Fig. 1.

Muscle fat infiltration shown schematically in the semimembranosus of the mid-thigh. The T1w image provides good contrast and shows the individual muscles separated by perimuscular adipose tissue (orange) and intramuscular adipose tissue (red). However, the amount of visible intramuscular adipose tissue depends on the spatial resolution and smaller aggregations of intramuscular adipose tissue either cause partial volume artifacts or cannot be detected in T1w images at all. The muscle tissue (dark) contains contractile tissue, and lipids, either as EMCLs and IMCLs that contribute to the fat faction signal in Dixon images. (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)