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First Clinical Experience with a Cloud Based Monte Carlo Secondary Dose Calculation for Tomotherapy Treatment Plans

J Ready

J Ready1*, Q Chen2 , S Benedict1 , Y Rong1 , (1) UC Davis Cancer Center, Sacramento, CA, (2) University of Virginia, Charlottesville, VA


MO-RAM-GePD-TT-4 (Monday, July 31, 2017) 9:30 AM - 10:00 AM Room: Therapy ePoster Theater

Purpose: To commission and validate a Cloud Based Monte Carlo (MC) application for dose verification calculations of Tomotherapy treatment plans.

Methods: An in-house MC code model for Tomotherapy was used to provide secondary dose calculations. Calculations were run on a cloud-based server, with all patient data anonymized prior to transmission. MC calculation run-time is generally less than 5 minutes per plan with an uncertainty parameter set to 0.03. Planned and measured doses from a set of manufacturer provided commissioning plans (TomoPhant) were compared to MC results. Fifteen prostate plans were analyzed to evaluate the clinical performance of the MC calculation relative to the TomoTherapy treatment planning system (TPS). D5, D50, and D95 dose levels were compared between MC and TPS calculations for bladder, femur, penile bulb, rectum, seminal vesicle, and PTV volumes.

Results: The MC results agree well with the TomoPhant calculation data, generally within 3% except for low dose regions outside of the field. The D5, D50, and D95 dose calculations from MC were all within acceptable agreement to TPS, with D95 being in closest agreement. The largest points of disagreement were at the D5 dose, for example PTV 3.6% (0–4.4%), seminal vesicle 2.6% (0.2–3.5%) and bladder 2.0% (-2.4–3.9%) average difference between MC and TPS.

Conclusion: This study introduces an accurate and reliable MC tool for secondary dose calculation on TomoTherapy treatment plans. The comparison of MC and TPS allows for the analysis and monitoring of dose calculation accuracies. The cloud costs required to perform a typical secondary dose calculation was well under $1 per patient. Future studies will include additional treatment sites, such as head & neck, brain, and pelvis.

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