Abstract
Magnetic resonance imaging (MR) is the method of choice in patients with ankylosing spondylitis in preradiologic stage. Especially in very young patients and patients with a short history of problems, where are not expected bone changes.
MR is also used as a complementary method to X-ray, if this is negative and the clinical signs of the disease are presented. The third most frequent indication is establishment of inflammation activity for the start of biological therapy and for monitoring the treatment.
An advantage of MRI in comparison to X-ray methods (X-ray, CT) is the absence of ionizing radiation and the ability to assess the bone marrow edema. The most important is the demonstration of active inflammation on sacroiliac joints.
This feature is important for diagnose the disease by currently used ASAS classification in the imaging branch of the classification. Other signs of active inflammation and signs of chronic changes, which is also seen on MRI, are alone insufficient to diagnose active sacroiliitis by ASAS.