Department of Radiation Oncology, Peking University 3rd Hospital, Beijing, 100191, China.
J Appl Clin Med Phys. 2020 Apr;21(4):22-30. doi: 10.1002/acm2.12840. Epub 2020 Mar 14.
To investigate the set-up error and consequent dosimetric change in HexaPOD evo RT 6D couch under image-guided intensity-modulated radiotherapy (IG-IMRT) for primary malignant tumor of the cervical spine.
Ten cases with primary malignant tumor of the cervical spine were treated with intensity-modulated radiotherapy (IMRT) in our hospital from August 2013 to November 2014. The X-ray volumetric images (XVI) were scanned and obtained by cone-beam CT (CBCT). The six directions (6D) of set-up errors of translation and rotation were obtained by planned CT image registration. HexaPOD evo RT 6D couch made online correction of the set-up error, and then the CBCT was conducted to obtain the residual error.
We performed set-up error and dosimetric analysis. First, for the set-up error analysis, the average error in three translation directions of 6D set-up error of the primary tumor of the cervical spine was <2 mm, whereas the single maximum error (absolute value) is 7.0 mm. Among average errors of rotation direction, Rotation X (RX) direction 0.67° ± 0.04°, Rotation Y (RY) direction 1.06° ± 0.06°, Rotation Z (RZ) direction 0.78° ± 0.05°; and the single maximum error in three rotation directions were 2.8°, 3.8°, and 2.9°, respectively. On three directions (X, Y, Z axis), the extended distance from clinical target volume (CTV) to planning target volume (PTV) was 3.45, 3.17, and 3.90 mm by calculating, respectively. Then, for the dosimetric analysis, the parameters, including plan sum PTV D98 and D95, planning gross tumor volume D98 and D95, V100% of the plan sum were significantly lower than the treatment plan. Moreover, Dmax of the spinal cord was significantly higher than the treatment plan.
6D set-up error correction system should be used for accurate position calibration of precise radiotherapy for patients with malignant tumor of the cervical spine.
研究原发性颈椎恶性肿瘤在图像引导调强放疗（IG-IMRT）下使用 HexaPOD evo RT 6D 治疗床的摆位误差和随后的剂量变化。
2013 年 8 月至 2014 年 11 月，我院对 10 例原发性颈椎恶性肿瘤患者进行调强放疗（IMRT）。通过锥形束 CT（CBCT）扫描获得容积 X 射线图像（XVI）。通过计划 CT 图像配准获得六个方向（6D）的平移和旋转摆位误差。HexaPOD evo RT 6D 治疗床在线校正摆位误差，然后进行 CBCT 以获得残余误差。
我们进行了摆位误差和剂量分析。首先，对于摆位误差分析，原发性颈椎肿瘤 6D 摆位误差的三个平移方向的平均误差<2mm，而单个最大误差（绝对值）为 7.0mm。在旋转方向的平均误差中，旋转 X（RX）方向为 0.67°±0.04°，旋转 Y（RY）方向为 1.06°±0.06°，旋转 Z（RZ）方向为 0.78°±0.05°；三个旋转方向的单个最大误差分别为 2.8°、3.8°和 2.9°。在三个方向（X、Y、Z 轴）上，通过计算，CTV 到 PTV 的扩展距离分别为 3.45、3.17 和 3.90mm。然后，对于剂量分析，计划总 PTV D98 和 D95、计划大体肿瘤体积 D98 和 D95、计划总和 V100%等参数明显低于治疗计划，而且脊髓的 Dmax 明显高于治疗计划。
对于颈椎恶性肿瘤患者的精确放疗，应使用 6D 摆位误差校正系统进行精确的位置校准。
