Woods Kyle, Rong Yi
Department of Radiation Oncology, Ohio State University, Columbus, Ohio 43210.
Department of Radiation Oncology, University of California Davis Comprehensive Cancer Center, Sacramento, California 95817.
Med Phys. 2015 Nov;42(11):6488-97. doi: 10.1118/1.4932363.
To develop and establish a comprehensive gating commissioning and quality assurance procedure in compliance with TG-142.
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.
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.
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.
制定并建立符合TG - 142的全面的门控调试和质量保证程序。
本研究使用了八台瓦里安TrueBeam直线加速器。门控调试包括端到端测试和基线建立。端到端测试使用了一个带有肺部内部移动圆柱体的CIRS动态胸部体模，该体模在靶区移动时用于携带光学模拟发光探测器（OSLD）和Gafchromic EBT2胶片，以进行点剂量检查和二维轮廓检查。此外，还为兆伏（MV）和千伏（kV）射线束建立了束流开启时间延迟和替代物校准的基线。使用运动模拟装置（MotionSim）在平台上提供周期性运动，与替代物运动同步。分析并比较了总体精度和不确定性。
对于相位和幅度门控照射，OSLD读数与计划剂量相比在5%以内（在测量不确定度范围内）。胶片结果显示，对于标准正弦运动，与预测剂量的一致性小于3%。MV射线束的门控开启时间精度平均为139±10毫秒，kV射线束为92±11毫秒。替代物运动的时间延迟取决于运动速度，慢速时平均为54.6±3.1毫秒，中速时为24.9±2.9毫秒，快速时为23.0±20.1毫秒。
引入了全面的门控调试程序，以验证输出精度并建立呼吸门控的时间精度基线。如TG - 142所建议，这些基线是常规质量保证测试所必需的。
