![]() A small Japanese study also reported that between 20 and 70 years the increase of intramuscular adipose tissue volume normalized to muscle volume was larger than the decrease of muscle cross-sectional area normalized to body weight. Ĭompared to young healthy subjects, in sarcopenic subjects IMAT volume of lower extremity tissues is increased and in older adults IMAT is associated with decreased mobility. ![]() An accurate separation of IMAT from muscle tissue of the thigh or calf requires a segmentation of the deep fascia lata (FL), a highly complex network of extracellular matrix and cells of mesenchymal and neural origin. A separation of IMCLs and EMCLs can be achieved by MR spectroscopy but not by MR imaging. However, their combined contribution to myosteatosis can be quantified indirectly from MRI Dixon sequences as fat fraction (FF) of MT. This component consists of small aggregates of adipocytes between muscle bundles and intramyocellular lipids. The second component of myosteatosis is not detectable (invisible) in T1-weighted MR images. Intramuscular fat may be deposited in two distinct compartments, either as intramyocellular lipids (IMCLs) accumulated in the cytoplasm of myocytes or as extramyocellular lipids (EMCLs) in interstitial, intramyofascial adipocytes. Traditionally, radiologists assessed muscle fat infiltration by semi quantitatively grading IMAT of the thigh or calf using CT or MR images. In T1-weighted MR (magnetic resonance) images the signal intensity of IMAT appears white whereas the signal intensity of the complement of IMAT, which is termed muscle tissue (MT) appears dark. The first one is IMAT (intermuscular adipose tissue) defined as "visible storage of lipids in adipocytes located between the muscle fibers (also termed intramuscular fat) and also between muscle groups (literally intermuscular)”. For the purpose of this study, two components are differentiated. Myosteatosis of the thigh for example, includes the adipose tissue and lipids beneath the fascia lata. ![]() Myosteatosis (skeletal muscle fat infiltration) is another important component of mobility and muscle strength, which is highly associated with muscle fat fraction. In older adults, the age-related decrease of muscle strength is about three times as high as the decrease of appendicular lean mass measured by dual X-ray absorptiometry (DXA), which is a surrogate of muscle mass. However, muscle strength is not just a function of muscle volume. A decrease in muscle volume is associated with a decrease of muscle strength and consequently of physical function. According to the latest definition of the European Working Group on Sarcopenia in Older People 2 (EWGSOP2), muscle quantity and quality are part of the sarcopenia case-finding algorithm.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |