For this reason, the ROI placement approach for analysis of quantitative PDFF and R2* maps needs to be standardized. This lack of standardization introduces an additional element of variability across sites and studies, impacting the widespread dissemination of these techniques as reproducible and repeatable quantitative imaging biomarkers. As a result, recent studies conducted at different sites have used a wide range of ROI sizes (from 0.785 cm 2 to the whole liver), locations (left and right lobes anterior, posterior, and lateral segments Couinaud segments whole liver), and number (one to nine ROIs) for measurements of liver PDFF and R2*. Despite the growing clinical and research interest in these techniques, a standardized approach for ROI-based measurements has not been established. The typical workflow for these techniques includes acquisition of CSE MRI data (typically a single 20-s breath-hold with whole-liver 3D acquisitions), reconstruction of PDFF and R2* maps from the CSE MRI data, and placement of ROIs on the PDFF and R2* maps to obtain quantitative estimates of the fat and iron content in the liver, respectively.

R2*-based liver iron quantification enables the noninvasive assessment of diseases that result in liver iron overload, including hereditary hemochromatosis, and blood transfusion–dependent conditions such as thalassemia, sickle cell disease, and bone marrow failure. Further, these techniques allow the simultaneous estimation of fat- and noise-corrected liver iron content using R2* (1 / T2*) quantification from the same acquired CSE MRI data.

PDFF-based liver fat quantification enables the noninvasive assessment of hepatic steatosis, the hallmark histologic feature of nonalcoholic fatty liver disease, which is estimated to affect 20–30% of the Western population.

Emerging measurements of proton density fat fraction (PDFF) in the liver based on chemical shift–encoded (CSE) MRI have shown great promise as quantitative imaging biomarkers for noninvasive detection, quantitative grading, and treatment monitoring of hepatic steatosis.

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