The Application Study Of Magnetic Resonance Imaging In Primary Skeletal Muscle Diseases

Part 1 The diagnostic value of conventional MRI and susceptibility weighted imaging in patients with primary skeletal muscle diseasesOBJECTIVETo study the diagnostic value of conventional MRI and susceptibility weighted imaging(SWI)in patients with primary skeletal muscle diseases.METHODSA total of 83 patients with primary skeletal muscle diseases were recruited,including 23 cases of muscular dystrophy(9 cases of pseudohypertrophy muscular dystrophy,6 cases of limb-girdle muscular dystrophy and 8 cases of facioscapulohumeral muscular dystrophy),10 metabolic myopathy(6 cases of lipid storage myopathy and 4 cases of glycogen sedimentary myopathy)and 50 inflammatory myopathy(31 cases of dermatomyositis and polymyositis,11 cases of immune-mediated necrotizing myopathy and 8 cases of inclusion body myositis).Conventional MRI scans were performed in all patients and SWI scans were performed in 41 patients.Fat infiltration score and edema score were performed in 24 muscles of bilateral thigh in all patients.Degree of angiogenesis was evaluated in 41 patients.We then compared fat infiltration score,edema score and angiogenesis score among the three groups of muscular dystrophy,inflammatory myopathy and metabolic myopathy.The distribution characteristics of muscle involvement in each subtype of muscular diseases were further analyzed.RESULTS1.The fat infiltration score of the muscular dystrophy group and metabolic myopathy group were higher than those of the inflammatory myopathy group(muscular dystrophy,P<0.001;metabolic myopathy P=0.008).And the edema score in both groups were lower than those in the inflammatory myopathy group(P<0.001).The angiogenesis score of muscular dystrophy group was higher than that of metabolic myopathy group and inflammatory myopathy group(P<0.001).2.Gluteus maximus had the most frequent and greatest degree of fatty infiltration in pseudohypertrophy muscular dystrophy and limb-girdle muscular dystrophy.The difference between the two groups was that the anterior group were most seriously affected than the posterior group in pseudohypertrophy muscular dystrophy.In facioscapulohumeral muscular dystrophy,asymmetric distribution was presented in bilateral thigh muscle,and the posterior grouphad the most frequent and greatest degree of fatty infiltration.Gracilis and sartorius were the lowest frequency and the least affected degree of fat infiltration inthe three subtypes.3.Quadriceps had the most frequent and greatest degree of edema in dermatomyositis and polymyositis.Rectus femoris and vastus lateralis muscles present severe edema compared to vastus medius and vastus medius in immune-mediated necrotizing myopathy.In inclusion body myositis,quadriceps femoris had the most frequent and greatest degree of edema and fatty infiltration.4.The posterior groupand gluteus maximus had the most frequent and greatest degree of fatty infiltration in metabolic myopathy.CONCLUSIONTypes of muscular diseases have the features of signal and muscle involvement distribution and conventional MRI and SWI can be helpful for the diagnoses of primary skeletal muscle diseases.Part 2 Inflow-based vascular-space-occupancy magnetic resonance imaging measures arteriolar muscular blood volume in dermatomyositisOBJECTIVEThis study aimed to determine whether inflow-based vascular-space-occupancy(iVASO)MRI could reproducibly quantify skeletal muscle perfusion and identify patients with dermatomyositis(DM).METHODS25 patients with DM and 22 healthy volunteers underwent iVASO in a 3T MR scanner.Maximum arteriolar muscular blood volume(MBVa_max)and mean MBVa(MBVa_mean)of four subgroups of muscles(normal muscles,morphologically-normal appearing muscles,edematous muscles,and atrophic or fat-infiltrated muscles)were obtained.MBVa_max and MBVa_mean among the different subgroups were compared,and repeat testing was performed in 20 subjects for assessment of reproducibility.RESULTS1.Compared to normal muscles in normal subjects(MBVa_max=1.443 ml/100ml;MBVa_mean=1.219 ml/100ml),morphologically-normal appearing muscles(MBVa_max=1.176ml/100ml;MBVa_mean=1.059ml/100ml),edematous muscles(MBVa_max=1.125ml/100ml;MBVa_mean=1.013ml/100ml),and atrophic or fat-infiltrated muscles(MBVa_max=0.669 ml/100ml;MBVa_mean=0.446ml/100ml)in DM patients showed a significant decrease of MBVa(p<0.001).Both MBVa_max and MBVa_mean of atrophic or fat-infiltrated muscles were significantly lower than morphologically-normal appearing muscles and edematous muscles(p<0.001).2.As a measure of test-retest studies,the ICC was 0.990(95%confidence interval[CI]:0.986 to 0.993)and 0.990(95%CI:0.987 to 0.993)for MBVa_max and MBVa_mean,respectively.For interobserver reproducibility,the ICC was 0.989(95%CI:0.986 to 0.991)and 0.980(95%CI:0.975 to 0.983)for MBVa_max and MBVa_mean,respectively.CONCLUSIONiVASO can reproducibly quantify thigh muscular arteriolar blood volume,and is able to discriminate between normal volunteers and patients with DM.