David F. Black MD, Presenter: Nothing to Disclose

Katrina Nesta Glazebrook MBChB, Abstract Co-Author: Nothing to Disclose

Tim Bongartz MD, Abstract Co-Author: Nothing to Disclose

Eric L. Matteson MD, Abstract Co-Author: Nothing to Disclose

Joel Garland Fletcher MD, Abstract Co-Author: Research grant, Siemens AG

Cynthia H. McCollough PhD, Abstract Co-Author: Research grant, Siemens AG

To evaluate the ability of dual-energy CT (DECT) to identify uric acid crystals in the extremities of patients with suspected gout.

Fifty-five clinically-indicated DECT scans in 54 patients (24 women, 30 men; mean age=62 y, range=29-89y) were retrospectively reviewed after IRB approval. Subjects were either clinically diagnosed with or suspected of having gout. A complete chart review of all participants was performed to document final clinical diagnosis. Dual-source CT (Siemens Definition DS), with its two, orthogonal X-ray tube/detector array pairs, was used to simultaneously acquire the 80 and 140 kV data sets used in the dual energy processing. Exploiting the kV-dependent nature of CT attenuation, a commercially-available, dual-energy material differentiation algorithm (Siemens syngo DE) was used to identify voxels comprised of uric acid, which were color coded as green, or calcium, which was color coded as purple, in order to identify which joints had urate crystal deposition and were thus likely suffering from gout. Twenty-eight of the 54 subjects underwent joint aspiration.

DECT scans were positive for uric acid crystal deposition in 26 of the 54 patients. A repeat DECT in one subject demonstrated a 90% decrease in the volume of uric acid burden as response to therapy. No false positive scans occurred when CT interpretation was compared with the final clinical diagnosis. Nine patients had insufficient joint fluid for aspiration. Of these, 2 had a positive DECT scan and were therefore considered to have gout based on clinical and imaging findings. No false negative scans following a positive fluid aspiration of the same joint were found.

DECT offers a non-invasive means to improve diagnostic accuracy in patients with suspected gout. By quantifying urate deposition, DECT may be used to monitor disease progression, assess response to therapy, or exclude gout as a diagnostic possibility.

Diagnosis of gout, which may be hindered by insufficient fluid aspiration, negative radiographs or normal urate levels, may be demonstrated quantitatively by imaging urate burden using DECT.

Black, D, Glazebrook, K, Bongartz, T, Matteson, E, Fletcher, J, McCollough, C, Dual Energy Computed Tomography (DECT) for the Evaluation of Gout.  Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL. http://archive.rsna.org/2009/8013047.html