Diagnostic accuracy of dual-energy CT virtual non-calcium imaging for detecting spinal metastases: a retrospective comparison with conventional CT.

Abstract

To compare the qualitative diagnostic performance of conventional computed tomography (CT) alone with that of dual-energy computed tomography (DECT) virtual non-calcium (VNCa) imaging for detecting spinal metastases, and evaluate the diagnostic utility of DECT-derived quantitative material parameters in this retrospective diagnostic accuracy study. Consecutive patients (August 2019-January 2024) underwent DECT at a single center. Two board-certified radiologists scored vertebrae on conventional CT and CT + VNCa using a 5-point scale (positive for scores 4-5). The reference standard was a consensus MRI within 3 months, supplemented by PET/CT and/or bone scintigraphy when available. We estimated sensitivity, specificity, and AUC with 95% CIs. Quantitative parameters including 70-keV CT attenuation (HU), water-calcium, water-hydroxyapatite, and Z_eff were compared between metastatic and normal vertebrae using the Wilcoxon rank-sum test. We included 117 patients, comprising 1416 vertebrae; 24.2% had metastases. For conventional CT, sensitivity was 0.70/0.71 (95% CI 0.664-0.738/0.677-0.750) and specificity, 0.97/0.97 (95% CI 0.939-1.000/0.935-1.000). CT + VNCa sensitivity increased to 0.94/0.93 (95% CI 0.906-0.980/0.890-0.964; p < 0.001) and AUC improved to 0.97/0.96 (both p < 0.001, specificity, 0.99/0.98). Quantitative analysis showed significantly higher values of water-calcium (1133.8 vs. 1007.6 mg/cm³), water-hydroxyapatite (991.5 vs. 971.0 mg/cm³), and effective atomic number (10.5 vs. 8.3) in osteoblastic metastases compared with those in normal vertebrae (all p < 0.05). CT + VNCa significantly improves the detection of spinal metastases compared with conventional CT alone. Quantitative parameters from material decomposition analysis provide additional diagnostic value.