A beta-emitting glass seed was proposed for the brachytherapy treatment of prostate cancer. Criteria for seed design were derived and several beta-emitting nuclides were examined for suitability. 142Pr was selected as the isotope of choice. Seeds 0.08 cm in diameter and 0.9 cm long were manufactured for testing. The seeds were activated in the Texas A&M University research reactor. The activity produced was as expected when considering the meta-stable state and epi-thermal neutron flux. The MCNP5 Monte Carlo code was used to calculate the quantitative dosimetric parameters suggested in the American Association of Physicists in Medicine (AAPM) TG-43/60. The Monte Carlo calculation results were compared with those from a dose point kernel code. The dose profiles agree well with each other. The gamma dose of 142Pr was evaluated. The gamma dose is 0.3 Gy at 1.0 cm with initial activity of 5.95 mCi and is insignificant to other organs. Measurements were performed to assess the 2-dimensional axial dose distributions using Gafchromic radiochromic film. The radiochromic film was calibrated using an X-ray machine calibrated against a National Institute of Standards and Technology (NIST) traceable ion chamber. A calibration curve was derived using a least squares fit of a second order polynomial. The measured dose distribution agrees well with results from the Monte Carlo simulation. The dose was 130.8 Gy at 6 mm from the seed center with initial activity of 5.95 mCi. AAPM TG-43/60 parameters were determined. The reference dose rate for 2 mm and 6 mm were 0.67 and 0.02 cGy/s/mCi, respectively. The geometry function, radial dose function and anisotropy function were generated.

The goal of this thesis was to explore the effects of dose resolution, respiratory variation and dose calculation method on dose accuracy. To achieve this, two models of lung were created. The first model, called TISSUE, approximated the connective alveolar tissues of the lung. The second model, called BRANCH, approximated the lungs bronchial, arterial and venous branching networks. Both models were varied to represent the full inhalation, full exhalation and midbreath phases of the respiration cycle.<p> To explore the effects of dose resolution and respiratory variation on dose accuracy, each model was converted into a CT dataset and imported into a Monte Carlo simulation. The resulting dose distributions were compared and contrasted against dose distributions from Monte Carlo simulations which included the explicit model geometries. It was concluded that, regardless of respiratory phase, the exclusion of the connective tissue structures in the CT representation did not significantly effect the accuracy of dose calculations. However, the exclusion of the BRANCH structures resulted in dose underestimations as high as 14\% local to the branching structures. As lung density decreased, the overall dose accuracy marginally decreased.<p> To explore the effects of dose calculation method on dose accuracy, CT representations of the lung models were imported into the Pinnacle$^3$ treatment planning system. Dose distributions were calculated using the collapsed cone convolution method and compared to those derived using the Monte Carlo method. For both lung models, it was concluded that the accuracy of the collapsed cone algorithm decreased with decreasing density. At full inhalation lung density, the collapsed cone algorithm underestimated dose by as much as 15\%. Also, the accuracy of the CCC method decreased with decreasing field size.<p> Further work is needed to determine the source of the discrepancy.

The goal of this thesis was to explore the effects of dose resolution, respiratory variation and dose calculation method on dose accuracy. To achieve this, two models of lung were created. The first model, called TISSUE, approximated the connective alveolar tissues of the lung. The second model, called BRANCH, approximated the lungs bronchial, arterial and venous branching networks. Both models were varied to represent the full inhalation, full exhalation and midbreath phases of the respiration cycle.<p> To explore the effects of dose resolution and respiratory variation on dose accuracy, each model was converted into a CT dataset and imported into a Monte Carlo simulation. The resulting dose distributions were compared and contrasted against dose distributions from Monte Carlo simulations which included the explicit model geometries. It was concluded that, regardless of respiratory phase, the exclusion of the connective tissue structures in the CT representation did not significantly effect the accuracy of dose calculations. However, the exclusion of the BRANCH structures resulted in dose underestimations as high as 14\% local to the branching structures. As lung density decreased, the overall dose accuracy marginally decreased.<p> To explore the effects of dose calculation method on dose accuracy, CT representations of the lung models were imported into the Pinnacle$^3$ treatment planning system. Dose distributions were calculated using the collapsed cone convolution method and compared to those derived using the Monte Carlo method. For both lung models, it was concluded that the accuracy of the collapsed cone algorithm decreased with decreasing density. At full inhalation lung density, the collapsed cone algorithm underestimated dose by as much as 15\%. Also, the accuracy of the CCC method decreased with decreasing field size.<p> Further work is needed to determine the source of the discrepancy.

