Dual Energy CT Virtual Non-Calcium Technique detects Post-Traumatic Bone Bruise of the Knee

SOMATOM Definition Dual Energy Scanning

Gregor Pache, MD; Stefan Bulla, MD; Philipp Blanke MD and Mathias Langer Prof., MD
Department of Radiology, University of Freiburg, Germany
 |  2011-05-17

History

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.


Diagnosis

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).


Comments

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.
 

Examination Protocol

Scanner SOMATOM Definition
Scan area Knee
Scan length 139 mm
Scan direction Cranio-Caudal
Scan time 34 s
Tube voltage (A/B) 140/80 kV
Tube current (A/B) 43/183 mAS
Dose modulation none
CTDIvol 8.69 mGy
DLP 131
Rotation time 1 s
Pitch 0.7
Slice collimation 20x0.6 mm
Slice width 2 mm
Spatial Resolution 0.33 mm
Reconstructed increment 1.0
Reconstruction kernel D30

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The drugs and doses mentioned herein are consistent with the approval labeling for uses and/or indications of the drug. The treating physician bears the sole responsibility for the diagnosis and treatment of patients, including drugs and doses prescribed in connection with such use. The Operating Instructions must always be strictly followed when operating the CT System. The source for the technical data is the corresponding data sheets. Results may vary.