Independent calculation-based verification of IMRT plans using a 3D dose-calculation engine
Arumugam, Sankar; Xing, Aitang; Goozee, Gary; Holloway, Lois
2013-01-01
Independent monitor unit verification of intensity-modulated radiation therapy (IMRT) plans requires detailed 3-dimensional (3D) dose verification. The aim of this study was to investigate using a 3D dose engine in a second commercial treatment planning system (TPS) for this task, facilitated by in-house software. Our department has XiO and Pinnacle TPSs, both with IMRT planning capability and modeled for an Elekta-Synergy 6 MV photon beam. These systems allow the transfer of computed tomography (CT) data and RT structures between them but do not allow IMRT plans to be transferred. To provide this connectivity, an in-house computer programme was developed to convert radiation therapy prescription (RTP) files as generated by many planning systems into either XiO or Pinnacle IMRT file formats. Utilization of the technique and software was assessed by transferring 14 IMRT plans from XiO and Pinnacle onto the other system and performing 3D dose verification. The accuracy of the conversion process was checked by comparing the 3D dose matrices and dose volume histograms (DVHs) of structures for the recalculated plan on the same system. The developed software successfully transferred IMRT plans generated by 1 planning system into the other. Comparison of planning target volume (TV) DVHs for the original and recalculated plans showed good agreement; a maximum difference of 2% in mean dose, − 2.5% in D95, and 2.9% in V95 was observed. Similarly, a DVH comparison of organs at risk showed a maximum difference of +7.7% between the original and recalculated plans for structures in both high- and medium-dose regions. However, for structures in low-dose regions (less than 15% of prescription dose) a difference in mean dose up to +21.1% was observed between XiO and Pinnacle calculations. A dose matrix comparison of original and recalculated plans in XiO and Pinnacle TPSs was performed using gamma analysis with 3%/3 mm criteria. The mean and standard deviation of pixels passing
Calculation of Dose Deposition in 3D Voxels by Heavy Ions
NASA Technical Reports Server (NTRS)
Plante, Ianik; Cucinotta, Francis A.
2010-01-01
The biological response to high-LET radiation is very different from low-LET radiation, and can be partly attributed to the energy deposition by the radiation. Several experiments, notably detection of gamma-H2AX foci by immunofluorescence, has revealed important differences in the nature and in the spatial distribution of double-strand breaks (DSB) induced by low- and high-LET radiations. Many calculations, most of which are based on amorphous track models with radial dose, have been combined with chromosome models to calculate the number and distribution of DSB within nuclei and chromosome aberrations. In this work, the Monte-Carlo track structure simulation code RITRACKS have been used to calculate directly the energy deposition in voxels (3D pixels). A cubic volume of 5 micrometers of side was irradiated by 1) 450 (1)H+ ions of 300 MeV (LET is approximately 0.3 keV/micrometer) and 2) by 1 (56)Fe26+ ion of 1 GeV/amu (LET is approximately 150 keV/micrometer). In both cases, the dose deposited in the volume is approximately 1 Gy. All energy deposition events are recorded and dose is calculated in voxels of 20 micrometers of side. The voxels are then visualized in 3D by using a color scale to represent the intensity of the dose in a voxel. This simple approach has revealed several important points which may help understand experimental observations. In both simulations, voxels which receive low dose are the most numerous, and those corresponding to electron track ends received a dose which is in the higher range. The dose voxels are distributed randomly and scattered uniformly within the volume irradiated by low-LET radiation. The distribution of the voxels shows major differences for the (56)Fe26+ ion. The track structure can still be seen, and voxels with much higher dose are found in the region corresponding to the track "core". These high-dose voxels are not found in the low-LET irradiation simulation and may be responsible for DSB that are more difficult to
Azcona, Juan Diego; Barbés, Benigno; Wang, Lilie; Burguete, Javier
2016-01-01
This paper presents a method to obtain the pencil-beam kernels that characterize a megavoltage photon beam generated in a flattening filter free (FFF) linear accelerator (linac) by deconvolution from experimental measurements at different depths. The formalism is applied to perform independent dose calculations in modulated fields. In our previous work a formalism was developed for ideal flat fluences exiting the linac's head. That framework could not deal with spatially varying energy fluences, so any deviation from the ideal flat fluence was treated as a perturbation. The present work addresses the necessity of implementing an exact analysis where any spatially varying fluence can be used such as those encountered in FFF beams. A major improvement introduced here is to handle the actual fluence in the deconvolution procedure. We studied the uncertainties associated to the kernel derivation with this method. Several Kodak EDR2 radiographic films were irradiated with a 10 MV FFF photon beam from two linacs from different vendors, at the depths of 5, 10, 15, and 20cm in polystyrene (RW3 water-equivalent phantom, PTW Freiburg, Germany). The irradiation field was a 50mm diameter circular field, collimated with a lead block. The 3D kernel for a FFF beam was obtained by deconvolution using the Hankel transform. A correction on the low dose part of the kernel was performed to reproduce accurately the experimental output factors. Error uncertainty in the kernel derivation procedure was estimated to be within 0.2%. Eighteen modulated fields used clinically in different treatment localizations were irradiated at four measurement depths (total of fifty-four film measurements). Comparison through the gamma-index to their corresponding calculated absolute dose distributions showed a number of passing points (3%, 3mm) mostly above 99%. This new procedure is more reliable and robust than the previous one. Its ability to perform accurate independent dose calculations was
Azcona, Juan Diego; Barbés, Benigno; Wang, Lilie; Burguete, Javier
2016-01-01
This paper presents a method to obtain the pencil-beam kernels that characterize a megavoltage photon beam generated in a flattening filter free (FFF) linear accelerator (linac) by deconvolution from experimental measurements at different depths. The formalism is applied to perform independent dose calculations in modulated fields. In our previous work a formalism was developed for ideal flat fluences exiting the linac's head. That framework could not deal with spatially varying energy fluences, so any deviation from the ideal flat fluence was treated as a perturbation. The present work addresses the necessity of implementing an exact analysis where any spatially varying fluence can be used such as those encountered in FFF beams. A major improvement introduced here is to handle the actual fluence in the deconvolution procedure. We studied the uncertainties associated to the kernel derivation with this method. Several Kodak EDR2 radiographic films were irradiated with a 10 MV FFF photon beam from two linacs from different vendors, at the depths of 5, 10, 15, and 20cm in polystyrene (RW3 water-equivalent phantom, PTW Freiburg, Germany). The irradiation field was a 50mm diameter circular field, collimated with a lead block. The 3D kernel for a FFF beam was obtained by deconvolution using the Hankel transform. A correction on the low dose part of the kernel was performed to reproduce accurately the experimental output factors. Error uncertainty in the kernel derivation procedure was estimated to be within 0.2%. Eighteen modulated fields used clinically in different treatment localizations were irradiated at four measurement depths (total of fifty-four film measurements). Comparison through the gamma-index to their corresponding calculated absolute dose distributions showed a number of passing points (3%, 3mm) mostly above 99%. This new procedure is more reliable and robust than the previous one. Its ability to perform accurate independent dose calculations was
NASA Astrophysics Data System (ADS)
Diego Azcona, Juan; Barbés, Benigno; Wang, Lilie; Burguete, Javier
2016-01-01
This paper presents a method to obtain the pencil-beam kernels that characterize a megavoltage photon beam generated in a flattening filter free (FFF) linear accelerator (linac) by deconvolution from experimental measurements at different depths. The formalism is applied to perform independent dose calculations in modulated fields. In our previous work a formalism was developed for ideal flat fluences exiting the linac’s head. That framework could not deal with spatially varying energy fluences, so any deviation from the ideal flat fluence was treated as a perturbation. The present work addresses the necessity of implementing an exact analysis where any spatially varying fluence can be used such as those encountered in FFF beams. A major improvement introduced here is to handle the actual fluence in the deconvolution procedure. We studied the uncertainties associated to the kernel derivation with this method. Several Kodak EDR2 radiographic films were irradiated with a 10 MV FFF photon beam from two linacs from different vendors, at the depths of 5, 10, 15, and 20cm in polystyrene (RW3 water-equivalent phantom, PTW Freiburg, Germany). The irradiation field was a 50mm diameter circular field, collimated with a lead block. The 3D kernel for a FFF beam was obtained by deconvolution using the Hankel transform. A correction on the low dose part of the kernel was performed to reproduce accurately the experimental output factors. Error uncertainty in the kernel derivation procedure was estimated to be within 0.2%. Eighteen modulated fields used clinically in different treatment localizations were irradiated at four measurement depths (total of fifty-four film measurements). Comparison through the gamma-index to their corresponding calculated absolute dose distributions showed a number of passing points (3%, 3mm) mostly above 99%. This new procedure is more reliable and robust than the previous one. Its ability to perform accurate independent dose calculations was
Visser, R.; Wauben, D. J. L.; Godart, J.; Langendijk, J. A.; Veld, A. A. van't; Korevaar, E. W.; Groot, M. de
2013-02-15
Purpose: Advanced radiotherapy treatments require appropriate quality assurance (QA) to verify 3D dose distributions. Moreover, increase in patient numbers demand efficient QA-methods. In this study, a time efficient method that combines model-based QA and measurement-based QA was developed; i.e., the hybrid-QA. The purpose of this study was to determine the reliability of the model-based QA and to evaluate time efficiency of the hybrid-QA method. Methods: Accuracy of the model-based QA was determined by comparison of COMPASS calculated dose with Monte Carlo calculations for heterogeneous media. In total, 330 intensity modulated radiation therapy (IMRT) treatment plans were evaluated based on the mean gamma index (GI) with criteria of 3%/3mm and classification of PASS (GI {<=} 0.4), EVAL (0.4 < GI > 0.6), and FAIL (GI {>=} 0.6). Agreement between model-based QA and measurement-based QA was determined for 48 treatment plans, and linac stability was verified for 15 months. Finally, time efficiency improvement of the hybrid-QA was quantified for four representative treatment plans. Results: COMPASS calculated dose was in agreement with Monte Carlo dose, with a maximum error of 3.2% in heterogeneous media with high density (2.4 g/cm{sup 3}). Hybrid-QA results for IMRT treatment plans showed an excellent PASS rate of 98% for all cases. Model-based QA was in agreement with measurement-based QA, as shown by a minimal difference in GI of 0.03 {+-} 0.08. Linac stability was high with an average GI of 0.28 {+-} 0.04. The hybrid-QA method resulted in a time efficiency improvement of 15 min per treatment plan QA compared to measurement-based QA. Conclusions: The hybrid-QA method is adequate for efficient and accurate 3D dose verification. It combines time efficiency of model-based QA with reliability of measurement-based QA and is suitable for implementation within any radiotherapy department.
Feasibility of a Multigroup Deterministic Solution Method for 3D Radiotherapy Dose Calculations
Vassiliev, Oleg N.; Wareing, Todd A.; Davis, Ian M.; McGhee, John; Barnett, Douglas; Horton, John L.; Gifford, Kent; Failla, Gregory; Titt, Uwe; Mourtada, Firas
2008-01-01
Purpose To investigate the potential of a novel deterministic solver, Attila, for external photon beam radiotherapy dose calculations. Methods and Materials Two hypothetical cases for prostate and head and neck cancer photon beam treatment plans were calculated using Attila and EGSnrc Monte Carlo simulations. Open beams were modeled as isotropic photon point sources collimated to specified field sizes (100 cm SSD). The sources had a realistic energy spectrum calculated by Monte Carlo for a Varian Clinac 2100 operated in a 6MV photon mode. The Attila computational grids consisted of 106,000 elements, or 424,000 spatial degrees of freedom, for the prostate case, and 123,000 tetrahedral elements, or 492,000 spatial degrees of freedom, for the head and neck cases. Results For both cases, results demonstrate excellent agreement between Attila and EGSnrc in all areas, including the build-up regions, near heterogeneities, and at the beam penumbra. Dose agreement for 99% of the voxels was within 3% (relative point-wise difference) or 3mm distance-to-agreement criterion. Localized differences between the Attila and EGSnrc results were observed at bone and soft tissue interfaces, and are attributable to the effect of voxel material homogenization in calculating dose-to-medium in EGSnrc. For both cases, Attila calculation times were under 20 CPU minutes on a single 2.2 GHz AMD Opteron processor. Conclusions The methods in Attila have the potential to be the basis for an efficient dose engine for patient specific treatment planning, providing accuracy similar to that obtained by Monte Carlo. PMID:18722273
Ma, M; Rouabhi, O; Flynn, R; Xia, J; Bayouth, J
2014-06-01
Purpose: To evaluate the dosimetric difference between 3D and 4Dweighted dose calculation using patient specific respiratory trace and deformable image registration for stereotactic body radiation therapy in lung tumors. Methods: Two dose calculation techniques, 3D and 4D-weighed dose calculation, were used for dosimetric comparison for 9 lung cancer patients. The magnitude of the tumor motion varied from 3 mm to 23 mm. Breath-hold exhale CT was used for 3D dose calculation with ITV generated from the motion observed from 4D-CT. For 4D-weighted calculation, dose of each binned CT image from the ten breathing amplitudes was first recomputed using the same planning parameters as those used in the 3D calculation. The dose distribution of each binned CT was mapped to the breath-hold CT using deformable image registration. The 4D-weighted dose was computed by summing the deformed doses with the temporal probabilities calculated from their corresponding respiratory traces. Dosimetric evaluation criteria includes lung V20, mean lung dose, and mean tumor dose. Results: Comparing with 3D calculation, lung V20, mean lung dose, and mean tumor dose using 4D-weighted dose calculation were changed by −0.67% ± 2.13%, −4.11% ± 6.94% (−0.36 Gy ± 0.87 Gy), −1.16% ± 1.36%(−0.73 Gy ± 0.85 Gy) accordingly. Conclusion: This work demonstrates that conventional 3D dose calculation method may overestimate the lung V20, MLD, and MTD. The absolute difference between 3D and 4D-weighted dose calculation in lung tumor may not be clinically significant. This research is supported by Siemens Medical Solutions USA, Inc and Iowa Center for Research By Undergraduates.
Boggula, Ramesh; Jahnke, Lennart; Wertz, Hansjoerg; Lohr, Frank; Wenz, Frederik
2011-11-15
Purpose: Fast and reliable comprehensive quality assurance tools are required to validate the safety and accuracy of complex intensity-modulated radiotherapy (IMRT) plans for prostate treatment. In this study, we evaluated the performance of the COMPASS system for both off-line and potential online procedures for the verification of IMRT treatment plans. Methods and Materials: COMPASS has a dedicated beam model and dose engine, it can reconstruct three-dimensional dose distributions on the patient anatomy based on measured fluences using either the MatriXX two-dimensional (2D) array (offline) or a 2D transmission detector (T2D) (online). For benchmarking the COMPASS dose calculation, various dose-volume indices were compared against Monte Carlo-calculated dose distributions for five prostate patient treatment plans. Gamma index evaluation and absolute point dose measurements were also performed in an inhomogeneous pelvis phantom using extended dose range films and ion chamber for five additional treatment plans. Results: MatriXX-based dose reconstruction showed excellent agreement with the ion chamber (<0.5%, except for one treatment plan, which showed 1.5%), film ({approx}100% pixels passing gamma criteria 3%/3 mm) and mean dose-volume indices (<2%). The T2D based dose reconstruction showed good agreement as well with ion chamber (<2%), film ({approx}99% pixels passing gamma criteria 3%/3 mm), and mean dose-volume indices (<5.5%). Conclusion: The COMPASS system qualifies for routine prostate IMRT pretreatment verification with the MatriXX detector and has the potential for on-line verification of treatment delivery using T2D.
Valdes, Gilmer; Robinson, Clifford; Lee, Percy; Morel, Delphine; Low, Daniel; Iwamoto, Keisuke S; Lamb, James M
2015-01-01
Four-dimensional (4D) dose calculations for lung cancer radiotherapy have been technically feasible for a number of years but have not become standard clinical practice. The purpose of this study was to determine if clinically significant differences in tumor control probability (TCP) exist between 3D and 4D dose calculations so as to inform the decision whether 4D dose calculations should be used routinely for treatment planning. Radiotherapy plans for Stage I-II lung cancer were created for 8 patients. Clinically acceptable treatment plans were created with dose calculated on the end-exhale 4D computed tomography (CT) phase using a Monte Carlo algorithm. Dose was then projected onto the remaining 9 phases of 4D-CT using the Monte Carlo algorithm and accumulated onto the end-exhale phase using commercially available deformable registration software. The resulting dose-volume histograms (DVH) of the gross tumor volume (GTV), planning tumor volume (PTV), and PTVsetup were compared according to target coverage and dose. The PTVsetup was defined as a volume including the GTV and a margin for setup uncertainties but not for respiratory motion. TCPs resulting from these DVHs were estimated using a wide range of alphas, betas, and tumor cell densities. Differences of up to 5Gy were observed between 3D and 4D calculations for a PTV with highly irregular shape. When the TCP was calculated using the resulting DVHs for fractionation schedules typically used in stereotactic body radiation therapy (SBRT), the TCP differed at most by 5% between 4D and 3D cases, and in most cases, it was by less than 1%. We conclude that 4D dose calculations are not necessary for most cases treated with SBRT, but they might be valuable for irregularly shaped target volumes. If 4D calculations are used, 4D DVHs should be evaluated on volumes that include margin for setup uncertainty but not respiratory motion.
Valdes, Gilmer; Robinson, Clifford; Lee, Percy; Morel, Delphine; Low, Daniel; Iwamoto, Keisuke S.; Lamb, James M.
2015-04-01
Four-dimensional (4D) dose calculations for lung cancer radiotherapy have been technically feasible for a number of years but have not become standard clinical practice. The purpose of this study was to determine if clinically significant differences in tumor control probability (TCP) exist between 3D and 4D dose calculations so as to inform the decision whether 4D dose calculations should be used routinely for treatment planning. Radiotherapy plans for Stage I-II lung cancer were created for 8 patients. Clinically acceptable treatment plans were created with dose calculated on the end-exhale 4D computed tomography (CT) phase using a Monte Carlo algorithm. Dose was then projected onto the remaining 9 phases of 4D-CT using the Monte Carlo algorithm and accumulated onto the end-exhale phase using commercially available deformable registration software. The resulting dose-volume histograms (DVH) of the gross tumor volume (GTV), planning tumor volume (PTV), and PTV{sub setup} were compared according to target coverage and dose. The PTV{sub setup} was defined as a volume including the GTV and a margin for setup uncertainties but not for respiratory motion. TCPs resulting from these DVHs were estimated using a wide range of alphas, betas, and tumor cell densities. Differences of up to 5 Gy were observed between 3D and 4D calculations for a PTV with highly irregular shape. When the TCP was calculated using the resulting DVHs for fractionation schedules typically used in stereotactic body radiation therapy (SBRT), the TCP differed at most by 5% between 4D and 3D cases, and in most cases, it was by less than 1%. We conclude that 4D dose calculations are not necessary for most cases treated with SBRT, but they might be valuable for irregularly shaped target volumes. If 4D calculations are used, 4D DVHs should be evaluated on volumes that include margin for setup uncertainty but not respiratory motion.
Calculation of Dose Deposition in 3D Voxels by Heavy Ions and Simulation of gamma-H2AX Experiments
NASA Technical Reports Server (NTRS)
Plante, I.; Ponomarev, A. L.; Wang, M.; Cucinotta, F. A.
2011-01-01
The biological response to high-LET radiation is different from low-LET radiation due to several factors, notably difference in energy deposition and formation of radiolytic species. Of particular importance in radiobiology is the formation of double-strand breaks (DSB), which can be detected by -H2AX foci experiments. These experiments has revealed important differences in the spatial distribution of DSB induced by low- and high-LET radiations [1,2]. To simulate -H2AX experiments, models based on amorphous track with radial dose are often combined with random walk chromosome models [3,4]. In this work, a new approach using the Monte-Carlo track structure code RITRACKS [5] and chromosome models have been used to simulate DSB formation. At first, RITRACKS have been used to simulate the irradiation of a cubic volume of 5 m by 1) 450 1H+ ions of 300 MeV (LET 0.3 keV/ m) and 2) by 1 56Fe26+ ion of 1 GeV/amu (LET 150 keV/ m). All energy deposition events are recorded to calculate dose in voxels of 20 m. The dose voxels are distributed randomly and scattered uniformly within the volume irradiated by low-LET radiation. Many differences are found in the spatial distribution of dose voxels for the 56Fe26+ ion. The track structure can be distinguished, and voxels with very high dose are found in the region corresponding to the track "core". These high-dose voxels are not found in the low-LET irradiation simulation and indicate clustered energy deposition, which may be responsible for complex DSB. In the second step, assuming that DSB will be found only in voxels where energy is deposited by the radiation, the intersection points between voxels with dose > 0 and simulated chromosomes were obtained. The spatial distribution of the intersection points is similar to -H2AX foci experiments. These preliminary results suggest that combining stochastic track structure and chromosome models could be a good approach to understand radiation-induced DSB and chromosome aberrations.
NASA Astrophysics Data System (ADS)
Pacilio, Massimiliano; Amato, Ernesto; Lanconelli, Nico; Basile, Chiara; Torres, Leonel Alberto; Botta, Francesca; Ferrari, Mahila; Cornejo Diaz, Nestor; Coca Perez, Marco; Fernández, María; Lassmann, Michael; Vergara Gil, Alex; Cremonesi, Marta
2015-03-01
This study compares 3D dose distributions obtained with voxel S values (VSVs) for soft tissue, calculated by several methods at their current state-of-the-art, varying the degree of image blurring. The methods were: 1) convolution of Dose Point Kernel (DPK) for water, using a scaling factor method; 2) an analytical model (AM), fitting the deposited energy as a function of the source-target distance; 3) a rescaling method (RSM) based on a set of high-resolution VSVs for each isotope; 4) local energy deposition (LED). VSVs calculated by direct Monte Carlo simulations were assumed as reference. Dose distributions were calculated considering spheroidal clusters with various sizes (251, 1237 and 4139 voxels of 3 mm size), uniformly filled with 131I, 177Lu, 188Re or 90Y. The activity distributions were blurred with Gaussian filters of various widths (6, 8 and 12 mm). Moreover, 3D-dosimetry was performed for 10 treatments with 90Y derivatives. Cumulative Dose Volume Histograms (cDVHs) were compared, studying the differences in D95%, D50% or Dmax (ΔD95%, ΔD50% and ΔDmax) and dose profiles. For unblurred spheroidal clusters, ΔD95%, ΔD50% and ΔDmax were mostly within some percents, slightly higher for 177Lu with DPK (8%) and RSM (12%) and considerably higher for LED (ΔD95% up to 59%). Increasing the blurring, differences decreased and also LED yielded very similar results, but D95% and D50% underestimations between 30-60% and 15-50%, respectively (with respect to 3D-dosimetry with unblurred distributions), were evidenced. Also for clinical images (affected by blurring as well), cDVHs differences for most methods were within few percents, except for slightly higher differences with LED, and almost systematic for dose profiles with DPK (-1.2%), AM (-3.0%) and RSM (4.5%), whereas showed an oscillating trend with LED. The major concern for 3D-dosimetry on clinical SPECT images is more strongly represented by image blurring than by differences among the VSVs
Mapping motion from 4D-MRI to 3D-CT for use in 4D dose calculations: A technical feasibility study
Boye, Dirk; Lomax, Tony; Knopf, Antje
2013-06-15
Purpose: Target sites affected by organ motion require a time resolved (4D) dose calculation. Typical 4D dose calculations use 4D-CT as a basis. Unfortunately, 4D-CT images have the disadvantage of being a 'snap-shot' of the motion during acquisition and of assuming regularity of breathing. In addition, 4D-CT acquisitions involve a substantial additional dose burden to the patient making many, repeated 4D-CT acquisitions undesirable. Here the authors test the feasibility of an alternative approach to generate patient specific 4D-CT data sets. Methods: In this approach motion information is extracted from 4D-MRI. Simulated 4D-CT data sets [which the authors call 4D-CT(MRI)] are created by warping extracted deformation fields to a static 3D-CT data set. The employment of 4D-MRI sequences for this has the advantage that no assumptions on breathing regularity are made, irregularities in breathing can be studied and, if necessary, many repeat imaging studies (and consequently simulated 4D-CT data sets) can be performed on patients and/or volunteers. The accuracy of 4D-CT(MRI)s has been validated by 4D proton dose calculations. Our 4D dose algorithm takes into account displacements as well as deformations on the originating 4D-CT/4D-CT(MRI) by calculating the dose of each pencil beam based on an individual time stamp of when that pencil beam is applied. According to corresponding displacement and density-variation-maps the position and the water equivalent range of the dose grid points is adjusted at each time instance. Results: 4D dose distributions, using 4D-CT(MRI) data sets as input were compared to results based on a reference conventional 4D-CT data set capturing similar motion characteristics. Almost identical 4D dose distributions could be achieved, even though scanned proton beams are very sensitive to small differences in the patient geometry. In addition, 4D dose calculations have been performed on the same patient, but using 4D-CT(MRI) data sets based on
Kauweloa, Kevin I; Gutierrez, Alonso N; Stathakis, Sotirios; Papanikolaou, Niko; Mavroidis, Panayiotis
2016-07-01
A toolkit has been developed for calculating the 3-dimensional biological effective dose (BED) distributions in multi-phase, external beam radiotherapy treatments such as those applied in liver stereotactic body radiation therapy (SBRT) and in multi-prescription treatments. This toolkit also provides a wide range of statistical results related to dose and BED distributions. MATLAB 2010a, version 7.10 was used to create this GUI toolkit. The input data consist of the dose distribution matrices, organ contour coordinates, and treatment planning parameters from the treatment planning system (TPS). The toolkit has the capability of calculating the multi-phase BED distributions using different formulas (denoted as true and approximate). Following the calculations of the BED distributions, the dose and BED distributions can be viewed in different projections (e.g. coronal, sagittal and transverse). The different elements of this toolkit are presented and the important steps for the execution of its calculations are illustrated. The toolkit is applied on brain, head & neck and prostate cancer patients, who received primary and boost phases in order to demonstrate its capability in calculating BED distributions, as well as measuring the inaccuracy and imprecision of the approximate BED distributions. Finally, the clinical situations in which the use of the present toolkit would have a significant clinical impact are indicated.
Van Uytven, Eric Van Beek, Timothy; McCowan, Peter M.; Chytyk-Praznik, Krista; Greer, Peter B.; McCurdy, Boyd M. C.
2015-12-15
Purpose: Radiation treatments are trending toward delivering higher doses per fraction under stereotactic radiosurgery and hypofractionated treatment regimens. There is a need for accurate 3D in vivo patient dose verification using electronic portal imaging device (EPID) measurements. This work presents a model-based technique to compute full three-dimensional patient dose reconstructed from on-treatment EPID portal images (i.e., transmission images). Methods: EPID dose is converted to incident fluence entering the patient using a series of steps which include converting measured EPID dose to fluence at the detector plane and then back-projecting the primary source component of the EPID fluence upstream of the patient. Incident fluence is then recombined with predicted extra-focal fluence and used to calculate 3D patient dose via a collapsed-cone convolution method. This method is implemented in an iterative manner, although in practice it provides accurate results in a single iteration. The robustness of the dose reconstruction technique is demonstrated with several simple slab phantom and nine anthropomorphic phantom cases. Prostate, head and neck, and lung treatments are all included as well as a range of delivery techniques including VMAT and dynamic intensity modulated radiation therapy (IMRT). Results: Results indicate that the patient dose reconstruction algorithm compares well with treatment planning system computed doses for controlled test situations. For simple phantom and square field tests, agreement was excellent with a 2%/2 mm 3D chi pass rate ≥98.9%. On anthropomorphic phantoms, the 2%/2 mm 3D chi pass rates ranged from 79.9% to 99.9% in the planning target volume (PTV) region and 96.5% to 100% in the low dose region (>20% of prescription, excluding PTV and skin build-up region). Conclusions: An algorithm to reconstruct delivered patient 3D doses from EPID exit dosimetry measurements was presented. The method was applied to phantom and patient
Park, J; Lee, J; Kim, H; Kim, I; Ye, S
2015-06-15
Purpose: To evaluate the effect of a tungsten eye-shield on the dose distribution of a patient. Methods: A 3D scanner was used to extract the dimension and shape of a tungsten eye-shield in the STL format. Scanned data was transferred into a 3D printer. A dummy eye shield was then produced using bio-resin (3D systems, VisiJet M3 Proplast). For a patient with mucinous carcinoma, the planning CT was obtained with the dummy eye-shield placed on the patient’s right eye. Field shaping of 6 MeV was performed using a patient-specific cerrobend block on the 15 x 15 cm{sup 2} applicator. The gantry angle was 330° to cover the planning target volume near by the lens. EGS4/BEAMnrc was commissioned from our measurement data from a Varian 21EX. For the CT-based dose calculation using EGS4/DOSXYZnrc, the CT images were converted to a phantom file through the ctcreate program. The phantom file had the same resolution as the planning CT images. By assigning the CT numbers of the dummy eye-shield region to 17000, the real dose distributions below the tungsten eye-shield were calculated in EGS4/DOSXYZnrc. In the TPS, the CT number of the dummy eye-shield region was assigned to the maximum allowable CT number (3000). Results: As compared to the maximum dose, the MC dose on the right lens or below the eye shield area was less than 2%, while the corresponding RTP calculated dose was an unrealistic value of approximately 50%. Conclusion: Utilizing a 3D scanner and a 3D printer, a dummy eye-shield for electron treatment can be easily produced. The artifact-free CT images were successfully incorporated into the CT-based Monte Carlo simulations. The developed method was useful in predicting the realistic dose distributions around the lens blocked with the tungsten shield.
Poder, Joel; Corde, Stéphanie
2013-12-15
Purpose: The purpose of this study was to measure the dose distributions for different Radiation Oncology Physics and Engineering Services, Australia (ROPES) type eye plaques loaded with I-125 (model 6711) seeds using GafChromic{sup ®} EBT3 films, in order to verify the dose distributions in the Plaque Simulator™ (PS) ophthalmic 3D treatment planning system. The brachytherapy module of RADCALC{sup ®} was used to independently check the dose distributions calculated by PS. Correction factors were derived from the measured data to be used in PS to account for the effect of the stainless steel ROPES plaque backing on the 3D dose distribution.Methods: Using GafChromic{sup ®} EBT3 films inserted in a specially designed Solid Water™ eye ball phantom, dose distributions were measured three-dimensionally both along and perpendicular to I-125 (model 6711) loaded ROPES eye plaque's central axis (CAX) with 2 mm depth increments. Each measurement was performed in full scatter conditions both with and without the stainless steel plaque backing attached to the eye plaque, to assess its effect on the dose distributions. Results were compared to the dose distributions calculated by Plaque Simulator™ and checked independently with RADCALC{sup ®}.Results: The EBT3 film measurements without the stainless steel backing were found to agree with PS and RADCALC{sup ®} to within 2% and 4%, respectively, on the plaque CAX. Also, RADCALC{sup ®} was found to agree with PS to within 2%. The CAX depth doses measured using EBT3 film with the stainless steel backing were observed to result in a 4% decrease relative to when the backing was not present. Within experimental uncertainty, the 4% decrease was found to be constant with depth and independent of plaque size. Using a constant dose correction factor of T= 0.96 in PS, where the calculated dose for the full water scattering medium is reduced by 4% in every voxel in the dose grid, the effect of the plaque backing was accurately
NASA Technical Reports Server (NTRS)
Plante, Ianik; Cucinotta, Francis A.
2010-01-01
Heavy ions have gained considerable importance in radiotherapy due to their advantageous dose distribution profile and high Relative Biological Effectiveness (RBE). Heavy ions are difficult to produce on Earth, but they are present in space and it is impossible at this moment to completely shield astronauts from them. The risk of these radiations is poorly understood, which is a concern for a 3-years Mars mission. The effects of radiation are mainly due to DNA damage such as DNA double-strand breaks (DSBs), although non-targeted effects are also very important. DNA can be damaged by the direct interaction of radiation and by reactions with chemical species produced by the radiolysis of water. The energy deposition is of crucial importance to understand biological effects of radiation. Therefore, much effort has been done recently to improve models of radiation tracks.
Optical-CT imaging of complex 3D dose distributions
NASA Astrophysics Data System (ADS)
Oldham, Mark; Kim, Leonard; Hugo, Geoffrey
2005-04-01
The limitations of conventional dosimeters restrict the comprehensiveness of verification that can be performed for advanced radiation treatments presenting an immediate and substantial problem for clinics attempting to implement these techniques. In essence, the rapid advances in the technology of radiation delivery have not been paralleled by corresponding advances in the ability to verify these treatments. Optical-CT gel-dosimetry is a relatively new technique with potential to address this imbalance by providing high resolution 3D dose maps in polymer and radiochromic gel dosimeters. We have constructed a 1st generation optical-CT scanner capable of high resolution 3D dosimetry and applied it to a number of simple and increasingly complex dose distributions including intensity-modulated-radiation-therapy (IMRT). Prior to application to IMRT, the robustness of optical-CT gel dosimetry was investigated on geometry and variable attenuation phantoms. Physical techniques and image processing methods were developed to minimize deleterious effects of refraction, reflection, and scattered laser light. Here we present results of investigations into achieving accurate high-resolution 3D dosimetry with optical-CT, and show clinical examples of 3D IMRT dosimetry verification. In conclusion, optical-CT gel dosimetry can provide high resolution 3D dose maps that greatly facilitate comprehensive verification of complex 3D radiation treatments. Good agreement was observed at high dose levels (>50%) between planned and measured dose distributions. Some systematic discrepancies were observed however (rms discrepancy 3% at high dose levels) indicating further work is required to eliminate confounding factors presently compromising the accuracy of optical-CT 3D gel-dosimetry.
Application of DYNA3D in large scale crashworthiness calculations
Benson, D.J.; Hallquist, J.O.; Igarashi, M.; Shimomaki, K.; Mizuno, M.
1986-01-01
This paper presents an example of an automobile crashworthiness calculation. Based on our experiences with the example calculation, we make recommendations to those interested in performing crashworthiness calculations. The example presented in this paper was supplied by Suzuki Motor Co., Ltd., and provided a significant shakedown for the new large deformation shell capability of the DYNA3D code. 15 refs., 3 figs.
Hong, X; Gao, H
2014-06-15
Purpose: The Linear Boltzmann Transport Equation (LBTE) solved through statistical Monte Carlo (MC) method provides the accurate dose calculation in radiotherapy. This work is to investigate the alternative way for accurately solving LBTE using deterministic numerical method due to its possible advantage in computational speed from MC. Methods: Instead of using traditional spherical harmonics to approximate angular scattering kernel, our deterministic numerical method directly computes angular scattering weights, based on a new angular discretization method that utilizes linear finite element method on the local triangulation of unit angular sphere. As a Result, our angular discretization method has the unique advantage in positivity, i.e., to maintain all scattering weights nonnegative all the time, which is physically correct. Moreover, our method is local in angular space, and therefore handles the anisotropic scattering well, such as the forward-peaking scattering. To be compatible with image-guided radiotherapy, the spatial variables are discretized on the structured grid with the standard diamond scheme. After discretization, the improved sourceiteration method is utilized for solving the linear system without saving the linear system to memory. The accuracy of our 3D solver is validated using analytic solutions and benchmarked with Geant4, a popular MC solver. Results: The differences between Geant4 solutions and our solutions were less than 1.5% for various testing cases that mimic the practical cases. More details are available in the supporting document. Conclusion: We have developed a 3D LBTE solver based on a new angular discretization method that guarantees the positivity of scattering weights for physical correctness, and it has been benchmarked with Geant4 for photon dose calculation.
Multigrid calculations of 3-D turbulent viscous flows
NASA Technical Reports Server (NTRS)
Yokota, Jeffrey W.
1989-01-01
Convergence properties of a multigrid algorithm, developed to calculate compressible viscous flows, are analyzed by a vector sequence eigenvalue estimate. The full 3-D Reynolds-averaged Navier-Stokes equations are integrated by an implicit multigrid scheme while a k-epsilon turbulence model is solved, uncoupled from the flow equations. Estimates of the eigenvalue structure for both single and multigrid calculations are compared in an attempt to analyze the process as well as the results of the multigrid technique. The flow through an annular turbine is used to illustrate the scheme's ability to calculate complex 3-D flows.
Dose rate dependency of micelle leucodye 3D gel dosimeters
NASA Astrophysics Data System (ADS)
Vandecasteele, J.; Ghysel, S.; De Deene, Y.
2010-11-01
Recently a novel 3D radiochromic gel dosimeter was introduced which uses micelles to dissolve a leucodye in a gelatin matrix. Experimental results show that this 3D micelle gel dosimeter was found to be dose rate dependent. A maximum difference in optical dose sensitivity of 70% was found for dose rates between 50 cGy min-1 and 400 cGy min-1. A novel composition of 3D radiochromic dosimeter is proposed composed of gelatin, sodium dodecyl sulphate, chloroform, trichloroacetic acid and leucomalachite green. The novel gel dosimeter formulation exhibits comparable radio-physical properties in respect to the composition previously proposed. Nevertheless, the novel formulation was found to be still dose rate dependent. A maximum difference of 33% was found for dose rates between 50 cGy min-1 and 400 cGy min-1. On the basis of these experimental results it is concluded that the leucodye micelle gel dosimeter is still unsatisfactory for clinical radiation therapy dose verifications. Some insights in the physico-chemical mechanisms were obtained and are discussed.
A new dosimeter formulation for deformable 3D dose verification
NASA Astrophysics Data System (ADS)
Høye, E. M.; Skyt, P. S.; Yates, E. S.; Muren, L. P.; Petersen, J. B. B.; Balling, P.
2015-01-01
We present the characteristics of a new silicone-based radiochromic dosimeter containing the leuco-malachite green (LMG) dye. The dose response as well as the dose-rate and photon-energy dependence of the dosimeter were characterized. To optimise the dose response, different concentrations of the chemical components were investigated. The dose response was found to decrease exponentially as a function of time after irradiation. A cylindrical dosimeter was produced and irradiated with a volumetric modulated arc therapy plan; the standard deviation between measured and calculated dose was 5% of the total dose.
Dose fractionation theorem in 3-D reconstruction (tomography)
Glaeser, R.M.
1997-02-01
It is commonly assumed that the large number of projections for single-axis tomography precludes its application to most beam-labile specimens. However, Hegerl and Hoppe have pointed out that the total dose required to achieve statistical significance for each voxel of a computed 3-D reconstruction is the same as that required to obtain a single 2-D image of that isolated voxel, at the same level of statistical significance. Thus a statistically significant 3-D image can be computed from statistically insignificant projections, as along as the total dosage that is distributed among these projections is high enough that it would have resulted in a statistically significant projection, if applied to only one image. We have tested this critical theorem by simulating the tomographic reconstruction of a realistic 3-D model created from an electron micrograph. The simulations verify the basic conclusions of high absorption, signal-dependent noise, varying specimen contrast and missing angular range. Furthermore, the simulations demonstrate that individual projections in the series of fractionated-dose images can be aligned by cross-correlation because they contain significant information derived from the summation of features from different depths in the structure. This latter information is generally not useful for structural interpretation prior to 3-D reconstruction, owing to the complexity of most specimens investigated by single-axis tomography. These results, in combination with dose estimates for imaging single voxels and measurements of radiation damage in the electron microscope, demonstrate that it is feasible to use single-axis tomography with soft X-ray microscopy of frozen-hydrated specimens.
2016-09-01
Numeracy and calculation are key skills for nurses. As nurses are directly accountable for ensuring medicines are prescribed, dispensed and administered safely, they must be able to understand and calculate drug doses. PMID:27615351
3D DIII-D Equilibrium Calculations with Magnetic Islands
NASA Astrophysics Data System (ADS)
Reiman, Allan; Monticello, Don; Lazerson, Sam
2012-10-01
We discuss 3D equilibrium calculations for the DIII-D tokamak that have been performed using the PIES code, focusing particularly on a single shot that has been studied by a number of different codes in the context of the FY 2012 FES Theory Milestone. The shot was part of an experimental campaign to study the suppression of edge localized modes (ELMs) using an externally imposed nonaxisymmetric magnetic perturbation.
Wavefront scanning method for minimum traveltime calculations in 3-D
Meng, F.; Liu, H.; Li, Y.
1994-12-31
This paper proposes an efficient way to calculate the shortest travel-time and its correspondent ray-path in three dimension, by using point secondary approximation to depict the wavefront and propagate the travel-time computation along recursively expanding and contracting cubic boxes. Due to its following advantages: (1) the computation order is O(N), where N is the total number of discrete secondary nodes; (2) the memory occupation is relatively small; (3) the algorithm is robust even for high velocity contrast; (4) the minimum travel-time and raypath are computed accurately, this 3-D wavefront scanning raytracing method promises to be real tool for 3-D seismic prestack migration, velocity analysis as well as forward waveform modeling by Maslov asymptotic ray theory.
EPID-guided 3D dose verification of lung SBRT
Aristophanous, M.; Rottmann, J.; Court, L. E.; Berbeco, R. I.
2011-01-15
Purpose: To investigate the feasibility of utilizing tumor tracks from electronic portal imaging device (EPID) images taken during treatment to verify the delivered dose. Methods: The proposed method is based on a computation of the delivered fluence by utilizing the planned fluence and the tumor motion track for each field. A phantom study was designed to assess the feasibility of the method. The CIRS dynamic thorax phantom was utilized with a realistic soft resin tumor, modeled after a real patient tumor. The dose calculated with the proposed method was compared to direct measurements taken with 15 metal oxide semiconductor field effect transistors (MOSFETs) inserted in small fissures made in the tumor model. The phantom was irradiated with the tumor static and moved with different range of motions and setup errors. EPID images were recorded throughout all deliveries and the tumor model was tracked post-treatment with in-house developed software. The planned fluence for each field was convolved with the tumor motion tracks to obtain the delivered fluence. Utilizing the delivered fluence from each field, the delivered dose was calculated. The estimated delivered dose was compared to the dose directly measured with the MOSFETs. The feasibility of the proposed method was also demonstrated on a real lung cancer patient, treated with stereotactic body radiotherapy. Results: The calculation of delivered dose with the delivered fluence method was in good agreement with the MOSFET measurements, with average differences ranging from 0.8% to 8.3% depending on the proximity of a dose gradient. For the patient treatment, the planned and delivered dose volume histograms were compared and verified the overall good coverage of the target volume. Conclusions: The delivered fluence method was applied successfully on phantom and clinical data and its accuracy was evaluated. Verifying each treatment fraction may enable correction strategies that can be applied during the course of
3D Dose Verification Using Tomotherapy CT Detector Array
Sheng Ke; Jones, Ryan; Yang Wensha; Saraiya, Siddharth; Schneider, Bernard; Chen Quan; Sobering, Geoff; Olivera, Gustavo; Read, Paul
2012-02-01
Purpose: To evaluate a three-dimensional dose verification method based on the exit dose using the onboard detector of tomotherapy. Methods and Materials: The study included 347 treatment fractions from 24 patients, including 10 prostate, 5 head and neck (HN), and 9 spinal stereotactic body radiation therapy (SBRT) cases. Detector sonograms were retrieved and back-projected to calculate entrance fluence, which was then forward-projected on the CT images to calculate the verification dose, which was compared with ion chamber and film measurement in the QA plans and with the planning dose in patient plans. Results: Root mean square (RMS) errors of 2.0%, 2.2%, and 2.0% were observed comparing the dose verification (DV) and the ion chamber measured point dose in the phantom plans for HN, prostate, and spinal SBRT patients, respectively. When cumulative dose in the entire treatment is considered, for HN patients, the error of the mean dose to the planning target volume (PTV) varied from 1.47% to 5.62% with a RMS error of 3.55%. For prostate patients, the error of the mean dose to the prostate target volume varied from -5.11% to 3.29%, with a RMS error of 2.49%. The RMS error of maximum doses to the bladder and the rectum were 2.34% (-4.17% to 2.61%) and 2.64% (-4.54% to 3.94%), respectively. For the nine spinal SBRT patients, the RMS error of the minimum dose to the PTV was 2.43% (-5.39% to 2.48%). The RMS error of maximum dose to the spinal cord was 1.05% (-2.86% to 0.89%). Conclusions: An excellent agreement was observed between the measurement and the verification dose. In the patient treatments, the agreement in doses to the majority of PTVs and organs at risk is within 5% for the cumulative treatment course doses. The dosimetric error strongly depends on the error in multileaf collimator leaf opening time with a sensitivity correlating to the gantry rotation period.
Tatsugami, Fuminari; Higaki, Toru; Fukumoto, Wataru; Kaichi, Yoko; Fujioka, Chikako; Kiguchi, Masao; Yamamoto, Hideya; Kihara, Yasuki; Awai, Kazuo
2015-06-01
To assess the possibility of reducing the radiation dose for coronary artery calcium (CAC) scoring by using adaptive iterative dose reduction 3D (AIDR 3D) on a 320-detector CT scanner. Fifty-four patients underwent routine- and low-dose CT for CAC scoring. Low-dose CT was performed at one-third of the tube current used for routine-dose CT. Routine-dose CT was reconstructed with filtered back projection (FBP) and low-dose CT was reconstructed with AIDR 3D. We compared the calculated Agatston-, volume-, and mass scores of these images. The overall percentage difference in the Agatston-, volume-, and mass scores between routine- and low-dose CT studies was 15.9, 11.6, and 12.6%, respectively. There were no significant differences in the routine- and low-dose CT studies irrespective of the scoring algorithms applied. The CAC measurements of both imaging modalities were highly correlated with respect to the Agatston- (r = 0.996), volume- (r = 0.996), and mass score (r = 0.997; p < 0.001, all); the Bland-Altman limits of agreement scores were -37.4 to 51.4, -31.2 to 36.4 and -30.3 to 40.9%, respectively, suggesting that AIDR 3D was a good alternative for FBP. The mean effective radiation dose for routine- and low-dose CT was 2.2 and 0.7 mSv, respectively. The use of AIDR 3D made it possible to reduce the radiation dose by 67% for CAC scoring without impairing the quantification of coronary calcification.
Tatsugami, Fuminari; Higaki, Toru; Fukumoto, Wataru; Kaichi, Yoko; Fujioka, Chikako; Kiguchi, Masao; Yamamoto, Hideya; Kihara, Yasuki; Awai, Kazuo
2015-06-01
To assess the possibility of reducing the radiation dose for coronary artery calcium (CAC) scoring by using adaptive iterative dose reduction 3D (AIDR 3D) on a 320-detector CT scanner. Fifty-four patients underwent routine- and low-dose CT for CAC scoring. Low-dose CT was performed at one-third of the tube current used for routine-dose CT. Routine-dose CT was reconstructed with filtered back projection (FBP) and low-dose CT was reconstructed with AIDR 3D. We compared the calculated Agatston-, volume-, and mass scores of these images. The overall percentage difference in the Agatston-, volume-, and mass scores between routine- and low-dose CT studies was 15.9, 11.6, and 12.6%, respectively. There were no significant differences in the routine- and low-dose CT studies irrespective of the scoring algorithms applied. The CAC measurements of both imaging modalities were highly correlated with respect to the Agatston- (r = 0.996), volume- (r = 0.996), and mass score (r = 0.997; p < 0.001, all); the Bland-Altman limits of agreement scores were -37.4 to 51.4, -31.2 to 36.4 and -30.3 to 40.9%, respectively, suggesting that AIDR 3D was a good alternative for FBP. The mean effective radiation dose for routine- and low-dose CT was 2.2 and 0.7 mSv, respectively. The use of AIDR 3D made it possible to reduce the radiation dose by 67% for CAC scoring without impairing the quantification of coronary calcification. PMID:25754302
1997-06-10
VENTSAR XL is an EXCEL Spreadsheet that can be used to calculate downwind doses as a result of a hypothetical atmospheric release. Both building effects and plume rise may be considered. VENTSAR XL will run using any version of Microsoft EXCEL version 4.0 or later. Macros (the programming language of EXCEL) was used to automate the calculations. The user enters a minimal amount of input and the code calculates the resulting concentrations and doses atmore » various downwind distances as specified by the user.« less
3D delivered dose assessment using a 4DCT-based motion model
Cai, Weixing; Hurwitz, Martina H.; Williams, Christopher L.; Dhou, Salam; Berbeco, Ross I.; Mishra, Pankaj E-mail: jhlewis@lroc.harvard.edu; Lewis, John H. E-mail: jhlewis@lroc.harvard.edu; Seco, Joao
2015-06-15
Purpose: The purpose of this work is to develop a clinically feasible method of calculating actual delivered dose distributions for patients who have significant respiratory motion during the course of stereotactic body radiation therapy (SBRT). Methods: A novel approach was proposed to calculate the actual delivered dose distribution for SBRT lung treatment. This approach can be specified in three steps. (1) At the treatment planning stage, a patient-specific motion model is created from planning 4DCT data. This model assumes that the displacement vector field (DVF) of any respiratory motion deformation can be described as a linear combination of some basis DVFs. (2) During the treatment procedure, 2D time-varying projection images (either kV or MV projections) are acquired, from which time-varying “fluoroscopic” 3D images of the patient are reconstructed using the motion model. The DVF of each timepoint in the time-varying reconstruction is an optimized linear combination of basis DVFs such that the 2D projection of the 3D volume at this timepoint matches the projection image. (3) 3D dose distribution is computed for each timepoint in the set of 3D reconstructed fluoroscopic images, from which the total effective 3D delivered dose is calculated by accumulating deformed dose distributions. This approach was first validated using two modified digital extended cardio-torso (XCAT) phantoms with lung tumors and different respiratory motions. The estimated doses were compared to the dose that would be calculated for routine 4DCT-based planning and to the actual delivered dose that was calculated using “ground truth” XCAT phantoms at all timepoints. The approach was also tested using one set of patient data, which demonstrated the application of our method in a clinical scenario. Results: For the first XCAT phantom that has a mostly regular breathing pattern, the errors in 95% volume dose (D95) are 0.11% and 0.83%, respectively for 3D fluoroscopic images
3D delivered dose assessment using a 4DCT-based motion model
Cai, Weixing; Hurwitz, Martina H.; Williams, Christopher L.; Dhou, Salam; Berbeco, Ross I.; Seco, Joao; Mishra, Pankaj; Lewis, John H.
2015-01-01
Purpose: The purpose of this work is to develop a clinically feasible method of calculating actual delivered dose distributions for patients who have significant respiratory motion during the course of stereotactic body radiation therapy (SBRT). Methods: A novel approach was proposed to calculate the actual delivered dose distribution for SBRT lung treatment. This approach can be specified in three steps. (1) At the treatment planning stage, a patient-specific motion model is created from planning 4DCT data. This model assumes that the displacement vector field (DVF) of any respiratory motion deformation can be described as a linear combination of some basis DVFs. (2) During the treatment procedure, 2D time-varying projection images (either kV or MV projections) are acquired, from which time-varying “fluoroscopic” 3D images of the patient are reconstructed using the motion model. The DVF of each timepoint in the time-varying reconstruction is an optimized linear combination of basis DVFs such that the 2D projection of the 3D volume at this timepoint matches the projection image. (3) 3D dose distribution is computed for each timepoint in the set of 3D reconstructed fluoroscopic images, from which the total effective 3D delivered dose is calculated by accumulating deformed dose distributions. This approach was first validated using two modified digital extended cardio-torso (XCAT) phantoms with lung tumors and different respiratory motions. The estimated doses were compared to the dose that would be calculated for routine 4DCT-based planning and to the actual delivered dose that was calculated using “ground truth” XCAT phantoms at all timepoints. The approach was also tested using one set of patient data, which demonstrated the application of our method in a clinical scenario. Results: For the first XCAT phantom that has a mostly regular breathing pattern, the errors in 95% volume dose (D95) are 0.11% and 0.83%, respectively for 3D fluoroscopic images
3-D magnetic field calculations for wiggglers using MAGNUS-3D
Pissanetzky, S.; Tompkins, P.
1988-01-01
The recent but steady trend toward increased magnetic and geometric complexity in the design of wigglers and undulators, of which tapered wigglers, hybrid structures, laced electromagnetic wigglers, magnetic cladding, twisters and magic structures are examples, has caused a need for reliable 3-D computer models and a better understanding of the behavior of magnetic systems in three dimensions. The capabilities of the MAGNUS-3D Group of Programs are ideally suited to solve this class of problems and provide insight into 3-D effects. MAGNUS-3D can solve any problem of Magnetostatics involving permanent magnets, linear or nonlinear ferromagnetic materials and electric conductors of any shape in space. The magnetic properties of permanent magnets are described by the complete nonlinear demagnetization curve as provided by the manufacturer, or, at the user's choice, by a simpler approximation involving the coercive force, the residual induction and the direction of magnetization. The ferromagnetic materials are described by a magnetization table and an accurate interpolation relation. An internal library with properties of common industrial steels is available. The conductors are independent of the mesh and are described in terms of conductor elements from an internal library.
Yeo, Unjin A; Taylor, Michael L; Supple, Jeremy R; Siva, Shankar; Kron, Tomas; Pham, Daniel; Franich, Rick D
2014-11-08
The purpose of this study is to evaluate dosimetric errors in 3D conventional plan- ning of stereotactic body radiotherapy (SBRT) by using a 4D deformable image registration (DIR)-based dose-warping and integration technique. Respiratory- correlated 4D CT image sets with 10 phases were acquired for four consecutive patients with five liver tumors. Average intensity projection (AIP) images were used to generate 3D conventional plans of SBRT. Quasi-4D path-integrated dose accumulation was performed over all 10 phases using dose-warping techniques based on DIR. This result was compared to the conventional plan in order to evalu- ate the appropriateness of 3D (static) dose calculations. In addition, we consider whether organ dose metrics derived from contours defined on the average intensity projection (AIP), or on a reference phase, provide the better approximation of the 4D values. The impact of using fewer (< 10) phases was also explored. The AIP- based 3D planning approach overestimated doses to targets by 1.4% to 8.7% (mean 4.2%) and underestimated dose to normal liver by up to 8% (mean -5.5%; range -2.3% to -8.0%), compared to the 4D methodology. The homogeneity of the dose distribution was overestimated when using conventional 3D calculations by up to 24%. OAR doses estimated by 3D planning were, on average, within 10% of the 4D calculations; however, differences of up to 100% were observed. Four-dimensional dose calculation using 3 phases gave a reasonable approximation of that calculated from the full 10 phases for all patients, which is potentially useful from a workload perspective. 4D evaluation showed that conventional 3D planning on an AIP can significantly overestimate target dose (ITV and GTV+5mm), underestimate normal liver dose, and overestimate dose homogeneity. Implementing nonadaptive quasi- 4D dose calculation can highlight the potential limitation of 3D conventional SBRT planning and the resultant misrepresentations of dose in some regions
NASA Astrophysics Data System (ADS)
Boggula, Ramesh; Lorenz, Friedlieb; Mueller, Lutz; Birkner, Mattias; Wertz, Hansjoerg; Stieler, Florian; Steil, Volker; Lohr, Frank; Wenz, Frederik
2010-10-01
We validate the dosimetric performance of COMPASS®, a novel 3D quality assurance system for verification of volumetric-modulated arc therapy (VMAT) treatment plans that can correlate the delivered dose to the patient's anatomy, taking into account the tissue inhomogeneity. The accuracy of treatment delivery was assessed by the COMPASS® for 12 VMAT plans, and the resulting assessments were evaluated using an ionization chamber and film measurements. Dose-volume relationships were evaluated by the COMPASS® for three additional treatment plans and these were used to verify the accuracy of treatment planning dose calculations. The results matched well between COMPASS® and measurements for the ionization chamber (<=3%) and film (73-99% for gamma(3%/3 mm) < 1 and 98-100% for gamma(5%/5 mm) < 1) for the phantom plans. Differences in dose-volume statistics for the average dose to the PTV were within 2.5% for three treatment plans. For the structures located in the low-dose region, a maximum difference of <9% was observed. In its current implementation, the system could measure the delivered dose with sufficient accuracy and could project the 3D dose distribution directly on the patient's anatomy. Slight deviations were found for large open fields. These could be minimized by improving the COMPASS® in-built beam model.
Evaluation of 3D Gamma index calculation implemented in two commercial dosimetry systems
NASA Astrophysics Data System (ADS)
Xing, Aitang; Arumugam, Sankar; Deshpande, Shrikant; George, Armia; Vial, Philip; Holloway, Lois; Goozee, Gary
2015-01-01
3D Gamma index is one of the metrics which have been widely used for clinical routine patient specific quality assurance for IMRT, Tomotherapy and VMAT. The algorithms for calculating the 3D Gamma index using global and local methods implemented in two software tools: PTW- VeriSoft® as a part of OCTIVIUS 4D dosimeter systems and 3DVHTM from Sun Nuclear were assessed. The Gamma index calculated by the two systems was compared with manual calculated for one data set. The Gamma pass rate calculated by the two systems was compared using 3%/3mm, 2%/2mm, 3%/2mm and 2%/3mm for two additional data sets. The Gamma indexes calculated by the two systems were accurate, but Gamma pass rates calculated by the two software tools for same data set with the same dose threshold were different due to the different interpolation of raw dose data by the two systems and different implementation of Gamma index calculation and other modules in the two software tools. The mean difference was -1.3%±3.38 (1SD) with a maximum difference of 11.7%.
Development of a patient-specific 3D dose evaluation program for QA in radiation therapy
NASA Astrophysics Data System (ADS)
Lee, Suk; Chang, Kyung Hwan; Cao, Yuan Jie; Shim, Jang Bo; Yang, Dae Sik; Park, Young Je; Yoon, Won Sup; Kim, Chul Yong
2015-03-01
We present preliminary results for a 3-dimensional dose evaluation software system ( P DRESS, patient-specific 3-dimensional dose real evaluation system). Scanned computed tomography (CT) images obtained by using dosimetry were transferred to the radiation treatment planning system (ECLIPSE, VARIAN, Palo Alto, CA) where the intensity modulated radiation therapy (IMRT) nasopharynx plan was designed. We used a 10 MV photon beam (CLiX, VARIAN, Palo Alto, CA) to deliver the nasopharynx treatment plan. After irradiation, the TENOMAG dosimeter was scanned using a VISTA ™ scanner. The scanned data were reconstructed using VistaRecon software to obtain a 3D dose distribution of the optical density. An optical-CT scanner was used to readout the dose distribution in the gel dosimeter. Moreover, we developed the P DRESS by using Flatform, which were developed by our group, to display the 3D dose distribution by loading the DICOM RT data which are exported from the radiotherapy treatment plan (RTP) and the optical-CT reconstructed VFF file, into the independent P DRESS with an ioniz ation chamber and EBT film was used to compare the dose distribution calculated from the RTP with that measured by using a gel dosimeter. The agreement between the normalized EBT, the gel dosimeter and RTP data was evaluated using both qualitative and quantitative methods, such as the isodose distribution, dose difference, point value, and profile. The profiles showed good agreement between the RTP data and the gel dosimeter data, and the precision of the dose distribution was within ±3%. The results from this study showed significantly discrepancies between the dose distribution calculated from the treatment plan and the dose distribution measured by a TENOMAG gel and by scanning with an optical CT scanner. The 3D dose evaluation software system ( P DRESS, patient specific dose real evaluation system), which were developed in this study evaluates the accuracies of the three-dimensional dose
Eigenvalue Contributon Estimator for Sensitivity Calculations with TSUNAMI-3D
Rearden, Bradley T; Williams, Mark L
2007-01-01
Since the release of the Tools for Sensitivity and Uncertainty Analysis Methodology Implementation (TSUNAMI) codes in SCALE [1], the use of sensitivity and uncertainty analysis techniques for criticality safety applications has greatly increased within the user community. In general, sensitivity and uncertainty analysis is transitioning from a technique used only by specialists to a practical tool in routine use. With the desire to use the tool more routinely comes the need to improve the solution methodology to reduce the input and computational burden on the user. This paper reviews the current solution methodology of the Monte Carlo eigenvalue sensitivity analysis sequence TSUNAMI-3D, describes an alternative approach, and presents results from both methodologies.
SU-E-T-535: Preliminary 2D and 3D Gamma Calculation Comparison Using PRESAGE
Lafratta, R; Yang, J; Sahoo, N; Tucker, S; Followill, D; Ibbott, G
2014-06-01
Purpose: To compare gamma calculations from 2D and 3D dosimetry measurements for phantom quality assurance. Methods: An IROC Houston (RPC) head and neck phantom was irradiated with a 9 beam IMRT plan using two inserts: a TLD and film insert and a PRESAGE insert. Both inserts were irradiated 3 times. The film and PRESAGE doses were scaled to the TLD dose and 2D gamma calculations were made in the axial and sagittal planes bisecting the primary target. 3D gamma measurements were taken within the PRESAGE dosimeter volume. Gamma constraints of 3%/3mm distance to agreement (DTA), 5%/3mm DTA and 7%/4mm DTA were used in the study. The 3 irradiations for each insert were averaged together for comparison. Results: Film measurements for the 2D gamma showed 85% pixels passing at 3%/3mm in both planes. The 5%/3 mm constraint had 93% and 90% passing in the two planes. The 7%/4mm restraint resulted in 99% passing in both planes. The PRESAGE 2D gamma passed 66% and 61% of pixels in the both planes at 3%/3mm. At 5%/3mm 86% and 82% passed. For 7%/4mm, 94% of pixels passed in both planes. The 3D gamma resulted in a pass rate of 90% at 3%/3mm, 95% at 5%/3mm, and 99% at 7%/4mm. Conclusion: 2D gamma pass rates using film showed a higher pass rate than PRESAGE using the same criteria in the same planes. This may be due to poor 3D registration with the treatment plan compared to the 2D film registration system. The 3D gamma results had a higher pass rate (> 90% pass rate) possibly because it sampled many more pixels in noncritical volumes thus diluting the percent of pixels passing. 3D restraints should be more restrictive to be comparable to 2D results. Funding from NIH grant 5R01CA100835.
3D dose and TCP distribution for radionuclide therapy in nuclear medicine
Valente, M.; Malano, F.; Perez, P.
2010-08-04
A common feature to any radiant therapy is that lesion and health tissue dosimetry provides relevant information for treatment optimization along with dose-efficacy and dose-complication correlation studies. Nowadays, different radionuclide therapies are commonly available, assessing both systemic and loco-regional approach and using different alfa-, beta-and gamma-emitting isotopes and binding molecules. It is well established, that specific dosimetric approaches become necessary according to each therapy modality. Sometimes, observed activity distribution can be satisfactory represented by simple geometrical models. However, Monte Carlo techniques are capable of better approaches, therefore becoming sometimes the only way to get dosimetric data since the patient-specific situation can not be adequately represented by conventional dosimetry techniques. Therefore, due to strong limitations of traditional and standard methods, this work concentrates on the development of a dedicated and novel calculation system in order to assess the dose distribution within the irradiated patient. However, physical dose may not be enough information in order to establish real deterministic biological/metabolic effects; therefore complementary radiobiological models have been suitably introduced with the aim of performing realistic 3D dose as well as corresponding Tumor Control Probability distribution calculation.
NASA Astrophysics Data System (ADS)
Svalkvist, Angelica; Hansson, Jonny; Bâth, Magnus
2014-03-01
Three-dimensional (3D) imaging with interventional fluoroscopy systems is today a common examination. The examination includes acquisition of two-dimensional projection images, used to reconstruct section images of the patient. The aim of the present study was to investigate the difference in resulting effective dose obtained using different levels of complexity in calculations of effective doses from these examinations. In the study the Siemens Artis Zeego interventional fluoroscopy system (Siemens Medical Solutions, Erlangen, Germany) was used. Images of anthropomorphic chest and pelvis phantoms were acquired. The exposure values obtained were used to calculate the resulting effective doses from the examinations, using the computer software PCXMC (STUK, Helsinki, Finland). The dose calculations were performed using three different methods: 1. using individual exposure values for each projection image, 2. using the mean tube voltage and the total DAP value, evenly distributed over the projection images, and 3. using the mean kV and the total DAP value, evenly distributed over smaller selection of projection images. The results revealed that the difference in resulting effective dose between the first two methods was smaller than 5%. When only a selection of projection images were used in the dose calculations the difference increased to over 10%. Given the uncertainties associated with the effective dose concept, the results indicate that dose calculations based on average exposure values distributed over a smaller selection of projection angles can provide reasonably accurate estimations of the radiation doses from 3D imaging using interventional fluoroscopy systems.
Flynn, A A; Pedley, R B; Green, A J; Boxer, G M; Boden, R; Begent, R H
2001-10-01
The biological effect of radioimmunotherapy (RIT) is most commonly assessed in terms of the absorbed radiation dose. In tumor, conventional dosimetry methods assume a uniform radionuclide and calculate a mean dose throughout the tumor. However, the vasculature of solid tumors tends to be highly irregular and the systemic delivery of antibodies is therefore heterogeneous. Tumor-specific antibodies preferentially localize in the viable, radiosensitive parts of the tumor whereas non-specific antibodies can penetrate into the necrosis where the dose is wasted. As a result, the observed biological effect can be very different to the predicted effect from conventional dose estimates. The purpose of this study is to assess the potential for optimizing the biological effect of RIT by matching the dose-distribution with tumor structure through the selection of appropriate antibodies and radionuclides. Storage phosphor plate technology was used to acquire images of the antibody distribution in serial tumor sections. Images of the distributions of a trivalent (TFM), bivalent (A5B7-IgG), monovalent (MFE-23) and a non-specific antibody (MOPC) were obtained. These images were registered with corresponding images showing tumor morphology. Serial images were reconstructed to form 3D maps of the antibody distribution and tumor structure. Convolution of the image of antibody distribution with beta dose point kernals generated dose-rate distributions for 14C, 131I and 90Y. These were statistically compared with the tumor structure. The highest correlation was obtained for the multivalent antibodies combined with 131I, due to specific retention in viable areas of tumor coupled with the fact that much of the dose was deposted locally. With decreasing avidity the correlation also decreased and with the non-specific antibody this correlation was negative, indicating higher concentrations in the necrotic regions. In conclusion, the dose distribution can be optimized in tumor by selecting
A novel time dependent gamma evaluation function for dynamic 2D and 3D dose distributions
NASA Astrophysics Data System (ADS)
Podesta, Mark; CGG Persoon, Lucas; Verhaegen, Frank
2014-10-01
Modern external beam radiotherapy requires detailed verification and quality assurance so that confidence can be placed on both the delivery of a single treatment fraction and on the consistency of delivery throughout the treatment course. To verify dose distributions, a comparison between prediction and measurement must be made. Comparisons between two dose distributions are commonly performed using a Gamma evaluation which is a calculation of two quantities on a pixel by pixel basis; the dose difference, and the distance to agreement. By providing acceptance criteria (e.g. 3%, 3 mm), the function will find the most appropriate match within its two degrees of freedom. For complex dynamic treatments such as IMRT or VMAT it is important to verify the dose delivery in a time dependent manner and so a gamma evaluation that includes a degree of freedom in the time domain via a third parameter, time to agreement, is presented here. A C++ (mex) based gamma function was created that could be run on either CPU and GPU computing platforms that would allow a degree of freedom in the time domain. Simple test cases were created in both 2D and 3D comprising of simple geometrical shapes with well-defined boundaries varying over time. Changes of varying magnitude in either space or time were introduced and repeated gamma analyses were performed varying the criteria. A clinical VMAT case was also included, artificial air bubbles of varying size were introduced to a patient geometry, along with shifts of varying magnitude in treatment time. For all test cases where errors in distance, dose or time were introduced, the time dependent gamma evaluation could accurately highlight the errors. The time dependent gamma function presented here allows time to be included as a degree of freedom in gamma evaluations. The function allows for 2D and 3D data sets which are varying over time to be compared using appropriate criteria without penalising minor offsets of subsequent radiation
A novel time dependent gamma evaluation function for dynamic 2D and 3D dose distributions.
Podesta, Mark; Persoon, Lucas C G G; Verhaegen, Frank
2014-10-21
Modern external beam radiotherapy requires detailed verification and quality assurance so that confidence can be placed on both the delivery of a single treatment fraction and on the consistency of delivery throughout the treatment course. To verify dose distributions, a comparison between prediction and measurement must be made. Comparisons between two dose distributions are commonly performed using a Gamma evaluation which is a calculation of two quantities on a pixel by pixel basis; the dose difference, and the distance to agreement. By providing acceptance criteria (e.g. 3%, 3 mm), the function will find the most appropriate match within its two degrees of freedom. For complex dynamic treatments such as IMRT or VMAT it is important to verify the dose delivery in a time dependent manner and so a gamma evaluation that includes a degree of freedom in the time domain via a third parameter, time to agreement, is presented here. A C++ (mex) based gamma function was created that could be run on either CPU and GPU computing platforms that would allow a degree of freedom in the time domain. Simple test cases were created in both 2D and 3D comprising of simple geometrical shapes with well-defined boundaries varying over time. Changes of varying magnitude in either space or time were introduced and repeated gamma analyses were performed varying the criteria. A clinical VMAT case was also included, artificial air bubbles of varying size were introduced to a patient geometry, along with shifts of varying magnitude in treatment time. For all test cases where errors in distance, dose or time were introduced, the time dependent gamma evaluation could accurately highlight the errors.The time dependent gamma function presented here allows time to be included as a degree of freedom in gamma evaluations. The function allows for 2D and 3D data sets which are varying over time to be compared using appropriate criteria without penalising minor offsets of subsequent radiation fields
Calculating Least Risk Paths in 3d Indoor Space
NASA Astrophysics Data System (ADS)
Vanclooster, A.; De Maeyer, Ph.; Fack, V.; Van de Weghe, N.
