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Technical Report: TG‐142 compliant and comprehensive quality assurance tests for respiratory gating
Author(s) -
Woods Kyle,
Rong Yi
Publication year - 2015
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 - 10.1118/1.4932363
Subject(s) - quality assurance , gating , truebeam , calibration , imaging phantom , synchronizing , physics , nuclear medicine , dosimetry , optics , beam (structure) , medical physics , computer science , linear particle accelerator , medicine , telecommunications , physiology , external quality assessment , pathology , quantum mechanics , transmission (telecommunications)
Purpose: To develop and establish a comprehensive gating commissioning and quality assurance procedure in compliance with TG‐142. Methods: Eight Varian TrueBeam Linacs were used for this study. Gating commissioning included an end‐to‐end test and baseline establishment. The end‐to‐end test was performed using a CIRS dynamic thoracic phantom with a moving cylinder inside the lung, which was used for carrying both optically simulated luminescence detectors (OSLDs) and Gafchromic EBT2 films while the target is moving, for a point dose check and 2D profile check. In addition, baselines were established for beam‐on temporal delay and calibration of the surrogate, for both megavoltage (MV) and kilovoltage (kV) beams. A motion simulation device (MotionSim) was used to provide periodic motion on a platform, in synchronizing with a surrogate motion. The overall accuracy and uncertainties were analyzed and compared. Results: The OSLD readings were within 5% compared to the planned dose (within measurement uncertainty) for both phase and amplitude gated deliveries. Film results showed less than 3% agreement to the predicted dose with a standard sinusoid motion. The gate‐on temporal accuracy was averaged at 139 ± 10 ms for MV beams and 92 ± 11 ms for kV beams. The temporal delay of the surrogate motion depends on the motion speed and was averaged at 54.6 ± 3.1 ms for slow, 24.9 ± 2.9 ms for intermediate, and 23.0 ± 20.1 ms for fast speed. Conclusions: A comprehensive gating commissioning procedure was introduced for verifying the output accuracy and establishing the temporal accuracy baselines with respiratory gating. The baselines are needed for routine quality assurance tests, as suggested by TG‐142.