Magnetic resonance imaging (MRI) is part of the Assessment of SpondyloArthritis international Society (ASAS) criteria for diagnosis of axial spondyloarthritis. Although the strength of MRI in detecting acute and active inflammation of the sacroiliac joints is uncontested, there is a controversy over its benefit in detecting structural changes. Thus, conventional X-ray (CR) is still a necessary imaging modality for the sacroiliac joints. It is attributed with a higher sensitivity in detecting erosions, sclerosis and ankylosis. However, plain film projection radiography has not the possibilities of tomography. Therefore, some changes might be hidden by overlapping of other structures: bowel gas for example might imitate erosions.
Here the advantages of computed tomography (CT) are quite clear. It is not affected by those difficulties and on the other hand is capable to visualise the chronic changes. However, CT is not part of the standard diagnostic algorithm due to the additional radiation exposure. Nevertheless it is now possible to reduce the exposure in with multidetector CT devices and new software, so that the radiation dose applied is comparable to CR. Secondly, innovative developments of MR pulse sequences are opening up the opportunity to get a high-resolution anatomical overview without any ionising radiation. Therefore, applying these new developments, MRI is capable of combining the detection of even small erosions with its possibilities in finding active inflammation and joint changes.
This lecture will summarize the current evidence for the application of MRI to depict structural damage. Furthermore, we will present the structural findings described above and will outline important differential diagnoses like triangular hyperostosis and osteoarthritis.
Disclosure of Interest None Declared