Clinical Implementation and Comparison of QA for Electron Therapy
Presentations
PO-GePV-T-63 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
ePoster Forums
Purpose: To investigate the accuracy of Monte Carlo dose calculation for electron therapy in Eclipse by comparing it to both measurements and calculation from Mobius.
Methods: Several treatment plans of electron beams with various energies, cone sizes, and circular cutouts of different radius in solid water phantom were generated with each beam delivering 100 MU. The dose at SSD=100cm and at the depth of dmax for each plan was acquired in Eclipse treatment planning system and normalized to the corresponding dose in 15x15 cm cone to calculate the cutout factor. Cutout factors were also measured on Truebeam machine with FC65G for large field and diamond detectors for small field in solid water phantom. The TPS calculated and measured cutout factors were compared to each other and to what was calculated from another MU verification software Mobius QA. Their differences were inspected and analyzed, and the table was then used to guide QA for breast patient electron plans.
Results: The difference of our measured clinical cutout factor from the one acquired from Eclipse was below 3% for most cases and below 5% for all cutout sizes above 6x6 cm. However, for some cutout sizes less than 6x6 cm the TPS calculation was larger than 5%, up to 13% for the 2x2 cutout for 6MeV. Use and evaluation of the measured data to predict patient specific cutout factors are in progress.
Conclusion: The accuracy of Monte Carlo dose calculation for electron therapy in Eclipse was acceptable for large cutout sizes which are mostly the clinical size. However, the accuracy became unacceptable under the condition of small cutout sizes less than 6x6 cm for certain energies.
Keywords
Electron Therapy, Quality Assurance
Taxonomy
TH- External Beam- Electrons: Quality Assurance - Linear accelerator
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