Diagnostic accuracy of quantitative dual-energy CT-based bone mineral density assessment in comparison to Hounsfield unit measurements using dual x-ray absorptiometry as standard of reference.

PURPOSE

To assess the diagnostic accuracy of phantomless dual-energy computed tomography (DECT)-based volumetric material decomposition to assess bone mineral density (BMD) of the lumbar spine for the detection of osteoporosis compared to Hounsfield unit (HU) measurements with dual x-ray absorptiometry (DXA) as reference standard.

METHOD

A total of two hundred lumbar vertebrae in 53 patients (28 men, 25 women; mean age, 52 years, range, 23-87 years) who had undergone clinically-indicated third-generation dual-source DECT and DXA within 30 days were retrospectively analyzed. For volumetric BMD assessment, dedicated DECT postprocessing software using material decomposition was applied, which enables color-coded three-dimensional mapping of the trabecular BMD distribution. Manual HU measurements were performed by defining five trabecular regions of interest (ROI) per vertebra as suggested by literature. The DXA T-score served as standard of reference (osteoporosis: T < -2.5). Sensitivity, specificity and the area under the curve (AUC) were primary metrics of diagnostic accuracy.

RESULTS

An optimal patient-based DECT-derived BMD cut-off of 84 mg/cm³ yielded 96 % sensitivity (22/23) and 93 % specificity (28/30) for detecting osteoporosis, while an optimal CT attenuation cut-off of 139 HU showed 65 % sensitivity (15/23) and 93 % specificity (28/30) for the detection of osteoporosis. Overall patient-based AUC were 0.930 (volumetric DECT) and 0.790 (HU analysis) (p < .001). Pearson's product-moment correlation showed higher correlation between DECT BMD and DXA values (r=0.780) compared to HU and DXA values (r=0.528) (p < .001).

CONCLUSIONS

Phantomless volumetric DECT yielded significantly more accurate BMD assessment of the lumbar spine and superior diagnostic accuracy of osteoporosis compared to HU measurements.