Author: Angel Gomez, Titania Juang, Grace Gwe-Ya Kim, Boyu Meng 👨🔬
Affiliation: UC San Diego, UCSD, University of California San Diego 🌍
Purpose: Single-Isocenter Multiple Targets (SIMT) Stereotactic Radiosurgery (SRS) is widely used for its precision and effectiveness. However, standardized quality assurance (QA) protocols for SIMT SRS and the integration of surface-guided radiotherapy (SGRT) and image-guided radiotherapy (IGRT) for setup and monitoring remain underexplored. This study aims to establish a comprehensive SRS QA protocol and evaluate SGRT and IGRT under conditions such as camera occlusion and skin tone variation.
Methods: A 3D-printed anthropomorphic head phantom with a Multi-Met Winston-Lutz cube (Sun Nuclear Corporation, Melbourne, FL) containing radiopaque fiducial markers was used to evaluate deviations in isocenter and off-axis targets during Winston-Lutz (WL) tests across 15 fields. An IGRT technique was implemented by setting up the phantom based on matching of the skull, target deviations were reported and compared to traditional WL. SGRT accuracy was assessed using AlignRT (Vision RT Ltd., London, UK) systems under varying conditions, including camera occlusion at gantry angles and skin tones simulated using makeup foundations
Results: WL tests with manual fiducial matching showed mean deviations of 0.35 ± 0.15 mm (isocenter) and 0.49 ± 0.26 mm (off-axis), while IGRT setup resulted in 0.41 ± 0.21 mm (isocenter) and 0.59 ± 0.35 mm (off-axis), respectively. SGRT showed significant camera occlusion at gantry angle 270 degree, with a 23.66 ± 1.70% decrease in percentage overlap compared to the 0 degree reference. For skin tone variation it was found that detectability for darker skin tone decreases with surface signal detection dropping from 74.13 ± 1.31% (baseline) in percentage overlap to 65.45 ± 1.24%.
Conclusion: The anthropomorphic phantom in this study improved QA efficiency and closely mimicked clinical setups. Skin tone settings were identified as critical setup parameters for SGRT performance. These findings provide valuable guidance for integrating SGRT and IGRT into clinical SRS treatment and monitoring.