A new homogeneity index based on the statistical analysis of dose volume histogram

Abstract

The goal of this study was to develop a new dose-volume histogram (DVH) based homogeneity index for effectively evaluating the dose homogeneity of intensity modulated radiotherapy plans. The new index, called the sigma-index (or s-index) is defined as the standard deviation of the normalized differential DVH curve. In a study of 16 brain tumor patients at our institution, the s-index was found to vary from 0.80 to 3.15. Our results showed that the s-index provides a more reliable and accurate measure of dose homogeneity than that given by conventional methods. A guideline for evaluating dose homogeneity of treatment plans is discussed based on s-index and its relation to equivalent uniform dose.