Quantitative magnetic resonance imaging for chronic liver disease

Abstract

Chronic liver disease (CLD) has rapidly increased in prevalence over the past two decades, resulting in significant morbidity and mortality worldwide. Historically, the clinical gold standard for diagnosis, assessment of severity, and longitudinal monitoring of CLD has been liver biopsy with histological analysis, but this approach has limitations that may make it suboptimal for clinical and research settings. Magnetic resonance (MR)-based biomarkers can overcome the limitations by allowing accurate, precise, and quantitative assessment of key components of CLD without the risk of invasive procedures. This review briefly describes the limitations associated with liver biopsy and the need for non-invasive biomarkers. It then discusses the current state-of-the-art for MRI-based biomarkers of liver iron, fat, and fibrosis, and inflammation.

Figure 1.

Conversion from relaxivity to LIC over a large biological range. The relationship between R2 and LIC is curvilinear while the relationship between R2* and LIC is mostly linear. Higher iron is associated with higher relaxivity rates.

Figure 2.

Complex-based R2* maps at 3T. Three different patients with mild, moderate and severe liver iron overload

Figure 3.

Magnitude-based PDFF maps. Three different patients with mild, moderate and severe liver steatosis.

Figure 4.

46-year-old female, magnitude-based PDFF maps. Segmental distribution of liver fat is displayed. Segment I has lower fat fraction compared to other liver segments.

Figure 5.

Contrast-enhanced portal venous phase images and correlating color coded elastogram of five different subjects with METAVIR fibrosis stages F0 to F4 confirmed on histopathological analysis.

Figure 6.

An example of MRE as a problem-solving tool. Contrast-enhanced portal venous phase of two separate 30-year-old male patients with abnormal liver function tests (A + B). Morphological changes suggest advanced fibrosis or cirrhosis with portal hypertension in both patients. c: Color-coded elastogram demonstrates only minimally increased liver stiffness. Biopsy demonstrates diffuse nodular regenerative hyperplasia without significant fibrosis. d: Color-coded elastogram demonstrates markedly increased liver stiffness consistent with stage four fibrosis (cirrhosis), which was confirmed on biopsy.

Figure 7.

Select images of 3D MRE and chemical-shift MRI-derived PDFF on subjects with NAFLD. The subject in the top row has biopsy-proven NASH and stage three fibrosis. The subject in the bottom row has NAFL without NASH and fibrosis. Note the elevated liver stiffness and decreased damping ratio in the liver in the subject with NASH.