Department of Physics, The George Washington University, Washington, DC 20052, USA.
Phys Med Biol. 2010 Feb 7;55(3):747-59. doi: 10.1088/0031-9155/55/3/014. Epub 2010 Jan 14.
Dose-rate-regulated tracking (DRRT) is a novel tumor-tracking technique based on a preprogrammed multileaf-collimator (MLC) sequence and dose-rate modulation. We have performed a parametric study on how limitations of the DRRT system and breathing irregularities affect the tracking error and the duty cycle of DRRT. The time delay and the allowed dose-rate increment (continuous-, discrete-increment or beam switching) were used as two parameters for the DRRT system limitation. The breathing irregularity was quantified in terms of three variables, namely, breathing period variation, variation of peak-to-peak amplitude and baseline drift. DRRT treatments were simulated using 2126 breathing cycles obtained from 24 lung-cancer patients. Tracking errors and duty cycles from all 24 patients were combined to evaluate their dependence on each parameter or variable. The tracking error and the duty cycle show a modest difference among the three dose-rate-increment cases. Time delay, breathing peak-to-peak variation and baseline drift are the main factors affecting tracking error. The duty cycle is affected mostly by the allowed dose-rate increment, peak-to-peak variation and baseline drift.
剂量率调控跟踪（DRRT）是一种基于预编程多叶准直器（MLC）序列和剂量率调制的新型肿瘤跟踪技术。我们对 DRRT 系统的限制和呼吸不规则性如何影响跟踪误差和 DRRT 的占空比进行了参数研究。时间延迟和允许的剂量率增量（连续、离散增量或束切换）被用作 DRRT 系统限制的两个参数。呼吸不规则性用三个变量来量化，即呼吸周期变化、峰峰值幅度变化和基线漂移。使用从 24 位肺癌患者中获得的 2126 个呼吸周期来模拟 DRRT 治疗。将来自所有 24 位患者的跟踪误差和占空比结合起来，以评估它们对每个参数或变量的依赖性。在三种剂量率增量情况下，跟踪误差和占空比之间存在适度差异。时间延迟、呼吸峰峰值变化和基线漂移是影响跟踪误差的主要因素。占空比主要受允许的剂量率增量、峰峰值变化和基线漂移的影响。
