MRI-based technologies for assessing non-alcoholic fatty liver disease

The condition

2.1 Non-alcoholic fatty liver disease (NAFLD) is the term for a range of conditions caused by a build-up of fat in the liver. NAFLD develops in 4 stages:

Diagnosis

2.2 NAFLD is usually diagnosed using ultrasound. There are several non-invasive tests available to assess the stage of fibrosis in NAFLD, including blood-based tests as well as imaging such as transient elastography or acoustic radiation force impulse elastography (ARFI).

2.3 NICE's guideline on the assessment and management of non-alcoholic fatty liver disease advises to test for advanced liver fibrosis in people with NAFLD using the enhanced liver fibrosis (ELF) test. If the result of the ELF test is 10.51 or above, the NICE guideline for cirrhosis in over 16s: assessment and management recommends testing for cirrhosis using transient elastography or ARFI. Routine liver blood tests are not recommended to rule out NAFLD or test for advanced fibrosis.

2.4 The British Society of Gastroenterology (BSG) guideline on NAFLD recommends testing for fibrosis in people with NAFLD using the NAFLD fibrosis score or FIB-4. If these scores indicate an intermediate risk, transient elastography or the ELF test can be used to further clarify the diagnosis. If the non-invasive tests are not able to exclude advanced fibrosis, the BSG recommends that liver biopsy is considered to stage the level of inflammation and fibrosis, and to rule out other concomitant liver disease. Biopsy results are used to decide referral and treatment strategies for people with NAFLD. The NICE guideline for cirrhosis in over 16s: assessment and management recommends that liver biopsy is considered to diagnose cirrhosis when transient elastography is not suitable. NASH is diagnosed using biopsy. However, liver biopsy is an invasive procedure that is associated with well-recognised complications including bleeding and death. NICE's guideline on the assessment and management of non-alcoholic fatty liver disease includes a research recommendation to identify which non-invasive tests most accurately identify NASH in people with NAFLD.

Management

2.5 Treatment for NAFLD with no or minimal fibrosis consists of education on risk factors for advanced fibrosis and advice on weight management. According to the NICE guideline for non-alcoholic fatty liver disease: assessment and management, people with advanced fibrosis may be offered pioglitazone or vitamin E. There are currently no treatments available specifically for NAFLD or NASH, but people with NASH or advanced fibrosis may enter clinical trials for new therapies.

2.6 The NICE guideline for cirrhosis in over 16s: assessment and management recommends that people with cirrhosis are monitored for end-stage liver disease and liver cancer every 6 months, tested for varices, offered treatment for complications of cirrhosis (for example variceal band ligation), and potentially offered prophylactic treatment depending on comorbidities.

LiverMultiScan

2.7 LiverMultiScan is a standalone software application produced by Perspectum that provides quantitative multiparametric analysis of non-contrast MRI. LiverMultiScan is intended to help clinicians diagnose and stage liver disease by non-invasively imaging the liver.

2.8 LiverMultiScan uses iron-corrected T1 (cT1), proton density fat fraction (PDFF) and T2* MRI protocols for its analyses. cT1 outputs are measured in milliseconds (ms), and correlate with liver fibro-inflammation. MRI PDFF is an MRI estimate of fat content and is expressed as a percentage. T2* is a measure correlated with the iron content of the liver and is used to produce the cT1 scan. The diagnosis indicated by the cT1 output and the clinical recommendations proposed by the company are as follows:

Magnetic resonance elastography

2.9 Magnetic resonance elastography (MRE) combines MRI with low-frequency vibrations to create a 2D or 3D elastogram showing the stiffness of tissue. In addition to the usual MRI, an external mechanical driver passes vibrations through a flexible tube to a passive driver placed on a person's abdomen over the liver. The driver is manufactured by Resoundant. MRE is intended to generate acoustic vibrations in the body during an MRI exam to assess tissue elasticity for diagnostic purposes.

2.10 MRE is used for detecting and evaluating different stages of fibrosis and is usually added to a conventional abdominal MRI protocol. MRE outputs are provided in kilopascals (kPa). The company suggested that MRE liver stiffness outputs can be used to stage liver fibrosis as follows:

No further testing before a decision to do a biopsy or any other care decision

2.11 Following testing as described in sections 2.2 to 2.4, in the absence of MRI-based testing, no other tests would be done before a decision to do a biopsy or any other care decision.