Six radiation dosimetry and medical physics problems were analyzed using a beta version of MCNP 5 as part of an international intercomparison of radiation dosimetry computer codes, sponsored by the European Commission committee on the quality assurance of computational tools in radiation dosimetry. Results have been submitted to the committee, which will perform the inter-code comparison and publish the results independently. A comparison of the beta version of MCNP 5 with MCNP 4C2 is made, as well as a comparison of the new Doppler broadening feature. Comparisons are also made between the *F8 and F6 tallies, neutron tally results with and without the use of the S(a,b) cross sections, and analytically derived peak positions with pulse height distributions of a Ge detector obtained using the beta version of MCNP 5. The following problems from the study were examined: Problem 1 was modeled to determine the near-field angular anisotropy and dose distribution from a high dose rate 192Ir brachytherapy source in a surrounding spherical water phantom. Problem 2 was modeled to find radial and axial dose in an artery wall from an intravascular brachytherapy 32P source. Problem 4 was modeled to investigate the response of a four-element TLD-albedo personal dosimeter from neutrons and/or photons. Significant differences in neutron response with S(a,b) cross sections compared to results without these cross sections were found. Problem 5 was modeled to obtain air kerma backscatter profiles for 150 and 200 kVp X-rays upon a water phantom. Air kerma backscatter profiles were determined along the apothem and diagonal of the front face of the phantom. A comparison of experimental results is also made. Problem 6 was modeled to determine indirect spectral and energy fluences upon two neutron detectors within a calibration bunker. The largest indirect contribution was found to come from low energy neutrons with an average angle of 47o where 0o is a plane parallel to the floor. Problem 7 was modeled to obtain pulse height distributions for a germanium detector. Comparison of analytically derived peaks with peak positions in the spectra are made. An examination of the Doppler broadening feature is also included.

A beta-emitting glass seed was proposed for the brachytherapy treatment of prostate cancer. Criteria for seed design were derived and several beta-emitting nuclides were examined for suitability. 142Pr was selected as the isotope of choice. Seeds 0.08 cm in diameter and 0.9 cm long were manufactured for testing. The seeds were activated in the Texas A&M University research reactor. The activity produced was as expected when considering the meta-stable state and epi-thermal neutron flux. The MCNP5 Monte Carlo code was used to calculate the quantitative dosimetric parameters suggested in the American Association of Physicists in Medicine (AAPM) TG-43/60. The Monte Carlo calculation results were compared with those from a dose point kernel code. The dose profiles agree well with each other. The gamma dose of 142Pr was evaluated. The gamma dose is 0.3 Gy at 1.0 cm with initial activity of 5.95 mCi and is insignificant to other organs. Measurements were performed to assess the 2-dimensional axial dose distributions using Gafchromic radiochromic film. The radiochromic film was calibrated using an X-ray machine calibrated against a National Institute of Standards and Technology (NIST) traceable ion chamber. A calibration curve was derived using a least squares fit of a second order polynomial. The measured dose distribution agrees well with results from the Monte Carlo simulation. The dose was 130.8 Gy at 6 mm from the seed center with initial activity of 5.95 mCi. AAPM TG-43/60 parameters were determined. The reference dose rate for 2 mm and 6 mm were 0.67 and 0.02 cGy/s/mCi, respectively. The geometry function, radial dose function and anisotropy function were generated.

Thesis (M.S.)--Rochester Institute of Technology, 2009. / Typescript. Includes bibliographical references (p. 57-63).

A mathematical model for polymer gel dosimeters was extended to simulate the effects of radiation depth doses of various radiation beams on the mass of polymer formed. The influences of monomer diffusion and temperature variation were investigated and predicted by the model. Simulation results indicate that both diffusion and temperature effects are most noticeable at the depth of maximum dose. Diffusion effects are larger for steep depth-dose curves with large dose gradients, while temperature effects are larger for extensive depth-dose curves that deliver high doses of radiation to a greater depth. Based on simulation results, involving a maximum dose of 5 Gy, the amount of additional polymer formed due to diffusion is small, ranging from 0.1 % for 15 MV x-ray photons to 2.6 % for Co60 γ-radiation. This small amount of additional polymer should not cause significant problems for the accuracy of depth-dose calibration curves, particularly if the depth of maximum dose is avoided. Inaccuracies caused by temperature effects are expected to be smaller than those caused by diffusion. Experimental studies were undertaken to improve the radiation dose response using x-ray Computed Tomography (CT). A new polymer gel dosimeter recipe with enhanced dose response was achieved by using a large quantity of N-isopropyl acrylamide (NIPAM) (15 wt%) to help dissolve the N,N’-methylene bisacrylamide (Bis) crosslinker. The solubility of Bis was substantially increased, allowing for large quantities of dissolved NIPAM and Bis in the system. The new dosimeter exhibits an enhanced dose sensitivity and dose resolution for x-ray CT imaging, which holds promise for clinical applications. The dose resolution of approximately 0.1 Gy, for up to absorbed doses of 50 Gy, for the new recipe is superior to that for previous dosimeter formulations developed for x-ray CT. / Thesis (Master, Chemical Engineering) -- Queen's University, 2010-12-21 18:10:28.37

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