Li Jun, Zhang Xile, Pan Yuxi, Zhuang Hongqing, Yang Ruijie
Department of Radiation Oncology, Peking University Third Hospital, Beijing, China.
Front Oncol. 2022 May 4;12:898175. doi: 10.3389/fonc.2022.898175. eCollection 2022.
This study attempts to evaluate Ray Tracing (RT) and Monte Carlo (MC) algorithms for CyberKnife treatments of spine lesions and determine whether the MC algorithm is necessary for all spine treatment and compare the RT algorithm and MC algorithm at various spine lesion sites.
The CyberKnife is used for stereotactic body radiotherapy for lesions in the cervical spine (30), thoracic spine (50), lumbar spine (30), and sacral spine (15). Dose was calculated using RT and MC algorithms for patients planned with the same beam angles and monitor units. Dose-volume histograms of the target and selected critical structures are evaluated.
The average target coverage of prescribed dose with MC algorithms was 94.80%, 88.47%, 92.52%, and 93.41%, respectively, in cervical, thoracic, lumbar, and sacral spine. For the thoracic spine, the RT algorithm significantly overestimates the percentage volume of the target covered by the prescribed dose, as well as overestimates doses to organs at risk in most cases, including lung, spinal cord, and esophagus. For cervical, lumbar, and sacral spine, the differences of the target coverage of prescription dose were generally less than 3% between the RT and MC algorithms. The differences of doses to organs at risk varied with lesion sites and surrounding organs.
In the thoracic spine lesions with beams through air cavities, RT algorithm should be limited and verified with MC algorithm, but the RT algorithm is adequate for treatment of cervical, lumbar, and sacral spine lesions without or with a small amount of beams passing through the lungs.
本研究旨在评估射波刀治疗脊柱病变时的射线追踪（RT）算法和蒙特卡罗（MC）算法，确定MC算法是否对所有脊柱治疗都必要，并比较RT算法和MC算法在不同脊柱病变部位的情况。
使用射波刀对颈椎（30例）、胸椎（50例）、腰椎（30例）和骶椎（15例）的病变进行立体定向体部放疗。对采用相同射束角度和监测单位计划的患者，使用RT算法和MC算法计算剂量。评估靶区和选定关键结构的剂量体积直方图。
在颈椎、胸椎、腰椎和骶椎中，MC算法对处方剂量的平均靶区覆盖率分别为94.80%、88.47%、92.52%和93.41%。对于胸椎，RT算法在大多数情况下显著高估了处方剂量覆盖靶区的体积百分比，同时也高估了对包括肺、脊髓和食管等危及器官的剂量。对于颈椎、腰椎和骶椎，RT算法和MC算法在处方剂量靶区覆盖率上的差异通常小于3%。对危及器官的剂量差异随病变部位和周围器官而变化。
在射束穿过气腔的胸椎病变中，应限制使用RT算法并通过MC算法进行验证，但RT算法足以治疗射束不穿过或少量穿过肺部的颈椎、腰椎和骶椎病变。
