Abstract
BackgroundDual-energy computed tomography (DECT) is a new diagnostic tool for gout, but its sensitivity has not been established. Our goal was to assess the sensitivity of DECT for the detection of monosodium urate (MSU) deposits in non-tophaceous and tophaceous gout, both at the level of the patient and that of the individual joint or lesion.MethodsDECT was performed on 11 patients with crystal-proven non-tophaceous gout and 10 with tophaceous gout and included both the upper and lower extremities in 20/21 patients. DECT images were simultaneously acquired at 80 and 140 kV and then processed on a workstation with proprietary software using a two-material decomposition algorithm. MSU deposits were color coded as green by the software and fused onto grey-scale CT images. The number and location of these deposits was tallied independently by two DECT-trained radiologists blinded to the clinical characteristics of the patient. Sensitivity of DECT was defined as the proportion of patients with a confirmed diagnosis of gout which was correctly identified as such by the imaging technique. All patients provided informed consent to participate in this IRB-approved study.ResultsMSU deposits were detected by DECT in ≥1 joint area in 7/11 (64 %) patients with non-tophaceous gout, but were only detected in 3/12 (25 %) joints proven by aspiration to be affected with gout. Inclusion of the upper extremity joints in the scanning protocol did not improve sensitivity. All 10 patients with tophaceous gout had MSU deposits evident by DECT. The sensitivity of DECT for individual gouty erosions was assessed in 3 patients with extensive foot involvement. MSU deposits were detected by DECT within or immediately adjacent to 13/26 (50 %) erosions.ConclusionsA DECT protocol that includes all lower extremity joints has moderate sensitivity in non-tophaceous and high sensitivity in tophaceous gout. However, DECT has lower sensitivity when restricted to individual crystal-proven gouty joints in non-tophaceous disease or individual erosive lesions in tophaceous gout. The detection of MSU deposits by DECT relates to their size and density and the detection parameters of the DECT scanner and adjustment of the latter might improve sensitivity.
Highlights
Dual-energy computed tomography (DECT) is a new diagnostic tool for gout, but its sensitivity has not been established
There was no significant difference in age between the patients with non-tophaceous and tophaceous gout
In our 11 patients with non-tophaceous gout, DECT of joints in all four extremities demonstrated monosodium urate (MSU) deposits in seven, equating to an overall sensitivity of 64 %. These deposits were only detected in three of 12 (25 %) joints shown to have MSU deposits by aspiration and polarized light microscopic analysis of the synovial fluid or soft tissue material. In this small series of seven non-tophaceous gout patients with MSU deposits detected by DECT, inclusion of the upper extremities in the scanning protocol served to identify MSU deposits in the elbows of three, but each had concomitant deposits in their lower extremities
Summary
Dual-energy computed tomography (DECT) is a new diagnostic tool for gout, but its sensitivity has not been established. Various advanced imaging techniques are being utilized, including ultrasonography with power Doppler, magnetic resonance imaging (MRI), and conventional computed tomography (CT). Each has their unique advantages and disadvantages. Dual-energy CT (DECT) is a new technique that allows identification of MSU crystal deposits. With this imaging methodology, the compositions of different tissues are determined by analyzing the difference in attenuation in a material exposed simultaneously to two different X-ray spectra. Whereas its sensitivity has been reported to be 100 % for clinically-overt tophaceous disease [7,8,9], its sensitivity has not been fully established for non-tophaceous disease where its diagnostic utility would be the greatest
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