to verify the utility of the reconstruction imaging technique in the brain perfusion computed tomography (PCT) scan by assessing reductions in the radiation dose and analyzing the generated images. The setting used for image acquisition had a detector coverage of 40 mm, a helical thickness of 0.625 mm, a helical shuttle mode scan type and a rotation time of 0.5 s as the image parameters used for the brain PCT scan. Additionally, a phantom experiment and an animal experiment were carried out. In the phantom and animal experiments, noise was measured in the scanning with the tube voltage fixed at 80 kVp (kilovolt peak) and the level of the adaptive statistical iterative reconstruction (ASIR) was changed from 0% to 100% at 10% intervals. The standard deviation of the CT coefficient was measured three times to calculate the mean value. In the phantom and animal experiments, the absorbed dose was measured 10 times under the same conditions as the ones for noise measurement before the mean value was calculated. In the animal experiment, pencil-type and CT-dedicated ionization chambers were inserted into the central portion of pig heads for measurement. In the phantom study, as the level of the ASIR changed from 0% to 100% under identical scanning conditions, the noise value and dose were proportionally reduced. In our animal experiment, the noise value was lowest when the ASIR level was 50%, unlike in the phantom study. The dose was reduced as in the phantom study.

Changes in growth and antioxidant status of alfalfa sprouts during sprouting as affected by gamma irradiation of seeds.

PubMed

Fan, Xuetong; Thayer, Donald W; Sokorai, Kimberly J B

2004-03-01

Viking 3000 alfalfa seeds irradiated with gamma rays to doses of 0, 1, 2, 3, or 4 kGy were sprouted and allowed to grow for up to 8 days at 23 degrees C. Germination, growth (yield and length), antioxidant capacity, and ascorbic acid (AA) were measured during sprouting. Results showed percent germination of the seeds and the rates of growth of the sprouts were inversely related to the radiation dose absorbed by the seeds. Both antioxidant capacity and AA content expressed on a fresh weight basis decreased during growth of the sprouts. Sprouts grown from irradiated seeds had greater antioxidant capacity and AA content on a fresh weight basis than those grown from nonirradiated seeds. However, when the nutritive values were expressed on a per gram of seed basis, irradiation had no effect on the nutritive values of sprouts.

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

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.

Changes in quality, liking, and purchase intent of irradiated fresh-cut spinach during storage.

PubMed

Fan, Xuetong; Sokorai, Kimberly J B

2011-08-01

The use of ionizing radiation to enhance microbial safety of fresh spinach at a maximum dose of 4 kGy has been approved by the U.S. Food and Drug Administration (FDA). However, whether spinach can tolerate those high doses of radiation is unclear. Therefore, this study was conducted to investigate the effects of irradiation and storage on quality, liking, and purchase intent of fresh-cut spinach. The oxygen radical absorbance capacity values and total phenolic content were not consistently affected by irradiation. However, the ascorbic acid content of irradiated sample decreased rapidly during storage, resulting in these samples being lower in ascorbic acid content than controls after 7 and 14 d of storage at 4 °C. Sensory evaluation by a 50-member panel revealed that purchase intent and ratings for liking of appearance, aroma, texture, flavor, and overall were not affected by irradiation at doses up to 2 kGy. Therefore, irradiation at doses up to 2 kGy may be used to enhance microbial safety without affecting consumer acceptance or overall antioxidant values of irradiated spinach. Journal of Food Science © 2011 Institute of Food Technologists® No claim to original US government works.

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.

Physiologically-based pharmacokinetic model for Fentanyl in support of the development of Provisional Advisory Levels

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

Shankaran, Harish, E-mail: harish.shankaran@pnnl.gov; Adeshina, Femi; Teeguarden, Justin G.

Provisional Advisory Levels (PALs) are tiered exposure limits for toxic chemicals in air and drinking water that are developed to assist in emergency responses. Physiologically-based pharmacokinetic (PBPK) modeling can support this process by enabling extrapolations across doses, and exposure routes, thereby addressing gaps in the available toxicity data. Here, we describe the development of a PBPK model for Fentanyl – a synthetic opioid used clinically for pain management – to support the establishment of PALs. Starting from an existing model for intravenous Fentanyl, we first optimized distribution and clearance parameters using several additional IV datasets. We then calibrated the modelmore » using pharmacokinetic data for various formulations, and determined the absorbed fraction, F, and time taken for the absorbed amount to reach 90% of its final value, t90. For aerosolized pulmonary Fentanyl, F = 1 and t90 < 1 min indicating complete and rapid absorption. The F value ranged from 0.35 to 0.74 for oral and various transmucosal routes. Oral Fentanyl was absorbed the slowest (t90 ∼ 300 min); the absorption of intranasal Fentanyl was relatively rapid (t90 ∼ 20–40 min); and the various oral transmucosal routes had intermediate absorption rates (t90 ∼ 160–300 min). Based on these results, for inhalation exposures, we assumed that all of the Fentanyl inhaled from the air during each breath directly, and instantaneously enters the arterial circulation. We present model predictions of Fentanyl blood concentrations in oral and inhalation scenarios relevant for PAL development, and provide an analytical expression that can be used to extrapolate between oral and inhalation routes for the derivation of PALs. - Highlights: • We develop a Fentanyl PBPK model for relating external dose to internal levels. • We calibrate the model to oral and inhalation exposures using > 50 human datasets. • Model predictions are in good agreement with the available pharmacokinetic data. • The model can be used for extrapolating across routes, doses and exposure durations. • We illustrate how the model can be used for developing Provisional Advisory Levels.« less

Monte Carlo determination of the conversion coefficients Hp(3)/Ka in a right cylinder phantom with 'PENELOPE' code. Comparison with 'MCNP' simulations.

PubMed

Daures, J; Gouriou, J; Bordy, J M

2011-03-01

This work has been performed within the frame of the European Union ORAMED project (Optimisation of RAdiation protection for MEDical staff). The main goal of the project is to improve standards of protection for medical staff for procedures resulting in potentially high exposures and to develop methodologies for better assessing and for reducing, exposures to medical staff. The Work Package WP2 is involved in the development of practical eye-lens dosimetry in interventional radiology. This study is complementary of the part of the ENEA report concerning the calculations with the MCNP-4C code of the conversion factors related to the operational quantity H(p)(3). In this study, a set of energy- and angular-dependent conversion coefficients (H(p)(3)/K(a)), in the newly proposed square cylindrical phantom made of ICRU tissue, have been calculated with the Monte-Carlo code PENELOPE and MCNP5. The H(p)(3) values have been determined in terms of absorbed dose, according to the definition of this quantity, and also with the kerma approximation as formerly reported in ICRU reports. At a low-photon energy (up to 1 MeV), the two results obtained with the two methods are consistent. Nevertheless, large differences are showed at a higher energy. This is mainly due to the lack of electronic equilibrium, especially for small angle incidences. The values of the conversion coefficients obtained with the MCNP-4C code published by ENEA quite agree with the kerma approximation calculations obtained with PENELOPE. We also performed the same calculations with the code MCNP5 with two types of tallies: F6 for kerma approximation and *F8 for estimating the absorbed dose that is, as known, due to secondary electrons. PENELOPE and MCNP5 results agree for the kerma approximation and for the absorbed dose calculation of H(p)(3) and prove that, for photon energies larger than 1 MeV, the transport of the secondary electrons has to be taken into account.

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.

Double-blind evaluation of the safety and pharmacokinetics of multiple oral once-daily 750-milligram and 1-gram doses of levofloxacin in healthy volunteers.

PubMed

Chien, S C; Wong, F A; Fowler, C L; Callery-D'Amico, S V; Williams, R R; Nayak, R; Chow, A T

1998-04-01

The safety and pharmacokinetics of once-daily oral levofloxacin in 16 healthy male volunteers were investigated in a randomized, double-blind, placebo-controlled study. Subjects were randomly assigned to the treatment (n = 10) or placebo group (n = 6). In study period 1, 750 mg of levofloxacin or a placebo was administered orally as a single dose on day 1, followed by a washout period on days 2 and 3; dosing resumed for days 4 to 10. Following a 3-day washout period, 1 g of levofloxacin or a placebo was administered in a similar fashion in period 2. Plasma and urine levofloxacin concentrations were measured by high-pressure liquid chromatography. Pharmacokinetic parameters were estimated by model-independent methods. Levofloxacin was rapidly absorbed after single and multiple once-daily 750-mg and 1-g doses with an apparently large volume of distribution. Peak plasma levofloxacin concentration (Cmax) values were generally attained within 2 h postdose. The mean values of Cmax and area under the concentration-time curve from 0 to 24 h (AUC0-24) following a single 750-mg dose were 7.1 microg/ml and 71.3 microg x h/ml, respectively, compared to 8.6 microg/ml and 90.7 microg x h/ml, respectively, at steady state. Following the single 1-g dose, mean Cmax and AUC0-24 values were 8.9 microg/ml and 95.4 microg x h/ml, respectively; corresponding values at steady state were 11.8 microg/ml and 118 microg x h/ml. These Cmax and AUC0-24 values indicate modest and similar degrees of accumulation upon multiple dosing at the two dose levels. Values of apparent total body clearance (CL/F), apparent volume of distribution (Vss/F), half-life (t1/2), and renal clearance (CL[R]) were similar for the two dose levels and did not vary from single to multiple dosing. Mean steady-state values for CL/F, Vss/F, t1/2, and CL(R) following 750 mg of levofloxacin were 143 ml/min, 100 liters, 8.8 h, and 116 ml/min, respectively; corresponding values for the 1-g dose were 146 ml/min, 105 liters, 8.9 h, and 105 ml/min. In general, the pharmacokinetics of levofloxacin in healthy subjects following 750-mg and 1-g single and multiple once-daily oral doses appear to be consistent with those found in previous studies of healthy volunteers given 500-mg doses. Levofloxacin was well tolerated at either high dose level. The most frequently reported drug-related adverse events were nausea and headache.

