Quantifying the bone marrow composition of the healthy adult wrist with dual-energy CT.

PURPOSE: Purpose of this study was to investigate Dual-energy CT (DECT) derived virtual non-calcium (VNCa) values for absolute quantification of the bone marrow composition in the wrist. MATERIALS AND METHODS: We prospectively included consecutive adult participants and examined their wrists with DECT. Ranges of VNCa and calcium values were measured in the carpal bones, radius and ulna using a semi-automatic method. Bones with bone marrow edema, assessed by two blinded radiologists, were excluded. After determining optimum parameters for the three-material decomposition, the influence of calcium values, age and sex on VNCa values was assessed using multiple linear regression. RESULTS: 41 participants (Median age 53 years, range 20 years - 88 years, 51 % men) were enrolled and 399 bones assessed. At participant level mean VNCa values were -143 HU (SD 14 HU) using the current parameters for three-material decomposition and -104HU (SD 11 HU) with optimized parameters. There was a strong and significant influence of calcium values on VNCa values with the current parameters (p < 0.001, -0.137 HU[VNCa] / HU[Calcium]). With optimized parameters the calcium values and sex were not statistically significant predictors of VNCa values. Age was a significant, but clinically negligible, predictor (p = 0.03, -0.225 HU / year). CONCLUSIONS: After optimizing three-material decomposition parameters, calcium values, age and sex do not substantially influence virtual non-calcium values, and DECT may therefore be used for absolute quantification of the bone marrow composition - alleviating the need for reference bones or groups.

Dual-Energy CT for Suspected Radiographically Negative Wrist Fractures: A Prospective Diagnostic Test Accuracy Study.

Background Patients with wrist trauma and negative findings on radiographs often undergo additional MRI examinations to assess for radiographically occult fractures. Dual-energy CT may be more readily available than MRI in some settings. Purpose To evaluate the diagnostic test accuracy of dual-energy CT in helping detect bone marrow edema and fracture in participants with wrist trauma and clinical suspicion of a wrist fracture but with negative findings on radiographs. Materials and Methods Adults were prospectively enrolled between January 2018 and November 2018. Wrists were examined with dual-energy CT and MRI, and images were read by four readers who were blinded to clinical information. The presence of bone marrow edema and fracture was rated per bone. The reference standard for bone marrow edema was the combined reading of MRI scans. The reference standard for fracture was a combined reading of MRI and dual-energy CT scans. A fifth radiologist arbitrated results in case of discrepancies. Diagnostic test accuracy was calculated per reader and for readers combined using exact binomial tests. Results Forty-six participants (mean age, 47 years ± 19 [standard deviation]; 24 men [52%]) were enrolled, and 750 bones (50 wrists) were assessed. Dual-energy CT had an average sensitivity of 94% (95% confidence interval [CI]: 80%, 99%; 31 of 33 wrists) and specificity of 65% (95% CI: 38%, 86%; 11 of 17 wrists) in the detection of wrists with bone marrow edema and a sensitivity of 69% (95% CI: 55%, 81%; 36 of 52 bones) and a specificity of 98% (95% CI: 97%, 99%; 682 of 696 bones) in the detection of edema in individual bones. MRI had a sensitivity of 80% (95% CI: 63%, 91%; 28 of 35 wrists) and a specificity of 93% (95% CI: 68%, 100%; 14 of 15 wrists) in helping detect wrists with fractures. Dual-energy CT had a sensitivity of 91% (95% CI: 77%, 98%; 32 of 35 wrists) and a specificity of 87% (95% CI: 60%, 98%; 53 of 60 wrists) in helping detect wrists with fractures. McNemar tests showed no significant differences between MRI and dual-energy CT (P = .07 to >.99) for all readers. Conclusion Dual-energy CT had a high sensitivity and a moderate specificity in the detection of bone marrow edema of the wrist. Dual-energy CT had high sensitivity and specificity in depicting fractures of the wrist in patients with suspected wrist fractures and negative findings on radiographs. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Fukuda in this issue.