Added Value of Diffusion Weighted MRI in Evaluation of Sacroiliitis in Newly Diagnosed Patients of Spondyloarthropathy.

Spondyloarthropathy encompasses a group of chronic immune-mediated rheumatic inflammatory diseases characterized by axial joint inflammation, peripheral arthritis, enthesitis, dactylitis and extra-articular features such as psoriasis, uveitis, inflammatory bowel disease (crohns and ulcerative colitis) [1].

Axial spondyloarthritis (SpA) has significant social and psychiatric impacts [2, 3] and affects quality-of-life (4-5). Patients often experience prolonged delays in diagnosis. Early disease diagnosis is becoming more important as it will facilitate early therapeutic interventions (6).

There's no "gold standard" feature for diagnosing axSpA. It's diagnosed through a combination of patient history, clinical examination, laboratory findings as blood tests (both for HLA-B27 and for markers of inflammation, such as C-reactive protein), and imaging tests, such as X-ray and MRI.

Sacroiliitis is commonly the first manifestation and an important indicator of the diagnosis and classification of the the disease. (7) Radiographic sacroiliitis is a key criterion. However, sole reliance on radiographs is associated with significant diagnostic delay [8]. Magnetic Resonance Imaging (MRI) can detect axial inflammation before radiographic changes. (9) So with the development of Assessment of Spondyloarthritis International Society (ASAS) classification criteria for ax-SpA, MRI is increasingly being used to early diagnose and monitor disease activity. (10) Diffusion-weighted imaging (DWI) offers a new approach to assess inflammation. It is a functional MRI technique that can non-invasively asses the random movements of water molecules through the measurements of the ADC value. (11). Inflammation produces an increase in the apparent diffusion coefficient (ADC) of water molecules in affected tissues, probably owing to an increase in the ratio of extracellular to intracellular water. (12-13) Recently several studies have shown that DWI is an effective tool in early diagnosis of axSpA (14-16). Furthermore, the ADC value may serve as a quantitative biomarker of disease activity, allowing monitoring and guiding treatment. (17-18)