Experience of application of T2-mapping MRI assessment of inflammatory myopathies

Abstract

Specialized quantitative MRI techniques allow identifying structural changes in individual muscles in inflammatory myopathies.Aim. To evaluate the role of T2 mapping MRI and to evaluate specific changes in T2 relaxation time in patients with inflammatory myopathies at different stages of the disease process.Methods. T2 mapping technique for assessing structural changes in muscle tissues was optimized for the Philips “Ingenia” 3.0T MR scanner. T2 relaxation (T2rt) time of the thigh and lower leg muscles (muscule rectus femoris, m. vastus lateralis, m. adductor magnus, m. soleus, m. tibialis anterior, medial and lateral head of m. gastrocnemius) was assessed in the control group (n = 9) and the study group (n = 6). Patients recruited in the study group suffered from dermatomyositis and polymyositis of various severity.Results. The following values of T2rt were obtained in the control group: m.rectus femoris – 78.2±6.9 ms, m.vastus lateralis – 79.5±4.8 ms, m.adductor magnus – 77.1±4.4 ms, m. soleus – 92.9±4.3 ms, m. tibialis anterior – 89.4±1.3 ms, m.gastrocnemius medial head – 93.7±2.4 ms, m.gastrocnemius lateral head – 92.9±3.5 ms. Patients with polymyositis and dermatomyositis showed an increase in the signal intensity on STIR and PD-SPAIR in the structure of m.soleus, m. gastrocmenius, m.rectus femoris, as well as a significant increase in T2rt of 40–49% (p<0.01). T2rt values did not differ in patients with polymyositis who received drug therapy and had clinical remission. Patients with dermatomyositis who had laboratory remission along with the deterioration reported an increase in T2rt in the structure of long spine muscles, m. rectus femoris and m. vastus lateralis equal to 15–25% (p<0.05). However, none significant changes in the signal characteristics on STIR and PDSPAIR were reported.Conclusion. The sensitivity of the reported technique in the detection of sub-acute swelling of muscle tissue in the absence of significant changes in signal characteristics on routine MR sequences had been shown.