Ultrasound Elastography Proves an Effective Tool for Diagnosing Hepatic Fibrosis
Non-invasive technique helps identify patients at high risk for disease progression
Ultrasound (US) elastography, which assesses tissue stiffness, is an effective non-invasive adjunct to liver biopsy in the diagnosis of hepatic fibrosis, according to a recent Radiology article.
“We have long known that the liver tissue stiffness corresponds to various pathologies, including fibrosis deposition in the liver,” said co-author Theodore Pierce, MD, abdominal radiologist at Massachusetts General Hospital (MGH) and an instructor at Harvard Medical School, both in Boston. “What makes elastography interesting is that it interrogates a fundamental property of the tissue, letting us directly assess stiffness.”
In their Radiology Research in Practice article, “US Elastography in Hepatic Fibrosis — Radiology In Training,” Dr. Pierce and Aileen O’Shea, MB BCh BAO, clinical fellow in the Department of Radiology at MGH, offer a comprehensive review of previous research and discuss a case presentations related to hepatic fibrosis.
Watch Drs. Pierce and O'Shea discuss their research:
Chronic liver disease is a growing public health concern worldwide, with 12% to 44% of cases progressing to advanced fibrosis and cirrhosis, making detection and early intervention in high-risk groups essential. Cirrhosis leads to liver failure and liver cancer. While liver biopsy is considered the reference standard for diagnosing hepatic fibrosis, the technique has key limitations including cost, procedure-associated risks, potential for tissue under-sampling and variability in interobserver interpretation.
“Biopsy by its very nature can only take a small sample of liver and that sample may not be representative of a disease process,” Dr. O’Shea said. “This can lead to an underestimation or overestimation of the extent of fibrosis. Elastography allows us to stratify patients at risk for hepatic fibrosis and obtain a more global assessment of their liver tissues without exposing them to biopsy risks.”
Ultrasound elastography determines parenchymal stiffness by measuring the speed of waves (created by mechanical or US forces) traveling through the liver tissue.
For example, strain elastography uses a mechanical force to deform tissues allowing one to compare the target tissue stiffness to that of surrounding structure and then calculate a stiffness ratio between tissues. Shear wave elastography, on the other hand, uses US pulses to send waves through tissue and measures their velocity. As shear waves travel through the liver, a quantitative, color-coded map of tissue stiffness is overlaid on a B-mode image of the liver, indicating the location of stiff tissue and determining how stiff that tissue is, in real time.
“If we can expand our understanding of elastography and develop it as a non-invasive biomarker for liver disease, we can identify which patients to treat earlier in the course of their disease and offset that potential progression toward cirrhosis.”
AILEEN O’SHEA, MB BCH BAO
Sheer Wave Elastography
In one case study, sheer wave elastography was used to confirm the presence of METAVIR Stage 2 hepatic fibrosis in a patient with a history of fatty liver disease.
“Elastography was key in helping us to identify this patient as high risk and confidently moving forward with a biopsy,” Dr. O’Shea said. “Having a relatively easy way to screen out those normal individuals and determine which ones need biopsies for further clarification is really helpful.”
In addition to being non-invasive, elastography is also low-cost, quick and often relatively portable.
Patient positioning and principles of two-dimensional shear-wave elastography. A, Patient’s right arm should be placed in maximal abduction to permit probe placement and to increase intercostal space to reduce rib shadowing. Right side is preferentially chosen; left-sided measurements are often artifactually increased due to secondary compressive effects of the probe, heart, or stomach. B, Standard curvilinear transducer, typically used for abdominal imaging applications, is used to generate focused ultrasound energy, resulting in shear waves traveling perpendicular to ultrasound pulse. High-quality B-mode imaging is used to track shear waves and to measure propagation speed (shear-wave velocity), which correlates to liver stiffness. C, Color-coded elastogram scale is superimposed on B-mode US images and suitable region of interest (ROI) is placed to measure liver stiffness. ROI should be positioned at least 1.5–2 cm away from liver capsule (arrow in C) in a site free traversing vasculature, on image without rib shadowing artifact, and not more than approximately 6.5 cm from skin surface.
O’Shea, et al, Radiology 2021 ©RSNA 2021
Understanding Elastography
One in three people is likely to have fatty liver disease. And as fatty liver disease becomes increasingly prevalent across the globe, cirrhosis, its end stage, is likely to increase in prevalence as well.
While further research is necessary, evidence shows US elastography can assist in the early detection of cirrhosis and in the validation of new therapies for hepatic fibrosis, Drs. Pierce and O’Shea said.
“If we can expand our understanding of elastography and develop it as a non-invasive biomarker for liver disease, we can identify which patients to treat earlier in the course of their disease and offset that potential progression toward cirrhosis,” Dr. O’Shea said.
Along with identifying patients who need a biopsy, elastography allows physicians to monitor patients as needed throughout treatment to gauge their response to therapies.
“In the future, new therapies will likely be developed for stopping or reversing liver fibrosis, and we will need ways to validate those treatments and monitor their effect,” Dr. Pierce said.
For More Information
Access the Radiology article, “US Elastography in Hepatic Fibrosis — Radiology In Training."
Radiology in Training Article Features Voice of Resident, Expert
The article, “US Elastography in Hepatic Fibrosis,” is a Radiology in Training: Research in Practice article, a case-based review applying science reported in Radiology to a specific patient.
The article features the voice of a radiology trainee and an expert on the issue but does not present new data or systematic analysis of the literature. Aileen O’Shea, MBBCh, clinical fellow in the Department of Radiology at Massachusetts General Hospital (MGH), is the trainee and Theodore Pierce, MD, abdominal radiologist at MGH and an instructor at Harvard Medical School, is the expert.
To harness the value of trainee talents in the editorial process, the Radiology Editorial Board and the RSNA launched Radiology In Training in 2020.
Created under the leadership of the Radiology Editor, David Bluemke, MD, and senior consultant to the editor, Susanna Lee, MD, PhD, the mission of Radiology In Training is to create a community of radiologists who will learn from research published in Radiology, to translate it into knowledge applicable to daily clinical practice and to share it with the broad readership.
The inaugural Radiology In Training Editorial Board includes seven deputy editors and eight associate editors, representing a variety of institutions throughout the world. During a one-year term, the trainees gain an in-depth experience in the editorial process at Radiology. Radiology In Training editorial board members also create unique multimedia content including “Tweetorials” and “In A Minute” videos, which deliver scientific knowledge published in Radiology to a large audience through social media.
Nominations for the Radiology in Training Editorial Board are accepted in the Spring. The new Editorial Board was slated to begin in July 2021.
To propose a topic for a Research in Practice article, email the Editorial Office at radiology@rsna.org for consideration by the Radiology In Training Editorial Board. For more information on Radiology manuscripts, go to pubs.rsna.org.