A New Approach to the Characterization of a Radiosurgery System: End-To-End Testing Using Phantom-Based 3D Dosimetry System
Y Wang1*, P Fan2, F Li3, A Xu4, T Wang5, J Choi6, J Adamovics7, C Wuu8, (1)New York Presbyterian/columbia University Irving Medical Center, New York, NY, (2) New York Presbyterian/Lawrence Hospital, Bronxville, NY, (3) New York Presbyterian/columbia University Irving Medical Center, New York, NY, (4) New York Presbyterian/columbia University Irving Medical Center, New York, NY, (5) New York Presbyterian/columbia University Irving Medical Center, New York, NY, (6) New York Presbyterian/columbia University Irving Medical Center, New York, NY,(7) HEURIS, INC., Skillman, NJ, (8) New York Presbyterian/columbia University Irving Medical Center
Presentations
TU-D1000-IePD-F3-3 (Tuesday, 7/12/2022) 10:00 AM - 10:30 AM [Eastern Time (GMT-4)]
Exhibit Hall | Forum 3
Purpose: The use of stereotactic radiosurgery systems has become widespread for the management of multiple small intracranial lesions. However, conventional 1D/2D quality assurance methodologies could not provide comprehensive information regarding the off-axis dosimetric and mechanical errors, dosimetric modeling of out-of-field doses and MLC characteristics, as well as dosimetric accuracy for multiple small lesions. Characterization of the radiosurgery system not only enhances the confidence in SRS treatments but also provides insights into treatment planning strategies. In this study a systematic end-to-end testing was performed using an integrated phantom-based 3D dosimetry system.
Methods: A fixed and movable tissue-equivalent holders were custom-made in STEEV phantom (CIRS, Inc.) to hold a 3D dosimeter, PRESAGE (Heuris Inc.). Ten benchmark single-isocenter VMAT plans were generated using HyperArc treatment planning system with different target number, target separations and off-axis distances. Hybrid plans were then delivered to the dosimeters using a TrueBeam linear accelerator. A comprehensive comparison of the 3D dose distribution between measurement and calculation was performed. To characterize the radiosurgery system, plan quality evaluation metrics (Conformal Index, Gradient Index, V10 and V12) were used for dosimetric assessment.
Results: The examined machine has minimal off-axis dosimetry errors, but mechanical error could increase up to 0.7 mm when the off-axis distance increases to 7 cm. Measured intermediate-low dose spillage is greater than the one in calculation, especially when the dose of one target is influenced by the out-of-field doses from neighboring targets. Measured 3D dose distribution was confirmed by a stack of EBT3 radiochromic films in the same phantom. Average gamma passing rate (3%, 2mm) between film and 3D dosimeter measurement is 99% while the one between TPS and 3D dosimeter is around 95%.
Conclusion: The integrated phantom-based 3D dosimetry system is a promising tool for SRS commissioning, machine characterization, treatment verification and independent auditing of SRS programs.
Funding Support, Disclosures, and Conflict of Interest: STEEV Phantom and the custom-made insert were provided by CIRS Inc. free of charge.
Keywords
Not Applicable / None Entered.
Taxonomy
Not Applicable / None Entered.
Contact Email