Introduction: To assess the diagnostic value of para-axial T2w-TSE (paT2) and fat-suppressed proton density (paPD-FS) MRI sequences for the evaluation of the sacroiliac joint (SIJ) of patients with axial Spondylarthritis (SpA).
Materials and methods: One hundred and six patients with clinical findings suggestive of SpA underwent an MR protocol of the SIJ with additional paPD-FS (41 patients) and paT2 (105 patients). Acute (bone marrow oedema [BME], enthesitis, capsulitis, synovitis) and chronic findings (erosions, ankylosis) were assessed by paPD-FS and compared with the gold standard post-contrast sequences, whereas chronic features (because of the lack of fat suppression) were evaluated on paT2 and compared with pcT1.
Results: paPD-FS demonstrated high sensitivity (98.9 %) and specificity (99.1 %) for BME; sensitivity and specificity for synovitis and enthesitis were 100 %; 85.7 % and 100 %, respectively, for capsulitis. paPD-FS and paT2 showed 100 % sensitivity and specificity for ankylosis; for erosions, paT2 demonstrated 85.3 % sensitivity and 100 % specificity, whereas paPD-FS, respectively, 98 % and 100 %.
Discussion: PaT2 and paPD-FS provided precious information enabling an accurate interpretation of the heterogeneous findings of SpA. paPD-FS showed good results in detecting acute and chronic lesions and its inclusion in a routine MR examination of the SIJ could increase the diagnostic performance of a pre-contrast protocol.
Key points: Para-axial sequence should be included in a routine MRI protocol for SpA. Acute and chronic findings can be evaluated on para-axial PD-FS. Para-axial PD-FS is superior to para-axial T2-W in SpA.
Keywords: Acute disease; Chronic disease; MRI; Sacroiliitis; Spondylarthritis.