Imaging tools for the clinical assessment of idiopathic inflammatory myositis

To summarize advances in the imaging of idiopathic inflammatory myopathies.

T2-weighted MRI with fat suppression or short tau inversion recovery sequences are the most sensitive and specific routine method of polymyositis and dermatomyositis imaging. MRI also represents an important aid in the identification of biopsy sites, with whole-body MRI sensitively visualizing the distribution of muscle involvement throughout the body. Ultrasound may be a cost-effective alternative to MRI, with contrast-enhanced ultrasound also permitting the assessment of muscle vascularization. PET sensitively detects increased muscle metabolism and simultaneously screens for underlying malignancies in dermatomyositis. Most scintigraphic techniques have a low sensitivity and specificity in the detection of muscle involvement, and it is unclear whether they provide an added benefit. New MRI techniques, such as T2 mapping, diffusion-weighted imaging and blood oxygenation level-dependent imaging, can provide information on muscle recruitment, myofibrillar structure and blood supply.

In suspected myositis, muscle imaging should be strongly considered prior to obtaining a muscle biopsy. Future research should prospectively study the use of muscle imaging in the evaluation of treatment response and muscle function.