Chulhyun Park, Presenter: Nothing to Disclose

Eduardo Almeida Cunha Costa MD, Abstract Co-Author: Nothing to Disclose

Kevin Amir Zand MD, Abstract Co-Author: Nothing to Disclose

Lisa Clark MPH, PhD, Abstract Co-Author: Nothing to Disclose

Gavin Hamilton PhD, Abstract Co-Author: Nothing to Disclose

Rohit Loomba MD, MSc, Abstract Co-Author: Nothing to Disclose

Claude B. Sirlin MD, Abstract Co-Author: Research Grant, General Electric Company Speakers Bureau, Bayer AG Consultant, Bayer AG

Michael Simca Middleton MD, PhD, Abstract Co-Author: Consultant, Allergan, Inc Institutional research contract, Bayer AG Institutional research contract, sanofi-aventis Group Institutional research contract, Isis Pharmaceuticals, Inc Institutional research contract, Johnson & Johnson Institutional research contract, Synageva BioPharma Corporation Institutional research contract, Takeda Pharmaceutical Company Limited Stockholder, General Electric Company Stockholder, Pfizer Inc Institutional research contract, Pfizer Inc

To compare hepatic proton density fat fraction (PDFF) accuracy using low- and high-flip angle (FA) 6-echo magnitude-based magnetic resonance imaging (MRI), before and after administration of gadoxetic acid (Gx), using pre-contrast magnetic resonance spectroscopy (MRS) as reference.

This prospective, cross-sectional, observational single-center study was IRB approved and HIPAA complaint. Adults with known or suspected non-alcoholic fatty liver disease (NAFLD) undergoing 3T clinical Gx-enhanced liver MRI were enrolled. Magnitude-based MRI at low-FA (10°) and high-FA (50°) was obtained pre-Gx and during the hepatobiliary phase to estimate PDFF, with FAs in random order to eliminate time-point bias. Pre- and post-Gx advanced MRS (using multiple TRs and TEs, to measure T1) was obtained from a voxel in the right hepatic lobe. Accuracy of MRI PDFF, co-localized to the MRS voxel location, was assessed by regression analysis using pre-Gx MRS as reference. Pre- and post-Gx hepatic water and fat T1 values were estimated from MRS.

Twenty-eight adult subjects were enrolled after obtaining written informed consent. Linear regression slope, intercept, and R2 of MRI-PDFF as a function of MRS-PDFF were, respectively: 1.06, 0.90%, and 0.98 pre-Gx at FA 10°; 1.05, 0.92%, and 0.99 post-Gx at FA 10°; 0.73, 0.06%, and 0.98 pre-Gx at FA 50°; and 1.04, 0.37%, and 0.99 post-Gx at FA 50°. Mean hepatic water and fat T1 values by MRS were 927 and 356 msec pre-Gx, and 361 and 347 msec post-Gx, respectively.

Low-FA magnitude multi-gradient-echo MRI estimates hepatic PDFF pre- and post-Gx accurately. High-FA magnitude MRI overestimates PDFF pre-Gx due to T1 bias from fat protons having shorter T1 values than water protons, but accurately estimates PDFF post-Gx because Gx preferentially relaxes water protons, causing T1 values of both water and fat to be similar, thus reducing T1 bias.

Post-Gx MRI at high FA allows accurate PDFF estimation with improved signal-to-noise, and higher resolution which may enable detection and characterization of fatty or fat-sparing focal liver lesions.

Park, C, Costa, E, Zand, K, Clark, L, Hamilton, G, Loomba, R, Sirlin, C, Middleton, M, Effect of Intravenous Gadoxetic Acid and Flip Angle on Hepatic Proton Density Fat Fraction (PDFF) Estimation with Magnitude Multi-echo Gradient-echo MR Imaging at 3T.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14012005.html