Improved assessment of multiple sclerosis lesion segmentation agreement via detection and outline error estimates

DE, OE and Similarity Index (SI) values were calculated for two raters tested on a set of 17 fluid-attenuated inversion-recovery (FLAIR) images of patients with MS. DE, OE, and SI values were tested for dependence with mean total area (MTA) of the raters' Region of Interests (ROIs).When correlated with MTA, neither DE (ρ？=？.056, p=.83) nor the ratio of OE to MTA (ρ？=？.23, p=.37), referred to as Outline Error Rate (OER), exhibited significant correlation. In contrast, SI is found to be strongly correlated with MTA (ρ？=？.75, p？<？.001). Furthermore, DE and OER values can be used to model the variation in SI with MTA.The DE and OER indices are proposed as a better method than SI for comparing rater agreement of ROIs, which also provide specific information for raters to improve their agreement.