Venkataraman Sankar, Abdalmassih Michael, Hanumanthappa Nikesh, Pareek Vibhay, Kulshrestha Rashi, Lambert Pascal, Rathod Srinivas, Butler Jim, Dubey Arbind
Department of Radiation Oncology, CancerCare Manitoba, Winnipeg, MB, Canada.
University of Manitoba, Winnipeg, MB, Canada.
J Radiosurg SBRT. 2022;8(4):305-312.
Stereotactic body radiation therapy (SBRT) for the spine is challenging due to high-dose gradients sparing the cord in the treatment plans. We present our findings of initial setup error and intrafraction motion from Cone-beam computed tomography (CBCT) imaging.
A total of 47 patients treated with spine SBRT with a total of 154 fractions following a fractionation schedule of 16 Gy in 1, 24 Gy in 2, and 30 Gy in 5 fractions were part of this study. Pre-treatment CBCT was used for localization of the target and couch shifts were applied based on target volume matching to the planning CT image set. Post-treatment CBCT was acquired for all fractions. Intrafraction motion (IFM) was calculated by matching post-treatment CBCT to planning CT for the target volume.
The average Intrafraction motion was 1.6 ± 0.9 mm for the study cohort. The average and standard deviation of intrafraction motion were 0.4 ± 1.1 (AP), 0.3 ± 0.9 (SI) and 0.2 ± 1.2 (RL) respectively. The average Initial setup error tabulated from the offline review showed a mean value of 7.8 ± 5.3 mm. The average and standard deviation of the initial setup error were 2.5 ± 5.5 (AP), 2.4 ± 5.3(SI), and 0.8 ± 4.5(RL) respectively. The correlation of intrafraction motion with body mass index (BMI) and the number of consecutive vertebrae levels did not show any statistical significance, however, there was a significant association with gender as women showed more IFM.
Our study on intrafraction motion from CBCT images reinforced the importance of immobilization and imaging for positioning spine SBRT patients.
The need for CBCT and imagining for positional errors is emphasized while treating with SBRT spine and the need for proper immobilization techniques.
由于在治疗计划中需高剂量梯度以保护脊髓，脊柱立体定向体部放射治疗（SBRT）具有挑战性。我们展示了锥形束计算机断层扫描（CBCT）成像得出的初始摆位误差和分次内运动的研究结果。
本研究纳入了47例接受脊柱SBRT治疗的患者，共154个分次，采用的分割方案为1次16 Gy、2次24 Gy以及5次30 Gy。治疗前CBCT用于靶区定位，并根据靶区体积与计划CT图像集匹配情况进行治疗床移位。所有分次均采集治疗后CBCT。通过将治疗后CBCT与计划CT的靶区体积进行匹配来计算分次内运动（IFM）。
研究队列的平均分次内运动为1.6±0.9 mm。分次内运动的平均值和标准差分别为前后方向（AP）0.4±1.1、左右方向（SI）0.3±0.9以及头脚方向（RL）0.2±1.2。离线分析得出的平均初始摆位误差为7.8±5.3 mm。初始摆位误差的平均值和标准差分别为前后方向2.5±5.5、左右方向2.4±5.3以及头脚方向0.8±4.5。分次内运动与体重指数（BMI）以及连续椎体节段数量之间的相关性未显示出任何统计学意义，然而，与性别存在显著关联，因为女性的分次内运动更多。
我们对CBCT图像分次内运动的研究强化了脊柱SBRT患者固定和成像定位的重要性。
强调了在脊柱SBRT治疗中使用CBCT以及对位置误差进行成像的必要性，以及适当固定技术的必要性。
