Quantitative Computed Tomography in Assessment of Osteoporosis

Computed tomography (CT) has been widely investigated and applied in recent years as a means for noninvasive quantitative bone mineral determination. The usefulness of computed tomography for measurement of bone mineral lies in its ability to provide a quantitative image and, thereby, measure trabecular, cortical, or integral bone, centrally or peripherally. For measuring the spine, the potential advantages of quantitative computed tomography (QCT) over dual-photon absorptiometry (DPA) are its capability for precise three-dimensional anatomic localization providing a direct density measurement, and its capability for spatial separation of highly responsive cancellous bone from less responsive compact bone. Currently, QCT vertebral mineral determination has been implemented at over 800 sites encompassing a wide geographic distribution and a wide array of commercial scanners. With a world-wide distribution of approximately 8,000 advanced CT body scanners, the capability now exists for widespread application of vertebral bone mineral determination by quantitative computed tomography. These QCT techniques for vertebral mineral determination have been used to study skeletal changes in osteoporosis and other metabolic bone diseases. Longitudinal and cross-sectional bone mass measurements have been obtained at the University of California at San Francisco (UCSF) in over 3,000 patients seen clinically or on research protocols. The results presented here illustrate the use of QCT spinal mineral measurement in the delineation of normal age-related bone loss, in the evaluation of estrogen effects on bone, in the assessment of fracture threshold and risk, and in the study of the effects of various exercise regimens on bone mineral and the determination of relationships to other techniques of bone mineral measurement. The laboratory and clinical results presented herein indicate that QCT provides a reliable means to evaluate and monitor the many forms of osteoporosis and the various interventions aimed at ameliorating this condition. The greatest advantages of spinal QCT for noninvasive bone mineral measurement lie in the high precision of the technique, the high sensitivity of the vertebral trabecular measurement site, and the potential for widespread application.