Dose Reduction Does Not Affect Detection of Bone Marrow Lesions with Dual-energy CT Virtual Noncalcium Technique

Rationale and Objectives: The aim of this study was to evaluate if a dose-reduced, dose-neutral dual-energy computed tomographic (CT) virtual noncalcium technique can equally detect posttraumatic bone marrow lesions (BMLs) of the knee. Materials and Methods: Fifty patients underwent DE CT imaging with either a standard dose (group A) or a dose equal to that of a single-energy CT scan (group B) (28% dose reduction) and magnetic resonance imaging for knee trauma workup. Calcium was virtually subtracted from the images. Two radiologists rated the presence of abnormal soft tissue-like attenuation in the bone marrow in a total of 12 femoral and tibial regions and performed Hounsfield unit measurements thereafter. Receiver-operating characteristic curve analysis was used for four-point rating scores and Hounsfield unit measurements. Fractures were classified. Results: Magnetic resonance imaging depicted 170 BMLs (35 femoral, 135 tibial). Mean age, number of fractures, attenuation values and number of regions with BMLs were not significantly different between the groups. Visual rating revealed overall areas under the curves of 0.983 and 0.979 for observers 1 and 2, respectively. Visual judgment was superior to attenuation measurements for femoral regions regardless of the dose applied. Analysis of variance of all CT values revealed a significant influence for the presence of edema (P<.001) but no differences for the radiation dose used (P=.424). Interobserver agreement was excellent (kappa = 0.944). Conclusions: Dose reduction does not affect the detectability of posttraumatic BMLs with a dual-energy CT virtual noncalcium technique, thereby providing potential additional information compared with single-energy CT imaging without additional radiation dose.