Departure of the project leader

The investigators hypothesize that the T1 Dixon post-Gadolinium and T2 Dixon sequences will show good diagnostic performances for active sacroiliitis compared to the reference test (Short tau inversion recovery) and clinical-biological criteria, which will allow a better diagnosis of active sacroiliitis

Inclusion Criteria:

• The patient must have given their free and informed consent and signed the consent form
• The patient must be a member or beneficiary of a health insurance plan
• The patient is at least 18 years old
• The patient has a clinically diagnosed axial spondyloarthritis (axSpA) (ASAS or AMOR classification)
• Patient has an active axSpA (BASDAI>4)

Exclusion Criteria:

• The subject is participating in another study, or is in a period of exclusion determined by a previous study
• The subject refuses to sign the consent
• It is impossible to give the subject informed information
• The patient is under safeguard of justice or state guardianship
• The patient is pregnant or breastfeeding
• The patient has a contra-indication

Patients with clinically-confirmed axial spondyloarthritis treated in the radiology services of the CHUs of Montpellier and Nimes