Among patients with gout, characteristics of color-coded dual-energy computed tomography (DECT) lesions may help to differentiate between pure monosodium urate and calcium-containing depositions, according to study results published in Arthritis Research & Therapy.
While DECT may help in the diagnosis of gout by color-coding monosodium urate depositions, the scanner needs to be able to distinguish these lesions from surrounding tissues, especially, calcium-containing depositions. The objective of the current study was to assess the characteristics and locations of color-coded DECT lesions in patients with gout.
The cross-sectional, observational study included adults with a clinical suspicion of gout who were referred to the Center for Rheumatology and Spine Diseases, Rigshospitalet, Denmark. All participants underwent DECT of the hands, knees, and feet. For each lesion, researchers registered the properties (mean density and mean DECT ratio and size) and location.
The study sample included 27 patients (n=23 with gout), with a total of 4033 color-coded DECT lesions (3918 lesions in patients with gout). The DECT ratios of color-coded DECT lesions in patients with gout approximated a normal distribution with a mean of 1.06, but the distribution showed a heavy right tail, indicating that color-coded DECT lesions in patients with gout have heterogeneous properties; some lesions may have the properties of pure monosodium urate depositions, while others may have a higher DECT ratio indicating calcium-containing depositions.
Common locations for all color-coded DECT lesions included the knee (78% of participants), the first metatarsophalangeal (83%), and the midtarsal joints (61%) along with the quadriceps (52%) and the patella tendons (52%).
Lesions were separated into 4 subgroups (“possible” calcium-containing material, dense tendon, and image noise artifacts, and “definite” monosodium urate depositions) to assess the potential differences in distribution of lesions that unquestionably represented monosodium urate depositions from lesions that could potentially represent other lesions.
Definite monosodium urate depositions had a similar distribution pattern and were the only lesions found in the first metatarsophalangeal joints and patella tendons. On the other hand, possible calcium-containing lesions and nongout monosodium urate-imitating lesions, defined as properties of definite monosodium urate lesions in patients without gout, were mostly found the in larger joints (knees, midtarsal, and talocrural) and tendons (Achilles and quadriceps).
One of the study’s limitations included the small sample size.
“In the current gout patient cohort, color-coded DECT lesions at the [metatarsophalangeal] joint and patella tendon were exclusively pure MSU depositions. All patients [with] gout had lesions in  or both of these locations. A sole focus on these regions when diagnosing patients [with] gout may therefore improve specificity without reducing sensitivity of DECT scans,” the researchers concluded.
Disclosure: Several study authors declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Christiansen SN, Müller FC, Østergaard M, et al. Dual-energy CT in gout patients: Do all colour-coded lesions actually represent monosodium urate crystals? Arthritis Res Ther. 2020;22(1):212.