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SU‐G‐JeP1‐04: Characterization of a High‐Definition Optical Patient Surface Tracking System Across Five Installations
Author(s) -
Smith T,
Ayan A,
Cochran E,
Woollard J,
Gupta N
Publication year - 2016
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4956979
Subject(s) - imaging phantom , truebeam , tracking (education) , computer science , rotation (mathematics) , displacement (psychology) , linear particle accelerator , computer vision , match moving , medical imaging , motion (physics) , biomedical engineering , artificial intelligence , physics , optics , beam (structure) , medicine , pedagogy , psychotherapist , psychology
Purpose: To assess the performance of Varian's real‐time, Optical Surface Monitoring System (OSMS) by measuring relative regular and irregular surface detection accuracy in 6 degrees of motion (6DoM), across multiple installations. Methods: Varian's Intracranial SRS Package includes OSMS, which utilizes 3 HD camera/projector pods to map a patient surface, track intra‐fraction motion, and gate the treatment beam if motion exceeds a threshold. To evaluate motion‐detection accuracy of OSMS, we recorded shifts of a cube‐shaped phantom on a single Varian TrueBeam linear accelerator as known displacements were performed incrementally across 6DoM. A subset of these measurements was repeated on identical OSMS installations. Phantom motion was driven using the TrueBeam treatment couch, and incremented across ±2cm in steps of 0.1mm, 1mm, and 1cm in the cardinal planes, and across ±40° in steps of 0.1°, 1°, and 5° in the rotational (couch kick) direction. Pitch and Roll were evaluated across ±2.5° in steps of 0.1° and 1°. We then repeated this procedure with a frameless SRS setup with a head phantom in a QFix Encompass mask. Results: Preliminary data show OSMS is capable of detecting regular‐surfaced phantom displacement within 0.03±0.04mm in the cardinal planes, and within 0.01±0.03° rotation across all planes for multiple installations. In a frameless SRS setup, OSMS is accurate to within 0.10±0.07mm and 0.04±0.07° across 6DoM. Additionally, a reproducible “thermal drift” was observed during the first 15min of monitoring each day, and characterized by recording displacement of a stationary phantom each minute for 25min. Drift settled after 15min to an average delta of 0.26±0.03mm and 0.38±0.03mm from the initial capture in the Y and Z directions, respectively. Conclusion: For both regular surfaces and clinical SRS situations, OSMS exceeds quoted detection accuracy. To reduce error, a warm‐up period should be employed to allow camera/projector pod thermal stabilization.