2013-08-01
Over the last couple of years, research on indoor environments has gained a fresh impetus; more specifically applications that support navigation and wayfinding have become one of the booming industries. Indoor navigation research currently covers the technological aspect of indoor positioning and the modelling of indoor space. The algorithmic development to support navigation has so far been left mostly untouched, as most applications mainly rely on adapting Dijkstra's shortest path algorithm to an indoor network. However, alternative algorithms for outdoor navigation have been proposed adding a more cognitive notion to the calculated paths and as such adhering to the natural wayfinding behaviour (e.g. simplest paths, least risk paths). These algorithms are currently restricted to outdoor applications. The need for indoor cognitive algorithms is highlighted by a more challenged navigation and orientation due to the specific indoor structure (e.g. fragmentation, less visibility, confined areas…). As such, the clarity and easiness of route instructions is of paramount importance when distributing indoor routes. A shortest or fastest path indoors not necessarily aligns with the cognitive mapping of the building. Therefore, the aim of this research is to extend those richer cognitive algorithms to three-dimensional indoor environments. More specifically for this paper, we will focus on the application of the least risk path algorithm of Grum (2005) to an indoor space. The algorithm as proposed by Grum (2005) is duplicated and tested in a complex multi-storey building. The results of several least risk path calculations are compared to the shortest paths in indoor environments in terms of total length, improvement in route description complexity and number of turns. Several scenarios are tested in this comparison: paths covering a single floor, paths crossing several building wings and/or floors. Adjustments to the algorithm are proposed to be more aligned to the
Shen, Hesong; Dai, Guochao; Luo, Mingyue; Duan, Chaijie; Cai, Wenli; Liang, Dan; Wang, Xinhua; Zhu, Dongyun; Li, Wenru; Qiu, Jianping
2015-01-01
Purpose To investigate image quality and radiation dose of CT coronary angiography (CTCA) scanned using automatic tube current modulation (ATCM) and reconstructed by strong adaptive iterative dose reduction three-dimensional (AIDR3D). Methods Eighty-four consecutive CTCA patients were collected for the study. All patients were scanned using ATCM and reconstructed with strong AIDR3D, standard AIDR3D and filtered back-projection (FBP) respectively. Two radiologists who were blinded to the patients' clinical data and reconstruction methods evaluated image quality. Quantitative image quality evaluation included image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). To evaluate image quality qualitatively, coronary artery is classified into 15 segments based on the modified guidelines of the American Heart Association. Qualitative image quality was evaluated using a 4-point scale. Radiation dose was calculated based on dose-length product. Results Compared with standard AIDR3D, strong AIDR3D had lower image noise, higher SNR and CNR, their differences were all statistically significant (P<0.05); compared with FBP, strong AIDR3D decreased image noise by 46.1%, increased SNR by 84.7%, and improved CNR by 82.2%, their differences were all statistically significant (P<0.05 or 0.001). Segments with diagnostic image quality for strong AIDR3D were 336 (100.0%), 486 (96.4%), and 394 (93.8%) in proximal, middle, and distal part respectively; whereas those for standard AIDR3D were 332 (98.8%), 472 (93.7%), 378 (90.0%), respectively; those for FBP were 217 (64.6%), 173 (34.3%), 114 (27.1%), respectively; total segments with diagnostic image quality in strong AIDR3D (1216, 96.5%) were higher than those of standard AIDR3D (1182, 93.8%) and FBP (504, 40.0%); the differences between strong AIDR3D and standard AIDR3D, strong AIDR3D and FBP were all statistically significant (P<0.05 or 0.001). The mean effective radiation dose was (2.55±1.21) mSv. Conclusion
Calculation of the 3D density model of the Earth
NASA Astrophysics Data System (ADS)
Piskarev, A.; Butsenko, V.; Poselov, V.; Savin, V.
2009-04-01
The study of the Earth's crust is a part of investigation aimed at extension of the Russian Federation continental shelf in the Sea of Okhotsk Gathered data allow to consider the Sea of Okhotsk' area located outside the exclusive economic zone of the Russian Federation as the natural continuation of Russian territory. The Sea of Okhotsk is an Epi-Mesozoic platform with Pre-Cenozoic heterogeneous folded basement of polycyclic development and sediment cover mainly composed of Paleocene - Neocene - Quaternary deposits. Results of processing and complex interpretation of seismic, gravity, and aeromagnetic data along profile 2-DV-M, as well as analysis of available geological and geophysical information on the Sea of Okhotsk region, allowed to calculate of the Earth crust model. 4 layers stand out (bottom-up) in structure of the Earth crust: granulite-basic (density 2.90 g/cm3), granite-gneiss (limits of density 2.60-2.76 g/cm3), volcanogenic-sedimentary (2.45 g/cm3) and sedimentary (density 2.10 g/cm3). The last one is absent on the continent; it is observed only on the water area. Density of the upper mantle is taken as 3.30 g/cm3. The observed gravity anomalies are mostly related to the surface relief of the above mentioned layers or to the density variations of the granite-metamorphic basement. So outlining of the basement blocks of different constitution preceded to the modeling. This operation is executed after Double Fourier Spectrum analysis of the gravity and magnetic anomalies and following compilation of the synthetic anomaly maps, related to the basement density and magnetic heterogeneity. According to bathymetry data, the Sea of Okhotsk can be subdivided at three mega-blocks. Taking in consideration that central Sea of Okhotsk area is aseismatic, i.e. isostatic compensated, it is obvious that Earth crust structure of these three blocks is different. The South-Okhotsk depression is characteristics by 3200-3300 m of sea depths. Moho surface in this area is at
Axisymmetric and 3D calculations of melt flow during VCz growth
NASA Astrophysics Data System (ADS)
Bänsch, E.; Davis, D.; Langmach, H.; Miller, W.; Rehse, U.; Reinhardt, G.; Uhle, M.
2004-05-01
Axisymmetric and 3D calculations of melt flow have been performed for a configuration used at the vapour-pressure-controlled Czochalski growth of GaAs single crystals. Thermal boundary conditions were adapted from a global simulation of the temperature field. The axisymmetric calculations with the code NAVIER confirmed the ones previously perfomed with FIDAP TM. The 3D calculations showed that the flow exhibits an asymmetric transient behaviour beyond a certain critical Reynolds number.
Evaluation of low-dose limits in 3D-2D rigid registration for surgical guidance
NASA Astrophysics Data System (ADS)
Uneri, A.; Wang, A. S.; Otake, Y.; Kleinszig, G.; Vogt, S.; Khanna, A. J.; Gallia, G. L.; Gokaslan, Z. L.; Siewerdsen, J. H.
2014-09-01
An algorithm for intensity-based 3D-2D registration of CT and C-arm fluoroscopy is evaluated for use in surgical guidance, specifically considering the low-dose limits of the fluoroscopic x-ray projections. The registration method is based on a framework using the covariance matrix adaptation evolution strategy (CMA-ES) to identify the 3D patient pose that maximizes the gradient information similarity metric. Registration performance was evaluated in an anthropomorphic head phantom emulating intracranial neurosurgery, using target registration error (TRE) to characterize accuracy and robustness in terms of 95% confidence upper bound in comparison to that of an infrared surgical tracking system. Three clinical scenarios were considered: (1) single-view image + guidance, wherein a single x-ray projection is used for visualization and 3D-2D guidance; (2) dual-view image + guidance, wherein one projection is acquired for visualization, combined with a second (lower-dose) projection acquired at a different C-arm angle for 3D-2D guidance; and (3) dual-view guidance, wherein both projections are acquired at low dose for the purpose of 3D-2D guidance alone (not visualization). In each case, registration accuracy was evaluated as a function of the entrance surface dose associated with the projection view(s). Results indicate that images acquired at a dose as low as 4 μGy (approximately one-tenth the dose of a typical fluoroscopic frame) were sufficient to provide TRE comparable or superior to that of conventional surgical tracking, allowing 3D-2D guidance at a level of dose that is at most 10% greater than conventional fluoroscopy (scenario #2) and potentially reducing the dose to approximately 20% of the level in a conventional fluoroscopically guided procedure (scenario #3).
NASA Astrophysics Data System (ADS)
Wang, Z.; Thomas, A.; Newton, J.; Ibbott, G.; Deasy, J.; Oldham, M.
2010-11-01
Achieving adequate verification and quality-assurance (QA) for radiosurgery treatment of trigeminal-neuralgia (TGN) is particularly challenging because of the combination of very small fields, very high doses, and complex irradiation geometries (multiple gantry and couch combinations). TGN treatments have extreme requirements for dosimetry tools and QA techniques, to ensure adequate verification. In this work we evaluate the potential of Presage/Optical-CT dosimetry system as a tool for the verification of TGN distributions in high-resolution and in 3D. A TGN treatment was planned and delivered to a Presage 3D dosimeter positioned inside the Radiological-Physics-Center (RPC) head and neck IMRT credentialing phantom. A 6-arc treatment plan was created using the iPlan system, and a maximum dose of 80Gy was delivered with a Varian Trilogy machine. The delivered dose to Presage was determined by optical-CT scanning using the Duke Large field-of-view Optical-CT Scanner (DLOS) in 3D, with isotropic resolution of 0.7mm3. DLOS scanning and reconstruction took about 20minutes. 3D dose comparisons were made with the planning system. Good agreement was observed between the planned and measured 3D dose distributions, and this work provides strong support for the viability of Presage/Optical-CT as a highly useful new approach for verification of this complex technique.
SU-E-T-422: Correlation Between 2D Passing Rates and 3D Dose Differences for Pretreatment VMAT QA
Jin, X; Xie, C
2014-06-01
Purpose: Volumetric modulated arc therapy (VMAT) quality assurance (QA) is typically using QA methods and action levels taken from fixedbeam intensity-modulated radiotherapy (IMRT) QA methods. However, recent studies demonstrated that there is no correlation between the percent gamma passing rate (%GP) and the magnitude of dose discrepancy between the planned dose and the actual delivered dose for IMRT. The purpose of this study is to investigate whether %GP is correlated with clinical dosimetric difference for VMAT. Methods: Twenty nasopharyngeal cancer (NPC) patients treated with dual-arc simultaneous integrated boost VMAT and 20 esophageal cancer patients treated with one-arc VMAT were enrolled in this study. Pretreatment VMAT QA was performed by a 3D diode array ArcCheck. Acceptance criteria of 2%/2mm, 3%/3mm, and 4%/4mm were applied for 2D %GP. Dose values below 10% of the per-measured normalization maximum dose were ignored.Mean DVH values obtained from 3DVH software and TPS were calculated and percentage dose differences were calculated. Statistical correlation between %GP and percent dose difference was studied by using Pearson correlation. Results: The %GP for criteria 2%/2mm, 3%/3mm, and 4%/4mm were 82.33±4.45, 93.47±2.31, 97.13±2.41, respectively. Dose differences calculated from 3DVH and TPS for beam isocenter, mean dose of PTV, maximum dose of PTV, D2 of PTV and D98 of PTV were -1.04±3.24, -0.74±1.71, 2.92±3.62, 0.89±3.29, -1.46±1.97, respectively. No correction were found between %GP and dose differences. Conclusion: There are weak correlations between the 2D %GP and dose differences calculated from 3DVH. The %GP acceptance criteria of 3%/3mm usually applied for pretreatment QA of IMRT and VMAT is not indicating strong clinical correlation with 3D dose difference. 3D dose reconstructions on patient anatomy may be necessary for physicist to predict the accuracy of delivered dose for VMAT QA.
Dose calculation for electron therapy
NASA Astrophysics Data System (ADS)
Gebreamlak, Wondesen T.
The dose delivered by electron beams has a complex dependence on the shape of the field; any field shaping shields, design of collimator systems, and energy of the beam. This complicated dependence is due to multiple scattering of the electron beam as the beam travels from the accelerator head to the patient. The dosimetry of only regular field shapes (circular, square, or rectangular) is well developed. However, most tumors have irregular shapes and their dosimetry is calculated by direct measurement. This is laborious and time consuming. In addition, error can be introduced during measurements. The lateral build up ratio method (LBR), which is based on the Fermi-Eyges multiple scattering theory, calculates the dosimetry of irregular electron beam shapes. The accuracy of this method depends on the function sigma r(r,E) (the mean square radial displacement of the electron beam in the medium) used in the calculation. This research focuses on improving the accuracy of electron dose calculations using lateral build up ratio method by investigating the properties of sigmar(r,E). The percentage depth dose curves of different circular cutouts were measured using four electron beam energies (6, 9, 12, and 15 MeV), four electron applicator sizes (6x6, 10x10, 14x14, and 20x20 cm), three source-surface distance values (100, 105, 110 cm). The measured percentage depth dose curves were normalized at a depth of 0.05 cm. Using the normalized depth dose, the lateral build up ratio curves were determined. Using the cutout radius and the lateral build up ratio values, sigmar(z,E) were determined. It is shown that the sigma value increases linearly with cutout size until the cutout radius reaches the equilibrium range of the electron beam. The sigma value of an arbitrary circular cutout was determined from the interpolation of sigma versus cutout curve. The corresponding LBR value of the circular cutout was determined using its radius and sigma values. The depth dose distribution of
Wall-touching kink mode calculations with the M3D code
Breslau, J. A. Bhattacharjee, A.
2015-06-15
This paper seeks to address a controversy regarding the applicability of the 3D nonlinear extended MHD code M3D [W. Park et al., Phys. Plasmas 6, 1796 (1999)] and similar codes to calculations of the electromagnetic interaction of a disrupting tokamak plasma with the surrounding vessel structures. M3D is applied to a simple test problem involving an external kink mode in an ideal cylindrical plasma, used also by the Disruption Simulation Code (DSC) as a model case for illustrating the nature of transient vessel currents during a major disruption. While comparison of the results with those of the DSC is complicated by effects arising from the higher dimensionality and complexity of M3D, we verify that M3D is capable of reproducing both the correct saturation behavior of the free boundary kink and the “Hiro” currents arising when the kink interacts with a conducting tile surface interior to the ideal wall.
A Cross-Benchmarking and Validation Initiative for Tokamak 3D Equilibrium Calculations
NASA Astrophysics Data System (ADS)
Reiman, A.; Turnbull, A.; Evans, T.; Ferraro, N.; Lazarus, E.; Breslau, J.; Cerfon, A.; Chang, C. S.; Hager, R.; King, J.; Lanctot, M.; Lazerson, S.; Liu, Y.; McFadden, G.; Monticello, D.; Nazikian, R.; Park, J. K.; Sovinec, C.; Suzuki, Y.; Zhu, P.
2014-10-01
We are pursuing a cross-benchmarking and validation initiative for tokamak 3D equilibrium calculations, with 11 codes participating: the linearized tokamak equilibrium codes IPEC and MARS-F, the time-dependent extended MHD codes M3D-C1, M3D, and NIMROD, the gyrokinetic code XGC, as well as the stellarator codes VMEC, NSTAB, PIES, HINT and SPEC. Dedicated experiments for the purpose of generating data for validation have been done on the DIII-D tokamak. The data will allow us to do validation simultaneously with cross-benchmarking. Initial cross-benchmarking calculations are finding a disagreement between stellarator and tokamak 3D equilibrium codes. Work supported in part by U.S. DOE under Contracts DE-ACO2-09CH11466, DE-FC02-04E854698, DE-FG02-95E854309 and DE-AC05-000R22725.
Continuous-energy eigenvalue sensitivity coefficient calculations in TSUNAMI-3D
Perfetti, C. M.; Rearden, B. T.
2013-07-01
Two methods for calculating eigenvalue sensitivity coefficients in continuous-energy Monte Carlo applications were implemented in the KENO code within the SCALE code package. The methods were used to calculate sensitivity coefficients for several test problems and produced sensitivity coefficients that agreed well with both reference sensitivities and multigroup TSUNAMI-3D sensitivity coefficients. The newly developed CLUTCH method was observed to produce sensitivity coefficients with high figures of merit and a low memory footprint, and both continuous-energy sensitivity methods met or exceeded the accuracy of the multigroup TSUNAMI-3D calculations. (authors)
Asuni, G; Beek, T van; Van Utyven, E; McCowan, P; McCurdy, B.M.C.
2014-08-15
Radical treatment techniques such as stereotactic body radiation therapy (SBRT) are becoming popular and they involve delivery of large doses in fewer fractions. Due to this feature of SBRT, a high-resolution, pre-treatment dose verification method that makes use of a 3D patient representation would be appropriate. Such a technique will provide additional information about dose delivered to the target volume(s) and organs-at-risk (OARs) in the patient volume compared to 2D verification methods. In this work, we investigate an electronic portal imaging device (EPID) based pre-treatment QA method which provides an accurate reconstruction of the 3D-dose distribution in the patient model. Customized patient plans are delivered ‘in air’ and the portal images are collected using the EPID in cine mode. The images are then analysed to determine an estimate of the incident energy fluence. This is then passed to a collapsed-cone convolution dose algorithm which reconstructs a 3D patient dose estimate on the CT imaging dataset. To date, the method has been applied to 5 SBRT patient plans. Reconstructed doses were compared to those calculated by the TPS. Reconstructed mean doses were mostly within 3% of those in the TPS. DVHs of target volumes and OARs compared well. The Chi pass rates using 3%/3mm in the high dose region are greater than 97% in all cases. These initial results demonstrate clinical feasibility and utility of a robust, efficient, effective and convenient pre-treatment QA method using EPID. Research sponsored in part by Varian Medical Systems.
Verification of Internal Dose Calculations.
NASA Astrophysics Data System (ADS)
Aissi, Abdelmadjid
The MIRD internal dose calculations have been in use for more than 15 years, but their accuracy has always been questionable. There have been attempts to verify these calculations; however, these attempts had various shortcomings which kept the question of verification of the MIRD data still unanswered. The purpose of this research was to develop techniques and methods to verify the MIRD calculations in a more systematic and scientific manner. The research consisted of improving a volumetric dosimeter, developing molding techniques, and adapting the Monte Carlo computer code ALGAM to the experimental conditions and vice versa. The organic dosimetric system contained TLD-100 powder and could be shaped to represent human organs. The dosimeter possessed excellent characteristics for the measurement of internal absorbed doses, even in the case of the lungs. The molding techniques are inexpensive and were used in the fabrication of dosimetric and radioactive source organs. The adaptation of the computer program provided useful theoretical data with which the experimental measurements were compared. The experimental data and the theoretical calculations were compared for 6 source organ-7 target organ configurations. The results of the comparison indicated the existence of an agreement between measured and calculated absorbed doses, when taking into consideration the average uncertainty (16%) of the measurements, and the average coefficient of variation (10%) of the Monte Carlo calculations. However, analysis of the data gave also an indication that the Monte Carlo method might overestimate the internal absorbed doses. Even if the overestimate exists, at least it could be said that the use of the MIRD method in internal dosimetry was shown to lead to no unnecessary exposure to radiation that could be caused by underestimating the absorbed dose. The experimental and the theoretical data were also used to test the validity of the Reciprocity Theorem for heterogeneous
Adamson, Justus; Newton, Joseph; Yang Yun; Steffey, Beverly; Cai, Jing; Adamovics, John; Oldham, Mark; Chino, Junzo; Craciunescu, Oana
2012-07-15
Purpose: To determine the geometric and dose attenuation characteristics of a new commercially available CT-compatible LDR tandem and ovoid (T and O) applicator using Monte Carlo calculation and 3D dosimetry. Methods: For geometric characterization, we quantified physical dimensions and investigated a systematic difference found to exist between nominal ovoid angle and the angle at which the afterloading buckets fall within the ovoid. For dosimetric characterization, we determined source attenuation through asymmetric gold shielding in the buckets using Monte Carlo simulations and 3D dosimetry. Monte Carlo code MCNP5 was used to simulate 1.5 Multiplication-Sign 10{sup 9} photon histories from a {sup 137}Cs source placed in the bucket to achieve statistical uncertainty of 1% at a 6 cm distance. For 3D dosimetry, the distribution about an unshielded source was first measured to evaluate the system for {sup 137}Cs, after which the distribution was measured about sources placed in each bucket. Cylindrical PRESAGE{sup Registered-Sign} dosimeters (9.5 cm diameter, 9.2 cm height) with a central channel bored for source placement were supplied by Heuris Inc. The dosimeters were scanned with the Duke Large field of view Optical CT-Scanner before and after delivering a nominal dose at 1 cm of 5-8 Gy. During irradiation the dosimeter was placed in a water phantom to provide backscatter. Optical CT scan time lasted 15 min during which 720 projections were acquired at 0.5 Degree-Sign increments, and a 3D distribution was reconstructed with a (0.05 cm){sup 3} isotropic voxel size. The distributions about the buckets were used to calculate a 3D distribution of transmission rate through the bucket, which was applied to a clinical CT-based T and O implant plan. Results: The systematic difference in bucket angle relative to the nominal ovoid angle (105 Degree-Sign ) was 3.1 Degree-Sign -4.7 Degree-Sign . A systematic difference in bucket angle of 1 Degree-Sign , 5 Degree-Sign , and
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.
NASA Astrophysics Data System (ADS)
Wahle, Andreas; Lopez, John J.; Pennington, Edward C.; Meeks, Sanford L.; Braddy, Kathleen C.; Fox, James M.; Brennan, Theresa M. H.; Buatti, John M.; Rossen, James D.; Sonka, Milan
2003-05-01
Intravascular brachytherapy has shown to reduce re-occurrence of in-stent restenosis in coronary arteries. For beta radiation, application time is determined from source activity and the angiographically estimated vessel diameter. Conventionally used dosing models assume a straight vessel with the catheter centered and a constant-diameter circular cross section. Aim of this study was to compare the actual dose delivered during in-vivo intravascular brachytherapy with the target range determined from the patient's prescribed dose. Furthermore, differences in dose distribution between a simplified tubular model (STM) and a geometrically correct 3-D model (GCM) obtained from fusion between biplane angiography and intravascular ultrasound were quantified. The tissue enclosed by the segmented lumen/plaque and media/adventitia borders was simulated using a structured finite-element mesh. The beta-radiation sources were modeled as 3-D objects in their angiographically determined locations. The accumulated dose was estimated using a fixed distance function based on the patient-specific radiation parameters. For visualization, the data was converted to VRML with the accumulated doses represented by color encoding. The statistical comparison between STM and GCM models in 8 patients showed that the STM significantly underestimates the dose delivered and its variability. The analysis revealed substantial deviations from the target dose range in curved vessels.
Eliminating the dose-rate effect in a radiochromic silicone-based 3D dosimeter
NASA Astrophysics Data System (ADS)
Høye, E. M.; Balling, P.; Yates, E. S.; Muren, L. P.; Petersen, J. B. B.; Skyt, P. S.
2015-07-01
Comprehensive dose verification, such as 3D dosimetry, may be required for safe introduction and use of advanced treatment modalities in radiotherapy. A radiochromic silicone-based 3D dosimetry system has recently been suggested, though its clinical use has so far been limited by a considerable dose-rate dependency of the dose response. In this study we have investigated the dose-rate dependency with respect to the chemical composition of the dosimeter. We found that this dependency was reduced with increasing dye concentration, and the dose response was observed to be identical for dosimeters irradiated with 2 and 6 Gy min-1 at concentrations of 0.26% (w/w) dye and 1% (w/w) dye solvent. Furthermore, for the optimized dosimeter formulation, no dose-rate effect was observed due to the attenuation of the beam fluence with depth. However, the temporal stability of the dose response decreased with dye concentration; the response was reduced by (62 ± 1)% within approximately 20 h upon irradiation, at the optimal chemical composition and storage at room temperature. In conclusion, this study presents a chemical composition for a dose-rate independent silicone dosimeter which has considerably improved the clinical applicability of such dosimeters, but at the cost of a decreased stability.
Modeling late rectal toxicities based on a parameterized representation of the 3D dose distribution
NASA Astrophysics Data System (ADS)
Buettner, Florian; Gulliford, Sarah L.; Webb, Steve; Partridge, Mike
2011-04-01
Many models exist for predicting toxicities based on dose-volume histograms (DVHs) or dose-surface histograms (DSHs). This approach has several drawbacks as firstly the reduction of the dose distribution to a histogram results in the loss of spatial information and secondly the bins of the histograms are highly correlated with each other. Furthermore, some of the complex nonlinear models proposed in the past lack a direct physical interpretation and the ability to predict probabilities rather than binary outcomes. We propose a parameterized representation of the 3D distribution of the dose to the rectal wall which explicitly includes geometrical information in the form of the eccentricity of the dose distribution as well as its lateral and longitudinal extent. We use a nonlinear kernel-based probabilistic model to predict late rectal toxicity based on the parameterized dose distribution and assessed its predictive power using data from the MRC RT01 trial (ISCTRN 47772397). The endpoints under consideration were rectal bleeding, loose stools, and a global toxicity score. We extract simple rules identifying 3D dose patterns related to a specifically low risk of complication. Normal tissue complication probability (NTCP) models based on parameterized representations of geometrical and volumetric measures resulted in areas under the curve (AUCs) of 0.66, 0.63 and 0.67 for predicting rectal bleeding, loose stools and global toxicity, respectively. In comparison, NTCP models based on standard DVHs performed worse and resulted in AUCs of 0.59 for all three endpoints. In conclusion, we have presented low-dimensional, interpretable and nonlinear NTCP models based on the parameterized representation of the dose to the rectal wall. These models had a higher predictive power than models based on standard DVHs and their low dimensionality allowed for the identification of 3D dose patterns related to a low risk of complication.
Improving Low-dose Cardiac CT Images based on 3D Sparse Representation
NASA Astrophysics Data System (ADS)
Shi, Luyao; Hu, Yining; Chen, Yang; Yin, Xindao; Shu, Huazhong; Luo, Limin; Coatrieux, Jean-Louis
2016-03-01
Cardiac computed tomography (CCT) is a reliable and accurate tool for diagnosis of coronary artery diseases and is also frequently used in surgery guidance. Low-dose scans should be considered in order to alleviate the harm to patients caused by X-ray radiation. However, low dose CT (LDCT) images tend to be degraded by quantum noise and streak artifacts. In order to improve the cardiac LDCT image quality, a 3D sparse representation-based processing (3D SR) is proposed by exploiting the sparsity and regularity of 3D anatomical features in CCT. The proposed method was evaluated by a clinical study of 14 patients. The performance of the proposed method was compared to the 2D spares representation-based processing (2D SR) and the state-of-the-art noise reduction algorithm BM4D. The visual assessment, quantitative assessment and qualitative assessment results show that the proposed approach can lead to effective noise/artifact suppression and detail preservation. Compared to the other two tested methods, 3D SR method can obtain results with image quality most close to the reference standard dose CT (SDCT) images.
Improving Low-dose Cardiac CT Images based on 3D Sparse Representation
Shi, Luyao; Hu, Yining; Chen, Yang; Yin, Xindao; Shu, Huazhong; Luo, Limin; Coatrieux, Jean-Louis
2016-01-01
Cardiac computed tomography (CCT) is a reliable and accurate tool for diagnosis of coronary artery diseases and is also frequently used in surgery guidance. Low-dose scans should be considered in order to alleviate the harm to patients caused by X-ray radiation. However, low dose CT (LDCT) images tend to be degraded by quantum noise and streak artifacts. In order to improve the cardiac LDCT image quality, a 3D sparse representation-based processing (3D SR) is proposed by exploiting the sparsity and regularity of 3D anatomical features in CCT. The proposed method was evaluated by a clinical study of 14 patients. The performance of the proposed method was compared to the 2D spares representation-based processing (2D SR) and the state-of-the-art noise reduction algorithm BM4D. The visual assessment, quantitative assessment and qualitative assessment results show that the proposed approach can lead to effective noise/artifact suppression and detail preservation. Compared to the other two tested methods, 3D SR method can obtain results with image quality most close to the reference standard dose CT (SDCT) images. PMID:26980176
Improving Low-dose Cardiac CT Images based on 3D Sparse Representation.
Shi, Luyao; Hu, Yining; Chen, Yang; Yin, Xindao; Shu, Huazhong; Luo, Limin; Coatrieux, Jean-Louis
2016-03-16
Cardiac computed tomography (CCT) is a reliable and accurate tool for diagnosis of coronary artery diseases and is also frequently used in surgery guidance. Low-dose scans should be considered in order to alleviate the harm to patients caused by X-ray radiation. However, low dose CT (LDCT) images tend to be degraded by quantum noise and streak artifacts. In order to improve the cardiac LDCT image quality, a 3D sparse representation-based processing (3D SR) is proposed by exploiting the sparsity and regularity of 3D anatomical features in CCT. The proposed method was evaluated by a clinical study of 14 patients. The performance of the proposed method was compared to the 2D spares representation-based processing (2D SR) and the state-of-the-art noise reduction algorithm BM4D. The visual assessment, quantitative assessment and qualitative assessment results show that the proposed approach can lead to effective noise/artifact suppression and detail preservation. Compared to the other two tested methods, 3D SR method can obtain results with image quality most close to the reference standard dose CT (SDCT) images.
Efficient calculation method for realistic deep 3D scene hologram using orthographic projection
NASA Astrophysics Data System (ADS)
Igarashi, Shunsuke; Nakamura, Tomoya; Matsushima, Kyoji; Yamaguchi, Masahiro
2016-03-01
We propose a fast calculation method to synthesize a computer-generated hologram (CGH) of realistic deep three-dimensional (3D) scene. In our previous study, we have proposed a calculation method of CGH for reproducing such scene called ray-sampling-plane (RSP) method, in which light-ray information of a scene is converted to wavefront, and the wavefront is numerically propagated based on diffraction theory. In this paper, we introduce orthographic projection to the RSP method for accelerating calculation time. By numerical experiments, we verified the accelerated calculation with the ratio of 28-times compared to the conventional RSP method. The calculated CGH was fabricated by the printing system using laser lithography and demonstrated deep 3D image reconstruction in 52mm×52mm with realistic appearance effect such as gloss and translucent effect.
Deformable 3D-2D registration for CT and its application to low dose tomographic fluoroscopy
NASA Astrophysics Data System (ADS)
Flach, Barbara; Brehm, Marcus; Sawall, Stefan; Kachelrieß, Marc
2014-12-01
Many applications in medical imaging include image registration for matching of images from the same or different modalities. In the case of full data sampling, the respective reconstructed images are usually of such a good image quality that standard deformable volume-to-volume (3D-3D) registration approaches can be applied. But research in temporal-correlated image reconstruction and dose reductions increases the number of cases where rawdata are available from only few projection angles. Here, deteriorated image quality leads to non-acceptable deformable volume-to-volume registration results. Therefore a registration approach is required that is robust against a decreasing number of projections defining the target position. We propose a deformable volume-to-rawdata (3D-2D) registration method that aims at finding a displacement vector field maximizing the alignment of a CT volume and the acquired rawdata based on the sum of squared differences in rawdata domain. The registration is constrained by a regularization term in accordance with a fluid-based diffusion. Both cost function components, the rawdata fidelity and the regularization term, are optimized in an alternating manner. The matching criterion is optimized by a conjugate gradient descent for nonlinear functions, while the regularization is realized by convolution of the vector fields with Gaussian kernels. We validate the proposed method and compare it to the demons algorithm, a well-known 3D-3D registration method. The comparison is done for a range of 4-60 target projections using datasets from low dose tomographic fluoroscopy as an application example. The results show a high correlation to the ground truth target position without introducing artifacts even in the case of very few projections. In particular the matching in the rawdata domain is improved compared to the 3D-3D registration for the investigated range. The proposed volume-to-rawdata registration increases the robustness regarding sparse
Deformable 3D-2D registration for CT and its application to low dose tomographic fluoroscopy.
Flach, Barbara; Brehm, Marcus; Sawall, Stefan; Kachelrieß, Marc
2014-12-21
Many applications in medical imaging include image registration for matching of images from the same or different modalities. In the case of full data sampling, the respective reconstructed images are usually of such a good image quality that standard deformable volume-to-volume (3D-3D) registration approaches can be applied. But research in temporal-correlated image reconstruction and dose reductions increases the number of cases where rawdata are available from only few projection angles. Here, deteriorated image quality leads to non-acceptable deformable volume-to-volume registration results. Therefore a registration approach is required that is robust against a decreasing number of projections defining the target position. We propose a deformable volume-to-rawdata (3D-2D) registration method that aims at finding a displacement vector field maximizing the alignment of a CT volume and the acquired rawdata based on the sum of squared differences in rawdata domain. The registration is constrained by a regularization term in accordance with a fluid-based diffusion. Both cost function components, the rawdata fidelity and the regularization term, are optimized in an alternating manner. The matching criterion is optimized by a conjugate gradient descent for nonlinear functions, while the regularization is realized by convolution of the vector fields with Gaussian kernels. We validate the proposed method and compare it to the demons algorithm, a well-known 3D-3D registration method. The comparison is done for a range of 4-60 target projections using datasets from low dose tomographic fluoroscopy as an application example. The results show a high correlation to the ground truth target position without introducing artifacts even in the case of very few projections. In particular the matching in the rawdata domain is improved compared to the 3D-3D registration for the investigated range. The proposed volume-to-rawdata registration increases the robustness regarding sparse
Dose distribution and mapping with 3D imaging presentation in intraoral and panoramic examinations
NASA Astrophysics Data System (ADS)
Chen, Hsiu-Ling; Huang, Yung-Hui; Wu, Tung-Hsin; Wang, Shih-Yuan; Lee, Jason J. S.
2011-10-01
In current medical imaging applications, high quality images not only provide more diagnostic value for anatomic delineation but also offer functional information for treatment direction. However, this approach would potentially subscribe higher radiation dose in dental radiographies, which has been putatively associated with low-birth-weight during pregnancy, which affects the hypothalamus-pituitary-thyroid axis or thereby directly affects the reproductive organs. The aim of this study was to apply the high resolution 3-D image mapping technique to evaluate radiation doses from the following aspects: (1) verifying operating parameters of dental X-ray units, (2) measuring the leakage radiations and (3) mapping dose with 3-D radiographic imaging to evaluate dose distribution in head and neck regions. From the study results, we found that (1) leakage radiation from X-ray units was about 21.31±15.24 mR/h (<100 mR/h), (2) error of actual tube voltage for 60 kVp setting was from 0.2% to 6.5%, with an average of 2.5% (<7%) and (3) the error of exposure time for a 0.5-1.5 s setting was within 0.7-8.5%, with an average of 7.3% (<10%) error as well. Our 3-D dose mapping demonstrated that dose values were relatively lower in soft tissues and higher in bone surfaces compared with other investigations. Multiple causes could contribute to these variations, including irradiation geometry, image equipment and type of technique applied, etc. From the results, we also observed that larger accumulated doses were presented in certain critical organs, such as salivary gland, thyroid gland and bone marrow. Potential biological affects associated with these findings warrant further investigation.
Perfetti, Christopher M; Rearden, Bradley T
2014-01-01
This work introduces a new approach for calculating sensitivity coefficients for generalized neutronic responses to nuclear data uncertainties using continuous-energy Monte Carlo methods. The approach presented in this paper, known as the GEAR-MC method, allows for the calculation of generalized sensitivity coefficients for multiple responses in a single Monte Carlo calculation with no nuclear data perturbations or knowledge of nuclear covariance data. The theory behind the GEAR-MC method is presented here, and proof of principle is demonstrated by using the GEAR-MC method to calculate sensitivity coefficients for responses in several 3D, continuous-energy Monte Carlo applications.
A flexible-dose dispenser for immediate and extended release 3D printed tablets.
Pietrzak, Katarzyna; Isreb, Abdullah; Alhnan, Mohamed A
2015-10-01
The advances in personalised medicine increased the demand for a fast, accurate and reliable production method of tablets that can be digitally controlled by healthcare staff. A flexible dose tablet system is presented in this study that proved to be suitable for immediate and extended release tablets with a realistic drug loading and an easy-to-swallow tablet design. The method bridges the affordable and digitally controlled Fused Deposition Modelling (FDM) 3D printing with a standard pharmaceutical manufacturing process, Hot Melt Extrusion (HME). The reported method was compatible with three methacrylic polymers (Eudragit RL, RS and E) as well as a cellulose-based one (hydroxypropyl cellulose, HPC SSL). The use of a HME based pharmaceutical filament preserved the linear relationship between the mass and printed volume and was utilized to digitally control the dose via an input from computer software with dose accuracy in the range of 91-95%. Higher resolution printing quality doubled the printing time, but showed a little effect on in vitro release pattern of theophylline and weight accuracy. Physical characterization studies indicated that the majority of the model drug (theophylline) in the 3D printed tablet exists in a crystal form. Owing to the small size, ease of use and the highly adjustable nature of FDM 3D printers, the method holds promise for future individualised treatment.
A flexible-dose dispenser for immediate and extended release 3D printed tablets.
Pietrzak, Katarzyna; Isreb, Abdullah; Alhnan, Mohamed A
2015-10-01
The advances in personalised medicine increased the demand for a fast, accurate and reliable production method of tablets that can be digitally controlled by healthcare staff. A flexible dose tablet system is presented in this study that proved to be suitable for immediate and extended release tablets with a realistic drug loading and an easy-to-swallow tablet design. The method bridges the affordable and digitally controlled Fused Deposition Modelling (FDM) 3D printing with a standard pharmaceutical manufacturing process, Hot Melt Extrusion (HME). The reported method was compatible with three methacrylic polymers (Eudragit RL, RS and E) as well as a cellulose-based one (hydroxypropyl cellulose, HPC SSL). The use of a HME based pharmaceutical filament preserved the linear relationship between the mass and printed volume and was utilized to digitally control the dose via an input from computer software with dose accuracy in the range of 91-95%. Higher resolution printing quality doubled the printing time, but showed a little effect on in vitro release pattern of theophylline and weight accuracy. Physical characterization studies indicated that the majority of the model drug (theophylline) in the 3D printed tablet exists in a crystal form. Owing to the small size, ease of use and the highly adjustable nature of FDM 3D printers, the method holds promise for future individualised treatment. PMID:26277660
A 3D dose model for low level laser / led therapy biostimulation and bioinhibition
NASA Astrophysics Data System (ADS)
Carroll, James D.
2008-03-01
There have been numerous reports describing the phenomena of biostimulation and bioinhibition using low-level laser therapy (LLLT) and other light and IR sources within the laboratory and in clinical trials. Stimulation or inhibition employed correctly has been shown clinically to reduce pain, improve tissue repair, resolve inflammation and stimulate the immune system. All these effects are sensitive to different irradiance and / or different energy (sometimes described as dose rate or fluence rate effects). The typical ranges for biostimulation and bioinhibition will be examined and a 3D Arndt Schulz style model proposed to illustrate possible 'dose sweet spots' for the intended clinical effects.
Vinogradskiy, Yevgeniy Y.; Balter, Peter; Followill, David S.; Alvarez, Paola E.; White, R. Allen; Starkschall, George
2009-11-15
Purpose: Four-dimensional (4D) dose calculation algorithms, which explicitly incorporate respiratory motion in the calculation of doses, have the potential to improve the accuracy of dose calculations in thoracic treatment planning; however, they generally require greater computing power and resources than currently used for three-dimensional (3D) dose calculations. The purpose of this work was to quantify the increase in accuracy of 4D dose calculations versus 3D dose calculations. Methods: The accuracy of each dose calculation algorithm was assessed using measurements made with two phantoms. Specifically, the authors used a rigid moving anthropomorphic thoracic phantom and an anthropomorphic thoracic phantom with a deformable lung insert. To incorporate a clinically relevant range of scenarios, they programed the phantoms to move and deform with two motion patterns: A sinusoidal motion pattern and an irregular motion pattern that was extracted from an actual patient's breathing profile. For each combination of phantom and motion pattern, three plans were created: A single-beam plan, a multiple-beam plan, and an intensity-modulated radiation therapy plan. Doses were calculated using 4D dose calculation methods as well as conventional 3D dose calculation methods. The rigid moving and deforming phantoms were irradiated according to the three treatment plans and doses were measured using thermoluminescent dosimeters (TLDs) and radiochromic film. The accuracy of each dose calculation algorithm was assessed using measured-to-calculated TLD doses and a {gamma} analysis. Results: No significant differences were observed between the measured-to-calculated TLD ratios among 4D and 3D dose calculations. The {gamma} results revealed that 4D dose calculations had significantly greater percentage of pixels passing the 5%/3 mm criteria than 3D dose calculations. Conclusions: These results indicate no significant differences in the accuracy between the 4D and the 3D dose
3D calculation of Tucson-Melbourne 3NF effect in triton binding energy
Hadizadeh, M. R.; Tomio, L.; Bayegan, S.
2010-08-04
As an application of the new realistic three-dimensional (3D) formalism reported recently for three-nucleon (3N) bound states, an attempt is made to study the effect of three-nucleon forces (3NFs) in triton binding energy in a non partial wave (PW) approach. The spin-isospin dependent 3N Faddeev integral equations with the inclusion of 3NFs, which are formulated as function of vector Jacobi momenta, specifically the magnitudes of the momenta and the angle between them, are solved with Bonn-B and Tucson-Melbourne NN and 3N forces in operator forms which can be incorporated in our 3D formalism. The comparison with numerical results in both, novel 3D and standard PW schemes, shows that non PW calculations avoid the very involved angular momentum algebra occurring for the permutations and transformations and it is more efficient and less cumbersome for considering the 3NF.
Highly accurate video coordinate generation for automatic 3-D trajectory calculation
NASA Astrophysics Data System (ADS)
Macleod, A.; Morris, Julian R. W.; Lyster, M.
1990-08-01
Most TV-based motion analysis systems, including the original version of 1/ICON, produce 3D coordinates by combining pre-tracked 2D trajectories from each camera. The latest version of the system, VICON-VX, uses totally automatic 3D trajectory calculation using the Geometric Self Identification (GSI) technique. This is achieved by matching unsorted 2D image coordinates from all cameras, looking for intersecting marker 'rays', and matching intersections into 3D trajectories. Effective GSI, with low false-positive intersection rates is only possible with highly accurate 2D data, produced by stable, high-resolution coordinate generators, and incorporating appropriate compensation for lens distortions. Data capture software and hardware have been completely redesigned to achieve this accuracy, together with higher throughput rates and better resistance to errors. In addition, a new ADC facility has been incorporated to allow very high speed analog data acquisition, synchronised with video measurements.
NASA Astrophysics Data System (ADS)
Keyvanloo Shahrestanaky, Amirmohamad
The integration of a clinical linear accelerator (linac) with a magnetic resonance imaging (MRI) system would provide real-time tumor tracking. The magnetic fields of linac-MR systems modify the path of contaminant electrons in photon beams, which alters patient skin dose. In this work, we used Monte Carlo calculations that incorporate realistic 3D magnetic field models of longitudinal and transverse linac-MR systems to accurately quantify the changes in skin dose. The results show that fringe fields of realistic 3D B-fields decay rapidly and have a very small magnitude at the linac’s head. As a result, for longitudinal linac-MR systems only a small increase in the entrance skin dose is predicted. For transverse linac-MR systems, changes to the entrance skin dose are small for most scenarios. On the exit side, however, a fairly large increase is observed for perpendicular beams due to the electron return effect, but significantly drops for large oblique angles of incidence.
Huang, M; Benhabib, S; Cardan, R; Brezovich, I; Popple, R; Faught, A; Followill, D
2014-06-15
Purpose: To compare 3D reconstructed dose of IMRT plans from 3D diode array measurements with measurements in anthropomorphic phantoms. Methods: Six IMRT plans were created for the IROC Houston (RPC) head and neck (H and N) and lung phantoms following IROC Houston planning protocols. The plans included flattened and unflattened beam energies ranging from 6 MV to 15 MV and both static and dynamic MLC tecH and Niques. Each plan was delivered three times to the respective anthropomorphic phantom, each of which contained thermoluminescent dosimeters (TLDs) and radiochromic films (RCFs). The plans were also delivered to a Delta4 diode array (Scandidos, Uppsala, Sweden). Irradiations were done using a TrueBeam STx (Varian Medical Systems, Palo Alto, CA). The dose in the patient was calculated by the Delta4 software, which used the diode measurements to estimate incident energy fluence and a kernel-based pencil beam algorithm to calculate dose. The 3D dose results were compared with the TLD and RCF measurements. Results: In the lung, the average difference between TLDs and Delta4 calculations was 5% (range 2%–7%). For the H and N, the average differences were 2.4% (range 0%–4.5%) and 1.1% (range 0%–2%) for the high- and low-dose targets, respectively, and 12% (range 10%-13%) for the organ-at-risk simulating the spinal cord. For the RCF and criteria of 7%/4mm, 5%/3mm, and 3%/3mm, the average gamma-index pass rates were 95.4%, 85.7%, and 76.1%, respectively for the H and N and 76.2%, 57.8%, and 49.5% for the lung. The pass-rate in the lung decreased with increasing beam energy, as expected for a pencil beam algorithm. Conclusion: The H and N phantom dose reconstruction met the IROC Houston acceptance criteria for clinical trials; however, the lung phantom dose did not, most likely due to the inaccuracy of the pencil beam algorithm in the presence of low-density inhomogeneities. Work supported by PHS grant CA10953 and CA81647 (NCI, DHHS)
Prado, Karl L; Kirsner, Steven M; Erice, Rolly C
2003-01-01
This paper describes an innovative method for correctly estimating the effective field size of tangential-breast fields. The method uses an "equivalent triangle" to verify intact breast tangential field monitor-unit settings calculated by a 3D planning system to within 2%. The effects on verification calculations of loss of full scatter due to beam oblique incidence, proximity to field boundaries, and reduced scattering volumes are handled properly. The methodology is validated by comparing calculations performed by the 3D planning system with the respective verification estimates. The accuracy of this technique is established for dose calculations both with and without heterogeneity corrections.
Performance of a commercial optical CT scanner and polymer gel dosimeters for 3-D dose verification
Xu, Y.; Wuu, C.-S.; Maryanski, Marek J.
2004-11-01
Performance analysis of a commercial three-dimensional (3-D) dose mapping system based on optical CT scanning of polymer gels is presented. The system consists of BANG{sup reg}3 polymer gels (MGS Research, Inc., Madison, CT), OCTOPUS{sup TM} laser CT scanner (MGS Research, Inc., Madison, CT), and an in-house developed software for optical CT image reconstruction and 3-D dose distribution comparison between the gel, film measurements and the radiation therapy treatment plans. Various sources of image noise (digitization, electronic, optical, and mechanical) generated by the scanner as well as optical uniformity of the polymer gel are analyzed. The performance of the scanner is further evaluated in terms of the reproducibility of the data acquisition process, the uncertainties at different levels of reconstructed optical density per unit length and the effects of scanning parameters. It is demonstrated that for BANG{sup registered}3 gel phantoms held in cylindrical plastic containers, the relative dose distribution can be reproduced by the scanner with an overall uncertainty of about 3% within approximately 75% of the radius of the container. In regions located closer to the container wall, however, the scanner generates erroneous optical density values that arise from the reflection and refraction of the laser rays at the interface between the gel and the container. The analysis of the accuracy of the polymer gel dosimeter is exemplified by the comparison of the gel/OCT-derived dose distributions with those from film measurements and a commercial treatment planning system (Cadplan, Varian Corporation, Palo Alto, CA) for a 6 cmx6 cm single field of 6 MV x rays and a 3-D conformal radiotherapy (3DCRT) plan. The gel measurements agree with the treatment plans and the film measurements within the '3%-or-2 mm' criterion throughout the usable, artifact-free central region of the gel volume. Discrepancies among the three data sets are analyzed.
Displaying 3D radiation dose on endoscopic video for therapeutic assessment and surgical guidance.
Qiu, Jimmy; Hope, Andrew J; Cho, B C John; Sharpe, Michael B; Dickie, Colleen I; DaCosta, Ralph S; Jaffray, David A; Weersink, Robert A
2012-10-21
We have developed a method to register and display 3D parametric data, in particular radiation dose, on two-dimensional endoscopic images. This registration of radiation dose to endoscopic or optical imaging may be valuable in assessment of normal tissue response to radiation, and visualization of radiated tissues in patients receiving post-radiation surgery. Electromagnetic sensors embedded in a flexible endoscope were used to track the position and orientation of the endoscope allowing registration of 2D endoscopic images to CT volumetric images and radiation doses planned with respect to these images. A surface was rendered from the CT image based on the air/tissue threshold, creating a virtual endoscopic view analogous to the real endoscopic view. Radiation dose at the surface or at known depth below the surface was assigned to each segment of the virtual surface. Dose could be displayed as either a colorwash on this surface or surface isodose lines. By assigning transparency levels to each surface segment based on dose or isoline location, the virtual dose display was overlaid onto the real endoscope image. Spatial accuracy of the dose display was tested using a cylindrical phantom with a treatment plan created for the phantom that matched dose levels with grid lines on the phantom surface. The accuracy of the dose display in these phantoms was 0.8-0.99 mm. To demonstrate clinical feasibility of this approach, the dose display was also tested on clinical data of a patient with laryngeal cancer treated with radiation therapy, with estimated display accuracy of ∼2-3 mm. The utility of the dose display for registration of radiation dose information to the surgical field was further demonstrated in a mock sarcoma case using a leg phantom. With direct overlay of radiation dose on endoscopic imaging, tissue toxicities and tumor response in endoluminal organs can be directly correlated with the actual tissue dose, offering a more nuanced assessment of normal tissue
SU-E-T-511: Do Presage 3D Dosimeters Show Dose Fractionation Sensitivity?
Klawikowski, S; Alqathami, M; Ibbott, G; Adamovics, J; Benning, R
2014-06-01
Purpose: To determine whether Presage 3D polymer dosimeter dose response is sensitive to dose delivery fractionation. Bang gels have demonstrated a dose fractionation related dependence in which a single 400 cGy irradiation would produce a different detector response than four 100 cGy irradiations even if delivered closely in time to one another. Such a fractional dependent response in Presage would be detrimental for measuring multi-beam irradiations. Methods: Two separate batches of Presage were poured into cuvettes, and a third batch was molded into cuvette shaped blocks. A total of 37 cuvettes/blocks were irradiated in a Cobalt-60 irradiator to 400 cGy within solid water phantoms in either one, eight, or sixteen fractions. Another group of 15 cuvettes were also kept unirradiated and used for background subtraction between the pre-scan and post-scan results. The times between fractional deliveries were held constant at 30 seconds and the Cobalt irradiator dose rate was 49 cGy/min. Each Presage batch has a separate dose sensitivity and therefore fractionation response comparisons were only performed within the same batch. The cuvettes were first pre-scanned the day prior to irradiation and post-scanned the day after irradiation. Other than approximately 3 hours warming time prior to each irradiation and optical density measurement the cuvettes were stored in a refrigerator. All cuvettes were stored in a lightless environment throughout manufacturing and testing. The cuvettes’ optical densities were optically measured at 632 nm with a spectrophotometer. Results: No noticeable dose fractionation dependence was detected for any of the three independent batches of Presage for either the eight or sixteen fraction irradiation schemes. Conclusion: These results indicate using Presage 3D dosimeters to measure multi-beam photon irradiations common in IMRT, Gamma Knife, and Cyberknife treatment delivery schemes. Presage dosimeters are made by and trademarked by Heuris
The feasibility assessment of radiation dose of movement 3D NIPAM gel by magnetic resonance imaging
NASA Astrophysics Data System (ADS)
Hsieh, Chih-Ming; Leung, Joseph Hang; Ng, Yu-Bun; Cheng, Chih-Wu; Sun, Jung-Chang; Lin, Ping-Chin; Hsieh, Bor-Tsung
2015-11-01
NIPAM dosimeter is widely accepted and recommended for its 3D distribution and accuracy in dose absorption. Up to the moment, most research works on dose measurement are based on a fixed irradiation target without the consideration of the effect from physiological motion. We present a study to construct a respiratory motion simulating patient anatomical and dosimetry model for the study of dosimetic effect of organ motion. The dose on fixed and motion targets was measured by MRI after a dose adminstration of 1, 2, 5, 8, and 10 Gy from linear accelerator. Comparison of two situations is made. The average sensitivity of fixed NIPAM was 0.1356 s-1/Gy with linearity R2=0.998. The average sensitivity of movement NIPAM was 0.1366 s-1/Gy with linearity R2=0.998 both having only 0.001 of the sensitivity difference. The difference between the two based on dose rate dependency, position and depth was not significant. There was thus no apparent impact on NIPAM dosimeter from physiological motion. The high sensitivity, linearity and stability of NIPAM dosimeter proved to be an ideal apparatus in the dose measurement in these circumstances.
Russo, James K.; Armeson, Kent E.; Richardson, Susan
2012-05-01
Purpose: To evaluate bladder and rectal doses using two-dimensional (2D) and 3D treatment planning for vaginal cuff high-dose rate (HDR) in endometrial cancer. Methods and Materials: Ninety-one consecutive patients treated between 2000 and 2007 were evaluated. Seventy-one and 20 patients underwent 2D and 3D planning, respectively. Each patient received six fractions prescribed at 0.5 cm to the superior 3 cm of the vagina. International Commission on Radiation Units and Measurements (ICRU) doses were calculated for 2D patients. Maximum and 2-cc doses were calculated for 3D patients. Organ doses were normalized to prescription dose. Results: Bladder maximum doses were 178% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were no different than ICRU doses (p = 0.22). Two-cubic centimeter doses were 59% of maximum doses (p < 0.0001). Rectal maximum doses were 137% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were 87% of ICRU doses (p < 0.0001). Two-cubic centimeter doses were 64% of maximum doses (p < 0.0001). Using the first 1, 2, 3, 4 or 5 fractions, we predicted the final bladder dose to within 10% for 44%, 59%, 83%, 82%, and 89% of patients by using the ICRU dose, and for 45%, 55%, 80%, 85%, and 85% of patients by using the maximum dose, and for 37%, 68%, 79%, 79%, and 84% of patients by using the 2-cc dose. Using the first 1, 2, 3, 4 or 5 fractions, we predicted the final rectal dose to within 10% for 100%, 100%, 100%, 100%, and 100% of patients by using the ICRU dose, and for 60%, 65%, 70%, 75%, and 75% of patients by using the maximum dose, and for 68%, 95%, 84%, 84%, and 84% of patients by using the 2-cc dose. Conclusions: Doses to organs at risk vary depending on the calculation method. In some cases, final dose accuracy appears to plateau after the third fraction, indicating that simulation and planning may not be necessary in all fractions. A clinically relevant level of accuracy should be determined and further research conducted to address
Pötter, Richard; Haie-Meder, Christine; Van Limbergen, Erik; Barillot, Isabelle; De Brabandere, Marisol; Dimopoulos, Johannes; Dumas, Isabelle; Erickson, Beth; Lang, Stefan; Nulens, An; Petrow, Peter; Rownd, Jason; Kirisits, Christian
2006-01-01
The second part of the GYN GEC ESTRO working group recommendations is focused on 3D dose-volume parameters for brachytherapy of cervical carcinoma. Methods and parameters have been developed and validated from dosimetric, imaging and clinical experience from different institutions (University of Vienna, IGR Paris, University of Leuven). Cumulative dose volume histograms (DVH) are recommended for evaluation of the complex dose heterogeneity. DVH parameters for GTV, HR CTV and IR CTV are the minimum dose delivered to 90 and 100% of the respective volume: D90, D100. The volume, which is enclosed by 150 or 200% of the prescribed dose (V150, V200), is recommended for overall assessment of high dose volumes. V100 is recommended for quality assessment only within a given treatment schedule. For Organs at Risk (OAR) the minimum dose in the most irradiated tissue volume is recommended for reporting: 0.1, 1, and 2 cm3; optional 5 and 10 cm3. Underlying assumptions are: full dose of external beam therapy in the volume of interest, identical location during fractionated brachytherapy, contiguous volumes and contouring of organ walls for >2 cm3. Dose values are reported as absorbed dose and also taking into account different dose rates. The linear-quadratic radiobiological model-equivalent dose (EQD2)-is applied for brachytherapy and is also used for calculating dose from external beam therapy. This formalism allows systematic assessment within one patient, one centre and comparison between different centres with analysis of dose volume relations for GTV, CTV, and OAR. Recommendations for the transition period from traditional to 3D image-based cervix cancer brachytherapy are formulated. Supplementary data (available in the electronic version of this paper) deals with aspects of 3D imaging, radiation physics, radiation biology, dose at reference points and dimensions and volumes for the GTV and CTV (adding to [Haie-Meder C, Pötter R, Van Limbergen E et al. Recommendations from
Tensor decomposition in electronic structure calculations on 3D Cartesian grids
Khoromskij, B.N. Khoromskaia, V.; Chinnamsetty, S.R.; Flad, H.-J.
2009-09-01
In this paper, we investigate a novel approach based on the combination of Tucker-type and canonical tensor decomposition techniques for the efficient numerical approximation of functions and operators in electronic structure calculations. In particular, we study applicability of tensor approximations for the numerical solution of Hartree-Fock and Kohn-Sham equations on 3D Cartesian grids. We show that the orthogonal Tucker-type tensor approximation of electron density and Hartree potential of simple molecules leads to low tensor rank representations. This enables an efficient tensor-product convolution scheme for the computation of the Hartree potential using a collocation-type approximation via piecewise constant basis functions on a uniform nxnxn grid. Combined with the Richardson extrapolation, our approach exhibits O(h{sup 3}) convergence in the grid-size h=O(n{sup -1}). Moreover, this requires O(3rn+r{sup 3}) storage, where r denotes the Tucker rank of the electron density with r=O(logn), almost uniformly in n. For example, calculations of the Coulomb matrix and the Hartree-Fock energy for the CH{sub 4} molecule, with a pseudopotential on the C atom, achieved accuracies of the order of 10{sup -6} hartree with a grid-size n of several hundreds. Since the tensor-product convolution in 3D is performed via 1D convolution transforms, our scheme markedly outperforms the 3D-FFT in both the computing time and storage requirements.
Feasibility of reduced-dose 3D/4D-DSA using a weighted edge preserving filter
NASA Astrophysics Data System (ADS)
Oberstar, Erick L.; Speidel, Michael A.; Davis, Brian J.; Strother, Charles; Mistretta, Charles
2016-03-01
A conventional 3D/4D digital subtraction angiogram (DSA) requires two rotational acquisitions (mask and fill) to compute the log-subtracted projections that are used to reconstruct a 3D/4D volume. Since all of the vascular information is contained in the fill acquisition, it is hypothesized that it is possible to reduce the x-ray dose of the mask acquisition substantially and still obtain subtracted projections adequate to reconstruct a 3D/4D volume with noise level comparable to a full dose acquisition. A full dose mask and fill acquisition were acquired from a clinical study to provide a known full dose reference reconstruction. Gaussian noise was added to the mask acquisition to simulate a mask acquisition acquired at 10% relative dose. Noise in the low-dose mask projections was reduced with a weighted edge preserving (WEP) filter designed to preserve bony edges while suppressing noise. 2D log-subtracted projections were computed from the filtered low-dose mask and full-dose fill projections, and then 3D/4D-DSA reconstruction algorithms were applied. Additional bilateral filtering was applied to the 3D volumes. The signal-to-noise ratio measured in the filtered 3D/4D-DSA volumes was compared to the full dose case. The average ratio of filtered low-dose SNR to full-dose SNR was 1.07 for the 3D-DSA and 1.05 for the 4D-DSA, indicating the method is a feasible approach to restoring SNR in DSA scans acquired with a low-dose mask. The method was also tested in a phantom study with full dose fill and 22% dose mask.
Improving low-dose cardiac CT images using 3D sparse representation based processing
NASA Astrophysics Data System (ADS)
Shi, Luyao; Chen, Yang; Luo, Limin
2015-03-01
Cardiac computed tomography (CCT) has been widely used in diagnoses of coronary artery diseases due to the continuously improving temporal and spatial resolution. When helical CT with a lower pitch scanning mode is used, the effective radiation dose can be significant when compared to other radiological exams. Many methods have been developed to reduce radiation dose in coronary CT exams including high pitch scans using dual source CT scanners and step-and-shot scanning mode for both single source and dual source CT scanners. Additionally, software methods have also been proposed to reduce noise in the reconstructed CT images and thus offering the opportunity to reduce radiation dose while maintaining the desired diagnostic performance of a certain imaging task. In this paper, we propose that low-dose scans should be considered in order to avoid the harm from accumulating unnecessary X-ray radiation. However, low dose CT (LDCT) images tend to be degraded by quantum noise and streak artifacts. Accordingly, in this paper, a 3D dictionary representation based image processing method is proposed to reduce CT image noise. Information on both spatial and temporal structure continuity is utilized in sparse representation to improve the performance of the image processing method. Clinical cases were used to validate the proposed method.
3D-printed surface mould applicator for high-dose-rate brachytherapy
NASA Astrophysics Data System (ADS)
Schumacher, Mark; Lasso, Andras; Cumming, Ian; Rankin, Adam; Falkson, Conrad B.; Schreiner, L. John; Joshi, Chandra; Fichtinger, Gabor
2015-03-01
In contemporary high-dose-rate brachytherapy treatment of superficial tumors, catheters are placed in a wax mould. The creation of current wax models is a difficult and time consuming proces.The irradiation plan can only be computed post-construction and requires a second CT scan. In case no satisfactory dose plan can be created, the mould is discarded and the process is repeated. The objective of this work was to develop an automated method to replace suboptimal wax moulding. We developed a method to design and manufacture moulds that guarantee to yield satisfactory dosimetry. A 3D-printed mould with channels for the catheters designed from the patient's CT and mounted on a patient-specific thermoplastic mesh mask. The mould planner was implemented as an open-source module in the 3D Slicer platform. Series of test moulds were created to accommodate standard brachytherapy catheters of 1.70mm diameter. A calibration object was used to conclude that tunnels with a diameter of 2.25mm, minimum 12mm radius of curvature, and 1.0mm open channel gave the best fit for this printer/catheter combination. Moulds were created from the CT scan of thermoplastic mesh masks of actual patients. The patient-specific moulds have been visually verified to fit on the thermoplastic meshes. The masks were visually shown to fit onto the thermoplastic meshes, next the resulting dosimetry will have to be compared with treatment plans and dosimetry achieved with conventional wax moulds in order to validate our 3D printed moulds.
Doran, Simon; Gorjiara, Tina; Kacperek, Andrzej; Adamovics, John; Kuncic, Zdenka; Baldock, Clive
2015-01-21
Dosimetry of proton beams using 3D imaging of chemical dosimeters is complicated by a variation with proton linear energy transfer (LET) of the dose-response (the so-called 'quenching effect'). Simple theoretical arguments lead to the conclusion that the total absorbed dose from multiple irradiations with different LETs cannot be uniquely determined from post-irradiation imaging measurements on the dosimeter. Thus, a direct inversion of the imaging data is not possible and the proposition is made to use a forward model based on appropriate output from a planning system to predict the 3D response of the dosimeter. In addition to the quenching effect, it is well known that chemical dosimeters have a non-linear response at high doses. To the best of our knowledge it has not yet been determined how this phenomenon is affected by LET. The implications for dosimetry of a number of potential scenarios are examined.Dosimeter response as a function of depth (and hence LET) was measured for four samples of the radiochromic plastic PRESAGE(®), using an optical computed tomography readout and entrance doses of 2.0 Gy, 4.0 Gy, 7.8 Gy and 14.7 Gy, respectively. The dosimeter response was separated into two components, a single-exponential low-LET response and a LET-dependent quenching. For the particular formulation of PRESAGE(®) used, deviations from linearity of the dosimeter response became significant for doses above approximately 16 Gy. In a second experiment, three samples were each irradiated with two separate beams of 4 Gy in various different configurations. On the basis of the previous characterizations, two different models were tested for the calculation of the combined quenching effect from two contributions with different LETs. It was concluded that a linear superposition model with separate calculation of the quenching for each irradiation did not match the measured result where two beams overlapped. A second model, which used the concept of an
An efficient 3D traveltime calculation using coarse-grid mesh for shallow-depth source
NASA Astrophysics Data System (ADS)
Son, Woohyun; Pyun, Sukjoon; Lee, Ho-Young; Koo, Nam-Hyung; Shin, Changsoo
2016-10-01
3D Kirchhoff pre-stack depth migration requires an efficient algorithm to compute first-arrival traveltimes. In this paper, we exploited a wave-equation-based traveltime calculation algorithm, which is called the suppressed wave equation estimation of traveltime (SWEET), and the equivalent source distribution (ESD) algorithm. The motivation of using the SWEET algorithm is to solve the Laplace-domain wave equation using coarse grid spacing to calculate first-arrival traveltimes. However, if a real source is located at shallow-depth close to free surface, we cannot accurately calculate the wavefield using coarse grid spacing. So, we need an additional algorithm to correctly simulate the shallow source even for the coarse grid mesh. The ESD algorithm is a method to define a set of distributed nodal sources that approximate a point source at the inter-nodal location in a velocity model with large grid spacing. Thanks to the ESD algorithm, we can efficiently calculate the first-arrival traveltimes of waves emitted from shallow source point even when we solve the Laplace-domain wave equation using a coarse-grid mesh. The proposed algorithm is applied to the SEG/EAGE 3D salt model. From the result, we note that the combination of SWEET and ESD algorithms can be successfully used for the traveltime calculation under the condition of a shallow-depth source. We also confirmed that our algorithm using coarse-grid mesh requires less computational time than the conventional SWEET algorithm using relatively fine-grid mesh.
Feasibility of RACT for 3D dose measurement and range verification in a water phantom
Alsanea, Fahed; Moskvin, Vadim; Stantz, Keith M.
2015-02-15
Purpose: The objective of this study is to establish the feasibility of using radiation-induced acoustics to measure the range and Bragg peak dose from a pulsed proton beam. Simulation studies implementing a prototype scanner design based on computed tomographic methods were performed to investigate the sensitivity to proton range and integral dose. Methods: Derived from thermodynamic wave equation, the pressure signals generated from the dose deposited from a pulsed proton beam with a 1 cm lateral beam width and a range of 16, 20, and 27 cm in water using Monte Carlo methods were simulated. The resulting dosimetric images were reconstructed implementing a 3D filtered backprojection algorithm and the pressure signals acquired from a 71-transducer array with a cylindrical geometry (30 × 40 cm) rotated over 2π about its central axis. Dependencies on the detector bandwidth and proton beam pulse width were performed, after which, different noise levels were added to the detector signals (using 1 μs pulse width and a 0.5 MHz cutoff frequency/hydrophone) to investigate the statistical and systematic errors in the proton range (at 20 cm) and Bragg peak dose (of 1 cGy). Results: The reconstructed radioacoustic computed tomographic image intensity was shown to be linearly correlated to the dose within the Bragg peak. And, based on noise dependent studies, a detector sensitivity of 38 mPa was necessary to determine the proton range to within 1.0 mm (full-width at half-maximum) (systematic error < 150 μm) for a 1 cGy Bragg peak dose, where the integral dose within the Bragg peak was measured to within 2%. For existing hydrophone detector sensitivities, a Bragg peak dose of 1.6 cGy is possible. Conclusions: This study demonstrates that computed tomographic scanner based on ionizing radiation-induced acoustics can be used to verify dose distribution and proton range with centi-Gray sensitivity. Realizing this technology into the clinic has the potential to significantly
NASA Astrophysics Data System (ADS)
Rodgers, J.; Tessier, D.; D'Souza, D.; Leung, E.; Hajdok, G.; Fenster, A.
2016-04-01
High-dose-rate (HDR) interstitial brachytherapy is often included in standard-of-care for gynaecological cancers. Needles are currently inserted through a perineal template without any standard real-time imaging modality to assist needle guidance, causing physicians to rely on pre-operative imaging, clinical examination, and experience. While two-dimensional (2D) ultrasound (US) is sometimes used for real-time guidance, visualization of needle placement and depth is difficult and subject to variability and inaccuracy in 2D images. The close proximity to critical organs, in particular the rectum and bladder, can lead to serious complications. We have developed a three-dimensional (3D) transrectal US system and are investigating its use for intra-operative visualization of needle positions used in HDR gynaecological brachytherapy. As a proof-of-concept, four patients were imaged with post-insertion 3D US and x-ray CT. Using software developed in our laboratory, manual rigid registration of the two modalities was performed based on the perineal template's vaginal cylinder. The needle tip and a second point along the needle path were identified for each needle visible in US. The difference between modalities in the needle trajectory and needle tip position was calculated for each identified needle. For the 60 needles placed, the mean trajectory difference was 3.23 +/- 1.65° across the 53 visible needle paths and the mean difference in needle tip position was 3.89 +/- 1.92 mm across the 48 visible needles tips. Based on the preliminary results, 3D transrectal US shows potential for the development of a 3D US-based needle guidance system for interstitial gynaecological brachytherapy.
Quasi-heterogeneous efficient 3-D discrete ordinates CANDU calculations using Attila
Preeti, T.; Rulko, R.
2012-07-01
In this paper, 3-D quasi-heterogeneous large scale parallel Attila calculations of a generic CANDU test problem consisting of 42 complete fuel channels and a perpendicular to fuel reactivity device are presented. The solution method is that of discrete ordinates SN and the computational model is quasi-heterogeneous, i.e. fuel bundle is partially homogenized into five homogeneous rings consistently with the DRAGON code model used by the industry for the incremental cross-section generation. In calculations, the HELIOS-generated 45 macroscopic cross-sections library was used. This approach to CANDU calculations has the following advantages: 1) it allows detailed bundle (and eventually channel) power calculations for each fuel ring in a bundle, 2) it allows the exact reactivity device representation for its precise reactivity worth calculation, and 3) it eliminates the need for incremental cross-sections. Our results are compared to the reference Monte Carlo MCNP solution. In addition, the Attila SN method performance in CANDU calculations characterized by significant up scattering is discussed. (authors)
Development of 3D pseudo pin-by-pin calculation methodology in ANC
Zhang, B.; Mayhue, L.; Huria, H.; Ivanov, B.
