灵活调控笔形束参数的点扫描照射新方法研究

项目名称： 灵活调控笔形束参数的点扫描照射新方法研究

项目编号： No.11205217

项目类型： 青年科学基金项目

立项/批准年度： 2013

项目学科： 物理学II

项目作者： 刘新国

作者单位： 中国科学院近代物理研究所

项目金额： 30万元

中文摘要： 重离子治癌是放疗研究领域的前沿与热点。在重离子三维点扫描照射技术中，单能重离子笔形束尖锐的Bragg峰需通过微型脊形过滤器略微展宽成峰区剂量分布为高斯型的初级展宽峰。在照射靶区内各个扫描点的过程中，初级展宽峰的半高宽及束斑尺寸基本不变。为提高适形程度，这些参数需保持在较小的尺度上，这导致点扫描时需要减小扫描步长，在靶区设置庞大的扫描点数量。本项目旨在建立一种新的点扫描照射方法，即利用较小束斑的笔形束照射靶区的边缘区域，较大束斑的笔形束照射靶区的内部区域，从而减少靶区内扫描点数量，同时通过倾斜微型脊形过滤器不同角度来调控笔形束参数，获得纵向上初级展宽峰半高宽及横向上束斑大小灵活可变的笔形束。该方法具有缩短照射时间、减小扫描点的剂量偏差和靶区内剂量不均匀性等优势。本项目拟通过系统研究建立该新型点扫描照射方法，通过实验测量验证该方法的有效性及优势，这对进一步发挥重离子在放疗中的优势具有重要意义。

中文关键词： 重离子放射治疗；点扫描；束斑尺寸；剂量优化；微型脊形过滤器

英文摘要： Heavy-ion cancer therapy is the forefront and hotspot in the field of radiation therapy research. In the beam delivery technique of three-dimensional spot scanning, the sharp Bragg peak of a pencil-like pristine heavy-ion beam generally needs to be extended slightly with a mini ridge filter so as to form a primary mini spread-out Bragg peak (mini-SOBP), where a Gaussian-shaped dose distribution in the mini-SOBP is presented. The width (full-width at the half maximum) of the primary mini-SOBP and the beam spot size are basically unchanged during the process of spot scanning at the scan points in the target volume. To improve the conformity degree, these pramaters should be maintained at a smaller scale. In this way, it is necessary to reduce the scan step for the spot scanning so as to allocate enormous scan points in the target volume. To resolve this problem, we propose this research project aiming at establishing a novel method of spot scanning irradiation with flexibly adjustable pencil beam parameters. In the method, pencil beams with smaller beam spots are used to irradiate the peripheral scan points and with bigger ones to the internal scan points. Meanwhile, the pencil beam parameters are elaborately modulated by means of tilting different angles for the mini ridge filter and then variable pencil beams wi

英文关键词： heavy-ion radiotherapy；spot scanning；beam spot size；dose optimization；mini ridge filter