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Design and Dose Calculation of Module Type Sealed Source Applicator Using Monte Carlo Simulation for Patient Specific Brachytherapy

C Choi

C Choi*, J Kim , J Park , S Park , M Chun , S Kang , H An , S Kim , Virginia Commonwealth University, Richmond, VA


SU-I-GPD-T-27 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: This study aimed to design a module type sealed source applicator for patient specific brachytherapy.

Methods: Dose distributions were evaluated by a Monte Carlo method to optimize the structure and materials of a module type sealed source applicator. Monte Carlo simulations were performed using MCNP6. Both cylindrical and hexagonal geometries were considered as basic design of applicator. P-32 isotope was selected as pure beta source. The inner part of the applicator consists of 3 layers, source, ceramic plate for beta shielding and tungsten plate for x-ray shielding. The outer part is stainless steel encapsulation. Six applicators were configured to evaluate the effect of gap in each applicator. Dose distribution for each applicator design was calculated at 1.25 mm and 2.5 mm depth. Dose uniformity was evaluated at each depth. Dose uniformity was defined as a ratio of area bounded by 80% isodose curve to that by 10% isodose curve. The dose distributions were normalized at 1.25 mm depth along the central axis of the centered applicator.

Results: The minimum percent doses caused by gaps between neighboring applicators were 12.5% and 22.2% for cylindrical and hexagonal models, respectively. The dose uniformity at 1.25 mm depth was 0.217 and 0.363 for cylindrical and hexagonal models, respectively. The percent depth doses at 2.5 mm were 18.3% and 17.5% for cylindrical and hexagonal models, respectively. Both cylindrical and hexagonal models showed similar depth dose distributions from each other. However, the dose distributions of hexagonal models were more uniform that those of cylindrical ones

Conclusion: : In terms of dose uniformity, hexagonal geometry turned out to be superior to cylindrical geometry.

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