Department of Radiation Oncology, Saint Francis Hospital and Medical Center, Hartford, Connecticut.
Department of Radiation Oncology, Saint Francis Hospital and Medical Center, Hartford, Connecticut.
Pract Radiat Oncol. 2011 Oct-Dec;1(4):251-60. doi: 10.1016/j.prro.2011.03.001. Epub 2011 May 5.
To evaluate a Monte Carlo (MC) treatment planning system for CyberKnife treatments of cranial and extracranial lesions and determine whether it is necessary for all treatment sites. Dose distributions are compared to those calculated with a ray-tracing algorithm. Maximum doses and dose-volume histograms for the target and selected critical structures are analyzed.
The CyberKnife is used for stereotactic radiosurgery-radiotherapy of intracranial lesions (91) as well as stereotactic body radiotherapy for lesions in the spine (24), lung (58), and pelvis (36). The Multiplan system is an inverse treatment planning system which uses an effective path length (EPL) algorithm (sometimes referred to as ray-trace) for dose calculations. In addition, an MC algorithm became clinically available in late 2007.
The maximum doses calculated by the EPL to targets in the lung were uniformly larger than the doses calculated by MC by up to a factor of 1.32. In addition, large differences in target and critical organs' dose coverage were observed. In general, more beams traversing larger distances through low density lung are associated with larger differences. For other sites such as brain and pelvis targets the differences in maximum doses and tumor coverage were generally less than 5% between the 2 calculation methods.
The MC algorithm should be consistently used for treatment plans of lung lesions and lesions near large air cavities, but the faster EPL algorithm is adequate for treatment sites with less tissue heterogeneity.
评估适用于 CyberKnife 治疗颅内外病变的蒙特卡罗（MC）治疗计划系统，以确定其是否适用于所有治疗部位。将剂量分布与射线追踪算法计算的结果进行比较。分析靶区和选定关键结构的最大剂量和剂量体积直方图。
CyberKnife 用于颅内病变（91 例）的立体定向放射外科治疗-放疗，以及脊柱（24 例）、肺（58 例）和骨盆（36 例）的立体定向体部放疗。Multiplan 系统是一种逆向治疗计划系统，它使用有效路径长度（EPL）算法（有时称为射线追踪）进行剂量计算。此外，MC 算法于 2007 年末在临床上可用。
EPL 计算的肺内靶区的最大剂量普遍比 MC 计算的剂量大 1.32 倍。此外，还观察到靶区和关键器官剂量覆盖的差异很大。一般来说，穿过低密度肺的更多光束穿过更大的距离会导致更大的差异。对于其他部位，如脑和骨盆靶区，两种计算方法之间的最大剂量和肿瘤覆盖率差异一般小于 5%。
MC 算法应始终用于肺病变和大空腔附近病变的治疗计划，但对于组织异质性较小的治疗部位，更快的 EPL 算法足够。
