目的: 评估锥形束CT (cone-beam CT, CBCT)引导下头颈部肿瘤调强放射治疗(intensity-modulated radiation therapy, IMRT)的分次内和分次间摆位偏差, 以及6D治疗床(HexaPOD evo RT 6D)对这些偏差的纠正能力和稳定性。方法: 选择北京大学第三医院肿瘤放疗科2019年5月至2022年4月头颈部肿瘤患者的病例资料进行回顾性分析, 利用医科达公司AXESSE医用直线加速器进行前置CBCT扫描, 通过骨窗模式与计划参考影像进行配准, 自动或手动调整6D治疗床以校准偏差, 随后进行第二次CBCT扫描以确认偏差校正。通过比较校正前后的配准结果, 记录患者在平移(X、Y、Z方向)和旋转(Rx、Ry、Rz方向)上的摆位误差, 并对分次间及分次内的摆位误差进行分析。结果: 在连续入组59例患者的506次CBCT扫描中, 成功获取并在线校正了6D治疗床的摆位误差数据, 校正前后摆位误差的最大值分别为0.90 cm与0.04 cm (X方向)、1.74 cm与0.09 cm (Y方向)、1.80 cm与0.09 cm (Z方向), 以及2.90°与0.14°(Rx方向)、3.00°与0.15°(Ry方向)、3.00°与0.15°(Rz方向)。在线校正明显减小了各方向上的平均摆位误差, 平移误差(X、Y、Z方向)和旋转误差(Rx、Ry、Rz方向)的平均值分别从0.18 cm、0.22 cm、0.25 cm和0.82°、1.11°、0.73°减少至0.01 cm、0.01 cm、0.01 cm和0.04°、0.06°、0.04°(P均 < 0.001)。校正后, 在X、Y、Z方向上平移误差小于0.10 cm的频率分别达到99.60%、98.62%、95.45%, 旋转误差小于0.20°的频率均达到或超过99.80%。结论: 结合CBCT和6D治疗床的在线校正显著降低了头颈部放疗患者的平移和旋转摆位误差, 极大提高了治疗的精准度。

Objective: To evaluate the intra-fraction and inter-fraction positional deviations in head and neck tumor patients undergoing intensity-modulated radiation therapy (IMRT) guided by cone-beam CT (CBCT), as well as the correction capability and stability of the HexaPOD evo RT 6D couch in addressing these deviations. Methods: From May 2019 to April 2022, 59 consecutive patients with head and neck tumors were enrolled at the Department of Radiation Oncology, Peking University Third Hospital.Using the Elekta AXESSE image-guided stereotactic treatment system, a pre-treatment CBCT scan was performed, followed by bone window mode registration with the planning reference images.Deviations were corrected automatically or manually on the 6D couch, followed by a second CBCT scan for confirmation of the deviation correction.Positional errors in translation (X, Y, Z directions) and rotation (Rx, Ry, Rz directions) were recorded before and after correction, and intra-fraction and inter-fraction positional errors were analyzed. Results: Positional error data before and after correction of the 6D couch were successfully obtained and corrected online in 506 CBCT scans.The maximum positional errors before and after correction were 0.90 cm to 0.04 cm (X direction), 1.74 cm to 0.09 cm (Y direction), 1.80 cm to 0.09 cm (Z direction), and 2.90° to 0.14°(Rx direction), 3.00° to 0.15°(Ry direction), 3.00° to 0.15°(Rz direction), respectively.The mean absolute values of translational (X, Y, Z directions) and rotational (Rx, Ry, Rz directions) errors significantly decreased after online correction, from 0.18 cm, 0.22 cm, 0.25 cm, and 0.82°, 1.11°, 0.73° to 0.01 cm, 0.01 cm, 0.01 cm, and 0.04°, 0.06°, 0.04°(all P values < 0.001).After correction, the frequencies of translational errors less than 0.10 cm in the X, Y, Z directions were 99.60%, 98.62%, and 95.45%, respectively, and the frequencies of rotational errors less than 0.2° were all above 99.80%. Conclusion: Online correction combined with CBCT and the 6D couch significantly reduces both translational and rotational positional errors in patients undergoing head and neck radiation therapy, greatly enhancing the precision of treatment.