To evaluate the accuracy of a commercial optical surface tracking (OST) system and to demonstrate how it can be implemented to monitor patient positioning during non‐coplanar single isocenter stereotactic treatments of brain metastases. A 3‐camera OST system was used (Catalyst HD™, C‐RAD) on a TruebeamSTx with a 6DoF couch. The setup accuracy and agreement between the OST system, and CBCT and kV‐MV imaging at couch angles 0° and 270°, respectively, were examined. Film measurements at 3 depths in the Rando‐Alderson phantom were performed using a single isocenter non‐coplanar VMAT plan containing 4 brain lesions. Setup of the phantom was performed with CBCT at couch 0° and subsequently monitored by OST at other couch angles. Setup data for 7 volunteers were collected to evaluate the accuracy and reproducibility of the OST system at couch angles 0°, 45°, 90°, 315°, and 270°. These results were also correlated to the couch rotation offsets obtained by a Winston‐Lutz (WL) test. The Rando‐Alderson phantom, as well as volunteers, were fixated using open face masks (Orfit). For repeated tests with the Rando‐Alderson phantom, deviations between rotational and translational isocenter corrections for CBCT and OST systems are always within 0.2° (pitch, roll, yaw), and 0.1mm and 0.5mm (longitudinal, lateral, vertical) for couch positions 0° and 270°, respectively. Dose deviations between the film and TPS doses in the center of the 4 lesions were −1.2%, −0.1%, −0.0%, and −1.9%. Local gamma evaluation criteria of 2%/2 mm and 3%/1 mm yielded pass rates of 99.2%, 99.2%, 98.6%, 89.9% and 98.8%, 97.5%, 81.7%, 78.1% for the 4 lesions. Regarding the volunteers, the mean translational and rotational isocenter shift values were (0.24 ± 0.09) mm and (0.15 ± 0.07) degrees. Largest isocenter shifts were found for couch angles 45˚ and 90˚, confirmed by WL couch rotation offsets. Patient monitoring during non‐coplanar VMAT treatments of brain metastases is feasible with submillimeter accuracy.

中文翻译：

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光学表面跟踪系统在多脑转移的非共面单等中心治疗中的潜力。

评估商用光学表面跟踪（OST）系统的准确性，并演示如何在非共面单等中心立体定向脑转移治疗中监测其位置。在配备6DoF沙发床的TruebeamSTx上使用了3台摄像机OST系统（Catalyst HD™，C-RAD）。分别检查了OST系统与CBCT和kV-MV成像分别在0°和270°倾斜角下的设置精度和一致性。使用包含4个脑部病变的单个等中心非共面VMAT计划在Rando-Alderson幻影的3个深度进行胶片测量。幻像的建立是在CBCT的0°躺椅上进行的，随后通过OST在其他躺椅角度进行监控。收集了7位志愿者的设置数据，以评估OST系统在0°躺椅角度下的准确性和可重复性，45°，90°，315°和270°。这些结果还与通过Winston-Lutz（WL）测试获得的沙发床旋转偏移量相关。使用开放式口罩（Orfit）固定Rando-Alderson幻像以及志愿者。对于使用Rando-Alderson体模进行的重复测试，CBCT和OST系统的旋转和平移等角点校正之间的偏差始终在0.2°（俯仰，滚动，偏航）范围内，沙发床的偏差始终在0.1mm和0.5mm（纵向，横向，垂直）范围内位置分别为0°和270°。在4个病灶中心的胶片和TPS剂量之间的剂量偏差为-1.2％，-0.1％，-0.0％和-1.9％。4个病变的局部伽玛评估标准为2％/ 2 mm和3％/ 1 mm，合格率分别为99.2％，99.2％，98.6％，89.9％和98.8％，97.5％，81.7％，78.1％。关于志愿者 平均平移和旋转等角点偏移值为（0.24±0.09）mm和（0.15±0.07）度。WL床旋转偏移证实了45°和90°床角的最大等中心位移。在非共面的VMAT治疗脑转移过程中进行患者监测是可行的，且精度可达到亚毫米级。