2012-07-01
Advanced cores and fuel assembly designs have been developed to improve operational flexibility, economic performance and further enhance safety features of nuclear power plants. The simulation of these new designs, along with strong heterogeneous fuel loading, have brought new challenges to the reactor physics methodologies currently employed in the industrial codes for core analyses. Control rod insertion during normal operation is one operational feature in the AP1000{sup R} plant of Westinghouse next generation Pressurized Water Reactor (PWR) design. This design improves its operational flexibility and efficiency but significantly challenges the conventional reactor physics methods, especially in pin power calculations. The mixture loading of fuel assemblies with significant neutron spectrums causes a strong interaction between different fuel assembly types that is not fully captured with the current core design codes. To overcome the weaknesses of the conventional methods, Westinghouse has developed a state-of-the-art 3D Pin-by-Pin Calculation Methodology (P3C) and successfully implemented in the Westinghouse core design code ANC. The new methodology has been qualified and licensed for pin power prediction. The 3D P3C methodology along with its application and validation will be discussed in the paper. (authors)
First-principles calculations of the interaction between hydrogen and 3d alloying atom in nickel
NASA Astrophysics Data System (ADS)
Liu, Wenguan; Qian, Yuan; Zhang, Dongxun; Liu, Wei; Han, Han
2015-10-01
Knowledge of the behavior of hydrogen (H) in Ni-based alloy is essential for the prediction of Tritium behavior in Molten Salt Reactor. First-principles calculations were performed to investigate the interaction between H and 3d transition metal (TM) alloying atom in Ni-based alloy. H prefers the octahedral interstitial site to the tetrahedral interstitial site energetically. Most of the 3d TM elements (except Zn) attract H. The attraction to H in the Ni-TM-H system can be mainly attributed to the differences in electronegativity. With the large electronegativity, H and Ni gain electrons from the other TM elements, resulting in the enhanced Ni-H bonds which are the source of the attraction to H in the Ni-TM-H system. The obviously covalent-like Cr-H and Co-H bindings are also beneficial to the attraction to H. On the other hand, the repulsion to H in the Ni-Zn-H system is due to the stable electronic configuration of Zn. We mainly utilize the results calculated in 32-atom supercell which corresponds to the case of a relatively high concentration of hydrogen. Our results are in good agreement with the experimental ones.
TE/TM alternating direction scheme for wake field calculation in 3D
NASA Astrophysics Data System (ADS)
Zagorodnov, Igor; Weiland, Thomas
2006-03-01
In the future, accelerators with very short bunches will be used. It demands developing new numerical approaches for long-time calculation of electromagnetic fields in the vicinity of relativistic bunches. The conventional FDTD scheme, used in MAFIA, ABCI and other wake and PIC codes, suffers from numerical grid dispersion and staircase approximation problem. As an effective cure of the dispersion problem, a numerical scheme without dispersion in longitudinal direction can be used as it was shown by Novokhatski et al. [Transition dynamics of the wake fields of ultrashort bunches, TESLA Report 2000-03, DESY, 2000] and Zagorodnov et al. [J. Comput. Phys. 191 (2003) 525]. In this paper, a new economical conservative scheme for short-range wake field calculation in 3D is presented. As numerical examples show, the new scheme is much more accurate on long-time scale than the conventional FDTD approach.
NASA Astrophysics Data System (ADS)
Dunkerley, David A. P.; Funk, Tobias; Speidel, Michael A.
2016-03-01
Scanning-beam digital x-ray (SBDX) is an inverse geometry x-ray fluoroscopy system capable of tomosynthesis-based 3D catheter tracking. This work proposes a method of dose-reduced 3D tracking using dynamic electronic collimation (DEC) of the SBDX scanning x-ray tube. Positions in the 2D focal spot array are selectively activated to create a regionof- interest (ROI) x-ray field around the tracked catheter. The ROI position is updated for each frame based on a motion vector calculated from the two most recent 3D tracking results. The technique was evaluated with SBDX data acquired as a catheter tip inside a chest phantom was pulled along a 3D trajectory. DEC scans were retrospectively generated from the detector images stored for each focal spot position. DEC imaging of a catheter tip in a volume measuring 11.4 cm across at isocenter required 340 active focal spots per frame, versus 4473 spots in full-FOV mode. The dose-area-product (DAP) and peak skin dose (PSD) for DEC versus full field-of-view (FOV) scanning were calculated using an SBDX Monte Carlo simulation code. DAP was reduced to 7.4% to 8.4% of the full-FOV value, consistent with the relative number of active focal spots (7.6%). For image sequences with a moving catheter, PSD was 33.6% to 34.8% of the full-FOV value. The root-mean-squared-deviation between DEC-based 3D tracking coordinates and full-FOV 3D tracking coordinates was less than 0.1 mm. The 3D distance between the tracked tip and the sheath centerline averaged 0.75 mm. Dynamic electronic collimation can reduce dose with minimal change in tracking performance.
Humm, J L; Macklis, R M; Lu, X Q; Yang, Y; Bump, K; Beresford, B; Chin, L M
1995-01-01
In order to better predict and understand the effects of radiopharmaceuticals used for therapy, it is necessary to determine more accurately the radiation absorbed dose to cells in tissue. Using thin-section autoradiography, the spatial distribution of sources relative to the cells can be obtained from a single section with micrometre resolution. By collecting and analysing serial sections, the 3D microscopic distribution of radionuclide relative to the cellular histology, and therefore the dose rate distribution, can be established. In this paper, a method of 3D reconstruction of serial sections is proposed, and measurements are reported of (i) the accuracy and reproducibility of quantitative autoradiography and (ii) the spatial precision with which tissue features from one section can be related to adjacent sections. Uncertainties in the activity determination for the specimen result from activity losses during tissue processing (4-11%), and the variation of grain count per unit activity between batches of serial sections (6-25%). Correlation of the section activity to grain count densities showed deviations ranging from 6-34%. The spatial alignment uncertainties were assessed using nylon fibre fiduciary markers incorporated into the tissue block, and compared to those for alignment based on internal tissue landmarks. The standard deviation for the variation in nylon fibre fiduciary alignment was measured to be 41 microns cm-1, compared to 69 microns cm-1 when internal tissue histology landmarks were used. In addition, tissue shrinkage during histological processing of up to 10% was observed. The implications of these measured activity and spatial distribution uncertainties upon the estimate of cellular dose rate distribution depends upon the range of the radiation emissions. For long-range beta particles, uncertainties in both the activity and spatial distribution translate linearly to the uncertainty in dose rate of < 15%. For short-range emitters (< 100
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.
Precise time-of-flight calculation for 3-D synthetic aperture focusing.
Andresen, Henrik; Nikolov, Svetoslav Ivanov; Jensen, Jørgen Arendt
2009-09-01
Conventional linear arrays can be used for 3-D ultrasound imaging by moving the array in the elevation direction and stacking the planes in a volume. The point-spread function is larger in the elevation plane, because the aperture is smaller and has a fixed elevation focus. Resolution improvements in elevation can be achieved by applying synthetic aperture focusing to the beamformed-in-plane RF data. The proposed method uses a virtual source placed at the elevation focus for postbeamforming. This has previously been done in 2 steps, in-plane focusing followed by synthetic aperture postfocusing in elevation, due to lack of a simple expression for the exact time of flight. This paper presents a new single step method for calculating the time of flight for a 3-D case using a linear array. The new method is more flexible and is able to beamform a fewer number of points much more efficiently. The method is evaluated using both simulated data and phantom measurements using the RASMUS experimental scanner. Computational cost of the method is higher than the 2-step method for a full volume beamforming, but it allows for a reduction of an order-of-magnitude if 3 planes are used for real-time visualization. In addition, the need for a temporary storage of beamformed data is removed.
An approach to 3D magnetic field calculation using numerical and differential algebra methods
Caspi, S.; Helm, M.; Laslett, L.J.; Brady, V.O.
1992-07-17
Motivated by the need for new means for specification and determination of 3D fields that are produced by electromagnetic lens elements in the region interior to coil windings and seeking to obtain techniques that will be convenient for accurate conductor placement and dynamical study of particle motion, we have conveniently gene the representation of a 2D magnetic field to 3D. We have shown that the 3 dimensioal magnetic field components of a multipole magnet in the curl-fire divergence-fire region near the axis r=0 can be derived from one dimensional functions A{sub n}(z) and their derivatives (part 1). In the region interior to coil windings of accelerator magnets the three spatial components of magnet fields can be expressed in terms of harmonic components'' proportional to functions sin (n{theta}) or cos (n{theta}) of the azimuthal angle. The r,z dependence of any such component can then be expressed in terms of powers of r times functions A{sub n}(z) and their derivatives. For twodimensional configurations B{sub z} of course is identically zero, the derivatives of A{sub n}(z) vanish, and the harmonic components of the transverse field then acquire a simple proportionality B{sub r,n} {proportional to} r{sup n-1} sin (n{theta}),B{sub {theta},n} {proportional to} r{sup n-1} cos (n{theta}), whereas in a 3-D configuration the more complex nature of the field gives rise to additional so-called psuedomultipole'' components as judged by additional powers of r required in the development of the field. Computation of the 3-D magnetic field arising at a sequence of field points, as a direct result of a specified current configuration or coil geometry, can be calculated explicitly through use of the Biot-Savart law and from such data the coefficients can then be derived for a general development of the type indicated above. We indicate, discuss, and illustrate two means by which this development may be performed.
NASA Astrophysics Data System (ADS)
Lin, Zhili; Li, Xiaoyan; Zhao, Kuixia; Chen, Xudong; Chen, Mingyu; Pu, Jixiong
2016-06-01
For an inertial confinement fusion (ICF) system, the light intensity distribution in the hohlraum is key to the initial plasma excitation and later laser-plasma interaction process. Based on the concept of coordinate transformation of spatial points and vector, we present a robust method with a detailed procedure that makes the calculation of the three dimensional (3D) light intensity distribution in hohlraum easily. The method is intuitive but powerful enough to solve the complex cases of random number of laser beams with arbitrary polarization states and incidence angles. Its application is exemplified in the Shenguang III Facility (SG-III) that verifies its effectiveness and it is useful for guiding the design of hohlraum structure parameter.
Kassaee, A; Ding, X; McDonough, J; Reiche, M; Witztum, A; Teo, B
2014-06-15
Purpose: To use 3D printers to design and construct complex geometrical phantoms for commissioning treatment planning systems, dose calculation algorithms, quality assurance (QA), dose delivery, and patient dose verifications. Methods: In radiotherapy, complex geometrical phantoms are often required for dose verification, dose delivery and calculation algorithm validation. Presently, fabrication of customized phantoms is limited due to time, expense and challenges in machining of complex shapes. In this work, we designed and utilized 3D printers to fabricate two phantoms for QA purposes. One phantom includes hills and valleys (HV) for verification of intensity modulated radiotherapy for photons, and protons (IMRT and IMPT). The other phantom includes cylindrical cavities (CC) of various sizes for dose verification of inhomogeneities. We evaluated the HV phantoms for an IMPT beam, and the CC phantom to study various inhomogeneity configurations using photon, electron, and proton beams. Gafcromic ™ films were used to quantify the dose distributions delivered to the phantoms. Results: The HV phantom has dimensions of 12 cm × 12 cm and consists of one row and one column of five peaks with heights ranging from 2 to 5 cm. The CC phantom has a size 10 cm × 14 cm and includes 6 cylindrical cavities with length of 7.2 cm and diameters ranging from 0.6 to 1.2 cm. The IMPT evaluation using the HV phantom shows good agreement as compared to the dose distribution calculated with treatment planning system. The CC phantom also shows reasonable agreements for using different algorithms for each beam modalities. Conclusion: 3D printers with submillimiter resolutions are capable of printing complex phantoms for dose verification and QA in radiotherapy. As printing costs decrease and the technology becomes widely available, phantom design and construction will be readily available to any clinic for testing geometries that were not previously feasible.
Fourkal, E.; Veltchev, I.; Lin, M.; Meyer, J.; Koren, S.; Doss, M.; Yu, J. Q.
2013-08-15
Purpose: The introduction of radioembolization with microspheres represents a significant step forward in the treatment of patients with metastatic disease to the liver. This technique uses semiempirical formulae based on body surface area or liver and target volumes to calculate the required total activity for a given patient. However, this treatment modality lacks extremely important information, which is the three-dimensional (3D) dose delivered by microspheres to different organs after their administration. The absence of this information dramatically limits the clinical efficacy of this modality, specifically the predictive power of the treatment. Therefore, the aim of this study is to develop a 3D dose calculation technique that is based on the PET imaging of the infused microspheres.Methods: The Fluka Monte Carlo code was used to calculate the voxel dose kernel for {sup 90}Y source with voxel size equal to that of the PET scan. The measured PET activity distribution was converted to total activity distribution for the subsequent convolution with the voxel dose kernel to obtain the 3D dose distribution. In addition, dose-volume histograms were generated to analyze the dose to the tumor and critical structures.Results: The 3D inpatient dose distribution can be reconstructed from the PET data of a patient scanned after the infusion of microspheres. A total of seven patients have been analyzed so far using the proposed reconstruction method. Four patients underwent treatment with SIR-Spheres for liver metastases from colorectal cancer and three patients were treated with Therasphere for hepatocellular cancer. A total of 14 target tumors were contoured on post-treatment PET-CT scans for dosimetric evaluation. Mean prescription activity was 1.7 GBq (range: 0.58–3.8 GBq). The resulting mean maximum measured dose to targets was 167 Gy (range: 71–311 Gy). Mean minimum dose to 70% of target (D70) was 68 Gy (range: 25–155 Gy). Mean minimum dose to 90% of target
Non-Ideal ELM Stability and Non-Axisymmetric Field Penetration Calculations with M3D-C1
NASA Astrophysics Data System (ADS)
Ferraro, N. M.; Chu, M. S.; Snyder, P. B.; Jardin, S. C.; Luo, X.
2009-11-01
Numerical studies of ELM stability and non-axisymmetric field penetration in diverted DIII-D and NSTX equilibria are presented, with resistive and finite Larmor radius effects included. These results are obtained with the nonlinear two-fluid code M3D-C1, which has recently been extended to allow linear non-axisymmetric calculations. Benchmarks of M3D-C1 with ideal codes ELITE and GATO show good agreement for the linear stability of peeling-ballooning modes in the ideal limit. New calculations of the resistive stability of ideally stable DIII-D equilibria are presented. M3D-C1 has also been used to calculate the linear response to non-axisymmetric external fields; these calculations are benchmarked with Surfmn and MARS-F. New numerical methods implemented in M3D-C1 are presented, including the treatment of boundary conditions with C^1 elements in a non-rectangular mesh.
A Program for Calculating Radiation Dose Rates.
1986-01-27
Version 00 SMART calculates radiation dose rate at the center of the outer cask surface. It can be applied to determine the radiation dose rate on each cask if source conditions, characteristic function, and material conditions in the bottle regions are given. MANYCASK calculates radiation dose rate distribution in a space surrounded by many casks. If the dose rate on each cask surface can be measured, MANYCASK can be applied to predict dose spatial dosemore » rate distribution for any case of cask configuration.« less
PFLOW: A 3-D Numerical Modeling Tool for Calculating Fluid-Pressure Diffusion from Coulomb Strain
NASA Astrophysics Data System (ADS)
Wolf, L. W.; Lee, M.; Meir, A.; Dyer, G.; Ma, K.; Chan, C.
2009-12-01
A new 3D time-dependent pore-pressure diffusion model PFLOW is developed to investigate the response of pore fluids to the crustal deformation generated by strong earthquakes in heterogeneous geologic media. Given crustal strain generated by changes in Coulomb stress, this MATLAB-based code uses Skempton's coefficient to calculate resulting changes fluid pressure. Pore-pressure diffusion can be tracked over time in a user-defined model space with user-prescribed Neumann or Dirchilet boundary conditions and with spatially variable values of permeability. PFLOW employs linear or quadratic finite elements for spatial discretization and first order or second order, explicit or implicit finite difference discretization in time. PFLOW is easily interfaced with output from deformation modeling programs such as Coulomb (Toda et al., 2007) or 3D-DEF (Gomberg and Ellis, 1994). The code is useful for investigating to first-order the evolution of pore pressure changes induced by changes in Coulomb stress and their possible relation to water-level changes in wells or changes in stream discharge. It can also be used for student research and classroom instruction. As an example application, we calculate the coseismic pore pressure changes and diffusion induced by volumetric strain associated with the 1999 Chi-Chi earthquake (Mw = 7.6) in Taiwan. The Chi-Chi earthquake provides an unique opportunity to investigate the spatial and time-dependent poroelastic response of near-field rocks and sediments because there exist extensive observational data of water-level changes and crustal deformation. The integrated model allows us to explore whether changes in Coulomb stress can adequately explain hydrologic anomalies observed in areas such as Taiwan’s western foothills and the Choshui River alluvial plain. To calculate coseismic strain, we use the carefully calibrated finite fault-rupture model of Ma et al. (2005) and the deformation modeling code Coulomb 3.1 (Toda et al., 2007
NASA Astrophysics Data System (ADS)
Przybycin, Anna M.; Scheck-Wenderoth, Magdalena; Schneider, Michael
2014-05-01
The North Alpine Foreland Basin is situated in the northern front of the European Alps and extends over parts of France, Switzerland, Germany and Austria. It formed as a wedge shaped depression since the Tertiary in consequence of the Euro - Adriatic continental collision and the Alpine orogeny. The basin is filled with clastic sediments, the Molasse, originating from erosional processes of the Alps and underlain by Mesozoic sedimentary successions and a Paleozoic crystalline crust. For our study we have focused on the German part of the basin. To investigate the deep structure, the isostatic state and the load distribution of this region we have constructed a 3D structural model of the basin and the Alpine area using available depth and thickness maps, regional scale 3D structural models as well as seismic and well data for the sedimentary part. The crust (from the top Paleozoic down to the Moho (Grad et al. 2008)) has been considered as two-parted with a lighter upper crust and a denser lower crust; the partition has been calculated following the approach of isostatic equilibrium of Pratt (1855). By implementing a seismic Lithosphere-Asthenosphere-Boundary (LAB) (Tesauro 2009) the crustal scale model has been extended to the lithospheric-scale. The layer geometry and the assigned bulk densities of this starting model have been constrained by means of 3D gravity modelling (BGI, 2012). Afterwards the 3D load distribution has been calculated using a 3D finite element method. Our results show that the North Alpine Foreland Basin is not isostatically balanced and that the configuration of the crystalline crust strongly controls the gravity field in this area. Furthermore, our results show that the basin area is influenced by varying lateral load differences down to a depth of more than 150 km what allows a first order statement of the required compensating horizontal stress needed to prevent gravitational collapse of the system. BGI (2012). The International
Opp, Daniel; Nelms, Benjamin E; Zhang, Geoffrey; Stevens, Craig; Feygelman, Vladimir
2013-01-01
3DVH software (Sun Nuclear Corp., Melbourne, FL) is capable of generating a volumetric patient VMAT dose by applying a volumetric perturbation algorithm based on comparing measurement-guided dose reconstruction and TPS-calculated dose to a cylindrical phantom. The primary purpose of this paper is to validate this dose reconstruction on an anthropomorphic heterogeneous thoracic phantom by direct comparison to independent measurements. The dosimetric insert to the phantom is novel, and thus the secondary goal is to demonstrate how it can be used for the hidden target end-to-end testing of VMAT treatments in lung. A dosimetric insert contains a 4 cm diameter unit-density spherical target located inside the right lung (0.21 g/cm(3) density). It has 26 slots arranged in two orthogonal directions, milled to hold optically stimulated luminescent dosimeters (OSLDs). Dose profiles in three cardinal orthogonal directions were obtained for five VMAT plans with varying degrees of modulation. After appropriate OSLD corrections were applied, 3DVH measurement-guided VMAT dose reconstruction agreed 100% with the measurements in the unit density target sphere at 3%/3 mm level (composite analysis) for all profile points for the four less-modulated VMAT plans, and for 96% of the points in the highly modulated C-shape plan (from TG-119). For this latter plan, while 3DVH shows acceptable agreement with independent measurements in the unit density target, in the lung disagreement with experiment is relatively high for both the TPS calculation and 3DVH reconstruction. For the four plans excluding the C-shape, 3%/3 mm overall composite analysis passing rates for 3DVH against independent measurement ranged from 93% to 100%. The C-shape plan was deliberately chosen as a stress test of the algorithm. The dosimetric spatial alignment hidden target test demonstrated the average distance to agreement between the measured and TPS profiles in the steep dose gradient area at the edge of the 2 cm
PARC3D calculations of the F/A-18A HARV inlet vortex generators
NASA Technical Reports Server (NTRS)
Podleski, Steve D.
1995-01-01
NASA Lewis Research Center is currently engaged in a research effort as a team member of the High Alpha Technology Program within the NASA agency. This program uses a specially-equipped F/A-18A aircraft called the High Alpha Research Vehicle (HARV), in an effort to improve the maneuverability of high performance military aircraft at low-subsonic-speed, high-angle-of-attack conditions. The overall objective of the NASA Lewis effort is to develop inlet analysis technology towards efficient airflow delivery to the engine during these maneuvers. One portion of this inlet analysis technology uses computational fluid dynamics to predict installed inlet performance. Most of the F/A-18A HARV geometry, which includes the ramp/splitter plate, side diverter and slot, inlet lip and upper diverter, and deflected leading-edge flap has been modeled. The empennage and rear fuselage have not. A pair of vortex generators located on the bottom wall of the inlet were not modeled initially. These vortex generators were installed to alleviate any flow separation that may be induced by the wheel well protrusion into the inlet wall. Calculations completed with the PARC3D code showed that the pressure recovery has been underpredicted and the flow distortion over-predicted. To improve the correlation of PARC3D predictions with flight and wind tunnel tests, the vortex generators were included in the grid geometry and the results are presented in this report. The grid totals 27 blocks or 1.3 million grid points for the half model, which includes the vortex generator grid blocks. Two flight cases were calculated, a high speed case with a Mach number of 0.8 and angle of attack of 3.4; and a low speed case with a Mach number of 0.43 and angle of attack of 32.2. The vortex generators have a significant effect on the inlet boundary layers at high speed, low angle of attack; and have no effect at low speed, high angle of attack.
Radioactive Dose Assessment and NRC Verification of Licensee Dose Calculation.
1994-09-16
Version 00 PCDOSE was developed for the NRC to perform calculations to determine radioactive dose due to the annual averaged offsite release of liquid and gaseous effluent by U.S commercial nuclear power facilities. Using NRC approved dose assessment methodologies, it acts as an inspector's tool for verifying the compliance of the facility's dose assessment software. PCDOSE duplicates the calculations of the GASPAR II mainframe code as well as calculations using the methodologices of Reg. Guidemore » 1.109 Rev. 1 and NUREG-0133 by optional choice.« less
The PIES2012 Code for Calculating 3D Equilibria with Islands and Stochastic Regions
NASA Astrophysics Data System (ADS)
Monticello, Donald; Reiman, Allan; Raburn, Daniel
2013-10-01
We have made major modifications to the PIES 3D equilibrium code to produce a new version, PIES2012. The new version uses an adaptive radial grid for calculating equilibrium currents. A subset of the flux surfaces conform closely to island separatrices, providing an accurate treatment of the effects driving the neoclassical tearing mode. There is now a set of grid surfaces that conform to the flux surfaces in the interiors of the islands, allowing the proper treatment of the current profiles in the islands, which play an important role in tearing phenomena. We have verified that we can introduce appropriate current profiles in the islands to suppress their growth, allowing us to simulate situations where islands are allowed to grow at some rational surfaces but not others. Placement of grid surfaces between islands is guided by the locations of high order fixed points, allowing us to avoid spectral polution and providing a more robust, and smoother convergence of the code. The code now has an option for turning on a vertical magnetic field to fix the position of the magnetic axis, which models the horizontal feedback positioning of a tokamak plasma. The code has a new option for using a Jacobian-Free Newton Krylov scheme for convergence. The code now also contains a model that properly handles stochastic regions with nonzero pressure gradients. Work supported by DOE contract DE-AC02-09CH11466.
How to calculate the dose of chemotherapy
Gurney, H
2002-01-01
Body surface area-dosing does not account for the complex processes of cytotoxic drug elimination. This leads to an unpredictable variation in effect. Overdosing is easily recognised but it is possible that unrecognised underdosing is more common and may occur in 30% or more of patients receiving standard regimen. Those patients who are inadvertently underdosed are at risk of a significantly reduced anticancer effect. Using published data, it can be calculated that there is an almost 20% relative reduction in survival for women receiving adjuvant chemotherapy for breast cancer as a result of unrecognised underdosing. Similarly, the cure rate of cisplatin-based chemotherapy for advanced testicular cancer may be reduced by as much as 10%. The inaccuracy of body surface area-dosing is more than an inconvenience and it is important that methods for more accurate dose calculation are determined, based on the known drug elimination processes for cytotoxic chemotherapy. Twelve rules for dose calculation of chemotherapy are given that can be used as a guideline until better dose-calculation methods become available. Consideration should be given to using fixed dose guidelines independent of body surface area and based on drug elimination capability, both as a starting dose and for dose adjustment, which may have accuracy, safety and financial advantages. British Journal of Cancer (2002) 86, 1297–1302. DOI: 10.1038/sj/bjc/6600139 www.bjcancer.com © 2002 Cancer Research UK PMID:11953888
Georgia fishery study: implications for dose calculations
Turcotte, M.D.S.
1983-03-28
Fish consumption will contribute a major portion of the estimated individual and population doses from L-Reactor liquid releases and Cs-137 remobilization in Steel Creek. It is therefore important that the values for fish consumption used in dose calculations be as realistic as possible. Since publication of the L-Reactor Environmental Information Document (EID), data have become available on sport fishing in the Savannah River. These data provide SRP with site-specific sport fish harvest and consumption values for use in dose calculations. The Georgia fishery data support the total population fish consumption and calculated dose reported in the EID. The data indicate, however, that both the EID average and maximum individual fish consumption have been underestimated, although each to a different degree. The average fish consumption value used in the EID is approximately 3% below the lower limit of the fish consumption range calculated using the Georgia data. A fish consumption value of 11.3 kg/yr should be used to recalculate dose to the average individual from L-Reactor restart. Maximum fish consumption in the EID has been underestimated by approximately 60%, and doses to the maximum individual should also be recalculated. Future dose calculations should utilize an average fish consumption value of 11.3 kg/yr, and a maximum fish consumption value of 34 kg/yr.
3D Neutronic Analysis in MHD Calculations at ARIES-ST Fusion Reactors Systems
NASA Astrophysics Data System (ADS)
Hançerliogulları, Aybaba; Cini, Mesut
2013-10-01
In this study, we developed new models for liquid wall (FW) state at ARIES-ST fusion reactor systems. ARIES-ST is a 1,000 MWe fusion reactor system based on a low aspect ratio ST plasma. In this article, we analyzed the characteristic properties of magnetohydrodynamics (MHD) and heat transfer conditions by using Monte-Carlo simulation methods (ARIES Team et al. in Fusion Eng Des 49-50:689-695, 2000; Tillack et al. in Fusion Eng Des 65:215-261, 2003) . In fusion applications, liquid metals are traditionally considered to be the best working fluids. The working liquid must be a lithium-containing medium in order to provide adequate tritium that the plasma is self-sustained and that the fusion is a renewable energy source. As for Flibe free surface flows, the MHD effects caused by interaction with the mean flow is negligible, while a fairly uniform flow of thick can be maintained throughout the reactor based on 3-D MHD calculations. In this study, neutronic parameters, that is to say, energy multiplication factor radiation, heat flux and fissile fuel breeding were researched for fusion reactor with various thorium and uranium molten salts. Sufficient tritium amount is needed for the reactor to work itself. In the tritium breeding ratio (TBR) >1.05 ARIES-ST fusion model TBR is >1.1 so that tritium self-sufficiency is maintained for DT fusion systems (Starke et al. in Fusion Energ Des 84:1794-1798, 2009; Najmabadi et al. in Fusion Energ Des 80:3-23, 2006).
Senkesen, Oznur; Tezcanli, Evrim; Buyuksarac, Bora; Ozbay, Ismail
2014-10-01
Radiation fluence changes caused by the dosimeter itself and poor spatial resolution may lead to lack of 3-dimensional (3D) information depending on the features of the dosimeter and quality assurance of dose distributions for high–dose rate (HDR) iridium-192 ({sup 192}Ir) brachytherapy sources is challenging and experimental dosimetry methods used for brachytherapy sources are limited. In this study, we investigated 3D dose distributions of {sup 192}Ir brachytherapy sources for irradiation with single and multiple dwell positions using a normoxic gel dosimeter and compared them with treatment planning system (TPS) calculations. For dose calibration purposes, 100-mL gel-containing vials were irradiated at predefined doses and then scanned in an magnetic resonance (MR) imaging unit. Gel phantoms prepared in 2 spherical glasses were irradiated with {sup 192}Ir for the calculated dwell positions, and MR scans of the phantoms were obtained. The images were analyzed with MATLAB software. Dose distributions and profiles derived with 1-mm resolution were compared with TPS calculations. Linearity was observed between the delivered dose and the reciprocal of the T2 relaxation time constant of the gel. The x-, y-, and z-axes were defined as the sagittal, coronal, and axial planes, respectively, the sagittal and axial planes were defined parallel to the long axis of the source while the coronal plane was defined horizontally to the long axis of the source. The differences between measured and calculated profile widths of 3-cm source length and point source for 70%, 50%, and 30% isodose lines were evaluated at 3 dose levels using 18 profiles of comparison. The calculations for 3-cm source length revealed a difference of > 3 mm in 1 coordinate at 50% profile width on the sagittal plane and 3 coordinates at 70% profile width and 2 coordinates at 50% and 30% profile widths on the axial plane. Calculations on the coronal plane for 3-cm source length showed > 3-mm difference in 1
Amundson, Sally A.
2013-06-12
We have used the MatTek 3-dimensional human skin model to study the gene expression response of a 3D model to low and high dose low LET radiation, and to study the radiation bystander effect as a function of distance from the site of irradiation with either alpha particles or low LET protons. We have found response pathways that appear to be specific for low dose exposures, that could not have been predicted from high dose studies. We also report the time and distance dependent expression of a large number of genes in bystander tissue. the bystander response in 3D tissues showed many similarities to that described previously in 2D cultured cells, but also showed some differences.
Mitchell, Tracy; Truong, Pauline T.; Salter, Lee; Graham, Cathy; Gaffney, Helene; Beckham, Wayne; Olivotto, Ivo A.
2011-04-01
In trials of 3D conformal external beam partial breast radiotherapy (PBRT), the dosimetrist must balance the priorities of achieving high conformity to the target versus minimizing low-dose exposure to the normal structures. This study highlights the caveat that in the absence of a low-dose lung restriction, the use of relatively en-face fields may meet trial-defined requirements but expose the ipsilateral lung to unnecessary low-dose radiation. Adding a low-dose restriction that {<=}20% of the ipsilateral lung should receive 10% of the prescribed dose resulted in successful plans in 88% of cases. This low-dose lung limit should be used in PBRT planning.
Historical river flow rates for dose calculations
Carlton, W.H.
1991-06-10
Annual average river flow rates are required input to the LADTAP Computer Code for calculating offsite doses from liquid releases of radioactive materials to the Savannah River. The source of information on annual river flow rates used in dose calculations varies, depending on whether calculations are for retrospective releases or prospective releases. Examples of these types of releases are: Retrospective - releases from routine operations (annual environmental reports) and short term release incidents that have occurred. Prospective - releases that might be expected in the future from routine or abnormal operation of existing or new facilities (EIS`s, EID`S, SAR`S, etc.). This memorandum provides historical flow rates at the downstream gauging station at Highway 301 for use in retrospective dose calculations and derives flow rate data for the Beaufort-Jasper and Port Wentworth water treatment plants.
HEMP 3D -- a finite difference program for calculating elastic-plastic flow
Wilkins, M.L.
1993-05-26
The HEMP 3D program can be used to solve problems in solid mechanics involving dynamic plasticity and time dependent material behavior and problems in gas dynamics. The equations of motion, the conservation equations, and the constitutive relations are solved by finite difference methods following the format of the HEMP computer simulation program formulated in two space dimensions and time. Presented here is an update of the 1975 report on the HEMP 3D numerical technique. The present report includes the sliding surface routines programmed by Robert Gulliford.
Osewski, Wojciech; Dolla, Łukasz; Radwan, Michał; Szlag, Marta; Rutkowski, Roman; Smolińska, Barbara; Ślosarek, Krzysztof
2014-01-01
Aim To present practical examples of our new algorithm for reconstruction of 3D dose distribution, based on the actual MLC leaf movement. Background DynaLog and RTplan files were used by DDcon software to prepare a new RTplan file for dose distribution reconstruction. Materials and methods Four different clinically relevant scenarios were used to assess the feasibility of the proposed new approach: (1) Reconstruction of whole treatment sessions for prostate cancer; (2) Reconstruction of IMRT verification treatment plan; (3) Dose reconstruction in breast cancer; (4) Reconstruction of interrupted arc and complementary plan for an interrupted VMAT treatment session of prostate cancer. The applied reconstruction method was validated by comparing reconstructed and measured fluence maps. For all statistical analysis, the U Mann–Whitney test was used. Results In the first two and the fourth cases, there were no statistically significant differences between the planned and reconstructed dose distribution (p = 0.910, p = 0.975, p = 0.893, respectively). In the third case the differences were statistically significant (p = 0.015). Treatment plan had to be reconstructed. Conclusion Developed dose distribution reconstruction algorithm presents a very useful QA tool. It provides means for 3D dose distribution verification in patient volume and allows to evaluate the influence of actual MLC leaf motion on the dose distribution. PMID:25337416
NASA Astrophysics Data System (ADS)
Beeler, F.; Andersen, O. K.; Scheffler, M.
1990-01-01
We describe spin-unrestricted self-consistent linear muffin-tin-orbital (LMTO) Green-function calculations for Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu transition-metal impurities in crystalline silicon. Both defect sites of tetrahedral symmetry are considered. All possible charge states with their spin multiplicities, magnetization densities, and energy levels are discussed and explained with a simple physical picture. The early transition-metal interstitial and late transition-metal substitutional 3d ions are found to have low spin. This is in conflict with the generally accepted crystal-field model of Ludwig and Woodbury, but not with available experimental data. For the interstitial 3d ions, the calculated deep donor and acceptor levels reproduce all experimentally observed transitions. For substitutional 3d ions, a large number of predictions is offered to be tested by future experimental studies.
A dose error evaluation study for 4D dose calculations
NASA Astrophysics Data System (ADS)
Milz, Stefan; Wilkens, Jan J.; Ullrich, Wolfgang
2014-10-01
Previous studies have shown that respiration induced motion is not negligible for Stereotactic Body Radiation Therapy. The intrafractional breathing induced motion influences the delivered dose distribution on the underlying patient geometry such as the lung or the abdomen. If a static geometry is used, a planning process for these indications does not represent the entire dynamic process. The quality of a full 4D dose calculation approach depends on the dose coordinate transformation process between deformable geometries. This article provides an evaluation study that introduces an advanced method to verify the quality of numerical dose transformation generated by four different algorithms. The used transformation metric value is based on the deviation of the dose mass histogram (DMH) and the mean dose throughout dose transformation. The study compares the results of four algorithms. In general, two elementary approaches are used: dose mapping and energy transformation. Dose interpolation (DIM) and an advanced concept, so called divergent dose mapping model (dDMM), are used for dose mapping. The algorithms are compared to the basic energy transformation model (bETM) and the energy mass congruent mapping (EMCM). For evaluation 900 small sample regions of interest (ROI) are generated inside an exemplary lung geometry (4DCT). A homogeneous fluence distribution is assumed for dose calculation inside the ROIs. The dose transformations are performed with the four different algorithms. The study investigates the DMH-metric and the mean dose metric for different scenarios (voxel sizes: 8 mm, 4 mm, 2 mm, 1 mm 9 different breathing phases). dDMM achieves the best transformation accuracy in all measured test cases with 3-5% lower errors than the other models. The results of dDMM are reasonable and most efficient in this study, although the model is simple and easy to implement. The EMCM model also achieved suitable results, but the approach requires a more complex
NASA Astrophysics Data System (ADS)
Prihantoro, Rudy; Sutarno, Doddy; Nurhasan
2016-08-01
In this work, we seek numerical solution of 3-D Magnetotelluric (MT) using edge- based finite element method. This approach is a variant of standard finite element method and commonly referred as vector finite-element (VFE) method. Nonphysical solutions usually occurred when the solution is sought using standard finite element which is a node based element. Vector finite element attempt to overcome those nonphysical solutions by using the edges of the element as vector basis. The proposed approach on solving second order Maxwell differential equation of 3-D MT is using direct solver rather than iterative method. Therefore, divergence correction to accelerate the rate of convergence for its iterative solution is no longer needed. The utilization of direct solver has been verified previously for correctness by comparing the resulting solution to those given by analytical solution, as well as the solution come from the other numerical methods, for earth layered model, 2-D models and COMMEMI 3D-2 model. In this work, further verification resulted from recent comparison model of Dublin Test Model 1 (DTM1) is presented.
NASA Astrophysics Data System (ADS)
Rana, Vijay; Rudin, Stephen; Bednarek, Daniel R.
2012-03-01
We have developed a dose-tracking system (DTS) that calculates the radiation dose to the patient's skin in realtime by acquiring exposure parameters and imaging-system-geometry from the digital bus on a Toshiba Infinix C-arm unit. The cumulative dose values are then displayed as a color map on an OpenGL-based 3D graphic of the patient for immediate feedback to the interventionalist. Determination of those elements on the surface of the patient 3D-graphic that intersect the beam and calculation of the dose for these elements in real time demands fast computation. Reducing the size of the elements results in more computation load on the computer processor and therefore a tradeoff occurs between the resolution of the patient graphic and the real-time performance of the DTS. The speed of the DTS for calculating dose to the skin is limited by the central processing unit (CPU) and can be improved by using the parallel processing power of a graphics processing unit (GPU). Here, we compare the performance speed of GPU-based DTS software to that of the current CPU-based software as a function of the resolution of the patient graphics. Results show a tremendous improvement in speed using the GPU. While an increase in the spatial resolution of the patient graphics resulted in slowing down the computational speed of the DTS on the CPU, the speed of the GPU-based DTS was hardly affected. This GPU-based DTS can be a powerful tool for providing accurate, real-time feedback about patient skin-dose to physicians while performing interventional procedures.
Rana, Vijay; Rudin, Stephen; Bednarek, Daniel R
2012-02-23
We have developed a dose-tracking system (DTS) that calculates the radiation dose to the patient's skin in real-time by acquiring exposure parameters and imaging-system-geometry from the digital bus on a Toshiba Infinix C-arm unit. The cumulative dose values are then displayed as a color map on an OpenGL-based 3D graphic of the patient for immediate feedback to the interventionalist. Determination of those elements on the surface of the patient 3D-graphic that intersect the beam and calculation of the dose for these elements in real time demands fast computation. Reducing the size of the elements results in more computation load on the computer processor and therefore a tradeoff occurs between the resolution of the patient graphic and the real-time performance of the DTS. The speed of the DTS for calculating dose to the skin is limited by the central processing unit (CPU) and can be improved by using the parallel processing power of a graphics processing unit (GPU). Here, we compare the performance speed of GPU-based DTS software to that of the current CPU-based software as a function of the resolution of the patient graphics. Results show a tremendous improvement in speed using the GPU. While an increase in the spatial resolution of the patient graphics resulted in slowing down the computational speed of the DTS on the CPU, the speed of the GPU-based DTS was hardly affected. This GPU-based DTS can be a powerful tool for providing accurate, real-time feedback about patient skin-dose to physicians while performing interventional procedures.
Multigroup neutron dose calculations for proton therapy
Kelsey Iv, Charles T; Prinja, Anil K
2009-01-01
We have developed tools for the preparation of coupled multigroup proton/neutron cross section libraries. Our method is to use NJOY to process evaluated nuclear data files for incident particles below 150 MeV and MCNPX to produce data for higher energies. We modified the XSEX3 program of the MCNPX code system to produce Legendre expansions of scattering matrices generated by sampling the physics models that are comparable to the output of the GROUPR routine of NJOY. Our code combines the low and high energy scattering data with user input stopping powers and energy deposition cross sections that we also calculated using MCNPX. Our code also calculates momentum transfer coefficients for the library and optionally applies an energy straggling model to the scattering cross sections and stopping powers. The motivation was initially for deterministic solution of space radiation shielding calculations using Attila, but noting that proton therapy treatment planning may neglect secondary neutron dose assessments because of difficulty and expense, we have also investigated the feasibility of multi group methods for this application. We have shown that multigroup MCNPX solutions for secondary neutron dose compare well with continuous energy solutions and are obtainable with less than half computational cost. This efficiency comparison neglects the cost of preparing the library data, but this becomes negligible when distributed over many multi group calculations. Our deterministic calculations illustrate recognized obstacles that may have to be overcome before discrete ordinates methods can be efficient alternatives for proton therapy neutron dose calculations.
Agriculture-related radiation dose calculations
Furr, J.M.; Mayberry, J.J.; Waite, D.A.
1987-10-01
Estimates of radiation dose to the public must be made at each stage in the identification and qualification process leading to siting a high-level nuclear waste repository. Specifically considering the ingestion pathway, this paper examines questions of reliability and adequacy of dose calculations in relation to five stages of data availability (geologic province, region, area, location, and mass balance) and three methods of calculation (population, population/food production, and food production driven). Calculations were done using the model PABLM with data for the Permian and Palo Duro Basins and the Deaf Smith County area. Extra effort expended in gathering agricultural data at succeeding environmental characterization levels does not appear justified, since dose estimates do not differ greatly; that effort would be better spent determining usage of food types that contribute most to the total dose; and that consumption rate and the air dispersion factor are critical to assessment of radiation dose via the ingestion pathway. 17 refs., 9 figs., 32 tabs.
Analysis of the KROTOS KFC test by coupling X-Ray image analysis and MC3D calculations
Brayer, C.; Charton, A.; Grishchenko, D.; Fouquart, P.; Bullado, Y.; Compagnon, F.; Correggio, P.; Cassiaut-Louis, N.; Piluso, P.
2012-07-01
During a hypothetical severe accident sequence in a Pressurized Water Reactor (PWR), the hot molten materials (corium) issuing from the degraded reactor core may generate a steam explosion if they come in contact with water and may damage the structures and threaten the reactor integrity. The SERENA program is an international OECD project that aims at helping the understanding of this phenomenon also called Fuel Coolant Interaction (FCI) by providing data. CEA takes part in this program by performing tests in its KROTOS facility where steam explosions using prototypic corium can be triggered. Data about the different phases in the premixing are extracted from the KROTOS X-Ray radioscopy images by using KIWI software (KROTOS Image analysis of Water-corium Interaction) currently developed by CEA. The MC3D code, developed by IRSN, is a thermal-hydraulic multiphase code mainly dedicated to FCI studies. It is composed of two applications: premixing and explosion. An overall FCI calculation with MC3D requires a premixing calculation followed by an explosion calculation. The present paper proposes an alternative approach in which all the features of the premixing are extracted from the X-Ray pictures using the KIWI software and transferred to an MC3D dataset for a direct simulation of the explosion. The main hypothesis are discussed as well as the first explosion results obtained with MC3D for the KROTOS KFC test. These results are rather encouraging and are analyzed on the basis of comparisons with the experimental data. (authors)
3D Dose reconstruction: Banding artefacts in cine mode EPID images during VMAT delivery
NASA Astrophysics Data System (ADS)
Woodruff, H. C.; Greer, P. B.
2013-06-01
Cine (continuous) mode images obtained during VMAT delivery are heavily degraded by banding artefacts. We have developed a method to reconstruct the pulse sequence (and hence dose deposited) from open field images. For clinical VMAT fields we have devised a frame averaging strategy that greatly improves image quality and dosimetric information for three-dimensional dose reconstruction.
Sumida, Iori; Yamaguchi, Hajime; Kizaki, Hisao; Aboshi, Keiko; Tsujii, Mari; Yamada, Yuji; Yagi, Masashi; Ogawa, Kazuhiko
2015-01-01
Pretreatment dose verification with beam-by-beam analysis for intensity-modulated radiation therapy (IMRT) is commonly performed with a gantry angle of 0° using a 2D diode detector array. Any changes in multileaf collimator (MLC) position between the actual treatment gantry angle and 0° may result in deviations from the planned dose. We evaluated the effects of MLC positioning errors between the actual treatment gantry angles and nominal gantry angles. A gantry angle correction (GAC) factor was generated by performing a non-gap test at various gantry angles using an electronic portal imaging device (EPID). To convert pixel intensity to dose at the MLC abutment positions, a non-gap test was performed using an EPID and a film at 0° gantry angle. We then assessed the correlations between pixel intensities and doses. Beam-by-beam analyses for 15 prostate IMRT cases as patient-specific quality assurance were performed with a 2D diode detector array at 0° gantry angle to determine the relative dose error for each beam. The resulting relative dose error with or without GAC was added back to the original dose grid for each beam. We compared the predicted dose distributions with or without GAC for film measurements to validate GAC effects. A gamma pass rate with a tolerance of 2%/2 mm was used to evaluate these dose distributions. The gamma pass rate with GAC was higher than that without GAC (P = 0.01). The predicted dose distribution improved with GAC, although the dosimetric effect to a patient was minimal. PMID:25742866
PARALLEL 3-D SPACE CHARGE CALCULATIONS IN THE UNIFIED ACCELERATOR LIBRARY.
D'IMPERIO, N.L.; LUCCIO, A.U.; MALITSKY, N.
2006-06-26
The paper presents the integration of the SIMBAD space charge module in the UAL framework. SIMBAD is a Particle-in-Cell (PIC) code. Its 3-D Parallel approach features an optimized load balancing scheme based on a genetic algorithm. The UAL framework enhances the SIMBAD standalone version with the interactive ROOT-based analysis environment and an open catalog of accelerator algorithms. The composite package addresses complex high intensity beam dynamics and has been developed as part of the FAIR SIS 100 project.
Use of Fluka to Create Dose Calculations
NASA Technical Reports Server (NTRS)
Lee, Kerry T.; Barzilla, Janet; Townsend, Lawrence; Brittingham, John
2012-01-01
Monte Carlo codes provide an effective means of modeling three dimensional radiation transport; however, their use is both time- and resource-intensive. The creation of a lookup table or parameterization from Monte Carlo simulation allows users to perform calculations with Monte Carlo results without replicating lengthy calculations. FLUKA Monte Carlo transport code was used to develop lookup tables and parameterizations for data resulting from the penetration of layers of aluminum, polyethylene, and water with areal densities ranging from 0 to 100 g/cm^2. Heavy charged ion radiation including ions from Z=1 to Z=26 and from 0.1 to 10 GeV/nucleon were simulated. Dose, dose equivalent, and fluence as a function of particle identity, energy, and scattering angle were examined at various depths. Calculations were compared against well-known results and against the results of other deterministic and Monte Carlo codes. Results will be presented.
3D global estimation and augmented reality visualization of intra-operative X-ray dose.
Rodas, Nicolas Loy; Padoy, Nicolas
2014-01-01
The growing use of image-guided minimally-invasive surgical procedures is confronting clinicians and surgical staff with new radiation exposure risks from X-ray imaging devices. The accurate estimation of intra-operative radiation exposure can increase staff awareness of radiation exposure risks and enable the implementation of well-adapted safety measures. The current surgical practice of wearing a single dosimeter at chest level to measure radiation exposure does not provide a sufficiently accurate estimation of radiation absorption throughout the body. In this paper, we propose an approach that combines data from wireless dosimeters with the simulation of radiation propagation in order to provide a global radiation risk map in the area near the X-ray device. We use a multi-camera RGBD system to obtain a 3D point cloud reconstruction of the room. The positions of the table, C-arm and clinician are then used 1) to simulate the propagation of radiation in a real-world setup and 2) to overlay the resulting 3D risk-map onto the scene in an augmented reality manner. By using real-time wireless dosimeters in our system, we can both calibrate the simulation and validate its accuracy at specific locations in real-time. We demonstrate our system in an operating room equipped with a robotised X-ray imaging device and validate the radiation simulation on several X-ray acquisition setups. PMID:25333145
NASA Astrophysics Data System (ADS)
Park, Hye-Suk; Kim, Ye-Seul; Lee, Haeng-Hwa; Gang, Won-Suk; Kim, Hee-Joung; Choi, Young-Wook; Choi, JaeGu
2015-08-01
The purpose of this study is to determine the optimal non-uniform angular dose distribution to improve the quality of the 3D reconstructed images and to acquire extra 2D projection images. In this analysis, 7 acquisition sets were generated by using four different values for the number of projections (11, 15, 21, and 29) and total angular range (±14°, ±17.5°, ±21°, and ±24.5° ). For all acquisition sets, the zero-degree projection was used as the 2D image that was close to that of standard conventional mammography (CM). Exposures used were 50, 100, 150, and 200 mR for the zero-degree projection, and the remaining dose was distributed over the remaining projection angles. To quantitatively evaluate image quality, we computed the CNR (contrast-to-noise ratio) and the ASF (artifact spread function) for the same radiation dose. The results indicate that, for microcalcifications, acquisition sets with approximately 4 times higher exposure on the zero-degree projection than the average exposure for the remaining projection angles yielded higher CNR values and were 3% higher than the uniform distribution. However, very high dose concentrations toward the zero-degree projection may reduce the quality of the reconstructed images due to increasing noise in the peripheral views. The zero-degree projection of the non-uniform dose distribution offers a 2D image similar to that of standard CM, but with a significantly lower radiation dose. Therefore, we need to evaluate the diagnostic potential of extra 2D projection image when diagnose breast cancer by using 3D images with non-uniform angular dose distributions.
Attili, A; Vignati, A; Giordanengo, S; Kraan, A; Dalmasso, F; Battistoni, G
2015-06-15
Purpose: Ion beam therapy is sensitive to uncertainties from treatment planning and dose delivery. PET imaging of induced positron emitter distributions is a practical approach for in vivo, in situ verification of ion beam treatments. Treatment verification is usually done by comparing measured activity distributions with reference distributions, evaluated in nominal conditions. Although such comparisons give valuable information on treatment quality, a proper clinical evaluation of the treatment ultimately relies on the knowledge of the actual delivered dose. Analytical deconvolution methods relating activity and dose have been studied in this context, but were not clinically applied. In this work we present a feasibility study of an alternative approach for dose reconstruction from activity data, which is based on relating variations in accumulated activity to tissue density variations. Methods: First, reference distributions of dose and activity were calculated from the treatment plan and CT data. Then, the actual measured activity data were cumulatively matched with the reference activity distributions to obtain a set of activity-equivalent path lengths (AEPLs) along the rays of the pencil beams. Finally, these AEPLs were used to deform the original dose distribution, yielding the actual delivered dose. The method was tested by simulating a proton therapy treatment plan delivering 2 Gy on a homogeneous water phantom (the reference), which was compared with the same plan delivered on a phantom containing inhomogeneities. Activity and dose distributions were were calculated by means of the FLUKA Monte Carlo toolkit. Results: The main features of the observed dose distribution in the inhomogeneous situation were reproduced using the AEPL approach. Variations in particle range were reproduced and the positions, where these deviations originated, were properly identified. Conclusions: For a simple inhomogeneous phantom the 3D dose reconstruction from PET
Lee, Larissa J.; Sadow, Cheryl A.; Russell, Anthony; Viswanathan, Akila N.
2009-11-01
Purpose: To compare high dose rate (HDR) point B to pelvic lymph node dose using three-dimensional-planned brachytherapy for cervical cancer. Methods and Materials: Patients with FIGO Stage IB-IIIB cervical cancer received 70 tandem HDR applications using CT-based treatment planning. The obturator, external, and internal iliac lymph nodes (LN) were contoured. Per fraction (PF) and combined fraction (CF) right (R), left (L), and bilateral (Bil) nodal doses were analyzed. Point B dose was compared with LN dose-volume histogram (DVH) parameters by paired t test and Pearson correlation coefficients. Results: Mean PF and CF doses to point B were R 1.40 Gy +- 0.14 (CF: 7 Gy), L 1.43 +- 0.15 (CF: 7.15 Gy), and Bil 1.41 +- 0.15 (CF: 7.05 Gy). The correlation coefficients between point B and the D100, D90, D50, D2cc, D1cc, and D0.1cc LN were all less than 0.7. Only the D2cc to the obturator and the D0.1cc to the external iliac nodes were not significantly different from the point B dose. Significant differences between R and L nodal DVHs were seen, likely related to tandem deviation from irregular tumor anatomy. Conclusions: With HDR brachytherapy for cervical cancer, per fraction nodal dose approximates a dose equivalent to teletherapy. Point B is a poor surrogate for dose to specific nodal groups. Three-dimensional defined nodal contours during brachytherapy provide a more accurate reflection of delivered dose and should be part of comprehensive planning of the total dose to the pelvic nodes, particularly when there is evidence of pathologic involvement.
MESA 3-D calculations of armor penetration by projectiles with combined obliquity and yaw
Cagliostro, D.J.; Mandell, D.A.; Schwalbe, L.A.; Adams, T.F.; Chapyak, E.J. )
1989-01-01
We introduce and briefly describe MESA, a new 3-D hydrodynamic code, developed specifically for simulations of armor and anti-armor systems. The code's current capabilities an its planned model improvements and additions are discussed. An Eulerian code using state-of-the-art numerical methods, MESA runs faster and is less affected by spurious numerical diffusion than older codes. It models hydrodynamic flow and the dynamic deformation of solid materials. It uses simple elastic-perfectly plastic material strength models as well as models with strain and strainrate hardening and thermal softening. Future versions will incorporate advanced fracture models. It treats detonations in explosives using a programmed burn. The code's current capabilities are illustrated with simulations of experiments on yawed rods obliquely impacting armor plates at 1.29 km/s. 12 refs., 14 figs.
Johnson, Timothy D; Taylor, Jeremy M G; Ten Haken, Randall K; Eisbruch, Avraham
2005-10-01
A goal of cancer radiation therapy is to deliver maximum dose to the target tumor while minimizing complications due to irradiation of critical organs. Technological advances in 3D conformal radiation therapy has allowed great strides in realizing this goal; however, complications may still arise. Critical organs may be adjacent to tumors or in the path of the radiation beam. Several mathematical models have been proposed that describe the relationship between dose and observed functional complication; however, only a few published studies have successfully fit these models to data using modern statistical methods which make efficient use of the data. One complication following radiation therapy of head and neck cancers is the patient's inability to produce saliva. Xerostomia (dry mouth) leads to high susceptibility to oral infection and dental caries and is, in general, unpleasant and an annoyance. We present a dose-damage-injury model that subsumes any of the various mathematical models relating dose to damage. The model is a nonlinear, longitudinal mixed effects model where the outcome (saliva flow rate) is modeled as a mixture of a Dirac measure at zero and a gamma distribution whose mean is a function of time and dose. Bayesian methods are used to estimate the relationship between dose delivered to the parotid glands and the observational outcome-saliva flow rate. A summary measure of the dose-damage relationship is modeled and assessed by a Bayesian chi(2) test for goodness-of-fit. PMID:15917377
A convolution-superposition dose calculation engine for GPUs
Hissoiny, Sami; Ozell, Benoit; Despres, Philippe
2010-03-15
Purpose: Graphic processing units (GPUs) are increasingly used for scientific applications, where their parallel architecture and unprecedented computing power density can be exploited to accelerate calculations. In this paper, a new GPU implementation of a convolution/superposition (CS) algorithm is presented. Methods: This new GPU implementation has been designed from the ground-up to use the graphics card's strengths and to avoid its weaknesses. The CS GPU algorithm takes into account beam hardening, off-axis softening, kernel tilting, and relies heavily on raytracing through patient imaging data. Implementation details are reported as well as a multi-GPU solution. Results: An overall single-GPU acceleration factor of 908x was achieved when compared to a nonoptimized version of the CS algorithm implemented in PlanUNC in single threaded central processing unit (CPU) mode, resulting in approximatively 2.8 s per beam for a 3D dose computation on a 0.4 cm grid. A comparison to an established commercial system leads to an acceleration factor of approximately 29x or 0.58 versus 16.6 s per beam in single threaded mode. An acceleration factor of 46x has been obtained for the total energy released per mass (TERMA) calculation and a 943x acceleration factor for the CS calculation compared to PlanUNC. Dose distributions also have been obtained for a simple water-lung phantom to verify that the implementation gives accurate results. Conclusions: These results suggest that GPUs are an attractive solution for radiation therapy applications and that careful design, taking the GPU architecture into account, is critical in obtaining significant acceleration factors. These results potentially can have a significant impact on complex dose delivery techniques requiring intensive dose calculations such as intensity-modulated radiation therapy (IMRT) and arc therapy. They also are relevant for adaptive radiation therapy where dose results must be obtained rapidly.
NASA Astrophysics Data System (ADS)
Wang, Haijun; Xu, Feiyun; Zhao, Jun'ai; Jia, Minping; Hu, Jianzhong; Huang, Peng
2013-11-01
Nonnegative Tucker3 decomposition(NTD) has attracted lots of attentions for its good performance in 3D data array analysis. However, further research is still necessary to solve the problems of overfitting and slow convergence under the anharmonic vibration circumstance occurred in the field of mechanical fault diagnosis. To decompose a large-scale tensor and extract available bispectrum feature, a method of conjugating Choi-Williams kernel function with Gauss-Newton Cartesian product based on nonnegative Tucker3 decomposition(NTD_EDF) is investigated. The complexity of the proposed method is reduced from o( n N lg n) in 3D spaces to o( R 1 R 2 nlg n) in 1D vectors due to its low rank form of the Tucker-product convolution. Meanwhile, a simultaneously updating algorithm is given to overcome the overfitting, slow convergence and low efficiency existing in the conventional one-by-one updating algorithm. Furthermore, the technique of spectral phase analysis for quadratic coupling estimation is used to explain the feature spectrum extracted from the gearbox fault data by the proposed method in detail. The simulated and experimental results show that the sparser and more inerratic feature distribution of basis images can be obtained with core tensor by the NTD_EDF method compared with the one by the other methods in bispectrum feature extraction, and a legible fault expression can also be performed by power spectral density(PSD) function. Besides, the deviations of successive relative error(DSRE) of NTD_EDF achieves 81.66 dB against 15.17 dB by beta-divergences based on NTD(NTD_Beta) and the time-cost of NTD_EDF is only 129.3 s, which is far less than 1 747.9 s by hierarchical alternative least square based on NTD (NTD_HALS). The NTD_EDF method proposed not only avoids the data overfitting and improves the computation efficiency but also can be used to extract more inerratic and sparser bispectrum features of the gearbox fault.
Momennezhad, Mehdi; Nasseri, Shahrokh; Zakavi, Seyed Rasoul; Parach, Ali Asghar; Ghorbani, Mahdi; Asl, Ruhollah Ghahraman
2016-01-01
Single-photon emission computed tomography (SPECT)-based tracers are easily available and more widely used than positron emission tomography (PET)-based tracers, and SPECT imaging still remains the most prevalent nuclear medicine imaging modality worldwide. The aim of this study is to implement an image-based Monte Carlo method for patient-specific three-dimensional (3D) absorbed dose calculation in patients after injection of (99m)Tc-hydrazinonicotinamide (hynic)-Tyr(3)-octreotide as a SPECT radiotracer. (99m)Tc patient-speciﬁc S values and the absorbed doses were calculated with GATE code for each source-target organ pair in four patients who were imaged for suspected neuroendocrine tumors. Each patient underwent multiple whole-body planar scans as well as SPECT imaging over a period of 1-24 h after intravenous injection of (99m)hynic-Tyr(3)-octreotide. The patient-specific S values calculated by GATE Monte Carlo code and the corresponding S values obtained by MIRDOSE program differed within 4.3% on an average for self-irradiation, and differed within 69.6% on an average for cross-irradiation. However, the agreement between total organ doses calculated by GATE code and MIRDOSE program for all patients was reasonably well (percentage difference was about 4.6% on an average). Normal and tumor absorbed doses calculated with GATE were slightly higher than those calculated with MIRDOSE program. The average ratio of GATE absorbed doses to MIRDOSE was 1.07 ± 0.11 (ranging from 0.94 to 1.36). According to the results, it is proposed that when cross-organ irradiation is dominant, a comprehensive approach such as GATE Monte Carlo dosimetry be used since it provides more reliable dosimetric results.
Momennezhad, Mehdi; Nasseri, Shahrokh; Zakavi, Seyed Rasoul; Parach, Ali Asghar; Ghorbani, Mahdi; Asl, Ruhollah Ghahraman
2016-01-01
Single-photon emission computed tomography (SPECT)-based tracers are easily available and more widely used than positron emission tomography (PET)-based tracers, and SPECT imaging still remains the most prevalent nuclear medicine imaging modality worldwide. The aim of this study is to implement an image-based Monte Carlo method for patient-specific three-dimensional (3D) absorbed dose calculation in patients after injection of (99m)Tc-hydrazinonicotinamide (hynic)-Tyr(3)-octreotide as a SPECT radiotracer. (99m)Tc patient-speciﬁc S values and the absorbed doses were calculated with GATE code for each source-target organ pair in four patients who were imaged for suspected neuroendocrine tumors. Each patient underwent multiple whole-body planar scans as well as SPECT imaging over a period of 1-24 h after intravenous injection of (99m)hynic-Tyr(3)-octreotide. The patient-specific S values calculated by GATE Monte Carlo code and the corresponding S values obtained by MIRDOSE program differed within 4.3% on an average for self-irradiation, and differed within 69.6% on an average for cross-irradiation. However, the agreement between total organ doses calculated by GATE code and MIRDOSE program for all patients was reasonably well (percentage difference was about 4.6% on an average). Normal and tumor absorbed doses calculated with GATE were slightly higher than those calculated with MIRDOSE program. The average ratio of GATE absorbed doses to MIRDOSE was 1.07 ± 0.11 (ranging from 0.94 to 1.36). According to the results, it is proposed that when cross-organ irradiation is dominant, a comprehensive approach such as GATE Monte Carlo dosimetry be used since it provides more reliable dosimetric results. PMID:27134562
Momennezhad, Mehdi; Nasseri, Shahrokh; Zakavi, Seyed Rasoul; Parach, Ali Asghar; Ghorbani, Mahdi; Asl, Ruhollah Ghahraman
2016-01-01
Single-photon emission computed tomography (SPECT)-based tracers are easily available and more widely used than positron emission tomography (PET)-based tracers, and SPECT imaging still remains the most prevalent nuclear medicine imaging modality worldwide. The aim of this study is to implement an image-based Monte Carlo method for patient-specific three-dimensional (3D) absorbed dose calculation in patients after injection of 99mTc-hydrazinonicotinamide (hynic)-Tyr3-octreotide as a SPECT radiotracer. 99mTc patient-speciﬁc S values and the absorbed doses were calculated with GATE code for each source-target organ pair in four patients who were imaged for suspected neuroendocrine tumors. Each patient underwent multiple whole-body planar scans as well as SPECT imaging over a period of 1-24 h after intravenous injection of 99mhynic-Tyr3-octreotide. The patient-specific S values calculated by GATE Monte Carlo code and the corresponding S values obtained by MIRDOSE program differed within 4.3% on an average for self-irradiation, and differed within 69.6% on an average for cross-irradiation. However, the agreement between total organ doses calculated by GATE code and MIRDOSE program for all patients was reasonably well (percentage difference was about 4.6% on an average). Normal and tumor absorbed doses calculated with GATE were slightly higher than those calculated with MIRDOSE program. The average ratio of GATE absorbed doses to MIRDOSE was 1.07 ± 0.11 (ranging from 0.94 to 1.36). According to the results, it is proposed that when cross-organ irradiation is dominant, a comprehensive approach such as GATE Monte Carlo dosimetry be used since it provides more reliable dosimetric results. PMID:27134562
Calculation of Dose Deposition in Nanovolumes and Simulation of gamma-H2AX Experiments
NASA Technical Reports Server (NTRS)
Plante, Ianik
2010-01-01
Monte-Carlo track structure simulations can accurately simulate experimental data: a) Frequency of target hits. b) Dose per event. c) Dose per ion. d) Radial dose. The dose is uniform in micrometers sized voxels; at the nanometer scale, the difference in energy deposition between high and low-LET radiations appears. The calculated 3D distribution of dose voxels, combined with chromosomes simulated by random walk is very similar to the distribution of DSB observed with gamma-H2AX experiments. This is further evidenced by applying a visualization threshold on dose.
Calculation of grain boundary normals directly from 3D microstructure images
Lieberman, E. J.; Rollett, A. D.; Lebensohn, R. A.; Kober, E. M.
2015-03-11
The determination of grain boundary normals is an integral part of the characterization of grain boundaries in polycrystalline materials. These normal vectors are difficult to quantify due to the discretized nature of available microstructure characterization techniques. The most common method to determine grain boundary normals is by generating a surface mesh from an image of the microstructure, but this process can be slow, and is subject to smoothing issues. A new technique is proposed, utilizing first order Cartesian moments of binary indicator functions, to determine grain boundary normals directly from a voxelized microstructure image. In order to validate the accuracymore » of this technique, the surface normals obtained by the proposed method are compared to those generated by a surface meshing algorithm. Specifically, the local divergence between the surface normals obtained by different variants of the proposed technique and those generated from a surface mesh of a synthetic microstructure constructed using a marching cubes algorithm followed by Laplacian smoothing is quantified. Next, surface normals obtained with the proposed method from a measured 3D microstructure image of a Ni polycrystal are used to generate grain boundary character distributions (GBCD) for Σ3 and Σ9 boundaries, and compared to the GBCD generated using a surface mesh obtained from the same image. Finally, the results show that the proposed technique is an efficient and accurate method to determine voxelized fields of grain boundary normals.« less
Numerical Calculations of 3-D High-Lift Flows and Comparison with Experiment
NASA Technical Reports Server (NTRS)
Compton, William B, III
2015-01-01
Solutions were obtained with the Navier-Stokes CFD code TLNS3D to predict the flow about the NASA Trapezoidal Wing, a high-lift wing composed of three elements: the main-wing element, a deployed leading-edge slat, and a deployed trailing-edge flap. Turbulence was modeled by the Spalart-Allmaras one-equation turbulence model. One case with massive separation was repeated using Menter's two-equation SST (Menter's Shear Stress Transport) k-omega turbulence model in an attempt to improve the agreement with experiment. The investigation was conducted at a free stream Mach number of 0.2, and at angles of attack ranging from 10.004 degrees to 34.858 degrees. The Reynolds number based on the mean aerodynamic chord of the wing was 4.3 x 10 (sup 6). Compared to experiment, the numerical procedure predicted the surface pressures very well at angles of attack in the linear range of the lift. However, computed maximum lift was 5% low. Drag was mainly under predicted. The procedure correctly predicted several well-known trends and features of high-lift flows, such as off-body separation. The two turbulence models yielded significantly different solutions for the repeated case.
Calculation of grain boundary normals directly from 3D microstructure images
Lieberman, E. J.; Rollett, A. D.; Lebensohn, R. A.; Kober, E. M.
2015-03-11
The determination of grain boundary normals is an integral part of the characterization of grain boundaries in polycrystalline materials. These normal vectors are difficult to quantify due to the discretized nature of available microstructure characterization techniques. The most common method to determine grain boundary normals is by generating a surface mesh from an image of the microstructure, but this process can be slow, and is subject to smoothing issues. A new technique is proposed, utilizing first order Cartesian moments of binary indicator functions, to determine grain boundary normals directly from a voxelized microstructure image. In order to validate the accuracy of this technique, the surface normals obtained by the proposed method are compared to those generated by a surface meshing algorithm. Specifically, the local divergence between the surface normals obtained by different variants of the proposed technique and those generated from a surface mesh of a synthetic microstructure constructed using a marching cubes algorithm followed by Laplacian smoothing is quantified. Next, surface normals obtained with the proposed method from a measured 3D microstructure image of a Ni polycrystal are used to generate grain boundary character distributions (GBCD) for Σ3 and Σ9 boundaries, and compared to the GBCD generated using a surface mesh obtained from the same image. Finally, the results show that the proposed technique is an efficient and accurate method to determine voxelized fields of grain boundary normals.
Evaluation of a new commercial Monte Carlo dose calculation algorithm for electron beams
Vandervoort, Eric J. Cygler, Joanna E.; Tchistiakova, Ekaterina; La Russa, Daniel J.