Double-Blind Evaluation of the Safety and Pharmacokinetics of Multiple Oral Once-Daily 750-Milligram and 1-Gram Doses of Levofloxacin in Healthy Volunteers

PubMed Central

Chien, Shu-Chean; Wong, Frank A.; Fowler, Cynthia L.; Callery-D’Amico, Susan V.; Williams, R. Rex; Nayak, Ramchandra; Chow, Andrew T.

1998-01-01

The safety and pharmacokinetics of once-daily oral levofloxacin in 16 healthy male volunteers were investigated in a randomized, double-blind, placebo-controlled study. Subjects were randomly assigned to the treatment (n = 10) or placebo group (n = 6). In study period 1, 750 mg of levofloxacin or a placebo was administered orally as a single dose on day 1, followed by a washout period on days 2 and 3; dosing resumed for days 4 to 10. Following a 3-day washout period, 1 g of levofloxacin or a placebo was administered in a similar fashion in period 2. Plasma and urine levofloxacin concentrations were measured by high-pressure liquid chromatography. Pharmacokinetic parameters were estimated by model-independent methods. Levofloxacin was rapidly absorbed after single and multiple once-daily 750-mg and 1-g doses with an apparently large volume of distribution. Peak plasma levofloxacin concentration (Cmax) values were generally attained within 2 h postdose. The mean values of Cmax and area under the concentration-time curve from 0 to 24 h (AUC0–24) following a single 750-mg dose were 7.1 μg/ml and 71.3 μg · h/ml, respectively, compared to 8.6 μg/ml and 90.7 μg · h/ml, respectively, at steady state. Following the single 1-g dose, mean Cmax and AUC0–24 values were 8.9 μg/ml and 95.4 μg · h/ml, respectively; corresponding values at steady state were 11.8 μg/ml and 118 μg · h/ml. These Cmax and AUC0–24 values indicate modest and similar degrees of accumulation upon multiple dosing at the two dose levels. Values of apparent total body clearance (CL/F), apparent volume of distribution (Vss/F), half-life (t1/2), and renal clearance (CLR) were similar for the two dose levels and did not vary from single to multiple dosing. Mean steady-state values for CL/F, Vss/F, t1/2, and CLR following 750 mg of levofloxacin were 143 ml/min, 100 liters, 8.8 h, and 116 ml/min, respectively; corresponding values for the 1-g dose were 146 ml/min, 105 liters, 8.9 h, and 105 ml/min. In general, the pharmacokinetics of levofloxacin in healthy subjects following 750-mg and 1-g single and multiple once-daily oral doses appear to be consistent with those found in previous studies of healthy volunteers given 500-mg doses. Levofloxacin was well tolerated at either high dose level. The most frequently reported drug-related adverse events were nausea and headache. PMID:9559801

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

Comparative dose levels between CT-scanner and slot-scanning device (EOS system) in pregnant women pelvimetry.

PubMed

Ben Abdennebi, A; Aubry, S; Ounalli, L; Fayache, M S; Delabrousse, E; Petegnief, Y

2017-01-01

To estimate fetal absorbed doses for pregnant women pelvimetry, a comparative study between EOS imaging system and low-dose spiral CT-scanner was carried out. For this purpose three different studies were investigated: in vivo, in vitro and Monte Carlo calculations. In vivo dosimetry was performed, using OSL NanoDot dosimeters, to determine the dose to the skin of twenty pregnant women. In vitro studies were established by using a cubic phantom of water, in order to estimate the out of field doses. In the latter study, OSLDs were placed at depths corresponding to the lowest, average and highest position of the uterus. Monte Carlo calculations of effective doses to high radio-sensitive organs were established, using PCXMC and CTExpo software suites for EOS imaging system and CT-scanner, respectively. The EOS imaging system reduces radiation exposure 4 to 8 times compared to the CT-scanner. The entrance skin doses were 74% (p-values <0.01) higher with the CT-scanner than with the EOS system. In the out of field region, the measured doses of the EOS system were reduced by 80% (p-values <0.02). Monte Carlo calculations confirmed that effective doses to organs are less accentuated for EOS than for CT pelvimetry. The EOS system is less irradiating than the CT exam. The out-of-field dose which is significant, is lower in the EOS than in the CT-scanner and could be reduced even further by optimizing the time used for image acquisition. Copyright © 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Comparison of three and four-field radiotherapy technique and the effect of laryngeal shield on vocal and spinal cord radiation dose in radiotherapy of non-laryngeal head and neck tumors

NASA Astrophysics Data System (ADS)

Pour, Noushin Hassan; Farajollahi, Alireza; Jamali, Masoud; Zeinali, Ahad; Jangjou, Amir Ghasemi

2018-03-01

Introduction: Due to the effect of radiation on both the tumor and the surrounding normal tissues, the side effects of radiation in normal tissues are expected. One of the important complications in the head and neck radiotherapy is the doses reached to the larynx and spinal cord of patients with non-laryngeal head and neck tumors. Materials and Methods: In this study, CT scan images of 25 patients with non-laryngeal tumors including; lymph nodes, tongue, oropharynx and nasopharynx were used. A three-field and a four-field treatment planning with and without laryngeal shield in 3D CRT technique were planned for each patient. Subsequently, the values of Dmin, Dmean, Dmax and Dose Volume Histogram from the treatment planning system and NTCP values of spinal cord and larynx were calculated with BIOPLAN and MATLAB software for all patients. Results: Statistical results showed that mean values of doses of larynx in both three and four-field methods were significantly different between with and without shield groups. Comparison of absorbed dose didn't show any difference between the three and four field methods (P>0.05). Using Shield, just the mean and minimum doses of spinal cord decreased in both three and four fields. The NTCP of the spinal cord and larynx by three and four-field methods with shield in the LKB and EUD models significantly are less than that of the three and four fields without shields, and in the four-field method NTCP of larynx is less than three radiation field. Conclusion: The results of this study indicate that there is no significant difference in doses reached to larynx and spinal cord between the treatments techniques, but laryngeal shield reduce dose and NTCP values in larynx considerably.

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.

Predictive model of early mortality following acute inhalation of PuO/sub 2/ aerosols. [Extrapolation of beagle data to man

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

Raabe, O.G.; Goldman, M.

Since data on the pulmonary toxicity of plutonium in people are not available, estimates must be based upon available experimental animal data. For this purpose, inhalation studies with beagle dogs exposed to aerosols of /sup 238/PuO/sub 2/ and /sup 239/PuO/sub 2/ were analyzed and a simple model has been proposed to describe apparent dose-response relationships. It was found that for each aerosol and radionuclide form, the cumulative absorbed lung dose that leads to death from lung damage up to 1000 days could be assumed to have a log-normal distribution of values that was independent of time to death. The datamore » was satisfactorily fit to a model in which the time of death postexposure is given by: t = (K/D), with the time to death, the cumulative dose to lung tissue (the killing dose), and anti D the average dose rate to lung tissue from time of exposure to death. The ratios of median K values, normalized to the value for /sup 90/Sr--Y FAP, indicate a relative biological effectiveness (RBE) of 14 for /sup 239/PuO/sub 2/ particles and 5 for /sup 238/PuO/sub 2/ particles. This demonstrates an effect of particle specific activity on relative biological effectiveness for early mortality, since an increase in specific activity of particles leads to a lower apparent RBE.« less

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

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.

Dose uniformity analysis among ten 16-slice same-model CT scanners.

