Sacroiliitis: current imaging modalities and future directions: a narrative review

Sacroiliitis, or inflammation of one or both of the sacroiliac joints (SIJs), can be difficult to distinguish from other etiologies of lower back and buttock pain due to diverse patient presentations and a lack of highly sensitive and specific diagnostic modalities. Although physical examination, provocation tests, and an SIJ block test are informative, confirmatory imaging is often required to improve diagnostic accuracy. Radiography and magnetic resonance imaging (MRI) are the most popular imaging studies for this purpose, but other modalities such as computed tomography (CT), single-photon emission computed tomography (SPECT)/CT, positron emission tomography (PET)/CT, and ultrasonography are emerging as viable alternatives. This narrative review provides a comprehensive summary of the history, clinical use and limitations of each imaging modality in the diagnosis of sacroiliitis. Novel techniques in image acquisition and analysis, such as digital tomosynthesis (DT), volumetric interpolated breath-hold examination (VIBE) MRI and dual energy CT (DECT) are also discussed.