Fig. 6

Muscle imaging grading (Wattjes et al. 2010; Heckmatt et al. 1982; Cotta et al. 2014, and personal files). Each line shows the comparative muscle grading and each column represents different imaging modalities: MRI (magnetic resonance imaging) (a, d, g, j, and m), CT (computed tomography) (b, e, h, k, and n), and US (ultrasound) (c, f, i, l, and o). Mercuri scale is divided in grades 1 to 4; grade 1: normal appearance, 2: mild involvement of less than 30% of the volume of the individual muscle, 3: moderate involvement of 30–60% of the volume of the individual muscle, 4: severe involvement with washed out appearance. Fischer scale is divided in grades 0 to 4; grade 0: normal appearance; 1: mild traces of involvement; 2: moderate involvement of less than 50% of the muscle; 3: severe involvement of more than 50% of the muscle; 4: end-stage appearance. Ultrasound grading according to Heckmatt scale: grade (1): normal (c); (2): increased muscle echo while bone echo (blue arrow in f) is distinct; (3): marked increase in muscle echo, and reduced bone echo (i, and l); and (4): very strong muscle echo and complete loss of bone echo (o). Each line represents the same grade of muscle fat replacement: Mercuri 1/ Fischer 0/ Heckmatt (1) (arrows in a, b, and c); Mercuri 1/ Fischer 1/ Heckmatt (2) (arrows in d, e, and f); Mercuri 2/ Fischer 2/ Heckmatt (3) (arrows in g, h, and i); Mercuri 3/ Fischer 3/ Heckmatt (3) (arrows in j, k, and l); and Mercuri 4/ Fischer 4/ Heckmatt (4) (arrows in m, n, and o)