Opportunistic screening of osteoporosis using CT urography: comparison of diagnostic performance between contrast phases

Background Opportunistic screening of osteoporosis using computed tomography (CT) should be optimized according to CT protocols. However, to date, no study has evaluated the different contrast phases of CT urography in osteoporosis screening. Purpose To compare the diagnostic performance of different contrast phases of CT urography in opportunistic screening of osteoporosis. Material and Methods In this single-center retrospective study, 210 consecutive patients (181 men, 29 women; mean age = 72.0 ± 9.5 years) who underwent both CT urography and dual-energy X-ray absorptiometry (DXA) within 3 months in July to December 2020 were included. The attenuation value was measured at the center of the L1 vertebral body in the axial plane of the precontrast, corticomedullary, and excretory phases. The mean and standard deviation (SD) of attenuation values were calculated. The area under the receiver operating characteristic curve (AUC) in differentiating osteoporosis versus osteopenia/normal was measured in each phase, and non-parametric comparisons between precontrast and the other phases were performed. Results According to DXA results, 90, 90, and 30 patients were classified into the normal, osteopenia, and osteoporosis groups, respectively. The mean ± SD of attenuation values in the precontrast, corticomedullary, and excretory phases were 114.9 ± 47.8, 132.8 ± 49.3, and 126.2 ± 47.2 HU, respectively. A significant difference was observed between AUCs measured in the precontrast (0.804, 95% confidence interval [CI] = 0.717–0.890) and corticomedullary phases (0.760, 95% CI = 0.661–0.860) ( P = 0.003) and those between the precontrast and excretory phases (0.774, 95% CI = 0.678–0.869) ( P = 0.005). Conclusion The precontrast phase outperformed the other phases in the opportunistic screening of osteoporosis using CT urography.