Among the noninvasive modalities used for quantification of liver fat,
chemical shift–encoded (CSE) MRI–based proton density fat
fraction (PDFF) mapping has the best combination of accuracy, precision, and
reproducibility in the measurement of liver fat content. Estimation of
hepatic fat content using US is based on increased echogenicity and sound
attenuation and has low accuracy for detection of mild-to-moderate
steatosis. Decreased x-ray attenuation (Hounsfield units) on noncontrast CT
scans can be used to quantify liver fat and correlates closely and linearly
with MRI PDFF. CSE MRI generates confounder-corrected volumetric
quantitative maps of PDFF, a fundamental property of tissue. (A,
D) Conventional US images, (B, E) noncontrast CT
images, and (C, F) MRI PDFF maps in 44-year-old man (patient 1)
with mild-to-moderate hepatic steatosis (MRI PDFF = 12%, CT attenuation = 43
HU) and 59-year-old woman (patient 2) without steatosis (MRI PDFF = 2%, CT
attenuation = 65 HU).