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Abstract #0211

On the Definition of Fat-Fraction for in Vivo Fat Quantification with Magnetic Resonance Imaging

Scott B. Reeder1,2, Catherine DG Hines1,3, Huanzhou Yu4, Charles A. McKenzie5, Jean H. Brittain6

1Radiology, University of Wisconsin, Madison, WI, USA; 2Medical Physics, University of Wisconsin, Madison, WI, USA; 3Biomedical Engineering, University of Wisconsin, Madison, WI, USA; 4Applied Science Laboratory, GE Healthcare, Menlo Park, CA, USA; 5Medical Biophysics, University of Western Ontario, London, Ontario, Canada; 6Applied Science Laboratory, GE Healthcare, Madison, WI, USA

The most commonly used metric for fat quantification with MRI is fat-signal-fraction. After correction for confounding factors (eg. T2*-decay, etc) fat-signal-fraction is synonymous with fat-proton-density-fraction. Unfortunately, gold standard assays used to validate MRI provide estimates of fat-volume-fraction or fat-mass-fraction. The purpose of this work is to clarify fat-fraction definitions, and to estimate fat-volume-fraction and fat-mass-fraction from separated fat/water signals. Theory and experiment demonstrate that for fat, signal-fraction is equivalent to volume-fraction and mass-fraction. The same is not true, however, for other combinations of chemical species such as acetone and water, which require correction factors to determine volume or mass fraction.