Bert Christoph, Gemmel Alexander, Saito Nami, Rietzel Eike
Gesellschaft für Schwerionenforschung, Abt. Biophysik, Darmstadt, Germany.
Int J Radiat Oncol Biol Phys. 2009 Mar 15;73(4):1270-5. doi: 10.1016/j.ijrobp.2008.11.014.
To demonstrate mitigation of the interplay effects of scanned particle beams and residual target motion within a gating window by increased overlap of pencil beams.
Lateral overlap was increased by increasing the pencil beam widths or by decreasing the distance between the pencil beams (scan grid). Longitudinal overlap was increased by reducing the distance between iso-range slices. For scanned carbon ion beams, simulation studies were performed and validated experimentally to determine the required parameters for different residual motion characteristics. The dose distributions were characterized by the maximal local deviations representing local over- and underdosage.
For residual lateral motion, the local deviations were <5% for 2, 4, and 7 mm residual motion within the gating window for a 2-mm scan grid and pencil beams of 10, 14, and 18 mm full width at half maximum, respectively. Decreasing the iso-range slice distance from 3 mm to 1 mm effectively mitigated <or=10 mm water-equivalent range changes. Experimental data reproduced the simulation results.
In charged particle therapy with a scanned beam, interplay effects between gated beam delivery and residual target motion can be decreased effectively by increasing the overlap between pencil beams laterally, as well as longitudinally.
通过增加笔形束的重叠来减轻扫描粒子束与门控窗口内残余靶运动的相互作用效应。
通过增加笔形束宽度或减小笔形束之间的距离（扫描栅格）来增加横向重叠。通过减小等射程切片之间的距离来增加纵向重叠。对于扫描碳离子束，进行了模拟研究并通过实验验证，以确定不同残余运动特征所需的参数。剂量分布通过代表局部剂量过高和过低的最大局部偏差来表征。
对于残余横向运动，在门控窗口内有2、4和7毫米残余运动时，对于2毫米的扫描栅格和半高宽分别为10、14和18毫米的笔形束，局部偏差分别<5%。将等射程切片距离从3毫米减小到1毫米有效地减轻了≤10毫米水等效射程的变化。实验数据重现了模拟结果。
在扫描束的带电粒子治疗中，通过横向以及纵向增加笔形束之间的重叠，可以有效降低门控束输送与残余靶运动之间的相互作用效应。
