Dual Energy CT Virtual Non-Calcium Technique detects Post-Traumatic Bone Bruise of the Knee
SOMATOM Definition Dual Energy Scanning
Author: Gregor Pache, MD; Stefan Bulla, MD; Philipp Blanke MD and Mathias Langer Prof., MD Department of Radiology, University of Freiburg, Germany
A 49-year old male patient, with sustained high-energy knee trauma due to a skiing accident, was referred to our department. As the radiography result was equivocal a CT scan of the knee was performed to rule out a fracture.
CT revealed a small circumscribed fracture in the posteromedial tibia plateau (Fig.2). Additionally a Dual Energy CT (DECT) virtual non-calcium image (VNCa) (Fig.1b) was calculated (r value = 1.43) revealing bone marrow edema in the posteromedial and posterolateral tibia plateau. Although the edema appeared subtle on the gray-scale VNCa image the color-coded VNCa made the bone bruises obvious (Fig.1d). In light of these findings subsequently performed corresponding T2-weighted MR image confirmed both bone bruises (Fig.1c). Sagittal T2-weighted image revealed a complete anterior cruciate ligament tear (Fig.3).
The DECT virtual non-calcium technique subtracts calcium from cancellous bone, making post-traumatic bone bruises of the knee potentially detectable with CT. It is well known that the bone bruise pattern can predict associated soft tissue injuries. Typically, as seen in our case, bone bruises of the posterolateral tibial plateau are associated with anterior cruciate ligament tears. Although DECT will not replace MRI in the evaluation of knee trauma, DECT might be helpful to guide further diagnostic work-up. DECT might also constitute an option for those patients who have contraindications to MR imaging or for whom MR imaging is not available. Most importantly, as compared with the 8.71 mGy required for a single-energy CT scan, it was possible to obtain this extra information without additional radiation dose.
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