Assessment of Vertebral Bone Mineral Density Using Volumetric Quantitative CT

PURPOSE: The purpose of this work was to determine the precision and diagnostic efficacy of bone mineral density (BMD) measures based on volumetric quantitative CT (QCT) of the spine. METHOD: Volumetric CT scans of L1 and L2 (GE-9800Q; 80 kVp, 140 mAs, 3 mm slices) were acquired in a cohort of 62 osteoporotic women (mean age 70.4 years, T(DXA hip or spine) < -2.5), of whom 20 had vertebral fractures and 42 were nonfractured control subjects. An image analysis technique delineated trabecular, cortical, and integral regions in reference to a vertebra-fixed coordinate system. We computed precision values and fracture control differences for these new regions and for single-slice QCT and dual X-ray absorptiometry (DXA) measures synthesized from the volumetric data. RESULTS: Volumetric trabecular BMD showed higher precision (1.3%) than the synthesized single-slice measures (2.1-2.8%). Volumetric and single-slice trabecular BMD showed equivalent decrements between fractured and nonfractured subjects (17-19%), with integral BMD showing smaller and less significant differences (7-8%). CONCLUSION: Volumetric and single-slice QCT techniques are equivalent for vertebral fracture risk estimation, but volumetric techniques should be superior for monitoring therapy efficacy.