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Large Scale Recalculation of Quality Assurance Plans Using Treatment Planning System Scripting for Dose Calculation Algorithm Validation

R Popple*, R Cardan, The University of Alabama at Birmingham, Birmingham, AL


(Sunday, 7/14/2019) 4:00 PM - 4:30 PM

Room: Exhibit Hall | Forum 7

Purpose: To evaluate commissioning of a dose calculation algorithm using large-scale recalculation of quality assurance plans.

Methods: A tool was developed for recalculation of film QA plans using the application programming interface (API) of a commercial treatment planning system. Upon algorithm parameter changes, the tool allowed for batch dose calculation without user interaction. We selected 423 measurements using radiochromic film in an acrylic phantom from our VMAT SRS patient-specific quality assurance database. For multiple target plans there were two measurements corresponding to the largest and smallest target. The measurements were for 301 plans, of which 123 had multiple targets. The plans, originally calculated using AAA 13.6.23, were recalculated using AcurosXB 15.5.11 with GPU acceleration and grid size 1 mm. The plans were calculated for source sizes 0 and 0.5 mm and dosimetric leaf gap (DLG) 0.5, 0.75, and 1 mm. The calculation-to-film ratio in the high-dose region (90% of the maximum dose) and gamma with criteria 1%/1mm were calculated.

Results: The median target size was 16.6mm (range 2.5 to 43.1). The total time to calculate the set of plans was approximately 9.5 hours. Mean time for dose calculation was 58 seconds per plan (range 23 to 110), with an additional 22 seconds for plan preparation tasks. Mean calculation-to-film ratio ranged from 0.987 to 1.045 for source size/DLG 0.5 mm/0.5 mm and 0 mm/1 mm respectively. The minimum value of median gamma for the 6 parameter sets was 0.26 for source size/DLG 0.5 mm/0.75 mm, for which the calculation-to-film ratio was 1.010.

Conclusion: Of the 6 tested configurations, 0.5 mm source size and 0.75 mm DLG had the best agreement with film as measured by gamma. Calculations of additional configurations are ongoing. Automation using scripting provides an efficient method for parameter optimization and validation during commissioning of dose calculation algorithms.


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