  In this paper a new technique is presented that extracts the geometry of
lumbar vertebral bodies from spiral CT scans. Our new multi-step segmentation
approach yields highly accurate and precise measurement of the bone mineral
density (BMD) in different volumes of interest which are defined relative to a
local anatomical coordinate systems. The approach also enables the analysis of
the geometry of the relevant vertebrae. Intra- and inter operator precision for
segmentation, BMD measurement and position of the coordinate system are below
1.5% in patient data, accuracy errors are below 1.5% for BMD and below 4% for
volume in phantom data. The long-term goal of the approach is to improve
fracture prediction in osteoporosis.
