Liver MR Elastography at 3 T: Agreement Across Pulse Sequences and Effect of Liver R2* on Image Quality.

Abstract

The objectives of our study were to compare MR elastography (MRE) based on gradient-recalled echo (GRE) imaging with spin-echo echo-planar imaging (SEEPI) and rapid fractional (RF)-GRE MRE sequences at 3 T in terms of liver stiffness (LS) and image quality and to evaluate the effect of liver R2* on image quality. Eighty-one patients underwent 3-T liver MRE with GRE, SE-EPI, and RF-GRE sequences performed in variable order in this study. LS and ROI areas on the LS 95% confidence maps were compared among the three sequences. The relationship between liver R2* and ROI area was investigated. There was no significant difference in mean LS among the three sequences (p = 0.49). Mean ROI area was significantly larger for RF-GRE (18,213 ± 9292 [SD] mm²) than for GRE (13,196 ± 8149 mm²) and SE-EPI (12,896 ± 8656 mm²) (p < 0.0001). Liver R2* was significantly higher among patients with one or more failed sequences (mean ± SD, 116 ± 76 s^-1) than for patients with no failed sequences (59 ± 26 s^-1) (p = 0.001). Technical failure rates were 10% (8/81), 4% (3/81), and 2% (2/81) for GRE, SE-EPI, and RF-GRE, respectively. Among patients with iron overload (R2* ≥ 100 s^-1), there was a trend toward larger ROI area for SE-EPI (p = 0.09). SE-EPI-and RF-GRE-based MRE sequences provide equivalent measures of LS compared with GRE-based MRE, and both have lower technical failure rates. The RF-GRE sequence yielded the largest measurable area of LS. Among patients with iron overload, there was a trend toward larger measurable area of LS for the SE-EPI sequence.