MR Elastography of the Liver: Preliminary Results

TLDR

The study aims to develop and prospectively evaluate a magnetic resonance elastography method for measuring liver stiffness in healthy volunteers and patients with liver fibrosis. Using a HIPAA‑compliant protocol, the authors built a pneumatic acoustic wave generator, tested it on a tissue‑simulating phantom with and without ribs, and measured liver stiffness in 12 volunteers (subcostal and transcostal approaches) and 12 chronic liver disease patients (transcostal) with statistical analysis. Ex vivo ribs reduced shear wave amplitude but did not impede stiffness measurements; transcostal imaging produced better shear waves than subcostal, and liver stiffness was significantly lower in volunteers (2.0 kPa) than in fibrotic patients (5.6 kPa), demonstrating feasibility and promise for noninvasive fibrosis assessment. © RSNA, 2006.

Abstract

Purpose: To develop a method for measuring liver stiffness with magnetic resonance (MR) elastography and to prospectively test this technique in healthy volunteers and patients with liver fibrosis. Materials and Methods: This HIPAA-compliant study was approved by an institutional review board, and informed consent was obtained from each subject. First, to determine the feasibility of applying shear waves to the liver, a pneumatic acoustic wave generator was developed and tested by using a tissue-simulating gel phantom with ribs on one side and without ribs on the other. The effect of interposed ribs on stiffness measurements was tested. Then, liver stiffness was measured with MR elastography in 12 healthy volunteers (eight men, four women; mean age, 26.7 years; age range, 19–39 years) by using the subcostal approach and the transcostal approach and in 12 patients with chronic liver disease (six men, six women; mean age, 50.5 years; age range, 36–60 years) by using the transcostal approach. Various statistical analyses were performed to assess all measurements. Results: Ex vivo, interposed ribs reduced shear wave amplitude but did not hinder stiffness measurements. In volunteers, the transcostal approach surprisingly yielded better shear waves in the liver than did the subcostal approach. The mean liver shear stiffness was significantly lower in volunteers (mean, 2.0 kPa ± 0.3 [standard deviation]) than it was in patients with liver fibrosis (mean, 5.6 kPa ± 5.0; median, 3.7 kPa; range, 2.7–19.2 kPa; P < .001). Conclusion: MR elastography of the liver is feasible and shows promise as a quantitative method for noninvasive assessment of liver fibrosis. © RSNA, 2006