PubMed

Erdi, Yusuf Emre

2012-01-01

With the introduction of multislice scanners, computed tomographic (CT) dose optimization has become important. The patient-absorbed dose may differ among the scanners although they are the same type and model. To investigate the dose output variation of the CT scanners, we designed the study to analyze dose outputs of 10 same-model CT scanners using 3 clinical protocols. Ten GE Lightspeed (GE Healthcare, Waukesha, Wis) 16-slice scanners located at main campus and various satellite locations of our institution have been included in this study. All dose measurements were performed using poly (methyl methacrylate) (PMMA) head (diameter, 16 cm) and body (diameter, 32 cm) phantoms manufactured by Radcal (RadCal Corp, Monrovia, Calif) using a 9095 multipurpose analyzer with 10 × 9-3CT ion chamber both from the same manufacturer. Ion chamber is inserted into the peripheral and central axis locations and volume CT dose index (CTDIvol) is calculated as weighted average of doses at those locations. Three clinical protocol settings for adult head, high-resolution chest, and adult abdomen are used for dose measurements. We have observed up to 9.4% CTDIvol variation for the adult head protocol in which the largest variation occurred among the protocols. However, head protocol uses higher milliampere second values than the other 2 protocols. Most of the measured values were less than the system-stored CTDIvol values. It is important to note that reduction in dose output from tubes as they age is expected in addition to the intrinsic radiation output fluctuations of the same scanner. Although the same model CT scanners were used in this study, it is possible to see CTDIvol variation in standard patient scanning protocols of head, chest, and abdomen. The compound effect of the dose variation may be larger with higher milliampere and multiphase and multilocation CT scans.

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.

Assessment of radiological hazard parameters due to natural radioactivity in soils from granite-rich regions in Kütahya Province, Turkey.

PubMed

Sahin, Latife; Hafızoğlu, Nurgül; Çetinkaya, Hakan; Manisa, Kaan; Bozkurt, Engin; Biçer, Ahmet

2017-05-01

The analysis of natural radioactivity from 238 U, 232 Th and 40 K in 357 soil samples collected from the province of Kütahya was carried out using a NaI(Tl) gamma-ray spectroscopy system at the Nuclear Physics Research Laboratory, Dumlupınar University, Kütahya, Turkey. The specific activities of 238 U, 232 Th and 40 K in the soil samples were evaluated. From the activity concentrations of 238 U, 232 Th and 40 K, the total absorbed outdoor gamma-ray dose rates and the corresponding annual effective dose rates were determined. The corresponding values of the external and internal hazard indices of all the soil samples were also calculated. The external gamma-ray dose rate at 1 m above the ground was directly measured at each collected soil sample location. The results obtained in this study were compared within the limits of values obtained in other cities of Turkey, those in other countries. Radiological maps of Kütahya Province were constructed from the results of this study.

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

Estimation of factors from natural and anthropogenic radioactivity present in the surface soil and comparison with DCF values.

PubMed

Ranade, A K; Pandey, M; Datta, D

2013-01-01

A study was conducted to evaluate the absorbed rate coefficient of (238)U, (232)Th, (40)K and (137)Cs present in soil. A total of 31 soil samples and the corresponding terrestrial dose rates at 1 m from different locations were taken around the Anushaktinagar region, where the litho-logy is dominated by red soil. A linear regression model was developed for the estimation of these factors. The estimated coefficients (nGy h(-1) Bq(-1) kg(-1)) were 0.454, 0.586, 0.035 and 0.392, respectively. The factors calculated were in good agreement with the literature values.

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

Safety and pharmacokinetics of Bevirimat (PA-457), a novel inhibitor of human immunodeficiency virus maturation, in healthy volunteers.

PubMed

Martin, David E; Blum, Robert; Wilton, John; Doto, Judy; Galbraith, Hal; Burgess, Gina L; Smith, Philip C; Ballow, Charles

2007-09-01

Bevirimat (BVM; formerly known as PA-457) is a novel inhibitor of human immunodeficiency virus (HIV) maturation that is being developed for the treatment of HIV infection. The pharmacokinetics of this agent in healthy male volunteers were studied in a randomized, double-blind study in which the participants received single oral doses of placebo (n = 8) or escalating doses of BVM at 25, 50, 100, or 250 mg (n = 6 per dose); escalation was performed only after the pharmacokinetics and safety of the preceding dose had been evaluated. Plasma was collected over 480 h after dosing and urine was collected over 48 h after dosing for determination of the values of pharmacokinetic parameters. BVM was well absorbed after oral administration, with peak plasma concentrations being achieved 1 to 3 h after dosing. The half-life was 60 to 80 h. The exposure assessed by determination of the peak concentration and the area under the concentration-time curve was dose proportional. Single oral doses of BVM were well tolerated: there were no dose-limiting toxicities, and no serious adverse events were reported. These findings suggest that that BVM offers a favorable pharmacokinetic profile, with predictable pharmacokinetics following the oral administration of single doses. The long half-life of BVM may facilitate once-daily dosing.

Pharmacokinetics, safety and tolerability of rotigotine transdermal patch in healthy Japanese and Caucasian subjects.

PubMed

Cawello, Willi; Kim, Seong R; Braun, Marina; Elshoff, Jan-Peer; Ikeda, Junji; Funaki, Tomoo

2014-02-01

Rotigotine is a dopamine receptor agonist with activity across the D1 through to D5 receptors as well as select serotonergic and adrenergic sites; continuous transdermal delivery of rotigotine with replacement of the patch once daily maintains stable plasma concentrations over 24 h. Rotigotine is indicated for the treatment of early and advanced-stage Parkinson's disease and moderate-to-severe idiopathic restless legs syndrome. The pharmacokinetics and pharmacodynamics of a drug may vary between subjects of different ethnic origin. This study evaluated the pharmacokinetics, safety, and tolerability of single-dose treatment with rotigotine transdermal patch in Japanese and Caucasian subjects. In this open-label, parallel-group study, healthy male and female subjects of Japanese or Caucasian ethnic origin were matched by sex, body mass index, and age. A single transdermal patch delivering 2 mg/24 h rotigotine (patch content 4.5 mg) was applied to the ventral/lateral abdomen for 24 h. The main outcome measures were the plasma concentrations of unconjugated and total rotigotine and its desalkyl metabolites and derived pharmacokinetic parameters (area under the concentration-time curve from time zero to last quantifiable concentration [AUClast], maximum plasma concentration [Cmax], and body weight- and dose-normalized values). The pharmacokinetic analysis included 48 subjects (24 Japanese, 24 Caucasian). The mean apparent dose of rotigotine was 2.0±0.5 mg for Japanese subjects and 2.08±0.58 mg for Caucasians. Plasma concentration-time profiles of unconjugated rotigotine and of the main metabolites were similar for both ethnic groups. Parameters of model-independent pharmacokinetics, Cmax, time to Cmax (tmax), and AUClast, for unconjugated rotigotine showed no statistically significant differences between Japanese and Caucasian subjects. Values of concentration-dependent pharmacokinetic parameters were higher in female subjects; this difference was minimized after correction for body weight. A statistically significant difference between ethnic groups was observed for total rotigotine concentrations (total rotigotine=unconjugated rotigotine+conjugated rotigotine), with slightly lower values in Caucasians after correction for body weight and apparent dose. No relevant differences were observed between males and females. Inter-individual variability was high. The terminal half-life for unconjugated rotigotine was 5.3 h in Japanese subjects and 5.7 h in Caucasians; corresponding values for total rotigotine were 8.6 h and 9.6 h. Less than 0.1% of the apparent dose was renally excreted as the parent compound. Renal elimination of total rotigotine covers 11.7% of absorbed dose in Japanese subjects and 10.8% of the absorbed dose in Caucasians, whereas the renal elimination via total despropyl rotigotine was 8.2 and 7.1%, respectively. The corresponding values for total desthienylethyl rotigotine were 3.5% in Japanese subjects and 4.2% Caucasians. Most adverse events were mild in intensity and typical for dopamine agonists or for transdermal therapeutics. Administration of a single patch delivering 2 mg/24 h rotigotine resulted in comparable pharmacokinetic profiles in Japanese and Caucasian subjects. The rotigotine transdermal patch was generally well-tolerated. Our findings suggest similar dose requirements for Japanese and Caucasian populations.

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.

