Program Information

An Automated Monte Carlo Based QA Framework for Pencil Beam Scanning Treatments

J Shin

J Shin*, K Jee , B Clasie , N Depauw , T Madden , G Sharp , H Paganetti , H Kooy , Massachusetts General Hospital, Boston, MA

Presentations

SU-G-TeP4-4 (Sunday, July 31, 2016) 5:30 PM - 6:00 PM Room: ePoster Theater

Purpose: Prior to treating new PBS field, multiple (three) patient-field-specific QA measurements are performed: two 2D dose distributions at shallow depth (M1) and at the tumor depth (M2) with treatment hardware at zero gantry angle; one 2D dose distribution at iso-center (M3) without patient specific devices at the planned gantry angle. This patient-specific QA could be simplified by the use of MC model. The results of MC model commissioning for a spot-scanning system and the fully automated TOPAS/MC-based QA framework will be presented.

Methods: We have developed in-house MC interface to access a TPS (Astroid) database from a computer cluster remotely. Once a plan is identified, the interface downloads information for the MC simulations, such as patient images, apertures points, and fluence maps and initiates calculations in both the patient and QA geometries. The resulting calculations are further analyzed to evaluate the TPS dose accuracy and the PBS delivery.

Results: The Monte Carlo model of our system was validated within 2.0 % accuracy over the whole range of the dose distribution (proximal/shallow part, as well as target dose part) due to the location of the measurements. The averaged range difference after commissioning was 0.25 mm over entire treatment ranges, e.g., 6.5 cm to 31.6 cm.

Conclusion:As M1 depths range typically from 1 cm to 4 cm from the phantom surface, The Monte Carlo model of our system was validated within +- 2.0 % in absolute dose level over a whole treatment range. The averaged range difference after commissioning was 0.25 mm over entire treatment ranges, e.g., 6.5 cm to 31.6 cm.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by NIH/NCI under CA U19 21239


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