The Value of Dual-energy CT Virtual Calcium Subtraction Technique in the Diagnosis of Fresh Sacrococcygeal Fractures in the “Sitting Position”

Purpose: The aim of this study was to evaluate the diagnostic performance of virtual non-calcium imaging using dual-energy computed tomography (CT) for acute sacrococcygeal injuries diagnosed by radiologists with varying levels of experience. Methods: A prospective study was employed and 29 patients presenting with acute coccygeal pain due to trauma between November 2021 and January 2024, involving a total of 174 vertebrae (145 sacral, 29 coccygeal), were enrolled. Both magnetic resonance imaging (MRI) and DECT data were acquired. Three radiologists with 1, 4, and 10 years of experience analyzed conventional CT and VNCa color-coded images, using MRI as the reference standard. Results: Following the application of VNCa imaging, the inter-rater agreement among the three radiologists significantly improved, with Kappa values increasing from 0.452, 0.615, and 0.735 to 0.775, 0.825, and 0.897, respectively. Diagnostic accuracy also notably increased to 92.5%, 94.3%, and 96.6% for the three radiologists, with no statistically significant differences observed among them. Quantitative analysis revealed an average VNCa CT value of (−84.2±20.3) HU for normal bone marrow and (−37.4±18.8) HU for bone marrow edema, showing a significant difference between the two. Using MRI as the reference standard, the area under the curve for distinguishing normal bone marrow from BME based on VNCa CT values was 0.962, with an optimal cutoff of −57.1 HU, yielding a sensitivity and specificity of 91.9％ and 90.2％, respectively. Conclusion: DECT VNCa imaging significantly enhances the diagnostic efficacy of radiologists with varying levels of experience in acute coccygeal injury assessment, particularly benefiting less-experienced physicians. VNCa CT values contribute substantially to diagnostic accuracy in this context.