SU-E-T-592: OSL Response of Al2O3:C Detectors Exposed to Therapeutic Proton Beams

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

Granville, DA; Flint, DB; Sawakuchi, GO

Purpose: To characterize the response of Al{sub 2}O{sub 3}:C optically stimulated luminescence (OSL) detectors (OSLDs) exposed to therapeutic proton beams of differing beam quality. Methods: We prepared Al{sub 2}O{sub 3}:C OSLDs from the same material as commercially available nanoDot dosimeters (Landauer, Inc). We irradiated the OSLDs in modulated proton beams of varying quality, as defined by the residual range. An absorbed dose to water of 0.2 Gy was delivered to all OSLDs with the residual range values varying from 0.5 to 23.5 cm (average LET in water from ∼0.5 to 2.5 keV/µm). To investigate the beam quality dependence of differentmore » emission bands within the OSL spectrum, we performed OSLD readouts using both continuous-wave stimulation (CW-OSL) and pulsed stimulation (P-OSL) with two sets of optical filters (Hoya U-340 and Kopp 5113). For all readout modes, the relative absorbed dose sensitivity ( S{sub rel}) for each beam quality was calculated using OSLDs irradiated in a 6 MV photon beam as a reference. Results: We found that the relative absorbed dose sensitivity was highly dependent on both readout mode and integration time of the OSL signal. For CW-OSL signals containing only the blue emission band, S{sub rel} was between 0.85 and 0.94 for 1 s readouts and between 0.82 and 0.93 for 10 s readouts. Similarly, for P-OSL readouts containing only the blue emission band S{sub rel} ranged from 0.86 to 0.91, and 0.82 to 0.93 for 1 s and 10 s readouts, respectively. For OSLD signals containing only the UV emission band, S{sub rel} ranged from 1.00 to 1.46, and 0.97 to 1.30 for P-OSL readouts of 1 s and 10 s, respectively. Conclusion: For measurements of absorbed dose using Al{sub 2}O{sub 3}:C OSLDs in therapeutic proton beams, dependence on beam quality was smallest for readout protocols that selected the blue emission band with small integration times. DA Granville received financial support from the Natural Sciences and Engineering Research Council of Canada.« 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.

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.

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.

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

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.

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.

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.

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.

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.

Sci—Fri PM: Topics — 04: What if bystander effects influence cell kill within a target volume? Potential consequences of dose heterogeneity on TCP and EUD on intermediate risk prostate patients

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

Balderson, M.J.; Kirkby, C.; Department of Medical Physics, Tom Baker Cancer Centre, Calgary, Alberta

In vitro evidence has suggested that radiation induced bystander effects may enhance non-local cell killing which may influence radiotherapy treatment planning paradigms. This work applies a bystander effect model, which has been derived from published in vitro data, to calculate equivalent uniform dose (EUD) and tumour control probability (TCP) and compare them with predictions from standard linear quadratic (LQ) models that assume a response due only to local absorbed dose. Comparisons between the models were made under increasing dose heterogeneity scenarios. Dose throughout the CTV was modeled with normal distributions, where the degree of heterogeneity was then dictated by changingmore » the standard deviation (SD). 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. The bystander model suggests a moderate degree of dose heterogeneity yields as good or better outcome compared to a uniform dose in terms of EUD and TCP. Intermediate risk prostate prescriptions of 78 Gy over 39 fractions had maximum EUD and TCP values at SD of around 5Gy. The plots only dropped below the uniform dose values for SD ∼ 10 Gy, almost 13% of the prescribed dose. The bystander model demonstrates the potential to deviate from the common local LQ model predictions as dose heterogeneity through a prostate CTV is varies. The results suggest the potential for allowing some degree of dose heterogeneity within a CTV, although further investigations of the assumptions of the bystander model are warranted.« less

Calibration of GafChromic EBT3 for absorbed dose measurements in 5 MeV proton beam and (60)Co γ-rays.

PubMed

Vadrucci, M; Esposito, G; Ronsivalle, C; Cherubini, R; Marracino, F; Montereali, R M; Picardi, L; Piccinini, M; Pimpinella, M; Vincenti, M A; De Angelis, C

2015-08-01

To study EBT3 GafChromic film in low-energy protons, and for comparison purposes, in a reference (60)Co beam in order to use it as a calibrated dosimetry system in the proton irradiation facility under construction within the framework of the Oncological Therapy with Protons (TOP)-Intensity Modulated Proton Linear Accelerator for RadioTherapy (IMPLART) Project at ENEA-Frascati, Italy. EBT3 film samples were irradiated at the Istituto Nazionale di Fisica Nucleare-Laboratori Nazionali di Legnaro, Italy, with a 5 MeV proton beam generated by a 7 MV Van de Graaff CN accelerator. The nominal dose rates used were 2.1 Gy/min and 40 Gy/min. The delivered dose was determined by measuring the particle fluence and the energy spectrum in air with silicon surface barrier detector monitors. A preliminary study of the EBT3 film beam quality dependence in low-energy protons was conducted by passively degrading the beam energy. EBT3 films were also irradiated at ENEA-National Institute of Ionizing Radiation Metrology with gamma radiation produced by a (60)Co source characterized by an absorbed dose to water rate of 0.26 Gy/min as measured by a calibrated Farmer type ionization chamber. EBT3 film calibration curves were determined by means of a set of 40 film pieces irradiated to various doses ranging from 0.5 Gy to 30 Gy absorbed dose to water. An EPSON Expression 11000XL color scanner in transmission mode was used for film analysis. Scanner response stability, intrafilm uniformity, and interfilm reproducibility were verified. Optical absorption spectra measurements were performed on unirradiated and irradiated EBT3 films to choose the most sensitive color channel to the dose range used. EBT3 GafChromic films show an under response up to about 33% for low-energy protons with respect to (60)Co gamma radiation, which is consistent with the linear energy transfer dependence already observed with higher energy protons, and a negligible dose-rate dependence in the 2-40 Gy/min range. Short- and long-term scanner stabilities were 0.5% and 1.5%, respectively; film uniformity and reproducibility were better than 0.5%. The main purpose of this study was to implement EBT3 dosimetry in the proton low-energy radiobiology line of the TOP-IMPLART accelerator, having a maximum energy of 7 MeV. Low-energy proton and (60)Co calibrated sources were used to investigate the behavior of film response vs to be written in italicum dose. The calibration in 5 MeV protons is currently used for dose assessment in the radiobiological experiments at the TOP-IMPLART accelerator carried out at that energy value.

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.

WE-E-BRE-03: Biological Validation of a Novel High-Throughput Irradiator for Predictive Radiation Sensitivity Bioassays

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

Fowler, TL; Martin, JA; Shepard, AJ

2014-06-15

Purpose: The large dose-response variation in both tumor and normal cells between individual patients has led to the recent implementation of predictive bioassays of patient-specific radiation sensitivity in order to personalize radiation therapy. This exciting new clinical paradigm has led us to develop a novel high-throughput, variable dose-rate irradiator to accompany these efforts. Here we present the biological validation of this irradiator through the use of human cells as a relative dosimeter assessed by two metrics, DNA double-strand break repair pathway modulation and intercellular reactive oxygen species production. Methods: Immortalized human tonsilar epithelial cells were cultured in 96-well micro titermore » plates and irradiated in groups of eight wells to absorbed doses of 0, 0.5, 1, 2, 4, and 8 Gy. High-throughput immunofluorescent microscopy was used to detect γH2AX, a DNA double-strand break repair mechanism recruiter. The same analysis was performed with the cells stained with CM-H2DCFDA that produces a fluorescent adduct when exposed to reactive oxygen species during the irradiation cycle. Results: Irradiations of the immortalized human tonsilar epithelial cells at absorbed doses of 0, 0.5, 1, 2, 4, and 8 Gy produced excellent linearity in γH2AX and CM-H2DCFDA with R2 values of 0.9939 and 0.9595 respectively. Single cell gel electrophoresis experimentation for the detection of physical DNA double-strand breaks in ongoing. Conclusions: This work indicates significant potential for our high-throughput variable dose rate irradiator for patient-specific predictive radiation sensitivity bioassays. This irradiator provides a powerful tool by increasing the efficiency and number of assay techniques available to help personalize radiation therapy.« less

Long-term development of the radionuclide exposure of murine rodent populations in Belarus after the Chernobyl accident.

PubMed

Ryabokon, N I; Smolich, I I; Kudryashov, V P; Goncharova, R I

2005-12-01

As a determinant of the associated health risks, the behavior of radionuclides in natural ecosystems needs to be better understood. Therefore, the activity concentration of various long-lived radionuclides released due to the Chernobyl accident, and the corresponding contributions to the whole-body dose rate, was studied as a function of time in mammalian indicator species inhabiting the natural forest ecosystems of Belarus, the bank vole (Clethrionomys glareolus) and the yellow-necked mouse (Apodemus flavicollus). The activity concentrations of 137Cs, 134Cs, 90Sr, 238Pu, 239,240Pu, 241Pu and 241Am in soil and in animals were measured at five monitoring sites with different ground deposition of radionuclides at different distances from the destroyed reactor. The observed temporal pattern of the radionuclide activity concentration in the studied animal populations reflects the changes in biological availability of these isotopes for biota, mostly due to fuel particle destruction and appearance of dissolved and exchangeable forms of radionuclides. The time course of 134+137Cs activity concentrations in animal populations appeared as a sequence of increase, peak and decrease. Maximal levels of radiocesium occurred 1-2 years after deposition, followed by an exponential decrease. Concentrations of incorporated 90Sr increased up to the tenth year after deposition. The activity concentrations of transuranic elements (238Pu, 239,240Pu, 241Pu and 241Am) were much lower than those of the other radionuclides, in the studied animals. A considerable activity of 241Am in animals from areas with high levels of contamination was firstly detected 5 years after deposition, it increased up to the tenth year and is expected to increase further in the future. Maximal values of the whole-body absorbed dose rates occurred during the year of deposition, followed by a decrease in the subsequent period. Generally, this decrease was monotonic, mainly determined by the decrease of the external gamma-ray dose rate, but there were exceptions due to the delayed maximum of internal exposure. The inter-individual distributions of radionuclide concentrations and lifetime whole-body absorbed doses were asymmetric and close to log-normal, including concentrations and doses considerably higher than the population mean values.