2014-02-15
Purpose: In this report the authors present the validation of a Monte Carlo dose calculation algorithm (XiO EMC from Elekta Software) for electron beams. Methods: Calculated and measured dose distributions were compared for homogeneous water phantoms and for a 3D heterogeneous phantom meant to approximate the geometry of a trachea and spine. Comparisons of measurements and calculated data were performed using 2D and 3D gamma index dose comparison metrics. Results: Measured outputs agree with calculated values within estimated uncertainties for standard and extended SSDs for open applicators, and for cutouts, with the exception of the 17 MeV electron beam at extended SSD for cutout sizes smaller than 5 × 5 cm{sup 2}. Good agreement was obtained between calculated and experimental depth dose curves and dose profiles (minimum number of measurements that pass a 2%/2 mm agreement 2D gamma index criteria for any applicator or energy was 97%). Dose calculations in a heterogeneous phantom agree with radiochromic film measurements (>98% of pixels pass a 3 dimensional 3%/2 mm γ-criteria) provided that the steep dose gradient in the depth direction is considered. Conclusions: Clinically acceptable agreement (at the 2%/2 mm level) between the measurements and calculated data for measurements in water are obtained for this dose calculation algorithm. Radiochromic film is a useful tool to evaluate the accuracy of electron MC treatment planning systems in heterogeneous media.
NASA Astrophysics Data System (ADS)
Mijnheer, Ben; Mans, Anton; Olaciregui-Ruiz, Igor; Sonke, Jan-Jakob; Tielenburg, Rene; Van Herk, Marcel; Vijlbrief, Ron; Stroom, Joep
2010-11-01
A review is given of the clinical use of EPID dosimetry in the Department of Radiation Oncology of The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital. All curative plans (almost all IMRT or VMAT) are verified with EPID dosimetry, mostly in vivo. The 2D approach for IMRT verification and the 3D method for VMAT verification are elucidated and their clinical implementation described. It has been shown that EPID dosimetry plays an important role in the total chain of verification procedures that are implemented in our department. It provides a safety net for advanced treatments such as IMRT and VMAT, as well as a full account of the dose delivered.
Linearly Scaling 3D Fragment Method for Large-Scale Electronic Structure Calculations
Wang, Lin-Wang; Lee, Byounghak; Shan, Hongzhang; Zhao, Zhengji; Meza, Juan; Strohmaier, Erich; Bailey, David H.
2008-07-01
We present a new linearly scaling three-dimensional fragment (LS3DF) method for large scale ab initio electronic structure calculations. LS3DF is based on a divide-and-conquer approach, which incorporates a novel patching scheme that effectively cancels out the artificial boundary effects due to the subdivision of the system. As a consequence, the LS3DF program yields essentially the same results as direct density functional theory (DFT) calculations. The fragments of the LS3DF algorithm can be calculated separately with different groups of processors. This leads to almost perfect parallelization on tens of thousands of processors. After code optimization, we were able to achieve 35.1 Tflop/s, which is 39percent of the theoretical speed on 17,280 Cray XT4 processor cores. Our 13,824-atom ZnTeO alloy calculation runs 400 times faster than a direct DFTcalculation, even presuming that the direct DFT calculation can scale well up to 17,280 processor cores. These results demonstrate the applicability of the LS3DF method to material simulations, the advantage of using linearly scaling algorithms over conventional O(N3) methods, and the potential for petascale computation using the LS3DF method.
Extracting chemical information from plane wave calculations by a 3D 'fuzzy atoms' analysis
NASA Astrophysics Data System (ADS)
Bakó, I.; Stirling, A.; Seitsonen, A. P.; Mayer, I.
2013-03-01
Bond order and valence indices have been calculated by the method of the three-dimensional 'fuzzy atoms' analysis, using the numerical molecular orbitals obtained from plane wave DFT calculations, i.e., without introducing any external atom-centered functions. Weight functions of both Hirshfeld and Becke types have been applied. The results are rather close to the similar 'fuzzy atoms' ones obtained by using atom-centered basis sets and agree well with the chemical expectations, stressing the power of the genuine chemical concepts.
Phage therapy pharmacology: calculating phage dosing.
Abedon, Stephen
2011-01-01
Phage therapy, which can be described as a phage-mediated biocontrol of bacteria (or, simply, biocontrol), is the application of bacterial viruses-also bacteriophages or phages-to reduce densities of nuisance or pathogenic bacteria. Predictive calculations for phage therapy dosing should be useful toward rational development of therapeutic as well as biocontrol products. Here, I consider the theoretical basis of a number of concepts relevant to phage dosing for phage therapy including minimum inhibitory concentration (but also "inundation threshold"), minimum bactericidal concentration (but also "clearance threshold"), decimal reduction time (D value), time until bacterial eradication, threshold bacterial density necessary to support phage population growth ("proliferation threshold"), and bacterial density supporting half-maximal phage population growth rates (K(B)). I also address the concepts of phage killing titers, multiplicity of infection, and phage peak densities. Though many of the presented ideas are not unique to this chapter, I nonetheless provide variations on derivations and resulting formulae, plus as appropriate discuss relative importance. The overriding goal is to present a variety of calculations that are useful toward phage therapy dosing so that they may be found in one location and presented in a manner that allows facile appreciation, comparison, and implementation. The importance of phage density as a key determinant of the phage potential to eradicate bacterial targets is stressed throughout the chapter. PMID:22050820
NASA Astrophysics Data System (ADS)
McCurdy, B. M. C.
2013-06-01
An overview is provided of the use of amorphous silicon electronic portal imaging devices (EPIDs) for dosimetric purposes in radiation therapy, focusing on 3D patient dose estimation. EPIDs were originally developed to provide on-treatment radiological imaging to assist with patient setup, but there has also been a natural interest in using them as dosimeters since they use the megavoltage therapy beam to form images. The current generation of clinically available EPID technology, amorphous-silicon (a-Si) flat panel imagers, possess many characteristics that make them much better suited to dosimetric applications than earlier EPID technologies. Features such as linearity with dose/dose rate, high spatial resolution, realtime capability, minimal optical glare, and digital operation combine with the convenience of a compact, retractable detector system directly mounted on the linear accelerator to provide a system that is well-suited to dosimetric applications. This review will discuss clinically available a-Si EPID systems, highlighting dosimetric characteristics and remaining limitations. Methods for using EPIDs in dosimetry applications will be discussed. Dosimetric applications using a-Si EPIDs to estimate three-dimensional dose in the patient during treatment will be overviewed. Clinics throughout the world are implementing increasingly complex treatments such as dynamic intensity modulated radiation therapy and volumetric modulated arc therapy, as well as specialized treatment techniques using large doses per fraction and short treatment courses (ie. hypofractionation and stereotactic radiosurgery). These factors drive the continued strong interest in using EPIDs as dosimeters for patient treatment verification.
Effects of inflow distortion profiles on fan tone noise calculated using a 3-D theory
NASA Technical Reports Server (NTRS)
Kobayashi, H.; Groeneweg, J. F.
1979-01-01
Calculations of the fan tone acoustic power and modal structure generated by complex distortions in axial inflow velocity are presented. The model used treats the motor as a rotating three-dimensional cascade and calculates the acoustic field from the distortion-produced dipole distribution on the blades including noncompact source effects. Radial and circumferential distortion shapes are synthesized from Fourier-Bessel components representing individual distortion modes. The relation between individual distortion modes and the generated acoustic modes is examined for particular distortion cases. Comparisons between theoretical and experimental results for distortions produced by wakes from upstream radial rods show that the analysis is a good predictor of acoustic power dependence on disturbance strength.
Kim, Yongbok; Modrick, Joseph M; Pennington, Edward C; Kim, Yusung
2016-01-01
The objective of this work is to present commissioning procedures to clinically implement a three-dimensional (3D), image-based, treatment-planning system (TPS) for high-dose-rate (HDR) brachytherapy (BT) for gynecological (GYN) cancer. The physical dimensions of the GYN applicators and their values in the virtual applicator library were varied by 0.4 mm of their nominal values. Reconstruction uncertainties of the titanium tandem and ovoids (T&O) were less than 0.4 mm on CT phantom studies and on average between 0.8-1.0 mm on MRI when compared with X-rays. In-house software, HDRCalculator, was developed to check HDR plan parameters such as independently verifying active tandem or cylinder probe length and ovoid or cylinder size, source calibration and treatment date, and differences between average Point A dose and prescription dose. Dose-volume histograms were validated using another independent TPS. Comprehensive procedures to commission volume optimization algorithms and process in 3D image-based planning were presented. For the difference between line and volume optimizations, the average absolute differences as a percentage were 1.4% for total reference air KERMA (TRAK) and 1.1% for Point A dose. Volume optimization consistency tests between versions resulted in average absolute differences in 0.2% for TRAK and 0.9 s (0.2%) for total treatment time. The data revealed that the optimizer should run for at least 1 min in order to avoid more than 0.6% dwell time changes. For clinical GYN T&O cases, three different volume optimization techniques (graphical optimization, pure inverse planning, and hybrid inverse optimization) were investigated by comparing them against a conventional Point A technique. End-to-end testing was performed using a T&O phantom to ensure no errors or inconsistencies occurred from imaging through to planning and delivery. The proposed commissioning procedures provide a clinically safe implementation technique for 3D image-based TPS for HDR
Calculations of separated 3-D flows with a pressure-staggered Navier-Stokes equations solver
NASA Technical Reports Server (NTRS)
Kim, S.-W.
1991-01-01
A Navier-Stokes equations solver based on a pressure correction method with a pressure-staggered mesh and calculations of separated three-dimensional flows are presented. It is shown that the velocity pressure decoupling, which occurs when various pressure correction algorithms are used for pressure-staggered meshes, is caused by the ill-conditioned discrete pressure correction equation. The use of a partial differential equation for the incremental pressure eliminates the velocity pressure decoupling mechanism by itself and yields accurate numerical results. Example flows considered are a three-dimensional lid driven cavity flow and a laminar flow through a 90 degree bend square duct. For the lid driven cavity flow, the present numerical results compare more favorably with the measured data than those obtained using a formally third order accurate quadratic upwind interpolation scheme. For the curved duct flow, the present numerical method yields a grid independent solution with a very small number of grid points. The calculated velocity profiles are in good agreement with the measured data.
Aorta cross-section calculation and 3D visualization from CT or MRT data using VRML
NASA Astrophysics Data System (ADS)
Grabner, Guenther; Modritsch, Robert; Stiegmaier, Wolfgang; Grasser, Simon; Klinger, Thomas
2005-04-01
Quantification of vessel diameters of artherosclerotic or congenital stenosis is very important for the diagnosis of vascular diseases. The aorta extraction and cross-section calculation is a software-based application that offers a three-dimensional, platform-independent, colorized visualization of the extracted aorta with augmented reality information of MRT or CT datasets. This project is based on different types of specialized image processing algorithms, dynamical particle filtering and complex mathematical equations. From this three-dimensional model a calculation of minimal cross sections is performed. In user specified distances, the aorta is cut in differently defined directions which are created through vectors with varying length. The extracted aorta and the derived minimal cross-sections are then rendered with the marching cube algorithm and represented together in a three-dimensional virtual reality with a very high degree of immersion. The aim of this study was to develop an imaging software that delivers cardiologists the possibility of (i) furnishing fast vascular diagnosis, (ii) getting precise diameter information, (iii) being able to process exact, local stenosis detection (iv) having permanent data storing and easy access to former datasets, and (v) reliable documentation of results in form of tables and graphical printouts.
Bree, Ingrid de; van Hinsberg, Mariëlle G E; van Veelen, Lieneke R
2012-01-01
Conformal 3D radiotherapy (3D-CRT) combined with chemotherapy for inoperable non-small cell lung cancer (NSCLC) to the preferable high dose is often not achievable because of dose-limiting organs. This reduces the probability of regional tumor control. Therefore, the surplus value of using intensity-modulated radiation therapy (IMRT) techniques, specifically volumetric modulated arc therapy (RapidArc [RA]) and dynamic IMRT (d-IMRT) has been investigated. RA and d-IMRT plans were compared with 3D-CRT treatment plans for 20 patients eligible for concurrent high-dose chemoradiotherapy, in whom a dose of 60 Gy was not achievable. Comparison of dose delivery in the target volume and organs at risk was carried out by evaluating 3D dose distributions and dose-volume histograms. Quality of the dose distribution was assessed using the inhomogeneity and conformity index. For most patients, a higher dose to the target volume can be delivered using RA or d-IMRT; in 15% of the patients a dose ≥60 Gy was possible. Both IMRT techniques result in a better conformity of the dose (p < 0.001). There are no significant differences in homogeneity of dose in the target volume. IMRT techniques for NSCLC patients allow higher dose to the target volume, thus improving regional tumor control. PMID:22459649
Johnson, M.W.
1990-01-01
A comparison of electron densities calculated from the Utah State University First-Principals Ionospheric Model with simultaneous observations taken at Sondrestrom, Millstone, and Arecibo incoherent-scatter radars was undertaken to better understanding the response of the ionosphere at these longitudinally similar yet latitudinally separated locations. The comparison included over 50 days distributed over 3 1/2 years roughly symmetrical about the last solar-minimum in 1986. The overall trend of the comparison was that to first-order the model reproduces electron densities responding to diurnal, seasonal, geomagnetic, and solar-cycle variations for all three radars. However, some model-observation discrepancies were found. These include, failure of the model to correctly produce an evening peak at Millstone, fall-spring equinox differences at Sondrestrom, tidal structure at Arecibo, and daytime NmF2 values at Arecibo.
Implementation of Hamada principle in calculations of nested 3-D equilibria
NASA Astrophysics Data System (ADS)
Zakharov, Leonid E.
2015-12-01
> Plasma confinement is based on the use of nested toroidal magnetic surfaces. In axisymmetric configurations the nestedness is provided by the existence of a flux function describing the magnetic surfaces explicitly. In the case of a three-dimensional magnetic field, the nested surfaces represent an exception. More typically, magnetic islands are formed on the resonant surfaces. The islands could degrade the plasma performance. The rigorous condition for the existence of nested surfaces without islands was formulated by Hamada (Nucl. Fusion, vol. 2, 1962, pp. 23-37) but was not implemented directly into numerical codes used, for example, for designing the stellarator configurations. This paper introduces a method of implementation of the Hamada principle in numerical algorithms. The proposed approach allows for simple linearized equilibrium equations (LEE) and potentially very efficient three-dimensional calculations of nested equilibria.
3D field calculation of the GEM prototype magnet and comparison with measurements
Lari, R.J.
1983-10-28
The proposed 4 GeV Electron Microtron (GEM) is designed to fill the existing buildings left vacant by the demise of the Zero Gradient Synchrotron (ZGS) accelerator. One of the six large dipole magnets is shown as well as the first 10 electron orbits. A 3-orbit prototype magnet has been built. The stepped edge of the magnet is to keep the beam exiting perpendicular to the pole. The end guards that wrap around the main coils are joined together by the 3 shield plates. The auxiliary coils are needed to keep the end guards and shield plates from saturating. A 0.3 cm Purcell filter air gap exists between the pole and the yoke. Can anyone question this being a truly three-dimensional magnetostatic problem. The computer program TOSCA, developed at the Rutherford Appleton Laboratory by the Computing Applications Group, was used to calculate this magnet and the results have been compared with measurements.
Applicability of 3D Monte Carlo simulations for local values calculations in a PWR core
NASA Astrophysics Data System (ADS)
Bernard, Franck; Cochet, Bertrand; Jinaphanh, Alexis; Jacquet, Olivier
2014-06-01
As technical support of the French Nuclear Safety Authority, IRSN has been developing the MORET Monte Carlo code for many years in the framework of criticality safety assessment and is now working to extend its application to reactor physics. For that purpose, beside the validation for criticality safety (more than 2000 benchmarks from the ICSBEP Handbook have been modeled and analyzed), a complementary validation phase for reactor physics has been started, with benchmarks from IRPHEP Handbook and others. In particular, to evaluate the applicability of MORET and other Monte Carlo codes for local flux or power density calculations in large power reactors, it has been decided to contribute to the "Monte Carlo Performance Benchmark" (hosted by OECD/NEA). The aim of this benchmark is to monitor, in forthcoming decades, the performance progress of detailed Monte Carlo full core calculations. More precisely, it measures their advancement towards achieving high statistical accuracy in reasonable computation time for local power at fuel pellet level. A full PWR reactor core is modeled to compute local power densities for more than 6 million fuel regions. This paper presents results obtained at IRSN for this benchmark with MORET and comparisons with MCNP. The number of fuel elements is so large that source convergence as well as statistical convergence issues could cause large errors in local tallies, especially in peripheral zones. Various sampling or tracking methods have been implemented in MORET, and their operational effects on such a complex case have been studied. Beyond convergence issues, to compute local values in so many fuel regions could cause prohibitive slowing down of neutron tracking. To avoid this, energy grid unification and tallies preparation before tracking have been implemented, tested and proved to be successful. In this particular case, IRSN obtained promising results with MORET compared to MCNP, in terms of local power densities, standard
Sofronov, I.D.; Voronin, B.L.; Butnev, O.I.
1997-12-31
The aim of the work performed is to develop a 3D parallel program for numerical calculation of gas dynamics problem with heat conductivity on distributed memory computational systems (CS), satisfying the condition of numerical result independence from the number of processors involved. Two basically different approaches to the structure of massive parallel computations have been developed. The first approach uses the 3D data matrix decomposition reconstructed at temporal cycle and is a development of parallelization algorithms for multiprocessor CS with shareable memory. The second approach is based on using a 3D data matrix decomposition not reconstructed during a temporal cycle. The program was developed on 8-processor CS MP-3 made in VNIIEF and was adapted to a massive parallel CS Meiko-2 in LLNL by joint efforts of VNIIEF and LLNL staffs. A large number of numerical experiments has been carried out with different number of processors up to 256 and the efficiency of parallelization has been evaluated in dependence on processor number and their parameters.
Wang, Lichun; Cardenas, M Bayani
2015-08-01
The quantitative study of transport through fractured media has continued for many decades, but has often been constrained by observational and computational challenges. Here, we developed an efficient quasi-3D random walk particle tracking (RWPT) algorithm to simulate solute transport through natural fractures based on a 2D flow field generated from the modified local cubic law (MLCL). As a reference, we also modeled the actual breakthrough curves (BTCs) through direct simulations with the 3D advection-diffusion equation (ADE) and Navier-Stokes equations. The RWPT algorithm along with the MLCL accurately reproduced the actual BTCs calculated with the 3D ADE. The BTCs exhibited non-Fickian behavior, including early arrival and long tails. Using the spatial information of particle trajectories, we further analyzed the dynamic dispersion process through moment analysis. From this, asymptotic time scales were determined for solute dispersion to distinguish non-Fickian from Fickian regimes. This analysis illustrates the advantage and benefit of using an efficient combination of flow modeling and RWPT. PMID:26042625
Software for 3D radiotherapy dosimetry. Validation
NASA Astrophysics Data System (ADS)
Kozicki, Marek; Maras, Piotr; Karwowski, Andrzej C.
2014-08-01
The subject of this work is polyGeVero® software (GeVero Co., Poland), which has been developed to fill the requirements of fast calculations of 3D dosimetry data with the emphasis on polymer gel dosimetry for radiotherapy. This software comprises four workspaces that have been prepared for: (i) calculating calibration curves and calibration equations, (ii) storing the calibration characteristics of the 3D dosimeters, (iii) calculating 3D dose distributions in irradiated 3D dosimeters, and (iv) comparing 3D dose distributions obtained from measurements with the aid of 3D dosimeters and calculated with the aid of treatment planning systems (TPSs). The main features and functions of the software are described in this work. Moreover, the core algorithms were validated and the results are presented. The validation was performed using the data of the new PABIGnx polymer gel dosimeter. The polyGeVero® software simplifies and greatly accelerates the calculations of raw 3D dosimetry data. It is an effective tool for fast verification of TPS-generated plans for tumor irradiation when combined with a 3D dosimeter. Consequently, the software may facilitate calculations by the 3D dosimetry community. In this work, the calibration characteristics of the PABIGnx obtained through four calibration methods: multi vial, cross beam, depth dose, and brachytherapy, are discussed as well.
The linearly scaling 3D fragment method for large scale electronic structure calculations
Zhao, Zhengji; Meza, Juan; Lee, Byounghak; Shan, Hongzhang; Strohmaier, Erich; Bailey, David; Wang, Lin-Wang
2009-07-28
The Linearly Scaling three-dimensional fragment (LS3DF) method is an O(N) ab initio electronic structure method for large-scale nano material simulations. It is a divide-and-conquer approach with a novel patching scheme that effectively cancels out the artificial boundary effects, which exist in all divide-and-conquer schemes. This method has made ab initio simulations of thousand-atom nanosystems feasible in a couple of hours, while retaining essentially the same accuracy as the direct calculation methods. The LS3DF method won the 2008 ACM Gordon Bell Prize for algorithm innovation. Our code has reached 442 Tflop/s running on 147,456 processors on the Cray XT5 (Jaguar) at OLCF, and has been run on 163,840 processors on the Blue Gene/P (Intrepid) at ALCF, and has been applied to a system containing 36,000 atoms. In this paper, we will present the recent parallel performance results of this code, and will apply the method to asymmetric CdSe/CdS core/shell nanorods, which have potential applications in electronic devices and solar cells.
The Linearly Scaling 3D Fragment Method for Large Scale Electronic Structure Calculations
Zhao, Zhengji; Meza, Juan; Lee, Byounghak; Shan, Hongzhang; Strohmaier, Erich; Bailey, David; Wang, Lin-Wang
2009-06-26
The Linearly Scaling three-dimensional fragment (LS3DF) method is an O(N) ab initio electronic structure method for large-scale nano material simulations. It is a divide-and-conquer approach with a novel patching scheme that effectively cancels out the artificial boundary effects, which exist in all divide-and-conquer schemes. This method has made ab initio simulations of thousand-atom nanosystems feasible in a couple of hours, while retaining essentially the same accuracy as the direct calculation methods. The LS3DF method won the 2008 ACM Gordon Bell Prize for algorithm innovation. Our code has reached 442 Tflop/s running on 147,456 processors on the Cray XT5 (Jaguar) at OLCF, and has been run on 163,840 processors on the Blue Gene/P (Intrepid) at ALCF, and has been applied to a system containing 36,000 atoms. In this paper, we will present the recent parallel performance results of this code, and will apply the method to asymmetric CdSe/CdS core/shell nanorods, which have potential applications in electronic devices and solar cells.
The linearly scaling 3D fragment method for large scale electronic structure calculations
NASA Astrophysics Data System (ADS)
Zhao, Zhengji; Meza, Juan; Lee, Byounghak; Shan, Hongzhang; Strohmaier, Erich; Bailey, David; Wang, Lin-Wang
2009-07-01
The linearly scaling three-dimensional fragment (LS3DF) method is an O(N) ab initio electronic structure method for large-scale nano material simulations. It is a divide-and-conquer approach with a novel patching scheme that effectively cancels out the artificial boundary effects, which exist in all divide-and-conquer schemes. This method has made ab initio simulations of thousand-atom nanosystems feasible in a couple of hours, while retaining essentially the same accuracy as the direct calculation methods. The LS3DF method won the 2008 ACM Gordon Bell Prize for algorithm innovation. Our code has reached 442 Tflop/s running on 147,456 processors on the Cray XT5 (Jaguar) at OLCF, and has been run on 163,840 processors on the Blue Gene/P (Intrepid) at ALCF, and has been applied to a system containing 36,000 atoms. In this paper, we will present the recent parallel performance results of this code, and will apply the method to asymmetric CdSe/CdS core/shell nanorods, which have potential applications in electronic devices and solar cells.
The Calculation of the Band Structure in 3D Phononic Crystal with Hexagonal Lattice
NASA Astrophysics Data System (ADS)
Aryadoust, Mahrokh; Salehi, H.
2015-12-01
In this article, the propagation of acoustic waves in the phononic crystals (PCs) of three dimensions with the hexagonal (HEX) lattice is studied theoretically. The PCs are constituted of nickel (Ni) spheres embedded in epoxy. The calculations of the band structure and the density of states are performed using the plane wave expansion (PWE) method in the irreducible part of the Brillouin zone (BZ). In this study, we analyse the dependence of the band structures inside (the complete band gap width) on c/a and filling fraction in the irreducible part of the first BZ. Also, we have analysed the band structure of the ALHA and MLHKM planes. The results show that the maximum width of absolute elastic band gap (AEBG) (0.045) in the irreducible part of the BZ of HEX lattice is formed for c/a=6 and filling fraction equal to 0.01. In addition, the maximum of the first and second AEBG widths are 0.0884 and 0.0474, respectively, in the MLHKM plane, and the maximum of the first and second AEBG widths are 0.0851 and 0.0431, respectively, in the ALHA plane.
Visser, R; Godart, J; Wauben, D J L; Langendijk, J A; Van't Veld, A A; Korevaar, E W
2016-05-21
The objective of this study was to introduce a new iterative method to reconstruct multi leaf collimator (MLC) positions based on low resolution ionization detector array measurements and to evaluate its error detection performance. The iterative reconstruction method consists of a fluence model, a detector model and an optimizer. Expected detector response was calculated using a radiotherapy treatment plan in combination with the fluence model and detector model. MLC leaf positions were reconstructed by minimizing differences between expected and measured detector response. The iterative reconstruction method was evaluated for an Elekta SLi with 10.0 mm MLC leafs in combination with the COMPASS system and the MatriXX Evolution (IBA Dosimetry) detector with a spacing of 7.62 mm. The detector was positioned in such a way that each leaf pair of the MLC was aligned with one row of ionization chambers. Known leaf displacements were introduced in various field geometries ranging from -10.0 mm to 10.0 mm. Error detection performance was tested for MLC leaf position dependency relative to the detector position, gantry angle dependency, monitor unit dependency, and for ten clinical intensity modulated radiotherapy (IMRT) treatment beams. For one clinical head and neck IMRT treatment beam, influence of the iterative reconstruction method on existing 3D dose reconstruction artifacts was evaluated. The described iterative reconstruction method was capable of individual MLC leaf position reconstruction with millimeter accuracy, independent of the relative detector position within the range of clinically applied MU's for IMRT. Dose reconstruction artifacts in a clinical IMRT treatment beam were considerably reduced as compared to the current dose verification procedure. The iterative reconstruction method allows high accuracy 3D dose verification by including actual MLC leaf positions reconstructed from low resolution 2D measurements. PMID:27100169
NASA Astrophysics Data System (ADS)
Visser, R.; Godart, J.; Wauben, D. J. L.; Langendijk, J. A.; van't Veld, A. A.; Korevaar, E. W.
2016-05-01
The objective of this study was to introduce a new iterative method to reconstruct multi leaf collimator (MLC) positions based on low resolution ionization detector array measurements and to evaluate its error detection performance. The iterative reconstruction method consists of a fluence model, a detector model and an optimizer. Expected detector response was calculated using a radiotherapy treatment plan in combination with the fluence model and detector model. MLC leaf positions were reconstructed by minimizing differences between expected and measured detector response. The iterative reconstruction method was evaluated for an Elekta SLi with 10.0 mm MLC leafs in combination with the COMPASS system and the MatriXX Evolution (IBA Dosimetry) detector with a spacing of 7.62 mm. The detector was positioned in such a way that each leaf pair of the MLC was aligned with one row of ionization chambers. Known leaf displacements were introduced in various field geometries ranging from -10.0 mm to 10.0 mm. Error detection performance was tested for MLC leaf position dependency relative to the detector position, gantry angle dependency, monitor unit dependency, and for ten clinical intensity modulated radiotherapy (IMRT) treatment beams. For one clinical head and neck IMRT treatment beam, influence of the iterative reconstruction method on existing 3D dose reconstruction artifacts was evaluated. The described iterative reconstruction method was capable of individual MLC leaf position reconstruction with millimeter accuracy, independent of the relative detector position within the range of clinically applied MU’s for IMRT. Dose reconstruction artifacts in a clinical IMRT treatment beam were considerably reduced as compared to the current dose verification procedure. The iterative reconstruction method allows high accuracy 3D dose verification by including actual MLC leaf positions reconstructed from low resolution 2D measurements.
NASA Astrophysics Data System (ADS)
Visser, R.; Godart, J.; Wauben, D. J. L.; Langendijk, J. A.; van’t Veld, A. A.; Korevaar, E. W.
2016-05-01
The objective of this study was to introduce a new iterative method to reconstruct multi leaf collimator (MLC) positions based on low resolution ionization detector array measurements and to evaluate its error detection performance. The iterative reconstruction method consists of a fluence model, a detector model and an optimizer. Expected detector response was calculated using a radiotherapy treatment plan in combination with the fluence model and detector model. MLC leaf positions were reconstructed by minimizing differences between expected and measured detector response. The iterative reconstruction method was evaluated for an Elekta SLi with 10.0 mm MLC leafs in combination with the COMPASS system and the MatriXX Evolution (IBA Dosimetry) detector with a spacing of 7.62 mm. The detector was positioned in such a way that each leaf pair of the MLC was aligned with one row of ionization chambers. Known leaf displacements were introduced in various field geometries ranging from ‑10.0 mm to 10.0 mm. Error detection performance was tested for MLC leaf position dependency relative to the detector position, gantry angle dependency, monitor unit dependency, and for ten clinical intensity modulated radiotherapy (IMRT) treatment beams. For one clinical head and neck IMRT treatment beam, influence of the iterative reconstruction method on existing 3D dose reconstruction artifacts was evaluated. The described iterative reconstruction method was capable of individual MLC leaf position reconstruction with millimeter accuracy, independent of the relative detector position within the range of clinically applied MU’s for IMRT. Dose reconstruction artifacts in a clinical IMRT treatment beam were considerably reduced as compared to the current dose verification procedure. The iterative reconstruction method allows high accuracy 3D dose verification by including actual MLC leaf positions reconstructed from low resolution 2D measurements.
Travel time calculation in regular 3D grid in local and regional scale using fast marching method
NASA Astrophysics Data System (ADS)
Polkowski, M.
2015-12-01
Local and regional 3D seismic velocity models of crust and sediments are very important for numerous technics like mantle and core tomography, localization of local and regional events and others. Most of those techniques require calculation of wave travel time through the 3D model. This can be achieved using multiple approaches from simple ray tracing to advanced full waveform calculation. In this study simple and efficient implementation of fast marching method is presented. This method provides more information than ray tracing and is much less complicated than methods like full waveform being the perfect compromise. Presented code is written in C++, well commented and is easy to modify for different types of studies. Additionally performance is widely discussed including possibilities of multithreading and massive parallelism like GPU. Source code will be published in 2016 as it is part of the PhD thesis. National Science Centre Poland provided financial support for this work via NCN grant DEC-2011/02/A/ST10/00284.
NASA Astrophysics Data System (ADS)
Arumugam, S.; Xing, A.; Vial, P.; Scotti, A.; Stirton, R.; Goozee, G.; Holloway, Lois
2013-06-01
The impact of 3D rotational errors in patient positioning on dose delivered target volumes and critical structures in IMRT was studied. Patient rotational errors ranging from -30 to +30 was introduced to IMRT treatment plans of pelvis, head and neck and brain treatment sites and the impact of rotational error on DVH metrics was assessed. The magnitude of impact of rotational error on the error in dose delivered to the target volume and critical structures depends on the location of the structures from plan isocentre. In studied plans, a maximum percentage difference of up to -9.8(1s=13.4) % in D95 to PTV was observed for head and neck treatments. Similarly, in Brain treatments a maximum difference of up to 24.0(1s=33.0) % in maximum dose of Optic chiasm was observed. The results suggest that failure to correct patient's rotational error results in under-dosage to target volumes and over-dosage to the critical structures in some specific treatment scenarios.
NASA Astrophysics Data System (ADS)
Lalone, Emily A.; Fox, Anne-Marie V.; Kedgley, Angela E.; Jenkyn, Thomas R.; King, Graham J. W.; Athwal, George S.; Johnson, James A.; Peters, Terry M.
2011-10-01
The study of joint congruency at the glenohumeral joint of the shoulder using computed tomography (CT) and three-dimensional (3D) reconstructions of joint surfaces is an area of significant clinical interest. However, ionizing radiation delivered to patients during CT examinations is much higher than other types of radiological imaging. The shoulder represents a significant challenge for this modality as it is adjacent to the thyroid gland and breast tissue. The objective of this study was to determine the optimal CT scanning techniques that would minimize radiation dose while accurately quantifying joint congruency of the shoulder. The results suggest that only one-tenth of the standard applied total current (mA) and a pitch ratio of 1.375:1 was necessary to produce joint congruency values consistent with that of the higher dose scans. Using the CT scanning techniques examined in this study, the effective dose applied to the shoulder to quantify joint congruency was reduced by 88.9% compared to standard clinical CT imaging techniques.
Ojala, Jarkko J; Kapanen, Mika K; Hyödynmaa, Simo J; Wigren, Tuija K; Pitkänen, Maunu A
2014-01-01
The accuracy of dose calculation is a key challenge in stereotactic body radiotherapy (SBRT) of the lung. We have benchmarked three photon beam dose calculation algorithms--pencil beam convolution (PBC), anisotropic analytical algorithm (AAA), and Acuros XB (AXB)--implemented in a commercial treatment planning system (TPS), Varian Eclipse. Dose distributions from full Monte Carlo (MC) simulations were regarded as a reference. In the first stage, for four patients with central lung tumors, treatment plans using 3D conformal radiotherapy (CRT) technique applying 6 MV photon beams were made using the AXB algorithm, with planning criteria according to the Nordic SBRT study group. The plans were recalculated (with same number of monitor units (MUs) and identical field settings) using BEAMnrc and DOSXYZnrc MC codes. The MC-calculated dose distributions were compared to corresponding AXB-calculated dose distributions to assess the accuracy of the AXB algorithm, to which then other TPS algorithms were compared. In the second stage, treatment plans were made for ten patients with 3D CRT technique using both the PBC algorithm and the AAA. The plans were recalculated (with same number of MUs and identical field settings) with the AXB algorithm, then compared to original plans. Throughout the study, the comparisons were made as a function of the size of the planning target volume (PTV), using various dose-volume histogram (DVH) and other parameters to quantitatively assess the plan quality. In the first stage also, 3D gamma analyses with threshold criteria 3%/3mm and 2%/2 mm were applied. The AXB-calculated dose distributions showed relatively high level of agreement in the light of 3D gamma analysis and DVH comparison against the full MC simulation, especially with large PTVs, but, with smaller PTVs, larger discrepancies were found. Gamma agreement index (GAI) values between 95.5% and 99.6% for all the plans with the threshold criteria 3%/3 mm were achieved, but 2%/2 mm
Feger, Sarah; Rief, Matthias; Zimmermann, Elke; Martus, Peter; Schuijf, Joanne Désirée; Blobel, Jörg; Richter, Felicitas; Dewey, Marc
2015-01-01
Purpose The aim of this study was the systematic image quality evaluation of coronary CT angiography (CTA), reconstructed with the 3 different levels of adaptive iterative dose reduction (AIDR 3D) and compared to filtered back projection (FBP) with quantum denoising software (QDS). Methods Standard-dose CTA raw data of 30 patients with mean radiation dose of 3.2 ± 2.6 mSv were reconstructed using AIDR 3D mild, standard, strong and compared to FBP/QDS. Objective image quality comparison (signal, noise, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), contour sharpness) was performed using 21 measurement points per patient, including measurements in each coronary artery from proximal to distal. Results Objective image quality parameters improved with increasing levels of AIDR 3D. Noise was lowest in AIDR 3D strong (p≤0.001 at 20/21 measurement points; compared with FBP/QDS). Signal and contour sharpness analysis showed no significant difference between the reconstruction algorithms for most measurement points. Best coronary SNR and CNR were achieved with AIDR 3D strong. No loss of SNR or CNR in distal segments was seen with AIDR 3D as compared to FBP. Conclusions On standard-dose coronary CTA images, AIDR 3D strong showed higher objective image quality than FBP/QDS without reducing contour sharpness. Trial Registration Clinicaltrials.gov NCT00967876 PMID:25945924
Kadoya, Noriyuki; Saito, Masahide; Ogasawara, Makoto; Fujita, Yukio; Ito, Kengo; Sato, Kiyokazu; Kishi, Kazuma; Dobashi, Suguru; Takeda, Ken; Jingu, Keiichi
2015-05-08
The purpose of this study was to evaluate the accuracy of commercially available software, using patient DVH-based QA metrics, by investigating the correlation between estimated 3D patient dose and magnitude of MLC misalignments. We tested 3DVH software with an ArcCHECK. Two different calculating modes of ArcCHECK Planned Dose Perturbation (ACPDP) were used: "Normal Sensitivity" and "High Sensitivity". Ten prostate cancer patients treated with hypofractionated VMAT (67.6 Gy/26 Fr) in our hospital were studied. For the baseline plan, we induced MLC errors (-0.75, -0.5, -0.25, 0.25, 0.5, and 0.75 mm for each single bank). We calculated the dose differences between the ACPDP dose with error and TPS dose with error using gamma passing rates and using DVH-based QA metrics. The correlations between dose estimation error and MLC position error varied with each structure and metric. A comparison using 1%/1 mm gamma index showed that the larger was the MLC error-induced, the worse were the gamma passing rates. Slopes of linear fit to dose estimation error versus MLC position error for mean dose and D95 to the PTV were 1.76 and 1.40% mm-1, respectively, for "Normal Sensitivity", and -0.53 and -0.88% mm-1, respectively, for "High Sensitivity", showing better accuracy for "High Sensitivity" than "Normal Sensitivity". On the other hand, the slopes for mean dose to the rectum and bladder, V35 to the rectum and bladder and V55 to the rectum and bladder, were -1.00, -0.55, -2.56, -1.25, -3.53, and -1.85%mm-1, respectively, for "Normal Sensitivity", and -2.89, -2.39, -4.54, -3.12, -6.24, and -4.11% mm-1, respectively, for "High Sensitivity", showing significant better accuracy for "Normal Sensitivity" than "High Sensitivity". Our results showed that 3DVH had some residual error for both sensitivities. Furthermore, we found that "Normal Sensitivity" might have better accuracy for the DVH metric for the PTV and that "High Sensitivity" might have better accuracy for DVH metrics for
NASA Astrophysics Data System (ADS)
Harvey, R. W.; Petrov, Yu. V.; Kinsey, J. E.; Liu, D.; Heidbrink, W. W.; Taylor, G.; Bonoli, P. T.
2014-10-01
Ion distribution function calculations with CQL3D have been substantially advanced through implementation of guiding-center-orbit-based Fokker-Planck Coefficients. The resulting finite-orbit-width (FOW) calculations are carried out with a fast CQL3D-Hybrid-FOW option, and in a slower but neoclassically complete (except no Er yet) CQL3D-FOW option. Good comparison between time-dependent Fast Ion Diagnostic FIDA, NPA, and neutron signals resulting from neutral beaminjection(NBI) and high harmonic fast wave (HHFW) power injected into the NSTX spherical tokamak have been simulated with the CQL3D-Hybrid-FOW, using only the FOW effects on QL diffusion, and particle losses, direct and CX. Comparisons are also made with recent CQL3D-FOW results, as well as between the original FIDA calculation code and a recent fortran version. Supported by USDOE Grants SC0006614, ER54744, and ER44649.
Haeger-Eugensson, Marie; Ferm, Martin; Elfman, Lena
2014-04-01
The interest in equestrian sports has increased substantially during the last decades, resulting in increased number of horse facilities around urban areas. In Sweden, new guidelines for safe distance have been decided based on the size of the horse facility (e.g., number of horses) and local conditions, such as topography and meteorology. There is therefore an increasing need to estimate dispersion of horse allergens to be used, for example, in the planning processes for new residential areas in the vicinity of horse facilities. The aim of this study was to develop a method for calculating short- and long-term emissions and dispersion of horse allergen and odor around horse facilities. First, a method was developed to estimate horse allergen and odor emissions at hourly resolution based on field measurements. Secondly, these emission factors were used to calculate concentrations of horse allergen and odor by using 3-D dispersion modeling. Results from these calculations showed that horse allergens spread up to about 200 m, after which concentration levels were very low (<2 U/m³). Approximately 10% of a study-group detected the smell of manure at 60m, while the majority--80%-90%--detected smell at 60 m or shorter distance from the manure heap. Modeling enabled horse allergen exposure concentrations to be determined with good time resolution.
NASA Astrophysics Data System (ADS)
Guo, X. L.; Si, R.; Li, S.; Huang, M.; Hutton, R.; Wang, Y. S.; Chen, C. Y.; Zou, Y. M.; Wang, K.; Yan, J.; Li, C. Y.; Brage, T.
2016-01-01
We present systematic and large-scale calculations for the fine-structure energy splitting and transition rate between the 3 d93/2,5/2,2D levels of Co-like ions with 28 ≤Z ≤100 . Two different fully relativistic approaches are used, based on the multiconfiguration Dirac-Hartree-Fock (MCDHF) theory and the relativistic many-body-perturbation theory (RMBPT). Especially the former gives results of similar accuracy as experiments for a large range of ions. Our calculations are therefore accurate enough to probe Breit and quantum-electro-dynamic effects. To obtain spectroscopic accuracy, we show that it is important to include deep core-valence correlation, down to and including the n =2 shell. We estimate that the uncertainties of our wavelengths are within the uncertainty of experiments, i.e., 0.02%. We also show that the frequently used flexible atomic code has an inaccurate treatment of the self-energy (SE) contribution and of the M 1 -transition properties for lower-Z ions. After correcting for the SE calculation, the resulting RMBPT transition energies are in good agreement with the MCDHF ones, especially for the high-Z end of the Co-like sequence.
Rey, Michaël; Nikitin, Andrei V; Tyuterev, Vladimir G
2014-07-28
Accurate variational high-resolution spectra calculations in the range 0-8000 cm(-1) are reported for the first time for the monodeutered methane ((12)CH3D). Global calculations were performed by using recent ab initio surfaces for line positions and line intensities derived from the main isotopologue (12)CH4. Calculation of excited vibrational levels and high-J rovibrational states is described by using the normal mode Eckart-Watson Hamiltonian combined with irreducible tensor formalism and appropriate numerical procedures for solving the quantum nuclear motion problem. The isotopic H→D substitution is studied in details by means of symmetry and nonlinear normal mode coordinate transformations. Theoretical spectra predictions are given up to J = 25 and compared with the HITRAN 2012 database representing a compilation of line lists derived from analyses of experimental spectra. The results are in very good agreement with available empirical data suggesting that a large number of yet unassigned lines in observed spectra could be identified and modeled using the present approach. PMID:25084919
Chibani, Omar C-M Ma, Charlie
2014-05-15
Purpose: To present a new accelerated Monte Carlo code for CT-based dose calculations in high dose rate (HDR) brachytherapy. The new code (HDRMC) accounts for both tissue and nontissue heterogeneities (applicator and contrast medium). Methods: HDRMC uses a fast ray-tracing technique and detailed physics algorithms to transport photons through a 3D mesh of voxels representing the patient anatomy with applicator and contrast medium included. A precalculated phase space file for the{sup 192}Ir source is used as source term. HDRM is calibrated to calculated absolute dose for real plans. A postprocessing technique is used to include the exact density and composition of nontissue heterogeneities in the 3D phantom. Dwell positions and angular orientations of the source are reconstructed using data from the treatment planning system (TPS). Structure contours are also imported from the TPS to recalculate dose-volume histograms. Results: HDRMC was first benchmarked against the MCNP5 code for a single source in homogenous water and for a loaded gynecologic applicator in water. The accuracy of the voxel-based applicator model used in HDRMC was also verified by comparing 3D dose distributions and dose-volume parameters obtained using 1-mm{sup 3} versus 2-mm{sup 3} phantom resolutions. HDRMC can calculate the 3D dose distribution for a typical HDR cervix case with 2-mm resolution in 5 min on a single CPU. Examples of heterogeneity effects for two clinical cases (cervix and esophagus) were demonstrated using HDRMC. The neglect of tissue heterogeneity for the esophageal case leads to the overestimate of CTV D90, CTV D100, and spinal cord maximum dose by 3.2%, 3.9%, and 3.6%, respectively. Conclusions: A fast Monte Carlo code for CT-based dose calculations which does not require a prebuilt applicator model is developed for those HDR brachytherapy treatments that use CT-compatible applicators. Tissue and nontissue heterogeneities should be taken into account in modern HDR
MCPI: a sub-minute Monte Carlo dose calculation engine for prostate implants.
Chibani, Omar; Williamson, Jeffrey F
2005-12-01
An accelerated Monte Carlo code [Monte Carlo dose calculation for prostate implant (MCPI)] is developed for dose calculation in prostate brachytherapy. MCPI physically simulates a set of radioactive seeds with arbitrary positions and orientations, merged in a three-dimensional (3D) heterogeneous phantom representing the prostate and surrounding tissue. MCPI uses a phase space data source-model to account for seed self-absorption and seed anisotropy. A "hybrid geometry" model (full 3D seed geometry merged in 3D mesh of voxels) is used for rigorous treatment of the interseed attenuation and tissue heterogeneity effects. MCPI is benchmarked against the MCNP5 code for idealized and real implants, for 103Pd and 125I seeds. MCPI calculates the dose distribution (2-mm voxel mesh) of a 103Pd implant (83 seeds) with 2% average statistical uncertainty in 59 s using a single Pentium 4 PC (2.4 GHz). MCPI is more than 10(3) and 10(4) times faster than MCNP5 for prostate dose calculations using 2- and 1-mm voxels, respectively. To illustrate its usefulness, MCPI is used to quantify the dosimetric effects of interseed attenuation, tissue composition, and tissue calcifications. Ignoring the interseed attenuation effect or slightly varying the prostate tissue composition may lead to 6% decreases of D100, the dose delivered to 100% of the prostate. The presence of calcifications, covering 1%-5% of the prostate volume, decreases D80, D90, and D100 by up to 32%, 37%, and 58%, respectively. In conclusion, sub-minute dose calculations, taking into account all dosimetric effects, are now possible for more accurate dose planning and dose assessment in prostate brachytherapy.
[Evaluation tests of computer systems concerning tri-dimensional dose calculations].
Simonian-Sauve, M; Smart, C
1998-01-01
The development of irradiation techniques in radiotherapy shows a clear tendency towards the systematic use of three-dimensional (3D) information. Great efforts are being made to set up 3D conformal radiotherapy. Consequently, in the aim of greater coherence and accuracy, "the dosimetric tool" must also meet the requirements of 3D radiotherapy, as it plays a role in the treatment chain. To know if the treatment planning system is a "3D", "2D" or even "1D" system, one should not be satisfied with reading the technical documentation and the program algorithm description nor entirely trust the constructor's assertions. It is essential to clearly and precisely evaluate the possibilities of the treatment planning system. Even if it is proved not to satisfy perfectly all the tests which would qualify it as a real 3D calculation system, the study of the test results helps to give clear explanations of the dosimetric results. Two series of test cases are proposed. The first series allows us to understand in which conditions the treatment planning system takes into account the scatter influence in a volume. The second series is designed to inform us about the capability of the dose calculation algorithm when the medium encloses non-homogeneities. These test cases do not constitute an exhaustive "check-list" able to tackle completely the question of 3D calculation. They are submitted as examples and should be considered as an evaluation methodology for the software implanted in the treatment planning system. PMID:9749097
Zhang, Y; Yang, J; Liu, H; Liu, D
2014-06-01
Purpose: The purpose of this work is to compare the verification results of three solutions (2D/3D ionization chamber arrays measurement and Monte Carlo simulation), the results will help make a clinical decision as how to do our cervical IMRT verification. Methods: Seven cervical cases were planned with Pinnacle 8.0m to meet the clinical acceptance criteria. The plans were recalculated in the Matrixx and Delta4 phantom with the accurate plans parameters. The plans were also recalculated by Monte Carlo using leaf sequences and MUs for individual plans of every patient, Matrixx and Delta4 phantom. All plans of Matrixx and Delta4 phantom were delivered and measured. The dose distribution of iso slice, dose profiles, gamma maps of every beam were used to evaluate the agreement. Dose-volume histograms were also compared. Results: The dose distribution of iso slice and dose profiles from Pinnacle calculation were in agreement with the Monte Carlo simulation, Matrixx and Delta4 measurement. A 95.2%/91.3% gamma pass ratio was obtained between the Matrixx/Delta4 measurement and Pinnacle distributions within 3mm/3% gamma criteria. A 96.4%/95.6% gamma pass ratio was obtained between the Matrixx/Delta4 measurement and Monte Carlo simulation within 2mm/2% gamma criteria, almost 100% gamma pass ratio within 3mm/3% gamma criteria. The DVH plot have slightly differences between Pinnacle and Delta4 measurement as well as Pinnacle and Monte Carlo simulation, but have excellent agreement between Delta4 measurement and Monte Carlo simulation. Conclusion: It was shown that Matrixx/Delta4 and Monte Carlo simulation can be used very efficiently to verify cervical IMRT delivery. In terms of Gamma value the pass ratio of Matrixx was little higher, however, Delta4 showed more problem fields. The primary advantage of Delta4 is the fact it can measure true 3D dosimetry while Monte Carlo can simulate in patients CT images but not in phantom.
NASA Astrophysics Data System (ADS)
Lougovski, A.; Hofheinz, F.; Maus, J.; Schramm, G.; Will, E.; van den Hoff, J.
2014-02-01
The aim of this study is the evaluation of on-the-fly volume of intersection computation for system’s geometry modelling in 3D PET image reconstruction. For this purpose we propose a simple geometrical model in which the cubic image voxels on the given Cartesian grid are approximated with spheres and the rectangular tubes of response (ToRs) are approximated with cylinders. The model was integrated into a fully 3D list-mode PET reconstruction for performance evaluation. In our model the volume of intersection between a voxel and the ToR is only a function of the impact parameter (the distance between voxel centre to ToR axis) but is independent of the relative orientation of voxel and ToR. This substantially reduces the computational complexity of the system matrix calculation. Based on phantom measurements it was determined that adjusting the diameters of the spherical voxel size and the ToR in such a way that the actual voxel and ToR volumes are conserved leads to the best compromise between high spatial resolution, low noise, and suppression of Gibbs artefacts in the reconstructed images. Phantom as well as clinical datasets from two different PET systems (Siemens ECAT HR+ and Philips Ingenuity-TF PET/MR) were processed using the developed and the respective vendor-provided (line of intersection related) reconstruction algorithms. A comparison of the reconstructed images demonstrated very good performance of the new approach. The evaluation showed the respective vendor-provided reconstruction algorithms to possess 34-41% lower resolution compared to the developed one while exhibiting comparable noise levels. Contrary to explicit point spread function modelling our model has a simple straight-forward implementation and it should be easy to integrate into existing reconstruction software, making it competitive to other existing resolution recovery techniques.
NASA Astrophysics Data System (ADS)
Caloz, Misael; Kafrouni, Marilyne; Leturgie, Quentin; Corde, Stéphanie; Downes, Simon; Lehmann, Joerg; Thwaites, David
2015-01-01
There are few reported intercomparisons or audits of combinations of advanced radiotherapy methods, particularly for 4D treatments. As part of an evaluation of the implementation of advanced radiotherapy technology, a phantom and associated methods, initially developed for in-house commissioning and QA of 4D lung treatments, has been developed further with the aim of using it for end-to-end dose intercomparison of 4D treatment planning and delivery. The respiratory thorax phantom can house moving inserts with variable speed (breathing rate) and motion amplitude. In one set-up mode it contains a small ion chamber for point dose measurements, or alternatively it can hold strips of radiochromic film to measure dose distributions. Initial pilot and feasibility measurements have been carried out in one hospital to thoroughly test the methods and procedures before using it more widely across a range of hospitals and treatment systems. Overall, the results show good agreement between measured and calculated doses and distributions, supporting the use of the phantom and methodology for multi-centre intercomparisons. However, before wider use, refinements of the method and analysis are currently underway particularly for the film measurements.
Quasi 3D dosimetry (EPID, conventional 2D/3D detector matrices)
NASA Astrophysics Data System (ADS)
Bäck, A.
2015-01-01
Patient specific pretreatment measurement for IMRT and VMAT QA should preferably give information with a high resolution in 3D. The ability to distinguish complex treatment plans, i.e. treatment plans with a difference between measured and calculated dose distributions that exceeds a specified tolerance, puts high demands on the dosimetry system used for the pretreatment measurements and the results of the measurement evaluation needs a clinical interpretation. There are a number of commercial dosimetry systems designed for pretreatment IMRT QA measurements. 2D arrays such as MapCHECK® (Sun Nuclear), MatriXXEvolution (IBA Dosimetry) and OCTAVIOUS® 1500 (PTW), 3D phantoms such as OCTAVIUS® 4D (PTW), ArcCHECK® (Sun Nuclear) and Delta4 (ScandiDos) and software for EPID dosimetry and 3D reconstruction of the dose in the patient geometry such as EPIDoseTM (Sun Nuclear) and Dosimetry CheckTM (Math Resolutions) are available. None of those dosimetry systems can measure the 3D dose distribution with a high resolution (full 3D dose distribution). Those systems can be called quasi 3D dosimetry systems. To be able to estimate the delivered dose in full 3D the user is dependent on a calculation algorithm in the software of the dosimetry system. All the vendors of the dosimetry systems mentioned above provide calculation algorithms to reconstruct a full 3D dose in the patient geometry. This enables analyzes of the difference between measured and calculated dose distributions in DVHs of the structures of clinical interest which facilitates the clinical interpretation and is a promising tool to be used for pretreatment IMRT QA measurements. However, independent validation studies on the accuracy of those algorithms are scarce. Pretreatment IMRT QA using the quasi 3D dosimetry systems mentioned above rely on both measurement uncertainty and accuracy of calculation algorithms. In this article, these quasi 3D dosimetry systems and their use in patient specific pretreatment IMRT
NASA Astrophysics Data System (ADS)
Choi, S.; Kim, C.; Kim, H. R.; Park, C.; Park, H. Y.
2015-12-01
We performed the marine magnetic and the bathymetry survey in the Lau basin for finding the submarine hydrothermal deposits in October 2009. We acquired magnetic and bathymetry datasets by using Overhouser Proton Magnetometer SeaSPY(Marine Magnetics Co.) and Multi-Beam Echo Sounder EM120(Kongsberg Co.). We conducted the data processing to obtain detailed seabed topography, magnetic anomaly and reduction to the pole(RTP). The Lau basin is one of the youngest back-arc basins in the Southwest Pacific. This region was a lot of hydrothermal activities and hydrothermal deposits. In particular, Tofua Arc(TA) in the Lau basin consists of various and complex stratovolcanos(from Massoth et al., 2007).), We calculated the magnetic susceptibility distribution of the TA19-1 seamount(longitude:176°23.5'W, latitude: 22°42.5'W)area using the RTP data by 3-D magnetic inversion from Jung's previous study(2013). Based on 2D 'compact gravity inversion' by Last & Kubik(1983), we expend it to the 3D algorithm using iterative reweighted least squares method with some weight matrices. The used weight matrices are two types: 1) the minimum gradient support(MGS) that controls the spatial distribution of the solution from Porniaguine and Zhdanov(1999); 2) the depth weight that are used according to the shape of subsurface structures. From the modeling, we derived the appropriate scale factor for the use of depth weight and setting magnetic susceptibility. Furthermore, we have to enter a very small error value to control the computation of the singular point of the inversion model that was able to be easily calculated for modeling. In addition, we applied separately weighted value for the correct shape and depth of the magnetic source. We selected the best results model by change to converge of RMS. Compared between the final modeled result and RTP values in this study, they are generally similar to the each other. But the input values and the modeled values have slightly little difference
The importance of 3D dosimetry
NASA Astrophysics Data System (ADS)
Low, Daniel
2015-01-01
Radiation therapy has been getting progressively more complex for the past 20 years. Early radiation therapy techniques needed only basic dosimetry equipment; motorized water phantoms, ionization chambers, and basic radiographic film techniques. As intensity modulated radiation therapy and image guided therapy came into widespread practice, medical physicists were challenged with developing effective and efficient dose measurement techniques. The complex 3-dimensional (3D) nature of the dose distributions that were being delivered demanded the development of more quantitative and more thorough methods for dose measurement. The quality assurance vendors developed a wide array of multidetector arrays that have been enormously useful for measuring and characterizing dose distributions, and these have been made especially useful with the advent of 3D dose calculation systems based on the array measurements, as well as measurements made using film and portal imagers. Other vendors have been providing 3D calculations based on data from the linear accelerator or the record and verify system, providing thorough evaluation of the dose but lacking quality assurance (QA) of the dose delivery process, including machine calibration. The current state of 3D dosimetry is one of a state of flux. The vendors and professional associations are trying to determine the optimal balance between thorough QA, labor efficiency, and quantitation. This balance will take some time to reach, but a necessary component will be the 3D measurement and independent calculation of delivered radiation therapy dose distributions.
Electronic structures in coupled two quantum dots by 3D-mesh Hartree-Fock-Kohn-Sham calculation
NASA Astrophysics Data System (ADS)
Matsuse, T.; Hama, T.; Kaihatsu, H.; Toyoda, N.; Takizawa, T.
To study the electronic structures of quantum dots in the framework of self-interaction-free including three dimensional effects, we adopt the theory of nonlocal effective potential introduced by Kohn and Sham [#!ks65!#]. For utilizing the advantageous point of the real space (3D) mesh method to solve the original nonlinear and nonlocal Hartree-Fock-Kohn-Sham (HFKS)-equation, we introduce a linearization of the equation in the local form by introducing the local Coulomb potentials which depend on explicitly the two single particle states. In practice, for solving the local form HFKS-equation, we use the Car-Parrinello-like relaxation method and the Coulomb potentials are obtained by solving the Poisson equation under proper boundary conditions. Firstly the observed energy gap between triplet- and singlet-states of N = 4 in DBS [#!tarucha96!#] is discussed to reproduce the addition energies and chemical potentials depending the magnetic field. Next the coupling between two-quantum dots in TBS [#!aht97!#] is studied by adding the square barrier between two dots. The spin-degeneracy [#!aht97!#] measured in gate-voltage depending on magnetic field is well reproduced in the limit of small mismatch. Finally, the electronic states in the ring structure are calculated and discussed how the ring size and magnetic field affect to the structures.
NASA Astrophysics Data System (ADS)
Jin, Shengye; Tamura, Masayuki
2012-10-01
In this paper we developed a 3D L-System tree model which expresses the leaf area density (LAD). As a key parameter, which conveys the thickness degree of the canopy and interaction capacity between a tree and the atmosphere, LAD is an important aspect in radiation transfer modeling within the vegetation canopy during the last decades. For modeling a tree, L-System is a good application which explains the internal canopy structure in detail. In the study, we developed the tree model in 3 steps. First we took photographs from eight directions using a commercial digital camera, and then extracted the canopy gap fraction. Secondly, we collected the sample camphor tree's leaf angles in the field for getting the leaf angle density function and computed the G-function from leaf angle density. We calculated the sample tree's LAD by Beer-Lambert's law. LAI-2000 instrument was the standard data source provider for evaluating the photographing method's LAD result. We set the L-System tree parameters in order to coincide with the real tree. The tree model visualization was performed by using POV-Ray v3.60. The eight directions photographing method's LAD result (0.54) was significantly close with the LAI-2000 adjusted data (0.52). Similarly the L-system tree models LAD mean value for 1000 samples was observed to be 0.54 which is close to the validation results.
Harvey, R. W.; Chan, V. S.; Chiu, S. C.; Evans, T. E.; Rosenbluth, M. N.; Whyte, D. G.
2000-11-01
Runaway electrons are calculated to be produced during the rapid plasma cooling resulting from ''killer pellet'' injection experiments, in general agreement with observations in the DIII-D [J. L. Luxon , Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] tokamak. The time-dependent dynamics of the kinetic runaway distributions are obtained with the CQL3D [R. W. Harvey and M. G. McCoy, ''The CQL3D Code,'' in Proceedings of the IAEA Technical Committee Meeting on Numerical Modeling, Montreal, 1992 (International Atomic Energy Agency, Vienna, 1992), p. 489] collisional Fokker--Planck code, including the effect of small and large angle collisions and stochastic magnetic field transport losses. The background density, temperature, and Z{sub eff} are evolved according to the KPRAD [D. G. Whyte and T. E. Evans , in Proceedings of the 24th European Conference on Controlled Fusion and Plasma Physics, Berchtesgaden, Germany (European Physical Society, Petit-Lancy, 1997), Vol. 21A, p. 1137] deposition and radiation model of pellet--plasma interactions. Three distinct runway mechanisms are apparent: (1) prompt ''hot-tail runaways'' due to the residual hot electron tail remaining from the pre-cooling phase, (2) ''knock-on'' runaways produced by large-angle Coulomb collisions on existing high energy electrons, and (3) Dreicer ''drizzle'' runaway electrons due to diffusion of electrons up to the critical velocity for electron runaway. For electron densities below {approx}1x10{sup 15}cm{sup -3}, the hot-tail runaways dominate the early time evolution, and provide the seed population for late time knock-on runaway avalanche. For small enough stochastic magnetic field transport losses, the knock-on production of electrons balances the losses at late times. For losses due to radial magnetic field perturbations in excess of {approx}0.1% of the background field, i.e., {delta}B{sub r}/B{>=}0.001, the losses
Liu, Han; Zhuang, Tingliang; Stephans, Kevin; Videtic, Gregory; Raithel, Stephen; Djemil, Toufik; Xia, Ping
2015-11-08
For patients with medically inoperable early-stage non-small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy, early treatment plans were based on a simpler dose calculation algorithm, the pencil beam (PB) calculation. Because these patients had the longest treatment follow-up, identifying dose differences between the PB calculated dose and Monte Carlo calculated dose is clinically important for understanding of treatment outcomes. Previous studies found significant dose differences between the PB dose calculation and more accurate dose calculation algorithms, such as convolution-based or Monte Carlo (MC), mostly for three-dimensional conformal radiotherapy (3D CRT) plans. The aim of this study is to investigate whether these observed dose differences also exist for intensity-modulated radiotherapy (IMRT) plans for both centrally and peripherally located tumors. Seventy patients (35 central and 35 peripheral) were retrospectively selected for this study. The clinical IMRT plans that were initially calculated with the PB algorithm were recalculated with the MC algorithm. Among these paired plans, dosimetric parameters were compared for the targets and critical organs. When compared to MC calculation, PB calculation overestimated doses to the planning target volumes (PTVs) of central and peripheral tumors with different magnitudes. The doses to 95% of the central and peripheral PTVs were overestimated by 9.7% ± 5.6% and 12.0% ± 7.3%, respectively. This dose overestimation did not affect doses to the critical organs, such as the spinal cord and lung. In conclusion, for NSCLC treated with IMRT, dose differences between the PB and MC calculations were different from that of 3D CRT. No significant dose differences in critical organs were observed between the two calculations.
Liu, Han; Zhuang, Tingliang; Stephans, Kevin; Videtic, Gregory; Raithel, Stephen; Djemil, Toufik; Xia, Ping
2015-01-01
For patients with medically inoperable early-stage non-small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy, early treatment plans were based on a simpler dose calculation algorithm, the pencil beam (PB) calculation. Because these patients had the longest treatment follow-up, identifying dose differences between the PB calculated dose and Monte Carlo calculated dose is clinically important for understanding of treatment outcomes. Previous studies found significant dose differences between the PB dose calculation and more accurate dose calculation algorithms, such as convolution-based or Monte Carlo (MC), mostly for three-dimensional conformal radiotherapy (3D CRT) plans. The aim of this study is to investigate whether these observed dose differences also exist for intensity-modulated radiotherapy (IMRT) plans for both centrally and peripherally located tumors. Seventy patients (35 central and 35 peripheral) were retrospectively selected for this study. The clinical IMRT plans that were initially calculated with the PB algorithm were recalculated with the MC algorithm. Among these paired plans, dosimetric parameters were compared for the targets and critical organs. When compared to MC calculation, PB calculation overestimated doses to the planning target volumes (PTVs) of central and peripheral tumors with different magnitudes. The doses to 95% of the central and peripheral PTVs were overestimated by 9.7% ± 5.6% and 12.0% ± 7.3%, respectively. This dose overestimation did not affect doses to the critical organs, such as the spinal cord and lung. In conclusion, for NSCLC treated with IMRT, dose differences between the PB and MC calculations were different from that of 3D CRT. No significant dose differences in critical organs were observed between the two calculations. PMID:26699560
Hybrid MV-kV 3D respiratory motion tracking during radiation therapy with low imaging dose
NASA Astrophysics Data System (ADS)
Yan, Huagang; Li, Haiyun; Liu, Zhixiang; Nath, Ravinder; Liu, Wu
2012-12-01
A novel real-time adaptive MV-kV imaging framework for image-guided radiation therapy is developed to reduce the thoracic and abdominal tumor targeting uncertainty caused by respiration-induced intrafraction motion with ultra-low patient imaging dose. In our method, continuous stereoscopic MV-kV imaging is used at the beginning of a radiation therapy delivery for several seconds to measure the implanted marker positions. After this stereoscopic imaging period, the kV imager is switched off except for the times when no fiducial marker is detected in the cine-MV images. The 3D time-varying marker positions are estimated by combining the MV 2D projection data and the motion correlations between directional components of marker motion established from the stereoscopic imaging period and updated afterwards; in particular, the most likely position is assumed to be the position on the projection line that has the shortest distance to the first principal component line segment constructed from previous trajectory points. An adaptive windowed auto-regressive prediction is utilized to predict the marker position a short time later (310 ms and 460 ms in this study) to allow for tracking system latency. To demonstrate the feasibility and evaluate the accuracy of the proposed method, computer simulations were performed for both arc and fixed-gantry deliveries using 66 h of retrospective tumor motion data from 42 patients treated for thoracic or abdominal cancers. The simulations reveal that using our hybrid approach, a smaller than 1.2 mm or 1.5 mm root-mean-square tracking error can be achieved at a system latency of 310 ms or 460 ms, respectively. Because the kV imaging is only used for a short period of time in our method, extra patient imaging dose can be reduced by an order of magnitude compared to continuous MV-kV imaging, while the clinical tumor targeting accuracy for thoracic or abdominal cancers is maintained. Furthermore, no additional hardware is required with the
Schmitt, Boris; Li, Tieyan; Kutty, Shelby; Khasheei, Alireza; Schmitt, Katharina R L; Anderson, Robert H; Lunkenheimer, Paul P; Berger, Felix; Kühne, Titus; Peters, Björn
2015-07-01
Beta-blockers contribute to treatment of heart failure. Their mechanism of action, however, is incompletely understood. Gradients in beta-blocker sensitivity of helically aligned cardiomyocytes compared with counteracting transversely intruding cardiomyocytes seem crucial. We hypothesize that selective blockade of transversely intruding cardiomyocytes by low-dose beta-blockade unloads ventricular performance. Cardiac magnetic resonance imaging (MRI) 3D tagging delivers parameters of myocardial performance. We studied 13 healthy volunteers by MRI 3D tagging during escalated intravenous administration of esmolol. The circumferential, longitudinal, and radial myocardial shortening was determined for each dose. The curves were analyzed for peak value, time-to-peak, upslope, and area-under-the-curve. At low doses, from 5 to 25 μg·kg(-1)·min(-1), peak contraction increased while time-to-peak decreased yielding a steeper upslope. Combining the values revealed a left shift of the curves at low doses compared with baseline without esmolol. At doses of 50 to 150 μg·kg(-1)·min(-1), a right shift with flattening occurred. In healthy volunteers we found more pronounced myocardial shortening at low compared with clinical dosage of beta-blockers. In patients with ventricular hypertrophy and higher prevalence of transversely intruding cardiomyocytes selective low-dose beta-blockade could be even more effective. MRI 3D tagging could help to determine optimal individual beta-blocker dosing avoiding undesirable side effects. PMID:25888512
Calculation of dose conversion factors for thoron decay products.
Ishikawa, Tetsuo; Tokonami, Shinji; Nemeth, Csaba
2007-12-01
The dose conversion factors for short-lived thoron decay products were calculated using a dosimetric approach. The calculations were based on a computer program LUDEP, which implements the ICRP 66 respiratory tract model. The dose per equilibrium equivalent concentration for thoron (EETC) was calculated with respect to (1) equivalent dose to each region of the lung tissues (bronchial, bronchiolar and alveolar), (2) weighted equivalent dose to organs other than lung, and (3) effective dose. The calculations indicated that (1) the most exposed region of the lung tissues was the bronchial for the unattached fraction and the bronchiolar for the attached fraction, (2) the effective dose is dominated by the contribution of lung dose, and (3) the effective dose per EETC was about four times larger than the effective dose per equilibrium equivalent concentration for radon (EERC). The calculated dose conversion factors were applied to the comparative dosimetry for some thoron-enhanced areas where the EERC and EETC have been measured. In the case of a spa in Japan, the dose from thoron decay products was larger than the dose from radon decay products.
NASA Astrophysics Data System (ADS)
Gupta, N.; Callaghan, S.; Graves, R.; Mehta, G.; Zhao, L.; Deelman, E.; Jordan, T. H.; Kesselman, C.; Okaya, D.; Cui, Y.; Field, E.; Gupta, V.; Vahi, K.; Maechling, P. J.
