MR elastography standards reliable for imaging chronic liver disease

Standardized MR elastography can reliably measure liver stiffness, according to an analysis published October 6 in Radiology.

An at least 19% change in liver stiffness represents a true biologic change with high confidence when standards are followed, wrote a team led by Suraj Serai, PhD, from Children’s Hospital of Philadelphia and the University of Pennsylvania.

“MR elastography provides a repeatable and reproducible quantitative biomarker of liver fibrosis, supporting longitudinal assessment of chronic liver disease,” wrote Serai and colleagues from the Quantitative Medical Imaging Coalition (QMIC).

While imaging biomarkers such as liver stiffness allow clinicians to noninvasively monitor chronic liver disease, liver stiffness measurements can be hindered by multiple factors. These include variability in imaging technique, scanner hardware, reconstruction algorithms, and interpretation practices across institutions and platforms.

Serai and colleagues in their analysis highlighted the Quantitative Imaging Biomarkers Alliance (QIBA), an RSNA initiative focused on standardizing quantitative imaging biomarkers. QIBA recently developed recommended guidelines for liver MR elastography that define standardized imaging procedures and performance benchmarks. The goal of these guidelines is to make hepatic stiffness measurements repeatable, reproducible, and clinically meaningful.

The guidelines suggest that a measured change in liver stiffness of at least 19% represents a true biologic change with 95% confidence, derived from a within-subject coefficient of variation of about 7%.

Representation of images generated in an MR elastography study in a 17-year-old male patient. (A) Magnitude image, (B) phase image showing black and white waves, (C) grayscale image (with 0–8-kPa scale; darker areas represent low stiffness, and brighter areas represent high stiffness), (D) elastogram (with 0–8-kPa color scale; purple and blue areas represent low stiffness, and green, yellow, orange, and red areas represent increasingly higher stiffness), (E) elastogram with confidence map showing areas of measurable stiffness, and (F) color wave image showing red and blue waves traversing through the liver. Additional postprocessed images may be available depending on the software version installed on the scanner.RSNA

The guidelines also outline the roles that physicists, engineers, technologists, radiologists, and image reconstruction and analysis software have in supporting standardized MR elastography. The roles include the following for each profession:

• Physicist/engineer: Oversees installation, initial validation, and ongoing quality assurance of the MRI scanner and elastography driver system. Also performs periodic checks of image quality and driver performance to ensure consistent mechanical wave generation.

• Technologist: Manages patient preparation, including fasting, positioning, and driver setup. Also verifies technical success by assessing wave visualization and overall image quality. 

• Radiologist: Responsible for image quality assurance, interpretation, and quantitative analysis. Also selects appropriate regions of interest (ROIs) and excludes low-confidence data.

• Software and standardization: Image reconstruction and analysis software must reliably generate standardized outputs, including stiffness maps and confidence maps. And outputs must conform to established postprocessing requirements.

The 19% repeatability threshold provides a benchmark to differentiate between true biologic change from measurement variability at the patient level, Serai et al wrote.

“At the group level, as is typical in clinical trials, meaningful treatment effects may be detected even when average changes are less than 19%, as statistical comparisons are made between treatment and control groups,” they added.

And vendors can benefit from the technical specifications and performance expectations provided in the guidelines, especially for emerging 3D vector MR elastography techniques, the authors added.

The team highlighted that such standardization can also enable clinicians and researchers to make confident, evidence-based decisions. This includes monitoring disease progression, evaluating treatment response, or enrolling patients in clinical trials.

“These guidelines facilitate the adoption of MR elastography as a validated quantitative imaging biomarker for chronic liver disease in both clinical practice and multicenter research,” the authors wrote.

Read the full analysis here.