Phantomless assessment of volumetric bone mineral density using virtual non-contrast images from spectral detector computed tomography

Objective: To evaluate phantomless assessment of volumetric bone mineral density (vBMD) based on virtual non-contrast images of arterial (VNCa) and venous phase (VNCv) derived from spectral detector CT in comparison to true non-contrast (TNC) images and adjusted venous phase conventional images (CIV(adjusted)). Methods: 104 consecutive patients who underwent triphasic spectral detector CT between January 2018 and April 2019 were retrospectively included. TNC, VNCa, VNCv and venous phase images (CIV) were reconstructed. vBMD was obtained by two radiologists using an FDA/CE-cleared software. Average vBMD of the first three lumbar vertebrae was determined in each reconstruction; vBMD of CIV was adjusted for contrast enhancement as suggested earlier. Results: vBMD values obtained from CIV(adjusted) are comparable to vBMD values derived from TNC images (91.79 +/- 36.52 vs 90.16 +/- 41.71 mg/cm(3), p = 1.00); however, vBMD values derived from VNCa and VNCv (42.20 +/- 22.50 and 41.98 +/- 23.3 mg/cm(3) respectively) were significantly lower as compared to vBMD values from TNC and CIV(adjusted) (all p = 0.01). Conclusion: Spectral detector CT-derived virtual non-contrast images systematically underestimate vBMD and therefore should not be used without appropriate adjustments. Adjusted venous phase images provide reliable results and may be utilized for an opportunistic BMD screening in CT examinations. Advances in knowledge: Adjustments of venous phase images facilitate opportunistic assessment of vBMD, while spectral detector CT-derived VNC images systematically underestimate vBMD.