Traumatic bone marrow edema of the calcaneus: Evaluation of color-coded virtual non-calcium dual-energy CT in a multi-reader diagnostic accuracy study

Purpose: To investigate the diagnostic accuracy of dual-energy computed tomography (CT) virtual non-calcium (VNCa) reconstructions for the depiction of traumatic bone marrow edema of the calcaneus. Method: Data from 62 patients (33 women, 29 men; mean age: 41 years, range: 19-84 years) with acute tarsal trauma who had undergone third-generation dual-source dual-energy CT and 3-T magnetic resonance imaging (MRI) within seven days between January 2017 and July 2018 were retrospectively analyzed. Five radiologists, blinded to clinical and MRI information, independently assessed conventional grayscale dual-energy CT series for the presence of fractures; after at least eight weeks, readers re-evaluated all cases using color-coded VNCa reconstructions for the presence of bone marrow edema. Quantitative analysis of CT numbers on VNCa reconstructions was performed by a sixth radiologist. Two additional experienced radiologists, blinded to clinical and CT information, assessed MRI series in consensus to define the reference standard. Sensitivity, specificity and the area under the curve (AUC) were the primary indices for diagnostic accuracy. Results: MRI revealed 62 areas with bone marrow edema in 39 patients. In the qualitative analysis, VNCa showed high overall sensitivity (286/310 [92%]) and specificity (899/930 [97%]) for the depiction of bone marrow edema. A cut-off value of -53 Hounsfield units (HU) provided a sensitivity of 82% (51/62) and specificity of 95% (176/186]) for differentiating bone marrow edema. The overall AUC was 0.98. Conclusions: In both quantitative and qualitative analyses, dual-energy CT VNCa reconstructions show excellent diagnostic accuracy for the visualization of traumatic calcaneal bone marrow edema compared to MRI.