Non-alcoholic fatty liver disease (NAFLD) is a term that is commonly used to refer to excess fat within the liver cells (hepatic steatosis or non-alcoholic fatty liver), and inflammation of the liver due to fat deposition (steatohepatitis or NASH). While this silent killer affects nearly 25% of adults in the US, our healthcare system’s approach to diagnosing and treating this disease presents many gaps in both education and care.  Non-invasive imaging methods, MRI in particular, can play a crucial role in effective diagnosis and support the treatment of NAFLD.

The cost of reactive healthcare

Early diagnosis is essential for effective management of NAFLD. However, many patients do not display any symptoms for months or even years, resulting in a late stage diagnose that can be both costly and debilitating. In fact, NAFLD is commonly detected incidentally on imaging studies such as ultrasound, after the disease has already advanced.

One way to combat this challenge is to learn the risk factors for NAFLD and stratify each patient’s risk. If we identify the most at-risk patients, we can take a proactive approach in assessing their liver health through appropriate diagnostic testing.

Risk factors for NAFLD include:

· High cholesterol

· Obesity

· Type 2 diabetes

· Polycystic ovary syndrome

· Sleep apnea

· Hypothyroidism

Lack of precision diagnostics

Diagnostic imaging modalities used to detect fatty liver include ultrasound as well as low attenuation coefficient in x-ray computed tomography (CT). However, these modalities deliver qualitative data that does not provide a precise estimate of hepatic fat content.

Liver biopsy has been considered the gold standard to assess fat content in the liver. But this method only samples 1/50,000th of the liver and the results may vary depending on where in the liver the sample was acquired.  Liver biopsies are invasive, carry a small but non-negligible risk of complications, expensive, and are less suited to repeat measurements.

However, a novel MR imaging method (referred to as proton density fat fraction MRI or PDFF-MRI) can measure the hepatic fat content of the entire liver high spatial resolution and with extremely high precision. MR images of the liver that depict fact content demonstrate that fat deposition in the liver can be non-uniform (See figure below).

Conventional MRI (left), while excellent for visualizing anatomy, provides little information about the amount of fat present in the liver. In contrast, the fat fraction image (right) quantifies liver fat to demonstrate that a small region in the anterior portion of the liver is relatively spared from excessive fat deposition (yellow circle, 16.2% fat) compared to other regions (red circle, 30.8%).

This MRI based measurement of fat does not require contrast dye administration, or uses ionizing radiation.  Therefore, this method can be used to assess the impact that lifestyle changes or other interventions have on hepatic fat.

Utilizing precision diagnostics is also important when measuring liver inflammation. An excess of hepatic fat can lead to inflammation, which left untreated can result in fibrosis. Studies have shown that liver fibrosis can alter liver stiffness, which can be measured with MR elastography (MRE). MRE uses an external transducer to transmit small, low frequency mechanical vibrations into the liver. The speed of the sound wave propagation within tissue depends on how stiff the liver is. MR imaging measures the microscopic motion of these sounds waves with the body. These measurements are used to calculate the speed of sound wave propagation within liver tissue and ultimately provide an estimate on how stiff the liver is.

MR imaging of the liver and MRE do not require contrast administration and can be repeated as needed without incurring the risk associated with invasive biopsies or exposure to radiation.

While these MR modalities provide precise and accurate measurements of hepatic fat content and fibrosis, they have not been widely adopted as they require specialized expertise.

At Live Healthy Imaging, we bring decades of expertise and cutting-edge technologies to deliver highly accurate assessments of hepatic fat content and liver fibrosis. One scan provides a detailed report which provides the precision and insight necessary for a confident diagnosis and the foundation for successful intervention.

Visit our Liver Health Imaging page to learn more!

References:

1. Yokoo et al. Linearity, Bias, and Precision of Hepatic Proton Density Fat Fraction Measurements by Using MR Imaging: A Meta-Analysis. Radiology . 2018 Feb;286(2):486-498. doi: 10.1148/radiol.2017170550.
2. Cui et al. MRE is superior to ARFI for the diagnosis of fibrosis in patients with biopsy-proven NAFLD: A prospective study. Hepatology. 2016 February ; 63(2): 453–461. doi:10.1002/hep.28337.