Spondyloarthritis (SpA) is one of the potentially debilitating inflammatory diseases that affect the whole body, primarily burdening the sacroiliac joints and the spine. It mostly affects young and middle aged adults. SpA can be classified to non-radiographic axial SpA (nr-axSpA) and radiographic axSpA (r-axSpA). The latter is ankylosing spondylitis (AS). The key to its early treatment is the radiological detection and management of sacroiliitis. To date, biologics is the most powerful anti-inflammatory drug. Recent research has shown that diffusion-weighted imaging (DWI) outperforms the sequence recommended by the Guidelines in diagnosing inflammation and assessing disease activity. Preliminary research conducted by our team has also demonstrated that apparent diffusion coefficient (ADC) is a valuable imaging biomarker. However, to date, no serum maker of comparable effectiveness has been identified. Damage-Associated Molecular Pattern (DAMP), including S100A8 and S100A9, high mobility group protein B1 (HMGB1) and Tenascin-C (TNC), may play a role in inflammation by regulating the TLR4/MyD88/NF-κB signaling pathways. The present study will enroll 20 patients with nr-axSpA and 20 patients with AS. It will utilize serum DAMP and ADC to assess disease activity before and after treatment as well as the change in and correlations of treatment outcomes, in order to identify objective and quantifiable serum and imaging markers that are beneficial in clinical applications. ADC is the primary outcome. The main hypothesis is that disease activity as measured by ADC will be reduced after 1 year of treatment from baseline as compared to before treatment at baseline. Study findings will indicate the utility of ADC as an objective indicator of disease activity for guiding therapeutic approaches and improving dosage adjustment in clinical applications.