2006-12-01
Researchers from the SCEC Community Modeling Environment (SCEC/CME) project are utilizing the CyberShake computational platform and a distributed high performance computing environment that includes USC High Performance Computer Center and the NSF TeraGrid facilities to calculate physics-based probabilistic seismic hazard curves for several sites in the Southern California area. Traditionally, probabilistic seismic hazard analysis (PSHA) is conducted using intensity measure relationships based on empirical attenuation relationships. However, a more physics-based approach using waveform modeling could lead to significant improvements in seismic hazard analysis. Members of the SCEC/CME Project have integrated leading-edge PSHA software tools, SCEC-developed geophysical models, validated anelastic wave modeling software, and state-of-the-art computational technologies on the TeraGrid to calculate probabilistic seismic hazard curves using 3D waveform-based modeling. The CyberShake calculations for a single probablistic seismic hazard curve require tens of thousands of CPU hours and multiple terabytes of disk storage. The CyberShake workflows are run on high performance computing systems including multiple TeraGrid sites (currently SDSC and NCSA), and the USC Center for High Performance Computing and Communications. To manage the extensive job scheduling and data requirements, CyberShake utilizes a grid-based scientific workflow system based on the Virtual Data System (VDS), the Pegasus meta-scheduler system, and the Globus toolkit. Probabilistic seismic hazard curves for spectral acceleration at 3.0 seconds have been produced for eleven sites in the Southern California region, including rock and basin sites. At low ground motion levels, there is little difference between the CyberShake and attenuation relationship curves. At higher ground motion (lower probability) levels, the curves are similar for some sites (downtown LA, I-5/SR-14 interchange) but different for
None, None
2015-09-28
Coulomb interaction between charged particles inside a bunch is one of the most importance collective effects in beam dynamics, becoming even more significant as the energy of the particle beam is lowered to accommodate analytical and low-Z material imaging purposes such as in the time resolved Ultrafast Electron Microscope (UEM) development currently underway at Michigan State University. In addition, space charge effects are the key limiting factor in the development of ultrafast atomic resolution electron imaging and diffraction technologies and are also correlated with an irreversible growth in rms beam emittance due to fluctuating components of the nonlinear electron dynamics.more » In the short pulse regime used in the UEM, space charge effects also lead to virtual cathode formation in which the negative charge of the electrons emitted at earlier times, combined with the attractive surface field, hinders further emission of particles and causes a degradation of the pulse properties. Space charge and virtual cathode effects and their remediation are core issues for the development of the next generation of high-brightness UEMs. Since the analytical models are only applicable for special cases, numerical simulations, in addition to experiments, are usually necessary to accurately understand the space charge effect. In this paper we will introduce a grid-free differential algebra based multiple level fast multipole algorithm, which calculates the 3D space charge field for n charged particles in arbitrary distribution with an efficiency of O(n), and the implementation of the algorithm to a simulation code for space charge dominated photoemission processes.« less
None, None
2015-09-28
Coulomb interaction between charged particles inside a bunch is one of the most importance collective effects in beam dynamics, becoming even more significant as the energy of the particle beam is lowered to accommodate analytical and low-Z material imaging purposes such as in the time resolved Ultrafast Electron Microscope (UEM) development currently underway at Michigan State University. In addition, space charge effects are the key limiting factor in the development of ultrafast atomic resolution electron imaging and diffraction technologies and are also correlated with an irreversible growth in rms beam emittance due to fluctuating components of the nonlinear electron dynamics. In the short pulse regime used in the UEM, space charge effects also lead to virtual cathode formation in which the negative charge of the electrons emitted at earlier times, combined with the attractive surface field, hinders further emission of particles and causes a degradation of the pulse properties. Space charge and virtual cathode effects and their remediation are core issues for the development of the next generation of high-brightness UEMs. Since the analytical models are only applicable for special cases, numerical simulations, in addition to experiments, are usually necessary to accurately understand the space charge effect. In this paper we will introduce a grid-free differential algebra based multiple level fast multipole algorithm, which calculates the 3D space charge field for n charged particles in arbitrary distribution with an efficiency of O(n), and the implementation of the algorithm to a simulation code for space charge dominated photoemission processes.
Shiri, Fereshteh; Pirhadi, Somayeh; Ghasemi, Jahan B.
2015-01-01
Mer receptor tyrosine kinase is a promising novel cancer therapeutic target in many human cancers, because abnormal activation of Mer has been implicated in survival signaling and chemoresistance. 3D-QSAR analyses based on alignment independent descriptors were performed on a series of 81 Mer specific tyrosine kinase inhibitors. The fractional factorial design (FFD) and the enhanced replacement method (ERM) were applied and tested as variable selection algorithms for the selection of optimal subsets of molecular descriptors from a much greater pool of such regression variables. The data set was split into 65 molecules as the training set and 16 compounds as the test set. All descriptors were generated by using the GRid INdependent descriptors (GRIND) approach. After variable selection, GRIND were correlated with activity values (pIC50) by PLS regression. Of the two applied variable selection methods, ERM had a noticeable improvement on the statistical parameters of PLS model, and yielded a q2 value of 0.77, an rpred2 of 0.94, and a low RMSEP value of 0.25. The GRIND information contents influencing the affinity on Mer specific tyrosine kinase were also confirmed by docking studies. In a quantum calculation study, the energy difference between HOMO and LUMO (gap) implied the high interaction of the most active molecule in the active site of the protein. In addition, the molecular electrostatic potential energy at DFT level confirmed results obtained from the molecular docking. The identified key features obtained from the molecular modeling, enabled us to design novel kinase inhibitors. PMID:27013913
Total Monte Carlo evaluation for dose calculations.
Sjöstrand, H; Alhassan, E; Conroy, S; Duan, J; Hellesen, C; Pomp, S; Österlund, M; Koning, A; Rochman, D
2014-10-01
Total Monte Carlo (TMC) is a method to propagate nuclear data (ND) uncertainties in transport codes, by using a large set of ND files, which covers the ND uncertainty. The transport code is run multiple times, each time with a unique ND file, and the result is a distribution of the investigated parameter, e.g. dose, where the width of the distribution is interpreted as the uncertainty due to ND. Until recently, this was computer intensive, but with a new development, fast TMC, more applications are accessible. The aim of this work is to test the fast TMC methodology on a dosimetry application and to propagate the (56)Fe uncertainties on the predictions of the dose outside a proposed 14-MeV neutron facility. The uncertainty was found to be 4.2 %. This can be considered small; however, this cannot be generalised to all dosimetry applications and so ND uncertainties should routinely be included in most dosimetry modelling.
NASA Astrophysics Data System (ADS)
Tang, Xiangyang; Hsieh, Jiang; Nilsen, Roy A.
2006-03-01
A three-dimensional weighted cone beam filtered backprojection (CB-FBP) algorithm (namely 3D weighted CB-FBP algorithm) has been proposed to reconstruct images from the projection data acquired along a helical trajectory in angular ranges up to [0, 2π]. However, an over scan is usually employed in the clinic to provide premium image qualities for an accurate diagnosis at the most challenging anatomic structures, such as head, spine and extremities. In an over scan, the corresponding normalized helical pitch is usually smaller than 1:1, under which the projection data acquired along angular range larger than [0, 2π] can be utilized to reconstruct an image. To improve noise characteristics or dose efficiency in an over scan, we extended the 3D weighted CB-FBP algorithm to handle helical pitches that are smaller than 1:1, while the algorithm's other advantages, such as reconstruction accuracy and computational efficiency, are maintained. The novelty of the extended 3D weighted CB-FBP algorithm is the decomposition of an over scan with an angular range corresponding to [0, 2π + Δβ] (0 < Δβ < 2π) into a union of full scans with an angular range corresponding to [0, 2π]. As a result, the extended 3D weighted function is a weighted sum of all 3D weighting functions corresponding to each overlapped full scan. An experimental evaluation shows that, the extended 3D weighted CB-FBP algorithm can significantly improve noise characteristics or dose efficiency of the 3D weighted CB-FBP algorithm at helical pitch smaller than 1:1, while its reconstruction accuracy and computational efficiency are maintained. It is imortant to indicate that, the extended 3D weighting function is still applied on projection data before 3D backporjection, resulting in the computational efficiency of the extended 3D weighted CB-FBP algorithm comparable to that of the 3D weighted CB-FBP algorithm. It is believed that, such an efficient CB reconstruction algorithm that can provide premium
NASA Technical Reports Server (NTRS)
Plante, I.; Cucinotta, F. A.
2010-01-01
INTRODUCTION: The radiation track structure is of crucial importance to understand radiation damage to molecules and subsequent biological effects. Of a particular importance in radiobiology is the induction of double-strand breaks (DSBs) by ionizing radiation, which are caused by clusters of lesions in DNA, and oxidative damage to cellular constituents leading to aberrant signaling cascades. DSB can be visualized within cell nuclei with gamma-H2AX experiments. MATERIAL AND METHODS: In DSB induction models, the DSB probability is usually calculated by the local dose obtained from a radial dose profile of HZE tracks. In this work, the local dose imparted by HZE ions is calculated directly from the 3D Monte-Carlo simulation code RITRACKS. A cubic volume of 5 micron edge (Figure 1) is irradiated by a (Fe26+)-56 ion of 1 GeV/amu (LET approx.150 keV/micron) and by a fluence of 450 H+ ions, 300 MeV/amu (LET approx. 0.3 keV/micron). In both cases, the dose deposited in the volume is approx.1 Gy. The dose is then calculated into each 3D pixels (voxels) of 20 nm edge and visualized in 3D. RESULTS AND DISCUSSION: The dose is deposited uniformly in the volume by the H+ ions. The voxels which receive a high dose (orange) corresponds to electron track ends. The dose is deposited differently by the 56Fe26+ ion. Very high dose (red) is deposited in voxels with direct ion traversal. Voxels with electron track ends (orange) are also found distributed around the path of the track. In both cases, the appearance of the dose distribution looks very similar to DSBs seen in gammaH2AX experiments, particularly when the visualization threshold is applied. CONCLUSION: The refinement of the dose calculation to the nanometer scale has revealed important differences in the energy deposition between high- and low-LET ions. Voxels of very high dose are only found in the path of high-LET ions. Interestingly, experiments have shown that DSB induced by high-LET radiation are more difficult to
DVR3D: a program suite for the calculation of rotation-vibration spectra of triatomic molecules
NASA Astrophysics Data System (ADS)
Tennyson, Jonathan; Kostin, Maxim A.; Barletta, Paolo; Harris, Gregory J.; Polyansky, Oleg L.; Ramanlal, Jayesh; Zobov, Nikolai F.
2004-11-01
The DVR3D program suite calculates energy levels, wavefunctions, and where appropriate dipole transition moments, for rotating and vibrating triatomic molecules. Potential energy and, where necessary, dipole surfaces must be provided. Expectation values of geometrically defined functions can be calculated, a feature which is particularly useful for fitting potential energy surfaces. The programs use an exact (within the Born-Oppenheimer approximation) Hamiltonian and offer a choice of Jacobi or Radau internal coordinates and several body-fixed axes. Rotationally excited states are treated using an efficient two-step algorithm. The programs uses a Discrete Variable Representation (DVR) based on Gauss-Jacobi and Gauss-Laguerre quadrature for all 3 internal coordinates and thus yields a fully point-wise representation of the wavefunctions. The vibrational step uses successive diagonalisation and truncation which is implemented for a number of possible coordinate orderings. The rotational, expectation value and transition dipole programs exploit the savings offered by performing integrals on a DVR grid. The new version has been rewritten in FORTRAN 90 to exploit the dynamic array allocations and the algorithm for dipole and spectra calculations have been substantially improved. New modules allow the z-axis to be embedded perpendicular to the plane of the molecule and for the calculation of expectation values. Program summaryTitle of the program: DVR3D suite Catalogue number: ADTI Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTI Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Programming language: Fortran 90 No. of lines in distributed program, including test data, etc.: 61 574 No. of bytes in distributed program, including test data, etc.: 972 404 Distribution format: tar.gz New version summaryTitle of program: DVR3DRJZ Catalogue number: ADTB Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTB Program obtainable
DICOM organ dose does not accurately represent calculated dose in mammography
NASA Astrophysics Data System (ADS)
Suleiman, Moayyad E.; Brennan, Patrick C.; McEntee, Mark F.
2016-03-01
This study aims to analyze the agreement between the mean glandular dose estimated by the mammography unit (organ dose) and mean glandular dose calculated using Dance et al published method (calculated dose). Anonymised digital mammograms from 50 BreastScreen NSW centers were downloaded and exposure information required for the calculation of dose was extracted from the DICOM header along with the organ dose estimated by the system. Data from quality assurance annual tests for the included centers were collected and used to calculate the mean glandular dose for each mammogram. Bland-Altman analysis and a two-tailed paired t-test were used to study the agreement between calculated and organ dose and the significance of any differences. A total of 27,869 dose points from 40 centers were included in the study, mean calculated dose and mean organ dose (+/- standard deviation) were 1.47 (+/-0.66) and 1.38 (+/-0.56) mGy respectively. A statistically significant 0.09 mGy bias (t = 69.25; p<0.0001) with 95% limits of agreement between calculated and organ doses ranging from -0.34 and 0.52 were shown by Bland-Altman analysis, which indicates a small yet highly significant difference between the two means. The use of organ dose for dose audits is done at the risk of over or underestimating the calculated dose, hence, further work is needed to identify the causal agents for differences between organ and calculated doses and to generate a correction factor for organ dose.
Study of dose calculation on breast brachytherapy using prism TPS
NASA Astrophysics Data System (ADS)
Fendriani, Yoza; Haryanto, Freddy
2015-09-01
PRISM is one of non-commercial Treatment Planning System (TPS) and is developed at the University of Washington. In Indonesia, many cancer hospitals use expensive commercial TPS. This study aims to investigate Prism TPS which been applied to the dose distribution of brachytherapy by taking into account the effect of source position and inhomogeneities. The results will be applicable for clinical Treatment Planning System. Dose calculation has been implemented for water phantom and CT scan images of breast cancer using point source and line source. This study used point source and line source and divided into two cases. On the first case, Ir-192 seed source is located at the center of treatment volume. On the second case, the source position is gradually changed. The dose calculation of every case performed on a homogeneous and inhomogeneous phantom with dimension 20 × 20 × 20 cm3. The inhomogeneous phantom has inhomogeneities volume 2 × 2 × 2 cm3. The results of dose calculations using PRISM TPS were compared to literature data. From the calculation of PRISM TPS, dose rates show good agreement with Plato TPS and other study as published by Ramdhani. No deviations greater than ±4% for all case. Dose calculation in inhomogeneous and homogenous cases show similar result. This results indicate that Prism TPS is good in dose calculation of brachytherapy but not sensitive for inhomogeneities. Thus, the dose calculation parameters developed in this study were found to be applicable for clinical treatment planning of brachytherapy.
Proton dose calculation based on in-air fluence measurements.
Schaffner, Barbara
2008-03-21
Proton dose calculation algorithms--as well as photon and electron algorithms--are usually based on configuration measurements taken in a water phantom. The exceptions to this are proton dose calculation algorithms for modulated scanning beams. There, it is usual to measure the spot profiles in air. We use the concept of in-air configuration measurements also for scattering and uniform scanning (wobbling) proton delivery techniques. The dose calculation includes a separate step for the calculation of the in-air fluence distribution per energy layer. The in-air fluence calculation is specific to the technique and-to a lesser extent-design of the treatment machine. The actual dose calculation uses the in-air fluence as input and is generic for all proton machine designs and techniques. PMID:18367787
Fast dose calculation in magnetic fields with GPUMCD.
Hissoiny, S; Raaijmakers, A J E; Ozell, B; Després, P; Raaymakers, B W
2011-08-21
A new hybrid imaging-treatment modality, the MRI-Linac, involves the irradiation of the patient in the presence of a strong magnetic field. This field acts on the charged particles, responsible for depositing dose, through the Lorentz force. These conditions require a dose calculation engine capable of taking into consideration the effect of the magnetic field on the dose distribution during the planning stage. Also in the case of a change in anatomy at the time of treatment, a fast online replanning tool is desirable. It is improbable that analytical solutions such as pencil beam calculations can be efficiently adapted for dose calculations within a magnetic field. Monte Carlo simulations have therefore been used for the computations but the calculation speed is generally too slow to allow online replanning. In this work, GPUMCD, a fast graphics processing unit (GPU)-based Monte Carlo dose calculation platform, was benchmarked with a new feature that allows dose calculations within a magnetic field. As a proof of concept, this new feature is validated against experimental measurements. GPUMCD was found to accurately reproduce experimental dose distributions according to a 2%-2 mm gamma analysis in two cases with large magnetic field-induced dose effects: a depth-dose phantom with an air cavity and a lateral-dose phantom surrounded by air. Furthermore, execution times of less than 15 s were achieved for one beam in a prostate case phantom for a 2% statistical uncertainty while less than 20 s were required for a seven-beam plan. These results indicate that GPUMCD is an interesting candidate, being fast and accurate, for dose calculations for the hybrid MRI-Linac modality.
NASA Astrophysics Data System (ADS)
Aringer, K.; Roschlaub, R.
2013-09-01
The Bavarian State Office for Surveying and Geoinformation has launched a statewide 3D Building Model with standardized roof shapes without textures for all 8.1 million buildings in Bavaria. For acquisition of the 3D Building Model LiDAR-data are used as data basis as well as the building ground plans of the official cadastral map and a list of standardized roof shapes. The data management of the 3D Building Model is carried out by a central database with the usage of a nationwide standardized data model and the data exchange interface CityGML. On the one hand the update of the 3D Building Model for new buildings is done by terrestrial building measurements within the maintenance process of the cadastre. On the other hand the roofs of buildings which were built after the LiDAR flight and which were not measured terrestrially yet, are captured by means of picture-based digital surface-models derived from image-matching of oriented aerial photographs (DSM from image matching).
[3D reconstructions in radiotherapy planning].
Schlegel, W
1991-10-01
3D Reconstructions from tomographic images are used in the planning of radiation therapy to study important anatomical structures such as the body surface, target volumes, and organs at risk. The reconstructed anatomical models are used to define the geometry of the radiation beams. In addition, 3D voxel models are used for the calculation of the 3D dose distributions with an accuracy, previously impossible to achieve. Further uses of 3D reconstructions are in the display and evaluation of 3D therapy plans, and in the transfer of treatment planning parameters to the irradiation situation with the help of digitally reconstructed radiographs. 3D tomographic imaging with subsequent 3D reconstruction must be regarded as a completely new basis for the planning of radiation therapy, enabling tumor-tailored radiation therapy of localized target volumes with increased radiation doses and improved sparing of organs at risk. 3D treatment planning is currently being evaluated in clinical trials in connection with the new treatment techniques of conformation radiotherapy. Early experience with 3D treatment planning shows that its clinical importance in radiotherapy is growing, but will only become a standard radiotherapy tool when volumetric CT scanning, reliable and user-friendly treatment planning software, and faster and cheaper PACS-integrated medical work stations are accessible to radiotherapists.
Weighting of secondary radiations in organ dose calculations.
Siiskonen, T; Tapiovaara, M
2010-09-01
The current system of dose quantities in radiological protection is based, in addition to the absorbed dose, on the concepts of equivalent dose and effective dose. This system has been developed mainly with uniform whole-body exposures in mind. Conceptual and practical problems arise when the system is applied to more general exposure situations where the radiation quality is altered within the human body. In this article these problems are discussed, using proton beam radiotherapy as a specific example, and a proposition is made that dose equivalent quantities should be used instead of equivalent doses when organ doses are of interest. The calculations of out-of-field organ doses in proton therapy show that the International Commission on Radiological Protection-prescribed use of the proton weighting factor generally leads to an underestimation of the stochastic risks, while the use of neutron weighting factors in the way as practised in the literature leads to a significant overestimation of these risks.
Baillie, D; St Aubin, J; Fallone, B; Steciw, S
2014-06-15
Purpose: To design a new compact S-band linac waveguide capable of producing a 10 MV x-ray beam, while maintaining the length (27.5 cm) of current 6 MV waveguides. This will allow higher x-ray energies to be used in our linac-MRI systems with the same footprint. Methods: Finite element software COMSOL Multiphysics was used to design an accelerator cavity matching one published in an experiment breakdown study, to ensure that our modeled cavities do not exceed the threshold electric fields published. This cavity was used as the basis for designing an accelerator waveguide, where each cavity of the full waveguide was tuned to resonate at 2.997 GHz by adjusting the cavity diameter. The RF field solution within the waveguide was calculated, and together with an electron-gun phase space generated using Opera3D/SCALA, were input into electron tracking software PARMELA to compute the electron phase space striking the x-ray target. This target phase space was then used in BEAM Monte Carlo simulations to generate percent depth doses curves for this new linac, which were then used to re-optimize the waveguide geometry. Results: The shunt impedance, Q-factor, and peak-to-mean electric field ratio were matched to those published for the breakdown study to within 0.1% error. After tuning the full waveguide, the peak surface fields are calculated to be 207 MV/m, 13% below the breakdown threshold, and a d-max depth of 2.42 cm, a D10/20 value of 1.59, compared to 2.45 cm and 1.59, respectively, for the simulated Varian 10 MV linac and brehmsstrahlung production efficiency 20% lower than a simulated Varian 10 MV linac. Conclusion: This work demonstrates the design of a functional 27.5 cm waveguide producing 10 MV photons with characteristics similar to a Varian 10 MV linac.
Calculation of the virtual current in an electromagnetic flow meter with one bubble using 3D model.
Zhang, Xiao-Zhang; Li, Yantao
2004-04-01
Based on the theory of electromagnetic induction flow measurement, the Laplace equation in a complicated three-dimensional (3D) domain is solved by an alternating method. Virtual current potentials are obtained for an electromagnetic flow meter with one spherical bubble inside. The solutions are used to investigate the effects of bubble size and bubble position on the virtual current. Comparisons are done among the cases of 2D and 3D models, and of point electrode and large electrode. The results show that the 2D model overestimates the effect, while large electrodes are least sensitive to the bubble. This paper offers fundamentals for the study of the behavior of an electromagnetic flow meter in multiphase flow. For application, the results provide a possible way to estimate errors of the flow meter caused by multiphase flow.
Klüter, Sebastian Schubert, Kai; Lissner, Steffen; Sterzing, Florian; Oetzel, Dieter; Debus, Jürgen; Schlegel, Wolfgang; Oelfke, Uwe; Nill, Simeon
2014-08-15
Purpose: The dosimetric verification of treatment plans in helical tomotherapy usually is carried out via verification measurements. In this study, a method for independent dose calculation of tomotherapy treatment plans is presented, that uses a conventional treatment planning system with a pencil kernel dose calculation algorithm for generation of verification dose distributions based on patient CT data. Methods: A pencil beam algorithm that directly uses measured beam data was configured for dose calculation for a tomotherapy machine. Tomotherapy treatment plans were converted into a format readable by an in-house treatment planning system by assigning each projection to one static treatment field and shifting the calculation isocenter for each field in order to account for the couch movement. The modulation of the fluence for each projection is read out of the delivery sinogram, and with the kernel-based dose calculation, this information can directly be used for dose calculation without the need for decomposition of the sinogram. The sinogram values are only corrected for leaf output and leaf latency. Using the converted treatment plans, dose was recalculated with the independent treatment planning system. Multiple treatment plans ranging from simple static fields to real patient treatment plans were calculated using the new approach and either compared to actual measurements or the 3D dose distribution calculated by the tomotherapy treatment planning system. In addition, dose–volume histograms were calculated for the patient plans. Results: Except for minor deviations at the maximum field size, the pencil beam dose calculation for static beams agreed with measurements in a water tank within 2%/2 mm. A mean deviation to point dose measurements in the cheese phantom of 0.89% ± 0.81% was found for unmodulated helical plans. A mean voxel-based deviation of −0.67% ± 1.11% for all voxels in the respective high dose region (dose values >80%), and a mean local
Impact of temporal probability in 4D dose calculation for lung tumors.
Rouabhi, Ouided; Ma, Mingyu; Bayouth, John; Xia, Junyi
2015-11-08
The purpose of this study was to evaluate the dosimetric uncertainty in 4D dose calculation using three temporal probability distributions: uniform distribution, sinusoidal distribution, and patient-specific distribution derived from the patient respiratory trace. Temporal probability, defined as the fraction of time a patient spends in each respiratory amplitude, was evaluated in nine lung cancer patients. Four-dimensional computed tomography (4D CT), along with deformable image registration, was used to compute 4D dose incorporating the patient's respiratory motion. First, the dose of each of 10 phase CTs was computed using the same planning parameters as those used in 3D treatment planning based on the breath-hold CT. Next, deformable image registration was used to deform the dose of each phase CT to the breath-hold CT using the deformation map between the phase CT and the breath-hold CT. Finally, the 4D dose was computed by summing the deformed phase doses using their corresponding temporal probabilities. In this study, 4D dose calculated from the patient-specific temporal probability distribution was used as the ground truth. The dosimetric evaluation matrix included: 1) 3D gamma analysis, 2) mean tumor dose (MTD), 3) mean lung dose (MLD), and 4) lung V20. For seven out of nine patients, both uniform and sinusoidal temporal probability dose distributions were found to have an average gamma passing rate > 95% for both the lung and PTV regions. Compared with 4D dose calculated using the patient respiratory trace, doses using uniform and sinusoidal distribution showed a percentage difference on average of -0.1% ± 0.6% and -0.2% ± 0.4% in MTD, -0.2% ± 1.9% and -0.2% ± 1.3% in MLD, 0.09% ± 2.8% and -0.07% ± 1.8% in lung V20, -0.1% ± 2.0% and 0.08% ± 1.34% in lung V10, 0.47% ± 1.8% and 0.19% ± 1.3% in lung V5, respectively. We concluded that four-dimensional dose computed using either a uniform or sinusoidal temporal probability distribution can
Dose Rate Calculations for Rotary Mode Core Sampling Exhauster
FOUST, D.J.
2000-10-26
This document provides the calculated estimated dose rates for three external locations on the Rotary Mode Core Sampling (RMCS) exhauster HEPA filter housing, per the request of Characterization Field Engineering.
Fast convolution-superposition dose calculation on graphics hardware.
Hissoiny, Sami; Ozell, Benoît; Després, Philippe
2009-06-01
The numerical calculation of dose is central to treatment planning in radiation therapy and is at the core of optimization strategies for modern delivery techniques. In a clinical environment, dose calculation algorithms are required to be accurate and fast. The accuracy is typically achieved through the integration of patient-specific data and extensive beam modeling, which generally results in slower algorithms. In order to alleviate execution speed problems, the authors have implemented a modern dose calculation algorithm on a massively parallel hardware architecture. More specifically, they have implemented a convolution-superposition photon beam dose calculation algorithm on a commodity graphics processing unit (GPU). They have investigated a simple porting scenario as well as slightly more complex GPU optimization strategies. They have achieved speed improvement factors ranging from 10 to 20 times with GPU implementations compared to central processing unit (CPU) implementations, with higher values corresponding to larger kernel and calculation grid sizes. In all cases, they preserved the numerical accuracy of the GPU calculations with respect to the CPU calculations. These results show that streaming architectures such as GPUs can significantly accelerate dose calculation algorithms and let envision benefits for numerically intensive processes such as optimizing strategies, in particular, for complex delivery techniques such as IMRT and are therapy.
Verification of Calculated Skin Doses in Postmastectomy Helical Tomotherapy
Ito, Shima; Parker, Brent C.; Levine, Renee; Sanders, Mary Ella; Fontenot, Jonas; Gibbons, John; Hogstrom, Kenneth
2011-10-01
Purpose: To verify the accuracy of calculated skin doses in helical tomotherapy for postmastectomy radiation therapy (PMRT). Methods and Materials: In vivo thermoluminescent dosimeters (TLDs) were used to measure the skin dose at multiple points in each of 14 patients throughout the course of treatment on a TomoTherapy Hi.Art II system, for a total of 420 TLD measurements. Five patients were evaluated near the location of the mastectomy scar, whereas 9 patients were evaluated throughout the treatment volume. The measured dose at each location was compared with calculations from the treatment planning system. Results: The mean difference and standard error of the mean difference between measurement and calculation for the scar measurements was -1.8% {+-} 0.2% (standard deviation [SD], 4.3%; range, -11.1% to 10.6%). The mean difference and standard error of the mean difference between measurement and calculation for measurements throughout the treatment volume was -3.0% {+-} 0.4% (SD, 4.7%; range, -18.4% to 12.6%). The mean difference and standard error of the mean difference between measurement and calculation for all measurements was -2.1% {+-} 0.2% (standard deviation, 4.5%: range, -18.4% to 12.6%). The mean difference between measured and calculated TLD doses was statistically significant at two standard deviations of the mean, but was not clinically significant (i.e., was <5%). However, 23% of the measured TLD doses differed from the calculated TLD doses by more than 5%. Conclusions: The mean of the measured TLD doses agreed with TomoTherapy calculated TLD doses within our clinical criterion of 5%.
NASA Astrophysics Data System (ADS)
Polkowski, Marcin
2016-04-01
Seismic wave travel time calculation is the most common numerical operation in seismology. The most efficient is travel time calculation in 1D velocity model - for given source, receiver depths and angular distance time is calculated within fraction of a second. Unfortunately, in most cases 1D is not enough to encounter differentiating local and regional structures. Whenever possible travel time through 3D velocity model has to be calculated. It can be achieved using ray calculation or time propagation in space. While single ray path calculation is quick it is complicated to find the ray path that connects source with the receiver. Time propagation in space using Fast Marching Method seems more efficient in most cases, especially when there are multiple receivers. In this presentation a Python module pySeismicFMM is presented - simple and very efficient tool for calculating travel time from sources to receivers. Calculation requires regular 2D or 3D velocity grid either in Cartesian or geographic coordinates. On desktop class computer calculation speed is 200k grid cells per second. Calculation has to be performed once for every source location and provides travel time to all receivers. pySeismicFMM is free and open source. Development of this tool is a part of authors PhD thesis. National Science Centre Poland provided financial support for this work via NCN grant DEC-2011/02/A/ST10/00284.
Santee, G.E. Jr.; Chang, F.H.; Mortensen, G.A.; Brockett, G.F.; Gross, M.B.; Belytschko, T.B.
1982-11-01
This report, the third in a series of reports for RP-1065, describes the final step in the stepwise approach for developing the three-dimensional, nonlinear, fluid-structure interaction methodology to assess the hydroloads on a large PWR during the subcooled portions of a hypothetical LOCA. The final step in the methodology implements enhancements and special modifications to the STEALTH 3D computer program and the WHAMSE 3D computer program. After describing the enhancements, the individual and the coupled computer programs are assessed by comparing calculational results with either analytical solutions or with experimental data. The coupled 3D STEALTH/WHAMSE computer program is then applied to the simulation of HDR Test V31.1 to further assess the program and to investigate the role that fluid-structure interaction plays in the hydrodynamic loading of reactor internals during subcooled blowdown.
Monte Carlo calculation of patient organ doses from computed tomography.
Oono, Takeshi; Araki, Fujio; Tsuduki, Shoya; Kawasaki, Keiichi
2014-01-01
In this study, we aimed to evaluate quantitatively the patient organ dose from computed tomography (CT) using Monte Carlo calculations. A multidetector CT unit (Aquilion 16, TOSHIBA Medical Systems) was modeled with the GMctdospp (IMPS, Germany) software based on the EGSnrc Monte Carlo code. The X-ray spectrum and the configuration of the bowtie filter for the Monte Carlo modeling were determined from the chamber measurements for the half-value layer (HVL) of aluminum and the dose profile (off-center ratio, OCR) in air. The calculated HVL and OCR were compared with measured values for body irradiation with 120 kVp. The Monte Carlo-calculated patient dose distribution was converted to the absorbed dose measured by a Farmer chamber with a (60)Co calibration factor at the center of a CT water phantom. The patient dose was evaluated from dose-volume histograms for the internal organs in the pelvis. The calculated Al HVL was in agreement within 0.3% with the measured value of 5.2 mm. The calculated dose profile in air matched the measured value within 5% in a range of 15 cm from the central axis. The mean doses for soft tissues were 23.5, 23.8, and 27.9 mGy for the prostate, rectum, and bladder, respectively, under exposure conditions of 120 kVp, 200 mA, a beam pitch of 0.938, and beam collimation of 32 mm. For bones of the femur and pelvis, the mean doses were 56.1 and 63.6 mGy, respectively. The doses for bone increased by up to 2-3 times that of soft tissue, corresponding to the ratio of their mass-energy absorption coefficients.
Dose-Response Calculator for ArcGIS
Hanser, Steven E.; Aldridge, Cameron L.; Leu, Matthias; Nielsen, Scott E.
2011-01-01
The Dose-Response Calculator for ArcGIS is a tool that extends the Environmental Systems Research Institute (ESRI) ArcGIS 10 Desktop application to aid with the visualization of relationships between two raster GIS datasets. A dose-response curve is a line graph commonly used in medical research to examine the effects of different dosage rates of a drug or chemical (for example, carcinogen) on an outcome of interest (for example, cell mutations) (Russell and others, 1982). Dose-response curves have recently been used in ecological studies to examine the influence of an explanatory dose variable (for example, percentage of habitat cover, distance to disturbance) on a predicted response (for example, survival, probability of occurrence, abundance) (Aldridge and others, 2008). These dose curves have been created by calculating the predicted response value from a statistical model at different levels of the explanatory dose variable while holding values of other explanatory variables constant. Curves (plots) developed using the Dose-Response Calculator overcome the need to hold variables constant by using values extracted from the predicted response surface of a spatially explicit statistical model fit in a GIS, which include the variation of all explanatory variables, to visualize the univariate response to the dose variable. Application of the Dose-Response Calculator can be extended beyond the assessment of statistical model predictions and may be used to visualize the relationship between any two raster GIS datasets (see example in tool instructions). This tool generates tabular data for use in further exploration of dose-response relationships and a graph of the dose-response curve.
Kim, Hayeon; Beriwal, Sushil; Houser, Chris; Huq, M. Saiful
2011-07-01
The purpose of this study was to analyze the dosimetric outcome of 3D image-guided high-dose-rate (HDR) brachytherapy planning for cervical cancer treatment and compare dose coverage of high-risk clinical target volume (HRCTV) to traditional Point A dose. Thirty-two patients with stage IA2-IIIB cervical cancer were treated using computed tomography/magnetic resonance imaging-based image-guided HDR brachytherapy (IGBT). Brachytherapy dose prescription was 5.0-6.0 Gy per fraction for a total 5 fractions. The HRCTV and organs at risk (OARs) were delineated following the GYN GEC/ESTRO guidelines. Total doses for HRCTV, OARs, Point A, and Point T from external beam radiotherapy and brachytherapy were summated and normalized to a biologically equivalent dose of 2 Gy per fraction (EQD2). The total planned D90 for HRCTV was 80-85 Gy, whereas the dose to 2 mL of bladder, rectum, and sigmoid was limited to 85 Gy, 75 Gy, and 75 Gy, respectively. The mean D90 and its standard deviation for HRCTV was 83.2 {+-} 4.3 Gy. This is significantly higher (p < 0.0001) than the mean value of the dose to Point A (78.6 {+-} 4.4 Gy). The dose levels of the OARs were within acceptable limits for most patients. The mean dose to 2 mL of bladder was 78.0 {+-} 6.2 Gy, whereas the mean dose to rectum and sigmoid were 57.2 {+-} 4.4 Gy and 66.9 {+-} 6.1 Gy, respectively. Image-based 3D brachytherapy provides adequate dose coverage to HRCTV, with acceptable dose to OARs in most patients. Dose to Point A was found to be significantly lower than the D90 for HRCTV calculated using the image-based technique. Paradigm shift from 2D point dose dosimetry to IGBT in HDR cervical cancer treatment needs advanced concept of evaluation in dosimetry with clinical outcome data about whether this approach improves local control and/or decreases toxicities.
Study of dose calculation on breast brachytherapy using prism TPS
Fendriani, Yoza; Haryanto, Freddy
2015-09-30
PRISM is one of non-commercial Treatment Planning System (TPS) and is developed at the University of Washington. In Indonesia, many cancer hospitals use expensive commercial TPS. This study aims to investigate Prism TPS which been applied to the dose distribution of brachytherapy by taking into account the effect of source position and inhomogeneities. The results will be applicable for clinical Treatment Planning System. Dose calculation has been implemented for water phantom and CT scan images of breast cancer using point source and line source. This study used point source and line source and divided into two cases. On the first case, Ir-192 seed source is located at the center of treatment volume. On the second case, the source position is gradually changed. The dose calculation of every case performed on a homogeneous and inhomogeneous phantom with dimension 20 × 20 × 20 cm{sup 3}. The inhomogeneous phantom has inhomogeneities volume 2 × 2 × 2 cm{sup 3}. The results of dose calculations using PRISM TPS were compared to literature data. From the calculation of PRISM TPS, dose rates show good agreement with Plato TPS and other study as published by Ramdhani. No deviations greater than ±4% for all case. Dose calculation in inhomogeneous and homogenous cases show similar result. This results indicate that Prism TPS is good in dose calculation of brachytherapy but not sensitive for inhomogeneities. Thus, the dose calculation parameters developed in this study were found to be applicable for clinical treatment planning of brachytherapy.
Varnum, Susan M.; Springer, David L.; Chaffee, Mary E.; Lien, Katie A.; Webb-Robertson, Bobbie-Jo M.; Waters, Katrina M.; Sacksteder, Colette A.
2012-12-01
Skin responses to moderate and high doses of ionizing radiation include the induction of DNA repair, apoptosis, and stress response pathways. Additionally, numerous studies indicate that radiation exposure leads to inflammatory responses in skin cells and tissue. However, the inflammatory response of skin tissue to low dose radiation (<10 cGy) is poorly understood. In order to address this, we have utilized a reconstituted human skin tissue model (MatTek EpiDerm FT) and assessed changes in 23 cytokines twenty-four and forty eight hours following treatment of skin with either 3 or 10 cGy low-dose of radiation. Three cytokines, IFN-γ, IL-2, MIP-1α, were significantly altered in response to low dose radiation. In contrast, seven cytokines were significantly altered in response to a high radiation dose of 200 cGy (IL-2, IL-10, IL-13, IFN-γ, MIP-1α, TNF α, and VEGF) or the tumor promoter 12-O-tetradecanoylphorbol 13-acetate (G-CSF, GM-CSF, IL-1α, IL-8, MIP-1α, MIP-1β, RANTES). Additionally, radiation induced inflammation appears to have a distinct cytokine response relative to the non-radiation induced stressor, TPA. Overall, these results indicate that there are subtle changes in the inflammatory protein levels following exposure to low dose radiation and this response is a sub-set of what is seen following a high dose in a human skin tissue model.
McCormack, W.D.; Ramsdell, J.V.; Napier, B.A.
1984-05-01
This document serves as a guide to Hanford contractors for obtaining or performing Hanford-related environmental dose calculations. Because environmental dose estimation techniques are state-of-the-art and are continually evolving, the data and standard methods presented herein will require periodic revision. This document is scheduled to be updated annually, but actual changes to the program will be made more frequently if required. For this reason, PNL's Occupational and Environmental Protection Department should be contacted before any Hanford-related environmental dose calculation is performed. This revision of the Hanford Dose Overview Program Report primarily reflects changes made to the data and models used in calculating atmospheric dispersion of airborne effluents at Hanford. The modified data and models are described in detail. In addition, discussions of dose calculation methods and the review of calculation results have been expanded to provide more explicit guidance to the Hanford contractors. 19 references, 30 tables.
Napier, B.A.
1992-12-01
A series of scoping calculations has been undertaken to evaluate the absolute and relative contributions of different radionuclides and exposure pathways to doses that may have been received by individuals living in the vicinity of the Hanford Site. This scoping calculation (Calculation 004) examined the contributions of numerous radionuclides to cumulative dose via environmental exposures and accumulation in foods. Addressed in this calculation were the contributions to organ and effective dose of infants and adults from (1) air submersion and groundshine external dose, (2) inhalation, (3) ingestion of soil by humans, (4) ingestion of leafy vegetables, (5) ingestion of other vegetables and fruits, (6) ingestion of meat, (7) ingestion of eggs, and (8) ingestion of cows` milk from Feeding Regime 1, as described in calculation 002. This calculation specifically addresses cumulative radiation doses to infants and adults resulting from releases occurring over the period 1945 through 1972.
Albright, N; Bergstrom, P M; Daly, T P; Descalle, M; Garrett, D; House, R K; Knapp, D K; May, S; Patterson, R W; Siantar, C L; Verhey, L; Walling, R S; Welczorek, D
1999-07-01
PEREGRINE is a 3D Monte Carlo dose calculation system designed to serve as a dose calculation engine for clinical radiation therapy treatment planning systems. Taking advantage of recent advances in low-cost computer hardware, modern multiprocessor architectures and optimized Monte Carlo transport algorithms, PEREGRINE performs mm-resolution Monte Carlo calculations in times that are reasonable for clinical use. PEREGRINE has been developed to simulate radiation therapy for several source types, including photons, electrons, neutrons and protons, for both teletherapy and brachytherapy. However the work described in this paper is limited to linear accelerator-based megavoltage photon therapy. Here we assess the accuracy, reliability, and added value of 3D Monte Carlo transport for photon therapy treatment planning. Comparisons with clinical measurements in homogeneous and heterogeneous phantoms demonstrate PEREGRINE's accuracy. Studies with variable tissue composition demonstrate the importance of material assignment on the overall dose distribution. Detailed analysis of Monte Carlo results provides new information for radiation research by expanding the set of observables.
NASA Astrophysics Data System (ADS)
Patel, Jalpa A.
The software package "Dosimetry Check" by MathResolutions, LLC, provides an absolute 3D volumetric dose measurement for IMRT QA using the existing Electronic Portal Imaging Device (EPID) mounted on most linear accelerators. This package provides a feedback loop using the patient's treatment planning CT data as the phantom for dose reconstruction. The aim of this work is to study the difference between point, planar and volumetric doses with MapCheck and Dosimetry Check via the use of the EPID and the diode array respectively. Evaluating tools such as point doses at isocenter, 1-D profiles, gamma volume histograms, and dose volume histograms are used for IMRT dose comparison in three types of cases: head and neck, prostate, and lung. Dosimetry Check can be a valuable tool for IMRT QA as it uses patient specific attenuation corrections and the superiority of the EPID as compared to the MapCheck diode array. This helps reduce the uncertainty in dose for less variability in delivery and a more realistic measured vs computed dose verification system as compared to MapCheck.
[An empirical model for calculating electron dose distributions].
Leistner, H; Schüler, W
1990-01-01
Dose-distributions in radiation fields are calculated for purpose of irradiation planning from measured depth dose and cross-distributions predominantly. Especially in electron fields the measuring effort is high to this, because these distributions have to be measured for all occurring irradiation parameters and in many different tissue depths. At the very least it can be shown for the 6...10 MeV electron radiation of the linear accelerator Neptun 10p that all required distributions can be calculated from each separately measured depth dose and cross-distribution. For this depth dose distribution and the measured border decrease of cross-distribution are tabulated and the abscissas are submitted to a linear transformation x' = k.x. In case of depth dose distribution the transformation factor k is dependent on electron energy only and in cross-distribution on tissue depth and source-surface-distance additionally. PMID:2356295
Georgia fishery study: implications for dose calculations. Revision 1
Turcotte, M.D.S.
1983-08-05
Fish consumption will contribute a major portion of the estimated individual and population doses from L-Reactor liquid releases and Cs-137 remobilization in Steel Creek. It is therefore important that the values for fish consumption used in dose calculations be as realistic as possible. Since publication of the L-Reactor Environmental Information Document (EID), data have become available on sport fishing in the Savannah River. These data provide SRP with a site-specific sport fish harvest and consumption values for use in dose calculations. The Georgia fishery data support the total population fish consumption and calculated dose reported in the EID. The data indicate, however, that both the EID average and maximum individual fish consumption have been underestimated, although each to a different degree. The average fish consumption value used in the EID is approximately 3% below the lower limit of the fish consumption range calculated using the Georgia data. Maximum fish consumption in the EID has been underestimated by approximately 60%, and doses to the maximum individual should also be recalculated. Future dose calculations should utilize an average adult fish consumption value of 11.3 kg/yr, and a maximum adult fish consumption value of 34 kg/yr. Consumption values for the teen and child age groups should be increased proportionally: (1) teen average = 8.5; maximum = 25.9 kg/yr; and (2) child average = 3.6; maximum = 11.2 kg/yr. 8 refs.
Neutron absorbed dose determination by calculations of recoil energy.
Wrobel, F; Benabdesselam, M; Iacconi, P; Lapraz, D
2004-01-01
The aim of this work is to calculate the absorbed dose to matter due to neutrons in the 5-150 MeV energy range. Materials involved in the calculations are Al2O3, CaSO4 and CaS, which may be used as dosemeters and have already been studied for their luminescent properties. The absorbed dose is assumed to be mainly due to the energy deposited by the recoils. Elastic reactions are treated with the ECIS code while for the non-elastic ones, a Monte Carlo code has been developed and allowed to follow the nucleus decay and to determine its characteristics (nature and energy). Finally, the calculations show that the absorbed dose is mainly due to non-elastic process and that above 20 MeV this dose decreases slightly with the neutron energy. PMID:15353750
NASA Astrophysics Data System (ADS)
Noblet, C.; Chiavassa, S.; Smekens, F.; Sarrut, D.; Passal, V.; Suhard, J.; Lisbona, A.; Paris, F.; Delpon, G.
2016-05-01
In preclinical studies, the absorbed dose calculation accuracy in small animals is fundamental to reliably investigate and understand observed biological effects. This work investigated the use of the split exponential track length estimator (seTLE), a new kerma based Monte Carlo dose calculation method for preclinical radiotherapy using a small animal precision micro irradiator, the X-RAD 225Cx. Monte Carlo modelling of the irradiator with GATE/GEANT4 was extensively evaluated by comparing measurements and simulations for half-value layer, percent depth dose, off-axis profiles and output factors in water and water-equivalent material for seven circular fields, from 20 mm down to 1 mm in diameter. Simulated and measured dose distributions in cylinders of water obtained for a 360° arc were also compared using dose, distance-to-agreement and gamma-index maps. Simulations and measurements agreed within 3% for all static beam configurations, with uncertainties estimated to 1% for the simulation and 3% for the measurements. Distance-to-agreement accuracy was better to 0.14 mm. For the arc irradiations, gamma-index maps of 2D dose distributions showed that the success rate was higher than 98%, except for the 0.1 cm collimator (92%). Using the seTLE method, MC simulations compute 3D dose distributions within minutes for realistic beam configurations with a clinically acceptable accuracy for beam diameter as small as 1 mm.
Lawrence, R.D.
1983-03-01
A nodal method is developed for the solution of the neutron-diffusion equation in two- and three-dimensional hexagonal geometries. The nodal scheme has been incorporated as an option in the finite-difference diffusion-theory code DIF3D, and is intended for use in the analysis of current LMFBR designs. The nodal equations are derived using higher-order polynomial approximations to the spatial dependence of the flux within the hexagonal-z node. The final equations, which are cast in the form of inhomogeneous response-matrix equations for each energy group, involved spatial moments of the node-interior flux distribution plus surface-averaged partial currents across the faces of the node. These equations are solved using a conventional fission-source iteration accelerated by coarse-mesh rebalance and asymptotic source extrapolation. This report describes the mathematical development and numerical solution of the nodal equations, as well as the use of the nodal option and details concerning its programming structure. This latter information is intended to supplement the information provided in the separate documentation of the DIF3D code.
PLUTONIUM/HIGH-LEVEL VITRIFIED WASTE BDBE DOSE CALCULATION
J.A. Ziegler
2000-11-20
The purpose of this calculation is to provide a dose consequence analysis of high-level waste (HLW) consisting of plutonium immobilized in vitrified HLW to be handled at the proposed Monitored Geologic Repository at Yucca Mountain for a beyond design basis event (BDBE) under expected conditions using best estimate values for each calculation parameter. In addition to the dose calculation, a plutonium respirable particle size for dose calculation use is derived. The current concept for this waste form is plutonium disks enclosed in cans immobilized in canisters of vitrified HLW (i.e., glass). The plutonium inventory at risk used for this calculation is selected from Plutonium Immobilization Project Input for Yucca Mountain Total Systems Performance Assessment (Shaw 1999). The BDBE examined in this calculation is a nonmechanistic initiating event and the sequence of events that follow to cause a radiological release. This analysis will provide the radiological releases and dose consequences for a postulated BDBE. Results may be considered in other analyses to determine or modify the safety classification and quality assurance level of repository structures, systems, and components. This calculation uses best available technical information because the BDBE frequency is very low (i.e., less than 1.0E-6 events/year) and is not required for License Application for the Monitored Geologic Repository. The results of this calculation will not be used as part of a licensing or design basis.
Quantification of Proton Dose Calculation Accuracy in the Lung
Grassberger, Clemens; Daartz, Juliane; Dowdell, Stephen; Ruggieri, Thomas; Sharp, Greg; Paganetti, Harald
2014-06-01
Purpose: To quantify the accuracy of a clinical proton treatment planning system (TPS) as well as Monte Carlo (MC)–based dose calculation through measurements and to assess the clinical impact in a cohort of patients with tumors located in the lung. Methods and Materials: A lung phantom and ion chamber array were used to measure the dose to a plane through a tumor embedded in the lung, and to determine the distal fall-off of the proton beam. Results were compared with TPS and MC calculations. Dose distributions in 19 patients (54 fields total) were simulated using MC and compared to the TPS algorithm. Results: MC increased dose calculation accuracy in lung tissue compared with the TPS and reproduced dose measurements in the target to within ±2%. The average difference between measured and predicted dose in a plane through the center of the target was 5.6% for the TPS and 1.6% for MC. MC recalculations in patients showed a mean dose to the clinical target volume on average 3.4% lower than the TPS, exceeding 5% for small fields. For large tumors, MC also predicted consistently higher V5 and V10 to the normal lung, because of a wider lateral penumbra, which was also observed experimentally. Critical structures located distal to the target could show large deviations, although this effect was highly patient specific. Range measurements showed that MC can reduce range uncertainty by a factor of ∼2: the average (maximum) difference to the measured range was 3.9 mm (7.5 mm) for MC and 7 mm (17 mm) for the TPS in lung tissue. Conclusion: Integration of Monte Carlo dose calculation techniques into the clinic would improve treatment quality in proton therapy for lung cancer by avoiding systematic overestimation of target dose and underestimation of dose to normal lung. In addition, the ability to confidently reduce range margins would benefit all patients by potentially lowering toxicity.
Automatic computed tomography patient dose calculation using DICOM header metadata.
Jahnen, A; Kohler, S; Hermen, J; Tack, D; Back, C
2011-09-01
The present work describes a method that calculates the patient dose values in computed tomography (CT) based on metadata contained in DICOM images in support of patient dose studies. The DICOM metadata is preprocessed to extract necessary calculation parameters. Vendor-specific DICOM header information is harmonized using vendor translation tables and unavailable DICOM tags can be completed with a graphical user interface. CT-Expo, an MS Excel application for calculating the radiation dose, is used to calculate the patient doses. All relevant data and calculation results are stored for further analysis in a relational database. Final results are compiled by utilizing data mining tools. This solution was successfully used for the 2009 CT dose study in Luxembourg. National diagnostic reference levels for standard examinations were calculated based on each of the countries' hospitals. The benefits using this new automatic system saved time as well as resources during the data acquisition and the evaluation when compared with earlier questionnaire-based surveys. PMID:21831868
Srinivas, Challapalli; Kumar, P Suman; Ravichandran, Ramamoorthy; Banerjee, S; Saxena, P.U; Kumar, E.S Arun; Pai, Dinesh K.
2014-01-01
External beam radiotherapy (EBRT) for carcinoma of uterine cervix is a basic line of treatment with three dimensional conformal radiotherapy (3DCRT) in large number of patients. There is need for an established method for verification dosimetry. We tried to document absorbed doses in a group of carcinoma cervix patients by inserting a 0.6 cc Farmer type ion chamber in the vaginal cavity. A special long perspex sleeve cap is designed to cover the chamber for using in the patient's body. Response of ionization chamber is checked earlier in water phantom with and without cap. Treatment planning was carried out with X-ray computed tomography (CT) scan and with the chamber along with cap in inserted position, and with the images Xio treatment planning system. Three measurements on 3 days at 5-6 fraction intervals were recorded in 12 patients. Electrometer measured charges are converted to absorbed dose at the chamber center, in vivo. Our results show good agreement with planned dose within 3% against prescribed dose. This study, is a refinement over our previous studies with transmission dosimetry and chemicals in ampules. This preliminary work shows promise that this can be followed as a routine dose check with special relevance to new protocols in the treatment of carcinoma cervix with EBRT. PMID:25525313
Benchmark of Atucha-2 PHWR RELAP5-3D control rod model by Monte Carlo MCNP5 core calculation
Pecchia, M.; D'Auria, F.; Mazzantini, O.
2012-07-01
Atucha-2 is a Siemens-designed PHWR reactor under construction in the Republic of Argentina. Its geometrical complexity and peculiarities require the adoption of advanced Monte Carlo codes for performing realistic neutronic simulations. Therefore core models of Atucha-2 PHWR were developed using MCNP5. In this work a methodology was set up to collect the flux in the hexagonal mesh by which the Atucha-2 core is represented. The scope of this activity is to evaluate the effect of obliquely inserted control rod on neutron flux in order to validate the RELAP5-3D{sup C}/NESTLE three dimensional neutron kinetic coupled thermal-hydraulic model, applied by GRNSPG/UNIPI for performing selected transients of Chapter 15 FSAR of Atucha-2. (authors)
Verification of IMRT dose calculations using AAA and PBC algorithms in dose buildup regions.
Oinam, Arun S; Singh, Lakhwant
2010-08-26
The purpose of this comparative study was to test the accuracy of anisotropic analytical algorithm (AAA) and pencil beam convolution (PBC) algorithms of Eclipse treatment planning system (TPS) for dose calculations in the low- and high-dose buildup regions. AAA and PBC algorithms were used to create two intensity-modulated radiotherapy (IMRT) plans of the same optimal fluence generated from a clinically simulated oropharynx case in an in-house fabricated head and neck phantom. The TPS computed buildup doses were compared with the corresponding measured doses in the phantom using thermoluminescence dosimeters (TLD 100). Analysis of dose distribution calculated using PBC and AAA shows an increase in gamma value in the dose buildup region indicating large dose deviation. For the surface areas of 1, 50 and 100 cm2, PBC overestimates doses as compared to AAA calculated value in the range of 1.34%-3.62% at 0.6 cm depth, 1.74%-2.96% at 0.4 cm depth, and 1.96%-4.06% at 0.2 cm depth, respectively. In high-dose buildup region, AAA calculated doses were lower by an average of -7.56% (SD = 4.73%), while PBC was overestimated by 3.75% (SD = 5.70%) as compared to TLD measured doses at 0.2 cm depth. However, at 0.4 and 0.6 cm depth, PBC overestimated TLD measured doses by 5.84% (SD = 4.38%) and 2.40% (SD = 4.63%), respectively, while AAA underestimated the TLD measured doses by -0.82% (SD = 4.24%) and -1.10% (SD = 4.14%) at the same respective depth. In low-dose buildup region, both AAA and PBC overestimated the TLD measured doses at all depths except -2.05% (SD = 10.21%) by AAA at 0.2 cm depth. The differences between AAA and PBC at all depths were statistically significant (p < 0.05) in high-dose buildup region, whereas it is not statistically significant in low-dose buildup region. In conclusion, AAA calculated the dose more accurately than PBC in clinically important high-dose buildup region at 0.4 cm and 0.6 cm depths. The use of an orfit cast increases the dose buildup
Napier, B.A.; Farris, W.T.; Simpson, J.C.
1992-12-01
A series of scoping calculations has been undertaken to evaluate the absolute and relative contribution of different radionuclides and exposure pathways to doses that may have been received by individuals living in the vicinity of the Hanford site. This scoping calculation (Calculation 005) examined the contributions of numerous parameters to the uncertainty distribution of doses calculated for environmental exposures and accumulation in foods. This study builds on the work initiated in the first scoping study of iodine in cow`s milk and the third scoping study, which added additional pathways. Addressed in this calculation were the contributions to thyroid dose of infants from (1) air submersion and groundshine external dose, (2) inhalation, (3) ingestion of soil by humans, (4) ingestion of leafy vegetables, (5) ingestion of other vegetables and fruits, (6) ingestion of meat, (7) ingestion of eggs, and (8) ingestion of cows` milk from Feeding Regime 1 as described in Calculation 001.
Onal, C; Topkan, E; Efe, E; Yavuz, M; Arslan, G; Yavuz, A
2009-01-01
In this study, we investigated the shrinking effect of concurrent three-dimensional conformal radiotherapy (3D-CRT) and androgen deprivation (AD) on prostate volume, and its possible impact on the dose received by the rectum and bladder during the course of 3D-CRT. The difference between the prostatic volumes determined on pre-treatment planning CT (PL-CT) and post-treatment CT (PT-CT) following a 3D-CRT course was assessed in 52 patients with localised prostate carcinoma. The changes in mean prostate volume when compared with PL-CT and PT-CT-based measurements were assessed. The pre- and post-treatment mean prostate volumes for the whole study population were 49.7 cm3 and 41.0 cm3 (p _ 0.02), respectively. The study cohort was divided into two groups depending on the duration of neoadjuvant androgen deprivation (NAD): 23 patients (44.7%) were designated as “short NAD” (≤3 months; SNAD) and the remaining 29 (55.3%) as “long NAD” (>3 months; LNAD). Patients on SNAD experienced a significantly greater reduction in prostate volume compared with those on LNAD (14.1% vs 5.1%; p _ 0.03). A significant increase in rectum V40–60 values in PT-CT compared with PL-CT was demonstrated. LNAD patients had significantly higher rectal V50–70 values at PT-CT compared with the SNAD group. There was a significant decline in V30–V75 bladder values in PT-CT compared with PL-CT in the SNAD group. In conclusion, a higher prostate volume reduction during 3D-CRT was demonstrated when RT planning was performed within 3 months of NAD. However, this reduction and daily organ motion may lead to an unpredictable increase in rectal doses. PMID:19581310
NASA Astrophysics Data System (ADS)
Hrinivich, W. Thomas; Hoover, Douglas A.; Surry, Kathleen; Edirisinghe, Chandima; Montreuil, Jacques; D'Souza, David; Fenster, Aaron; Wong, Eugene
2016-03-01
Background: High-dose-rate brachytherapy (HDR-BT) is a prostate cancer treatment option involving the insertion of hollow needles into the gland through the perineum to deliver a radioactive source. Conventional needle imaging involves indexing a trans-rectal ultrasound (TRUS) probe in the superior/inferior (S/I) direction, using the axial transducer to produce an image set for organ segmentation. These images have limited resolution in the needle insertion direction (S/I), so the sagittal transducer is used to identify needle tips, requiring a manual registration with the axial view. This registration introduces a source of uncertainty in the final segmentations and subsequent treatment plan. Our lab has developed a device enabling 3D-TRUS guided insertions with high S/I spatial resolution, eliminating the need to align axial and sagittal views. Purpose: To compare HDR-BT needle tip localization accuracy between 2D and 3D-TRUS. Methods: 5 prostate cancer patients underwent conventional 2D TRUS guided HDR-BT, during which 3D images were also acquired for post-operative registration and segmentation. Needle end-length measurements were taken, providing a gold standard for insertion depths. Results: 73 needles were analyzed from all 5 patients. Needle tip position differences between imaging techniques was found to be largest in the S/I direction with mean+/-SD of -2.5+/-4.0 mm. End-length measurements indicated that 3D TRUS provided statistically significantly lower mean+/-SD insertion depth error of -0.2+/-3.4 mm versus 2.3+/-3.7 mm with 2D guidance (p < .001). Conclusions: 3D TRUS may provide more accurate HDR-BT needle localization than conventional 2D TRUS guidance for the majority of HDR-BT needles.
Macro Monte Carlo for dose calculation of proton beams
NASA Astrophysics Data System (ADS)
Fix, Michael K.; Frei, Daniel; Volken, Werner; Born, Ernst J.; Aebersold, Daniel M.; Manser, Peter
2013-04-01
Although the Monte Carlo (MC) method allows accurate dose calculation for proton radiotherapy, its usage is limited due to long computing time. In order to gain efficiency, a new macro MC (MMC) technique for proton dose calculations has been developed. The basic principle of the MMC transport is a local to global MC approach. The local simulations using GEANT4 consist of mono-energetic proton pencil beams impinging perpendicularly on slabs of different thicknesses and different materials (water, air, lung, adipose, muscle, spongiosa, cortical bone). During the local simulation multiple scattering, ionization as well as elastic and inelastic interactions have been taken into account and the physical characteristics such as lateral displacement, direction distributions and energy loss have been scored for primary and secondary particles. The scored data from appropriate slabs is then used for the stepwise transport of the protons in the MMC simulation while calculating the energy loss along the path between entrance and exit position. Additionally, based on local simulations the radiation transport of neutrons and the generated ions are included into the MMC simulations for the dose calculations. In order to validate the MMC transport, calculated dose distributions using the MMC transport and GEANT4 have been compared for different mono-energetic proton pencil beams impinging on different phantoms including homogeneous and inhomogeneous situations as well as on a patient CT scan. The agreement of calculated integral depth dose curves is better than 1% or 1 mm for all pencil beams and phantoms considered. For the dose profiles the agreement is within 1% or 1 mm in all phantoms for all energies and depths. The comparison of the dose distribution calculated using either GEANT4 or MMC in the patient also shows an agreement of within 1% or 1 mm. The efficiency of MMC is up to 200 times higher than for GEANT4. The very good level of agreement in the dose comparisons
Calculation of the biological effective dose for piecewise defined dose-rate fits
Hobbs, Robert F.; Sgouros, George
2009-03-15
An algorithmic solution to the biological effective dose (BED) calculation from the Lea-Catcheside formula for a piecewise defined function is presented. Data from patients treated for metastatic thyroid cancer were used to illustrate the solution. The Lea-Catcheside formula for the G-factor of the BED is integrated numerically using a large number of small trapezoidal fits to each integral. The algorithmically calculated BED is compatible with an analytic calculation for a similarly valued exponentially fitted dose-rate plot and is the only resolution for piecewise defined dose-rate functions.
An empirical model for calculation of the collimator contamination dose in therapeutic proton beams.
Vidal, M; De Marzi, L; Szymanowski, H; Guinement, L; Nauraye, C; Hierso, E; Freud, N; Ferrand, R; François, P; Sarrut, D
2016-02-21
Collimators are used as lateral beam shaping devices in proton therapy with passive scattering beam lines. The dose contamination due to collimator scattering can be as high as 10% of the maximum dose and influences calculation of the output factor or monitor units (MU). To date, commercial treatment planning systems generally use a zero-thickness collimator approximation ignoring edge scattering in the aperture collimator and few analytical models have been proposed to take scattering effects into account, mainly limited to the inner collimator face component. The aim of this study was to characterize and model aperture contamination by means of a fast and accurate analytical model. The entrance face collimator scatter distribution was modeled as a 3D secondary dose source. Predicted dose contaminations were compared to measurements and Monte Carlo simulations. Measurements were performed on two different proton beam lines (a fixed horizontal beam line and a gantry beam line) with divergent apertures and for several field sizes and energies. Discrepancies between analytical algorithm dose prediction and measurements were decreased from 10% to 2% using the proposed model. Gamma-index (2%/1 mm) was respected for more than 90% of pixels. The proposed analytical algorithm increases the accuracy of analytical dose calculations with reasonable computation times.
An empirical model for calculation of the collimator contamination dose in therapeutic proton beams
NASA Astrophysics Data System (ADS)
Vidal, M.; De Marzi, L.; Szymanowski, H.; Guinement, L.; Nauraye, C.; Hierso, E.; Freud, N.; Ferrand, R.; François, P.; Sarrut, D.
2016-02-01
Collimators are used as lateral beam shaping devices in proton therapy with passive scattering beam lines. The dose contamination due to collimator scattering can be as high as 10% of the maximum dose and influences calculation of the output factor or monitor units (MU). To date, commercial treatment planning systems generally use a zero-thickness collimator approximation ignoring edge scattering in the aperture collimator and few analytical models have been proposed to take scattering effects into account, mainly limited to the inner collimator face component. The aim of this study was to characterize and model aperture contamination by means of a fast and accurate analytical model. The entrance face collimator scatter distribution was modeled as a 3D secondary dose source. Predicted dose contaminations were compared to measurements and Monte Carlo simulations. Measurements were performed on two different proton beam lines (a fixed horizontal beam line and a gantry beam line) with divergent apertures and for several field sizes and energies. Discrepancies between analytical algorithm dose prediction and measurements were decreased from 10% to 2% using the proposed model. Gamma-index (2%/1 mm) was respected for more than 90% of pixels. The proposed analytical algorithm increases the accuracy of analytical dose calculations with reasonable computation times.
An empirical model for calculation of the collimator contamination dose in therapeutic proton beams.
Vidal, M; De Marzi, L; Szymanowski, H; Guinement, L; Nauraye, C; Hierso, E; Freud, N; Ferrand, R; François, P; Sarrut, D
2016-02-21
Collimators are used as lateral beam shaping devices in proton therapy with passive scattering beam lines. The dose contamination due to collimator scattering can be as high as 10% of the maximum dose and influences calculation of the output factor or monitor units (MU). To date, commercial treatment planning systems generally use a zero-thickness collimator approximation ignoring edge scattering in the aperture collimator and few analytical models have been proposed to take scattering effects into account, mainly limited to the inner collimator face component. The aim of this study was to characterize and model aperture contamination by means of a fast and accurate analytical model. The entrance face collimator scatter distribution was modeled as a 3D secondary dose source. Predicted dose contaminations were compared to measurements and Monte Carlo simulations. Measurements were performed on two different proton beam lines (a fixed horizontal beam line and a gantry beam line) with divergent apertures and for several field sizes and energies. Discrepancies between analytical algorithm dose prediction and measurements were decreased from 10% to 2% using the proposed model. Gamma-index (2%/1 mm) was respected for more than 90% of pixels. The proposed analytical algorithm increases the accuracy of analytical dose calculations with reasonable computation times. PMID:26816191
Impact of dose calculation algorithm on radiation therapy
Chen, Wen-Zhou; Xiao, Ying; Li, Jun
2014-01-01
The quality of radiation therapy depends on the ability to maximize the tumor control probability while minimize the normal tissue complication probability. Both of these two quantities are directly related to the accuracy of dose distributions calculated by treatment planning systems. The commonly used dose calculation algorithms in the treatment planning systems are reviewed in this work. The accuracy comparisons among these algorithms are illustrated by summarizing the highly cited research papers on this topic. Further, the correlation between the algorithms and tumor control probability/normal tissue complication probability values are manifested by several recent studies from different groups. All the cases demonstrate that dose calculation algorithms play a vital role in radiation therapy. PMID:25431642
NASA Astrophysics Data System (ADS)
Meier, G.; Besson, R.; Nanz, A.; Safai, S.; Lomax, A. J.
2015-04-01
Pencil beam scanning proton therapy allows the delivery of highly conformal dose distributions by delivering several thousand pencil beams. These beams have to be individually optimised and accurately delivered requiring a significant quality assurance workload. In this work we describe a toolkit for independent dose calculations developed at Paul Scherrer Institut which allows for dose reconstructions at several points in the treatment workflow. Quality assurance based on reconstructed dose distributions was shown to be favourable to pencil beam by pencil beam comparisons for the detection of delivery uncertainties and estimation of their effects. Furthermore the dose reconstructions were shown to have a sensitivity of the order of or higher than the measurements currently employed in the clinical verification procedures. The design of the independent dose calculation tool allows for a high modifiability of the dose calculation parameters (e.g. depth dose profiles, angular spatial distributions) allowing for a safe environment outside of the clinical treatment planning system for investigating the effect of such parameters on the resulting dose distributions and thus distinguishing between different contributions to measured dose deviations. The presented system could potentially reduce the amount of patient-specific quality assurance measurements which currently constitute a bottleneck in the clinical workflow.
Meier, G; Besson, R; Nanz, A; Safai, S; Lomax, A J
2015-04-01
Pencil beam scanning proton therapy allows the delivery of highly conformal dose distributions by delivering several thousand pencil beams. These beams have to be individually optimised and accurately delivered requiring a significant quality assurance workload. In this work we describe a toolkit for independent dose calculations developed at Paul Scherrer Institut which allows for dose reconstructions at several points in the treatment workflow. Quality assurance based on reconstructed dose distributions was shown to be favourable to pencil beam by pencil beam comparisons for the detection of delivery uncertainties and estimation of their effects. Furthermore the dose reconstructions were shown to have a sensitivity of the order of or higher than the measurements currently employed in the clinical verification procedures. The design of the independent dose calculation tool allows for a high modifiability of the dose calculation parameters (e.g. depth dose profiles, angular spatial distributions) allowing for a safe environment outside of the clinical treatment planning system for investigating the effect of such parameters on the resulting dose distributions and thus distinguishing between different contributions to measured dose deviations. The presented system could potentially reduce the amount of patient-specific quality assurance measurements which currently constitute a bottleneck in the clinical workflow. PMID:25779992
Beta and gamma dose calculations for PWR and BWR containments
King, D.B.
1989-07-01
Analyses of gamma and beta dose in selected regions in PWR and BWR containment buildings have been performed for a range of fission product releases from selected severe accidents. The objective of this study was to determine the radiation dose that safety-related equipment could experience during the selected severe accident sequences. The resulting dose calculations demonstrate the extent to which design basis accident qualified equipment could also be qualified for the severe accident environments. Surry was chosen as the representative PWR plant while Peach Bottom was selected to represent BWRs. Battelle Columbus Laboratory performed the source term release analyses. The AB epsilon scenario (an intermediate to large LOCA with failure to recover onsite or offsite electrical power) was selected as the base case Surry accident, and the AE scenario (a large break LOCA with one initiating event and a combination of failures in two emergency cooling systems) was selected as the base case Peach Bottom accident. Radionuclide release was bounded for both scenarios by including spray operation and arrested sequences as variations of the base scenarios. Sandia National Laboratories used the source terms to calculate dose to selected containment regions. Scenarios with sprays operational resulted in a total dose comparable to that (2.20 /times/ 10/sup 8/ rads) used in current equipment qualification testing. The base case scenarios resulted in some calculated doses roughly an order of magnitude above the current 2.20 /times/ 10/sup 8/ rad equipment qualification test region. 8 refs., 23 figs., 12 tabs.
