Distance deviation measure of contouring variability

Background and Purpose: Studies of contouring variation face a difficulty of meaningful comparison of contours. Although several measures of contouring disagreement were proposed, each of them has certain limitations that prevent its widespread use. The purpose of this work was to develop a novel measure that can provide meaningful results for a wide range of contour analysis studies. Materials and Methods: The proposed novel measure of contouring variability, i.e., a distance deviation measure, is based on distances from certain points on the analyzed image to closest points on all analyzed contours. By performing such analysis for all image points/voxels a new image is obtained, providing information of local contour agreement, given in absolute distance units (millimeters). To present such information rich results, three presentation methods are proposed: image representation for detailed topographic analysis, angular representation for compact topographic analysis, and an overall scalar estimate for quick assessment of the level of contour disagreement. Results: Distance deviation method is demonstrated on a multi observer contouring example with complex contour shapes, i.e., with presence of holes or excrescences. The results are presented using the three proposed methods. Conclusions: The proposed method can detect and measure contour variation irrespective of contour complexity and number of contour segments, while the obtained results are easy interpret. It can be used in various situations, regarding the presence of reference contour or multiple test contours.