title: Relaxation effects in MRI-based quantification of fat content and fatty acid composition.
abstract: OBJECTIVE
  To investigate various sources of bias in MRI-based quantification of fat fraction (FF) and fatty acid composition (FAC) using chemical shift-encoded techniques.
  
  
  METHODS
  Signals from various FFs and FACs and individual relaxation rates of all signal components were simulated. From these signals, FF and FAC parameters were estimated with and without correction for differences in individual relaxation rates. In addition, phantom experiments were conducted with various flip angles and number of echoes to validate the simulations.
  
  
  RESULTS
  As expected, T(1) weighting resulted in an overestimation of the FF, but had much smaller impact on the FAC parameters. Differences in T(2) values of the signal components resulted in overestimation of the FAC parameters in fat/water mixtures, whereas the estimation in pure oil was largely unaffected. This bias was corrected using a simplified signal model with different T(2) values of water and fat, where the accuracy of the modeled T(2) of water was critical. The results of the phantom experiment were in agreement with simulations.
  
  
  CONCLUSIONS
  T(1) weighting has only a minor effect on FAC quantification in both fat/water mixtures and pure oils. T(2) weighting is mainly a concern in fat/water mixtures but may be corrected using a simplified model.
authors: Department of Medical Radiation Physics, Malmö, Department of Clinical Sciences, Malmö, Lund University, Skåne University Hospital, Malmö, Sweden.
authors: Pernilla
authors: P
authors: Peterson
authors: Jonas
authors: J
authors: Svensson
authors: Sven
authors: S
authors: Månsson
mesh_terms: D000273:Adipose Tissue / Q000737:chemistry*; D003198:Computer Simulation; D005227:Fatty Acids / Q000737:chemistry*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D019047:Phantoms, Imaging
chemical_list: D005227:Fatty Acids
keywords: chemical shift; fat quantification; fatty acid composition; magnetic resonance; relaxation; water-fat imaging