Quantitative muscle MRI and ultrasound for facioscapulohumeral muscular dystrophy: complementary imaging biomarkers

Fig. 1. a MR image of left upper leg with a region of interest drawn for a normal looking rectus femoris muscle. b The corresponding ultrasound image to a. c MR image of left upper leg with a region of interest drawn for a dystrophic rectus femoris muscle. d The corresponding ultrasound image to c. S: sartorius; G: gracilis; VM: vastus medialis; VI: vastus intermedius; VL; vastus lateralis; AL: adductor longus; AM: adductor magnus

Fig. 2. Correlation between quantitative MRI (fat fraction) and ultrasound (z-score) for the mean values of all muscles and for each muscle separately. The fat fractions and z-scores for the total legs were calculated by averaging the scores for the ten muscles measured. Dotted lines indicate limits of values that are considered normal. CC: correlation coefficient

Fig. 3. a, b Images of the right vastus lateralis, appearing normal on MRI (fat fraction 6%) but showing textural changes tissue texture changes (an increased amount of short linear reflective structures) on ultrasound images, resulting in a high echo intensity (z-score 3.4). c, d MRI of the left gastrocnemius medialis that is completely fatty infiltrated (fat fraction 74%) and the corresponding ultrasound image that shows a low echo intensity (resulting in a normal z-score of 0.6), but a disturbed architecture of the muscle tissue. e, f MRI of the right vastus lateralis with focal fatty infiltration (fat fraction 21%) and the corresponding ultrasound image, capturing only the fatty infiltrated part of the muscle (z-score 7.1)