Department of Radiation Physics, Unit 94, The University of Texas M D Anderson Cancer Center, 1515 Holcombe Blvd, Houston, TX 77030, USA.
Phys Med Biol. 2010 Dec 21;55(24):7633-47. doi: 10.1088/0031-9155/55/24/016. Epub 2010 Nov 26.
A synchrotron-based proton therapy system operates in a low repetition rate pulsed beam delivery mode. Unlike cyclotron-based beam delivery, there is no guarantee that a synchrotron beam can be delivered effectively or precisely under the respiratory-gated mode. To evaluate the performance of gated synchrotron treatment, we simulated proton beam delivery in the synchrotron-based respiratory-gated mode using realistic patient breathing signals. Parameters used in the simulation were respiratory motion traces (70 traces from 24 patients), respiratory gate levels (10%, 20% and 30% duty cycles at the exhalation phase) and synchrotron magnet excitation cycles (T(cyc)) (fixed T(cyc) mode: 2.7, 3.0-6.0 s and each patient breathing cycle, and variable T(cyc) mode). The simulations were computed according to the breathing trace in which the proton beams were delivered. In the shorter fixed T(cyc) (<4 s), most of the proton beams were delivered uniformly to the target during the entire expiration phase of the respiratory cycle. In the longer fixed T(cyc) (>4 s) and the variable T(cyc) mode, the proton beams were not consistently delivered during the end-expiration phase of the respiratory cycle. However we found that the longer and variable T(cyc) operation modes delivered proton beams more precisely during irregular breathing.
基于同步加速器的质子治疗系统以低重复率脉冲束输送模式运行。与基于回旋加速器的束输送不同，不能保证在呼吸门控模式下同步加速器束能够有效地或精确地输送。为了评估门控同步加速器治疗的性能，我们使用真实患者呼吸信号模拟了基于同步加速器的呼吸门控模式下的质子束输送。模拟中使用的参数包括呼吸运动轨迹（24 名患者中的 70 条轨迹）、呼吸门控水平（呼气阶段的 10%、20%和 30%占空比）和同步加速器磁体激励周期（T(cyc)）（固定 T(cyc)模式：2.7、3.0-6.0 s 和每个患者呼吸周期，以及可变 T(cyc)模式）。模拟根据质子束输送的呼吸轨迹进行计算。在较短的固定 T(cyc)（<4 s）中，大多数质子束在整个呼吸周期的呼气阶段均匀地输送到目标。在较长的固定 T(cyc)（>4 s）和可变 T(cyc)模式下，质子束在呼吸周期的呼气末期不能始终输送。然而，我们发现较长和可变的 T(cyc)操作模式在不规则呼吸期间更精确地输送质子束。
