Room: ePoster Forums
Purpose: To measure the accuracy of surface guided radiation therapy (SGRT) (Catalyst HD, C-Rad) relative to orthogonal X-Ray localization (ExacTrac, Brainlab) for SRS.
Methods: An anthropomorphic head phantom (Brainlab) was used in a CT simulation for a brain lesion per department protocol and a virtual isocenter was placed in the frontal lobe region using iPlan TPS software (Brainlab). A treatment plan was created using arcs at the couch cardinal angles (270Â°, 225Â°, 180Â°, 135Â°, and 90Â°) and discrepancies between modalities were recorded for the Vertical, Longitudinal and Lateral directions. Discrete volumes for SGRT analysis were based on anatomical facial features and limited in volume to simulate multiple mask openings (Volumes = 2637cmÂ³ to 254 cmÂ³). The largest volume was lateral to the ears, superior to the eyebrows and inferior to the mouth, in contrast, the smallest volume includes only the eyes and bridge of the nose.
Results: There was a <1mm difference in the vertical and longitudinal directions until the nose was excluded (Volume = 603cmÂ³). The lateral direction shows the largest shift differences and was >1mm when ears are excluded (Volume = 1714cmÂ³). The total vector shift difference for Catalyst HD and ExacTrac was <1mm accuracy for a facial volume of 2637cmÂ³.
Conclusion: When appropriate volumes are used with SGRT, accuracy relative to orthogonal imaging can be <1mm. Individual clinics should verify accuracy of specific installations.
Funding Support, Disclosures, and Conflict of Interest: Research funded in part by a vendor grant.