Evolution of Tophus and Erosions of Hands and Feet at DECT

The main objective is to evaluate the decrease in crystalline volume of the target tophus using Dual-Energy Computed Tomography (DECT), after 6 months +/- 1 month of urate-lowering therapy with target uricemia.

Study hypothesis

* The dynamics of tophus resolution with urate-lowering therapy is poorly understood.
* It is variable according to the location of the tophus, peri articular / intratendinous, but also probably at the feet / hands, the initial overall volume of the tophus, the initial crystal charge of the tophus. Knowledge of prognostic factors for tophus resolution will help determine the best target for treatment follow-up for each patient.
* Erosions are the consequence of tophus. Tophus resolution could be associated with repair of erosions and stabilization of joint destruction.

Study design The research is a non-randomized prospective bi-centric study in adult patients with tophaceous gout. It aims at studying tophus resolution (main objective), and prognostic factors for tophus resolution (secondary objective), and bone erosions, with Dual-Energy Computed Tomography (DECT) (secondary objective).

Study population

* Adult patients with a tophaceous gout but no urate-lowering treatment or treatment but target not reached (target = uricemia \< 360µmol/L).
* Recruitment of patients during a visit or hospitalization in rheumatology at Lariboisière Hospital.

Calculated size of study population: 50 patients

No control group

Inclusion criteria

* Age greater than or equal to 18 years
* Patient with a tophaceous gout
* Without urate-lowering treatment or with treatment but uricemia not at target
* Having given its free and informed consent to participate in this study
* Affiliated with a social security system

Non-Inclusion criteria

* Pregnant or breastfeeding woman
* Participation in another intervention research or period of exclusion due to a previous research.
* Impossibility to position oneself in ventral position (position for hands/wrists DECT acquisition).

Acts or product added for the research study Dual-Energy Computed Tomography examination at 6 and 12 months +/- 1 month of medical treatment with uricemia \< 360µmol/L (baseline DECT is in the domain of usual care).

For each patient, 3 visits (usual care):

* M0: Inclusion visit
* M6 + /- 1 month: visit, usual care, + DECT for research purpose
* M12 + /- 1 month: visit, usual care, + DECT for research purpose

Research duration:

* Inclusion period: 24 months
* Duration of participation (treatment + follow-up): 12 months + /- 1 month
* Total duration: 37 months

Eligibility Criteria:
Inclusion Criteria:

* Age greater than or equal to 18 years
* Patient with a tophaceous gout
* Without urate-lowering treatment or with treatment but uricemia not at target
* Having given its free and informed consent to participate in this study
* Affiliated with a social security system

Exclusion Criteria:

* Pregnant or breastfeeding woman
* Participation in another intervention research or period of exclusion due to a previous research.
* Impossibility to position oneself in ventral position (position for hands/wrists DECT acquisition).