Free-breathing radial magnetic resonance elastography of the liver in children at 3 T: a pilot study

Abstract

Background Magnetic resonance (MR) elastography of the liver measures hepatic stiffness, which correlates with the histopathological staging of liver fibrosis. Conventional Cartesian gradient-echo (GRE) MR elastography requires breath-holding, which is challenging for children. Non-Cartesian radial free-breathing MR elastography is a potential solution to this problem. Objective To investigate radial free-breathing MR elastography for measuring hepatic stiffness in children. Materials and methods In this prospective pilot study, 14 healthy children and 9 children with liver disease were scanned at 3 T using 2-D Cartesian GRE breath-hold MR elastography (22 s/slice) and 2-D radial GRE free-breathing MR elastography (163 s/slice). Each sequence was acquired twice. Agreement in the stiffness measurements was evaluated using Lin’s concordance correlation coefficient (CCC) and within-subject mean difference. The repeatability was assessed using the within-subject coefficient of variation and intraclass correlation coefficient (ICC). Results Fourteen healthy children and seven children with liver disease completed the study. Median (±interquartile range) normalized measurable liver areas were 62.6% (±26.4%) and 44.1% (±39.6%) for scan 1, and 60.3% (±21.8%) and 43.9% (±44.2%) for scan 2, for Cartesian and radial techniques, respectively. Hepatic stiffness from the Cartesian and radial techniques had close agreement with CCC of 0.89 and 0.94, and mean difference of 0.03 kPa and −0.01 kPa, for scans 1 and 2. Cartesian and radial techniques achieved similar repeatability with within-subject coefficient of variation=1.9% and 3.4%, and ICC=0.93 and 0.92, respectively. Conclusion In this pilot study, radial free-breathing MR elastography was repeatable and in agreement with Cartesian breath-hold MR elastography in children.

Individualized driver amplitude in liver MR elastography: a linear regression study

“…Consequently, the determination of individualized amplitudes presents a critical clinical challenge. Building upon previous research and our own experience, we contend that liver MRE images should aim for optimal pMLV (3,13,14) and minimize AMVR. In this study, we employed driver amplitude-related variables to develop an optimal linear regression model, which holds the potential to enhance the quality and efficiency of hepatic MRE examinations and may address the historical inadequacies in driver amplitude settings in past research (Fig.…”

Rapid MR elastography of the liver for subsecond stiffness sampling

“…Other k-space sampling schemes for fast GRE MRE, such as radial readout, have been proposed and are currently being tested. 42 The fact that SE-EPI-MRE could not resolve a difference in stiffness between the end of inspiration and end of expiration may be attributable to the long scan time and breath-hold phases (21 s vs. 10 s in our breathing experiment) (Figure 4), which averages out temporal effects. Because THE is a rapid method for stiffness measurement (1 s acquisition time), it has been used as a robust tool to test physiologic effects in elastography.…”

“…SE‐EPI‐MRE is more susceptible to off‐resonance‐related distortion artifact than segmented spiral readout sequences, 40,41 whereas the latter are more susceptible to blurring artifacts. Other k‐space sampling schemes for fast GRE MRE, such as radial readout, have been proposed and are currently being tested 42 . The fact that SE‐EPI‐MRE could not resolve a difference in stiffness between the end of inspiration and end of expiration may be attributable to the long scan time and breath‐hold phases (21 s vs. 10 s in our breathing experiment) (Figure 4), which averages out temporal effects.…”

Single Breath-Hold 3-Dimensional Magnetic Resonance Elastography Depicts Liver Fibrosis and Inflammation in Obese Patients

“…An accurate solution of the complex shear modulus may allow for, in addition to fibrosis quantification, a better quantification of inflammation than the approximate solution of 2-dimensional MRE. [2][3][4] Moreover, free-breathing MRE techniques using either a motion-robust radial trajectory, 24 or respiratory triggering based on bellows, 25 or navigator echoes 26 have been proposed. However, these techniques lead to prolonged acquisition times for 2-dimensional MRE measurements, and their extension to acquire the full 3D displacement field would result in a considerably long acquisition time.…”