Dual-energy CT virtual non-contrast technology in the diagnosis of osteoporosis: a preliminary study

Objective To investigate the diagnostic value of dual-energy CT virtual non-contrast (VNC) technology for osteoporosis(OP). Methods Dual-energy CT images of 50 patients with lumbar traumas were collected prospectively. Patients who suffer from vertebral bodies fractures between lumbar 1 to 4, have internal metal fixations or underwent percutaneous vertebroplasty, or presented tumors or compromised bone metabolism induced by diseases or medications were excluded. The scanning range was from the upper edge of the 12th thoracic vertebral body to the lower edge of the first sacral vertebral body. The voltages of tubes A and B were 90 kV and Sn 150 kV, and the reference tubes currents were 220 mAs and 138 mAs. Image reconstruction was performed using Advanced Modeled Iterative Reconstruction (ADMIRE) with iterative strength of 3 and convolution kernel of Qr 40. The default parameters of the virtual non-contrast software were corrected by the standard recommended by the Bone Marrow software of the post-processing platform Syngo.via, and the CT value of calcium (contrast media CM), the CT value of mixed energy images (regular CT value, rCT), the calcium density (CaD) and the fat fraction (Fat) were measured. The bone mineral density (BMD) and T score of each lumbar vertebra from lumbar 1 to lumbar 4 were measured by dual energy X-ray absorptiometry (DXA). With T score less than or equal to the 2.5 standard deviation as the gold standard for the diagnosis of OP, correlations between CT measurements and vertebral BMDs were analyzed using Pearson correlation analysis and linear regression and the diagnostic values of different CT measurements for OP were compared using receiver operating characteristic curve. Results Each of the vertebral bodies was analyzed as a single unit. Fifty of them were osteoporotic and the rest 116 were non-osteoporotic. Except for Fat, the CT measurement parameters of the osteoporotic vertebral bodies were lower than those of the ones without osteoporosis, and the difference was statistically significant (P<0.01). CM, rCT and CaD were significantly correlated with BMD (r were 0.75, 0.65, 0.71, all P<0.01) and there was a linear relationship (F were 209.91, 120.24, 167.69, all P<0.01).Meanwhile, CM, rCT, CaD and T score were also significantly correlated (r were 0.74, 0.65, 0.70, all P<0.01) with a linear relationship (F were 195.04, 120.29, 156.37, all P<0.01). CM, rCT and CaD had relatively high concordance rates against the OP diagnosis gold standard (respectively 81.9%, 62.2% and 81.9%). CM and CaD had higher concordance rates than rCT, the difference being statistically significant (P<0.01), and by the CM less than 239.5 HU or CaD less than 10.9 mg/cm3 standard, their sensitivities of diagnosing osteoporosis were respectively 86.0% and 84.0%, while the specificities, 80.2% and 81.0%. After superimposing CM and CaD, the results did not improve the diagnosis efficiency of OP (pre-superposition diagnostic performance better than post-superposition (P<0.05). Conclusion The VNC technology on DECT can do both vertebral fractures diagnosis and osteoporosis assessment at the same time, thus optimizing the clinical examination process. Key words: Osteoporosis; Lumbar vertebrae; Dual-energy computed tomography; Virtual non-contrast technology