Khaled, Shaban A; Burley, Jonathan C; Alexander, Morgan R; Yang, Jing; Roberts, Clive J
2015-11-10
We have used three dimensional (3D) extrusion printing to manufacture a multi-active solid dosage form or so called polypill. This contains five compartmentalised drugs with two independently controlled and well-defined release profiles. This polypill demonstrates that complex medication regimes can be combined in a single personalised tablet. This could potentially improve adherence for those patients currently taking many separate tablets and also allow ready tailoring of a particular drug combination/drug release for the needs of an individual. The polypill here represents a cardiovascular treatment regime with the incorporation of an immediate release compartment with aspirin and hydrochlorothiazide and three sustained release compartments containing pravastatin, atenolol, and ramipril. X-ray powder diffraction (XRPD) and Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) were used to assess drug-excipient interaction. The printed polypills were evaluated for drug release using USP dissolution testing. We found that the polypill showed the intended immediate and sustained release profiles based upon the active/excipient ratio used. PMID:26390808
Sci—Thur AM: YIS - 06: An EPID-based 3D patient dose verification method for SBRT-VMAT delivery
McCowan, P.; Uytven, E van; Beek, T van; McCurdy, B
2014-08-15
Purpose: Stereotactic body radiation therapy (SBRT) delivered via volumetric modulated arc therapy (VMAT) can strongly benefit from an in vivo patient dose verification due to the large doses per fraction. Electronic portal imaging devices (EPIDs) can be utilized as a patient dose dosimeter. In this work we present a physics-based model which utilizes on-treatment EPID images to reconstruct the dose delivered to an anthropomorphic phantom during SBRT-VMAT delivery. Methods: An SBRT linac beam was modeled using Monte Carlo methods and verified with measured data. Our dose reconstruction model back-projects EPID measured focal fluence upstream of the patient and adds a predicted extra-focal fluence component. This fluence is forward projected onto the patient's density matrix and convolved with dose kernels to calculate dose. The model was validated for two prostate, three lung, and two spine SBRT-VMAT treatments. Results were compared to the treatment planning system's calculation. Results: 2%/2 mm chi comparison calculations gave pass rates for the whole volume, infield, and high dose region respectively, and no lower than: 98%, 95%, 99% for the prostate plans, 99%, 92%, 85% for the lung plans, and 91%, 85%, 81% for the spine plans. A 3%/3mm calculation gave pass rates no lower than 99%, 94%, and 90% for all dose regions for the prostate, lung, and spine respectively. Conclusions: We have developed a physics-based model which calculates delivered dose to phantom (or patient) for SBRT-VMAT delivery using on treatment EPID images. The accuracy of the results has allowed us to test this model clinically.
Russell, Kellie R.; Carlsson Tedgren, Aasa K.; Ahnesjoe, Anders
2005-09-15
In brachytherapy, tissue heterogeneities, source shielding, and finite patient/phantom extensions affect both the primary and scatter dose distributions. The primary dose is, due to the short range of secondary electrons, dependent only on the distribution of material located on the ray line between the source and dose deposition site. The scatter dose depends on both the direct irradiation pattern and the distribution of material in a large volume surrounding the point of interest, i.e., a much larger volume must be included in calculations to integrate many small dose contributions. It is therefore of interest to consider different methods for the primary and the scatter dose calculation to improve calculation accuracy with limited computer resources. The algorithms in present clinical use ignore these effects causing systematic dose errors in brachytherapy treatment planning. In this work we review a primary and scatter dose separation formalism (PSS) for brachytherapy source characterization to support separate calculation of the primary and scatter dose contributions. We show how the resulting source characterization data can be used to drive more accurate dose calculations using collapsed cone superposition for scatter dose calculations. Two types of source characterization data paths are used: a direct Monte Carlo simulation in water phantoms with subsequent parameterization of the results, and an alternative data path built on processing of AAPM TG43 formatted data to provide similar parameter sets. The latter path is motivated of the large amounts of data already existing in the TG43 format. We demonstrate the PSS methods using both data paths for a clinical {sup 192}Ir source. Results are shown for two geometries: a finite but homogeneous water phantom, and a half-slab consisting of water and air. The dose distributions are compared to results from full Monte Carlo simulations and we show significant improvement in scatter dose calculations when the
Monte Carlo dose calculation in dental amalgam phantom.
Aziz, Mohd Zahri Abdul; Yusoff, A L; Osman, N D; Abdullah, R; Rabaie, N A; Salikin, M S
2015-01-01
It has become a great challenge in the modern radiation treatment to ensure the accuracy of treatment delivery in electron beam therapy. Tissue inhomogeneity has become one of the factors for accurate dose calculation, and this requires complex algorithm calculation like Monte Carlo (MC). On the other hand, computed tomography (CT) images used in treatment planning system need to be trustful as they are the input in radiotherapy treatment. However, with the presence of metal amalgam in treatment volume, the CT images input showed prominent streak artefact, thus, contributed sources of error. Hence, metal amalgam phantom often creates streak artifacts, which cause an error in the dose calculation. Thus, a streak artifact reduction technique was applied to correct the images, and as a result, better images were observed in terms of structure delineation and density assigning. Furthermore, the amalgam density data were corrected to provide amalgam voxel with accurate density value. As for the errors of dose uncertainties due to metal amalgam, they were reduced from 46% to as low as 2% at d80 (depth of the 80% dose beyond Zmax) using the presented strategies. Considering the number of vital and radiosensitive organs in the head and the neck regions, this correction strategy is suggested in reducing calculation uncertainties through MC calculation.
Ono, K; Fujimoto, S; Akagi, Y; Hirokawa, Y; Hayashi, S; Miyazawa, M
2014-06-01
Purpose: The aim of this dosimetric study was to develop 3D dose verification system for volumetric modulated arc therapy (VMAT) using polyacrylamide-based gel (PAGAT) dosimeter improved the sensitivity by magnesium chloride (MgCl{sub 2}). Methods: PAGAT gel containing MgCl{sub 2} as a sensitizer was prepared in this study. Methacrylic-acid-based gel (MAGAT) was also prepared to compare the dosimetric characteristics with PAGAT gel. The cylindrical glass vials (4 cm diameter, 12 cm length) filled with each polymer gel were irradiated with 6 MV photon beam using Novalis Tx linear accelerator (Varian/BrainLAB). The irradiated polymer gel dosimeters were scanned with Signa 1.5 T MRI system (GE), and dose calibration curves were obtained using T{sub 2} relaxation rate (R{sub 2} = 1/T{sub 2}). Dose rate (100-600 MU min{sup −1}) and fractionation (1-8 fractions) were varied. In addition, a cubic acrylic phantom (10 × 10 × 10 cm{sup 3}) filled with improved PAGAT gel inserted into the IMRT phantom (IBA) was irradiated with VMAT (RapidArc). C-shape structure was used for the VMAT planning by the Varian Eclipse treatment planning system (TPS). The dose comparison of TPS and measurements with the polymer gel dosimeter was accomplished by the gamma index analysis, overlaying the dose profiles for a set of data on selected planes using in-house developed software. Results: Dose rate and fractionation dependence of improved PAGAT gel were smaller than MAGAT gel. A high similarity was found by overlaying the dose profiles measured with improved PAGAT gel dosimeter and the TPS dose, and the mean pass rate of the gamma index analysis using 3%/3 mm criteria was achieved 90% on orthogonal planes for VMAT using improved PAGAT gel dosimeter. Conclusion: In-house developed 3D dose verification system using improved polyacrylamide-based gel dosimeter had a potential as an effective tool for VMAT QA.
Benchmarking analytical calculations of proton doses in heterogeneous matter
Ciangaru, George; Polf, Jerimy C.; Bues, Martin; Smith, Alfred R.
2005-12-15
A proton dose computational algorithm, performing an analytical superposition of infinitely narrow proton beamlets (ASPB) is introduced. The algorithm uses the standard pencil beam technique of laterally distributing the central axis broad beam doses according to the Moliere scattering theory extended to slablike varying density media. The purpose of this study was to determine the accuracy of our computational tool by comparing it with experimental and Monte Carlo (MC) simulation data as benchmarks. In the tests, parallel wide beams of protons were scattered in water phantoms containing embedded air and bone materials with simple geometrical forms and spatial dimensions of a few centimeters. For homogeneous water and bone phantoms, the proton doses we calculated with the ASPB algorithm were found very comparable to experimental and MC data. For layered bone slab inhomogeneity in water, the comparison between our analytical calculation and the MC simulation showed reasonable agreement, even when the inhomogeneity was placed at the Bragg peak depth. There also was reasonable agreement for the parallelepiped bone block inhomogeneity placed at various depths, except for cases in which the bone was located in the region of the Bragg peak, when discrepancies were as large as more than 10%. When the inhomogeneity was in the form of abutting air-bone slabs, discrepancies of as much as 8% occurred in the lateral dose profiles on the air cavity side of the phantom. Additionally, the analytical depth-dose calculations disagreed with the MC calculations within 3% of the Bragg peak dose, at the entry and midway depths in the phantom. The distal depth-dose 20%-80% fall-off widths and ranges calculated with our algorithm and the MC simulation were generally within 0.1 cm of agreement. The analytical lateral-dose profile calculations showed smaller (by less than 0.1 cm) 20%-80% penumbra widths and shorter fall-off tails than did those calculated by the MC simulations. Overall
Benchmarking analytical calculations of proton doses in heterogeneous matter.
Ciangaru, George; Polf, Jerimy C; Bues, Martin; Smith, Alfred R
2005-12-01
A proton dose computational algorithm, performing an analytical superposition of infinitely narrow proton beamlets (ASPB) is introduced. The algorithm uses the standard pencil beam technique of laterally distributing the central axis broad beam doses according to the Moliere scattering theory extended to slablike varying density media. The purpose of this study was to determine the accuracy of our computational tool by comparing it with experimental and Monte Carlo (MC) simulation data as benchmarks. In the tests, parallel wide beams of protons were scattered in water phantoms containing embedded air and bone materials with simple geometrical forms and spatial dimensions of a few centimeters. For homogeneous water and bone phantoms, the proton doses we calculated with the ASPB algorithm were found very comparable to experimental and MC data. For layered bone slab inhomogeneity in water, the comparison between our analytical calculation and the MC simulation showed reasonable agreement, even when the inhomogeneity was placed at the Bragg peak depth. There also was reasonable agreement for the parallelepiped bone block inhomogeneity placed at various depths, except for cases in which the bone was located in the region of the Bragg peak, when discrepancies were as large as more than 10%. When the inhomogeneity was in the form of abutting air-bone slabs, discrepancies of as much as 8% occurred in the lateral dose profiles on the air cavity side of the phantom. Additionally, the analytical depth-dose calculations disagreed with the MC calculations within 3% of the Bragg peak dose, at the entry and midway depths in the phantom. The distal depth-dose 20%-80% fall-off widths and ranges calculated with our algorithm and the MC simulation were generally within 0.1 cm of agreement. The analytical lateral-dose profile calculations showed smaller (by less than 0.1 cm) 20%-80% penumbra widths and shorter fall-off tails than did those calculated by the MC simulations. Overall
NASA Technical Reports Server (NTRS)
Walitt, L.
1982-01-01
The VANS successive approximation numerical method was extended to the computation of three dimensional, viscous, transonic flows in turbomachines. A cross-sectional computer code, which conserves mass flux at each point of the cross-sectional surface of computation was developed. In the VANS numerical method, the cross-sectional computation follows a blade-to-blade calculation. Numerical calculations were made for an axial annular turbine cascade and a transonic, centrifugal impeller with splitter vanes. The subsonic turbine cascade computation was generated in blade-to-blade surface to evaluate the accuracy of the blade-to-blade mode of marching. Calculated blade pressures at the hub, mid, and tip radii of the cascade agreed with corresponding measurements. The transonic impeller computation was conducted to test the newly developed locally mass flux conservative cross-sectional computer code. Both blade-to-blade and cross sectional modes of calculation were implemented for this problem. A triplet point shock structure was computed in the inducer region of the impeller. In addition, time-averaged shroud static pressures generally agreed with measured shroud pressures. It is concluded that the blade-to-blade computation produces a useful engineering flow field in regions of subsonic relative flow; and cross-sectional computation, with a locally mass flux conservative continuity equation, is required to compute the shock waves in regions of supersonic relative flow.
Analytical probabilistic proton dose calculation and range uncertainties
NASA Astrophysics Data System (ADS)
Bangert, M.; Hennig, P.; Oelfke, U.
2014-03-01
We introduce the concept of analytical probabilistic modeling (APM) to calculate the mean and the standard deviation of intensity-modulated proton dose distributions under the influence of range uncertainties in closed form. For APM, range uncertainties are modeled with a multivariate Normal distribution p(z) over the radiological depths z. A pencil beam algorithm that parameterizes the proton depth dose d(z) with a weighted superposition of ten Gaussians is used. Hence, the integrals ∫ dz p(z) d(z) and ∫ dz p(z) d(z)2 required for the calculation of the expected value and standard deviation of the dose remain analytically tractable and can be efficiently evaluated. The means μk, widths δk, and weights ωk of the Gaussian components parameterizing the depth dose curves are found with least squares fits for all available proton ranges. We observe less than 0.3% average deviation of the Gaussian parameterizations from the original proton depth dose curves. Consequently, APM yields high accuracy estimates for the expected value and standard deviation of intensity-modulated proton dose distributions for two dimensional test cases. APM can accommodate arbitrary correlation models and account for the different nature of random and systematic errors in fractionated radiation therapy. Beneficial applications of APM in robust planning are feasible.
Tissue heterogeneity in IMRT dose calculation for lung cancer.
Pasciuti, Katia; Iaccarino, Giuseppe; Strigari, Lidia; Malatesta, Tiziana; Benassi, Marcello; Di Nallo, Anna Maria; Mirri, Alessandra; Pinzi, Valentina; Landoni, Valeria
2011-01-01
The aim of this study was to evaluate the differences in accuracy of dose calculation between 3 commonly used algorithms, the Pencil Beam algorithm (PB), the Anisotropic Analytical Algorithm (AAA), and the Collapsed Cone Convolution Superposition (CCCS) for intensity-modulated radiation therapy (IMRT). The 2D dose distributions obtained with the 3 algorithms were compared on each CT slice pixel by pixel, using the MATLAB code (The MathWorks, Natick, MA) and the agreement was assessed with the γ function. The effect of the differences on dose-volume histograms (DVHs), tumor control, and normal tissue complication probability (TCP and NTCP) were also evaluated, and its significance was quantified by using a nonparametric test. In general PB generates regions of over-dosage both in the lung and in the tumor area. These differences are not always in DVH of the lung, although the Wilcoxon test indicated significant differences in 2 of 4 patients. Disagreement in the lung region was also found when the Γ analysis was performed. The effect on TCP is less important than for NTCP because of the slope of the curve at the level of the dose of interest. The effect of dose calculation inaccuracy is patient-dependent and strongly related to beam geometry and to the localization of the tumor. When multiple intensity-modulated beams are used, the effect of the presence of the heterogeneity on dose distribution may not always be easily predictable. PMID:20970989
Bai, T; Yan, H; Shi, F; Jia, X; Jiang, Steve B.; Lou, Y; Xu, Q; Mou, X
2014-06-15
Purpose: To develop a 3D dictionary learning based statistical reconstruction algorithm on graphic processing units (GPU), to improve the quality of low-dose cone beam CT (CBCT) imaging with high efficiency. Methods: A 3D dictionary containing 256 small volumes (atoms) of 3x3x3 voxels was trained from a high quality volume image. During reconstruction, we utilized a Cholesky decomposition based orthogonal matching pursuit algorithm to find a sparse representation on this dictionary basis of each patch in the reconstructed image, in order to regularize the image quality. To accelerate the time-consuming sparse coding in the 3D case, we implemented our algorithm in a parallel fashion by taking advantage of the tremendous computational power of GPU. Evaluations are performed based on a head-neck patient case. FDK reconstruction with full dataset of 364 projections is used as the reference. We compared the proposed 3D dictionary learning based method with a tight frame (TF) based one using a subset data of 121 projections. The image qualities under different resolutions in z-direction, with or without statistical weighting are also studied. Results: Compared to the TF-based CBCT reconstruction, our experiments indicated that 3D dictionary learning based CBCT reconstruction is able to recover finer structures, to remove more streaking artifacts, and is less susceptible to blocky artifacts. It is also observed that statistical reconstruction approach is sensitive to inconsistency between the forward and backward projection operations in parallel computing. Using high a spatial resolution along z direction helps improving the algorithm robustness. Conclusion: 3D dictionary learning based CBCT reconstruction algorithm is able to sense the structural information while suppressing noise, and hence to achieve high quality reconstruction. The GPU realization of the whole algorithm offers a significant efficiency enhancement, making this algorithm more feasible for potential
Khailov, A.M.; Ivannikov, A. I.; Skvortsov, V.G.; Stepanenko, V.F.; Orlenko, S.P.; Flood, A.B.; Williams, B.B.; Swartz, H.M.
2015-01-01
Absorbed doses to fingernails and organs were calculated for a set of homogenous external gamma-ray irradiation geometries in air. The doses were obtained by stochastic modeling of the ionizing particle transport (Monte Carlo method) for a mathematical human phantom with arms and hands placed loosely along the sides of the body. The resulting dose conversion factors for absorbed doses in fingernails can be used to assess the dose distribution and magnitude in practical dose reconstruction problems. For purposes of estimating dose in a large population exposed to radiation in order to triage people for treatment of acute radiation syndrome, the calculated data for a range of energies having a width of from 0.05 to 3.5 MeV were used to convert absorbed doses in fingernails to corresponding doses in organs and the whole body as well as the effective dose. Doses were assessed based on assumed rates of radioactive fallout at different time periods following a nuclear explosion. PMID:26347593
An Efficient Method for Heavy Ion Dose Calculations
Dandini, Vincent J.; Prinja, Anil K.
1997-06-01
Heavy charged particles deposit much of their kinetic energy at very high rates in small volumes near the end of their range. This characteristic, coupled with the availability of modern particle accelerators, has sparked a revival of interest in the use of ions as a possible treatment tool for certain types of cancers. Collisions between projectile ions and atoms in the target medium can result in ion fragments that are different from the original projectile species. The energy deposition characteristics of these fragments differ from those of the projectile in a manner that allows them to travel beyond the range of the original particle. This can result in deposition of doses in healthy tissue beyond the tumor. The loss of projectiles due to the fragmentation process will also affect the dose deposited in the target tumor. An accurate dose calculation requires that these effects be taken into account. Monte Carlo calculations are expensive, time consuming, and can be limited in the number of ion species considered. Linear methods can yield high-order accuracy but can sometimes exhibit the undesirable characteristic of calculating negative fluxes. In order to bypass these difficulties, we have applied the recently developed exponential discontinuous (ED) finite- element method to a calculation of dose deposition by relativistic heavy ion projectiles and fragments. The ED method has been shown to yield strictly -- positive solutions for positive sources of neutral particles.
Touch screen man machine interfere for emergency dose calculations
Woodard, K.; Abrams, M.
1987-01-01
Emergency dose calculation systems generally use a keyboard to provide the interface between the user and the computer. This interface is preferred by users who work daily with computers; however, for many plant personnel who are not continuously involved with computer operations, the use of a keyboard can be cumbersome and time consuming. This is particularly true when the user is under pressure during a drill or an actual emergency. Experience in many applications of Pickard, Lowe and Garrick's PLG's Meteorological Information and Dose Assessment System (MIDAS) has shown that user friendliness is a key ingredient toward achieving acceptance of computerized systems. Hardware to support to touch screen interface is now available and has been implemented in MIDAS. Recent experience has demonstrated that selection times for dose calculations are reduced, data entry errors have been minimized, and confusion over appropriate entries has been avoided due to the built-in logic. A 10-yr search for an acceptable keyboard replacement has ended.
A simplified analytical random walk model for proton dose calculation
NASA Astrophysics Data System (ADS)
Yao, Weiguang; Merchant, Thomas E.; Farr, Jonathan B.
2016-10-01
We propose an analytical random walk model for proton dose calculation in a laterally homogeneous medium. A formula for the spatial fluence distribution of primary protons is derived. The variance of the spatial distribution is in the form of a distance-squared law of the angular distribution. To improve the accuracy of dose calculation in the Bragg peak region, the energy spectrum of the protons is used. The accuracy is validated against Monte Carlo simulation in water phantoms with either air gaps or a slab of bone inserted. The algorithm accurately reflects the dose dependence on the depth of the bone and can deal with small-field dosimetry. We further applied the algorithm to patients’ cases in the highly heterogeneous head and pelvis sites and used a gamma test to show the reasonable accuracy of the algorithm in these sites. Our algorithm is fast for clinical use.
NASA Astrophysics Data System (ADS)
Zhang, He
2013-01-01
The space charge effect is one of the most important collective effects in beam dynamic studies. In many cases, numerical simulations are inevitable in order to get a clear understanding of this effect. The particle-particle interaction algorithms and the article-in-cell algorithms are widely used in space charge effect simulations. But they both have difficulties in dealing with highly correlated beams with abnormal distributions or complicated geometries. We developed a new algorithm to calculate the three dimensional self-field between charged particles by combining the differential algebra (DA) techniques with the fast multi-pole method (FMM). The FMM hierarchically decomposes the whole charged domain into many small regions. For each region it uses multipole expansions to represent the potential/field contributions from the particles far away from the region and then converts the multipole expansions into a local expansion inside the region. The potential/field due to the far away particles is calculated from the expansions and the potential/field due to the nearby particles is calculated from the Coulomb force law. The DA techniques are used in the calculation, translation and converting of the expansions. The new algorithm scales linearly with the total number of particles and it is suitable for any arbitrary charge distribution. Using the DA techniques, we can calculate both the potential/field and its high order derivatives, which will be useful for the purpose of including the space charge effect into transfer maps in the future. We first present the single level FMM, which decomposes the whole domain into boxes of the same size. It works best for charge distributions that are not overly non-uniform. Then we present the multilevel fast multipole algorithm (MLFMA), which decomposes the whole domain into different sized boxes according to the charge density. Finer boxes are generated where the higher charge density exists; thus the algorithm works for any
NASA Astrophysics Data System (ADS)
Dzhalandinov, A.; Tsofin, V.; Kochkin, V.; Panferov, P.; Timofeev, A.; Reshetnikov, A.; Makhotin, D.; Erak, D.; Voloschenko, A.
2016-02-01
Usually the synthesis of two-dimensional and one-dimensional discrete ordinate calculations is used to evaluate neutron fluence on VVER-1000 reactor pressure vessel (RPV) for prognosis of radiation embrittlement. But there are some cases when this approach is not applicable. For example the latest projects of VVER-1000 have upgraded surveillance program. Containers with surveillance specimens are located on the inner surface of RPV with fast neutron flux maximum. Therefore, the synthesis approach is not suitable enough for calculation of local disturbance of neutron field in RPV inner surface behind the surveillance specimens because of their complicated and heterogeneous structure. In some cases the VVER-1000 core loading consists of fuel assemblies with different fuel height and the applicability of synthesis approach is also ambiguous for these fuel cycles. Also, the synthesis approach is not enough correct for the neutron fluence estimation at the RPV area above core top. Because of these reasons only the 3D neutron transport codes seem to be satisfactory for calculation of neutron fluence on the VVER-1000 RPV. The direct 3D calculations are also recommended by modern regulations.
NASA Technical Reports Server (NTRS)
Stremel, Paul M.
1995-01-01
A method has been developed to accurately compute the viscous flow in three-dimensional (3-D) enclosures. This method is the 3-D extension of a two-dimensional (2-D) method developed for the calculation of flow over airfoils. The 2-D method has been tested extensively and has been shown to accurately reproduce experimental results. As in the 2-D method, the 3-D method provides for the non-iterative solution of the incompressible Navier-Stokes equations by means of a fully coupled implicit technique. The solution is calculated on a body fitted computational mesh incorporating a staggered grid methodology. In the staggered grid method, the three components of vorticity are defined at the centers of the computational cell sides, while the velocity components are defined as normal vectors at the centers of the computational cell faces. The staggered grid orientation provides for the accurate definition of the vorticity components at the vorticity locations, the divergence of vorticity at the mesh cell nodes and the conservation of mass at the mesh cell centers. The solution is obtained by utilizing a fractional step solution technique in the three coordinate directions. The boundary conditions for the vorticity and velocity are calculated implicitly as part of the solution. The method provides for the non-iterative solution of the flow field and satisfies the conservation of mass and divergence of vorticity to machine zero at each time step. To test the method, the calculation of simple driven cavity flows have been computed. The driven cavity flow is defined as the flow in an enclosure driven by a moving upper plate at the top of the enclosure. To demonstrate the ability of the method to predict the flow in arbitrary cavities, results will he shown for both cubic and curved cavities.
Dose calculation using megavoltage cone-beam CT
Morin, Olivier . E-mail: Morin@radonc17.ucsf.edu; Chen, Josephine; Aubin, Michele; Gillis, Amy; Aubry, Jean-Francois; Bose, Supratik; Chen Hong; Descovich, Martina; Xia Ping; Pouliot, Jean
2007-03-15
Purpose: To demonstrate the feasibility of performing dose calculation on megavoltage cone-beam CT (MVCBCT) of head-and-neck patients in order to track the dosimetric errors produced by anatomic changes. Methods and Materials: A simple geometric model was developed using a head-size water cylinder to correct an observed cupping artifact occurring with MVCBCT. The uniformity-corrected MVCBCT was calibrated for physical density. Beam arrangements and weights from the initial treatment plans defined using the conventional CT were applied to the MVCBCT image, and the dose distribution was recalculated. The dosimetric inaccuracies caused by the cupping artifact were evaluated on the water phantom images. An ideal test patient with no observable anatomic changes and a patient imaged with both CT and MVCBCT before and after considerable weight loss were used to clinically validate MVCBCT for dose calculation and to determine the dosimetric impact of large anatomic changes. Results: The nonuniformity of a head-size water phantom ({approx}30%) causes a dosimetric error of less than 5%. The uniformity correction method developed greatly reduces the cupping artifact, resulting in dosimetric inaccuracies of less than 1%. For the clinical cases, the agreement between the dose distributions calculated using MVCBCT and CT was better than 3% and 3 mm where all tissue was encompassed within the MVCBCT. Dose-volume histograms from the dose calculations on CT and MVCBCT were in excellent agreement. Conclusion: MVCBCT can be used to estimate the dosimetric impact of changing anatomy on several structures in the head-and-neck region.
Dose Calculation Evolution for Internal Organ Irradiation in Humans
Jimenez V, Reina A.
2007-10-26
The International Commission of Radiation Units (ICRU) has established through the years, a discrimination system regarding the security levels on the prescription and administration of doses in radiation treatments (Radiotherapy, Brach therapy, Nuclear Medicine). The first level is concerned with the prescription and posterior assurance of dose administration to a point of interest (POI), commonly located at the geometrical center of the region to be treated. In this, the effects of radiation around that POI, is not a priority. The second level refers to the dose specifications in a particular plane inside the patient, mostly the middle plane of the lesion. The dose is calculated to all the structures in that plane regardless if they are tumor or healthy tissue. In this case, the dose is not represented by a point value, but by level curves called 'isodoses' as in a topographic map, so you can assure the level of doses to this particular plane, but it also leave with no information about how this values go thru adjacent planes. This is why the third level is referred to the volumetrical description of doses so these isodoses construct now a volume (named 'cloud') that give us better assurance about tissue irradiation around the volume of the lesion and its margin (sub clinical spread or microscopic illness). This work shows how this evolution has resulted, not only in healthy tissue protection improvement but in a rise of tumor control, quality of life, better treatment tolerance and minimum permanent secuelae.
Internal dose conversion factors for calculation of dose to the public
Not Available
1988-07-01
This publication contains 50-year committed dose equivalent factors, in tabular form. The document is intended to be used as the primary reference by the US Department of Energy (DOE) and its contractors for calculating radiation dose equivalents for members of the public, resulting from ingestion or inhalation of radioactive materials. Its application is intended specifically for such materials released to the environment during routine DOE operations, except in those instances where compliance with 40 CFR 61 (National Emission Standards for Hazardous Air Pollutants) requires otherwise. However, the calculated values may be equally applicable to unusual releases or to occupational exposures. The use of these committed dose equivalent tables should ensure that doses to members of the public from internal exposures are calculated in a consistent manner at all DOE facilities.
NASA Technical Reports Server (NTRS)
Demuren, A. O.
1990-01-01
A multigrid method is presented for calculating turbulent jets in crossflow. Fairly rapid convergence is obtained with the k-epsilon turbulence model, but computations with a full Reynolds stress turbulence model (RSM) are not yet very efficient. Grid dependency tests show that there are slight differences between results obtained on the two finest grid levels. Computations using the RSM are significantly different from those with k-epsilon model and compare better to experimental data. Some work is still required to improve the efficiency of the computations with the RSM.
PLUTONIUM/HIGH LEVEL VITRIFIED WASTE - DBE OFFSITE DOSE CALCULATION
S. O. Bader
1999-09-20
The purpose of this calculation is to provide a bounding dose consequence analysis of the immobilized plutonium (can-in-canister) waste form to be handled at the Monitored Geologic Repository (MGR) at Yucca Mountain. The current concept for the Plutonium Can-in-Canister waste form is provided in Attachment III. A typical design basis event (DBE) defines a scenario that generally includes an initiating event and the sequences of events that follow. This analysis will provide (1) radiological releases and dose consequences for a postulated, bounding DBE and (2) design-related assumptions on which the calculated dose consequences are based. This analysis is part of the safety design basis for the repository. Results will be used in other analyses to determine or modify the safety classification and quality assurance level of repository structures, systems, and components (SSCs). The Quality Assurance (QA) program applies to this calculation. The work reported in this document is part of the analysis of MGR DBEs and is performed using AP-3.12Q, Calculations. The work done for this analysis was evaluated according to QAP-2-0, Control of Activities. This evaluation determined that such activities are subject to DOE/RW/0333PY Quality Assurance Requirements and Description (DOE 1998), requirements. This calculation is quality affecting because the results may be used to support analyses of repository SSCs per QAP-2-3, Classification of Permanent Items.
Dose calculations using artificial neural networks: A feasibility study for photon beams
NASA Astrophysics Data System (ADS)
Vasseur, Aurélien; Makovicka, Libor; Martin, Éric; Sauget, Marc; Contassot-Vivier, Sylvain; Bahi, Jacques
2008-04-01
Direct dose calculations are a crucial requirement for Treatment Planning Systems. Some methods, such as Monte Carlo, explicitly model particle transport, others depend upon tabulated data or analytic formulae. However, their computation time is too lengthy for clinical use, or accuracy is insufficient, especially for recent techniques such as Intensity-Modulated Radiotherapy. Based on artificial neural networks (ANNs), a new solution is proposed and this work extends the properties of such an algorithm and is called NeuRad. Prior to any calculations, a first phase known as the learning process is necessary. Monte Carlo dose distributions in homogeneous media are used, and the ANN is then acquired. According to the training base, it can be used as a dose engine for either heterogeneous media or for an unknown material. In this report, two networks were created in order to compute dose distribution within a homogeneous phantom made of an unknown material and within an inhomogeneous phantom made of water and TA6V4 (titanium alloy corresponding to hip prosthesis). All NeuRad results were compared to Monte Carlo distributions. The latter required about 7 h on a dedicated cluster (10 nodes). NeuRad learning requires between 8 and 18 h (depending upon the size of the training base) on a single low-end computer. However, the results of dose computation with the ANN are available in less than 2 s, again using a low-end computer, for a 150×1×150 voxels phantom. In the case of homogeneous medium, the mean deviation in the high dose region was less than 1.7%. With a TA6V4 hip prosthesis bathed in water, the mean deviation in the high dose region was less than 4.1%. Further improvements in NeuRad will have to include full 3D calculations, inhomogeneity management and input definitions.
Bhandare, N.
2014-06-01
Purpose: To estimate and compare the doses received by the obturator, external and internal iliac lymph nodes and point Methods: CT-MR fused image sets of 15 patients obtained for each of 5 fractions of HDR brachytherapy using tandem and ring applicator, were used to generate treatment plans optimized to deliver a prescription dose to HRCTV-D90 and to minimize the doses to organs at risk (OARs). For each set of image, target volume (GTV, HRCTV) OARs (Bladder, Rectum, Sigmoid), and both left and right pelvic lymph nodes (obturator, external and internal iliac lymph nodes) were delineated. Dose-volume histograms (DVH) were generated for pelvic nodal groups (left and right obturator group, internal and external iliac chains) Per fraction DVH parameters used for dose comparison included dose to 100% volume (D100), and dose received by 2cc (D2cc), 1cc (D1cc) and 0.1 cc (D0.1cc) of nodal volume. Dose to point B was compared with each DVH parameter using 2 sided t-test. Pearson correlation were determined to examine relationship of point B dose with nodal DVH parameters. Results: FIGO clinical stage varied from 1B1 to IIIB. The median pretreatment tumor diameter measured on MRI was 4.5 cm (2.7– 6.4cm).The median dose to bilateral point B was 1.20 Gy ± 0.12 or 20% of the prescription dose. The correlation coefficients were all <0.60 for all nodal DVH parameters indicating low degree of correlation. Only 2 cc of obturator nodes was not significantly different from point B dose on t-test. Conclusion: Dose to point B does not adequately represent the dose to any specific pelvic nodal group. When using image guided 3D dose-volume optimized treatment nodal groups should be individually identified and delineated to obtain the doses received by pelvic nodes.
NASA Astrophysics Data System (ADS)
Tang, S.; Zhang, M. H.
2014-12-01
Large-scale forcing data (vertical velocities and advective tendencies) are important atmospheric fields to drive single-column models (SCM), cloud-resolving models (CRM) and large-eddy simulations (LES), but they are difficult to calculate accurately. The current 1-dimensional constrained variational analysis (1D CVA) method (Zhang and Lin, 1997) used by the Atmospheric Radiation Measurement (ARM) program is limited to represent the average of a sounding network domain. We extended the original 1D CVA algorithm into 3-dimensional along with other improvements, calculated gridded large-scale forcing data, apparent heating sources (Q1) and moisture sinks (Q2), and compared with 5 reanalyses: ERA-Interim, NCEP CFSR, MERRA, JRA55 and NARR for a mid-latitude spring cyclone case. The results from a case study for in March 3rd 2000 at the Southern Great Plain (SGP) show that reanalyses generally captured the structure of the mid-latitude cyclone, but they have serious biases in the 2nd order derivative terms (divergences and horizontal derivations) at regional scales of less than a few hundred kilometers. Our algorithm provides a set of atmospheric fields consistent with the observed constraint variables at the surface and top of the atmosphere better than reanalyses. The analyzed atmospheric fields can be used in SCM, CRM and LES to provide 3-dimensional dynamical forcing, or be used to evaluate reanalyses or model simulations.
Guerin, P.; Baudron, A. M.; Lautard, J. J.
2006-07-01
This paper describes a new technique for determining the pin power in heterogeneous core calculations. It is based on a domain decomposition with overlapping sub-domains and a component mode synthesis technique for the global flux determination. Local basis functions are used to span a discrete space that allows fundamental global mode approximation through a Galerkin technique. Two approaches are given to obtain these local basis functions: in the first one (Component Mode Synthesis method), the first few spatial eigenfunctions are computed on each sub-domain, using periodic boundary conditions. In the second one (Factorized Component Mode Synthesis method), only the fundamental mode is computed, and we use a factorization principle for the flux in order to replace the higher order Eigenmodes. These different local spatial functions are extended to the global domain by defining them as zero outside the sub-domain. These methods are well-fitted for heterogeneous core calculations because the spatial interface modes are taken into account in the domain decomposition. Although these methods could be applied to higher order angular approximations - particularly easily to a SPN approximation - the numerical results we provide are obtained using a diffusion model. We show the methods' accuracy for reactor cores loaded with UOX and MOX assemblies, for which standard reconstruction techniques are known to perform poorly. Furthermore, we show that our methods are highly and easily parallelizable. (authors)
Furuta, T; Maeyama, T; Ishikawa, K L; Fukunishi, N; Fukasaku, K; Takagi, S; Noda, S; Himeno, R; Hayashi, S
2015-08-21
In this research, we used a 135 MeV/nucleon carbon-ion beam to irradiate a biological sample composed of fresh chicken meat and bones, which was placed in front of a PAGAT gel dosimeter, and compared the measured and simulated transverse-relaxation-rate (R2) distributions in the gel dosimeter. We experimentally measured the three-dimensional R2 distribution, which records the dose induced by particles penetrating the sample, by using magnetic resonance imaging. The obtained R2 distribution reflected the heterogeneity of the biological sample. We also conducted Monte Carlo simulations using the PHITS code by reconstructing the elemental composition of the biological sample from its computed tomography images while taking into account the dependence of the gel response on the linear energy transfer. The simulation reproduced the experimental distal edge structure of the R2 distribution with an accuracy under about 2 mm, which is approximately the same as the voxel size currently used in treatment planning. PMID:26266894
NASA Astrophysics Data System (ADS)
Furuta, T.; Maeyama, T.; Ishikawa, K. L.; Fukunishi, N.; Fukasaku, K.; Takagi, S.; Noda, S.; Himeno, R.; Hayashi, S.
2015-08-01
In this research, we used a 135 MeV/nucleon carbon-ion beam to irradiate a biological sample composed of fresh chicken meat and bones, which was placed in front of a PAGAT gel dosimeter, and compared the measured and simulated transverse-relaxation-rate (R2) distributions in the gel dosimeter. We experimentally measured the three-dimensional R2 distribution, which records the dose induced by particles penetrating the sample, by using magnetic resonance imaging. The obtained R2 distribution reflected the heterogeneity of the biological sample. We also conducted Monte Carlo simulations using the PHITS code by reconstructing the elemental composition of the biological sample from its computed tomography images while taking into account the dependence of the gel response on the linear energy transfer. The simulation reproduced the experimental distal edge structure of the R2 distribution with an accuracy under about 2 mm, which is approximately the same as the voxel size currently used in treatment planning.
Fast optimization and dose calculation in scanned ion beam therapy
Hild, S.; Graeff, C.; Trautmann, J.; Kraemer, M.; Zink, K.; Durante, M.; Bert, C.
2014-07-15
Purpose: Particle therapy (PT) has advantages over photon irradiation on static tumors. An increased biological effectiveness and active target conformal dose shaping are strong arguments for PT. However, the sensitivity to changes of internal geometry complicates the use of PT for moving organs. In case of interfractionally moving objects adaptive radiotherapy (ART) concepts known from intensity modulated radiotherapy (IMRT) can be adopted for PT treatments. One ART strategy is to optimize a new treatment plan based on daily image data directly before a radiation fraction is delivered [treatment replanning (TRP)]. Optimizing treatment plans for PT using a scanned beam is a time consuming problem especially for particles other than protons where the biological effective dose has to be calculated. For the purpose of TRP, fast optimization and fast dose calculation have been implemented into the GSI in-house treatment planning system (TPS) TRiP98. Methods: This work reports about the outcome of a code analysis that resulted in optimization of the calculation processes as well as implementation of routines supporting parallel execution of the code. To benchmark the new features, the calculation time for therapy treatment planning has been studied. Results: Compared to the original version of the TPS, calculation times for treatment planning (optimization and dose calculation) have been improved by a factor of 10 with code optimization. The parallelization of the TPS resulted in a speedup factor of 12 and 5.5 for the original version and the code optimized version, respectively. Hence the total speedup of the new implementation of the authors' TPS yielded speedup factors up to 55. Conclusions: The improved TPS is capable of completing treatment planning for ion beam therapy of a prostate irradiation considering organs at risk in this has been overseen in the review process. Also see below 6 min.
TH-C-BRD-02: Analytical Modeling and Dose Calculation Method for Asymmetric Proton Pencil Beams
Gelover, E; Wang, D; Hill, P; Flynn, R; Hyer, D
2014-06-15
Purpose: A dynamic collimation system (DCS), which consists of two pairs of orthogonal trimmer blades driven by linear motors has been proposed to decrease the lateral penumbra in pencil beam scanning proton therapy. The DCS reduces lateral penumbra by intercepting the proton pencil beam near the lateral boundary of the target in the beam's eye view. The resultant trimmed pencil beams are asymmetric and laterally shifted, and therefore existing pencil beam dose calculation algorithms are not capable of trimmed beam dose calculations. This work develops a method to model and compute dose from trimmed pencil beams when using the DCS. Methods: MCNPX simulations were used to determine the dose distributions expected from various trimmer configurations using the DCS. Using these data, the lateral distribution for individual beamlets was modeled with a 2D asymmetric Gaussian function. The integral depth dose (IDD) of each configuration was also modeled by combining the IDD of an untrimmed pencil beam with a linear correction factor. The convolution of these two terms, along with the Highland approximation to account for lateral growth of the beam along the depth direction, allows a trimmed pencil beam dose distribution to be analytically generated. The algorithm was validated by computing dose for a single energy layer 5×5 cm{sup 2} treatment field, defined by the trimmers, using both the proposed method and MCNPX beamlets. Results: The Gaussian modeled asymmetric lateral profiles along the principal axes match the MCNPX data very well (R{sup 2}≥0.95 at the depth of the Bragg peak). For the 5×5 cm{sup 2} treatment plan created with both the modeled and MCNPX pencil beams, the passing rate of the 3D gamma test was 98% using a standard threshold of 3%/3 mm. Conclusion: An analytical method capable of accurately computing asymmetric pencil beam dose when using the DCS has been developed.
External dose-rate conversion factors for calculation of dose to the public
Not Available
1988-07-01
This report presents a tabulation of dose-rate conversion factors for external exposure to photons and electrons emitted by radionuclides in the environment. This report was prepared in conjunction with criteria for limiting dose equivalents to members of the public from operations of the US Department of Energy (DOE). The dose-rate conversion factors are provided for use by the DOE and its contractors in performing calculations of external dose equivalents to members of the public. The dose-rate conversion factors for external exposure to photons and electrons presented in this report are based on a methodology developed at Oak Ridge National Laboratory. However, some adjustments of the previously documented methodology have been made in obtaining the dose-rate conversion factors in this report. 42 refs., 1 fig., 4 tabs.
Wemhoff, A P; Burnham, A K
2006-04-05
Cross-comparison of the results of two computer codes for the same problem provides a mutual validation of their computational methods. This cross-validation exercise was performed for LLNL's ALE3D code and AKTS's Thermal Safety code, using the thermal ignition of HMX in two standard LLNL cookoff experiments: the One-Dimensional Time to Explosion (ODTX) test and the Scaled Thermal Explosion (STEX) test. The chemical kinetics model used in both codes was the extended Prout-Tompkins model, a relatively new addition to ALE3D. This model was applied using ALE3D's new pseudospecies feature. In addition, an advanced isoconversional kinetic approach was used in the AKTS code. The mathematical constants in the Prout-Tompkins code were calibrated using DSC data from hermetically sealed vessels and the LLNL optimization code Kinetics05. The isoconversional kinetic parameters were optimized using the AKTS Thermokinetics code. We found that the Prout-Tompkins model calculations agree fairly well between the two codes, and the isoconversional kinetic model gives very similar results as the Prout-Tompkins model. We also found that an autocatalytic approach in the beta-delta phase transition model does affect the times to explosion for some conditions, especially STEX-like simulations at ramp rates above 100 C/hr, and further exploration of that effect is warranted.
Monte Carlo dose calculations for phantoms with hip prostheses
NASA Astrophysics Data System (ADS)
Bazalova, M.; Coolens, C.; Cury, F.; Childs, P.; Beaulieu, L.; Verhaegen, F.
2008-02-01
Computed tomography (CT) images of patients with hip prostheses are severely degraded by metal streaking artefacts. The low image quality makes organ contouring more difficult and can result in large dose calculation errors when Monte Carlo (MC) techniques are used. In this work, the extent of streaking artefacts produced by three common hip prosthesis materials (Ti-alloy, stainless steel, and Co-Cr-Mo alloy) was studied. The prostheses were tested in a hypothetical prostate treatment with five 18 MV photon beams. The dose distributions for unilateral and bilateral prosthesis phantoms were calculated with the EGSnrc/DOSXYZnrc MC code. This was done in three phantom geometries: in the exact geometry, in the original CT geometry, and in an artefact-corrected geometry. The artefact-corrected geometry was created using a modified filtered back-projection correction technique. It was found that unilateral prosthesis phantoms do not show large dose calculation errors, as long as the beams miss the artefact-affected volume. This is possible to achieve in the case of unilateral prosthesis phantoms (except for the Co-Cr-Mo prosthesis which gives a 3% error) but not in the case of bilateral prosthesis phantoms. The largest dose discrepancies were obtained for the bilateral Co-Cr-Mo hip prosthesis phantom, up to 11% in some voxels within the prostate. The artefact correction algorithm worked well for all phantoms and resulted in dose calculation errors below 2%. In conclusion, a MC treatment plan should include an artefact correction algorithm when treating patients with hip prostheses.
NASA Astrophysics Data System (ADS)
Berger, Thomas
The radiation environment encountered in space differs in nature from that on earth, consisting mostly of high energetic ions from protons up to iron, resulting in radiation levels far exceeding the ones present on earth for occupational radiation workers. Accurate knowledge of the physical characteristics of the space radiation field in dependence on the solar activity, the orbital parameters and the different shielding configurations of the International Space Station (ISS) is therefore needed. For the investigation of the spatial and temporal distribution of the radiation field inside the European Columbus module the experiment “Dose Distribution Inside the ISS” (DOSIS), under the project and science lead of the German Aerospace Center (DLR), was launched on July 15th 2009 with STS-127 to the ISS. The DOSIS experiment consists of a combination of “Passive Detector Packages” (PDP) distributed at eleven locations inside Columbus for the measurement of the spatial variation of the radiation field and two active Dosimetry Telescopes (DOSTELs) with a Data and Power Unit (DDPU) in a dedicated nomex pouch mounted at a fixed location beneath the European Physiology Module rack (EPM) for the measurement of the temporal variation of the radiation field parameters. The DOSIS experiment suite measured during the lowest solar minimum conditions in the space age from July 2009 to June 2011. In July 2011 the active hardware was transferred to ground for refurbishment and preparation for the follow up DOSIS 3D experiment. The hardware for DOSIS 3D was launched with Soyuz 30S to the ISS on May 15th 2012. The PDPs are replaced with each even number Soyuz flight starting with Soyuz 30S. Data from the active detectors is transferred to ground via the EPM rack which is activated once a month for this action. The presentation will give an overview of the DOSIS and DOSIS 3D experiment and focus on the results from the passive radiation detectors from the DOSIS 3D experiment
NASA Astrophysics Data System (ADS)
Fischer, E.; Shcherbakov, P.; Kurnyshov, R.
2007-11-01
The synchrotron SIS100 is one of the two basic accelerators of the future Facility for Antiproton and Ion Research (FAIR) at GSI in Darmstadt. This accelerator should provide high intensity U28+ and proton beams with a pulse repetition rate of 1 Hz (i.e. a ramp rate of 4 T/s). The magnetic system of the accelerator uses superferric 2.1 T dipoles of about 3 m length and 32 T/m quadrupoles of about 1 m length. The magnet coils are made of a hollow tube cable wrapped with Cu/NbTi composite wire cooled with two phase helium flow at 4.5 K. The bore dimensions were defined to 130 × 60 mm for the dipole and 135 × 65 mm for the quadrupole. We present the developed ANSYS models for different important aspects: AC loss, magnetic field quality and mechanical stability. Preliminary studies verified the approaches and these models were applied to calculate the effects for the coil, the yoke and the beam pipe structures. We outline further steps to fully describe the SIS100 magnets including mechanical and thermal properties.
Smithe, D.N.; Colestock, P.L.; Kashuba, R.J.; Kammash, T.
1987-04-01
A computational scheme is developed which permits tractable calculation of three-dimensional full-wave solutions to the Maxwell-Vlasov equations under typical Ion Cyclotron Range of Frequencies (ICRF) experimental conditions. The method is unique in that power deposition to the plasma is determined via the anti-Hermitian part of a truncated warm-plasma dielectric operator, rather than as the result of an assumed phenomenological collision frequency. The resulting computer code allows arbitrary variation of density, temperature, magnetic field, and minority concentration in the poloidal plane by performing a convolution of poloidal modes to produce a coupled system of differential equations in the radial variable. By assuming no inhomogeneity along the toroidal axis, an inverse transform over k/sub parallel/ is performed to yield the full three-dimensional field solutions. The application of the code to TFTR-like plasmas shows a mild resonance structure in antenna loading related to the changing number of wavelengths between antenna and the resonance layer. 48 figs.
NASA Astrophysics Data System (ADS)
Alrowaili, Z. A.; Lerch, M. L. F.; Carolan, M.; Fuduli, I.; Porumb, C.; Petasecca, M.; Metcalfe, P.; Rosenfeld, A. B.
2015-09-01
Summary: the photon irradiation response of a 2D solid state transmission detector array mounted in a linac block tray is used to reconstruct the projected 2D dose map in a homogenous phantom along rays that diverge from the X-ray source and pass through each of the 121 detector elements. A unique diode response-to-dose scaling factor, applied to all detectors, is utilised in the reconstruction to demonstrate that real time QA during radiotherapy treatment is feasible. Purpose: to quantitatively demonstrate reconstruction of the real time radiation dose from the irradiation response of the 11×11 silicon Magic Plate (MP) detector array operated in Transmission Mode (MPTM). Methods and Materials: in transmission mode the MP is positioned in the block tray of a linac so that the central detector of the array lies on the central axis of the radiation beam. This central detector is used to determine the conversion factor from measured irradiation response to reconstructed dose at any point on the central axis within a homogenous solid water phantom. The same unique conversion factor is used for all MP detector elements lying within the irradiation field. Using the two sets of data, the 2D or 3D dose map is able to be reconstructed in the homogenous phantom. The technique we have developed is illustrated here for different depths and irradiation field sizes, (5 × 5 cm2 to 40 × 40 cm2) as well as a highly non uniform irradiation field. Results: we find that the MPTM response is proportional to the projected 2D dose map measured at a specific phantom depth, the "sweet depth". A single factor, for several irradiation field sizes and depths, is derived to reconstruct the dose in the phantom along rays projected from the photon source through each MPTM detector element. We demonstrate that for all field sizes using the above method, the 2D reconstructed and measured doses agree to within ± 2.48% (2 standard deviation) for all in-field MP detector elements. Conclusions: a
NASA Astrophysics Data System (ADS)
Oldham, Mark
2015-01-01
Radiochromic materials exhibit a colour change when exposed to ionising radiation. Radiochromic film has been used for clinical dosimetry for many years and increasingly so recently, as films of higher sensitivities have become available. The two principle advantages of radiochromic dosimetry include greater tissue equivalence (radiologically) and the lack of requirement for development of the colour change. In a radiochromic material, the colour change arises direct from ionising interactions affecting dye molecules, without requiring any latent chemical, optical or thermal development, with important implications for increased accuracy and convenience. It is only relatively recently however, that 3D radiochromic dosimetry has become possible. In this article we review recent developments and the current state-of-the-art of 3D radiochromic dosimetry, and the potential for a more comprehensive solution for the verification of complex radiation therapy treatments, and 3D dose measurement in general.
Xu, Zhongnan; Kitchin, John R.; Joshi, Yogesh V.; Raman, Sumathy
2015-04-14
We validate the usage of the calculated, linear response Hubbard U for evaluating accurate electronic and chemical properties of bulk 3d transition metal oxides. We find calculated values of U lead to improved band gaps. For the evaluation of accurate reaction energies, we first identify and eliminate contributions to the reaction energies of bulk systems due only to changes in U and construct a thermodynamic cycle that references the total energies of unique U systems to a common point using a DFT + U(V ) method, which we recast from a recently introduced DFT + U(R) method for molecular systems. We then introduce a semi-empirical method based on weighted DFT/DFT + U cohesive energies to calculate bulk oxidation energies of transition metal oxides using density functional theory and linear response calculated U values. We validate this method by calculating 14 reactions energies involving V, Cr, Mn, Fe, and Co oxides. We find up to an 85% reduction of the mean average error (MAE) compared to energies calculated with the Perdew-Burke-Ernzerhof functional. When our method is compared with DFT + U with empirically derived U values and the HSE06 hybrid functional, we find up to 65% and 39% reductions in the MAE, respectively.
Monte Carlo Code System for Electron (Positron) Dose Kernel Calculations.
CHIBANI, OMAR
1999-05-12
Version 00 KERNEL performs dose kernel calculations for an electron (positron) isotropic point source in an infinite homogeneous medium. First, the auxiliary code PRELIM is used to prepare cross section data for the considered medium. Then the KERNEL code simulates the transport of electrons and bremsstrahlung photons through the medium until all particles reach their cutoff energies. The deposited energy is scored in concentric spherical shells at a radial distance ranging from zero to twice the source particle range.
NASA Astrophysics Data System (ADS)
Harvey, R. W. (Bob); Petrov, Yu. V.; Jaeger, E. F.; Berry, L. A.; Bonoli, P. T.; Bader, A.
2015-11-01
A time-dependent simulation of C-Mod pulsed ICRF power is made calculating minority hydrogen ion distribution functions with the CQL3D-Hybrid-FOW finite-orbit-width Fokker-Planck code. ICRF fields are calculated with the AORSA full wave code, and RF diffusion coefficients are obtained from these fields using the DC Lorentz gyro-orbit code. Prior results with a zero-banana-width simulation using the CQL3D/AORSA/DC time-cycles showed a pronounced enhancement of the H distribution in the perpendicular velocity direction compared to results obtained from Stix's quasilinear theory, in general agreement with experiment. The present study compares the new FOW results, including relevant gyro-radius effects, to determine the importance of these effects on the the NPA synthetic diagnostic time-dependence. The new NPA results give increased agreement with experiment, particularly in the ramp-down time after the ICRF pulse. Funded, through subcontract with Massachusetts Institute of Technology, by USDOE sponsored SciDAC Center for Simulation of Wave-Plasma Interactions.
Hoffman, E.L.; Ammerman, D.J.
1995-04-01
A series of tests investigating dynamic pulse buckling of a cylindrical shell under axial impact is compared to several 2D and 3D finite element simulations of the event. The purpose of the work is to investigate the performance of various analysis codes and element types on a problem which is applicable to radioactive material transport packages, and ultimately to develop a benchmark problem to qualify finite element analysis codes for the transport package design industry. Four axial impact tests were performed on 4 in-diameter, 8 in-long, 304 L stainless steel cylinders with a 3/16 in wall thickness. The cylinders were struck by a 597 lb mass with an impact velocity ranging from 42.2 to 45.1 ft/sec. During the impact event, a buckle formed at each end of the cylinder, and one of the two buckles became unstable and collapsed. The instability occurred at the top of the cylinder in three tests and at the bottom in one test. Numerical simulations of the test were performed using the following codes and element types: PRONTO2D with axisymmetric four-node quadrilaterals; PRONTO3D with both four-node shells and eight-node hexahedrons; and ABAQUS/Explicit with axisymmetric two-node shells and four-node quadrilaterals, and 3D four-node shells and eight-node hexahedrons. All of the calculations are compared to the tests with respect to deformed shape and impact load history. As in the tests, the location of the instability is not consistent in all of the calculations. However, the calculations show good agreement with impact load measurements with the exception of an initial load spike which is proven to be the dynamic response of the load cell to the impact. Finally, the PRONIT02D calculation is compared to the tests with respect to strain and acceleration histories. Accelerometer data exhibited good qualitative agreement with the calculations. The strain comparisons show that measurements are very sensitive to gage placement.
NASA Astrophysics Data System (ADS)
Klinger, Carolin; Mayer, Bernhard
2016-01-01
Due to computational costs, radiation is usually neglected or solved in plane parallel 1D approximation in today's numerical weather forecast and cloud resolving models. We present a fast and accurate method to calculate 3D heating and cooling rates in the thermal spectral range that can be used in cloud resolving models. The parameterization considers net fluxes across horizontal box boundaries in addition to the top and bottom boundaries. Since the largest heating and cooling rates occur inside the cloud, close to the cloud edge, the method needs in first approximation only the information if a grid box is at the edge of a cloud or not. Therefore, in order to calculate the heating or cooling rates of a specific grid box, only the directly neighboring columns are used. Our so-called Neighboring Column Approximation (NCA) is an analytical consideration of cloud side effects which can be considered a convolution of a 1D radiative transfer result with a kernel or radius of 1 grid-box (5 pt stencil) and which does usually not break the parallelization of a cloud resolving model. The NCA can be easily applied to any cloud resolving model that includes a 1D radiation scheme. Due to the neglect of horizontal transport of radiation further away than one model column, the NCA works best for model resolutions of about 100 m or lager. In this paper we describe the method and show a set of applications of LES cloud field snap shots. Correction terms, gains and restrictions of the NCA are described. Comprehensive comparisons to the 3D Monte Carlo Model MYSTIC and a 1D solution are shown. In realistic cloud fields, the full 3D simulation with MYSTIC shows cooling rates up to -150 K/d (100 m resolution) while the 1D solution shows maximum coolings of only -100 K/d. The NCA is capable of reproducing the larger 3D cooling rates. The spatial distribution of the heating and cooling is improved considerably. Computational costs are only a factor of 1.5-2 higher compared to a 1D
Pitsevich, G; Malevich, A; Doroshenko, I; Kozlovskaya, E; Pogorelov, V; Sablinskas, V; Balevicius, V
2014-01-01
FTIR spectra of pyridine N-oxide and trichloroacetic acid H-bonded complex in acetonitrile were studied at 20 and 50°C. The calculations of equilibrium configurations of the complex and their IR spectra in harmonic- and anharmonic approximations were carried out at the level of B3LYP/cc-pVTZ/PCM. However both approximations turned out to be incompetent determining the frequency of the O-Н stretching vibration. In order to reveal the causes of essential discrepancies between calculated and experimental data one-, two- and three-dimensional potential energy surfaces (PES) of the O-H…O bridge proton motion in the frame of fixed other atoms in the complex were calculated. The frequencies of O-H…O stretching and bending vibrations were calculated by numerical solution of the Schrödinger equation. It is shown that only the approach of proton motion on the 3D PES allows obtaining a good agreement between the calculated and the experimental values of the frequencies of the О-Н stretching vibrations. PMID:24373980
Off-center ratios for three-dimensional dose calculations
Chui, C.S.; Mohan, R.
1986-05-01
A new method is proposed for computing the off-center ratios (OCR's) in three-dimensional dose calculations. For an open field, the OCR at a point is computed as the product of the primary OCR (POCR) and the boundary factors (BF's). The POCR describes the beam profile for an infinite field, that is, without the effect of the collimators. It is defined as the ratio of the dose at a point off the central ray to the dose at the point on the central ray at the same depth for an infinite field. The POCR is a function of radial distance from the beam central ray and depth. The BF describes the shape of the beam in the neighborhood of the field boundary defined by the collimators. It is defined as the ratio of the OCR at a point for a finite field to the OCR at the same point for an infinite field. The BF is a function of distance from the field boundary, depth, and field size. For a wedged field, we assume that the boundary factors remain the same as for open fields but the POCR's are altered. The changes in beam profiles are described by a factor called the wedge profile factor (WPF), defined as the ratio of the dose at a point for the largest wedged field to the dose at the same point for an open field of the same field size. The WPF is a function of lateral distance from the beam central plane and depth. Calculated OCR's using this new method are in agreement with the measured data along both the transverse and the diagonal directions of the field.
Dose discrepancies in the buildup region and their impact on dose calculations for IMRT fields
Hsu, Shu-Hui; Moran, Jean M.; Chen Yu; Kulasekere, Ravi; Roberson, Peter L.
2010-05-15
Purpose: Dose accuracy in the buildup region for radiotherapy treatment planning suffers from challenges in both measurement and calculation. This study investigates the dosimetry in the buildup region at normal and oblique incidences for open and IMRT fields and assesses the quality of the treatment planning calculations. Methods: This study was divided into three parts. First, percent depth doses and profiles (for 5x5, 10x10, 20x20, and 30x30 cm{sup 2} field sizes at 0 deg., 45 deg., and 70 deg. incidences) were measured in the buildup region in Solid Water using an Attix parallel plate chamber and Kodak XV film, respectively. Second, the parameters in the empirical contamination (EC) term of the convolution/superposition (CVSP) calculation algorithm were fitted based on open field measurements. Finally, seven segmental head-and-neck IMRT fields were measured on a flat phantom geometry and compared to calculations using {gamma} and dose-gradient compensation (C) indices to evaluate the impact of residual discrepancies and to assess the adequacy of the contamination term for IMRT fields. Results: Local deviations between measurements and calculations for open fields were within 1% and 4% in the buildup region for normal and oblique incidences, respectively. The C index with 5%/1 mm criteria for IMRT fields ranged from 89% to 99% and from 96% to 98% at 2 mm and 10 cm depths, respectively. The quality of agreement in the buildup region for open and IMRT fields is comparable to that in nonbuildup regions. Conclusions: The added EC term in CVSP was determined to be adequate for both open and IMRT fields. Due to the dependence of calculation accuracy on (1) EC modeling, (2) internal convolution and density grid sizes, (3) implementation details in the algorithm, and (4) the accuracy of measurements used for treatment planning system commissioning, the authors recommend an evaluation of the accuracy of near-surface dose calculations as a part of treatment planning
Dose discrepancies in the buildup region and their impact on dose calculations for IMRT fields
Hsu, Shu-Hui; Moran, Jean M.; Chen, Yu; Kulasekere, Ravi; Roberson, Peter L.
2010-01-01
Purpose: Dose accuracy in the buildup region for radiotherapy treatment planning suffers from challenges in both measurement and calculation. This study investigates the dosimetry in the buildup region at normal and oblique incidences for open and IMRT fields and assesses the quality of the treatment planning calculations. Methods: This study was divided into three parts. First, percent depth doses and profiles (for 5×5, 10×10, 20×20, and 30×30 cm2 field sizes at 0°, 45°, and 70° incidences) were measured in the buildup region in Solid Water using an Attix parallel plate chamber and Kodak XV film, respectively. Second, the parameters in the empirical contamination (EC) term of the convolution∕superposition (CVSP) calculation algorithm were fitted based on open field measurements. Finally, seven segmental head-and-neck IMRT fields were measured on a flat phantom geometry and compared to calculations using γ and dose-gradient compensation (C) indices to evaluate the impact of residual discrepancies and to assess the adequacy of the contamination term for IMRT fields. Results: Local deviations between measurements and calculations for open fields were within 1% and 4% in the buildup region for normal and oblique incidences, respectively. The C index with 5%∕1 mm criteria for IMRT fields ranged from 89% to 99% and from 96% to 98% at 2 mm and 10 cm depths, respectively. The quality of agreement in the buildup region for open and IMRT fields is comparable to that in nonbuildup regions. Conclusions: The added EC term in CVSP was determined to be adequate for both open and IMRT fields. Due to the dependence of calculation accuracy on (1) EC modeling, (2) internal convolution and density grid sizes, (3) implementation details in the algorithm, and (4) the accuracy of measurements used for treatment planning system commissioning, the authors recommend an evaluation of the accuracy of near-surface dose calculations as a part of treatment planning commissioning
Patient-specific Monte Carlo dose calculations for 103Pd breast brachytherapy
NASA Astrophysics Data System (ADS)
Miksys, N.; Cygler, J. E.; Caudrelier, J. M.; Thomson, R. M.
2016-04-01
This work retrospectively investigates patient-specific Monte Carlo (MC) dose calculations for 103Pd permanent implant breast brachytherapy, exploring various necessary assumptions for deriving virtual patient models: post-implant CT image metallic artifact reduction (MAR), tissue assignment schemes (TAS), and elemental tissue compositions. Three MAR methods (thresholding, 3D median filter, virtual sinogram) are applied to CT images; resulting images are compared to each other and to uncorrected images. Virtual patient models are then derived by application of different TAS ranging from TG-186 basic recommendations (mixed adipose and gland tissue at uniform literature-derived density) to detailed schemes (segmented adipose and gland with CT-derived densities). For detailed schemes, alternate mass density segmentation thresholds between adipose and gland are considered. Several literature-derived elemental compositions for adipose, gland and skin are compared. MC models derived from uncorrected CT images can yield large errors in dose calculations especially when used with detailed TAS. Differences in MAR method result in large differences in local doses when variations in CT number cause differences in tissue assignment. Between different MAR models (same TAS), PTV {{D}90} and skin {{D}1~\\text{c{{\\text{m}}3}}} each vary by up to 6%. Basic TAS (mixed adipose/gland tissue) generally yield higher dose metrics than detailed segmented schemes: PTV {{D}90} and skin {{D}1~\\text{c{{\\text{m}}3}}} are higher by up to 13% and 9% respectively. Employing alternate adipose, gland and skin elemental compositions can cause variations in PTV {{D}90} of up to 11% and skin {{D}1~\\text{c{{\\text{m}}3}}} of up to 30%. Overall, AAPM TG-43 overestimates dose to the PTV ({{D}90} on average 10% and up to 27%) and underestimates dose to the skin ({{D}1~\\text{c{{\\text{m}}3}}} on average 29% and up to 48%) compared to the various MC models derived using the post-MAR CT images studied
NASA Astrophysics Data System (ADS)
Predoi-Cross, A.; Malathy Devi, V.; Sutradhar, P.; Sinyakova, T.; Buldyreva, J.; Sung, K.; Smith, M. A. H.; Mantz, A. W.
2016-07-01
This paper presents the results of a spectroscopic line shape study of self- and nitrogen-broadened 12CH3D transitions in the ν3 and ν5 bands in the Triad region. We combined five pure gas spectra with eighteen spectra of lean mixtures of 12CH3D and nitrogen, all recorded with a Bruker IFS-125 HR Fourier transform spectrometer. The spectra have been analyzed simultaneously using a multispectrum nonlinear least squares fitting technique. N2-broadened line parameters for 184 transitions in the ν3 band and 205 transitions in the ν5 band were measured. In addition, line positions and line intensities were measured for 168 transitions in the ν3 band and 214 transitions in the ν5 band. We have observed 10 instances of weak line mixing corresponding to K″=3 A1 or A2 transitions. Comparisons were made for the N2-broadening coefficients and associated temperature exponents with corresponding values calculated using a semi-classical Robert Bonamy type formalism that involved an inter-molecular potential with terms corresponding to short- and long-range interactions, and exact classical molecular trajectories. The theoretical N2-broadened coefficients are overestimated for high J values, but are in good agreement with the experimental values for small and middle range J values.
Gleckler, M; Valentine, J D; Silberstein, E B
1998-01-01
Using a 90Sr applicator for brachytherapy for the reduction of recurrence rates after pterygium excisions has been an effective therapeutic procedure. Accurate knowledge of the dose being applied to the affected area on the sclera has been lacking, and for decades inaccurate estimates for lens dose have thus been made. Small errors in the assumptions which are required to make these estimates lead to dose rates changing exponentially because of the attenuation of beta particles. Monte Carlo simulations have been used to evaluate the assumptions that are now being used for the calculation of the surface dose rate and the corresponding determination of lens dose. For an ideal 90Sr applicator, results from this study indicate dose rates to the most radiosensitive areas of the lens ranging from 8.8 to 15.5 cGy/s. This range is based on different eye dimensions that ultimately corresponds to a range in distance between the applicator surface and the germinative epithelium of the lens of 2-3 mm. Furthermore, the conventional 200 cGy threshold for whole lens cataractogenesis is questioned for predicting complications from scleral brachytherapy. The dose to the germinative epithelium should be used for studying radiocataractogenesis.
Source term calculations for assessing radiation dose to equipment
Denning, R.S.; Freeman-Kelly, R.; Cybulskis, P.; Curtis, L.A.
1989-07-01
This study examines results of analyses performed with the Source Term Code Package to develop updated source terms using NUREG-0956 methods. The updated source terms are to be used to assess the adequacy of current regulatory source terms used as the basis for equipment qualification. Time-dependent locational distributions of radionuclides within a containment following a severe accident have been developed. The Surry reactor has been selected in this study as representative of PWR containment designs. Similarly, the Peach Bottom reactor has been used to examine radionuclide distributions in boiling water reactors. The time-dependent inventory of each key radionuclide is provided in terms of its activity in curies. The data are to be used by Sandia National Laboratories to perform shielding analyses to estimate radiation dose to equipment in each containment design. See NUREG/CR-5175, Beta and Gamma Dose Calculations for PWR and BWR Containments.'' 6 refs., 11 tabs.
New calculations of neutron kerma coefficients and dose equivalent.
