Bone Single Photon Emission/Computed Tomography in the Detection of Sacroiliitis in Seronegative Spondyloarthritis: A Comparison with Magnetic Resonance Imaging

OBJECTIVE Seronegative spondyloarthritis (SpA) is characterized by chronic inflammation affecting the axial skeleton, entheses and occasionally peripheral joints. The involvement of the sacroiliac joints, sacroiliitis, is considered as a pathognomonic radiographic finding. Magnetic resonance imaging (MRI) is the method of choice for its early detection. Bone scintigraphy (BS) is characterized by high sensitivity in the diagnosis of bone and articular diseases. Limited value of BS in the diagnosis of sacroiliitis may be attributed to the use of planar imaging. In the present study, we aimed to investigate the role of SPECT in SpA, compared to MRI. METHODS Forty-three patients suffering from inflammatory back pain underwent MRI evaluation of the sacroiliac joints and BS, combined with SPECT in the same region, for the assessment of sacroiliitis. RESULTS Bone SPECT revealed no findings of sacroiliitis in 11 patients, with total agreement with MRI. Findings of chronic lesions were demonstrated from both modalities in 2 patients. Bone SPECT and MRI findings were in concordance regarding the investigation of active sacroiliitis, with the exception of one patient with mild SPECT findings and negative MRI examination; the diagnosis of AS however, was established one year later, after a positive follow-up MRI. The evaluation of the planar imaging of the whole skeleton and SPECT imaging, revealed additional lesions. CONCLUSION Bone SPECT is a reliable imaging method in the diagnosis of active sacroiliitis. Its application on planar BS, an economic and widely available diagnostic technique, appears to be a valuable aid for the clinician.