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.

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.

Evaluation of external exposures of the population of Ozyorsk, Russia, with luminescence measurements of bricks.

PubMed

Woda, Clemens; Jacob, P; Ulanovsky, A; Fiedler, I; Mokrov, Y; Rovny, S

2009-11-01

Recently discovered historical documents indicate that large releases of noble gases (mainly (41)Ar and radioactive isotopes of Kr and Xe) from the Mayak Production Association (MPA) over the period from 1948 to 1956 may have caused considerable external exposures of both, inhabitants of Ozyorsk and former inhabitants of villages at the upper Techa River. To quantify this exposure, seven brick samples from three buildings in Ozyorsk, located 8-10 km north-northwest from the radioactive gas release points, were taken. The absorbed dose in brick was measured in a depth interval of 3-13 mm below the exposed surface of the bricks by means of the thermoluminescence (TL) and the optically stimulated luminescence (OSL) method. Generally, luminescence properties using TL were more favorable for precise dose determination than using OSL, but within their uncertainties the results from both methods agree well with each other. The absorbed dose due to natural radiation was assessed and subtracted under the assumption of the bricks to be completely dry. The weighted average of the anthropogenic dose for all samples measured by TL and OSL is 10 +/- 9 and 1 +/- 9 mGy, respectively. An upper limit for a possible anthropogenic dose in brick that would not be detected due to the measurement uncertainties is estimated at 24 mGy. This corresponds to an effective dose of about 21 mSv. A similar range of values is obtained in recently published dispersion calculations that were based on reconstructed MPA releases. It is concluded that the release of radioactive noble gases from the radiochemical and reactor plants at Mayak PA did not lead to a significant external exposure of the population of Ozyorsk. In addition, the study demonstrates the detection limit for anthropogenic doses in ca. 60-year-old bricks to be about 24 mGy, if luminescence methods are used.

Assessment of Mean Glandular Dose in Mammography System with Different Anode-Filter Combinations Using MCNP Code.

PubMed

Gholamkar, Lida; Mowlavi, Ali Asghar; Sadeghi, Mahdi; Athari, Mitra

2016-10-01

X-ray mammography is one of the general methods for early detection of breast cancer. Since glandular tissue in the breast is sensitive to radiation and it increases the risk of cancer, the given dose to the patient is very important in mammography. The aim of this study was to determine the average absorbed dose of X-ray radiation in the glandular tissue of the breast during mammography examinations as well as investigating factors that influence the mean glandular dose (MGD). One of the precise methods for determination of MGD absorbed by the breast is Monte Carlo simulation method which is widely used to assess the dose. We studied some different X-ray sources and exposure factors that affect the MGD. "Midi-future" digital mammography system with amorphous-selenium detector was simulated using the Monte Carlo N-particle extended (MCNPX) code. Different anode/filter combinations such as tungsten/silver (W/Ag), tungsten/rhodium (W/Rh), and rhodium/aluminium (Rh/Al) were simulated in this study. The voltage of X-ray tube ranged from 24 kV to 32 kV with 2 kV intervals and the breast phantom thickness ranged from 3 to 8 cm, and glandular fraction g varied from 10% to 100%. MGD was measured for different anode/filter combinations and the effects of changing tube voltage, phantom thickness, combination and glandular breast tissue on MGD were studied. As glandular g and X-ray tube voltage increased, the breast dose increased too, and the increase of breast phantom thickness led to the decrease of MGD. The obtained results for MGD were consistent with the result of Boone et al. that was previously reported. By comparing the results, we saw that W/Rh anode/filter combination is the best choice in breast mammography imaging because of the lowest delivered dose in comparison with W/Ag and Rh/Al. Moreover, breast thickness and g value have significant effects on MGD.

Small Active Radiation Monitor

NASA Technical Reports Server (NTRS)

Badhwar, Gautam D.

2004-01-01

A device, named small active radiation monitor, allows on-orbit evaluations during periods of increased radiation, after extravehicular activities, or at predesignated times for crews on such long-duration space missions as on the International Space Station. It also permits direct evaluation of biological doses, a task now performed using a combination of measurements and potentially inaccurate simulations. Indeed the new monitor can measure a full array of radiation levels, from soft x-rays to hard galactic cosmic-ray particles. With refinement, it will benefit commercial (nuclear power-plant workers, airline pilots, medical technicians, physicians/dentists, and others) and military personnel as well as the astronauts for whom thermoluminescent dosimeters are inadequate. Civilian and military personnel have long since graduated from film badges to thermoluminescent dosimeters. Once used, most dosimeters must be returned to a central facility for processing, a step that can take days or even weeks. While this suffices for radiation workers for whom exposure levels are typically very low and of brief duration, it does not work for astronauts. Even in emergencies and using express mail, the results can often be delayed by as much as 24 hours. Electronic dosimeters, which are the size of electronic oral thermometers, and tattlers, small electronic dosimeters that sound an alarm when the dose/dose rate exceeds preset values, are also used but suffer disadvantages similar to those of thermoluminescent dosimeters. None of these devices fully answers the need of rapid monitoring during the space missions. Instead, radiation is monitored by passive detectors, which are read out after the missions. Unfortunately, these detectors measure only the absorbed dose and not the biologically relevant dose equivalent. The new monitor provides a real-time readout, a time history of radiation exposures (both absorbed dose and biologically relevant dose equivalent), and a count of the number of particles passing through a unit area. Better still, the monitor can be used anywhere.

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.

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

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

SU-F-T-159: Monte Carlo Simulation Studies of Three-Dimensional Dose Distribution for Polymer Gel Dosimeter and Radiochromic Gel Dosimeter in a Proton Beam

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

Park, M; Kim, G; Jung, H

Purpose: The purpose of this simulation study is to evaluate the proton detectability of gel dosimeters, and estimate the three-dimensional dose distribution of protons in the radiochromic gel and polymer gel dosimeter compared with the dose distribution in water. Methods: The commercial composition ratios of normoxic polymer gel and LCV micelle radiochromic gel were included in this simulation study. The densities of polymer and radiochromic gel were 1.024 and 1.005 g/cm3, respectively. The 50, 80 and 140 MeV proton beam energies were selected. The dose distributions of protons in the polymer and radiochromic gel were simulated using Monte Carlo radiationmore » transport code (MCNPX 2.7.0, Los Alamos Laboratory). The water equivalent depth profiles and the dose distributions of two gel dosimeters were compared for the water. Results: In case of irradiating 50, 80 and 140 MeV proton beam to water phantom, the reference Bragg-peak depths are represented at 2.22, 5.18 and 13.98 cm, respectively. The difference in the water equivalent depth is represented to about 0.17 and 0.37 cm in the radiochromic gel and polymer gel dosimeter, respectively. The proton absorbed doses in the radiochromic gel dosimeter are calculated to 2.41, 3.92 and 6.90 Gy with increment of incident proton energies. In the polymer gel dosimeter, the absorbed doses are calculated to 2.37, 3.85 and 6.78 Gy with increment of incident proton energies. The relative absorbed dose in radiochromic gel (about 0.47 %) is similar to that of water than the relative absorbed dose of polymer gel (about 2.26 %). In evaluating the proton dose distribution, we found that the dose distribution of both gel dosimeters matched that of water in most cases. Conclusion: As the dosimetry device, the radiochromic gel dosimeter has the potential particle detectability and is feasible to use for quality assurance of proton beam therapy beam.« less

SU-E-T-753: Three-Dimensional Dose Distributions of Incident Proton Particle in the Polymer Gel Dosimeter and the Radiochromic Gel Dosimeter: A Simulation Study with MCNP Code

