A technique is provided for automatically identifying regions of bone or other structural regions within a reconstructed CT volume data set. The technique identifies and labels regions within the data set and computes various statistics for the regions. A rule-based classifier processes the statistics to classify each region. Incidental connections between disparate regions are eliminated. A structure mask, such as a bone mask, is then constructed after exclusion of regions of interest, such as a vascular map. The structure mask may then be used to construct a volume rendering free of the structure, such as bone-free.