title: Fat quantification using multiecho sequences with bipolar gradients: investigation of accuracy and noise performance.
abstract: OBJECTIVE
  To investigate the accuracy and noise performance of fat quantification with multiple gradient-echo images acquired using bipolar read-out gradients and compare them with those of the well-established unipolar technique.
  
  
  BACKGROUND
  The bipolar read-out technique induces phase and amplitude errors caused by gradient delays, eddy currents, and frequency-dependent coil sensitivity. In this study, these errors were corrected for jointly with the fat/water separation by modeling the impact of these effects on the signal. This approach did not require acquisition of reference data or modification of the pulse sequence.
  
  
  METHODS
  Simulations and a phantom experiment were used to investigate the accuracy and noise performance of the technique and compare them with those of a well-established technique using unipolar read-out gradients. Also, the in vivo feasibility was demonstrated for abdominal applications.
  
  
  RESULTS
  The phantom experiment demonstrated similar accuracy of the bipolar and unipolar fat quantification techniques. In addition, the noise performance was shown not to be affected by the added estimations of the phase and amplitude errors for most inter-echo times.
  
  
  CONCLUSIONS
  The bipolar technique was found to provide accurate fat quantification with noise performance similar to the unipolar technique given an appropriate choice of inter-echo time.
authors: Department of Medical Radiation Physics, Lund University, Skåne University Hospital, Malmö, Sweden.
authors: Pernilla
authors: P
authors: Peterson
authors: Sven
authors: S
authors: Månsson
mesh_terms: D050153:Abdominal Fat / Q000033:anatomy & histology*; D000465:Algorithms; D003198:Computer Simulation; D005240:Feasibility Studies; D006801:Humans; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008954:Models, Biological; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D014894:Weights and Measures
keywords: bipolar gradient; chemical shift; eddy currents; fat quantification; magnetic resonance imaging; multiecho