Diagnostic value of dual-energy CT in differential diagnosis of osteoblastic metastasis and bone islands

Background To evaluate the performance of multiple quantitative parameters derived from three-phase dual-energy CT (DECT) in the differential diagnosis of osteoblastic metastasis (OBM) from bone islands (BI). Methods In this retrospective study, patients who underwent contrast-enhanced CT scan and were diagnosed with OBM or BI between April 2019 to December 2022 were included. Multiple quantitative parameters including CT attenuation (CTa), iodine concentration (IC), slope of the spectral Hounsfield unit curve (λ _Hu ), electron density (Rho), effective atomic number (Z _eff ) (all derived from three-phase DECT scan) and virtual non-calcium (VNCa) (derived from pre-contrast DECT scan), then compared between OBM and BI groups. The diagnostic performance was evaluated using receiver operator characteristic (ROC) curve. Results A total of 125 patients with malignant tumors were enrolled, including 51 patients with 124 OBM and 74 patients with 119 BI. VNCa of OBM was significantly higher than BI, whereas other DECT quantitative parameters of OBM were significantly lower than BI (all P  < 0.001). The parameters extracted from different phases were highly correlated with each other both in the OBM group (r, 0.637–0.862) and BI group (r, 0.490–0.903), except VNCa. The three-phase DECT quantitative parameters performed well in identifying both OBM and BI; in particular, VNCa achieved an excellent and stable diagnostic performance in both the training group and testing group with AUC 1.00, sensitivity 100.0%, specificity 100.0%, and accuracy 100.0% ( P  < 0.001). Conclusions DECT derived multiple quantitative parameters that demonstrated excellent performance in differentiating OBM from BI. Notably, VNCa could completely distinguish between the OBM and BI.