Current approach to muscle imaging in myositis.

PURPOSE OF REVIEW: Muscle imaging is commonly utilized in idiopathic inflammatory myopathies (IIM) for diagnostic evaluation, selection of muscle biopsy site, and differentiating between disease activity versus damage. In this review, we discuss the current state and recent developments in the use of muscle imaging modalities including muscle magnetic resonance imaging (MRI), ultrasound (US), and positron emission tomography (PET) scan.

RECENT FINDINGS: Muscle MRI is a clinically useful tool in evaluation of IIM with studies showing good correlations between pattern of morphological changes on MRI and histopathological findings on muscle biopsy. The use of computer aided diagnostics to enable quantification of muscle pathology will be a welcome development for future studies and trials. New studies highlight that muscle US could be a particularly useful point of care tool in longitudinal monitoring of patients with active myositis. Muscle FDG-PET scan shows inflammatory activity in IIM muscle and can also provide additional information on extra-muscular manifestations and cancer screening. Utilization of novel tracers is an exciting development for IIM evaluation.

SUMMARY: Muscle MRI remains the gold standard for muscle imaging in IIM. Growing literature on muscle US and PET scan highlight their promising applications in IIM.