Prendergast Brendan M, Popple Richard A, Clark Grant M, Spencer Sharon A, Guthrie Bart, Markert James, Fiveash John B
Department of Radiation Oncology, University of Alabama at Birmingham.
Division of Neurosurgery, University of Alabama at Birmingham.
J Radiosurg SBRT. 2011;1(2):117-122.
Linear accelerator (linac) based CNS stereotactic radiosurgery (SRS) requires significant time resources. We hypothesized that CNS SRS using a flattening filter free (FFF) linac would reduce treatment time and improve clinical efficiency. A FFF linac was recently commissioned for CNS radiosurgery at the University of Alabama at Birmingham. The efficiency of this linac for CNS SRS was retrospectively reviewed. Beam on time (BOT), time in room (TIR), and clinical dose rate (CDR) were calculated using an integrated treatment planning, record, and verification software platform and are proposed as surrogates for treatment efficiency. Twenty-seven eligible CNS SRS cases consisting of 1-5 fractions of 5 Gy or more per fraction were reviewed. Mean BOT was 1:21 (minutes:seconds; range: 00:36-2:52) and mean TIR was 10:42 (minutes:seconds; range: 6:05-22:56). The mean CDR was 1820 MU/ min (range: 872-2396). On regression analysis the number of alignment images, treatment arcs, targets, monitor units, and presence of intra-fraction imaging were factors significantly (p < 0.05) associated with prolonged TIR. Use of FFF mode in CNS SRS more than triples the CDR and results in shortened BOT and TIR compared to treatment at conventional dose rates. Reduction in clinical treatment times may translate to better target localization due to reduced opportunity for intrafraction motion. Linac-based CNS SRS can be completed in a normal time slot with a high output FFF linac.
基于直线加速器（linac）的中枢神经系统立体定向放射外科手术（SRS）需要大量时间资源。我们假设使用无 flattening 滤波器（FFF）的直线加速器进行中枢神经系统 SRS 将减少治疗时间并提高临床效率。最近，阿拉巴马大学伯明翰分校启用了一台 FFF 直线加速器用于中枢神经系统放射外科手术。对该直线加速器用于中枢神经系统 SRS 的效率进行了回顾性评估。使用集成治疗计划、记录和验证软件平台计算束流开启时间（BOT）、在室时间（TIR）和临床剂量率（CDR），并将其作为治疗效率的替代指标。回顾了 27 例符合条件的中枢神经系统 SRS 病例，每例包含 1 - 5 次分割，每次分割剂量为 5 Gy 或更高。平均 BOT 为 1:21（分钟:秒；范围：00:36 - 2:52），平均 TIR 为 10:42（分钟:秒；范围：6:05 - 22:56）。平均 CDR 为 1820 MU/分钟（范围：872 - 2396）。回归分析显示，校准图像数量、治疗弧、靶区、监测单位以及分割内成像的存在是与 TIR 延长显著相关（p < 0.05）的因素。与传统剂量率治疗相比，在中枢神经系统 SRS 中使用 FFF 模式可使 CDR 增加两倍多，并导致 BOT 和 TIR 缩短。临床治疗时间的减少可能由于分割内运动机会减少而转化为更好的靶区定位。基于直线加速器的中枢神经系统 SRS 可以在正常时间段内使用高输出的 FFF 直线加速器完成。