Liu, Zhenzhou; Chen, Jinxiang
2008-06-01
For neutron energies ranging from 1 keV to 20 MeV, the kerma coefficients for elements H, C, N, O, light water, and ICRU tissue were deduced respectively from microscopic cross sections and Monte Carlo simulation (MCNP code). The results are consistent within admitted uncertainties with values evaluated by an international group (Chadwick et al 1999 Med. Phys. 26 974-91). The ambient dose equivalent generated in the ISO-recommended neutron field for an Am-Be neutron source (ISO 8529-1: 2001(E)) was obtained from the kerma coefficients and Monte Carlo calculation. In addition, it was calculated directly by multiplying the neutron fluence by the fluence-to-ambient dose conversion coefficients recommended by ICRP (ICRP 1996 ICRP Publication 74 (Oxford: Pergamon)). The two results agree well with each other. The main feature of this work is our Monte Carlo simulation design and the treatments differing from the work of others in the calculation of neutron energy transfer in non-elastic processes. PMID:18495982
Monte Carlo Code System for Electron (Positron) Dose Kernel Calculations.
1999-05-12
Version 00 KERNEL performs dose kernel calculations for an electron (positron) isotropic point source in an infinite homogeneous medium. First, the auxiliary code PRELIM is used to prepare cross section data for the considered medium. Then the KERNEL code simulates the transport of electrons and bremsstrahlung photons through the medium until all particles reach their cutoff energies. The deposited energy is scored in concentric spherical shells at a radial distance ranging from zero to twicemore » the source particle range.« less
Chapman, K E; Thomas, A D; Wills, J W; Pfuhler, S; Doak, S H; Jenkins, G J S
2014-05-01
Recent restrictions on the testing of cosmetic ingredients in animals have resulted in the need to test the genotoxic potential of chemicals exclusively in vitro prior to licensing. However, as current in vitro tests produce some misleading positive results, sole reliance on such tests could prevent some chemicals with safe or beneficial exposure levels from being marketed. The 3D human reconstructed skin micronucleus (RSMN) assay is a promising new in vitro approach designed to assess genotoxicity of dermally applied compounds. The assay utilises a highly differentiated in vitro model of the human epidermis. For the first time, we have applied automated micronucleus detection to this assay using MetaSystems Metafer Slide Scanning Platform (Metafer), demonstrating concordance with manual scoring. The RSMN assay's fixation protocol was found to be compatible with the Metafer, providing a considerably shorter alternative to the recommended Metafer protocol. Lowest observed genotoxic effect levels (LOGELs) were observed for mitomycin-C at 4.8 µg/ml and methyl methanesulfonate (MMS) at 1750 µg/ml when applied topically to the skin surface. In-medium dosing with MMS produced a LOGEL of 20 µg/ml, which was very similar to the topical LOGEL when considering the total mass of MMS added. Comparisons between 3D medium and 2D LOGELs resulted in a 7-fold difference in total mass of MMS applied to each system, suggesting a protective function of the 3D microarchitecture. Interestingly, hydrogen peroxide (H2O2), a positive clastogen in 2D systems, tested negative in this assay. A non-genotoxic carcinogen, methyl carbamate, produced negative results, as expected. We also demonstrated expression of the DNA repair protein N-methylpurine-DNA glycosylase in EpiDerm™. Our preliminary validation here demonstrates that the RSMN assay may be a valuable follow-up to the current in vitro test battery, and together with its automation, could contribute to minimising unnecessary in vivo
Schaeken, B.; Lelie, S.; Meijnders, P.; Van den Weyngaert, D.; Janssens, H.; Verellen, D.
2010-12-15
Purpose: To avoid complications in total body irradiation (TBI), it is important to achieve a homogeneous dose distribution throughout the body and to deliver a correct dose to the lung which is an organ at risk. The purpose of this work was to validate the TBI dose protocol and to check the accuracy of the 3D dose calculations of the treatment planning system. Methods: Dosimetry based on alanine/electron paramagnetic resonance (EPR) was used to measure dose at numerous locations within an anthropomorphic phantom (Alderson) that was irradiated in a clinical TBI beam setup. The alanine EPR dosimetry system was calibrated against water calorimetry in a Co-60 beam and the absorbed dose was determined by the use of ''dose-normalized amplitudes'' A{sub D}. The dose rate of the TBI beam was checked against a Farmer ionization chamber. The phantom measurements were compared to 3D dose calculations from a treatment planning system (Pinnacle) modeled for standard dose calculations. Results: Alanine dosimetry allowed accurate measurements which were in accordance with ionization chamber measurements. The combined relative standard measurement uncertainty in the Alderson phantom was U{sub r}(A{sub D})=0.6%. The humanoid phantom was irradiated to a reference dose of 10 Gy, limiting the lung dose to 7.5 Gy. The ratio of the average measured dose midplane in the craniocaudal direction to the reference dose was 1.001 with a spread of {+-}4.7% (1 sd). Dose to the lung was measured in 26 locations and found, in average, 1.8% lower than expected. Lung dose was homogeneous in the ventral-dorsal direction but a dose gradient of 0.10 Gy cm{sup -1} was observed in the craniocaudal direction midline within the lung lobe. 3D dose calculations (Pinnacle) were found, in average, 2% lower compared to dose measurements on the body axis and 3% lower for the lungs. Conclusions: The alanine/EPR dosimetry system allowed accurate dose measurements which enabled the authors to validate their TBI
40 CFR Appendix B to Part 191 - Calculation of Annual Committed Effective Dose
Code of Federal Regulations, 2011 CFR
2011-07-01
...—Calculation of Annual Committed Effective Dose I. Equivalent Dose The calculation of the committed effective dose (CED) begins with the determination of the equivalent dose, HT, to a tissue or organ, T, listed in... is the radiation weighting factor which is given in Table B.1 below. The unit of equivalent dose...
PFP vertical calciner shield wall dose rate calculations using MCNP
Wittekind, W.D.
1997-08-21
This report yields a neutron shield wall design for a full time occupancy dose rate of 0.25 mrem/h. ORIGEN2 generated gamma ray spectrum and neutron intensity for plutonium. MCNP modeled the calciner glovebox and room for reflection of neutrons off concrete walls and ceiling. Neutron calculations used MCNP in mode n, p to include neutron capture gammas. Photon calculations used MCNP in mode p for gamma rays. Neutron shield with lower 137.16 cm (4.5 feet) of 12.7 cm (5 inch) thick Lucite{reg_sign} and 0.3175 cm (0.125 inch) stainless steel on both sides, and upper 76.2 cm (2.5 feet) of 10.16 cm (4 inch) thick Lucite{reg_sign} and 1.905 cm (0.75 inch) thick glass on each side gave a total weighted dose rate of 0.23 mrem/h, fulfilling the design goal. Lucite{reg_sign} is considered to be equivalent to Plexiglas{reg_sign} since both are methylmethacrylate polymers.
Assessing the effect of electron density in photon dose calculations
Seco, J.; Evans, P. M.
2006-02-15
Photon dose calculation algorithms (such as the pencil beam and collapsed cone, CC) model the attenuation of a primary photon beam in media other than water, by using pathlength scaling based on the relative mass density of the media to water. In this study, we assess if differences in the electron density between the water and media, with different atomic composition, can influence the accuracy of conventional photon dose calculations algorithms. A comparison is performed between an electron-density scaling method and the standard mass-density scaling method for (i) tissues present in the human body (such as bone, muscle, etc.), and for (ii) water-equivalent plastics, used in radiotherapy dosimetry and quality assurance. We demonstrate that the important material property that should be taken into account by photon dose algorithms is the electron density, and not the mass density. The mass-density scaling method is shown to overestimate, relative to electron-density predictions, the primary photon fluence for tissues in the human body and water-equivalent plastics, where 6%-7% and 10% differences were observed respectively for bone and air. However, in the case of patients, differences are expected to be smaller due to the large complexity of a treatment plan and of the patient anatomy and atomic composition and of the smaller thickness of bone/air that incident photon beams of a treatment plan may have to traverse. Differences have also been observed for conventional dose algorithms, such as CC, where an overestimate of the lung dose occurs, when irradiating lung tumors. The incorrect lung dose can be attributed to the incorrect modeling of the photon beam attenuation through the rib cage (thickness of 2-3 cm in bone upstream of the lung tumor) and through the lung and the oversimplified modeling of electron transport in convolution algorithms. In the present study, the overestimation of the primary photon fluence, using the mass-density scaling method, was shown
Investigation of Nonuniform Dose Voxel Geometry in Monte Carlo Calculations.
Yuan, Jiankui; Chen, Quan; Brindle, James; Zheng, Yiran; Lo, Simon; Sohn, Jason; Wessels, Barry
2015-08-01
The purpose of this work is to investigate the efficacy of using multi-resolution nonuniform dose voxel geometry in Monte Carlo (MC) simulations. An in-house MC code based on the dose planning method MC code was developed in C++ to accommodate the nonuniform dose voxel geometry package since general purpose MC codes use their own coupled geometry packages. We devised the package in a manner that the entire calculation volume was first divided into a coarse mesh and then the coarse mesh was subdivided into nonuniform voxels with variable voxel sizes based on density difference. We name this approach as multi-resolution subdivision (MRS). It generates larger voxels in small density gradient regions and smaller voxels in large density gradient regions. To take into account the large dose gradients due to the beam penumbra, the nonuniform voxels can be further split using ray tracing starting from the beam edges. The accuracy of the implementation of the algorithm was verified by comparing with the data published by Rogers and Mohan. The discrepancy was found to be 1% to 2%, with a maximum of 3% at the interfaces. Two clinical cases were used to investigate the efficacy of nonuniform voxel geometry in the MC code. Applying our MRS approach, we started with the initial voxel size of 5 × 5 × 3 mm(3), which was further divided into smaller voxels. The smallest voxel size was 1.25 × 1.25 × 3 mm(3). We found that the simulation time per history for the nonuniform voxels is about 30% to 40% faster than the uniform fine voxels (1.25 × 1.25 × 3 mm(3)) while maintaining similar accuracy.
NASA Technical Reports Server (NTRS)
Armstrong, T. W.; Bishop, B. L.
1972-01-01
Monte Carlo calculations have been carried out to determine the absorbed dose and dose equivalent for 592-MeV protons incident on a cylindrical phantom and for neutrons from 580-MeV proton-Be collisions incident on a semi-infinite phantom. For both configurations, the calculated depth dependence of the absorbed dose is in good agreement with experimental data.
Strenge, D.L.; Peloquin, R.A.
1981-04-01
The computer code HADOC (Hanford Acute Dose Calculations) is described and instructions for its use are presented. The code calculates external dose from air submersion and inhalation doses following acute radionuclide releases. Atmospheric dispersion is calculated using the Hanford model with options to determine maximum conditions. Building wake effects and terrain variation may also be considered. Doses are calculated using dose conversion factor supplied in a data library. Doses are reported for one and fifty year dose commitment periods for the maximum individual and the regional population (within 50 miles). The fractional contribution to dose by radionuclide and exposure mode are also printed if requested.
Limitations of the TG-43 formalism for skin high-dose-rate brachytherapy dose calculations
Granero, Domingo; Perez-Calatayud, Jose; Vijande, Javier; Ballester, Facundo; Rivard, Mark J.
2014-02-15
Purpose: In skin high-dose-rate (HDR) brachytherapy, sources are located outside, in contact with, or implanted at some depth below the skin surface. Most treatment planning systems use the TG-43 formalism, which is based on single-source dose superposition within an infinite water medium without accounting for the true geometry in which conditions for scattered radiation are altered by the presence of air. The purpose of this study is to evaluate the dosimetric limitations of the TG-43 formalism in HDR skin brachytherapy and the potential clinical impact. Methods: Dose rate distributions of typical configurations used in skin brachytherapy were obtained: a 5 cm × 5 cm superficial mould; a source inside a catheter located at the skin surface with and without backscatter bolus; and a typical interstitial implant consisting of an HDR source in a catheter located at a depth of 0.5 cm. Commercially available HDR{sup 60}Co and {sup 192}Ir sources and a hypothetical {sup 169}Yb source were considered. The Geant4 Monte Carlo radiation transport code was used to estimate dose rate distributions for the configurations considered. These results were then compared to those obtained with the TG-43 dose calculation formalism. In particular, the influence of adding bolus material over the implant was studied. Results: For a 5 cm × 5 cm{sup 192}Ir superficial mould and 0.5 cm prescription depth, dose differences in comparison to the TG-43 method were about −3%. When the source was positioned at the skin surface, dose differences were smaller than −1% for {sup 60}Co and {sup 192}Ir, yet −3% for {sup 169}Yb. For the interstitial implant, dose differences at the skin surface were −7% for {sup 60}Co, −0.6% for {sup 192}Ir, and −2.5% for {sup 169}Yb. Conclusions: This study indicates the following: (i) for the superficial mould, no bolus is needed; (ii) when the source is in contact with the skin surface, no bolus is needed for either {sup 60}Co and {sup 192}Ir. For
NASA Technical Reports Server (NTRS)
Ott, Lesley; Pickering, Kenneth; Stenchikov, Georgiy; Allen, Dale; DeCaria, Alex; Ridley, Brian; Lin, Ruei-Fong; Lang, Steve; Tao, Wei-Kuo
2009-01-01
A 3-D cloud scale chemical transport model that includes a parameterized source of lightning NO(x), based on observed flash rates has been used to simulate six midlatitude and subtropical thunderstorms observed during four field projects. Production per intracloud (P(sub IC) and cloud-to-ground (P(sub CG)) flash is estimated by assuming various values of P(sub IC) and P(sub CG) for each storm and determining which production scenario yields NO(x) mixing ratios that compare most favorably with in-cloud aircraft observations. We obtain a mean P(sub CG) value of 500 moles NO (7 kg N) per flash. The results of this analysis also suggest that on average, P(sub IC) may be nearly equal to P(sub CG), which is contrary to the common assumption that intracloud flashes are significantly less productive of NO than are cloud-to-ground flashes. This study also presents vertical profiles of the mass of lightning NO(x), after convection based on 3-D cloud-scale model simulations. The results suggest that following convection, a large percentage of lightning NO(x), remains in the middle and upper troposphere where it originated, while only a small percentage is found near the surface. The results of this work differ from profiles calculated from 2-D cloud-scale model simulations with a simpler lightning parameterization that were peaked near the surface and in the upper troposphere (referred to as a "C-shaped" profile). The new model results (a backward C-shaped profile) suggest that chemical transport models that assume a C-shaped vertical profile of lightning NO(x) mass may place too much mass neat the surface and too little in the middle troposphere.
Monte Carlo calculation of helical tomotherapy dose delivery
Zhao Yingli; Mackenzie, M.; Kirkby, C.; Fallone, B. G.
2008-08-15
Helical tomotherapy delivers intensity modulated radiation therapy using a binary multileaf collimator (MLC) to modulate a fan beam of radiation. This delivery occurs while the linac gantry and treatment couch are both in constant motion, so the beam describes, from a patient/phantom perspective, a spiral or helix of dose. The planning system models this continuous delivery as a large number (51) of discrete gantry positions per rotation, and given the small jaw/fan width setting typically used (1 or 2.5 cm) and the number of overlapping rotations used to cover the target (pitch often <0.5), the treatment planning system (TPS) potentially employs a very large number of static beam directions and leaf opening configurations to model the modulated fields. All dose calculations performed by the system employ a convolution/superposition model. In this work the authors perform a full Monte Carlo (MC) dose calculation of tomotherapy deliveries to phantom computed tomography (CT) data sets to verify the TPS calculations. All MC calculations are performed with the EGSnrc-based MC simulation codes, BEAMnrc and DOSXYZnrc. Simulations are performed by taking the sinogram (leaf opening versus time) of the treatment plan and decomposing it into 51 different projections per rotation, as does the TPS, each of which is segmented further into multiple MLC opening configurations, each with different weights that correspond to leaf opening times. Then the projection is simulated by the summing of all of the opening configurations, and the overall rotational treatment is simulated by the summing of all of the projection simulations. Commissioning of the source model was verified by comparing measured and simulated values for the percent depth dose and beam profiles shapes for various jaw settings. The accuracy of the MLC leaf width and tongue and groove spacing were verified by comparing measured and simulated values for the MLC leakage and a picket fence pattern. The validated source
Emergency Doses (ED) - Revision 3: A calculator code for environmental dose computations
Rittmann, P.D.
1990-12-01
The calculator program ED (Emergency Doses) was developed from several HP-41CV calculator programs documented in the report Seven Health Physics Calculator Programs for the HP-41CV, RHO-HS-ST-5P (Rittman 1984). The program was developed to enable estimates of offsite impacts more rapidly and reliably than was possible with the software available for emergency response at that time. The ED - Revision 3, documented in this report, revises the inhalation dose model to match that of ICRP 30, and adds the simple estimates for air concentration downwind from a chemical release. In addition, the method for calculating the Pasquill dispersion parameters was revised to match the GENII code within the limitations of a hand-held calculator (e.g., plume rise and building wake effects are not included). The summary report generator for printed output, which had been present in the code from the original version, was eliminated in Revision 3 to make room for the dispersion model, the chemical release portion, and the methods of looping back to an input menu until there is no further no change. This program runs on the Hewlett-Packard programmable calculators known as the HP-41CV and the HP-41CX. The documentation for ED - Revision 3 includes a guide for users, sample problems, detailed verification tests and results, model descriptions, code description (with program listing), and independent peer review. This software is intended to be used by individuals with some training in the use of air transport models. There are some user inputs that require intelligent application of the model to the actual conditions of the accident. The results calculated using ED - Revision 3 are only correct to the extent allowed by the mathematical models. 9 refs., 36 tabs.
Gamma Dose Calculations in the Target Service Cell of the SNS
Azmy, Y.Y.; Johnson, J.O.; Lillie, R.A.; Santoro, R.T.
1999-11-14
Calculations of the gamma dose rates inside and outside of the Target Service Cell (TSC) of the Spallation Neutron Source (SNS) are complicated by the large size of the structure, large volume of air (internal void), optical thickness of the enclosing walls, and multiplicity of radiation sources. Furthermore, a reasonably detailed distribution of the dose rate over the volume of the TSC, and on the outside of its walls is necessary in order to optimize electronic instrument locations, and plan access control. For all these reasons a deterministic transport method was preferred over Monte Carlo, The three- dimensional neutral particle transport code TORT was employed for this purpose with support from other peripheral codes in the Discrete Ordinates of Oak Ridge System (DOORS). The computational model for the TSC is described and the features of TORT and its companion codes that enable such a difficult calculation are discussed. Most prominent is the presence of severe ray effects in the air cavity of the TSC that persists in the transport through the concrete walls and is pronounced throughout the problem volume. Initial attempts at eliminating ray effects from the computed results using the newly developed three-dimensional uncollided flux and first collided source code GRTUNCL3D are described.
SU-E-I-06: A Dose Calculation Algorithm for KV Diagnostic Imaging Beams by Empirical Modeling
Chacko, M; Aldoohan, S; Sonnad, J; Ahmad, S; Ali, I
2015-06-15
Purpose: To develop accurate three-dimensional (3D) empirical dose calculation model for kV diagnostic beams for different radiographic and CT imaging techniques. Methods: Dose was modeled using photon attenuation measured using depth dose (DD), scatter radiation of the source and medium, and off-axis ratio (OAR) profiles. Measurements were performed using single-diode in water and a diode-array detector (MapCHECK2) with kV on-board imagers (OBI) integrated with Varian TrueBeam and Trilogy linacs. The dose parameters were measured for three energies: 80, 100, and 125 kVp with and without bowtie filters using field sizes 1×1–40×40 cm2 and depths 0–20 cm in water tank. Results: The measured DD decreased with depth in water because of photon attenuation, while it increased with field size due to increased scatter radiation from medium. DD curves varied with energy and filters where they increased with higher energies and beam hardening from half-fan and full-fan bowtie filters. Scatter radiation factors increased with field sizes and higher energies. The OAR was with 3% for beam profiles within the flat dose regions. The heal effect of this kV OBI system was within 6% from the central axis value at different depths. The presence of bowtie filters attenuated measured dose off-axis by as much as 80% at the edges of large beams. The model dose predictions were verified with measured doses using single point diode and ionization chamber or two-dimensional diode-array detectors inserted in solid water phantoms. Conclusion: This empirical model enables fast and accurate 3D dose calculation in water within 5% in regions with near charge-particle equilibrium conditions outside buildup region and penumbra. It considers accurately scatter radiation contribution in water which is superior to air-kerma or CTDI dose measurements used usually in dose calculation for diagnostic imaging beams. Considering heterogeneity corrections in this model will enable patient specific dose
An analytic linear accelerator source model for GPU-based Monte Carlo dose calculations.
Tian, Zhen; Li, Yongbao; Folkerts, Michael; Shi, Feng; Jiang, Steve B; Jia, Xun
2015-10-21
dose difference within 1.7%. The maximum relative difference of output factors was within 0.5%. Over 98.5% passing rate was achieved in 3D gamma-index tests with 2%/2 mm criteria in both an IMRT prostate patient case and a head-and-neck case. These results demonstrated the efficacy of our model in terms of accurately representing a reference phase-space file. We have also tested the efficiency gain of our source model over our previously developed phase-space-let file source model. The overall efficiency of dose calculation was found to be improved by ~1.3-2.2 times in water and patient cases using our analytical model.
An analytic linear accelerator source model for GPU-based Monte Carlo dose calculations.
Tian, Zhen; Li, Yongbao; Folkerts, Michael; Shi, Feng; Jiang, Steve B; Jia, Xun
2015-10-21
dose difference within 1.7%. The maximum relative difference of output factors was within 0.5%. Over 98.5% passing rate was achieved in 3D gamma-index tests with 2%/2 mm criteria in both an IMRT prostate patient case and a head-and-neck case. These results demonstrated the efficacy of our model in terms of accurately representing a reference phase-space file. We have also tested the efficiency gain of our source model over our previously developed phase-space-let file source model. The overall efficiency of dose calculation was found to be improved by ~1.3-2.2 times in water and patient cases using our analytical model. PMID:26418216
NASA Astrophysics Data System (ADS)
Tian, Zhen; Jiang Graves, Yan; Jia, Xun; Jiang, Steve B.
2014-10-01
Monte Carlo (MC) simulation is commonly considered as the most accurate method for radiation dose calculations. Commissioning of a beam model in the MC code against a clinical linear accelerator beam is of crucial importance for its clinical implementation. In this paper, we propose an automatic commissioning method for our GPU-based MC dose engine, gDPM. gDPM utilizes a beam model based on a concept of phase-space-let (PSL). A PSL contains a group of particles that are of the same type and close in space and energy. A set of generic PSLs was generated by splitting a reference phase-space file. Each PSL was associated with a weighting factor, and in dose calculations the particle carried a weight corresponding to the PSL where it was from. Dose for each PSL in water was pre-computed, and hence the dose in water for a whole beam under a given set of PSL weighting factors was the weighted sum of the PSL doses. At the commissioning stage, an optimization problem was solved to adjust the PSL weights in order to minimize the difference between the calculated dose and measured one. Symmetry and smoothness regularizations were utilized to uniquely determine the solution. An augmented Lagrangian method was employed to solve the optimization problem. To validate our method, a phase-space file of a Varian TrueBeam 6 MV beam was used to generate the PSLs for 6 MV beams. In a simulation study, we commissioned a Siemens 6 MV beam on which a set of field-dependent phase-space files was available. The dose data of this desired beam for different open fields and a small off-axis open field were obtained by calculating doses using these phase-space files. The 3D γ-index test passing rate within the regions with dose above 10% of dmax dose for those open fields tested was improved averagely from 70.56 to 99.36% for 2%/2 mm criteria and from 32.22 to 89.65% for 1%/1 mm criteria. We also tested our commissioning method on a six-field head-and-neck cancer IMRT plan. The
Monte Carlo prompt dose calculations for the National Ingition Facility
Latkowski, J.F.; Phillips, T.W.
1997-01-01
During peak operation, the National Ignition Facility (NIF) will conduct as many as 600 experiments per year and attain deuterium- tritium fusion yields as high as 1200 MJ/yr. The radiation effective dose equivalent (EDE) to workers is limited to an average of 03 mSv/yr (30 mrem/yr) in occupied areas of the facility. Laboratory personnel determined located outside the facility will receive EDEs <= 0.5 mSv/yr (<= 50 mrem/yr). The total annual occupational EDE for the facility will be maintained at <= 0.1 person-Sv/yr (<= 10 person- rem/yr). To ensure that prompt EDEs meet these limits, three- dimensional Monte Carlo calculations have been completed.
Considerations of beta and electron transport in internal dose calculations
Bolch, W.E.; Poston, J.W. Sr. . Dept. of Nuclear Engineering)
1990-12-01
Ionizing radiation has broad uses in modern science and medicine. These uses often require the calculation of energy deposition in the irradiated media and, usually, the medium of interest is the human body. Energy deposition from radioactive sources within the human body and the effects of such deposition are considered in the field of internal dosimetry. In July of 1988, a three-year research project was initiated by the Nuclear Engineering Department at Texas A M University under the sponsorship of the US Department of Energy. The main thrust of the research was to consider, for the first time, the detailed spatial transport of electron and beta particles in the estimation of average organ doses under the Medical Internal Radiation Dose (MIRD) schema. At the present time (December of 1990), research activities are continuing within five areas. Several are new initiatives begun within the second or third year of the current contract period. They include: (1) development of small-scale dosimetry; (2) development of a differential volume phantom; (3) development of a dosimetric bone model; (4) assessment of the new ICRP lung model; and (5) studies into the mechanisms of DNA damage. A progress report is given for each of these tasks within the Comprehensive Report. In each use, preliminary results are very encouraging and plans for further research are detailed within this document. 22 refs., 13 figs., 1 tab.
Considerations of beta and electron transport in internal dose calculations
Bolch, W.E.; Poston, J.W. Sr.
1990-12-01
Ionizing radiation has broad uses in modern science and medicine. These uses often require the calculation of energy deposition in the irradiated media and, usually, the medium of interest is the human body. Energy deposition from radioactive sources within the human body and the effects of such deposition are considered in the field of internal dosimetry. In July of 1988, a three-year research project was initiated by the Nuclear Engineering Department at Texas A M University under the sponsorship of the US Department of Energy. The main thrust of the research was to consider, for the first time, the detailed spatial transport of electron and beta particles in the estimation of average organ doses under the Medical Internal Radiation Dose (MIRD) schema. At the present time (December of 1990), research activities are continuing within five areas. Several are new initiatives begun within the second or third year of the current contract period. They include: (1) development of small-scale dosimetry; (2) development of a differential volume phantom; (3) development of a dosimetric bone model; (4) assessment of the new ICRP lung model; and (5) studies into the mechanisms of DNA damage. A progress report is given for each of these tasks within the Comprehensive Report. In each case, preliminary results are very encouraging and plans for further research are detailed within this document.
2013-10-01
Earth3D is a computer code designed to allow fast calculation of seismic rays and travel times through a 3D model of the Earth. LLNL is using this for earthquake location and global tomography efforts and such codes are of great interest to the Earth Science community.
NASA Astrophysics Data System (ADS)
Suzuki, W.; Aoi, S.; Maeda, T.; Sekiguchi, H.; Kunugi, T.
2013-12-01
Source inversion analysis using near-source strong-motion records with an assumption of 1-D underground structure models has revealed the overall characteristics of the rupture process of the 2011 Tohoku-Oki mega-thrust earthquake. This assumption for the structure model is acceptable because the seismic waves radiated during the Tohoku-Oki event were rich in the very-low-frequency contents lower than 0.05 Hz, which are less affected by the small-scale heterogeneous structure. The analysis using more reliable Green's functions even in the higher-frequency range considering complex structure of the subduction zone will illuminate more detailed rupture process in space and time and the transition of the frequency dependence of the wave radiation for the Tohoku-Oki earthquake. In this study, we calculate the near-source Green's functions using a 3-D underground structure model and perform the source inversion analysis using them. The 3-D underground structure model used in this study is the Japan Integrated Velocity Structure Model (Headquarters for Earthquake Research Promotion, 2012). A curved fault model on the Pacific plate interface is discretized into 287 subfaults at ~20 km interval. The Green's functions are calculated using GMS (Aoi et al., 2004), which is a simulation program package for the seismic wave field by the finite difference method using discontinuous grids (Aoi and Fujiwara, 1999). Computational region is 136-146.2E in longitude, 34-41.6N in latitude, and 0-100 km in depth. The horizontal and vertical grid intervals are 200 m and 100 m, respectively, for the shallower region and those for the deeper region are tripled. The number of the total grids is 2.1 billion. We derive 300-s records by calculating 36,000 steps with a time interval of 0.0083 second (120 Hz sampling). It takes nearly one hour to compute one case using 48 Graphics Processing Units (GPU) on TSUBAME2.0 supercomputer owned by Tokyo Institute of Technology. In total, 574 cases are
Kanematsu, Nobuyuki; Yonai, Shunsuke; Ishizaki, Azusa
2008-02-15
A new variant of the pencil-beam (PB) algorithm for dose distribution calculation for radiotherapy with protons and heavier ions, the grid-dose spreading (GDS) algorithm, is proposed. The GDS algorithm is intrinsically faster than conventional PB algorithms due to approximations in convolution integral, where physical calculations are decoupled from simple grid-to-grid energy transfer. It was effortlessly implemented to a carbon-ion radiotherapy treatment planning system to enable realistic beam blurring in the field, which was absent with the broad-beam (BB) algorithm. For a typical prostate treatment, the slowing factor of the GDS algorithm relative to the BB algorithm was 1.4, which is a great improvement over the conventional PB algorithms with a typical slowing factor of several tens. The GDS algorithm is mathematically equivalent to the PB algorithm for horizontal and vertical coplanar beams commonly used in carbon-ion radiotherapy while dose deformation within the size of the pristine spread occurs for angled beams, which was within 3 mm for a single 150-MeV proton pencil beam of 30 deg. incidence, and needs to be assessed against the clinical requirements and tolerances in practical situations.
Rana, Vijay K.; Rudin, Stephen; Bednarek, Daniel R.
2013-01-01
We have developed a dose-tracking system (DTS) to manage the risk of deterministic skin effects to the patient during fluoroscopic image-guided interventional cardiac procedures. The DTS calculates the radiation dose to the patient’s skin in real-time by acquiring exposure parameters and imaging-system geometry from the digital bus on a Toshiba C-arm unit and displays the cumulative dose values as a color map on a 3D graphic of the patient for immediate feedback to the interventionalist. Several recent updates have been made to the software to improve its function and performance. Whereas the older system needed manual input of pulse rate for dose-rate calculation and used the CPU clock with its potential latency to monitor exposure duration, each x-ray pulse is now individually processed to determine the skin-dose increment and to automatically measure the pulse rate. We also added a correction for the table pad which was found to reduce the beam intensity to the patient for under-table projections by an additional 5–12% over that of the table alone at 80 kVp for the x-ray filters on the Toshiba system. Furthermore, mismatch between the DTS graphic and the patient skin can result in inaccuracies in dose calculation because of inaccurate inverse-square-distance calculation. Therefore, a means for quantitative adjustment of the patient-graphic-model position and a parameterized patient-graphic library have been developed to allow the graphic to more closely match the patient. These changes provide more accurate estimation of the skin-dose which is critical for managing patient radiation risk. PMID:24817801
Rana, Vijay K; Rudin, Stephen; Bednarek, Daniel R
2013-03-01
We have developed a dose-tracking system (DTS) to manage the risk of deterministic skin effects to the patient during fluoroscopic image-guided interventional cardiac procedures. The DTS calculates the radiation dose to the patient's skin in real-time by acquiring exposure parameters and imaging-system geometry from the digital bus on a Toshiba C-arm unit and displays the cumulative dose values as a color map on a 3D graphic of the patient for immediate feedback to the interventionalist. Several recent updates have been made to the software to improve its function and performance. Whereas the older system needed manual input of pulse rate for dose-rate calculation and used the CPU clock with its potential latency to monitor exposure duration, each x-ray pulse is now individually processed to determine the skin-dose increment and to automatically measure the pulse rate. We also added a correction for the table pad which was found to reduce the beam intensity to the patient for under-table projections by an additional 5-12% over that of the table alone at 80 kVp for the x-ray filters on the Toshiba system. Furthermore, mismatch between the DTS graphic and the patient skin can result in inaccuracies in dose calculation because of inaccurate inverse-square-distance calculation. Therefore, a means for quantitative adjustment of the patient-graphic-model position and a parameterized patient-graphic library have been developed to allow the graphic to more closely match the patient. These changes provide more accurate estimation of the skin-dose which is critical for managing patient radiation risk.
NASA Astrophysics Data System (ADS)
Isaksson, Folke; Borg, Johan; Haglund, Leif
2008-04-01
In this paper the performance of passive range measurement imaging using stereo technique in real time applications is described. Stereo vision uses multiple images to get depth resolution in a similar way as Synthetic Aperture Radar (SAR) uses multiple measurements to obtain better spatial resolution. This technique has been used in photogrammetry for a long time but it will be shown that it is now possible to do the calculations, with carefully designed image processing algorithms, in e.g. a PC in real time. In order to get high resolution and quantitative data in the stereo estimation a mathematical camera model is used. The parameters to the camera model are settled in a calibration rig or in the case of a moving camera the scene itself can be used for calibration of most of the parameters. After calibration an ordinary TV camera has an angular resolution like a theodolite, but to a much lower price. The paper will present results from high resolution 3D imagery from air to ground. The 3D-results from stereo calculation of image pairs are stitched together into a large database to form a 3D-model of the area covered.
78 FR 64030 - Monitoring Criteria and Methods To Calculate Occupational Radiation Doses
Federal Register 2010, 2011, 2012, 2013, 2014
2013-10-25
... From the Federal Register Online via the Government Publishing Office NUCLEAR REGULATORY COMMISSION Monitoring Criteria and Methods To Calculate Occupational Radiation Doses AGENCY: Nuclear... monitoring and calculating occupational radiation doses. On December 4, 2007 (72 FR 68043), the NRC...
NASA Astrophysics Data System (ADS)
Datta, Soumendu; Kaphle, Gopi Chandra; Baral, Sayan; Mookerjee, Abhijit
2015-08-01
Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO)24 nanostructures with the impurity dopant atoms of the 3d late transition metals—Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO)24 nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties.
Datta, Soumendu; Kaphle, Gopi Chandra; Baral, Sayan; Mookerjee, Abhijit
2015-08-28
Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO)24 nanostructures with the impurity dopant atoms of the 3d late transition metals-Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO)24 nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties.
Schrempf, Michael; Haluza, Daniela; Simic, Stana; Riechelmann, Stefan; Graw, Kathrin; Seckmeyer, Gunther
2016-01-01
In a recent study, melanoma incidence rates for Austrian inhabitants living at higher altitudes were found to increase by as much as 30% per 100 m altitude. This strong increase cannot simply be explained by the known increase of erythemally-weighted irradiance with altitude, which ranges between 0.5% and 4% per 100 m. We assume that the discrepancy is partially explainable by upwelling UV radiation; e.g., reflected by snow-covered surfaces. Therefore, we present an approach where the human UV exposure is derived by integrating incident radiation over the 3D geometry of a human body, which enables us to take upwelling radiation into account. Calculating upwelling and downwelling radiance with a radiative transfer model for a snow-free valley and for snow-covered mountain terrain (with albedo of 0.6) yields an increase in UV exposure by 10% per 100 m altitude. The results imply that upwelling radiation plays a significant role in the increase of melanoma incidence with altitude. PMID:27690069
Datta, Soumendu Baral, Sayan; Mookerjee, Abhijit; Kaphle, Gopi Chandra
2015-08-28
Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO){sub 24} nanostructures with the impurity dopant atoms of the 3d late transition metals—Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO){sub 24} nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties.
Datta, Soumendu; Kaphle, Gopi Chandra; Baral, Sayan; Mookerjee, Abhijit
2015-08-28
Using density functional theory (DFT) based electronic structure calculations, the effects of morphology of semiconducting nanostructures on the magnetic interaction between two magnetic dopant atoms as well as a possibility of tuning band gaps have been studied in the case of the bi-doped (ZnO)24 nanostructures with the impurity dopant atoms of the 3d late transition metals-Mn, Fe, Co, Ni, and Cu. To explore the morphology effect, three different structures of the host (ZnO)24 nano-system, having different degrees of spatial confinement, have been considered: a two dimensional nanosheet, a one dimensional nanotube, and a finite cage-shaped nanocluster. The present study employs hybrid density functional theory to accurately describe the electronic structure of all the systems. It is shown here that the magnetic coupling between the two dopant atoms remains mostly anti-ferromagnetic in the course of changing the morphology from the sheet geometry to the cage-shaped geometry of the host systems, except for the case of energetically most stable bi-Mn doping, which shows a transition from ferromagnetic to anti-ferromagnetic coupling with decreasing aspect ratio of the host system. The effect of the shape change, however, has a significant effect on the overall band gap variations of both the pristine as well as all the bi-doped systems, irrespective of the nature of the dopant atoms and provides a means for easy tunability of their optoelectronic properties. PMID:26328845
Comparison of 2D and 3D gamma analyses
Pulliam, Kiley B.; Huang, Jessie Y.; Howell, Rebecca M.; Followill, David; Kry, Stephen F.; Bosca, Ryan; O’Daniel, Jennifer
2014-02-15
Purpose: As clinics begin to use 3D metrics for intensity-modulated radiation therapy (IMRT) quality assurance, it must be noted that these metrics will often produce results different from those produced by their 2D counterparts. 3D and 2D gamma analyses would be expected to produce different values, in part because of the different search space available. In the present investigation, the authors compared the results of 2D and 3D gamma analysis (where both datasets were generated in the same manner) for clinical treatment plans. Methods: Fifty IMRT plans were selected from the authors’ clinical database, and recalculated using Monte Carlo. Treatment planning system-calculated (“evaluated dose distributions”) and Monte Carlo-recalculated (“reference dose distributions”) dose distributions were compared using 2D and 3D gamma analysis. This analysis was performed using a variety of dose-difference (5%, 3%, 2%, and 1%) and distance-to-agreement (5, 3, 2, and 1 mm) acceptance criteria, low-dose thresholds (5%, 10%, and 15% of the prescription dose), and data grid sizes (1.0, 1.5, and 3.0 mm). Each comparison was evaluated to determine the average 2D and 3D gamma, lower 95th percentile gamma value, and percentage of pixels passing gamma. Results: The average gamma, lower 95th percentile gamma value, and percentage of passing pixels for each acceptance criterion demonstrated better agreement for 3D than for 2D analysis for every plan comparison. The average difference in the percentage of passing pixels between the 2D and 3D analyses with no low-dose threshold ranged from 0.9% to 2.1%. Similarly, using a low-dose threshold resulted in a difference between the mean 2D and 3D results, ranging from 0.8% to 1.5%. The authors observed no appreciable differences in gamma with changes in the data density (constant difference: 0.8% for 2D vs 3D). Conclusions: The authors found that 3D gamma analysis resulted in up to 2.9% more pixels passing than 2D analysis. It must
Williams, Greg; Tobler, Matthew; Gaffney, David; Moeller, John; Leavitt, Dennis D
2002-01-01
Computerized tomography (CT) is used routinely in evaluating radiation therapy isodose plans. With the introduction of 3D algorithms such as the voxel raytrace, which determines inhomogeneity corrections from actual CT Hounsfield numbers, caution must be used when evaluating isodose calculations. Artifacts from contrast media and dental work, radiopaque markers placed by the treatment planner, and changing bowel and rectal air patterns all have the potential to introduce error into the calculation due to inaccurate assessment of high or low density. Radiopaque makers such as x-spot BB's or solder wire are placed externally on the patient. Barium contrast media introduced at the time of simulation may be necessary to visualize specific anatomical structures on the CT images. While these localization and visualization tools may be necessary, it is important to understand the effects they may introduce in the planning process. Other problems encountered are patient specific and out of the control of the treatment planner. These include high- and low-density streaking caused by dental work, which produce computational errors due to overestimation, and small bowel and rectal air, the patterns of which change on a daily basis and may result in underestimation of structure density. It is important for each treatment planner to have an understanding of how this potentially tainted CT information may be applied in dose calculations and the possible effects they may have. At our institution, the voxel raytrace calculation is automatically forced any time couch angle is introduced. Errors in the calculation from the above mentioned situations may be introduced if a heterogeneity correction is applied. Examples of potential calculation errors and the magnitude of each will be discussed. The methods used to minimize these errors and the possible solutions will also be evaluated.
NASA Astrophysics Data System (ADS)
Sharkey, Keeper L.; Bubin, Sergiy; Adamowicz, Ludwik
2014-11-01
Accurate variational nonrelativistic quantum-mechanical calculations are performed for the five lowest 1D and four lowest 3D states of the 9Be isotope of the beryllium atom. All-electron explicitly correlated Gaussian (ECG) functions are used in the calculations and their nonlinear parameters are optimized with the aid of the analytical energy gradient determined with respect to these parameters. The effect of the finite nuclear mass is directly included in the Hamiltonian used in the calculations. The singlet-triplet energy gaps between the corresponding 1D and 3D states, are reported.
NASA Astrophysics Data System (ADS)
Rodrigo Rodríguez Cardozo, Félix; Hjörleifsdóttir, Vala
2015-04-01
One important ingredient in the study of the complex active tectonics in Mexico is the analysis of earthquake focal mechanisms, or the seismic moment tensor. They can be determined trough the calculation of Green functions and subsequent inversion for moment-tensor parameters. However, this calculation is gets progressively more difficult as the magnitude of the earthquakes decreases. Large earthquakes excite waves of longer periods that interact weakly with laterally heterogeneities in the crust. For these earthquakes, using 1D velocity models to compute the Greens fucntions works well. The opposite occurs for smaller and intermediate sized events, where the relatively shorter periods excited interact strongly with lateral heterogeneities in the crust and upper mantle and requires more specific or regional 3D models. In this study, we calculate Greens functions for earthquakes in Mexico using a laterally heterogeneous seismic wave speed model, comprised of mantle model S362ANI (Kustowski et al 2008) and crustal model CRUST 2.0 (Bassin et al 1990). Subsequently, we invert the observed seismograms for the seismic moment tensor using a method developed by Liu et al (2004) an implemented by Óscar de La Vega (2014) for earthquakes in Mexico. By following a brute force approach, in which we include all observed Rayleigh and Love waves of the Mexican National Seismic Network (Servicio Sismológico Naciona, SSN), we obtain reliable focal mechanisms for events that excite a considerable amount of low frequency waves (Mw > 4.8). However, we are not able to consistently estimate focal mechanisms for smaller events using this method, due to high noise levels in many of the records. Excluding the noisy records, or noisy parts of the records manually, requires interactive edition of the data, using an efficient tool for the editing. Therefore, we developed a graphical user interface (GUI), based on python and the python library ObsPy, that allows the edition of observed and
Laub, Wolfram U.; Nuesslin, Fridtjof
2003-12-31
In the present paper, dose distribution calculated with the Monte Carlo code EGS4 and with a pencil-beam algorithm are compared for the treatment of a pelvis with an implant. Overestimations of dose values inside the target volume by the pencil-beam algorithm of up to 10% were found, which are attributed to the underestimation of the absorption of photons by the implant. The differences in dose distributions are also expressed by comparing the tumor control probability (TCP) of the Monte Carlo dose calculations with the TCP of the pencil-beam calculations. A TCP reduction of order of 30% was found.
Considerations for applying VARSKIN mod 2 to skin dose calculations averaged over 10 cm2.
Durham, James S
2004-02-01
VARSKIN Mod 2 is a DOS-based computer program that calculates the dose to skin from beta and gamma contamination either directly on skin or on material in contact with skin. The default area for calculating the dose is 1 cm2. Recently, the U.S. Nuclear Regulatory Commission issued new guidelines for calculating shallow dose equivalent from skin contamination that requires the dose be averaged over 10 cm2. VARSKIN Mod 2 was not filly designed to calculate beta or gamma dose estimates averaged over 10 cm2, even though the program allows the user to calculate doses averaged over 10 cm2. This article explains why VARSKIN Mod 2 overestimates the beta dose when applied to 10 cm2 areas, describes a manual method for correcting the overestimate, and explains how to perform reasonable gamma dose calculations averaged over 10 cm2. The article also describes upgrades underway in Varskin 3. PMID:14744063
NASA Astrophysics Data System (ADS)
Hokkanen, T. M.; Hartikainen, A.; Raja-Halli, A.; Virtanen, H.; Makinen, J.
2015-12-01
INTRODUCTION The aim of this study is to construct a fine resolution time lapse groundwater (GW) model of Metsähovi (MH). GW, geological, and soil moisture (SM) data were collected for several years to achieve the goal. The knowledge of the behavior of the GW at local scale is essential for superconductive gravimeter (SG) investigations performing in MH. DESCRIPTION OF THE DATA Almost 50 sensors have been recorded SM data some 6 years with 1 to 5 minutes sampling frequency. The GW table has been monitored, both in bedrock and in soil, in many stages with all together 15 piezometers. Two geological sampling campaigns were conducted to get the knowledge of hydrological properties of soil in the study area of 200×200 m2 around SG station in MH. PRINCIPLE OF TIME LAPSE 3D HYDROGEOLOGICAL MODEL The model of study site consists of the surfaces of ground and bedrock gridded with 2×2 m2 resolution. The height of GW table was interpolated to 2×2×0.1 m3 grid between GW and SM monitoring points. Close to the outline of the study site and areas lacking of sensors GW table was defined by extrapolation and considering the geological information of the area. The bedrock porosity is 2% and soil porosity determined by geological information and SM recordings is from 5 to 35%. Only fully saturated media is considered in the time lapse model excluding unsaturated one. BENEFICIERS With a new model the fluctuation of GW table can be followed with ranging time lapses from 1 minute to 1 month. The gravity effect caused by the variation of GW table can be calculated more accurate than before in MH. Moreover, the new model can be validated and refined by measured gravity, i.e. hydrological model can be improved by SG recordings (Figure 1).
Van den Herrewegen, Inge; Cuppens, Kris; Broeckx, Mario; Barisch-Fritz, Bettina; Vander Sloten, Jos; Leardini, Alberto; Peeraer, Louis
2014-08-22
Multi-segmental foot kinematics have been analyzed by means of optical marker-sets or by means of inertial sensors, but never by markerless dynamic 3D scanning (D3DScanning). The use of D3DScans implies a radically different approach for the construction of the multi-segment foot model: the foot anatomy is identified via the surface shape instead of distinct landmark points. We propose a 4-segment foot model consisting of the shank (Sha), calcaneus (Cal), metatarsus (Met) and hallux (Hal). These segments are manually selected on a static scan. To track the segments in the dynamic scan, the segments of the static scan are matched on each frame of the dynamic scan using the iterative closest point (ICP) fitting algorithm. Joint rotations are calculated between Sha-Cal, Cal-Met, and Met-Hal. Due to the lower quality scans at heel strike and toe off, the first and last 10% of the stance phase is excluded. The application of the method to 5 healthy subjects, 6 trials each, shows a good repeatability (intra-subject standard deviations between 1° and 2.5°) for Sha-Cal and Cal-Met joints, and inferior results for the Met-Hal joint (>3°). The repeatability seems to be subject-dependent. For the validation, a qualitative comparison with joint kinematics from a corresponding established marker-based multi-segment foot model is made. This shows very consistent patterns of rotation. The ease of subject preparation and also the effective and easy to interpret visual output, make the present technique very attractive for functional analysis of the foot, enhancing usability in clinical practice.
Xu, Xuefei; Zhang, Wenjing; Tang, Mingsheng; Truhlar, Donald G.
2015-05-12
Coupled-cluster (CC) methods have been extensively used as the high-level approach in quantum electronic structure theory to predict various properties of molecules when experimental results are unavailable. It is often assumed that CC methods, if they include at least up to connected-triple-excitation quasiperturbative corrections to a full treatment of single and double excitations (in particular, CCSD(T)), and a very large basis set, are more accurate than Kohn–Sham (KS) density functional theory (DFT). In the present work, we tested and compared the performance of standard CC and KS methods on bond energy calculations of 20 3d transition metal-containing diatomic molecules against the most reliable experimental data available, as collected in a database called 3dMLBE20. It is found that, although the CCSD(T) and higher levels CC methods have mean unsigned deviations from experiment that are smaller than most exchange-correlation functionals for metal–ligand bond energies of transition metals, the improvement is less than one standard deviation of the mean unsigned deviation. Furthermore, on average, almost half of the 42 exchange-correlation functionals that we tested are closer to experiment than CCSD(T) with the same extended basis set for the same molecule. The results show that, when both relativistic and core–valence correlation effects are considered, even the very high-level (expensive) CC method with single, double, triple, and perturbative quadruple cluster operators, namely, CCSDT(2)Q, averaged over 20 bond energies, gives a mean unsigned deviation (MUD(20) = 4.7 kcal/mol when one correlates only valence, 3p, and 3s electrons of transition metals and only valence electrons of ligands, or 4.6 kcal/mol when one correlates all core electrons except for 1s shells of transition metals, S, and Cl); and that is similar to some good xc functionals (e.g., B97-1 (MUD(20) = 4.5 kcal/mol) and PW6B95 (MUD(20) = 4.9 kcal/mol)) when the same basis set is used
SU-E-T-162: Evaluation of Dose Calculation of RayStation Planning System in Heterogeneous Media
Xu, H; Yi, B; Chung, H; Prado, K; Chen, S
2014-06-01
Purpose: To investigate the clinical reliability of heterogeneity-based dose algorithm using RayStation treatment planning system v.4.0. Methods: The collapsed cone dose calculations in RayStation (RaySearch, Sweden) were compared with the measurements (ion chamber and EBT2 film) and with an in-house Monte Carlo algorithm. A heterogeneous multi-layer phantom and CT images of 4 lung cancer patients were used here. The phantom, composed of multiple solid water slabs and Styrofoams, was irradiated with 6MV beams perpendicular to the layers. The MLC-defined field sizes were 5×5, 10×10, 15×15 and 20×20cm{sup 2}. The chamber was positioned at center of central solid water layer, and the films were placed at interfaces of solid water and Styrofoam. The RayStation dose and Monte Carlo dose were compared by performing absolute gamma analysis (3mm/3%): 1D gamma for PDD in the phantom and 3D gamma for patient volumes receiving dose above 10% of maximum dose. Results: The point dose differences between RayStation and ion chamber measurement were smaller than 1% for all of the field sizes. Between RayStation and film measurement, 5×5cm2 field had the maximum differences : <4mm for the penumbra and <0.3mm for the field width at all Styrofoam-and-solid-water interfaces. The absolute gamma analysis showed good agreement between RayStation and Monte Carlo. For PDD along beam axis in the phantom, the 1D gamma was 95.4, 98.6, 99.6 and 99.3% for field size 5×5, 10×10, 15×15 and 20×202 respectively. For dose comparison using patient CT images, 3D gamma was > 95% for all the patients. Conclusion: With respect to ion chamber/film measurement and Monte Carlo calculation, the collapsed cone algorithm in RayStation computed reasonable dose in both phantom and patient cases. Heterogeneity-based dose calculation of RayStation is clinically acceptable in heterogeneous media.
Clinical applications of 3-D dosimeters
NASA Astrophysics Data System (ADS)
Wuu, Cheng-Shie
2015-01-01
Both 3-D gels and radiochromic plastic dosimeters, in conjunction with dose image readout systems (MRI or optical-CT), have been employed to measure 3-D dose distributions in many clinical applications. The 3-D dose maps obtained from these systems can provide a useful tool for clinical dose verification for complex treatment techniques such as IMRT, SRS/SBRT, brachytherapy, and proton beam therapy. These complex treatments present high dose gradient regions in the boundaries between the target and surrounding critical organs. Dose accuracy in these areas can be critical, and may affect treatment outcome. In this review, applications of 3-D gels and PRESAGE dosimeter are reviewed and evaluated in terms of their performance in providing information on clinical dose verification as well as commissioning of various treatment modalities. Future interests and clinical needs on studies of 3-D dosimetry are also discussed.
Napier, B.A.; Kennedy, W.E. Jr.; Soldat, J.K.
1980-03-01
A computer program, PABLM, was written to facilitate the calculation of internal radiation doses to man from radionuclides in food products and external radiation doses from radionuclides in the environment. This report contains details of mathematical models used and calculational procedures required to run the computer program. Radiation doses from radionuclides in the environment may be calculated from deposition on the soil or plants during an atmospheric or liquid release, or from exposure to residual radionuclides in the environment after the releases have ended. Radioactive decay is considered during the release of radionuclides, after they are deposited on the plants or ground, and during holdup of food after harvest. The radiation dose models consider several exposure pathways. Doses may be calculated for either a maximum-exposed individual or for a population group. The doses calculated are accumulated doses from continuous chronic exposure. A first-year committed dose is calculated as well as an integrated dose for a selected number of years. The equations for calculating internal radiation doses are derived from those given by the International Commission on Radiological Protection (ICRP) for body burdens and MPC's of each radionuclide. The radiation doses from external exposure to contaminated water and soil are calculated using the basic assumption that the contaminated medium is large enough to be considered an infinite volume or plane relative to the range of the emitted radiations. The equations for calculations of the radiation dose from external exposure to shoreline sediments include a correction for the finite width of the contaminated beach.
Monte Carlo calculation of skyshine'' neutron dose from ALS (Advanced Light Source)
Moin-Vasiri, M.
1990-06-01
This report discusses the following topics on skyshine'' neutron dose from ALS: Sources of radiation; ALS modeling for skyshine calculations; MORSE Monte-Carlo; Implementation of MORSE; Results of skyshine calculations from storage ring; and Comparison of MORSE shielding calculations.
Kusano, Maggie; Caldwell, Curtis B
2014-07-01
A primary goal of nuclear medicine facility design is to keep public and worker radiation doses As Low As Reasonably Achievable (ALARA). To estimate dose and shielding requirements, one needs to know both the dose equivalent rate constants for soft tissue and barrier transmission factors (TFs) for all radionuclides of interest. Dose equivalent rate constants are most commonly calculated using published air kerma or exposure rate constants, while transmission factors are most commonly calculated using published tenth-value layers (TVLs). Values can be calculated more accurately using the radionuclide's photon emission spectrum and the physical properties of lead, concrete, and/or tissue at these energies. These calculations may be non-trivial due to the polyenergetic nature of the radionuclides used in nuclear medicine. In this paper, the effects of dose equivalent rate constant and transmission factor on nuclear medicine dose and shielding calculations are investigated, and new values based on up-to-date nuclear data and thresholds specific to nuclear medicine are proposed. To facilitate practical use, transmission curves were fitted to the three-parameter Archer equation. Finally, the results of this work were applied to the design of a sample nuclear medicine facility and compared to doses calculated using common methods to investigate the effects of these values on dose estimates and shielding decisions. Dose equivalent rate constants generally agreed well with those derived from the literature with the exception of those from NCRP 124. Depending on the situation, Archer fit TFs could be significantly more accurate than TVL-based TFs. These results were reflected in the sample shielding problem, with unshielded dose estimates agreeing well, with the exception of those based on NCRP 124, and Archer fit TFs providing a more accurate alternative to TVL TFs and a simpler alternative to full spectral-based calculations. The data provided by this paper should assist
Kusano, Maggie; Caldwell, Curtis B
2014-07-01
A primary goal of nuclear medicine facility design is to keep public and worker radiation doses As Low As Reasonably Achievable (ALARA). To estimate dose and shielding requirements, one needs to know both the dose equivalent rate constants for soft tissue and barrier transmission factors (TFs) for all radionuclides of interest. Dose equivalent rate constants are most commonly calculated using published air kerma or exposure rate constants, while transmission factors are most commonly calculated using published tenth-value layers (TVLs). Values can be calculated more accurately using the radionuclide's photon emission spectrum and the physical properties of lead, concrete, and/or tissue at these energies. These calculations may be non-trivial due to the polyenergetic nature of the radionuclides used in nuclear medicine. In this paper, the effects of dose equivalent rate constant and transmission factor on nuclear medicine dose and shielding calculations are investigated, and new values based on up-to-date nuclear data and thresholds specific to nuclear medicine are proposed. To facilitate practical use, transmission curves were fitted to the three-parameter Archer equation. Finally, the results of this work were applied to the design of a sample nuclear medicine facility and compared to doses calculated using common methods to investigate the effects of these values on dose estimates and shielding decisions. Dose equivalent rate constants generally agreed well with those derived from the literature with the exception of those from NCRP 124. Depending on the situation, Archer fit TFs could be significantly more accurate than TVL-based TFs. These results were reflected in the sample shielding problem, with unshielded dose estimates agreeing well, with the exception of those based on NCRP 124, and Archer fit TFs providing a more accurate alternative to TVL TFs and a simpler alternative to full spectral-based calculations. The data provided by this paper should assist
Ikenberry, T.A.; Napier, B.A.
1992-12-01
A series of scoping calculations have been undertaken to evaluate The absolute and relative contribution of different exposure pathways to doses that may have been received by individuals living in the vicinity of the Hanford site. This scoping calculation (Calculation 001) examined the contributions of the various exposure pathways associated with environmental transport and accumulation of iodine-131 in the pasture-cow-milk pathway. Addressed in this calculation were the contributions to thyroid dose of infants and adult from (1) the ingestion by dairy cattle of various feedstuffs (pasturage, silage, alfalfa hay, and grass hay) in four different feeding regimes; (2) ingestion of soil by dairy cattle; (3) ingestion of stared feed on which airborne iodine-131 had been deposited; and (4) inhalation of airborne iodine-131 by dairy cows.
NASA Astrophysics Data System (ADS)
Sihver, L.; Mancusi, D.; Niita, K.; Sato, T.; Townsend, L.; Farmer, C.; Pinsky, L.; Ferrari, A.; Cerutti, F.; Gomes, I.
Particles and heavy ions are used in various fields of nuclear physics, medical physics, and material science, and their interactions with different media, including human tissue and critical organs, have therefore carefully been investigated both experimentally and theoretically since the 1930s. However, heavy-ion transport includes many complex processes and measurements for all possible systems, including critical organs, would be impractical or too expensive; e.g. direct measurements of dose equivalents to critical organs in humans cannot be performed. A reliable and accurate particle and heavy-ion transport code is therefore an essential tool in the design study of accelerator facilities as well as for other various applications. Recently, new applications have also arisen within transmutation and reactor science, space and medicine, especially radiotherapy, and several accelerator facilities are operating or planned for construction. Accurate knowledge of the physics of interaction of particles and heavy ions is also necessary for estimating radiation damage to equipment used on space vehicles, to calculate the transport of the heavy ions in the galactic cosmic ray (GCR) through the interstellar medium, and the evolution of the heavier elements after the Big Bang. Concerns about the biological effect of space radiation and space dosimetry are increasing rapidly due to the perspective of long-duration astronaut missions, both in relation to the International Space Station and to manned interplanetary missions in near future. Radiation protection studies for crews of international flights at high altitude have also received considerable attention in recent years. There is therefore a need to develop accurate and reliable particle and heavy-ion transport codes. To be able to calculate complex geometries, including production and transport of protons, neutrons, and alpha particles, 3-dimensional transport using Monte Carlo (MC) technique must be used. Today
Hanford Site Annual Report Radiological Dose Calculation Upgrade Evaluation
Snyder, Sandra F.
2010-02-28
Operations at the Hanford Site, Richland, Washington, result in the release of radioactive materials to offsite residents. Site authorities are required to estimate the dose to the maximally exposed offsite resident. Due to the very low levels of exposure at the residence, computer models, rather than environmental samples, are used to estimate exposure, intake, and dose. A DOS-based model has been used in the past (GENII version 1.485). GENII v1.485 has been updated to a Windows®-based software (GENII version 2.08). Use of the updated software will facilitate future dose evaluations, but must be demonstrated to provide results comparable to those of GENII v1.485. This report describes the GENII v1.485 and GENII v2.08 dose exposure, intake, and dose estimates for the maximally exposed offsite resident reported for calendar year 2008. The GENII v2.08 results reflect updates to implemented algorithms. No two environmental models produce the same results, as was again demonstrated in this report. The aggregated dose results from 2008 Hanford Site airborne and surface water exposure scenarios provide comparable dose results. Therefore, the GENII v2.08 software is recommended for future offsite resident dose evaluations.
Analysis of offsite dose calculation methodology for a nuclear power reactor
Moser, D.M.
1995-12-31
This technical study reviews the methodology for calculating offsite dose estimates as described in the offsite dose calculation manual (ODCM) for Pennsylvania Power and Light - Susquehanna Steam Electric Station (SSES). An evaluation of the SSES ODCM dose assessment methodology indicates that it conforms with methodology accepted by the US Nuclear Regulatory Commission (NRC). Using 1993 SSES effluent data, dose estimates are calculated according to SSES ODCM methodology and compared to the dose estimates calculated according to SSES ODCM and the computer model used to produce the reported 1993 dose estimates. The 1993 SSES dose estimates are based on the axioms of Publication 2 of the International Commission of Radiological Protection (ICRP). SSES Dose estimates based on the axioms of ICRP Publication 26 and 30 reveal the total body estimates to be the most affected.
Cowley, W.L.
1996-04-25
The analysis described in this report develops the Unit Liter Doses for use in the TWRS FSAR. The Unit Liter Doses provide a practical way to calculate conservative radiological consequences for a variety of potential accidents for the tank farms.
Three-Dimensional Dose Calculation for Total Body Irradiation
NASA Astrophysics Data System (ADS)
Ito, Akira
Bone Marrow Transplant (BMT) therapy has been a big success in the treatment of leukemia and other haematopoietic diseases 1 . Prior to BMT, total body irradiation (TBI) is given to the patient for the purpose of (1) killing leukemia cells in bone marrow, as well as in the whole body, and (2) producing immuno-suppressive status in the patient so that the donor's marrow cells will be transplanted without rejection. TBI employs a very large field photon beam to irradiate the whole body of the patient. A uniform dose distribution over the entire body is the treatment goal. To prevent the occurrence of a serious side effect (interstitial pneumonia), the lung dose should not exceed a certain level. This novel technique poses various new radiological physics problems. The accurate assessment of dose and dose distribution in the patient is essential. Physical and dosimetric problems associated with TBI are reviewed elsewhere 2,3 .
NASA Astrophysics Data System (ADS)
Pletinckx, D.
2011-09-01
The current 3D hype creates a lot of interest in 3D. People go to 3D movies, but are we ready to use 3D in our homes, in our offices, in our communication? Are we ready to deliver real 3D to a general public and use interactive 3D in a meaningful way to enjoy, learn, communicate? The CARARE project is realising this for the moment in the domain of monuments and archaeology, so that real 3D of archaeological sites and European monuments will be available to the general public by 2012. There are several aspects to this endeavour. First of all is the technical aspect of flawlessly delivering 3D content over all platforms and operating systems, without installing software. We have currently a working solution in PDF, but HTML5 will probably be the future. Secondly, there is still little knowledge on how to create 3D learning objects, 3D tourist information or 3D scholarly communication. We are still in a prototype phase when it comes to integrate 3D objects in physical or virtual museums. Nevertheless, Europeana has a tremendous potential as a multi-facetted virtual museum. Finally, 3D has a large potential to act as a hub of information, linking to related 2D imagery, texts, video, sound. We describe how to create such rich, explorable 3D objects that can be used intuitively by the generic Europeana user and what metadata is needed to support the semantic linking.
NASA Technical Reports Server (NTRS)
Bancroft, Gregory N.; Sikavitsas, Vassilios I.; van den Dolder, Juliette; Sheffield, Tiffany L.; Ambrose, Catherine G.; Jansen, John A.; Mikos, Antonios G.; McIntire, L. V. (Principal Investigator)
2002-01-01
Bone is a complex highly structured mechanically active 3D tissue composed of cellular and matrix elements. The true biological environment of a bone cell is thus derived from a dynamic interaction between responsively active cells experiencing mechanical forces and a continuously changing 3D matrix architecture. To investigate this phenomenon in vitro, marrow stromal osteoblasts were cultured on 3D scaffolds under flow perfusion with different rates of flow for an extended period to permit osteoblast differentiation and significant matrix production and mineralization. With all flow conditions, mineralized matrix production was dramatically increased over statically cultured constructs with the total calcium content of the cultured scaffolds increasing with increasing flow rate. Flow perfusion induced de novo tissue modeling with the formation of pore-like structures in the scaffolds and enhanced the distribution of cells and matrix throughout the scaffolds. These results represent reporting of the long-term effects of fluid flow on primary differentiating osteoblasts and indicate that fluid flow has far-reaching effects on osteoblast differentiation and phenotypic expression in vitro. Flow perfusion culture permits the generation and study of a 3D, actively modeled, mineralized matrix and can therefore be a valuable tool for both bone biology and tissue engineering.
NASA Astrophysics Data System (ADS)
Naik, Mehul S.
Intensity-modulated radiation therapy (IMRT) is a 3D conformal radiation therapy technique that utilizes either a multileaf intensity-modulating collimator (MIMiC used with the NOMOS Peacock system) or a multileaf collimator (MLC) on a conventional linear accelerator for beam intensity modulation to afford increased conformity in dose distributions. Due to the high-dose gradient regions that are effectively created, particular emphasis should be placed in the accurate determination of pencil beam kernels that are utilized by pencil beam convolution algorithms employed by a number of commercial IMRT treatment planning systems (TPS). These kernels are determined from relatively large field dose profiles that are typically collected using an ion chamber during commissioning of the TPS, while recent studies have demonstrated improvements in dose calculation accuracy when incorporating film data into the commissioning measurements. For this study, it has been proposed that the shape of high-resolution dose kernels can be extracted directly from single pencil beam (beamlet) profile measurements acquired using high-precision dosimetric film in order to accurately compute dose distributions, specifically for small fields and the penumbra regions of the larger fields. The effectiveness of GafChromic EBT film as an appropriate dosimeter to acquire the necessary measurements was evaluated and compared to the conventional silver-halide Kodak EDR2 film. Using the NOMOS Peacock system, similar dose kernels were extracted through deconvolution of the elementary pencil beam profiles using the two different types of films. Independent convolution-based calculations were performed using these kernels, resulting in better agreement with the measured relative dose profiles, as compared to those determined by CORVUS TPS' finite-size pencil beam (FSPB) algorithm. Preliminary evaluation of the proposed method in performing kernel extraction for an MLC-based IMRT system also showed
A Method for Correcting IMRT Optimizer Heterogeneity Dose Calculations
Zacarias, Albert S.; Brown, Mellonie F. Mills, Michael D.
2010-04-01
Radiation therapy treatment planning for volumes close to the patient's surface, in lung tissue and in the head and neck region, can be challenging for the planning system optimizer because of the complexity of the treatment and protected volumes, as well as striking heterogeneity corrections. Because it is often the goal of the planner to produce an isodose plan with uniform dose throughout the planning target volume (PTV), there is a need for improved planning optimization procedures for PTVs located in these anatomical regions. To illustrate such an improved procedure, we present a treatment planning case of a patient with a lung lesion located in the posterior right lung. The intensity-modulated radiation therapy (IMRT) plan generated using standard optimization procedures produced substantial dose nonuniformity across the tumor caused by the effect of lung tissue surrounding the tumor. We demonstrate a novel iterative method of dose correction performed on the initial IMRT plan to produce a more uniform dose distribution within the PTV. This optimization method corrected for the dose missing on the periphery of the PTV and reduced the maximum dose on the PTV to 106% from 120% on the representative IMRT plan.
Raisali, G; Davilu, H; Haghighishad, A; Khodadadi, R; Sabet, M
2006-01-01
In this research, total effective dose equivalent (TEDE) and collective dose (CD) are calculated for the most adverse potential accident in Bushehr Nuclear Power Plant from the viewpoint of radionuclides release to the environment. Calculations are performed using a Gaussian diffusion model and a slightly modified version of AIREM computer code to adopt for conditions in Bushehr. The results are comparable with the final safety analysis report which used DOZAM code. Results of our calculations show no excessive dose in populated regions. Maximum TEDE is determined to be in the WSW direction. CD in the area around the nuclear power plant by a distance of 30 km (138 man Sv) is far below the accepted limits. Thyroid equivalent dose is also calculated for the WSW direction (maximum 25.6 mSv) and is below the limits at various distances from the reactor stack.
Hardcastle, Nicholas; Bayliss, Adam; Wong, Jeannie Hsiu Ding; Rosenfeld, Anatoly B.; Tome, Wolfgang A.
2012-08-15
Purpose: A recent field safety notice from TomoTherapy detailed the underdosing of small, off-axis targets when receiving high doses per fraction. This is due to angular undersampling in the dose calculation gantry angles. This study evaluates a correction method to reduce the underdosing, to be implemented in the current version (v4.1) of the TomoTherapy treatment planning software. Methods: The correction method, termed 'Super Sampling' involved the tripling of the number of gantry angles from which the dose is calculated during optimization and dose calculation. Radiochromic film was used to measure the dose to small targets at various off-axis distances receiving a minimum of 21 Gy in one fraction. Measurements were also performed for single small targets at the center of the Lucy phantom, using radiochromic film and the dose magnifying glass (DMG). Results: Without super sampling, the peak dose deficit increased from 0% to 18% for a 10 mm target and 0% to 30% for a 5 mm target as off-axis target distances increased from 0 to 16.5 cm. When super sampling was turned on, the dose deficit trend was removed and all peak doses were within 5% of the planned dose. For measurements in the Lucy phantom at 9.7 cm off-axis, the positional and dose magnitude accuracy using super sampling was verified using radiochromic film and the DMG. Conclusions: A correction method implemented in the TomoTherapy treatment planning system which triples the angular sampling of the gantry angles used during optimization and dose calculation removes the underdosing for targets as small as 5 mm diameter, up to 16.5 cm off-axis receiving up to 21 Gy.
Napier, B.A.; Simpson, J.C.
