title: Comparison of MRI and DXA to measure muscle size and age-related atrophy in thigh muscles.
abstract: OBJECTIVE
  Magnetic resonance imaging (MRI) and dual-energy x-ray absorptiometry (DXA) were used to examine the thigh lean mass in young and old men and women.
  
  
  METHODS
  A whole-body DXA scan was used to estimate thigh lean mass in young (20 men; 22.4±3.1y; 18 women; 22.1±2.0y) and older adults (25 men; 72.3±4.9y; 28 women; 72.0±4.5y). Thigh lean mass determined with a thigh scan on the DXA or full thigh MRI scans were compared.
  
  
  RESULTS
  Although the thigh lean mass quantified by DXA and MRI in young and older participants were correlated (R(2)=0.88; p<0.001) the magnitude of the differences in thigh lean mass between young and old was smaller with DXA than MRI (old vs. young men 79.5±13.1% and 73.4±11.2%; old vs. young women 88.6±11.8% and 79.4±12.3%, respectively). Detailed analysis of MRI revealed 30% smaller quadriceps muscles in the older than young individuals, while the other thigh muscles were only 18% smaller.
  
  
  CONCLUSIONS
  DXA underestimates the age-related loss of thigh muscle mass in comparison to MRI. The quadriceps muscles were more susceptible to age-related atrophy compared with other thigh muscles.
authors.affiliation: School of Healthcare Science, Manchester Metropolitan University, John Dalton Building, Oxford Road, Manchester, United Kingdom.
authors.forename: T M
authors.initials: TM
authors.lastname: Maden-Wilkinson
authors.forename: H
authors.initials: H
authors.lastname: Degens
authors.forename: D A
authors.initials: DA
authors.lastname: Jones
authors.forename: J S
authors.initials: JS
authors.lastname: McPhee
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D000375:Aging / Q000473:pathology*; D001284:Atrophy; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D052097:Quadriceps Muscle / Q000473:pathology*; D055815:Young Adult