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Tristan Pascart, MD, PhD Credit: Research Gate Results from the GOUT-DECTUS study, a prospective, multicenter, 24-month longitudinal pilot study, have indicated dual-energy computed tomography (DECT) causes complete tophus resolution faster than ultrasound. Ultrasound is more and more commonly utilized by rheumatologists to locate monosodium urate (MSU) deposits on the cartilage surface and tophi. DECT is primarily used for identifying and breaking down the crystal core of the tophus, while ultrasound can identify both the core and the crown of macrophages surrounding it.
As a result, ultrasound is widely considered the default treat-to-target (T2T) urate-lowering therapy (ULT) for treating gout . 2 “The kinetics of the change in individual tophi volume, the hallmark elementary lesion in gout, with [ultrasound] and DECT has never been studied and compared, and it is not known how individual tophus volume measured with the two techniques changed during T2T,” wrote Tristan Pascart, MD, PhD, department of rheumatology, Lille Catholic University, Saint-Philibert Hospital, and colleagues. “The main objective of the study was to examine the kinetics of tophus volume measured with DECT and [ultrasound] in patients with gout during their first 24 months of T2T ULT.
” 1 Pascart and colleagues’ study, titled GOUT-DECTUS, included 55 patients over the course of 24 months in three French centers. Clinical visits for DECT and ultrasound scans of the knees and feet were planned at baseline, 6, 12, and 24 months. Gout history, including number of flares during the last 6 months, ongoing treatments, and SU levels were collected at each visit.
1 Patients included in the study were 18-80 years old, had an SU level ≥6.0 mg/dL (360 μmol/L), had not used ULT over the past year, and at least one tophus in the knee or foot detected with ultrasound. Of these patients, 31/54 had their index tophus localized at the first MTP joint, 11/54 had knee tendon or ligament tophi, and 6/54 exhibited tophi on the tarsi.
Overall, 44/51 participants exhibited ultrasound tophi in the feet, and 17/50 in the knees. 1 Index tophi were not identified by DECT in 12/37 participants. These tophi were localized around the MTP1 joint (10/12) and in the knee collateral ligaments (2/12).
Additionally, they were smaller than the average ultrasound tophi volume and were associated with a lower prevalence of DC sign than the average of the cohort. 1 Investigators noted, by the end of the study at month 24, median index tophus volume had changed from 0.61 cm 3 at baseline to 0.
07 cm 3 when measured with ultrasound, and from 0.1 cm 3 to 0 cm 3 when measured with DECT. Correlation of MSU volume change between ultrasound and DECT was weak throughout ( P =.
33 at month 6, P =.18 at month 12, P =.25 at month 24).
1 Investigators noted that participants with tophus had a DECT volume greater than 0 cm 3 at baseline exhibited greater dissolution by months 6 (0.16 cm 3 , 95% CI, .02-.
29) and 12 (.02 cm 3 , 95% CI, 0.005-0.
18), and by month 24 the tophus were undetectable altogether. Ultrasound, however, was still capable of identifying tophi at month 24 (.22 cm 3 , 95% CI, .
07-1.81). 1 Ultimately, the team explained these data indicate a distinct difference in the effectiveness and functionality of ultrasound and DECT.
Through ultrasound, a tophus’s crystal core has generally dissolved by month 12, while the general tophaceous structure dissipates unevenly and still exists by month 24 in 51.7% of cases. This discrepancy was corroborated by the poor to moderate correlations in tophus volume change throughout follow-up.
1 “Further studies are needed to develop which quantitative thresholds of elementary gout lesions should be considered a treatment responses for [ultrasound] and DECT separately, specifically for each imaging technique,” wrote Pascart and colleagues. 1 Pascart T, Richette P, Bousson V, et al. Time-course of Tophus Resolution on dual-energy CT and ultrasound after 24 months of a treat-to-target strategy: Results from gout-DECTUS study.
Joint Bone Spine . Published online March 24, 2025:105892. doi:10.
1016/j.jbspin.2025.
105892 Filippou G, Pascart T, Iagnocco A. Utility of Ultrasound and Dual Energy CT in Crystal Disease Diagnosis and Management. Curr Rheumatol Rep .
2020;22(5):15. Published 2020 Apr 15. doi:10.
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