Rathee S, McClean B A, Field C
Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada.
Med Phys. 1993 Sep-Oct;20(5):1343-51. doi: 10.1118/1.596984.
This paper describes the errors in rebinning photon dose point spread functions and pencil beam kernels (PBKs) from cylindrical to Cartesian coordinates. An area overlap method, which assumes that the fractional energy deposited per unit volume remains constant within cylindrical voxels, provides large deviations (up to 20%) in rebinned Cartesian voxels while conserving the total energy. A modified area overlap method is presented that allows the fractional energy deposited per unit volume within cylindrical voxels to vary according to an interpolating function. This method rebins the kernels accurately in each Cartesian voxel while conserving the total energy. The dose distributions were computed for a partially blocked beam of uniform fluence using the Cartesian coordinate kernel and the kernels rebinned by both methods. The kernel rebinned by the modified area overlap method provided errors less than 1.7%, while the kernel rebinned by the area overlap method gave errors up to 4.4%.
本文描述了将光子剂量点扩展函数和笔形束核（PBK）从柱坐标重新划分到笛卡尔坐标时的误差。一种面积重叠方法，该方法假定在柱形体素内每单位体积沉积的分数能量保持恒定，在重新划分的笛卡尔体素中会产生较大偏差（高达20%），同时总能量守恒。提出了一种改进的面积重叠方法，该方法允许柱形体素内每单位体积沉积的分数能量根据插值函数变化。该方法在每个笛卡尔体素中准确地重新划分核，同时总能量守恒。使用笛卡尔坐标核和两种方法重新划分的核计算了均匀注量的部分阻挡束的剂量分布。通过改进的面积重叠方法重新划分的核产生的误差小于1.7%，而通过面积重叠方法重新划分的核产生的误差高达4.4%。
