Cross vendor comparison of gradient recalled echo (GRE) and spin echo-echo planar imaging (SE-EPI) based MR elastography of the liver at 3T.
Suraj D Serai1, Jonathan R Dillman1, Hui Wang2, and Andrew T Trout1

1Radiology, Cincinnati Children's Hospital, Cincinnati, OH, United States, 2Philips Healthcare, Cincinnati, OH, United States


MR elastography (MRE) allows non-invasive evaluation of hepatic stiffness and samples a larger area of the liver than liver biopsy. The high accuracy of MRE for liver fibrosis staging suggests that MRE could potentially replace liver biopsy. MRE has traditionally been performed using a GRE sequence. GRE, however, has SNR limitations at higher field strengths that can result in under-sampling potentially leading to erroneous stiffness values. SE-EPI is an alternative means of performing MRE that has higher SNR, lower susceptibility related signal loss and increased speed. In this work, we compared GRE and SE-EPI MRE across two vendor platforms.


As MRE gains acceptance, it is important to confirm that liver stiffness values obtained by different sequences and on different vendor platforms are reproducible. The aim of this study was to compare GRE and SE-EPI MRE on volunteers on two different vendor platform 3T MRI scanners performed on the same day.


16 volunteers (6 hours fasting status) were recruited under an approved IRB for liver MRE scans. All subjects were imaged in one session using both GRE and SE-EPI MRE on two 3T MRI scanners (750W, GE Healthcare, Waukesha, WI, USA and Philips Ingenia, Best, Netherlands). All scan parameters were identical on the two platforms to the best extent possible (Representative image in Figure 1). The subjects did not eat or drink between the two MRE exams in order to avoid postprandial hepatic blood flow. MRE scans were done using a 16-channel torso coil and identical active driver amplitudes and frequency (60 Hz). The initiation and cessation of the vibrations were controlled by the MR pulse sequence programmed and embedded as part of the scanner software. GRE MRE was acquired in 4 breath holds of 15 seconds each and SE-EPI MRE was acquired in a single breath hold of 15 seconds. Four axial slices through the liver were obtained for each sequence. MR elastogram maps were generated using a multimodal direct inversion (MMDI) algorithm (Mayo Clinic, Rochester, MN) with liver stiffness calculated as a mean of mean stiffness measured on each slice (kPa), measured by a single observer. Mean liver stiffness values across the two platforms and between GRE versus SE-EPI MRE sequences were compared using Bland-Altman difference plots. Pearson’s correlation coefficient was used to assess correlation between stiffness values obtained within and across scanners. Mean liver stiffness values between the two platforms were compared using interclass correlation coefficients (ICC). Area of the sampled regions of interest was also recorded and compared with a paired t-test.


Mean subject age was 39.2 years (range: 22.7-55.3 years) and 69% were female. Mean liver stiffness values measured on the GE scanner were 1.98 ± 0.4 kPa by GRE MRE and 2.06 ± 0.3 kPa by SE-EPI MRE and were highly correlated (R = 0.9). Similarly mean liver stiffness values on the Philips scanner were 1.83 ± 0.3 kPa by GRE MRE and 1.85 ± 0.3 kPa by SE-EPI MRE and were highly correlated (R = 0.9). Sampled areas were 6174 ± 2197 mm2 for GRE MRE and 9915 ± 2721 mm2 for SE-EPI MRE on the GE MRI scanner and were 8392 ± 4666 mm2 for GRE MRE and 14540 ± 4490 mm2 for SE-EPI MRE on the Philips MRI scanner. For both scanners, SE-EPI allowed sampling of significantly larger areas (p<0.001). Stiffness measurements by both GRE MRE and SE-EPI MRE were highly reproducible across the two scanner platforms. ICC was 0.85 (95% confidence interval: 0.58 – 0.95) for GRE MRE and 0.84 (95% confidence interval: 0.52 – 0.94) for SE-EPI MRE. For both sequences, Bland-Altman analysis shows all values falling within two standard deviations (Figure 2A and 2B). Bland-Altman analysis of GRE MRE versus SE-EPI MRE, independent of vendor, demonstrates a bias of 0.06 kPa (standard deviation = 0.41 kPa) between techniques with all values falling within 95% prediction limits (Figure 3) with the exception of a single outlier. Scatter plots show stiffness values and across scanners (GE and Philips) (Figure 4) and within scanners (GRE and SE-EPI) (Figure 5); all stiffness values fell within 95% agreement with the line of equality.


Liver MRE is a promising non-invasive quantitative imaging tool used to determine liver stiffness in the assessment of patients with chronic liver disease. As MRE becomes more widespread in its availability and usage, and as more vendor platforms become approved for routine clinical determination of liver stiffness, it is imperative that cross vendor validation studies be performed to ensure that liver stiffness values are consistent across different platforms. This consistency will ensure that surveillance exams can be performed on individual patients with chronic liver disease at different facilities, with different MR platforms, but without concern for variation in liver stiffness results secondary to purely technical factors. In this pilot investigation, we demonstrate that there is strong agreement in measured hepatic stiffness among two vendor scanners at 3T and between GRE and SE-EPI MRE sequences with minimal bias (0.06 kPa) between techniques. SE-EPI MRE has the advantage of sampling a larger area of the liver and can be performed in a single breath hold.


No acknowledgement found.


1. Xanthakos SA, Podberesky DJ, Serai SD, Miles L, King EC, Balistreri WF, Kohli R (2014) Use of magnetic resonance elastography to assess hepatic fibrosis in children with chronic liver disease. The Journal of pediatrics 164 (1):186-188. doi:10.1016/j.jpeds.2013.07.050 13.

2. Yin M, Talwalkar JA, Glaser KJ, Manduca A, Grimm RC, Rossman PJ, Fidler JL, Ehman RL (2007) Assessment of hepatic fibrosis with magnetic resonance elastography. Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association 5 (10):1207-1213.e1202. doi:10.1016/j.cgh.2007.06.012


Representative GRE and SE-EPI images. Left column shows GRE images and right column shows SE-EPI images. Top row shows magnitude images and bottom row show elastogram maps.

Bland Altman plot shows strong correlation between values obtained by GRE MRE (A) and SE-EPI MRE (B) from two different 3T MR vendor platforms.

Bland Altman plot shows strong correlation between values obtained by Gradient Echo MRE and Spin echo EPI MRE.

Scatter plot show that all GRE MRE (A) and SE-EPI MRE (B) studies from both scanners fall within 95% prediction limits (r=0.9; r2=0.9).

Scatter plot show that all GRE MRE and SE-EPI MRE studies fall within 95% prediction limits. (Solid Blue line denotes line of equality and dotted red line denotes 95% acceptance limits.)

Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)