Given the available data, the utility of PET/CT in the diagnosis of axSpA is uncertain at this time. MRI Sacroiliac Joints After radiography is performed, MRI of the sacroiliac joints is the next imaging technique of choice in the evaluation of patients with suspected axSpA [1,3,19,22]. MRI of the sacroiliac joints is widely recognized as an important tool in the evaluation of patients with suspected axSpA, resulting in improved diagnostic confidence and yielding findings that stimulate changes in both diagnosis and treatment plans for patients [1,3,19,22,74]. Additionally, MRI findings have been shown to be predictive of both subsequent radiographic disease progression and the likelihood of response to therapy [36,63,75,76]. MRI, utilizing short tau inversion recovery (STIR) and T1-weighted images, can identify both active inflammatory lesions of the sacroiliac joints (bone marrow edema, capsulitis, synovitis, and enthesitis) and chronic structural lesions (sclerosis, erosions, fat deposition, and ankylosis) that are typical for sacroiliitis [38,77]. MRI demonstrates active sacroiliitis with higher sensitivity and earlier than radiography because of its ability to detect inflammatory lesions of axSpA [13,36,37,78]. The inflammatory changes of sacroiliitis on MRI have been shown to precede structural radiographic findings by three to seven years [36,37]. MRI can also detect the chronic structural lesions of the sacroiliac joints with higher accuracy than radiographs [45]. It is important to recognize that the sensitivity and specificity of MRI for axSpA depends on the imaging criteria used, patient population, and reference standard for diagnosis. Early literature showed 95% sensitivity and 100% specificity of MRI for sacroiliitis, substantially higher than radiographs or bone scintigraphy, although that study included a small number of patients, and most subsequent studies demonstrate smaller yields [41].
Inflammatory Back Pain Known or Suspected Axial Spondyloarthropathy PCAs. Given the available data, the utility of PET/CT in the diagnosis of axSpA is uncertain at this time. MRI Sacroiliac Joints After radiography is performed, MRI of the sacroiliac joints is the next imaging technique of choice in the evaluation of patients with suspected axSpA [1,3,19,22]. MRI of the sacroiliac joints is widely recognized as an important tool in the evaluation of patients with suspected axSpA, resulting in improved diagnostic confidence and yielding findings that stimulate changes in both diagnosis and treatment plans for patients [1,3,19,22,74]. Additionally, MRI findings have been shown to be predictive of both subsequent radiographic disease progression and the likelihood of response to therapy [36,63,75,76]. MRI, utilizing short tau inversion recovery (STIR) and T1-weighted images, can identify both active inflammatory lesions of the sacroiliac joints (bone marrow edema, capsulitis, synovitis, and enthesitis) and chronic structural lesions (sclerosis, erosions, fat deposition, and ankylosis) that are typical for sacroiliitis [38,77]. MRI demonstrates active sacroiliitis with higher sensitivity and earlier than radiography because of its ability to detect inflammatory lesions of axSpA [13,36,37,78]. The inflammatory changes of sacroiliitis on MRI have been shown to precede structural radiographic findings by three to seven years [36,37]. MRI can also detect the chronic structural lesions of the sacroiliac joints with higher accuracy than radiographs [45]. It is important to recognize that the sensitivity and specificity of MRI for axSpA depends on the imaging criteria used, patient population, and reference standard for diagnosis. Early literature showed 95% sensitivity and 100% specificity of MRI for sacroiliitis, substantially higher than radiographs or bone scintigraphy, although that study included a small number of patients, and most subsequent studies demonstrate smaller yields [41].