A method includes generating, based on a distance map, a signal indicative of a quantification of a characteristic of a lumen of a tubular structure of interest over a pre-determined extent of the tubular structure of interest represented in volumetric imaging data. A system includes a quantifying component (216) that generates, based on a distance map, a signal indicative of a quantification of characteristic of a lumen of a tubular structure of interest over a pre-determined extent of the tubular structure of interest represented in volumetric imaging data. A method includes identifying voxels of 3D segmented imaging data that represent tubular structure of interest, determining distances between the identified voxels and nearest voxels corresponding to other structure in a plurality of 2D slices of the segment imaging data, representing the voxels with intensity values that are proportional to the distances, and generating a signal indicative of a 3D distance map based on the intensity values.