目的：在脊柱立体定向身体放射治疗中，必须从批准的患者设置中量化分数内六自由度（6DoF）残余误差或运动，以进行精确的束输送。然而,先前报告的错误未在光束传递过程中获得。因此,我们的目的是量化的6DoF残余误差和运动期间使用并发锥形束计算机断层扫描（CBCT）成像技术的弧形束传输，照射内CBCT。
方法：连续15名患者，19个不同治疗地点的计划，分析了199张CBCT图像。使用ExacTrac系统进行预照射CBCT以验证从初始患者设置的偏移。在通过两个或三个共面全弧旋转的光束传递过程中，同时进行CBCT成像。随后，重建了照射内CBCT图像。基于骨骼，将辐照前和辐照内CBCT图像与计划CT图像进行严格配准，以量化6DoF残余误差。
结果：使用辐照前和辐照内CBCT量化的6DoF残余误差在2.0mm/2.0°以内，除了一个测量。预照射CBCT到最后一次电弧束递送结束后的平均经过时间(平均值±标准偏差[min:sec])为6:08±1:25和7:54±2:14,分别。几个方向的残余误差的均方根显示出显着差异；但是，它们在1.0毫米/1.0°以内。与时间相关的分析表明，剩余误差随着时间的流逝而增加。
结论：与使用前，梁间,和6DoF后图像指导，可以在标准治疗时隙内获取。
OBJECTIVE: Quantifying intra-fractional six-degree-of-freedom (6DoF) residual errors or motion from approved patient setups is necessary for accurate beam delivery in spine stereotactic body radiotherapy. However, previously reported errors were not acquired during beam delivery. Therefore, we aimed to quantify the 6DoF residual errors and motions during arc beam delivery using a concurrent cone-beam computed tomography (CBCT) imaging technique, intra-irradiation CBCT.
METHODS: Consecutive 15 patients, 19 plans for various treatment sites, and 199 CBCT images were analyzed. Pre-irradiation CBCT was performed to verify shifts from the initial patient setup using the ExacTrac system. During beam delivery by two or three co-planar full-arc rotations, CBCT imaging was performed concurrently. Subsequently, an intra-irradiation CBCT image was reconstructed. Pre- and intra-irradiation CBCT images were rigidly registered to a planning CT image based on the bone to quantify 6DoF residual errors.
RESULTS: 6DoF residual errors quantified using pre- and intra-irradiation CBCTs were within 2.0 mm/2.0°, except for one measurement. The mean elapsed time (mean ± standard deviation [min:sec]) after pre-irradiation CBCT to the end of the last arc beam delivery was 6:08 ± 1:25 and 7:54 ± 2:14 for the 2- and 3-arc plans, respectively. Root mean squares of residual errors for several directions showed significant differences; however, they were within 1.0 mm/1.0°. Time-dependent analysis revealed that the residual errors tended to increase with elapsed time.
CONCLUSIONS: The errors represent the optimal intra-fractional error compared with those acquired using the pre-, inter-beam, and post-6DoF image guidance and can be acquired within a standard treatment timeslot.
