Kunieda E, Wada T, Ando Y, Tsukamoto N, Ito H, Kubo A
Department of Radiology, Keio University.
Nihon Igaku Hoshasen Gakkai Zasshi. 1995 Nov;55(14):980-6.
The aim of this study was to analyze the three-dimensional dose distributions produced by various techniques used in current radiosurgery treatments by means of dose-volume histograms (DVH). Off-center ratio and tissue-peak ratio from 6-MV X-rays through additional cylindrical collimators were measured in advance for dose calculation. The use of the diamond detector and beam profile film dosimetry in small fields were certified. The impact of arc number, arc geometry, and field size on the dose distribution in a spherical phantom was evaluated through the use of DVH. These were calculated for a) four arc irradiations with collimator sizes of 5, 10, 20 and 30 mm in diameter, and b) for single-plane rotation, four or eleven multiple non-coplanar convergent arcs, dynamic rotation and precessional converging radio-therapy (PCR) with a field size of 20 mm. PCR is performed in the sitting position with the patient seated on a special treatment chair, which is rotating continuously while the gantry moves from the top to the center of the chair rotation. Most of the differences between techniques were found in a range of less than 40% of the maximum dose. Multiple non-coplanar convergent arcs with four or eleven arcs and PCR performed similar result in DVH, while single-plane rotation revealed almost unacceptably shallow dose falloffs. The DVH of dynamic rotation was between that of single-plane rotation and the other three methods.
本研究的目的是通过剂量体积直方图（DVH）分析当前放射外科治疗中使用的各种技术所产生的三维剂量分布。预先测量了通过附加圆柱形准直器的6兆伏X射线的离轴比和组织峰值比，用于剂量计算。验证了在小射野中使用金刚石探测器和射野剖面胶片剂量测定法。通过使用DVH评估了弧数、弧几何形状和射野大小对球形模体中剂量分布的影响。这些是针对以下情况计算的：a）直径为5、10、20和30毫米的准直器尺寸的四弧照射，以及b）对于单平面旋转、四个或十一个多非共面汇聚弧、动态旋转和进动汇聚放射治疗（PCR），射野大小为20毫米。PCR在患者坐在特殊治疗椅上的坐姿下进行，当机架从椅子旋转的顶部移动到中心时，椅子持续旋转。技术之间的大多数差异在最大剂量的40%以下的范围内被发现。四个或十一个弧的多非共面汇聚弧和PCR在DVH中表现出相似的结果，而单平面旋转显示出几乎不可接受的浅剂量下降。动态旋转的DVH介于单平面旋转和其他三种方法之间。
