Imaging biomarkers in the idiopathic inflammatory myopathies, 2023, Adeel S. Zubair et al

MRI assessing muscle metabolism
Quantification of muscle metabolism by measuring pH and high-energy phosphate metabolites [phosphocreatine, inorganic phosphate, and adenosine triphosphate (ATP)] by phosphorus-31 magnetic resonance spectroscopy (P-MRS) can identify metabolic abnormalities in DM, juvenile dermatomyositis (JDM), and also treatment response (9, 80, 81). Mean ATP and phosphocreatine values are much lower in the thigh muscles of patients with JDM (81). Post-exercise P-MRS indices are impaired in DM with prolonged post-exercise recovery likely related to impaired perfusion (80). In DM, JDM, and PM, these metabolic abnormalities improve with corticosteroid therapy (81–83). On the contrary, patients with IBM have abnormal resting metabolites but normal post-exercise recovery parameters (84). While MRS can be a useful modality that can differentiate between subtypes of IIMs and assess treatment response, it is limited by cost and availability, and still mostly used for research purposes (9, 20, 39).

Conclusion
There have been significant advances in imaging technologies in the past two decades that have impacted the clinical practice and management of patients with IIMs(Idiopathic inflammatory myopathies). These evolving technologies have the potential to provide an objective assessment of muscle health once their utility is confirmed in large-scale prospective studies. Eventually, we anticipate that these technologies will be incorporated into a validated paraclinical assessment system that allows for more sensitive tracking of disease activity and treatment response to therapeutic interventions both in the clinic and in the context of therapeutic clinical studies.

https://www.frontiersin.org/articles/10.3389/fneur.2023.1146015/full