Posterior elbow impingement (4DCT)

Case Discussion

Dynamic CT is a technique that has become available with the invention of wide detectors.  This technique combines the functional imaging of fluoroscopy with the 3D capabilities of CT. 16cm is the widest detector available and this allows dynamic volume scanning of any part of the body that lies within this range and thus makes it perfectly suited for 4D MSK, Cardiac, Angiographic, respiratory and Perfusion studies.

This examination required the assessment of bony anatomy during motion (flexion and extension of the elbow joint). During the 8 second acquisition, the patient slowly flexed and extended their elbow within the center of the CT gantry whilst gripping a 1kg sandbag to simulate the pain they experienced when exercising. 17 volumes (equating to 17 frames at ~2 fps) were acquired, each reconstructed into fine 0.5mm slices to allow for optimal isotropic resolution.

Data from this scan can then be used to generate 3D rendered images displayed dynamically or statically and fine MPRs can also be generated in any user-defined plane, these too can be dynamically assessed.

Due to the increase in time, kV and mA exposure factors are decreased to ensure doses are kept to a minimum. In this case, the effective dose was approximately 0.09mSv (roughly 4-5x a routine CT elbow dose).

The dynamic assessment of cases such as this can provide crucial information, previously not available, to further manage patient care and improve outcomes. It is likely, from the 4DCT findings, that this patient will undergo arthroscopic debridement to remove the fragments causing impingement.