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Initial evaluation of Advanced Collapsed cone Engine dose calculations in water medium for I‐125 seeds and COMS eye plaques
Author(s) -
Morrison Hali,
Me Geetha,
Larocque Matthew P.,
Veelen Bob,
Niatsetski Yury,
Weis Ezekiel,
Sloboda Ron S.
Publication year - 2018
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1002/mp.12776
Subject(s) - monte carlo method , materials science , biomedical engineering , kernel (algebra) , nuclear medicine , environmental science , mathematics , medicine , statistics , combinatorics
Purpose To investigate the dose calculation accuracy in water medium of the Advanced Collapsed cone Engine ( ACE ) for three sizes of COMS eye plaques loaded with low‐energy I‐125 seeds. Methods A model of the Oncura 6711 I‐125 seed was created for use with ACE in Oncentra ® Brachy (OcB) using primary‐scatter separated ( PSS ) point dose kernel and Task Group ( TG ) 43 datasets. COMS eye plaque models of diameters 12, 16, and 20 mm were introduced into the OcB applicator library based on 3D CAD drawings of the plaques and Silastic inserts. To perform TG ‐186 level 1 commissioning, treatment plans were created in OcB for a single source in water and for each COMS plaque in water for two scenarios: with only one centrally loaded seed, or with all seed positions loaded. ACE dose calculations were performed in high accuracy mode with a 0.5 × 0.5 × 0.5 mm 3 calculation grid. The resulting dose data were evaluated against Monte Carlo ( MC ) calculated doses obtained with MCNP 6, using both local and global percent differences. Results ACE doses around the source for the single seed in water agreed with MC doses on average within < 5% inside a 6 × 6 × 6 cm 3 region, and within < 1.5% inside a 2 × 2 × 2 cm 3 region. The PSS data were generated at a higher resolution within 2 cm from the source, resulting in this improved agreement closer to the source due to fewer approximations in the ACE dose calculation. Average differences in both investigated plaque loading patterns in front of the plaques and on the plaque central axes were ≤ 2.5%, though larger differences (up to 12%) were found near the plaque lip. Conclusions Overall, good agreement was found between ACE and MC dose calculations for a single I‐125 seed and in front of the COMS plaques in water. More complex scenarios need to be investigated to determine how well ACE handles heterogeneous patient materials.