Simultaneous Multislice Accelerated Diffusion Tensor Imaging of Thigh Muscles in Myositis.

Abstract

Diffusion tensor imaging (DTI) has long been proposed as a potential tool for quantitatively evaluating muscle lesions of dermatomyositis (DM) and polymyositis (PM), but adapting DTI to thigh muscles requires minimizing acquisition time. We investigated the clinical feasibility of using SMS-EPI-DTI (simultaneous multislice [SMS] accelerated echo planar imaging [EPI] DTI) to image and analyze the anisotropic diffusion characteristics of thigh muscles in patients with DM or PM. Both thighs of 20 patients (seven patients with DM and 13 patients with PM) and 10 healthy control subjects were prospectively scanned using SMSEPI-DTI. Tractographic images and DTI-derived parameters, including fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values and three eigenvalues (λ₁, λ₂, and λ₃), were obtained from four selected muscles (vastus medialis, vastus intermedius, adductor magnus, and semimembranosus) and were analyzed. After Bonferroni correction, p < 0.017 (0.05/3) was considered to denote statistical significance. SMS-EPI-DTI allowed imaging of both thighs of patients with DM or PM and healthy control subjects within approximately 5 minutes. For each of the four measured muscles, FA values for patients with edematous muscles were lower than those for patients with unaffected muscles and healthy control subjects with normal muscles (p < 0.017 for all). The ADC and λ₁, λ₂, and λ₃ values of edematous muscles were significantly higher than those for patients with unaffected muscles and healthy control subjects (p < 0.017 for all). Unaffected muscles of patients and healthy control subjects were similar in terms of all parameters (p > 0.017 for all). SMS-EPI-DTI is clinically feasible for imaging thigh muscles and quantitatively evaluating edematous muscles of patients with DM or PM.