Bortfeld T, Schlegel W, Rhein B
German Cancer Research Center, Department of Biophysics and Medical Radiation Physics, Heidelberg.
Med Phys. 1993 Mar-Apr;20(2 Pt 1):311-8. doi: 10.1118/1.597070.
A method for the calculation of three-dimensional dose distributions for high-energy photon beams is presented. The main features are (i) the calculation is fast enough to allow interactive three-dimensional treatment planning, and (ii) irregularly shaped or compensated fields, which are required to fit three-dimensional dose distributions to target volumes, are adequately taken into consideration. The method is based on the pencil beam convolution technique and shares its features concerning accuracy. A considerable gain in speed is achieved by decomposing the pencil beam kernel into three separated terms, thus reducing the required number of two-dimensional convolutions. The convolutions are performed in the frequency domain via the fast Hartley transform. Using these techniques, the calculation time for the convolutions is only about 8 s on a DEC VAX station 3100. This is one-fourth to one-third of the calculation time for the ray tracing through the three-dimensional CT data set, which has to be performed in any case. Results of the calculation are compared with measurements in a homogeneous phantom for 15 MV photons. Two irregular fields shaped with a multileaf collimator are considered. The deviations between measured and calculated absolute dose values are smaller than +/- 2%.
本文介绍了一种用于计算高能光子束三维剂量分布的方法。其主要特点为：（i）计算速度足够快，可实现交互式三维治疗计划；（ii）能充分考虑为使三维剂量分布与靶体积相匹配所需的不规则形状或补偿野。该方法基于笔形束卷积技术，在精度方面具有相同特点。通过将笔形束核分解为三个分离项，显著提高了速度，从而减少了所需的二维卷积次数。卷积在频域通过快速哈特利变换进行。使用这些技术，在DEC VAX 3100工作站上，卷积的计算时间仅约为8秒。这是在任何情况下都必须进行的通过三维CT数据集进行射线追踪计算时间的四分之一到三分之一。计算结果与在均匀模体中对15MV光子的测量结果进行了比较。考虑了两个用多叶准直器形成的不规则野。测量值与计算得到的绝对剂量值之间的偏差小于±2%。
