RESUMO
Objective To evaluate the fatty infiltration of lower limbs (pelvis, thighs and calf) by using iterative decomposition of water and fat with asymmetry and least squares estimation‐quantitative fat imaging (IDEAL‐IQ) in Duchenne muscular dystrophy (DMD) patients, and correlate muscle fat fraction(FF) with clinical assessments. Methods The prospective study method was applied, twenty‐one patients with DMD were diagnosed by genetic analysis and/or muscle biopsy and twenty‐one age‐matched healthy control subjects, were evaluated using IDEAL‐IQ, calculating fat fraction (FF) of muscles in the lower limbs. The clinical data of patients, such as age, height, weight, course of disease, time to walk 10 m, Medical Research Council Scale score, were collected. The age and height between DMD group and control group were compared by independent sample t test. The weight, BMI and FF values between two groups were compared by independent samples nonparametric tests (Mann‐Whitney U tests). K related samples nonparametric test (Friedman test) was used for comparison of FF values between pelvic muscles, thighs muscles and calf muscles. The relationships between FF values and clinical assessments were investigated using Spearman correlation test. Results The mean FF of pelvic muscles [13.1(6.9, 33.8)] was significantly higher than that of the thighs muscles [8.3 (23.4, 4.5)] and calf muscles [8.3 (23.4, 4.5)] (all P<0.05) in DMD group. The FF of all the pelvic muscles in DMD were significantly higher than that of the control group muscles (all P<0.05). The gluteus maximus had the greatest mean FF values [34.7 (26.4, 63.7)] in pelvic muscles. The FF of all the thigh muscles in DMD were significantly higher than that of the control group muscles, except for the sartorius, adductor longus and gracilis (Z=0.69, 1.67 and 1.22, respectively, P=0.489, 0.094 and 0.222, respectively). The adductor magnus had the greatest mean FF values [27.2 (12.4, 58.5)] in thigh muscles. The FF of all the calf muscles in DMD were significantly higher than that of the control group muscles, except for the tibialis anterior and tibialis posterior (Z value was1.77 and 1.85, respectively, P value was 0.076 and 0.064, respectively). The gastrocnemius lateral had the greatest mean FF values [7.4 (4.6, 20.9)] in calf muscles. The mean FF value of pelvic muscles (r=0.679, 0.704,?0.761, 0.755, respectively, all P<0.001), thighs muscles (r=0.801, 0.813,?0.738, 0.706, respectively, all P<0.001) and calf muscles (r=0.502, 0.682,?0.637, 0.664, respectively, all P<0.05) were significantly correlate with age, course of disease, %MRC and time to walk 10 m. Conclusions The fat infiltration of lower limbs in DMD patients showes a distinct involvement pattern. IDEAL‐IQ technique is able to quantitatively and objectively evaluate the degree of fat infiltration of lower limbs in DMD, and it has great value in clinical application.