Magnetic resonance elastography of abdomen

Abstract

Many diseases cause substantial changes in the mechanical properties of tissue and this provides motivation for developing methods to non-invasively assess the stiffness of tissue using imaging technology. Magnetic resonance elastography (MRE) has emerged as a versatile MRI-based technique, based on direct visualization of propagating shear waves in the tissues. The most established clinical application of MRE in the abdomen is in chronic liver disease. MRE is currently regarded as the most accurate non-invasive technique for detection and staging of liver fibrosis. Increasing experience and ongoing research is leading to exploration of applications in other abdominal organs. In this review article, the current use of MRE in liver disease and the potential future applications of this technology in other parts of the abdomen are surveyed.

Elastography in Chronic Liver Disease: Modalities, Techniques, Limitations, and Future Directions

“…MR elastography is currently regarded as the most accurate noninvasive method for detection and staging of liver fibrosis (57)(58)(59). Calculations of liver stiffness with MR elastography are highly reproducible and show excellent interobserver agreement (60)(61)(62).…”

“…An ROI is typically drawn on each of four axial images, and the mean stiffness is reported. To properly draw an ROI, artifacts must be excluded, including the edge artifact, fossae and fissures, large (>3-mm) vessels, regions of wave interference, and the artifactual "hot spot"; examples of these artifacts are provided in Figure 14 (57). Areas of low statistical confidence are also typically excluded from the reported measurement.…”

Does gadoxetate disodium affect MRE measurements in the delayed hepatobiliary phase?

“…We used a two-dimensional phase-contrast GRE sequence to gather three transverse slices through the liver parenchyma and manually positioned an as large as possible polygonal ROI within the 95% confidence region of the acquired stiffness maps. This generally accepted method [43] allows the evaluation of a large portion, but not of the entire organ, because usually the 95% confidence region with reliable stiffness values is smaller than the entire liver [8]. The use of true three-dimensional imaging could be alternatively discussed, even though longer acquisition times might be problematic for breath-holding [18], and these methods are not yet commercially available.…”

“…Mechanical 60-Hz vibrations were applied using a circular passive acoustic driver (Resoundant, Inc.) placed against the right abdominal wall and fixed using an elastic band. A two-dimensional commercial phase-contrast gradient-echo (GRE) sequence as provided by the manufacturer was applied, which performs inline calculation of wave and stiffness images together with a 95% confidence map showing areas with less reliable stiffness crossed out [8]. For every patient, three transverse slices through the liver were acquired, with one slice located in the cranial, one in the middle (portal vein at the level of the hilus) and one in the caudal hepatic section.…”

Theoretical mathematical model of non-invasive flow quantification for future implementation in routine clinical MRI

“…Among the existing imaging techniques, MRI offers the most complex multiparametric geometricophysicochemical information of the physio-anatomy of interest. The information includes: lengths or thicknesses (Fanea and Fagan, 2012), areas (Feczko et al, 2009), volumes (Feczko et al, 2009), relaxation times (Fanea and Fagan, 2012;Bojorquez et al, 2017), diffusion coefficients and fractional volumes of the diffusing components detected (Dong et al, 2004;Le Bihan, 2014), magnetization transfer ratios and the protein concentration (Gupta, 2002;Oreja-Guevara et al, 2006;Henkelman et al, 2001), magnetic susceptibility and iron or calcification concentrations (Duyn, 2013;Wang and Liu, 2015;Liu et al, 2015), and shear stiffnesses in elastography (Yin et al, 2016;Mariappan et al, 2010;Venkatesh and Ehman, 2015;Hiscox et al, 2016). More recently, magnetic resonance spectroscopy has been implemented clinically to analyze the complex biochemical composition of the anatomy imaged (Soares and Law, 2009).…”