Background The value of magnetic resonance imaging (MRI) in the detection of erosions on the sacroiliac joints (SI-joints) is controversial. Structural changes on the other hand are getting more and more into scientific focus.
Objectives The aim of this study is a comparison between x-ray, low dose computed tomography (CT) and MRI. The presented data are preliminary results from the sacroiliac joint magnetic resonance imaging and computed tomography (SIMACT) study.
Methods We investigated prospectively 30 patients with lower back pain and the suspicion of axSpA expressed by an experienced rheumatologist. All patients underwent a low dose CT (Somatom Definition Flash, Siemens, Germany) and an MRI (3.0T Magnetom Skyra, Siemens, Germany) of the SI-joints. Imaging data were compared with X-ray of the pelvis. The MRI protocol contained these sequences: T1-weighted spine echo (T1-SE), short tau inversion recovery (STIR), T1-weighted 3D volumetric interpolated breath hold examination (VIBE) high resolution sequence, all in paracoronal orientation. The grade of the disease was scored in X-ray according to the modified New York criteria and the erosions were counted by quadrant by a blinded reader. The final diagnosis made by the rheumatologist was also used for comparison.
Results CT and T1-SE showed no significant differences in detecting erosions. 3D-VIBE found significantly more erosions in patients with axSpA compared to CT and T1-SE. (n=22; CT 178 erosions, T1 163, VIBE 421; average CT 5.9, T1 5.4, VIBE 14.0; p<0.001). In other diagnosis (osteoarthritis N=4, triangular hyperostosis N=3, others N=1) there were no significant differences among imaging modalities. The erosion count in 3D-VIBE correlated with the grade of sacroiliitis in X-ray (r=0.123, p=0.007).
Conclusions High-resolution 3D MR sequences like 3D-VIBE are more suitable in detecting erosions on the SI-joints than conventional MRI (T1-SE) and even low dose CT. They are therefore a reasonable supplement to any MRI protocol and may improve the ability of MRI for diagnosis both in early and advanced SpA.
Disclosure of Interest None declared