Hu David Y, Xu Yiwen, Chen Yu-Hui, Khosravi Marjan, Lyatskaya Yulia, Bredfeldt Jeremy S, Hacker Fred L, Balboni Tracy A, Spektor Alexander, Cagney Daniel, Mak Raymond, Huynh Mai Anh
Department of Radiation Oncology, Brigham and Women's Hospital and Dana Farber Cancer Institute, Boston, Massachusetts.
Department of Data Science, Dana-Farber Cancer Institute, Boston, Massachusetts.
Adv Radiat Oncol. 2022 Apr 8;7(5):100961. doi: 10.1016/j.adro.2022.100961. eCollection 2022 Sep-Oct.
Our purpose was to optimize an image guided radiation therapy (IGRT) workflow to achieve practical setup accuracy in spine stereotactic body radiation therapy (SBRT). We assessed the time-saving efficiencies gained from incorporating planar kV midimaging as a surrogate for cone beam computed tomography (CBCT) for intrafraction motion monitoring.
We selected 5 thoracic spine SBRT patients treated in 5 fractions and analyzed patient shifts captured by a modified IGRT workflow using planar kV midimaging integrated with CBCT to maintain a tolerance of 1 mm and 1°. We determined the frequency at which kV midimaging captured intrafraction motion as validated on repeat CBCT and assessed the potential time and dosimetric advantages of our modified IGRT workflow.
Patient motion, detected as out-of-tolerance shifts on planar kV midimaging, occurred during 6 of 25 fractions (24%) and were validated on repeat CBCT 100% of the time. Observed intrafraction absolute shifts (mean ± standard deviation) for the 25 fractions were 0.39 ± 0.21, 0.56 ± 0.22, and 0.45 ± 0.21 mm for lateral-longitude-vertical translations and 0.38 ± 0.12°, 0.32 ± 0.09°, and 0.47 ± 0.14° for pitch-roll-yaw rotation, which if uncorrected, could have significantly affected target coverage and increased spinal cord dose. The average times for pretreatment imaging, midtreatment verification, and total treatment time were 8.94, 2.81, and 16.21 minutes. Our modified IGRT workflow reduced the total number of CBCTs required from 120 to 35 (70%) and imaging dose from 126.2 to 43.4 cGy (65.6%) while maintaining high fidelity for our patient population.
Accurate patient positioning was effectively achieved with use of multiple 2-dimensional-3-dimensional kV images and an average of 1 verification CBCT scan per fraction. Integration of planar kV midimaging can effectively reduce treatment time associated with spine SBRT delivery and minimize the potential dosimetric effect of intrafraction motion on target coverage and spinal cord dose.
我们的目的是优化图像引导放射治疗（IGRT）工作流程，以在脊柱立体定向体部放射治疗（SBRT）中实现实际的摆位精度。我们评估了将平面千伏（kV）中期成像作为锥束计算机断层扫描（CBCT）的替代方法用于分次内运动监测所带来的时间节省效率。
我们选择了5例接受5次分割治疗的胸椎SBRT患者，分析了通过改良的IGRT工作流程捕获的患者位移，该流程使用与CBCT集成的平面kV中期成像，以维持1毫米和1°的容差。我们确定了kV中期成像捕获分次内运动的频率，并通过重复CBCT进行验证，并评估了我们改良的IGRT工作流程在时间和剂量学方面的潜在优势。
在25次分割中的6次（24%）中，在平面kV中期成像上检测到患者运动超出容差范围，并在100%的重复CBCT上得到验证。25次分割中观察到的分次内绝对位移（平均值±标准差），横向-纵向-垂直平移分别为0.39±0.21、0.56±0.22和0.45±0.21毫米，俯仰-横滚-偏航旋转分别为0.38±0.12°、0.32±0.09°和0.47±0.14°，如果不进行校正，可能会显著影响靶区覆盖并增加脊髓剂量。预处理成像、治疗中期验证和总治疗时间的平均时间分别为8.94、2.81和16.21分钟。我们改良的IGRT工作流程将所需CBCT的总数从120次减少到35次（70%），成像剂量从126.2厘戈瑞减少到43.4厘戈瑞（65.6%），同时对我们的患者群体保持了高保真度。
通过使用多个二维-三维kV图像和平均每次分割1次验证CBCT扫描，有效地实现了准确的患者摆位。平面kV中期成像的整合可以有效减少与脊柱SBRT治疗相关的治疗时间，并将分次内运动对靶区覆盖和脊髓剂量的潜在剂量学影响降至最低。
