Int J Radiat Oncol Biol Phys. 1991 May 15;21(1):59-69. doi: 10.1016/0360-3016(91)90167-3.
The role of inhomogeneity corrections in three-dimensional (3-D) radiation treatment planning (RTP) was one of the issues addressed in a National Cancer Institute sponsored research contract. In eight selected disease sites, plans calculated with and without inhomogeneity corrections were compared. The one-dimensional Effective Path Length (EPL) method was used by all four participating institutions as the standard inhomogeneity correction method. However, the dose calculation algorithms were different, particularly in the treatment of blocking effects near the edge of the field. Evaluation tools such as dose-volume histogram, dose statistics, 3-D display of dose distributions and others were used in the comparison. Dose distributions were significantly altered by inhomogeneity corrections in the treatment plans for the lung tumors, and, to a lesser degree, for the breast and Hodgkin's diseases. Dose distributions for tumors of the head and neck region and in the abdomen were not significantly affected. The results should be regarded as particular to the EPL calculations. A treatment plan for the tumor of the larynx was calculated using both the EPL method and a 3-D scatter ray-trace Delta Volume method. For that particular site, inhomogeneity corrections were less important than correctly accounting for the effects of blockings on the scatter dose. Perturbations of electron transport were not accounted for by any of the methods used and not reflected in those sites where the effects were expected to be important. Fully quantitative evaluation of the role of inhomogeneity corrections in treatment planning requires an as yet unavailable all-encompassing accurate method of dose calculation.
非均匀性校正在三维（3-D）放射治疗计划（RTP）中的作用是美国国立癌症研究所资助的一项研究合同所涉及的问题之一。在八个选定的疾病部位，比较了进行非均匀性校正和未进行非均匀性校正时计算出的计划。所有四个参与机构均采用一维有效路径长度（EPL）方法作为标准的非均匀性校正方法。然而，剂量计算算法有所不同，尤其是在处理射野边缘附近的阻挡效应方面。在比较中使用了诸如剂量体积直方图、剂量统计、剂量分布的三维显示等评估工具。在肺癌治疗计划中，非均匀性校正显著改变了剂量分布，在乳腺癌和霍奇金病治疗计划中，剂量分布也有较小程度的改变。头颈部区域和腹部肿瘤的剂量分布未受到显著影响。这些结果应被视为特定于EPL计算的结果。使用EPL方法和三维散射射线追踪增量体积法计算了一例喉癌的治疗计划。对于该特定部位，非均匀性校正不如正确考虑阻挡对散射剂量的影响重要。所使用的任何方法均未考虑电子传输的扰动，在预期该效应重要的部位也未体现出来。要对非均匀性校正在治疗计划中的作用进行全面定量评估，需要一种目前尚不存在的全面准确的剂量计算方法。
