Case: Reliable Detection and Diagnoses of Gout Using Dual Energy Acquisition Technique

Case history
Usually, rheumatologic diseases are of many kinds, numerous and varied, making a quick diagnosis sometimes difficult. Siemens Computed Tomography, using Dual Energy acquisition techniques, allows the visualization of uric acid deposits. These urate crystal deposits are most often located in peripheral joints or near the surrounding soft tissues. The question, which had to be clearified in this investigation was whether the urate crystal deposits must have a minimum size to trigger clinical symptoms. 76 peripheral joints were examined and evaluated using Dual Energy CT techniques. The size of the uric crystal deposits were correlated to the presence of pain at the exact location of these deposits. Additionally, the correlation between serum uric acid blood levels and the final diagnosis, including the results of all available examinations, was established.

Diagnosis
Urate crystal deposits > 2 mm correlated to 100 % with pain at the exact given location. All patients with urate crystal deposits > 2 mm had increased uric acid blood levels, either actually or reported. These patients were then finally diagnosed with gout, taking all performed examinations into consideration. Urate crystal deposits ≤ 2 mm did not correlate in any instance with pain exactly at the deposit site. The uric acid blood levels in these patients at the time of the examination were partly elevated (43 %) partly normal (57 %). In patients with no detectable urate crystal deposits, the uric acid blood levels were normal. The existing symptoms were explained through differential diagnosis (some of which were found during the Dual Energy CT examination).

Protocol

Comments
Dual Energy CT allows the quantitative imaging of urate crystal deposits. A minimum size of the urate crystal deposits > 2 mm seems to be the pre-requisite for inducing clinical symptoms. Taking into consideration the size of the urate crystal deposits, the diagnosis of clinically manifested gout can be reliably made. Patients, of course, prefer the non-invasive acquisition protocol in comparison to invasive punctures.