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

Park, M; Kim, G; Ji, Y

Purpose: The purpose of this study is to estimate the three-dimensional dose distributions in the polymer and the radiochromic gel dosimeter, and to identify the detectability of both gel dosimeters by comparing with the water phantom in case of irradiating the proton particles. Methods: The normoxic polymer gel and the LCV micelle radiochromic gel were used in this study. The densities of polymer and the radiochromic gel dosimeter were 1.024 and 1.005 g/cm{sup 3}, respectively. The dose distributions of protons in the polymer and radiochromic gel were simulated using Monte Carlo radiation transport code (MCNPX, Los Alamos National Laboratory). Themore » shape of phantom irradiated by proton particles was a hexahedron with the dimension of 12.4 × 12.4 × 15.0 cm{sup 3}. The energies of proton beam were 50, 80, and 140 MeV energies were directed to top of the surface of phantom. The cross-sectional view of proton dose distribution in both gel dosimeters was estimated with the water phantom and evaluated by the gamma evaluation method. In addition, the absorbed dose(Gy) was also calculated for evaluating the proton detectability. Results: The evaluation results show that dose distributions in both gel dosimeters at intermediated section and Bragg-peak region are similar with that of the water phantom. At entrance section, however, inconsistencies of dose distribution are represented, compared with water. The relative absorbed doses in radiochromic and polymer gel dosimeter were represented to be 0.47 % and 2.26 % difference, respectively. These results show that the radiochromic gel dosimeter was better matched than the water phantom in the absorbed dose evaluation. Conclusion: The polymer and the radiochromic gel dosimeter show similar characteristics in dose distributions for the proton beams at intermediate section and Bragg-peak region. Moreover the calculated absorbed dose in both gel dosimeters represents similar tendency by comparing with that in water phantom.« less

Effect of irradiation and storage on patulin disappearance and some chemical constituents of apple juice concentrate.

PubMed

Zegota, H; Zegota, A; Bachmann, S

1988-10-01

The effect of irradiation on the patulin content and on the chemical composition of apple juice concentrate during storage at 4 degrees C over a period of several weeks was investigated. The radiation-induced disappearance of the mycotoxin in relation to the absorbed dose followed an exponential relationship. The radiation dose (D50), i.e., the dose which reduced the patulin content to 50% of its initial value was equal to 0.35 kGy. Storage of the irradiated concentrate had no effect on the patulin content; however, storage did lead to a slight increase in the titratable acidity and a decrease in the amounts of the carbonyl compounds and the ascorbic acid concentration. The development of non-enzymatic browning during storage of the irradiated samples followed the same kinetics as that of the non-irradiated samples.

Application of stereo x-ray photogrammetry (SRM) in the determination of absorbed dose values during intracavitary radiation therapy

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

van Kleffens, H.J.; Star, W.M.

1979-04-01

The method of stereo x-ray photogrammetry is described, using a stereo x-ray comparator, as well as some clinical applications. The x-ray equipment consists of two x-ray tubes and a pneumatically driven cassette changer, developed to reduce effects of patient or organ motion between stero radiographs. The accuracy of the set-up is demonstated with measurements on a geometrical model and on a gelatine phantom containing radium needles. The clinical use is reported in determining dose rates to points of the intestinal wall during intracavitary radiotherapy of gynecological cancer. In a number of cases the stereo measurements have resulted in a changemore » in the application time or in the charge or position of the applicator, possibly preventing later complications, as a result of a high dose. Future applications for implant dosimetry (/sup 192/Ir, /sup 125/I) are suggested.« less

The radiation enhancement of the sterility assurance levels of sterile fluids — A case study

NASA Astrophysics Data System (ADS)

Plessis, T. A. Du.; Rosekilly, I. C.

1995-02-01

A study was undertaken to determine the effect of low-dose gamma irradiation on aseptically admixed total parenteral nutrition (TPN) solutions to which large inocula of three test bacterial species, recognised as common contaminants of these products, were added. Attainable SALs of TPN solutions containing test bacteria were subsequently calculated. Results showed that a minimum absorbed radiation dose as low as 1.5 kGy improved the SAL of aseptically prepared TPN solutions from a SAL of 10 -3 to a value of less than 10 -8 for the microorganisms investigated. No measurable changes in amino acid, electrolyte, glucose and lipid components of the solutions were detected up to a dose of 8.3 kGy. Practical experience applying this radiation treatment of TPNs rendered excellent results leading to the routine application of the process in South Africa.

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.

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

Bromine incorporation into five DBP classes upon chlorination of water with extremely low SUVA values.

PubMed

Hong, Huachang; Yan, Xiaoqing; Song, Xuhui; Qin, Yanyan; Sun, Hongjie; Lin, Hongjun; Chen, Jianrong; Liang, Yan

2017-07-15

The main objective of this study was to assess the effects of disinfection conditions on bromine incorporation into disinfection by-products (DBPs) during chlorination of water with low specific UV absorbance (SUVA). Five classes of DBPs were included: trihalomethanes (THMs), dihaloacetic acids (di-HAAs), trihaloacetic acids (tri-HAAs), dihaloacetonitriles (DHANs) and trihalonitromethanes (THNMs). Results showed that the bromine utilization in DBPs formation was positive related with reaction time, pH and temperature. On the other hand, the bromine substitution factors (BSFs) of DBPs were generally increased with pH (except tri-HAAs) and bromide concentration, but decreased with the reaction time, temperature and chlorine dose. Moreover, the BSFs values varied with DBP classes with the ranking being as following: THNMs≫DHANs≫tri-HAAs>THM≈di-HAAs. These results were mostly similar with the references, yet the pH effect on BSFs as well as the rank of BSFs for different DBP classes may differ with the specific UV absorbance of organic matter. Copyright © 2017 Elsevier B.V. All rights reserved.

A comparative study of space radiation organ doses and associated cancer risks using PHITS and HZETRN.

PubMed

Bahadori, Amir A; Sato, Tatsuhiko; Slaba, Tony C; Shavers, Mark R; Semones, Edward J; Van Baalen, Mary; Bolch, Wesley E

2013-10-21

NASA currently uses one-dimensional deterministic transport to generate values of the organ dose equivalent needed to calculate stochastic radiation risk following crew space exposures. In this study, organ absorbed doses and dose equivalents are calculated for 50th percentile male and female astronaut phantoms using both the NASA High Charge and Energy Transport Code to perform one-dimensional deterministic transport and the Particle and Heavy Ion Transport Code System to perform three-dimensional Monte Carlo transport. Two measures of radiation risk, effective dose and risk of exposure-induced death (REID) are calculated using the organ dose equivalents resulting from the two methods of radiation transport. For the space radiation environments and simplified shielding configurations considered, small differences (<8%) in the effective dose and REID are found. However, for the galactic cosmic ray (GCR) boundary condition, compensating errors are observed, indicating that comparisons between the integral measurements of complex radiation environments and code calculations can be misleading. Code-to-code benchmarks allow for the comparison of differential quantities, such as secondary particle differential fluence, to provide insight into differences observed in integral quantities for particular components of the GCR spectrum.

A comparative study of space radiation organ doses and associated cancer risks using PHITS and HZETRN

NASA Astrophysics Data System (ADS)

Bahadori, Amir A.; Sato, Tatsuhiko; Slaba, Tony C.; Shavers, Mark R.; Semones, Edward J.; Van Baalen, Mary; Bolch, Wesley E.

2013-10-01

NASA currently uses one-dimensional deterministic transport to generate values of the organ dose equivalent needed to calculate stochastic radiation risk following crew space exposures. In this study, organ absorbed doses and dose equivalents are calculated for 50th percentile male and female astronaut phantoms using both the NASA High Charge and Energy Transport Code to perform one-dimensional deterministic transport and the Particle and Heavy Ion Transport Code System to perform three-dimensional Monte Carlo transport. Two measures of radiation risk, effective dose and risk of exposure-induced death (REID) are calculated using the organ dose equivalents resulting from the two methods of radiation transport. For the space radiation environments and simplified shielding configurations considered, small differences (<8%) in the effective dose and REID are found. However, for the galactic cosmic ray (GCR) boundary condition, compensating errors are observed, indicating that comparisons between the integral measurements of complex radiation environments and code calculations can be misleading. Code-to-code benchmarks allow for the comparison of differential quantities, such as secondary particle differential fluence, to provide insight into differences observed in integral quantities for particular components of the GCR spectrum.

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.

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.

Monte Carlo Estimation of Absorbed Dose Distributions Obtained from Heterogeneous 106Ru Eye Plaques.

