MRI is the gold standard modality for non-invasive evaluation of myositis, which shows a classic edema signal pattern (high T2WI and STIR signal) in affected muscles. Inflamed muscles demonstrate contrast enhancement.
If chronic, T1WI will show high muscle signal indicating fat replacement and atrophy.
1. William Palmer, Laura Bancroft, Fiona Bonar, Jung-Ah Choi, Anne Cotten, James F. Griffith, Philip Robinson, Christian W.A. Pfirrmann. Glossary of terms for musculoskeletal radiology. (2020) Skeletal Radiology. doi:10.1007/s00256-020-03465-1 - Pubmed
2. Kaushik S, Flagg E, Wise CM, Hadfield G, McCarty JM. Granulomatous myositis: a manifestation of chronic graft-versus-host disease. (2002) Skeletal radiology. 31 (4): 226-9. doi:10.1007/s00256-001-0469-5 - Pubmed
4. Smitaman E, Flores DV, Mejía Gómez C, Pathria MN. MR Imaging of Atraumatic Muscle Disorders. (2018) Radiographics : a review publication of the Radiological Society of North America, Inc. 38 (2): 500-522. doi:10.1148/rg.2017170112 - Pubmed