Musculoskeletal imaging (dual-energy CT)

Last revised by Frank Gaillard on 15 May 2024

Dual-energy CT has a number of clinical applications in the assessment of the musculoskeletal system particularly in the realm of artefact reduction and material composition.

Similar to the concept of using virtual non-contrast imaging, virtual non-calcium images can be created using a three-material decomposition technique, to subtract the high attenuating trabecular bone and allow for assessment of bone marrow edema 1. Using this technique one can appreciate areas of increased attenuation within the bone marrow and hence can better appreciate occult fractures that lack or possess a limited cortical component. Although it should be noted that bone marrow edema is not pathognomonic for a subtle fracture. 

Conventional CT suffers from decreased image quality when faced with metal implants, metal in the CT scan will lead to artefacts such as beam hardening, excessive beam attenuation, photon starvation and overall degradation of the image. A method to overcome this is a virtual monochromatic energy spectrum reconstruction from a dual-energy acquisition, whereby a higher energy data set can be created (often around 105 and 133 kV 2) to decrease attenuation (increase penetration [virtually]) and overall decrease metal related artefact 2.  

Traditionally gout has been diagnosed via plain radiography and joint aspiration. Dual-energy CT has become a reliable, non-invasive technique to make this diagnosis 2,3. Taking into account the differing attenuation values of material, it is possible to detect and quantify urate deposits within CT scans. Furthermore, it is a useful rule post-processing technique to determine if a region of interest is, infact, tophaceous gout or an infection/mass. 

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