Comparison of radiography, computed tomography and magnetic resonance imaging in the detection of sacroiliitis in ankylosing spondylitis

Objective: The objectives of our study were to evaluate the role of conventional radiography, computed tomography (CT), and magnetic resonance imaging (MRI) in the detection of sacroiliitis in ankylosing spondylitis (AS), along with the radiological spectrum of disease. Materials and Methods: Thirty-six patients with symptoms of inflammatory back pain (IBP) were evaluated with conventional radiography, CT, and MRI. The sacroiliac (SI) joints were evaluated for joint margins, joint space, sclerosis, and bone marrow changes. Imaging findings were analyzed for correlation with multiple clinical characteristics and comparison among different imaging modalities. Results: CT and MRI are extremely useful in the absence of alterations or minimal changes on plain radiographs. CT is comparable to MRI for joint space alteration, however, itis superior for evaluating bone sclerosis and erosion, and is indicated especially for detecting chronic alterations. The capability of MRI to distinguish between acute and chronic changes and estimate the degree of disease activity and damage present at diagnosis can be beneficial in monitoring the effect of pharmacological treatment. The administration of Gadolinium did not provide any additional information for the diagnosis of sacroiliitis and the evaluation of the features of active inflammation. Conclusions: Between radiography, CT and MRI, MRI outscores the others in being able to delineate the inflammatory changes of early sacroiliitis in AS. Therefore, if early sacroiliitis is suspected clinically, MRI should be the preferred imaging modality for evaluating the SI joint. However, CT is more sensitive than radiography and MRI in detailing the structural changes of sacroiliitis in AS.