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Verification of a Monte Carlo Simulation Tool as a Second Check for TomoTherapy Treatment Planning

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J Yuan

J Yuan1*, Q Chen2 , Y Zheng1 , J Sohn1 , B Wessels1 , (1) University Hospitals, Case Medical Center, Dept of Radiation Oncology, Cleveland OHIO, (2) University of Virginia, Charlottesville, VA


SU-E-T-349 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To verify a virtual source model used in Monte Carlo (MC) TomoTherapy simulations and to provide a tool for the dose distribution second check for TomoTherapy treatment planning.

Methods: Published studies adopted the full MC model to simulate helical TomoTherapy which use phase space files (PSFs) at different scoring planes to facilitate patient dose calculations. We have developed a simple virtual source model (VSM) based on the commissioning data of helical TomoTherapy unit which can be exported from the treatment planning station (TPS). To calculate the patient dose distribution, TPS-generated sinograms are extracted from archived patient XML files and fluence maps are created by incorporating the open-close leaf time with leaf filter, jaw penumbra, and leaf latency. The VSM has been validated for various geometrical set-ups including open fields, heterogeneous media and clinical DQA cases.

Results: Good agreement was obtained between our VSM and a published full MC model for the test case of heterogeneous media. For the complex clinical head and neck (HN) case, the MC simulation of the DQA plan agreed with the film measurement with 98% of planar dose pixels passing the 2%/2 mm gamma value test. For the patient treatment plan itself, the MC simulation showed comparable DVHs for the planning target volumes (PTVs) and organs-at-risk (OARs). Deviations observed were consistent with literature.

Conclusion: The proposed VSM can be used in the MC method to accurately simulate the patient dose distributions for helical TomoTherapy.

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