1992-12-01
A series of scoping calculations has been undertaken to evaluate the doses that may have been received by individuals living in the vicinity of the Hanford site. This scoping calculation (Calculation 007) examined the spatial distribution of potential doses resulting from releases in the year 1945. This study builds on the work initiated in the first scoping calculation, of iodine in cow`s milk; the third scoping calculation, which added additional pathways; the fifth calculation, which addressed the uncertainty of the dose estimates at a point; and the sixth calculation, which extrapolated the doses throughout the atmospheric transport domain. A projection of dose to representative individuals throughout the proposed HEDR atmospheric transport domain was prepared on the basis of the HEDR source term. Addressed in this calculation were the contributions to iodine-131 thyroid dose of infants from (1) air submersion and groundshine external dose, (2) inhalation, (3) ingestion of soil by humans, (4) ingestion of leafy vegetables, (5) ingestion of other vegetables and fruits, (6) ingestion of meat, (7) ingestion of eggs, and (8) ingestion of cows` milk from-Feeding Regime 1 as described in scoping calculation 001.
Napier, B.A.
1992-12-01
A series of scoping calculations has been undertaken to evaluate the absolute and relative contributions of different radionuclides and exposure pathways to doses that may have been received by individuals living in the vicinity of the Hanford Site. This scoping calculation (Calculation 003) examined the contributions of numerous radionuclides to dose via environmental exposures and accumulation in foods. This study builds on the work initiated in the first scoping study of iodine in cow`s milk (calculation 001). Addressed in this calculation were the contributions to organ and effective dose of infants and adults from (1) air submersion and groundshine external dose, (2) inhalation, (3) ingestion of soil by humans, (4) ingestion of leafy vegetables, (5) ingestion of other vegetables and fruits, (6) ingestion of meat, (7) ingestion of eggs, and (8) ingestion of cows` milk from Feeding Regime 1, as described in Calculation 001.
Park, Yang-Kyun; Sharp, Gregory C.; Phillips, Justin; Winey, Brian A.
2015-01-01
Purpose: To demonstrate the feasibility of proton dose calculation on scatter-corrected cone-beam computed tomographic (CBCT) images for the purpose of adaptive proton therapy. Methods: CBCT projection images were acquired from anthropomorphic phantoms and a prostate patient using an on-board imaging system of an Elekta infinity linear accelerator. Two previously introduced techniques were used to correct the scattered x-rays in the raw projection images: uniform scatter correction (CBCTus) and a priori CT-based scatter correction (CBCTap). CBCT images were reconstructed using a standard FDK algorithm and GPU-based reconstruction toolkit. Soft tissue ROI-based HU shifting was used to improve HU accuracy of the uncorrected CBCT images and CBCTus, while no HU change was applied to the CBCTap. The degree of equivalence of the corrected CBCT images with respect to the reference CT image (CTref) was evaluated by using angular profiles of water equivalent path length (WEPL) and passively scattered proton treatment plans. The CBCTap was further evaluated in more realistic scenarios such as rectal filling and weight loss to assess the effect of mismatched prior information on the corrected images. Results: The uncorrected CBCT and CBCTus images demonstrated substantial WEPL discrepancies (7.3 ± 5.3 mm and 11.1 ± 6.6 mm, respectively) with respect to the CTref, while the CBCTap images showed substantially reduced WEPL errors (2.4 ± 2.0 mm). Similarly, the CBCTap-based treatment plans demonstrated a high pass rate (96.0% ± 2.5% in 2 mm/2% criteria) in a 3D gamma analysis. Conclusions: A priori CT-based scatter correction technique was shown to be promising for adaptive proton therapy, as it achieved equivalent proton dose distributions and water equivalent path lengths compared to those of a reference CT in a selection of anthropomorphic phantoms. PMID:26233175
PLOT3D/AMES, APOLLO UNIX VERSION USING GMR3D (WITHOUT TURB3D)
NASA Technical Reports Server (NTRS)
Buning, P.
1994-01-01
PLOT3D is an interactive graphics program designed to help scientists visualize computational fluid dynamics (CFD) grids and solutions. Today, supercomputers and CFD algorithms can provide scientists with simulations of such highly complex phenomena that obtaining an understanding of the simulations has become a major problem. Tools which help the scientist visualize the simulations can be of tremendous aid. PLOT3D/AMES offers more functions and features, and has been adapted for more types of computers than any other CFD graphics program. Version 3.6b+ is supported for five computers and graphic libraries. Using PLOT3D, CFD physicists can view their computational models from any angle, observing the physics of problems and the quality of solutions. As an aid in designing aircraft, for example, PLOT3D's interactive computer graphics can show vortices, temperature, reverse flow, pressure, and dozens of other characteristics of air flow during flight. As critical areas become obvious, they can easily be studied more closely using a finer grid. PLOT3D is part of a computational fluid dynamics software cycle. First, a program such as 3DGRAPE (ARC-12620) helps the scientist generate computational grids to model an object and its surrounding space. Once the grids have been designed and parameters such as the angle of attack, Mach number, and Reynolds number have been specified, a "flow-solver" program such as INS3D (ARC-11794 or COS-10019) solves the system of equations governing fluid flow, usually on a supercomputer. Grids sometimes have as many as two million points, and the "flow-solver" produces a solution file which contains density, x- y- and z-momentum, and stagnation energy for each grid point. With such a solution file and a grid file containing up to 50 grids as input, PLOT3D can calculate and graphically display any one of 74 functions, including shock waves, surface pressure, velocity vectors, and particle traces. PLOT3D's 74 functions are organized into
PLOT3D/AMES, APOLLO UNIX VERSION USING GMR3D (WITH TURB3D)
NASA Technical Reports Server (NTRS)
Buning, P.
1994-01-01
PLOT3D is an interactive graphics program designed to help scientists visualize computational fluid dynamics (CFD) grids and solutions. Today, supercomputers and CFD algorithms can provide scientists with simulations of such highly complex phenomena that obtaining an understanding of the simulations has become a major problem. Tools which help the scientist visualize the simulations can be of tremendous aid. PLOT3D/AMES offers more functions and features, and has been adapted for more types of computers than any other CFD graphics program. Version 3.6b+ is supported for five computers and graphic libraries. Using PLOT3D, CFD physicists can view their computational models from any angle, observing the physics of problems and the quality of solutions. As an aid in designing aircraft, for example, PLOT3D's interactive computer graphics can show vortices, temperature, reverse flow, pressure, and dozens of other characteristics of air flow during flight. As critical areas become obvious, they can easily be studied more closely using a finer grid. PLOT3D is part of a computational fluid dynamics software cycle. First, a program such as 3DGRAPE (ARC-12620) helps the scientist generate computational grids to model an object and its surrounding space. Once the grids have been designed and parameters such as the angle of attack, Mach number, and Reynolds number have been specified, a "flow-solver" program such as INS3D (ARC-11794 or COS-10019) solves the system of equations governing fluid flow, usually on a supercomputer. Grids sometimes have as many as two million points, and the "flow-solver" produces a solution file which contains density, x- y- and z-momentum, and stagnation energy for each grid point. With such a solution file and a grid file containing up to 50 grids as input, PLOT3D can calculate and graphically display any one of 74 functions, including shock waves, surface pressure, velocity vectors, and particle traces. PLOT3D's 74 functions are organized into
Calculates External and Inhalation Doses from Acute Radionuclide Releases on the Hanford Site.
1984-03-02
HADOC (Hanford Acute Dose Calculations) calculates external and inhalation doses resulting from postulated accidental radionuclide releases on the Hanford site. It generates doses to an individual at a specified location and to the population in the region near the Hanford site for specified organs. Doses reported include the maximally exposed individual's dose (by organ and exposure mode) and the total population dose (by organ and exposure mode) in the sector having the highest population exposuremore » factor. The first year and fifty-year dose commitments are reported. Optional reports giving the fractional contribution to total dose by radionuclide for each organ and dose commitment period for a maximally exposed individual and the population may be printed.« less
3d-3d correspondence revisited
NASA Astrophysics Data System (ADS)
Chung, Hee-Joong; Dimofte, Tudor; Gukov, Sergei; Sułkowski, Piotr
2016-04-01
In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d {N}=2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. We also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.
3d-3d correspondence revisited
Chung, Hee -Joong; Dimofte, Tudor; Gukov, Sergei; Sułkowski, Piotr
2016-04-21
In fivebrane compactifications on 3-manifolds, we point out the importance of all flat connections in the proper definition of the effective 3d N = 2 theory. The Lagrangians of some theories with the desired properties can be constructed with the help of homological knot invariants that categorify colored Jones polynomials. Higgsing the full 3d theories constructed this way recovers theories found previously by Dimofte-Gaiotto-Gukov. As a result, we also consider the cutting and gluing of 3-manifolds along smooth boundaries and the role played by all flat connections in this operation.
Sampson, Andrew; Le, Yi; Williamson, Jeffrey F.
2012-01-01
Purpose: To demonstrate potential of correlated sampling Monte Carlo (CMC) simulation to improve the calculation efficiency for permanent seed brachytherapy (PSB) implants without loss of accuracy. Methods: CMC was implemented within an in-house MC code family (PTRAN) and used to compute 3D dose distributions for two patient cases: a clinical PSB postimplant prostate CT imaging study and a simulated post lumpectomy breast PSB implant planned on a screening dedicated breast cone-beam CT patient exam. CMC tallies the dose difference, ΔD, between highly correlated histories in homogeneous and heterogeneous geometries. The heterogeneous geometry histories were derived from photon collisions sampled in a geometrically identical but purely homogeneous medium geometry, by altering their particle weights to correct for bias. The prostate case consisted of 78 Model-6711 125I seeds. The breast case consisted of 87 Model-200 103Pd seeds embedded around a simulated lumpectomy cavity. Systematic and random errors in CMC were unfolded using low-uncertainty uncorrelated MC (UMC) as the benchmark. CMC efficiency gains, relative to UMC, were computed for all voxels, and the mean was classified in regions that received minimum doses greater than 20%, 50%, and 90% of D90, as well as for various anatomical regions. Results: Systematic errors in CMC relative to UMC were less than 0.6% for 99% of the voxels and 0.04% for 100% of the voxels for the prostate and breast cases, respectively. For a 1 × 1 × 1 mm3 dose grid, efficiency gains were realized in all structures with 38.1- and 59.8-fold average gains within the prostate and breast clinical target volumes (CTVs), respectively. Greater than 99% of the voxels within the prostate and breast CTVs experienced an efficiency gain. Additionally, it was shown that efficiency losses were confined to low dose regions while the largest gains were located where little difference exists between the homogeneous and heterogeneous doses
NIF Ignition Target 3D Point Design
Jones, O; Marinak, M; Milovich, J; Callahan, D
2008-11-05
We have developed an input file for running 3D NIF hohlraums that is optimized such that it can be run in 1-2 days on parallel computers. We have incorporated increasing levels of automation into the 3D input file: (1) Configuration controlled input files; (2) Common file for 2D and 3D, different types of capsules (symcap, etc.); and (3) Can obtain target dimensions, laser pulse, and diagnostics settings automatically from NIF Campaign Management Tool. Using 3D Hydra calculations to investigate different problems: (1) Intrinsic 3D asymmetry; (2) Tolerance to nonideal 3D effects (e.g. laser power balance, pointing errors); and (3) Synthetic diagnostics.
[Development of a software for 3D virtual phantom design].
Zou, Lian; Xie, Zhao; Wu, Qi
2014-02-01
In this paper, we present a 3D virtual phantom design software, which was developed based on object-oriented programming methodology and dedicated to medical physics research. This software was named Magical Phan tom (MPhantom), which is composed of 3D visual builder module and virtual CT scanner. The users can conveniently construct any complex 3D phantom, and then export the phantom as DICOM 3.0 CT images. MPhantom is a user-friendly and powerful software for 3D phantom configuration, and has passed the real scene's application test. MPhantom will accelerate the Monte Carlo simulation for dose calculation in radiation therapy and X ray imaging reconstruction algorithm research. PMID:24804488
Calculation of Radiation Doses from Uranium Recovery Operations.
1980-12-08
Version: 00 MILDOS estimates impacts from radioactive emissions from uranium milling facilities. These impacts are presented as dose commitments to individuals and the regional population within an 80 km radius of the facility. Only airborne releases of radioactive materials are considered: releases to surface water and to groundwater are not addressed in MILDOS. This is a multi-purpose code system, within the range of its proper application, and can be used to evaluate population doses formore » NEPA assessments, maximum individual doses for predictive 40 CFR 190 compliance evaluations, or maximum offsite air concentrations for predictive evaluations of 10 CFR 20 compliance. The MILDOS package includes models for both point sources (stacks, vents) and area sources (ore pads, tailings areas). Gaseous releases are limited to consideration of 222Rn plus ingrowth of daughters. Exposure pathways of concern are assumed to be inhalation of airborne radioactive material, ingestion of vegetables, meat, and milk contaminated via deposition, and external exposure to radiation emitted by airborne activity and activity deposited on ground surfaces. Liquid exposure pathways are not treated by MILDOS.« less
Recommended environmental dose calculation methods and Hanford-specific parameters
Schreckhise, R.G.; Rhoads, K.; Napier, B.A.; Ramsdell, J.V. ); Davis, J.S. )
1993-03-01
This document was developed to support the Hanford Environmental Dose overview Panel (HEDOP). The Panel is responsible for reviewing all assessments of potential doses received by humans and other biota resulting from the actual or possible environmental releases of radioactive and other hazardous materials from facilities and/or operations belonging to the US Department of Energy on the Hanford Site in south-central Washington. This document serves as a guide to be used for developing estimates of potential radiation doses, or other measures of risk or health impacts, to people and other biota in the environs on and around the Hanford Site. It provides information to develop technically sound estimates of exposure (i.e., potential or actual) to humans or other biotic receptors that could result from the environmental transport of potentially harmful materials that have been, or could be, released from Hanford operations or facilities. Parameter values and information that are specific to the Hanford environs as well as other supporting material are included in this document.
NASA Astrophysics Data System (ADS)
Alaei, Parham
2000-11-01
A number of procedures in diagnostic radiology and cardiology make use of long exposures to x rays from fluoroscopy units. Adverse effects of these long exposure times on the patients' skin have been documented in recent years. These include epilation, erythema, and, in severe cases, moist desquamation and tissue necrosis. Potential biological effects from these exposures to other organs include radiation-induced cataracts and pneumonitis. Although there have been numerous studies to measure or calculate the dose to skin from these procedures, there have only been a handful of studies to determine the dose to other organs. Therefore, there is a need for accurate methods to measure the dose in tissues and organs other than the skin. This research was concentrated in devising a method to determine accurately the radiation dose to these tissues and organs. The work was performed in several stages: First, a three dimensional (3D) treatment planning system used in radiation oncology was modified and complemented to make it usable with the low energies of x rays used in diagnostic radiology. Using the system for low energies required generation of energy deposition kernels using Monte Carlo methods. These kernels were generated using the EGS4 Monte Carlo system of codes and added to the treatment planning system. Following modification, the treatment planning system was evaluated for its accuracy of calculations in low energies within homogeneous and heterogeneous media. A study of the effects of lungs and bones on the dose distribution was also performed. The next step was the calculation of dose distributions in humanoid phantoms using this modified system. The system was used to calculate organ doses in these phantoms and the results were compared to those obtained from other methods. These dose distributions can subsequently be used to create dose-volume histograms (DVHs) for internal organs irradiated by these beams. Using this data and the concept of normal tissue
The polyGeVero® software for fast and easy computation of 3D radiotherapy dosimetry data
NASA Astrophysics Data System (ADS)
Kozicki, Marek; Maras, Piotr
2015-01-01
The polyGeVero® software package was elaborated for calculations of 3D dosimetry data such as the polymer gel dosimetry. It comprises four workspaces designed for: i) calculating calibrations, ii) storing calibrations in a database, iii) calculating dose distribution 3D cubes, iv) comparing two datasets e.g. a measured one with a 3D dosimetry with a calculated one with the aid of a treatment planning system. To accomplish calculations the software was equipped with a number of tools such as the brachytherapy isotopes database, brachytherapy dose versus distance calculation based on the line approximation approach, automatic spatial alignment of two 3D dose cubes for comparison purposes, 3D gamma index, 3D gamma angle, 3D dose difference, Pearson's coefficient, histograms calculations, isodoses superimposition for two datasets, and profiles calculations in any desired direction. This communication is to briefly present the main functions of the software and report on the speed of calculations performed by polyGeVero®.
Estimation of Nuclear Reaction Effects in Proton-Tissue-Dose Calculations.
1983-01-14
Version 00 REPC reviews calculational methods for the estimation of dose from external proton exposure of arbitrary convex bodies and presents the necessary information for the estimation of dose in soft tissue. The effects of nuclear reactions, especially in relation to the dose equivalent, are retained. REPC subroutines can be used to convert existing computer programs which neglect nuclear reaction effects to include them.
NASA Astrophysics Data System (ADS)
Laforsch, C.; Christoph, E.; Glaser, C.; Naumann, M.; Wild, C.; Niggl, W.
2008-12-01
The surface area of corals represents a major reference parameter for the standardization of flux rates, for coral growth investigations, and for investigations of coral metabolism. The methods currently used to determine the surface area of corals are rather approximate approaches lacking accuracy, or are invasive and often destructive methods that are inapplicable for experiments involving living corals. This study introduces a novel precise and non-destructive technique to quantify surface area in living coral colonies by applying computed tomography (CT) and subsequent 3D reconstruction. Living coral colonies of different taxa were scanned by conventional medical CT either in air or in sea water. Resulting data volumes were processed by 3D modeling software providing realistic 3D coral skeleton surface reconstructions, thus enabling surface area measurements. Comparisons of CT datasets obtained from calibration bodies and coral colonies proved the accuracy of the surface area determination. Surface area quantifications derived from two different surface rendering techniques applied for scanning living coral colonies showed congruent results (mean deviation ranging from 1.32 to 2.03%). The validity of surface area measurement was verified by repeated measurements of the same coral colonies by three test persons. No significant differences between all test persons in all coral genera and in both surface rendering techniques were found (independent sample t-test: all n.s.). Data analysis of a single coral colony required approximately 15 to 30 min for a trained user using the isosurface technique regardless of the complexity and growth form of the latter, rendering the method presented in this study as a time-saving and accurate method to quantify surface areas in both living coral colonies and bare coral skeletons.
Lefebvre, L; Doyeux, K; Linca, S; Challand, T; Hanzen, C
2014-12-01
The purpose was to assess three treatments planning techniques including one in intensity-modulated radiation therapy (IMRT) for cerebral irradiation of pregnant woman, in order to limit the dose delivered to the foetus. The treatment provided was 60 Gy to the planning target volume. Estimated foetal dose was measured using an anthropomorphic phantom, on the upper and middle part of the uterus. The first plan consisted in four beams in conformational technique delivered from a Varian accelerator with a 120 leaves collimator, the second one used non-coplanar fields and the third one assessed IMRT. With the conformational technique, the dose at the upper part of the uterus was 8.3 mGy and 6.3 mGy at the middle part. The dose delivered to the foetus was higher with the non-coplanar fields. In IMRT, the dose at the upper part of the uterus was 23.8 mGy and 14.3 mGy at the middle part. The three plans used 6 MV X-rays. Because of the use of leaves and non-coplanar fields, IMRT does not seem to be the optimal technique for the treatment of pregnant woman. However, the dose delivered to the foetus remains low and below the dose of 100 mGy recommended by the International Commission of Radiological Protection. It seems possible to consider the use of this technique for a better sparing of organs at risk for the mother.
Tol-Geerdink, Julia J. van . E-mail: J.vanTol@rther.umcn.nl; Stalmeier, Peep F.M.; Pasker-de Jong, Pieternel C.M.; Huizenga, Henk; Lin, Emile N.J.T. van; Schimmel, Erik C.; Leer, Jan Willem; Daal, Willem A.J. van
2006-02-01
Purpose: A higher radiation dose is believed to result in a larger probability of tumor control and a higher risk of side effects. To make an evidence-based choice of dose, the relation between dose and outcome needs to be known. This study focuses on the dose-response relation for prostate cancer. Methods and Materials: A systematic review was carried out on the literature from 1990 to 2003. From the selected studies, the radiation dose, the associated 5-year survival, 5-year bNED (biochemical no evidence of disease), acute and late gastrointestinal (GI) and genitourinary (GU) morbidity Grade 2 or more, and sexual dysfunction were extracted. With logistic regression models, the relation between dose and outcome was described. Results: Thirty-eight studies met our criteria, describing 87 subgroups and involving up to 3000 patients per outcome measure. Between the (equivalent) dose of 70 and 80 Gy, various models estimated an increase in 5-year survival (ranging from 10% to 11%), 5-year bNED for low-risk patients (5-7%), late GI complications (12-16%), late GU complications (8-10%), and erectile dysfunction (19-24%). Only for the overall 5-year bNED, results were inconclusive (range, 0-18%). Conclusions: The data suggest a relationship between dose and outcome measures, including survival. However, the strength of these conclusions is limited by the sometimes small number of studies, the incompleteness of the data, and above all, the correlational nature of the data. Unambiguous proof for the dose-response relationships can, therefore, only be obtained by conducting randomized trials.
NASA Astrophysics Data System (ADS)
Avery, S.; Cardin, A.; Lin, L.; Kirk, M.; Kassaee, A.; Maryanski, M. J.
2015-01-01
This paper is intended as a preliminary study to demonstrate the quality assurance benefits from polymer gel detectors for proton pencil beam cranio-spinal treatments. A stable gel type was selected for protons to suppress the LET dependence at the end of the Bragg peak. The depth dose distributions in the gels were examined with regard of its dose dependences and compared to baseline measurements. The preliminary experimental results indicate polymer gel detectors may be able to verify dose in three dimensions along match line for proton therapy treatments.
RADIATION DOSE CALCULATION FOR FUEL HANDLING FACILITY CLOSURE CELL EQUIPMENT
D. Musat
2005-03-07
This calculation evaluates the energy deposition rates in silicon, gamma and neutron flux spectra at various locations of interest throughout FHF closure cell. The physical configuration features a complex geometry, with particle flux attenuation of many orders of magnitude that cannot be modeled by computer codes that use deterministic methods. Therefore, in this calculation the Monte Carlo method was used to solve the photon and neutron transport. In contrast with the deterministic methods, Monte Carlo does not solve an explicit transport equation, but rather obtain answers by simulating individual particles, recording the aspects of interest of their average behavior, and estimates the statistical precision of the results.
Calculating integral dose using data exported from a commercial record and verify system.
Fox, C; Hardcastle, N; Lim, A; Khor, R
2015-06-01
Integral dose has been useful in investigations into the incidence of second primary malignancies in radiotherapy patients. This note outlines an approach to calculation of integral dose for a group of prostate patients using only data exported from a commercial record and verify system. Even though it was necessary to make some assumptions about patient anatomy, comparison with integral dose calculated from data exported from the planning system showed good agreement. PMID:25869674
Effect of Embolization Material in the Calculation of Dose Deposition in Arteriovenous Malformations
De la Cruz, O. O. Galvan; Moreno-Jimenez, S.; Larraga-Gutierrez, J. M.; Celis-Lopez, M. A.
2010-12-07
In this work it is studied the impact of the incorporation of high Z materials (embolization material) in the dose calculation for stereotactic radiosurgery treatment for arteriovenous malformations. A statistical analysis is done to establish the variables that may impact in the dose calculation. To perform the comparison pencil beam (PB) and Monte Carlo (MC) calculation algorithms were used. The comparison between both dose calculations shows that PB overestimates the dose deposited. The statistical analysis, for the quantity of patients of the study (20), shows that the variable that may impact in the dose calculation is the volume of the high Z material in the arteriovenous malformation. Further studies have to be done to establish the clinical impact with the radiosurgery result.
Effect of Embolization Material in the Calculation of Dose Deposition in Arteriovenous Malformations
NASA Astrophysics Data System (ADS)
De la Cruz, O. O. Galván; Lárraga-Gutiérrez, J. M.; Moreno-Jiménez, S.; Célis-López, M. A.
2010-12-01
In this work it is studied the impact of the incorporation of high Z materials (embolization material) in the dose calculation for stereotactic radiosurgery treatment for arteriovenous malformations. A statistical analysis is done to establish the variables that may impact in the dose calculation. To perform the comparison pencil beam (PB) and Monte Carlo (MC) calculation algorithms were used. The comparison between both dose calculations shows that PB overestimates the dose deposited. The statistical analysis, for the quantity of patients of the study (20), shows that the variable that may impact in the dose calculation is the volume of the high Z material in the arteriovenous malformation. Further studies have to be done to establish the clinical impact with the radiosurgery result.
NASA Astrophysics Data System (ADS)
Meulien Ohlmann, Odile
2013-02-01
Today the industry offers a chain of 3D products. Learning to "read" and to "create in 3D" becomes an issue of education of primary importance. 25 years professional experience in France, the United States and Germany, Odile Meulien set up a personal method of initiation to 3D creation that entails the spatial/temporal experience of the holographic visual. She will present some different tools and techniques used for this learning, their advantages and disadvantages, programs and issues of educational policies, constraints and expectations related to the development of new techniques for 3D imaging. Although the creation of display holograms is very much reduced compared to the creation of the 90ies, the holographic concept is spreading in all scientific, social, and artistic activities of our present time. She will also raise many questions: What means 3D? Is it communication? Is it perception? How the seeing and none seeing is interferes? What else has to be taken in consideration to communicate in 3D? How to handle the non visible relations of moving objects with subjects? Does this transform our model of exchange with others? What kind of interaction this has with our everyday life? Then come more practical questions: How to learn creating 3D visualization, to learn 3D grammar, 3D language, 3D thinking? What for? At what level? In which matter? for whom?
Napier, B.A.; Simpson, J.C.
1992-12-01
A series of scoping calculations has been undertaken to evaluate the radiation doses that may have-been received by individuals living in the vicinity of the Hanford site. This scoping calculation (Calculation 008) examined the potential for changes in the uncertainty distributions of potential doses from releases in the year 1945 as a function of temporal resolution of the intermediate data storage. This study builds on the work initiated in the fifth scoping calculation, which addressed the uncertainty of the dose estimates at a point; the sixth calculation, which extrapolated the doses throughout the atmospheric transport domain; and the seventh, which evaluated the spatial scales across the domain. A projection of dose to representative individuals throughout the proposed HEDR atmospheric transport domain was prepared on the basis of the HEDR source term. Addressed in this calculation were the contributions to iodine-131 thyroid dose of infants from (1) air submersion and groundshine external dose, (2) inhalation, (3) ingestion of soil by humans, (4) ingestion of leafy vegetables, (5) ingestion of other vegetables and fruits, (6) ingestion of meat, (7) ingestion of eggs, and ingestion of cow`s milk.
NASA Technical Reports Server (NTRS)
2004-01-01
This 3-D, microscopic imager mosaic of a target area on a rock called 'Diamond Jenness' was taken after NASA's Mars Exploration Rover Opportunity ground into the surface with its rock abrasion tool for a second time.
Opportunity has bored nearly a dozen holes into the inner walls of 'Endurance Crater.' On sols 177 and 178 (July 23 and July 24, 2004), the rover worked double-duty on Diamond Jenness. Surface debris and the bumpy shape of the rock resulted in a shallow and irregular hole, only about 2 millimeters (0.08 inch) deep. The final depth was not enough to remove all the bumps and leave a neat hole with a smooth floor. This extremely shallow depression was then examined by the rover's alpha particle X-ray spectrometer.
On Sol 178, Opportunity's 'robotic rodent' dined on Diamond Jenness once again, grinding almost an additional 5 millimeters (about 0.2 inch). The rover then applied its Moessbauer spectrometer to the deepened hole. This double dose of Diamond Jenness enabled the science team to examine the rock at varying layers. Results from those grindings are currently being analyzed.
The image mosaic is about 6 centimeters (2.4 inches) across.
Utilising pseudo-CT data for dose calculation and plan optimization in adaptive radiotherapy.
Whelan, Brendan; Kumar, Shivani; Dowling, Jason; Begg, Jarrad; Lambert, Jonathan; Lim, Karen; Vinod, Shalini K; Greer, Peter B; Holloway, Lois
2015-12-01
To quantify the dose calculation error and resulting optimization uncertainty caused by performing inverse treatment planning on inaccurate electron density data (pseudo-CT) as needed for adaptive radiotherapy and Magnetic Resonance Imaging (MRI) based treatment planning. Planning Computer Tomography (CT) data from 10 cervix cancer patients was used to generate 4 pseudo-CT data sets. Each pseudo-CT was created based on an available method of assigning electron density to an anatomic image. An inversely modulated radiotherapy (IMRT) plan was developed on each planning CT. The dose calculation error caused by each pseudo-CT data set was quantified by comparing the dose calculated each pseudo-CT data set with that calculated on the original planning CT for the same IMRT plan. The optimization uncertainty introduced by the dose calculation error was quantified by re-optimizing the same optimization parameters on each pseudo-CT data set and comparing against the original planning CT. Dose differences were quantified by assessing the Equivalent Uniform Dose (EUD) for targets and relevant organs at risk. Across all pseudo-CT data sets and all organs, the absolute mean dose calculation error was 0.2 Gy, and was within 2 % of the prescription dose in 98.5 % of cases. Then absolute mean optimisation error was 0.3 Gy EUD, indicating that that inverse optimisation is impacted by the dose calculation error. However, the additional uncertainty introduced to plan optimisation is small compared the sources of variation which already exist. Use of inaccurate electron density data for inverse treatment planning results in a dose calculation error, which in turn introduces additional uncertainty into the plan optimization process. In this study, we showed that both of these effects are clinically acceptable for cervix cancer patients using four different pseudo-CT data sets. Dose calculation and inverse optimization on pseudo-CT is feasible for this patient cohort.
Aliasgharzadeh, Akbar; Mihandoost, Ehsan; Masoumbeigi, Mahboubeh; Salimian, Morteza; Mohseni, Mehran
2015-01-01
The knowledge of the radiation dose received by the patient during the radiological examination is essential to prevent risks of exposures. The aim of this work is to study patient doses for common diagnostic radiographic examinations in hospitals affiliated to Kashan University of Medical sciences, Iran. The results of this survey are compared with those published by some national and international values. Entrance surface dose (ESD) was measured based on the exposure parameters used for the actual examination and effective dose (ED) was calculated by use of conversion coefficients calculated by Monte Carlo methods. The mean entrance surface dose and effective dose for examinations of the chest (PA, Lat), abdomen (AP), pelvis (AP), lumbar spine (AP, Lat) and skull (AP, Lat) are 0.37, 0.99, 2.01, 1.76, 2.18, 5.36, 1.39 and 1.01 mGy, and 0.04, 0.1, 0.28, 0,28, 0.23, 0.13, 0.01 and 0.01 mSv, respectively. The ESDs and EDs reported in this study, except for examinations of the chest, are generally lower than comparable reference dose values published in the literature. On the basis of the results obtained in this study can conclude that use of newer equipment and use of the proper radiological parameter can significantly reduce the absorbed dose. It is recommended that radiological parameter in chest examinations be revised. PMID:26156930
Calculation of the effective dose from natural radioactivity in soil using MCNP code.
Krstic, D; Nikezic, D
2010-01-01
Effective dose delivered by photon emitted from natural radioactivity in soil was calculated in this work. Calculations have been done for the most common natural radionuclides in soil (238)U, (232)Th series and (40)K. A ORNL human phantoms and the Monte Carlo transport code MCNP-4B were employed to calculate the energy deposited in all organs. The effective dose was calculated according to ICRP 74 recommendations. Conversion factors of effective dose per air kerma were determined. Results obtained here were compared with other authors. PMID:20045343
Park, C; Arhjoul, L; Yan, G; Lu, B; Li, J; Liu, C
2014-06-15
Purpose: In current IMRT and VMAT settings, the use of sophisticated dose calculation procedure is inevitable in order to account complex treatment field created by MLCs. As a consequence, independent volumetric dose verification procedure is time consuming which affect the efficiency of clinical workflow. In this study, the authors present an efficient Pencil Beam based dose calculation algorithm that minimizes the computational procedure while preserving the accuracy. Methods: The computational time of Finite Size Pencil Beam (FSPB) algorithm is proportional to the number of infinitesimal identical beamlets that constitute the arbitrary field shape. In AB-FSPB, the dose distribution from each beamlet is mathematically modelled such that the sizes of beamlets to represent arbitrary field shape are no longer needed to be infinitesimal nor identical. In consequence, it is possible to represent arbitrary field shape with combinations of different sized and minimal number of beamlets. Results: On comparing FSPB with AB-FSPB, the complexity of the algorithm has been reduced significantly. For 25 by 25 cm2 squared shaped field, 1 beamlet of 25 by 25 cm2 was sufficient to calculate dose in AB-FSPB, whereas in conventional FSPB, minimum 2500 beamlets of 0.5 by 0.5 cm2 size were needed to calculate dose that was comparable to the Result computed from Treatment Planning System (TPS). The algorithm was also found to be GPU compatible to maximize its computational speed. On calculating 3D dose of IMRT (∼30 control points) and VMAT plan (∼90 control points) with grid size 2.0 mm (200 by 200 by 200), the dose could be computed within 3∼5 and 10∼15 seconds. Conclusion: Authors have developed an efficient Pencil Beam type dose calculation algorithm called AB-FSPB. The fast computation nature along with GPU compatibility has shown performance better than conventional FSPB. This completely enables the implantation of AB-FSPB in the clinical environment for independent
Mohammadyari, Parvin; Faghihi, Reza; Mosleh-Shirazi, Mohammad Amin; Lotfi, Mehrzad; Hematiyan, Mohammad Rahim; Koontz, Craig; Meigooni, Ali S
2015-12-01
Compression is a technique to immobilize the target or improve the dose distribution within the treatment volume during different irradiation techniques such as AccuBoost(®) brachytherapy. However, there is no systematic method for determination of dose distribution for uncompressed tissue after irradiation under compression. In this study, the mechanical behavior of breast tissue between compressed and uncompressed states was investigated. With that, a novel method was developed to determine the dose distribution in uncompressed tissue after irradiation of compressed breast tissue. Dosimetry was performed using two different methods, namely, Monte Carlo simulations using the MCNP5 code and measurements using thermoluminescent dosimeters (TLD). The displacement of the breast elements was simulated using a finite element model and calculated using ABAQUS software. From these results, the 3D dose distribution in uncompressed tissue was determined. The geometry of the model was constructed from magnetic resonance images of six different women volunteers. The mechanical properties were modeled by using the Mooney-Rivlin hyperelastic material model. Experimental dosimetry was performed by placing the TLD chips into the polyvinyl alcohol breast equivalent phantom. The results determined that the nodal displacements, due to the gravitational force and the 60 Newton compression forces (with 43% contraction in the loading direction and 37% expansion in the orthogonal direction) were determined. Finally, a comparison of the experimental data and the simulated data showed agreement within 11.5% ± 5.9%.
Mohammadyari, Parvin; Faghihi, Reza; Mosleh-Shirazi, Mohammad Amin; Lotfi, Mehrzad; Hematiyan, Mohammad Rahim; Koontz, Craig; Meigooni, Ali S
2015-12-01
Compression is a technique to immobilize the target or improve the dose distribution within the treatment volume during different irradiation techniques such as AccuBoost(®) brachytherapy. However, there is no systematic method for determination of dose distribution for uncompressed tissue after irradiation under compression. In this study, the mechanical behavior of breast tissue between compressed and uncompressed states was investigated. With that, a novel method was developed to determine the dose distribution in uncompressed tissue after irradiation of compressed breast tissue. Dosimetry was performed using two different methods, namely, Monte Carlo simulations using the MCNP5 code and measurements using thermoluminescent dosimeters (TLD). The displacement of the breast elements was simulated using a finite element model and calculated using ABAQUS software. From these results, the 3D dose distribution in uncompressed tissue was determined. The geometry of the model was constructed from magnetic resonance images of six different women volunteers. The mechanical properties were modeled by using the Mooney-Rivlin hyperelastic material model. Experimental dosimetry was performed by placing the TLD chips into the polyvinyl alcohol breast equivalent phantom. The results determined that the nodal displacements, due to the gravitational force and the 60 Newton compression forces (with 43% contraction in the loading direction and 37% expansion in the orthogonal direction) were determined. Finally, a comparison of the experimental data and the simulated data showed agreement within 11.5% ± 5.9%. PMID:26572554
NASA Astrophysics Data System (ADS)
Mohammadyari, Parvin; Faghihi, Reza; Mosleh-Shirazi, Mohammad Amin; Lotfi, Mehrzad; Rahim Hematiyan, Mohammad; Koontz, Craig; Meigooni, Ali S.
2015-12-01
Compression is a technique to immobilize the target or improve the dose distribution within the treatment volume during different irradiation techniques such as AccuBoost® brachytherapy. However, there is no systematic method for determination of dose distribution for uncompressed tissue after irradiation under compression. In this study, the mechanical behavior of breast tissue between compressed and uncompressed states was investigated. With that, a novel method was developed to determine the dose distribution in uncompressed tissue after irradiation of compressed breast tissue. Dosimetry was performed using two different methods, namely, Monte Carlo simulations using the MCNP5 code and measurements using thermoluminescent dosimeters (TLD). The displacement of the breast elements was simulated using a finite element model and calculated using ABAQUS software. From these results, the 3D dose distribution in uncompressed tissue was determined. The geometry of the model was constructed from magnetic resonance images of six different women volunteers. The mechanical properties were modeled by using the Mooney-Rivlin hyperelastic material model. Experimental dosimetry was performed by placing the TLD chips into the polyvinyl alcohol breast equivalent phantom. The results determined that the nodal displacements, due to the gravitational force and the 60 Newton compression forces (with 43% contraction in the loading direction and 37% expansion in the orthogonal direction) were determined. Finally, a comparison of the experimental data and the simulated data showed agreement within 11.5% ± 5.9%.
Zhou Jun; Sebastian, Evelyn; Mangona, Victor; Yan Di
2013-02-15
Purpose: In order to increase the accuracy and speed of catheter reconstruction in a high-dose-rate (HDR) prostate implant procedure, an automatic tracking system has been developed using an electromagnetic (EM) device (trakSTAR, Ascension Technology, VT). The performance of the system, including the accuracy and noise level with various tracking parameters and conditions, were investigated. Methods: A direct current (dc) EM transmitter (midrange model) and a sensor with diameter of 1.3 mm (Model 130) were used in the trakSTAR system for tracking catheter position during HDR prostate brachytherapy. Localization accuracy was assessed under both static and dynamic analyses conditions. For the static analysis, a calibration phantom was used to investigate error dependency on operating room (OR) table height (bottom vs midposition vs top), sensor position (distal tip of catheter vs connector end of catheter), direction [left-right (LR) vs anterior-posterior (AP) vs superior-inferior (SI)], sampling frequency (40 vs 80 vs 120 Hz), and interference from OR equipment (present vs absent). The mean and standard deviation of the localization offset in each direction and the corresponding error vectors were calculated. For dynamic analysis, the paths of five straight catheters were tracked to study the effects of directions, sampling frequency, and interference of EM field. Statistical analysis was conducted to compare the results in different configurations. Results: When interference was present in the static analysis, the error vectors were significantly higher at the top table position (3.3 {+-} 1.3 vs 1.8 {+-} 0.9 mm at bottom and 1.7 {+-} 1.0 mm at middle, p < 0.001), at catheter end position (3.1 {+-} 1.1 vs 1.4 {+-} 0.7 mm at the tip position, p < 0.001), and at 40 Hz sampling frequency (2.6 {+-} 1.1 vs 2.4 {+-} 1.5 mm at 80 Hz and 1.8 {+-} 1.1 at 160 Hz, p < 0.001). So did the mean offset errors in the LR direction (-1.7 {+-} 1.4 vs 0.4 {+-} 0.5 mm in AP and 0
NASA Technical Reports Server (NTRS)
Wilson, J. W.; Chun, S. Y.; Reginatto, M.; Hajnal, F.
1995-01-01
The Green's function for the transport of ions of high charge and energy is utilized with a nuclear fragmentation database to evaluate dose, dose equivalent, and RBE for C3H10T1/2 cell survival and neo-plastic transformation as function of depth in soft tissue. Such evaluations are useful to estimates of biological risk for high altitude aircraft, space operations, accelerator operations, and biomedical application.
NASA Technical Reports Server (NTRS)
Wilson, J. W.; Reginatto, M.; Hajnal, F.; Chun, S. Y.
1995-01-01
The Green's function for the transport of ions of high charge and energy is utilized with a nuclear fragmentation database to evaluate dose, dose equivalent, and RBE for C3H1OT1/2 cell survival and neoplastic transformation as a function of depth in soft tissue. Such evaluations are useful to estimates of biological risk for high altitude aircraft, space operations, accelerator operations, and biomedical applications.
[Comparison of dose calculation algorithms in stereotactic radiation therapy in lung].
Tomiyama, Yuki; Araki, Fujio; Kanetake, Nagisa; Shimohigashi, Yoshinobu; Tominaga, Hirofumi; Sakata, Jyunichi; Oono, Takeshi; Kouno, Tomohiro; Hioki, Kazunari
2013-06-01
Dose calculation algorithms in radiation treatment planning systems (RTPSs) play a crucial role in stereotactic body radiation therapy (SBRT) in the lung with heterogeneous media. This study investigated the performance and accuracy of dose calculation for three algorithms: analytical anisotropic algorithm (AAA), pencil beam convolution (PBC) and Acuros XB (AXB) in Eclipse (Varian Medical Systems), by comparison against the Voxel Monte Carlo algorithm (VMC) in iPlan (BrainLab). The dose calculations were performed with clinical lung treatments under identical planning conditions, and the dose distributions and the dose volume histogram (DVH) were compared among algorithms. AAA underestimated the dose in the planning target volume (PTV) compared to VMC and AXB in most clinical plans. In contrast, PBC overestimated the PTV dose. AXB tended to slightly overestimate the PTV dose compared to VMC but the discrepancy was within 3%. The discrepancy in the PTV dose between VMC and AXB appears to be due to differences in physical material assignments, material voxelization methods, and an energy cut-off for electron interactions. The dose distributions in lung treatments varied significantly according to the calculation accuracy of the algorithms. VMC and AXB are better algorithms than AAA for SBRT. PMID:23782779
Bourguignon, Laurent; Goutelle, Sylvain; Gérard, Cécile; Guillermet, Anne; Burdin de Saint Martin, Julie; Maire, Pascal; Ducher, Michel
2009-01-01
The use of amikacin is difficult because of its toxicity and its pharmacokinetic variability. This variability is almost ignored in adult standard dosage regimens since only the weight is used in the dose calculation. Our objective is to test if the pharmacokinetic of amikacin can be regarded as homogenous, and if the method for calculating the dose according to patients' weight is appropriate. From a cohort of 580 patients, five groups of patients were created by statistical data partitioning. A population pharmacokinetic analysis was performed in each group. The adult population is not homogeneous in term of pharmacokinetics. The doses required to achieve a maximum concentration of 60 mg/L are strongly different (585 to 1507 mg) between groups. The exclusive use of the weight to calculate the dose of amikacine appears inappropriate for 80% of the patients, showing the limits of the formulae for calculating doses of aminoglycosides.
Lopatiuk-Tirpak, O.; Langen, K. M.; Meeks, S. L.; Kupelian, P. A.; Zeidan, O. A.; Maryanski, M. J.
2008-09-15
The performance of a next-generation optical computed tomography scanner (OCTOPUS-5X) is characterized in the context of three-dimensional gel dosimetry. Large-volume (2.2 L), muscle-equivalent, radiation-sensitive polymer gel dosimeters (BANG-3) were used. Improvements in scanner design leading to shorter acquisition times are discussed. The spatial resolution, detectable absorbance range, and reproducibility are assessed. An efficient method for calibrating gel dosimeters using the depth-dose relationship is applied, with photon- and electron-based deliveries yielding equivalent results. A procedure involving a preirradiation scan was used to reduce the edge artifacts in reconstructed images, thereby increasing the useful cross-sectional area of the dosimeter by nearly a factor of 2. Dose distributions derived from optical density measurements using the calibration coefficient show good agreement with the treatment planning system simulations and radiographic film measurements. The feasibility of use for motion (four-dimensional) dosimetry is demonstrated on an example comparing dose distributions from static and dynamic delivery of a single-field photon plan. The capability to visualize three-dimensional dose distributions is also illustrated.
CALCULATION OF GAMMA SPECTRA IN A PLASTIC SCINTILLATOR FOR ENERGY CALIBRATIONAND DOSE COMPUTATION.
Kim, Chankyu; Yoo, Hyunjun; Kim, Yewon; Moon, Myungkook; Kim, Jong Yul; Kang, Dong Uk; Lee, Daehee; Kim, Myung Soo; Cho, Minsik; Lee, Eunjoong; Cho, Gyuseong
2016-09-01
Plastic scintillation detectors have practical advantages in the field of dosimetry. Energy calibration of measured gamma spectra is important for dose computation, but it is not simple in the plastic scintillators because of their different characteristics and a finite resolution. In this study, the gamma spectra in a polystyrene scintillator were calculated for the energy calibration and dose computation. Based on the relationship between the energy resolution and estimated energy broadening effect in the calculated spectra, the gamma spectra were simply calculated without many iterations. The calculated spectra were in agreement with the calculation by an existing method and measurements. PMID:27127208
NASA Astrophysics Data System (ADS)
de Paiva, Eduardo
Concave beta sources of 106Ru/106Rh are used in radiotherapy to treat ophthalmic tumors. However, a problem that arises is the difficult determination of absorbed dose distributions around such sources mainly because of the small range of the electrons and the steep dose gradients. In this sense, numerical methods have been developed to calculate the dose distributions around the beta applicators. In this work a simple code in Fortran language is developed to estimate the dose rates along the central axis of 106Ru/106Rh curved plaques by numerical integration of the beta point source function and results are compared with other calculated data.
Moderated 252Cf neutron energy spectra in brain tissue and calculated boron neutron capture dose.
Rivard, Mark J; Zamenhof, Robert G
2004-11-01
While there is significant clinical experience using both low- and high-dose (252)Cf brachytherapy, combination therapy using (10)B for neutron capture therapy-enhanced (252)Cf brachytherapy has not been performed. Monte Carlo calculations were performed in a brain phantom (ICRU 44 brain tissue) to evaluate the dose enhancement predicted for a range of (10)B concentrations over a range of distances from a clinical (252)Cf source. These results were compared to experimental measurements and calculations published in the literature. For (10)B concentrations dose enhancement was small in comparison to the (252)Cf fast neutron dose.
ERIC Educational Resources Information Center
Hastings, S. K.
2002-01-01
Discusses 3 D imaging as it relates to digital representations in virtual library collections. Highlights include X-ray computed tomography (X-ray CT); the National Science Foundation (NSF) Digital Library Initiatives; output peripherals; image retrieval systems, including metadata; and applications of 3 D imaging for libraries and museums. (LRW)
Ikenberry, T.A.; Napier, B.A.
1992-12-01
A series of scoping calculations have been undertaken to evaluate The absolute and relative contribution of different exposure pathways to doses that may have been received by individuals living in the vicinity of the Hanford site. This scoping calculation (Calculation 001) examined the contributions of the various exposure pathways associated with environmental transport and accumulation of iodine-131 in the pasture-cow-milk pathway. Addressed in this calculation were the contributions to thyroid dose of infants and adult from (1) the ingestion by dairy cattle of various feedstuffs (pasturage, silage, alfalfa hay, and grass hay) in four different feeding regimes; (2) ingestion of soil by dairy cattle; (3) ingestion of stared feed on which airborne iodine-131 had been deposited; and (4) inhalation of airborne iodine-131 by dairy cows.
(Considerations of beta and electron transport in internal dose calculations): (Progress report)
Poston, J.W.
1989-01-01
This task involved use of the code INDOSE-EGS for calculation of S-values for radionuclides of importance in nuclear medicine. This task was proposed to proceed in a logical fashion as outlined below: identification of radionuclides for which more refined dose estimates are required; identification of the target and source combinations for which the previous assumption is clearly invalid; production of a base of data for monoenergetic radiations with sufficient accuracy to be used in dose calculations; calculation of revised dose estimates, i.e., S-values. The extension of this code to include head and neck models, gall bladder models, and kidney models are discussed. 2 refs.
NASA Astrophysics Data System (ADS)
Weihs, P.; Wagner, J. E.; Schreier, S. F.; Rieder, H. E.; Angelini, F.; Blumthaler, M.; Fitzka, M.; Gobbi, G. P.; Kift, R.; Kreuter, A.; Simic, S.; Webb, A. R.
2012-03-01
The aim of this study is to investigate the influence of the spatial resolution of a digital elevation map (DEM) on the three-dimensional (3-D) radiative transfer performance for both spectral ultraviolet (UV) irradiance and actinic flux at 305 nm. Model simulations were performed for clear sky conditions for three case studies: the first and second one using three sites in the Innsbruck area and the third one using three sites at the Sonnblick observatory and surrounding area. It was found that the DEM resolution may change the altitude at some locations by up to 500 m, resulting in changes in the sky obscured by the horizon of up to 15%. The geographical distribution of UV irradiance and actinic flux shows that with larger pixel size, uncertainties in UV irradiance and actinic flux determination of up to 100% are possible. These large changes in incident irradiance and actinic flux with changing pixel size are strongly connected to shading effects. The effect of the DEM pixel size on irradiance and actinic flux was studied at the six locations, and it was found that significant increases in irradiance and actinic flux with increasing DEM pixel size occurred at one valley location at high solar zenith angles in the Innsbruck area as well as for one steep valley location in the Sonnblick area. This increase in irradiance and actinic flux with increasing DEM resolution is most likely to be connected to shading effects affecting the reflections from the surroundings.
NASA Astrophysics Data System (ADS)
Weihs, P.; Wagner, J. E.; Schreier, S. F.; Rieder, H. E.; Angelini, F.; Blumthaler, M.; Fitzka, M.; Gobbi, G. P.; Kift, R.; Kreuter, A.; Simic, S.; Webb, A. R.
2011-10-01
The aim of this study was to investigate the influence of the spatial resolution of a digital elevation map (DEM) on the three-dimensional (3-D) radiative transfer performance for both spectral ultraviolet (UV) irradiance and actinic flux at 305 nm. Model simulations were performed for clear sky conditions for three case studies: the first and second one using three sites in the Innsbruck area and the third one using three sites at the Sonnblick Observatory and surrounding area. It was found that DEM resolution may change the altitude at some locations by up to 500 m, resulting in changes in the sky obscured by the horizon of up to 15%. The geographical distribution of UV irradiance and actinic flux shows that with larger pixel size, uncertainties in UV irradiance and actinic flux determination of up to 100% are possible. These large changes in incident irradiance and actinic flux with changing pixel size are strongly connected to shading effects. The effect of DEM pixel size on irradiance and actinic flux was studied at the six locations, and it was found that significant increases in irradiance and actinic flux with increasing DEM pixel size occurred at one valley location at high solar zenith angles in the Innsbruck area as well as for one steep valley location in the Sonnblick area. This increase in irradiance and actinic flux with increasing DEM resolution is most likely to be connected to shading effects affecting the reflections from the surroundings.
Vavassori, Vittorio; Fiorino, Claudio . E-mail: fiorino.claudio@hsr.it; Rancati, Tiziana; Magli, Alessandro; Fellin, Gianni; Baccolini, Michela; Bianchi, Carla; Cagna, Emanuela; Mauro, Flora A.; Monti, Angelo F.; Munoz, Fernando; Stasi, Michele; Franzone, Paola; Valdagni, Riccardo
2007-04-01
Purpose: To find predictors for rectal and intestinal acute toxicity in patients with prostate cancer treated with {>=}70 Gy conformal radiotherapy. Methods and Materials: Between July 2002 and March 2004, 1,132 patients were entered into a cooperative study (AIROPROS01-02). Toxicity was scored using the Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer scale and by considering the changes (before and after treatment) of the scores of a self-administered questionnaire on rectal/intestinal toxicity. The correlation with a number of parameters was assessed by univariate and multivariate analyses. Concerning the questionnaire, only moderate/severe complications were considered. Results: Of 1,132 patients, 1,123 were evaluable. Of these patients, 375, 265, and 28 had Grade 1, 2, and 3 Radiation Therapy Oncology Group/European Organization for Research and Treatment of Cancer toxicity, respectively. The mean rectal dose was the most predictive parameter (p = 0.0004; odds ratio, 1.035) for Grade 2 or worse toxicity, and the use of anticoagulants/antiaggregants (p 0.02; odds ratio, 0.63) and hormonal therapy (p = 0.04, odds ratio, 0.65) were protective. The questionnaire-based scoring revealed that a greater mean rectal dose was associated with a greater risk of bleeding; larger irradiated volumes were associated with frequency, tenesmus, incontinence, and bleeding; hormonal therapy was protective against frequency and tenesmus; hemorrhoids were associated with a greater risk of tenesmus and bleeding; and diabetes associated highly with diarrhea. Conclusion: The mean rectal dose correlated with acute rectal/intestinal toxicity in three-dimensional conformal radiotherapy for prostate cancer, and hormonal therapy and the use of anticoagulants/antiaggregants were protective. According to the moderate/severe injury scores on the self-assessed questionnaire, several clinical and dose-volume parameters were independently predictive for
Independent calculation of dose from a helical TomoTherapy unit.
Gibbons, John P; Smith, Koren; Cheek, Dennis; Rosen, Isaac
2009-02-05
A new calculation algorithm has been developed for independently verifying doses calculated by the TomoTherapy Hi.Art treatment planning system (TPS). The algorithm is designed to confirm the dose to a point in a high dose, low dose-gradient region. Patient data used by the algorithm include the radiological depth to the point for each projection angle and the treatment sinogram file controlling the leaf opening time for each projection. The algorithm uses common dosimetric functions [tissue phantom ratio (TPR) and output factor (Scp)] for the central axis combined with lateral and longitudinal beam profile data to quantify the off-axis dose dependence. Machine data for the dosimetric functions were measured on the Hi.Art machine and simulated using the TPS. Point dose calculations were made for several test phantoms and for 97 patient treatment plans using the simulated machine data. Comparisons with TPS-predicted point doses for the phantom treatment plans demonstrated agreement within 2% for both on-axis and off-axis planning target volumes (PTVs). Comparisons with TPS-predicted point doses for the patient treatment plans also showed good agreement. For calculations at sites other than lung and superficial PTVs, agreement between the calculations was within 2% for 94% of the patient calculations (64 of 68). Calculations within lung and superficial PTVs overestimated the dose by an average of 3.1% (sigma=2.4%) and 3.2% (sigma=2.2%), respectively. Systematic errors within lung are probably due to the weakness of the algorithm in correcting for missing tissue and/or tissue density heterogeneities. Errors encountered within superficial PTVs probably result from the algorithm overestimating the scatter dose within the patient. Our results demonstrate that for the majority of cases, the algorithm could be used without further refinement to independently verify patient treatment plans.
NASA Astrophysics Data System (ADS)
Lee, M. S.; Kim, H. J.; Cho, H. S.; Hong, D. K.; Je, U. K.; Oh, J. E.; Park, Y. O.; Lee, S. H.; Cho, H. M.; Choi, S. I.; Koo, Y. S.
2013-09-01
The most popular reconstruction algorithm for cone-beam computed tomography (CBCT) is based on the computationally-inexpensive filtered-backprojection (FBP) method. However, that method usually requires dense projections over the Nyquist samplings, which imposes severe restrictions on the imaging doses. Moreover, the algorithm tends to produce cone-beam artifacts as the cone angle is increased. Several variants of the FBP-based algorithm have been developed to overcome these difficulties, but problems with the cone-beam reconstruction still remain. In this study, we considered a compressed-sensing (CS)-based reconstruction algorithm for low-dose, high-quality dental CBCT images that exploited the sparsity of images with substantially high accuracy. We implemented the algorithm and performed systematic simulation works to investigate the imaging characteristics. CBCT images of high quality were successfully reconstructed by using the built-in CS-based algorithm, and the image qualities were evaluated quantitatively in terms of the universal-quality index (UQI) and the slice-profile quality index (SPQI).We expect the reconstruction algorithm developed in the work to be applicable to current dental CBCT systems, to reduce imaging doses, and to improve the image quality further.
A centralized dose calculation system for radiation therapy.
Xiao, Y; Galvin, J
2000-05-01
Centralization of treatment planning in a radiation therapy department is a realistic strategy to achieve an integrated and quality-controlled planning system, especially for institutions with numerous affiliations. The rapid evolution of computer hardware and software technology makes this a distinct possibility. However, the procedure of three-dimensional treatment planning involves a number of steps, such as: (1) input of patient computed tomography (CT) images and contour information; (2) interactions with local devices such as a film digitizer; and (3) output of beam information to be integrated with the record and verify the system. A full-fledged realization of the web-based centralized three-dimensional treatment planning system will require an extensive commercial development effort. We have developed and incorporated a web-based Timer/Monitor Unit (MU) program as a first step towards the full implementation of a centralized treatment planning system. The software application was developed in JAVA language. It uses the internet server and client technology. With one server that can handle multiple threads, it is a simple process to access the application anywhere on the network with an internet browser. Both the essential data needed for the calculation and the results are stored on the server, which centralizes the maintenance of the software and the storage of patient information.
NASA Astrophysics Data System (ADS)
Burmeister, Soenke; Berger, Thomas; Reitz, Guenther; Boehme, Matthias; Haumann, Lutz; Labrenz, Johannes
Besides the effects of the microgravity environment, and the psychological and psychosocial problems encountered in confined spaces, radiation is the main health detriment for long duration human space missions. The radiation environment encountered in space differs in nature from that on earth, consisting mostly of high energetic ions from protons up to iron, resulting in radiation levels far exceeding the ones encountered on earth for occupational radiation workers. Accurate knowledge of the physical characteristics of the space radiation field in dependence on the solar activity, the orbital parameters and the different shielding configurations of the International Space Station ISS is therefore needed. For the investigation of the spatial and temporal distribution of the radiation field inside the European COLUMBUS module the experiment DOSIS (Dose Distribution Inside the ISS) under the lead of DLR has been launched on July 15 (th) 2009 with STS-127 to the ISS. The experimental package was transferred from the Space Shuttle into COLUMBUS on July 18 (th) . It consists of a combination of passive detector packages (PDP) distributed at 11 locations inside the European Columbus Laboratory and two active radiation detectors (Dosimetry Telescopes = DOSTELs) with a DDPU (DOSTEL Data and Power Unit) in a Nomex pouch (DOSIS MAIN BOX) mounted at a fixed location beneath the European Physiology Module rack (EPM) inside COLUMBUS. The active components of the DOSIS experiment were operational from July 18 (th) 2009 to June 16 (th) 2011. After refurbishment the hardware has been reactivated on May 15 (th) 2012 as active part of the DOSIS 3D experiment and provides continuous data since this activation. The presentation will focus on the latest results from the two DOSTEL instruments as absorbed dose, dose equivalent and the related LET spectra gathered within the DOSIS (2009 - 2011) and DOSIS 3D (2012 - 2014) experiment. The CAU contributions to DOSIS and DOSIS 3D are
Yan Xiangsheng; Poon, Emily; Reniers, Brigitte; Vuong, Te; Verhaegen, Frank
2008-11-15
Colorectal cancer patients are treated at our hospital with {sup 192}Ir high dose rate (HDR) brachytherapy using an applicator that allows the introduction of a lead or tungsten shielding rod to reduce the dose to healthy tissue. The clinical dose planning calculations are, however, currently performed without taking the shielding into account. To study the dose distributions in shielded cases, three techniques were employed. The first technique was to adapt a shielding algorithm which is part of the Nucletron PLATO HDR treatment planning system. The isodose pattern exhibited unexpected features but was found to be a reasonable approximation. The second technique employed a ray tracing algorithm that assigns a constant dose ratio with/without shielding behind the shielding along a radial line originating from the source. The dose calculation results were similar to the results from the first technique but with improved accuracy. The third and most accurate technique used a dose-matrix-superposition algorithm, based on Monte Carlo calculations. The results from the latter technique showed quantitatively that the dose to healthy tissue is reduced significantly in the presence of shielding. However, it was also found that the dose to the tumor may be affected by the presence of shielding; for about a quarter of the patients treated the volume covered by the 100% isodose lines was reduced by more than 5%, leading to potential tumor cold spots. Use of any of the three shielding algorithms results in improved dose estimates to healthy tissue and the tumor.
Validation of Monte Carlo calculated surface doses for megavoltage photon beams.
Abdel-Rahman, Wamied; Seuntjens, Jan P; Verhaegen, Frank; Deblois, François; Podgorsak, Ervin B
2005-01-01
Recent work has shown that there is significant uncertainty in measuring build-up doses in mega-voltage photon beams especially at high energies. In this present investigation we used a phantom-embedded extrapolation chamber (PEEC) made of Solid Water to validate Monte Carlo (MC)-calculated doses in the dose build-up region for 6 and 18 MV x-ray beams. The study showed that the percentage depth ionizations (PDIs) obtained from measurements are higher than the percentage depth doses (PDDs) obtained with Monte Carlo techniques. To validate the MC-calculated PDDs, the design of the PEEC was incorporated into the simulations. While the MC-calculated and measured PDIs in the dose build-up region agree with one another for the 6 MV beam, a non-negligible difference is observed for the 18 MV x-ray beam. A number of experiments and theoretical studies of various possible effects that could be the source of this discrepancy were performed. The contribution of contaminating neutrons and protons to the build-up dose region in the 18 MV x-ray beam is negligible. Moreover, the MC calculations using the XCOM photon cross-section database and the NIST bremsstrahlung differential cross section do not explain the discrepancy between the MC calculations and measurement in the dose build-up region for the 18 MV. A simple incorporation of triplet production events into the MC dose calculation increases the calculated doses in the build-up region but does not fully account for the discrepancy between measurement and calculations for the 18 MV x-ray beam. PMID:15719980
3D Model of Surfactant Replacement Therapy
NASA Astrophysics Data System (ADS)
Grotberg, James; Tai, Cheng-Feng; Filoche, Marcel
2015-11-01
Surfactant Replacement Therapy (SRT) involves instillation of a liquid-surfactant mixture directly into the lung airway tree. Though successful in neonatal applications, its use in adults had early success followed by failure. We present the first mathematical model of 3D SRT where a liquid plug propagates through the tree from forced inspiration. In two separate modeling steps, the plug first deposits a coating film on the airway wall which subtracts from its volume, a ``coating cost''. Then the plug splits unevenly at the airway bifurcation due to gravity. The steps are repeated until a plug ruptures or reaches the tree endpoint alveoli/acinus. The model generates 3D images of the resulting acinar distribution and calculates two global indexes, efficiency and homogeneity. Simulating published literature, the earlier successful adult SRT studies show comparatively good index values, while the later failed studies do not. Those unsuccessful studies used smaller dose volumes with higher concentration mixtures, apparently assuming a well mixed compartment. The model shows that adult lungs are not well mixed in SRT due to the coating cost and gravity effects. Returning to the higher dose volume protocols could save many thousands of lives annually in the US. Supported by NIH Grants HL85156, HL84370 and Agence Nationale de la Recherche, ANR no. 2010-BLAN-1119-05.
Sub-second pencil beam dose calculation on GPU for adaptive proton therapy.
da Silva, Joakim; Ansorge, Richard; Jena, Rajesh
2015-06-21
Although proton therapy delivered using scanned pencil beams has the potential to produce better dose conformity than conventional radiotherapy, the created dose distributions are more sensitive to anatomical changes and patient motion. Therefore, the introduction of adaptive treatment techniques where the dose can be monitored as it is being delivered is highly desirable. We present a GPU-based dose calculation engine relying on the widely used pencil beam algorithm, developed for on-line dose calculation. The calculation engine was implemented from scratch, with each step of the algorithm parallelized and adapted to run efficiently on the GPU architecture. To ensure fast calculation, it employs several application-specific modifications and simplifications, and a fast scatter-based implementation of the computationally expensive kernel superposition step. The calculation time for a skull base treatment plan using two beam directions was 0.22 s on an Nvidia Tesla K40 GPU, whereas a test case of a cubic target in water from the literature took 0.14 s to calculate. The accuracy of the patient dose distributions was assessed by calculating the γ-index with respect to a gold standard Monte Carlo simulation. The passing rates were 99.2% and 96.7%, respectively, for the 3%/3 mm and 2%/2 mm criteria, matching those produced by a clinical treatment planning system.
Sub-second pencil beam dose calculation on GPU for adaptive proton therapy
NASA Astrophysics Data System (ADS)
da Silva, Joakim; Ansorge, Richard; Jena, Rajesh
2015-06-01
Although proton therapy delivered using scanned pencil beams has the potential to produce better dose conformity than conventional radiotherapy, the created dose distributions are more sensitive to anatomical changes and patient motion. Therefore, the introduction of adaptive treatment techniques where the dose can be monitored as it is being delivered is highly desirable. We present a GPU-based dose calculation engine relying on the widely used pencil beam algorithm, developed for on-line dose calculation. The calculation engine was implemented from scratch, with each step of the algorithm parallelized and adapted to run efficiently on the GPU architecture. To ensure fast calculation, it employs several application-specific modifications and simplifications, and a fast scatter-based implementation of the computationally expensive kernel superposition step. The calculation time for a skull base treatment plan using two beam directions was 0.22 s on an Nvidia Tesla K40 GPU, whereas a test case of a cubic target in water from the literature took 0.14 s to calculate. The accuracy of the patient dose distributions was assessed by calculating the γ-index with respect to a gold standard Monte Carlo simulation. The passing rates were 99.2% and 96.7%, respectively, for the 3%/3 mm and 2%/2 mm criteria, matching those produced by a clinical treatment planning system.
A system for remote dosimetry audit of 3D-CRT, IMRT and VMAT based on lithium formate dosimetry.
Adolfsson, Emelie; Gustafsson, Håkan; Lund, Eva; Alm Carlsson, Gudrun; Olsson, Sara; Carlsson Tedgren, Sa
2014-11-01
The aim of this work was to develop and test a remote end-to-end audit system using lithium formate EPR dosimeters. Four clinics were included in a pilot study, absorbed doses determined in the PTV agreed with TPS calculated doses within ±5% for 3D-CRT and ±7% (k=1) for IMRT/VMAT dose plans.
Influence of polarization and a source model for dose calculation in MRT
Bartzsch, Stefan Oelfke, Uwe; Lerch, Michael; Petasecca, Marco; Bräuer-Krisch, Elke
2014-04-15
Purpose: Microbeam Radiation Therapy (MRT), an alternative preclinical treatment strategy using spatially modulated synchrotron radiation on a micrometer scale, has the great potential to cure malignant tumors (e.g., brain tumors) while having low side effects on normal tissue. Dose measurement and calculation in MRT is challenging because of the spatial accuracy required and the arising high dose differences. Dose calculation with Monte Carlo simulations is time consuming and their accuracy is still a matter of debate. In particular, the influence of photon polarization has been discussed in the literature. Moreover, it is controversial whether a complete knowledge of phase space trajectories, i.e., the simulation of the machine from the wiggler to the collimator, is necessary in order to accurately calculate the dose. Methods: With Monte Carlo simulations in the Geant4 toolkit, the authors investigate the influence of polarization on the dose distribution and the therapeutically important peak to valley dose ratios (PVDRs). Furthermore, the authors analyze in detail phase space information provided byMartínez-Rovira et al. [“Development and commissioning of a Monte Carlo photon model for the forthcoming clinical trials in microbeam radiation therapy,” Med. Phys. 39(1), 119–131 (2012)] and examine its influence on peak and valley doses. A simple source model is developed using parallel beams and its applicability is shown in a semiadjoint Monte Carlo simulation. Results are compared to measurements and previously published data. Results: Polarization has a significant influence on the scattered dose outside the microbeam field. In the radiation field, however, dose and PVDRs deduced from calculations without polarization and with polarization differ by less than 3%. The authors show that the key consequences from the phase space information for dose calculations are inhomogeneous primary photon flux, partial absorption due to inclined beam incidence outside
Maxim, Voichita; Lojacono, Xavier; Hilaire, Estelle; Krimmer, Jochen; Testa, Etienne; Dauvergne, Denis; Magnin, Isabelle; Prost, Rémy
2016-01-01
This paper addresses the problem of evaluating the system matrix and the sensitivity for iterative reconstruction in Compton camera imaging. Proposed models and numerical calculation strategies are compared through the influence they have on the three-dimensional reconstructed images. The study attempts to address four questions. First, it proposes an analytic model for the system matrix. Second, it suggests a method for its numerical validation with Monte Carlo simulated data. Third, it compares analytical models of the sensitivity factors with Monte Carlo simulated values. Finally, it shows how the system matrix and the sensitivity calculation strategies influence the quality of the reconstructed images.
1982-06-15
WRAITH calculates the atmospheric transport of radioactive material to each of a number of downwind receptor points and the external and internal doses to a reference man at each of the receptor points.
Technical basis for beta skin dose calculations at the Y-12 Plant
Thomas, J.M.; Bogard, R.S.
1994-03-01
This report describes the methods for determining shallow dose equivalent to workers at the Oak Ridge Y-12 Plant from skin contamination detected by survey instrumentation. Included is a discussion of how the computer code VARSKIN is used to calculate beta skin dose and how the code input parameters affect skin dose calculation results. A summary of Y-12 Plant specific assumptions used in performing VARSKIN calculations is presented. Derivations of contamination levels that trigger the need for skin dose assessment are given for both enriched and depleted uranium with the use of Y-12 Plant site-specific survey instruments. Department of Energy recording requirements for nonuniform exposure of the skin are illustrated with sample calculations.