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 hone 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.