Effect of bone distribution on vertebral strength: assessment with patient-specific nonlinear finite element analysis.

Three-dimensional quantitative computed tomographic (QCT) studies of the lumbar spine were extended with finite element analysis (FEA) to include bone distribution in assessment of vertebral body strength. Fifty-nine FEA models were created from data from 43 patients, 28 with no evidence of osteoporosis and 15 with previous vertebral fractures. Simulated loads were applied to the vertebral models to estimate vertebral strength. Yield strength in the models from patients with osteoporosis was 0.22-1.05 MPa (average, 0.57 MPa +/- 0.26 [mean +/- standard deviation]), compared with 0.80-2.79 MPa (1.46 +/- 0.52, P less than .001) in patients with normal bone. Yield strength of vertebrae in patients with osteoporosis uniformly fell below approximately 1.0 MPa, with minimal overlap between patients with osteoporosis and those with normal bone compared with the overlap in bone mineral content and trabecular mineral density. Reproducibility of the FEA technique was 12.1% in a subgroup of patients with normal bone. A constant relationship between cortical and trabecular contributions was observed in patients with osteoporosis but not in control patients.

Osteoporosis: assessment by quantitative computed tomography.

The results presented in this article indicate that quantitative computed tomography provides a reliable means of evaluating and monitoring the many forms of osteoporosis and its various treatments. The greatest advantages of spinal QCT for noninvasive bone mineral measurement are its high precision, the high sensitivity of the vertebral spongiosa measurement site, and the potential for widespread application.

Assessment of metabolic bone diseases by quantitative computed tomography.

Advances in the radiologic sciences have permitted the development of numerous noninvasive techniques for measuring the mineral content of bone, with varying degrees of precision, accuracy, and sensitivity. The techniques of standard radiography, radiogrammetry, photodensitometry, Compton scattering, neutron activation analysis, single and dual photon absorptiometry, and quantitative computed tomography (QCT) are described and reviewed in depth. Results from previous cross-sectional and longitudinal QCT investigations are given. They then describe a current investigation in which they studied 269 subjects, including 173 normal women, 34 patients with hyperparathyroidism, 24 patients with steroid-induced osteoporosis, and 38 men with idiopathic osteoporosis. Spinal quantitative computed tomography, radiogrammetry, and single photon absorptiometry were performed, and a spinal fracture index was calculated on all patients. The authors found a disproportionate loss of spinal trabecular mineral compared to appendicular mineral in the men with idiopathic osteoporosis and the patients with steroid-induced osteoporosis. They observed roughly equivalent mineral loss in both the appendicular and axial regions in the hyperparathyroid patients. The appendicular cortical measurements correlated moderately well with each other but less well with spinal trabecular QCT. The spinal fracture index correlated well with QCT and less well with the appendicular measurements. Knowledge of appendicular cortical mineral status is important in its own right but is not a valid predictor of axial trabecular mineral status, which may be disproportionately decreased in certain diseases. Quantitative CT provides a reliable means of assessing the latter region of the skeleton, correlates well with the spinal fracture index (a semiquantitative measurement of end-organ failure), and offers the clinician a sensitive means of following the effects of therapy.

Quantitative computed tomography for spinal mineral assessment: current status.

Quantitative CT (QCT) is an established method for the noninvasive assessment of bone mineral content in the vertebral spongiosum and other anatomic locations. The potential strengths of QCT relative to 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 cortical bone. The extraction of this quantitative information from the CT image, however, requires sophisticated calibration and positioning techniques and careful technical monitoring.

How accurate are computed tomographic scans in assessment of changes in tumor size?

The computed tomographic scan plays an integral part in the diagnosis and management of tumors; however, its potential has not yet been fully exploited. With a computer-assisted volume determination method, the reproducibility of derived volume calculations was assessed, and radiologists' standard interpretations of interval change on serial scans were compared with the investigators' calculations of tumor volume change. Interobserver reproducibility of tumor volume calculations of the mean of two repeated volume determinations was satisfactory (mean of 3 percent, median of 1 percent). There were 29 comparisons (47 scans of 19 patients with liver tumors) of computed tumor changes with the radiologists' computed tomographic reports of consecutive scans. In only 41 percent (12 of 29) of the cases did the radiologists' interpretations and the computer-assisted volume determinations agree. It is concluded that objective computer-assisted volume determination provides a potentially more sensitive assessment of tumor change and that such precise, specific, reproducible determination of tumor volume should further clinical research and improve patient care.