PURPOSE: We demonstrate the feasibility of optical imaging as a quality assurance tool for static small beamlets, and pretreatment verification tool for radiosurgery and volumetric-modulated arc therapy (VMAT) plans. METHODS: Small static beams and clinical VMAT plans were simulated in a treatment planning system (TPS) and delivered to a cylindrical tank filled with water-based liquid scintillator. Emission was imaged using a blue-sensitive, intensified CMOS camera time-gated to the linac pulses. For static beams, percentage depth and cross beam profiles of projected intensity distribution were compared to TPS data. Two-dimensional (2D) gamma analysis was performed on all clinical plans, and the technique was tested for sensitivity against common errors (multileaf collimator position, gantry angle) by inducing deliberate errors in the VMAT plans control points. The technique's detection limits for spatial resolution and the smallest number of control points that could be imaged reliably were also tested. The sensitivity to common delivery errors was also compared against a commercial 2.5D diode array dosimeter. RESULTS: A spatial resolution of 1 mm was achieved with our imaging setup. The optical projected percentage depth intensity profiles agreed to within 2% relative to the TPS data for small static square beams (5, 10, and 50 mm2 ). For projected cross beam profiles, a gamma pass rate >99% was achieved for a 3%/1 mm criteria. All clinical plans passed the 3%/3 mm criteria with >95% passing rate. A static 5 mm beam with 20 Monitor Units could be measured with an average percent difference of 5.5 ± 3% relative to the TPS. The technique was sensitive to multileaf collimator errors down to 1 mm and gantry angle errors of 1°. CONCLUSIONS: Optical imaging provides ample spatial resolution for imaging small beams. The ability to faithfully image down to 20 MU of 5 mm, 6 MV beamlets prove the ability to perform quality assurance for each control point within dynamic plans. The technique is sensitive to small offset errors in gantry angles and multileaf collimator (MLC) leaf positions, and at certain scenario, it exhibits higher sensitivity than a commercial 2.5D diode array.
PURPOSE: We demonstrate the feasibility of optical imaging as a quality assurance tool for static small beamlets, and pretreatment verification tool for radiosurgery and volumetric-modulated arc therapy (VMAT) plans. METHODS: Small static beams and clinical VMAT plans were simulated in a treatment planning system (TPS) and delivered to a cylindrical tank filled with water-based liquid scintillator. Emission was imaged using a blue-sensitive, intensified CMOS camera time-gated to the linac pulses. For static beams, percentage depth and cross beam profiles of projected intensity distribution were compared to TPS data. Two-dimensional (2D) gamma analysis was performed on all clinical plans, and the technique was tested for sensitivity against common errors (multileaf collimator position, gantry angle) by inducing deliberate errors in the VMAT plans control points. The technique's detection limits for spatial resolution and the smallest number of control points that could be imaged reliably were also tested. The sensitivity to common delivery errors was also compared against a commercial 2.5D diode array dosimeter. RESULTS: A spatial resolution of 1 mm was achieved with our imaging setup. The optical projected percentage depth intensity profiles agreed to within 2% relative to the TPS data for small static square beams (5, 10, and 50 mm2 ). For projected cross beam profiles, a gamma pass rate >99% was achieved for a 3%/1 mm criteria. All clinical plans passed the 3%/3 mm criteria with >95% passing rate. A static 5 mm beam with 20 Monitor Units could be measured with an average percent difference of 5.5 ± 3% relative to the TPS. The technique was sensitive to multileaf collimator errors down to 1 mm and gantry angle errors of 1°. CONCLUSIONS: Optical imaging provides ample spatial resolution for imaging small beams. The ability to faithfully image down to 20 MU of 5 mm, 6 MV beamlets prove the ability to perform quality assurance for each control point within dynamic plans. The technique is sensitive to small offset errors in gantry angles and multileaf collimator (MLC) leaf positions, and at certain scenario, it exhibits higher sensitivity than a commercial 2.5D diode array.
Authors: Joanne N Davis; Clinton Medbery; Sanjeev Sharma; John Pablo; Frank Kimsey; David Perry; Alexander Muacevic; Anand Mahadevan Journal: Radiat Oncol Date: 2015-05-15 Impact factor: 3.481
Authors: Emil Schüler; Munjal Acharya; Pierre Montay-Gruel; Billy W Loo; Marie-Catherine Vozenin; Peter G Maxim Journal: Med Phys Date: 2022-01-19 Impact factor: 4.506
Authors: Daniel A Alexander; Petr Bruza; Aris G Rassias; Jacqueline M Andreozzi; Brian W Pogue; Rongxiao Zhang; David J Gladstone Journal: Med Phys Date: 2021-05-09 Impact factor: 4.506