Muralidhar K R, Murthy Narayana P, Raju Alluri Krishnam, Sresty Nvnm
Department of Radiation Oncology, Indo-American Cancer Institute and Research Center, Road No:14, Banjara Hills, Hyderabad-500 034, Andhra Pradesh, Physics, Nagarjuna University, Nagarjuna Nagar, Guntur, Andhra Pradesh, India.
J Med Phys. 2009 Jan;34(1):12-22. doi: 10.4103/0971-6203.48716.
The aim of this study is to compare the dosimetry results that are obtained by using Convolution, Superposition and Fast Superposition algorithms in Conventional Radiotherapy, Three-Dimensional Conformal Radiotherapy (3D-CRT), and Intensity Modulated Radiotherapy (IMRT) for different sites, and to study the suitability of algorithms with respect to site and technique. For each of the Conventional, 3D-CRT, and IMRT techniques, four different sites, namely, Lung, Esophagus, Prostate, and Hypopharynx were analyzed. Treatment plans were created using 6MV Photon beam quality using the CMS XiO (Computerized Medical System, St.Louis, MO) treatment planning system. The maximum percentage of variation recorded between algorithms was 3.7% in case of Ca.Lung, for the IMRT Technique. Statistical analysis was performed by comparing the mean relative difference, Conformity Index, and Homogeneity Index for target structures. The fast superposition algorithm showed excellent results for lung and esophagus cases for all techniques. For the prostate, the superposition algorithm showed better results in all techniques. In the conventional case of the hypopharynx, the convolution algorithm was good. In case of Ca. Lung, Ca Prostate, Ca Esophagus, and Ca Hypopharynx, OARs got more doses with the superposition algorithm; this progressively decreased for fast superposition and convolution algorithms, respectively. According to this study the dosimetric results using different algorithms led to significant variation and therefore care had to be taken while evaluating treatment plans. The choice of a dose calculation algorithm may in certain cases even influence clinical results.
本研究的目的是比较在传统放疗、三维适形放疗（3D-CRT）和调强放疗（IMRT）中，针对不同部位使用卷积、叠加和快速叠加算法所获得的剂量学结果，并研究这些算法相对于部位和技术的适用性。对于传统放疗、3D-CRT和IMRT技术中的每一种，分析了四个不同的部位，即肺、食管、前列腺和下咽。使用CMS XiO（计算机医学系统，密苏里州圣路易斯）治疗计划系统，采用6MV光子束质量创建治疗计划。在IMRT技术中，对于肺癌病例，算法之间记录的最大变化百分比为3.7%。通过比较靶区结构的平均相对差异、适形指数和均匀性指数进行统计分析。快速叠加算法在所有技术的肺癌和食管癌病例中均显示出优异的结果。对于前列腺，叠加算法在所有技术中均显示出更好的结果。在下咽的传统病例中，卷积算法表现良好。在肺癌、前列腺癌、食管癌和下咽癌病例中，叠加算法使危及器官接受的剂量更多；快速叠加算法和卷积算法使危及器官接受的剂量则分别逐渐减少。根据这项研究，使用不同算法的剂量学结果导致了显著差异，因此在评估治疗计划时必须谨慎。在某些情况下，剂量计算算法的选择甚至可能影响临床结果。
