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RayStation Clinical MLC Modeling and Commissioning

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C Allen

C Allen*, D Pavord, P Sansourekidou, M Sutton, Health Quest, Poughkeepsie, NY

SU-E-T-22 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: To accurately model the MLC in RayStation v3.0.0.251 and achieve acceptable clinical results.

Methods:MLC parameters including transmission, leaf tip width and tongue and groove effect were investigated using previously published tests. Transmission and leaf-tip geometry were assessed with a 2cm x 10cm MLC defined strip test on CAX and +/- 10 cm off axis with 16x20 jaws, and a step-wedge (Cadman, et al) irradiating 10 adjacent 1cm x 10cm MLC segments with step and shoot IMRT, while increasing the MU per segment by a fixed value. Conformal MLC shapes included the C-shape and Squiggle (TG-53), cross (Xiao, et al) and slanted rectangle (Phillips, et al).
RayStation dose calculations were compared to EBT3 film and PTW Octavius detector 729 ion chamber array measurements. Analysis software included FilmQA™ and PTW Verisoft v5.1. All tests were performed on a Varian Trilogy.
Additionally, six patient plans were created and IMRT QA was performed as clinical cases. Both split and non-split field IMRT QA was tested. Patient disease sites included pelvis, prostate, head and neck, and lung. A passing criteria of 2%,2mm was applied.

Results:After numerous iterations, the following was determined for both 6MV and 18MV: 0.017 tranmission, 0.05 cm tongue and groove, and 0.200 cm leaf tip width.
IMRT analysis for a total 66 fields resulted in a 98.5% (97.2% split, 100% split) overall passing with the 2%,2mm criteria.

Conclusion:The MLC model in RayStation v3.0.0.251 is clinically acceptable for patient treatment.

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