Comparison of spin-echo echo-planar imaging magnetic resonance elastography with gradient-recalled echo magnetic resonance elastography and their correlation with transient elastography

Abstract

PURPOSE This study aimed to assess the agreement between liver stiffness (LS) values obtained by the gradient-recalled echo (GRE) magnetic resonance elastography (MRE) and spin-echo echo-planar imaging (SE-EPI) MRE with those of transient elastography (TE), respectively. METHODS We retrospectively included 48 participants who underwent liver MRE with both GRE and SE-EPI sequences in the same session and also TE within 1 year. We obtained LS values for MRE by drawing free-hand region of interest, and TE was performed using a FibroScan device. We assessed the relationship between the mean LS values obtained by each MRE sequence and TE using the correlation coefficients and Bland-Altman plots, respectively. We also compared LS values and technical failure rates of measured values from MRE between SE-EPI and GRE sequences using the paired t-test and McNemar's test. The MRE failure was defined as the absence of pixel value with a confidence index above 95%. RESULTS The LS values from SE-EPI and GRE sequences strongly correlated with those from TE (GRE; r = 0.73, P < .001 vs. SE-EPI; r = 0.79, P < .001). In addition, the LS values from the 2 MRE sequences showed excellent relationship (intraclass correlation coefficient, 0.94 [0.89-0.97], P < .001). The LS values from SE-EPI and GRE MRE were not significantly different (4.14 kPa vs. 3.88 kPa, P = .19). Furthermore, the technical success rate of SE-EPI MRE was superior to that of GRE (100% vs. 83.8%, P = .031). CONCLUSION The measured LS values obtained using TE correlated strongly with those obtained using GRE and SE-EPI MRE techniques, even though SE-EPI-MRE resulted a higher technical success rate than GRE-MRE. Therefore, we believe that TE, GRE, and SE-EPI MR elastography techniques may complement each other according to the appropriate individual situation.

Figure 1. a-c.

Bland–Altman plots (a-c) are generated with data from mean liver stiffness values based on GRE and SE-EPI MRE sequences and TE; the dotted red lines indicate 1.96 standard deviations above and below the mean and the solid green whiskers indicate the 95% prediction limits of the standard deviations and the pink line indicates the regression line. MRE, magnetic resonance elastography; GRE, gradient recalled echo; SE-EPI, spin-echo echo-planar imaging; TE, transient elastography; SD, standard deviation.

Figure 2. a-d.

A 60-year-old man with multiple hepatocellular carcinomas in the liver. Representative GRE and SE-EPI MRE color elastogram (a, c) and gray-scale elastogram (b, d) images showed no significant difference between liver stiffness values measured from GRE MRE (a, b) and SE-EPI MRE (c, d). The reliable area for measurement, without checkerboard pattern, is significantly larger with the elastogram (c, d) using SE-EPI sequence than those with the GRE sequence (a, b), reflecting stability and reliability of the examination.

Figure 3. a-d.

A 67-year-old man with alcoholic liver cirrhosis. Wave image (a) acquired during liver MRE examination using a 2-dimensional GRE sequence show irregular and bizarre pattern of the shear wave, likely indicating technical failure. However, wave image (c) acquired using a 2-dimensional SE-EPI sequence in the same patient show relatively regular and well-stratified shear wave indicating technical success. Furthermore, there is no pixel value with a confidence index higher than 95% in gray-scale elastogram (b) using GRE MRE when compared with elastogram (d) using SE-EPI MRE. The patient’s automatically calculated R2* (1/T2*) value from a 3-dimensional multi-echo Dixon sequence (LiverLab, Siemens Healthcare) was 187.5/s which indicates iron deposition and also is known to result in a higher technical failure rate in GRE MRE.