PubMed

Zaragoza, Francisco J; Eichmann, Marion; Flühs, Dirk; Sauerwein, Wolfgang; Brualla, Lorenzo

2017-09-01

The distribution of the emitter substance in 106 Ru eye plaques is usually assumed to be homogeneous for treatment planning purposes. However, this distribution is never homogeneous, and it widely differs from plaque to plaque due to manufacturing factors. By Monte Carlo simulation of radiation transport, we study the absorbed dose distribution obtained from the specific CCA1364 and CCB1256 106 Ru plaques, whose actual emitter distributions were measured. The idealized, homogeneous CCA and CCB plaques are also simulated. The largest discrepancy in depth dose distribution observed between the heterogeneous and the homogeneous plaques was 7.9 and 23.7% for the CCA and CCB plaques, respectively. In terms of isodose lines, the line referring to 100% of the reference dose penetrates 0.2 and 1.8 mm deeper in the case of heterogeneous CCA and CCB plaques, respectively, with respect to the homogeneous counterpart. The observed differences in absorbed dose distributions obtained from heterogeneous and homogeneous plaques are clinically irrelevant if the plaques are used with a lateral safety margin of at least 2 mm. However, these differences may be relevant if the plaques are used in eccentric positioning.

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.

Changes in radiation dose with variations in human anatomy: moderately and severely obese adults.

PubMed

Clark, Landon D; Stabin, Michael G; Fernald, Michael J; Brill, Aaron B

2010-06-01

The phantoms used in standardized dose assessment are based on a median (i.e., 50th percentile) individual of a large population, for example, adult males or females or children of a particular age. Here we describe phantoms that model instead the influence of obesity on specific absorbed fractions (SAFs) and dose factors in adults. The literature was reviewed to evaluate how individual organ sizes change with variations in body weight in mildly and severely obese adult men and women. On the basis of the literature evaluation, changes were made to our deformable reference adult male and female total-body models. Monte Carlo simulations of radiation transport were performed. SAFs for photons were generated for mildly and severely obese adults, and comparisons were made to the reference (50th) percentile SAF values. SAFs studied between the obese phantoms and the 50th percentile reference phantoms were not significantly different from the reference 50th percentile individual, with the exception of intestines irradiating some abdominal organs, because of an increase in separation between folds caused by an increase in mesenteric adipose deposits. Some low-energy values for certain organ pairs were different, possibly due only to the statistical variability of the data at these low energies. The effect of obesity on dose calculations for internal emitters is minor and may be neglected in the routine use of standardized dose estimates.

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

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

Comparison between Measured and Simulated Radiation Doses in the Matoroshka-R Spherical phantom Experiment#1 and Area Monitoring aboard International Space Station using PADLES from May - Sep. 2012

NASA Astrophysics Data System (ADS)

Nagamatsu, Aiko; Tolochek, Raisa; Shurshakov, Vyacheslav; Nikolaev, Igor; Tawara, Hiroko; Kitajo, Keiichi; Shimada, Ken

The measurement of radiation environmental parameters in space is essential to support radiation risk assessments for astronauts and establish a benchmark for space radiation models for present and future human space activities. Since Japanese Experiment Module ‘KIBO’ was attached to the International Space Station (ISS) in 2008, we have been performing continuous space radiation dosimetery using a PADLES (Passive Dosimeter for Life-Science Experiments in Space) consisting of CR-39 PNTDs (Plastic Nuclear track detectors) and TLD-MSOs (Mg2SiO4:Tb) for various space experiments onboard the ‘KIBO’ part of the ISS. The MATROSHKA-R experiments aims to verify of dose distributions in a human body during space flight. The phantom consists of tissue equivalent material covered by a poncho jacket with 32 pockets on the surface. 20 container rods with dosimeters can be struck into the spherical phantom. Its diameter is 370 mm and it is 32 kg in weight. The first experiment onboard the KIBO at Forward No.2 area (JPM1F2 Rack2) was conducted over 114 days from 21 May to 12 September 2012 (the installation schedule inside the phantom) on the way to solar cycle 24th upward curve. 16 PADLES packages were deployed into 16 poncho pockets on the surface of the spherical phantom. Another 12 PADLES packages were deployed inside 4 rods (3 packages per rod in the outer, middle and inner side). Area monitoring in the KIBO was conducted in the same period (Area PADLES series #8 from 15 May to 16 September, 2012). Absorbed doses were measured at 17 area monitoring points in the KIBO and 28 locations (16 packages in poncho pockets and 12 inside 4 rods) in the phantom. The maximum value measured with the PADLES in the poncho pockets on the surface of the spherical phantom facing the outer wall was 0.43 mGy/day and the minimum value measured with the PADLES in the poncho pockets on the surface of the spherical phantom facing the KIBO interior was 0.30 mGy/day. The maximum absorbed doses measured inside rods was 0.28 mGy/day and the minimum value was 0.19 mGy/day. This indicates doses measured from the dosimeters placed in the outer side of each rod are relatively high compared to the doses placed in the center of rod. At this time, we also would like to show the preliminary results of comparative study between measured and Simulated Radiation Doses using the Particle and Heavy Ion Transport code System (PHITS) calculations with well developed shielding model of the KIBO and numerical spherical phantom inside.

Bayesian estimation of dose thresholds

NASA Technical Reports Server (NTRS)

Groer, P. G.; Carnes, B. A.

2003-01-01

An example is described of Bayesian estimation of radiation absorbed dose thresholds (subsequently simply referred to as dose thresholds) using a specific parametric model applied to a data set on mice exposed to 60Co gamma rays and fission neutrons. A Weibull based relative risk model with a dose threshold parameter was used to analyse, as an example, lung cancer mortality and determine the posterior density for the threshold dose after single exposures to 60Co gamma rays or fission neutrons from the JANUS reactor at Argonne National Laboratory. The data consisted of survival, censoring times and cause of death information for male B6CF1 unexposed and exposed mice. The 60Co gamma whole-body doses for the two exposed groups were 0.86 and 1.37 Gy. The neutron whole-body doses were 0.19 and 0.38 Gy. Marginal posterior densities for the dose thresholds for neutron and gamma radiation were calculated with numerical integration and found to have quite different shapes. The density of the threshold for 60Co is unimodal with a mode at about 0.50 Gy. The threshold density for fission neutrons declines monotonically from a maximum value at zero with increasing doses. The posterior densities for all other parameters were similar for the two radiation types.

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

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

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.

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.

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.

Hydrogen breath test for the diagnosis of lactose intolerance, is the routine sugar load the best one?

PubMed Central

Argnani, Fiorenza; Camillo, Mauro Di; Marinaro, Vanessa; Foglietta, Tiziana; Avallone, Veronica; Cannella, Carlo; Vernia, Piero

2008-01-01

AIM: To evaluate the prevalence of lactose intolerance (LI) following a load of 12.5 g in patients diagnosed as high-grade malabsorbers using the hydrogen breath test (HBT)-25. METHODS: Ninety patients showing high-grade malabsorption at HBT-25 were submitted to a second HBT with a lactose load of 12.5 g. Peak hydrogen production, area under the curve of hydrogen excretion and occurrence of symptoms were recorded. RESULTS: Only 16 patients (17.77%) with positive HBT-25 proved positive at HBT-12.5. Hydrogen production was lower as compared to HBT-25 (peak value 21.55 parts per million (ppm) ± 29.54 SD vs 99.43 ppm ± 40.01 SD; P < 0.001). Symptoms were present in only 13 patients. The absence of symptoms during the high-dose test has a high negative predictive value (0.84) for a negative low-dose test. The presence of symptoms during the first test was not useful for predicting a positive low-dose test (positive predictive value 0.06-0.31). CONCLUSION: Most patients with a positive HBT-25 normally absorb a lower dose of lactose and a strict lactose restriction on the basis of a “standard” HBT is, in most instances, unnecessary. Thus, the 25 g lactose tolerance test should probably be substituted by the 12.5 g test in the diagnosis of LI, and in providing dietary guidelines to patients with suspected lactose malabsorption/intolerance. PMID:18985811

Hydrogen breath test for the diagnosis of lactose intolerance, is the routine sugar load the best one?

PubMed

Argnani, Fiorenza; Di Camillo, Mauro; Marinaro, Vanessa; Foglietta, Tiziana; Avallone, Veronica; Cannella, Carlo; Vernia, Piero

2008-10-28

To evaluate the prevalence of lactose intolerance (LI) following a load of 12.5 g in patients diagnosed as high-grade malabsorbers using the hydrogen breath test (HBT)-25. Ninety patients showing high-grade malabsorption at HBT-25 were submitted to a second HBT with a lactose load of 12.5 g. Peak hydrogen production, area under the curve of hydrogen excretion and occurrence of symptoms were recorded. Only 16 patients (17.77%) with positive HBT-25 proved positive at HBT-12.5. Hydrogen production was lower as compared to HBT-25 (peak value 21.55 parts per million (ppm) +/- 29.54 SD vs 99.43 ppm +/- 40.01 SD; P < 0.001). Symptoms were present in only 13 patients. The absence of symptoms during the high-dose test has a high negative predictive value (0.84) for a negative low-dose test. The presence of symptoms during the first test was not useful for predicting a positive low-dose test (positive predictive value 0.06-0.31). Most patients with a positive HBT-25 normally absorb a lower dose of lactose and a strict lactose restriction on the basis of a "standard" HBT is, in most instances, unnecessary. Thus, the 25 g lactose tolerance test should probably be substituted by the 12.5 g test in the diagnosis of LI, and in providing dietary guidelines to patients with suspected lactose malabsorption/intolerance.

