Room: AAPM ePoster Library
Mobetron is used for intra-operative radiation therapy treatments (IORT). In an effort to provide image-guided IORT (IG-IORT) IntraOp and GMV have, respectively, developed plastic cones for Mobetron and an electron Monte Carlo treatment planning software (Radiance). The purpose of this study was to validate Radiance with plastic cones measurements with the overall objective of potentially using these developments for IG-IORT treatments.
This study was a two-step process. First, Radiance dose calculation parameters were optimized to best match our institution’s PDD commissioning data for a single energy (6 MeV) and cone size (8cm). Ten scans were computed and compared with the commissioning data.
Next, dose measurements in solid water were made using plastic cones (10cm or 4cm). A total of 6 exposures were performed on the Mobetron system using either 6MeV, 9MeV or 12MeV energies. Each exposure was designed to deliver 400 MU at dmax. Doses at four different depths were measured in a single exposure by placing EBT3 films in-between the solid water slabs. Depths ranged from 11-24mm, 17-37mm and 20-36mm for 6MeV, 9MeV and 12MeV, respectively. Measured dose from EBT3 films were compared with Radiance calculated values using the parameters found in the first part of the study.
Radiance parameters that most closely agree with commissioning data had an average percent difference of 1.1%. Generally, greatest variance was shown at greater depths (>25mm).
Average percent difference between calculated and measured doses in solid water was 3.9%. Percent differences generally increased at deeper depths due to comparing small values. The measured output factor difference between the metal and plastic cones (up to 4.8% higher for metal cones) was accounted for in the percent differences comparisons.
Conclusion: Dose calculated by Radiance agreed well with measurements in solid water, however, further validation is required for more complex phantom setups.
Funding Support, Disclosures, and Conflict of Interest: This study was partially funded by IntraOp Medical Inc.
Not Applicable / None Entered.