Hepatic stiffness estimated using 2D MRE has become the leading biomarker for liver fibrosis and thus has been advocated in assessment of NAFLD^{1, 2}. However, the standard 2D MRE imaging sequence used in most commercial implementations is a gradient-recalled-echo (GRE) sequence which may have a default echo time (TE) when fat and water signals are not in-phase³. Using TE times that are not in-phase can potential result in signal cancelation in patients with severe steatosis, thereby reducing signal-to-noise ratio (SNR) of computed wave images. Because tissue stiffness estimation accuracy depends on wave-image quality, choice of TE may affect hepatic stiffness estimation in patients with NAFLD. The purpose of our study was to compare in NAFLD patients hepatic stiffness estimation and wave-image quality of MRE with a default TE and MRE with TE at the nearest in-phase value.After obtaining informed consent/assent, adult and pediatric subjects with known or suspected NAFLD were prospectively enrolled. Hepatic proton-density fat fraction (PDFF), a biomarker for hepatic steatosis, was estimated with an advanced T1-independent, T2*-corrected multi-peak, fat-spectrum-modeled sequence⁴. Two 2D MRE scans were performed on a 3T GE HDxt MRI scanner with a motion-sensitized GRE sequence, one with a default TE value of 20.1 ms (default-TE), and with a nearest in-phase TE value of 20.6 ms (IP-TE)³. To evaluate wave-image quality objectively, a confidence map was generated depicting wave image goodness of fit to a smooth polynomial, pixel-by-pixel (i.e., R2)⁵. Confidence map values ranged from 0 to 1, with '1' indicating high quality wave data⁵. Using a custom software package (MRE/Quant, Mayo Clinic), an image analyst drew regions of interest (ROIs) on anatomic magnitude images to include only liver parenchyma, co-localized to the elastogram for both IP-TE and default-TE, and final ROIs were created separately for the two MRE methods by excluding values not meeting a confidence-map R2 threshold of 0.95. Mean hepatic stiffness within final ROIs, and final ROI sizes were recorded. Final ROI size represents the area of the liver producing good wave data where reliable hepatic stiffness measurements can be obtained, and was used as a quantitative measure of wave-image quality. Mean hepatic stiffness and ROI size between default-TE and IP-TE were compared using the pairwise Wilcoxon rank-sum test. The comparison was repeated for a subgroup of subjects with hepatic PDFF greater than 20%, for which water and fat signal cancelation is expected to be substantial. In addition, the relationship between PDFF and the difference in ROI size between IP-TE and default-TE was examined using Pearson's correlation.Fifty subjects (mean age 46 yrs, range 9-78 yrs, mean BMI 29 kg/m², range 20-51 kg/m²) were enrolled between 5/2015 and 9/2015 with hepatic PDFF ranging from 0.23% to 35%, and mean hepatic stiffness ranging from 1.61 kPa to 9.64 kPa. Overall, mean hepatic stiffness and ROI size were not different between IP-TE and default-TE (p=0.16 for hepatic stiffness, p=0.52 for ROI size). For the subgroup with hepatic PDFF greater than 20% (n = 12), ROI size was larger when using IP-TE compared to default-TE (5,380 voxels vs. 4,505 voxels; p = 0.0049), but mean computed hepatic stiffness was not different (2.36 kPa vs. 2.40 kPa; p = 0.1294). In addition, hepatic PDFF correlated positively with difference in ROI size between IP-TE and default-TE (r = 0.67, p < 0.0001).Hepatic stiffness estimation for the two MRE scans with different TEs are in excellent agreement, indicating that standard 2D MRE acquisition works well over a wide range of hepatic PDFF, and thus is useful in the assessment of NAFLD. For patients with moderate to severe steatosis, increasing to an IP-TE increased the area where accurate stiffness measurements can be obtained by roughly 16%. The positive correlation between PDFF and difference in ROI size suggests that this improvement in coverage of the liver is larger for higher PDFF. In summary, 2D MRE with an in-phase TE provides slightly higher wave-image quality in patients with high PDFF, and potentially may be advantageous for fibrosis assessment in NAFLD.