It has been demonstrated that thermoacoustic imaging can be used to identify water and fat concentrations \[Bauer, 2012\]. In addition, the group led by Dr. Kruger have demonstrated that conventional computed tomography shows similar features to thermoacoustic imaging in small animal studies \[Kruger, 2003\]. These concepts have led Endra Life Sciences to develop the FLIP device with the purpose of imaging fat concentration in liver tissue with indications for fatty liver disease. Non-alcoholic fatty liver disease (NAFLD) was first reported in 1980 by pathologists at the Mayo clinic in obese, or overweight, patients with no history of alcohol abuse. This represented the first time that fatty livers were observed with no history of alcohol abuse. Since that first report of NAFLD, increased rates of obesity and general increased caloric intake has dramatically increased rates of fatty liver disease. Estimates of NAFLD range from 25 - 40% of the adult population globally. NAFLD is a multi-system disease. Fatty liver disease is highly correlated with obesity and alcohol abuse, and is an important biomarker of insulin resistance and metabolic disease. Endra's technology offers a non-invasive, cost effective point of care solution to monitoring liver fat content that will be enormously helpful in surveilling patients with metabolic disease, insulin resistance, and those at risk for later stage liver disease.

This study will provide additional information that will guide the further development of the FLIP device with the end goal of commercializing the product. Fibroscan is a device that is currently on the market that is also indicated for fatty liver disease. Fibroscan is a shear wave elastography device that measures the stiffness of liver tissue by mechanically deforming tissue (by utilizing a plunger that vibrates the surface of the skin) and measures the resulting shear wave speed within the liver by ultrasound. The shear wave speed is related to the mechanical stiffness of the tissue. Fibroscan aims to assess the progression of infiltration of collagen into normal liver tissue that results in scarring, characteristic of fibrotic liver disease. Liver fibrosis progresses from fatty liver disease, not all fatty liver disease patients develop fibrotic liver disease.

The Fibroscan device has an optional software module that attempts to quantify the attenuation of the shear wave as it travels away from the plane of deformation. Fibroscan refers to this measurement as CAP (Calculated Attenuation Parameter). The attenuation of the shear wave is thought to be related to the degree of liver steatosis (fat content). To date, the technique has demonstrated poor sensitivity, and is poorly correlated with quantitative MRI measures of liver fat. Furthermore, CAP measurements in obese patients are difficult to obtain and unreliable . Endra's technology aims to provide much more sensitive measurements of liver fat content at the point of care. The Endra device has the potential to quantify fat content as low as 5% (by volume). The system is interoperable with ultrasound and leverages B-mode ultrasound imaging to guide measurement location. Compared to Fibroscan's CAP, Endra's fatty liver measures are expected to be much more sensitive and reproducible based on anatomical guidance by ultrasound imaging.