Objective: The purpose of the study was to quantify the fat fraction in nine fat-water phantoms containing 0-80% fat using opposed-phase imaging with the qualitative guidance of 1H MR spectroscopy (MRS), which was used by observer 1 to visually assess the sizes of the water and fat peaks to apply two alternative mathematic formulas for the calculation of the fat fraction. In addition, the fat fraction was also quantified directly with 1H MRS as an independent method by two observers (observers 2 and 3).
Conclusion: The fat fraction calculated with opposed-phase imaging (FF(OPI)) and that calculated with 1H MRS (FF(MRS)) correlated well with the known fat fractions of the phantoms (FF(P)): r = 0.99 for FF(OPI); p < 0.0001 and r = 0.96-0.98 for FF(MRS); p < 0.001, for observers 2 and 3, respectively. Opposed-phase imaging should be combined with 1H MRS to ensure accurate quantification of the fat fraction.