RESUMO
Purpose To evaluate the fatty infiltration of lower limbs by using iterative decomposition of water and fat with asymmetry and least squares estimation quantitative fat imaging(IDEAL-IQ)technique in idiopathic inflammatory myopathy(IIM)patients,and to analyze the correlation between muscle fat fraction(FF)and clinical assessments.Materials and Methods Thirty-two patients with IIM were diagnosed by muscle biopsy and 32 age-,gender-matched healthy volunteers(control group)were recruited.T1WI,T2WI in axial view and IDEAL-IQ sequence of thighs were scanned on each subject.FF values of the anterior,interior and posterior thigh muscles were measured on the FF image generated in the IDEAL-IQ sequence,and medical research council scale score of the IIM group were collected.The difference of muscle FF value between the IIM group and control group was compared,the correlation between FF value and muscle strength of thigh muscles was also analyzed.Results The mean FF values of anterior,interior and posterior thigh muscles in IIM group were 16.60±3.67,6.77±4.92 and 17.32±4.01,respectively,which were significantly higher than those in control group(2.58±2.57,1.40±0.64 and 1.57±0.19),with statistically significant differences(t=-7.29,-6.91,-4.85;all P<0.05).Spearman test showed that the mean FF value was significantly correlated with course of disease(r=0.587,P<0.001).The mean FF values of anterior,interior and posterior thigh muscles were significantly correlated with muscle strength(r=-0.885,-0.761,-0.594;all P<0.001).Conclusion The IDEAL-IQ technique can quantitatively and objectively analyze the severity of muscle fat infiltration in IIM patients,and its degree is correlated with the muscle strength,which has significant clinical application value.