Imaging of inflammatory rheumatic diseases of the axial skeleton (Sacroiliitis) When and how should we use MRI?

Inflammatory involvement of the sacroiliac joints is the hallmark of the sp ondyloarthropathies (SpA), in particular ankylosing spondylitis (AS). One l eading symptom of SpA is inflammatory back pain (IBP), which may be indicat ive of sacroiliitis. Conventional diagnostic imaging is insufficient at ear ly stages of sacroiliitis because of the low sensitivity of conventional ra diographic scans. In contrast, magnetic resonance imaging (MRI) of the sacr oiliac joints depicts both acute and chronic inflammatory changes at all st ages of the disease. Disadvantages of MRI are the operator-dependency the l ack of standardization, and the relatively high costs. Therefore, in the er a of cuts in health care expenditure, the Diagnostic Imaging in Rheumatolog y Study Group of the Berlin Regional Rheumatology Center, which consists of experienced rheumatologists, skeletal radiologists, and orthopedic surgeon s, has compiled a survey of diagnostic imaging in sacroiliitis covering the clinical background, technical details, radiation exposure, and costs. Con ventional x-rays remain the standard imaging procedure for the diagnosis of AS. Early sacroiliitis can be detected with higher sensitivity by MRI usin g contrast agents or fat suppression techniques. Because of its lack of rad iation exposure, MRI is the method of choice in children and young women. M RI allows for a more accurate diagnosis of inflammatory back pain by provid ing objective evidence of inflammation in the sacroiliac joints. Computed t omography can be superior to MRI when bony changes have already occurred.