Bone densitometry of excised vertebrae; anatomical relationships.

Bone mineral density (BMD) was determined in 32 excised vertebrae using three methods: (1) dual-energy quantitative computed tomography (QCT), (2) dual-photon absorptiometry (DPA) with 153-Gd in an anteriorposterior projection and (3) scanning slit X-ray absorptiometry (SSXA) in both AP and lateral projections. The QCT region-of-interest in the anterior vertebral body had a lower density than that of the total trabecular portion of the body, but was highly correlated to this larger region (r = 0.96; SEE = 8 mg/cm3). The anterior QCT region also correlated moderately with BMD from DPA (r = 0.77; SEE = 18 mg/cm3). Measurements of the vertebral body in lateral projection were less well correlated (r = 0.5-0.7) to QCT densities. Both the anterior QCT region (r = 0.81; SEE = 18 mg/cm3) and the BMD from DPA (r = 0.86; SEE = 16 mg/cm3) and the BMD from DPA (r = 0.86; SEE = 16 mg/cm3) were similarly predictive of density of the integral vertebral body. Differences among densitometric methods on the spine depend on the projection used and the region examined.