title: Validation of a quantitative magnetic resonance method for measuring human body composition.
abstract: OBJECTIVE
  To evaluate a novel quantitative magnetic resonance (QMR) methodology (EchoMRI-AH, Echo Medical Systems) for measurement of whole-body fat and lean mass in humans.
  
  
  METHODS
  We have studied (i) the in vitro accuracy and precision by measuring 18 kg Canola oil with and without 9 kg water (ii) the accuracy and precision of measures of simulated fat mass changes in human subjects (n = 10) and (iii) QMR fat and lean mass measurements compared to those obtained using the established 4-compartment (4-C) model method (n = 30).
  
  
  RESULTS
  (i) QMR represented 18 kg of oil at 40 degrees C as 17.1 kg fat and 1 kg lean while at 30 degrees C 15.8 kg fat and 4.7 kg lean were reported. The s.d. of repeated estimates was 0.13 kg for fat and 0.23 kg for lean mass. Adding 9 kg of water reduced the fat estimates, increased misrepresentation of fat as lean, and degraded the precision. (ii) the simulated change in the fat mass of human volunteers was accurately represented, independently of added water. (iii) compared to the 4-C model, QMR underestimated fat and over-estimated lean mass. The extent of difference increased with body mass. The s.d. of repeated measurements increased with adiposity, from 0.25 kg (fat) and 0.51 kg (lean) with BMI <25 kg/m(2) to 0.43 kg and 0.81 kg respectively with BMI >30 kg/m(2).
  
  
  CONCLUSIONS
  EchoMRI-AH prototype showed shortcomings in absolute accuracy and specificity of fat mass measures, but detected simulated body composition change accurately and with precision roughly three times better than current best measures. This methodology should reduce the study duration and cohort number needed to evaluate anti-obesity interventions.
authors.affiliation: Clinical Unit Cambridge, GlaxoSmithKline Clinical Pharmacology and Discovery Medicine, Addenbrooke's Hospital, Cambridge, UK. Antonella.2.Napolitano@gsk.com
authors.forename: Antonella
authors.initials: A
authors.lastname: Napolitano
authors.forename: Sam R
authors.initials: SR
authors.lastname: Miller
authors.forename: Peter R
authors.initials: PR
authors.lastname: Murgatroyd
authors.forename: W Andrew
authors.initials: WA
authors.lastname: Coward
authors.forename: Antony
authors.initials: A
authors.lastname: Wright
authors.forename: Nick
authors.initials: N
authors.lastname: Finer
authors.forename: Tjerk W
authors.initials: TW
authors.lastname: De Bruin
authors.forename: Edward T
authors.initials: ET
authors.lastname: Bullmore
authors.forename: Derek J
authors.initials: DJ
authors.lastname: Nunez
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity; D001823:Body Composition; D015992:Body Mass Index; D001834:Body Water; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results