Inflow-based vascular-space-occupancy MRI for evaluation of arteriolar muscular blood volume in dermatomyositis patients

Objective: To investigate the reproducibility of inflow-based vascular-space-occupancy (iVASO)-MRI in quantifying skeletal muscle perfusion and its potential clinical value in patients with dermatomyositis (DM). Methods: Totally 15 consecutive patients with DM and 15 healthy volunteers were enrolled in this prospective study from December 2018 to April 2019 at Nanfang Hospital, Southern Medical University. All subjects underwent T₁WI, short-tau inversion recovery (STIR) T₂WI, and iVASO-MRI of thigh on a 3.0 T MR scanner. According to findings on T₁WI and STIR T₂WI, the muscles were divided into normal, unaffected, edematous and atrophic or fat-infiltrated groups. Maximum arteriolar muscular blood volume (MBVa_-max) and mean MBVa (MBVa_-mean) of these 4 groups of muscles were obtained by 2 radiologists independently. In order to evaluate the reproducibility of iVASO, the repeated scan was performed 3 days later in 17 subjects (12 healthy volunteers and 5 DM patients), and the MBVa values were measured to calculate the intraclass correlation coefficients (ICC). The MBVa_-max and MBVa_-mean among the 4 groups were compared by using Kruskal-Wallis H test and the differences of each 2 groups was compare by using Mann-Whitney U test. Results: The ICC between the 2 observers was 0.95 and 0.96 for MBVa_-max and MBVa_-mean, respectively. The ICC between repeated tests was 0.87 and 0.89 for MBVa_-max and MBVa_-mean, respectively. There was significant difference among normal muscles, unaffected muscles, edematous muscles and atrophic or fat-infiltrated muscles (P < 0.001). Post hoc comparisons of MBVa_max and MBVa_-mean showed that compared to normal muscles, unaffected muscles, edematous muscles and atrophic or fat-infiltrated muscles had a significant decrease of MBVa (P < 0.05). Unaffected muscles and edematous muscles showed no significant difference in terms of MBVa_-max and MBVa_-mean (both P = 0.99), which were significantly higher than those of atrophic or fat-infiltrated muscles (P < 0.05). Conclusions: iVASO-MRIcan reliably quantify the MBVa of thigh muscular arteriolar, and it is potentially valuable in the diagnosis of DM. (authors)