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

Single dose pharmacokinetics, pharmacodynamics, tolerability and safety of BAY 60-5521, a potent inhibitor of cholesteryl ester transfer protein.

PubMed

Boettcher, Michael-Friedrich; Heinig, Roland; Schmeck, Carsten; Kohlsdorfer, Christian; Ludwig, Matthias; Schaefer, Anja; Gelfert-Peukert, Sabine; Wensing, Georg; Weber, Olaf

2012-02-01

To determine pharmacokinetics (PK), pharmacodynamics (PD), tolerability and safety of BAY 60-5521, a potent inhibitor of cholesteryl ester transfer protein (CETP). The first in man (FIM) study investigated the safety, tolerability, pharmacodynamics and pharmacokinetics in healthy male subjects following administration of single oral doses. The study was performed using a randomized, single-blind, placebo-controlled, single dose-escalation design. Thirty-eight young healthy male subjects (aged 20-45 years) received an oral dose of 5, 12.5, 25 or 50 mg BAY 60-5521 (n= 28) or were treated with a placebo (n= 10). In all four dose steps, only one adverse event (25 mg; mild skin rash) was considered drug related. Clinical laboratory parameters showed no clinically relevant changes. A clear dose-dependent CETP inhibition could be demonstrated starting at a dose of 5 mg. At a dose of 25 mg, a CETP inhibition >50% over 18 h was observed. After 50 mg, CETP inhibition >50% lasted more than 50 h. Twenty-four h after administration mean HDL-C-values showed a nearly dose-proportional increase. Following administration of 50 mg, a significant HDL-C increase of about 30% relative to baseline values was found. BAY 60-5521 was slowly absorbed reaching maximum concentrations in plasma after 4 to 6 h. The disposition in plasma was multi-exponential with an estimated mean terminal half-life of 76 to 144 h. BAY 60-5521 was clinically safe and well tolerated. No effects on heart rate, blood pressure and ECG recordings were observed during the study. A clear pharmacodynamic effect on CETP inhibition and HDL could be demonstrated. © 2011 The Authors. British Journal of Clinical Pharmacology © 2011 The British Pharmacological Society.

Human absorption and retention of polonium-210 from caribou meat.

PubMed

Thomas, P A; Fisenne, I; Chorney, D; Baweja, A S; Tracy, B L

2001-01-01

The gastrointestinal (GI) absorption factors and the biological retention times for polonium were determined for a group of 14 volunteers--seven men and seven women--from Saskatoon, Saskatchewan, Canada. Each volunteer consumed 2.0 kg of caribou meat containing known amounts of naturally occurring 210Po. Urine and faecal samples were collected for up to 65 days after meat consumption and analysed for 210Po. The average GI absorption factor for the 14 volunteers was 56 +/- 4% (range = 31-71%), not significantly different from the ICRP value of 50%. About 3% of absorbed polonium underwent prompt excretion by the urinary pathway. The remainder was retained by the body with a half-time >100 days, compared to the ICRP value of 50 days. The effect of these findings increases the dose estimate for ingestion of 210Po in food by a factor of 1.5 to 3.5. Thus, background doses to people consuming caribou and reindeer may be higher than previously thought.

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.

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

Method of absorbance correction in a spectroscopic heating value sensor

DOEpatents

Saveliev, Alexei; Jangale, Vilas Vyankatrao; Zelepouga, Sergeui; Pratapas, John

2013-09-17

A method and apparatus for absorbance correction in a spectroscopic heating value sensor in which a reference light intensity measurement is made on a non-absorbing reference fluid, a light intensity measurement is made on a sample fluid, and a measured light absorbance of the sample fluid is determined. A corrective light intensity measurement at a non-absorbing wavelength of the sample fluid is made on the sample fluid from which an absorbance correction factor is determined. The absorbance correction factor is then applied to the measured light absorbance of the sample fluid to arrive at a true or accurate absorbance for the sample fluid.

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.

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

PubMed

Beamish, David

2014-12-01

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

Organ and effective dose coefficients for cranial and caudal irradiation geometries: photons

DOE PAGES

Veinot, K. G.; Eckerman, K. F.; Hertel, N. E.

2015-05-02

With the introduction of new recommendations of the International Commission on Radiological Protection (ICRP) in Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors and the introduction of reference sex-specific computational phantoms. Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision ofmore » ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT) and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for photon irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue kerma and absorbed doses for caudal and cranial exposures to photons ranging in energy from 10 keV to 10 GeV have been performed using the MCNP6.1 radiation transport code and the adult reference phantoms of ICRP Publication 110. As with calculations reported in ICRP 116, the effects of charged-particle transport are evident when compared with values obtained by using the kerma approximation. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above similar to 30 MeV the cranial and caudal values are greater.« less

Organ and effective dose coefficients for cranial and caudal irradiation geometries: photons

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

Veinot, K. G.; Eckerman, K. F.; Hertel, N. E.

With the introduction of new recommendations of the International Commission on Radiological Protection (ICRP) in Publication 103, the methodology for determining the protection quantity, effective dose, has been modified. The modifications include changes to the defined organs and tissues, the associated tissue weighting factors, radiation weighting factors and the introduction of reference sex-specific computational phantoms. Computations of equivalent doses in organs and tissues are now performed in both the male and female phantoms and the sex-averaged values used to determine the effective dose. Dose coefficients based on the ICRP 103 recommendations were reported in ICRP Publication 116, the revision ofmore » ICRP Publication 74 and ICRU Publication 57. The coefficients were determined for the following irradiation geometries: anterior-posterior (AP), posterior-anterior (PA), right and left lateral (RLAT and LLAT), rotational (ROT) and isotropic (ISO). In this work, the methodology of ICRP Publication 116 was used to compute dose coefficients for photon irradiation of the body with parallel beams directed upward from below the feet (caudal) and directed downward from above the head (cranial). These geometries may be encountered in the workplace from personnel standing on contaminated surfaces or volumes and from overhead sources. Calculations of organ and tissue kerma and absorbed doses for caudal and cranial exposures to photons ranging in energy from 10 keV to 10 GeV have been performed using the MCNP6.1 radiation transport code and the adult reference phantoms of ICRP Publication 110. As with calculations reported in ICRP 116, the effects of charged-particle transport are evident when compared with values obtained by using the kerma approximation. At lower energies the effective dose per particle fluence for cranial and caudal exposures is less than AP orientations while above similar to 30 MeV the cranial and caudal values are greater.« less

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.

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.

Assessment of Natural Radioactivity Levels and Potential Radiological Risks of Common Building Materials Used in Bangladeshi Dwellings.

PubMed

Asaduzzaman, Khandoker; Mannan, Farhana; Khandaker, Mayeen Uddin; Farook, Mohideen Salihu; Elkezza, Aeman; Amin, Yusoff Bin Mohd; Sharma, Sailesh; Abu Kassim, Hasan Bin

2015-01-01

The concentrations of primordial radionuclides (226Ra, 232Th and 40K) in commonly used building materials (brick, cement and sand), the raw materials of cement and the by-products of coal-fired power plants (fly ash) collected from various manufacturers and suppliers in Bangladesh were determined via gamma-ray spectrometry using an HPGe detector. The results showed that the mean concentrations of 226Ra, 232Th and 40K in all studied samples slightly exceeded the typical world average values of 50 Bq kg(-1), 50 Bq kg(-1) and 500 Bq kg(-1), respectively. The activity concentrations (especially 226Ra) of fly-ash-containing cement in this study were found to be higher than those of fly-ash-free cement. To evaluate the potential radiological risk to individuals associated with these building materials, various radiological hazard indicators were calculated. The radium equivalent activity values for all samples were found to be lower than the recommended limit for building materials of 370 Bq kg(-1), with the exception of the fly ash. For most samples, the values of the alpha index and the radiological hazard (external and internal) indices were found to be within the safe limit of 1. The mean indoor absorbed dose rate was observed to be higher than the population-weighted world average of 84 nGy h(-1), and the corresponding annual effective dose for most samples fell below the recommended upper dose limit of 1 mSv y(-1). For all investigated materials, the values of the gamma index were found to be greater than 0.5 but less than 1, indicating that the gamma dose contribution from the studied building materials exceeds the exemption dose criterion of 0.3 mSv y(-1) but complies with the upper dose principle of 1 mSv y(-1).