Room: Stars at Night Ballroom 1
Purpose: To validate the treatment planning system (TPS) accuracy of ZAP-X (Zap Surgical, Inc.) SRS system through nondosimetric, dosimetric, and end-to-end (E2E) tests.
Methods: A comprehensive set of TPS validation tests were developed using published guidelines (TG-53, MPPG5a, TRS430). Equipment included CatPhan-500, Lucy 3D phantom, PTW MP3-XS water tank, PTW PinPoint and Exradin A16 ion chambers (IC), solid-water with 1cm high/low density slabs, and GafchromicTM EBT3 film. Nondosimetric validation included import/export, image registration (CT-CT/CT-MR), and structure/contouring/geometrical tests. Dosimetric validation included comparisons between TPS and water tank/solid-water measurements and E2E. RadCalc was used for independent MU verification. MD Anderson SRS head and RTsafe gel phantoms were used for absolute dose verification.
Results: Tools for image transfer/registration, contouring, and TPS display were functional. Slice thickness and distance accuracy was within 0.1mm, and volume accuracy was within 0-0.11cc. TPS volume measurement uncertainty was within 0.1-0.4cc. Point-dose measurements in water agreed to within Â±2% for cone sizes 10-25mm, and Â±1.1-5% for 7.5mm, across multiple depths from dmax (7mm) to 150mm. TPS and RadCalc agreed to within Â±4% (average difference: Â±1.3%) for all cone sizes (4-25mm). In homogeneous solid-water, point-dose measurements agreed to within Â±4% for cones sizes 7.5-25mm. With 1cm high/low density inserts, measurements were within Â±4.2% for cone sizes 10-25mm. Film-based E2E using 4mm/5mm cones resulted in gamma pass rate (GP) of 99.8% (2%/1.5mm). Lucy phantom IC dose measurements using 36 beams distributed along three non-coplanar arcs agreed to within Â±4% for cone sizes 10-25mm. MD Anderson head phantom yielded passing results, with 4% TLD agreement and GP of 95%/93% (5%/3mm) for coronal/sagittal film planes. The RTsafe gel phantom gave GP of >95% (5%/2mm) for all four targets.
Conclusion: Point-dose and planar measurements are in agreement with TPS calculations for multiple phantoms and setup geometries, validating the beam model for clinical use.