CAP™ : A noninvasive tool to evaluate and quantify steatosis

 Interview of Véronique Miette, PhD, Research Director at Echosens.

Could you briefly outline the objectives and principles of the CAP™?

CAP™, the Controlled Attenuation Parameter, was developed in response to demand by physicians who wanted to quantify steatosis in the liver.

Steatosis is the amount of fat in the liver. This fat can remain totally benign or can develop into fibrosis or even cirrhosis. It is very important for doctors to detect it. It is caused by factors such as diabetes, obesity, or hepatitis treatments.

Our idea was to develop a non-invasive, quantitative parameter that would allow us to quantify this steatosis. It is based on the attenuation of ultrasound signals. I should point out that a healthy liver attenuates ultrasound signals much less than a fatty liver. We measure the ultrasound attenuation on signals emitted by FibroScan®. This is a quantitative measurement expressed in dB/m. It varies continuously between 150 and 400 dB/m. A healthy liver will produce a measurement around 150-200, whilst a fatty liver will be measured at around 300-400 dB/m.



What are the advantages of CAP™ compared to other technologies?

As I said earlier, this measurement is totally non-invasive and quantitative. The physician performs exactly the same examination as before with the FibroScan®. We have developed a new algorithm, which allows us to calculate the CAP™ from the ultrasound signals used to calculate the stiffness.

After the exam, the physician therefore has two values: the stiffness correlated with fibrosis and the CAP™ correlated with steatosis. This allows the physician to track the progress of the disease.

Why has this measurement not been implemented on ultrasound scans, which are based on ultrasound signals?

Because FibroScan® is very repeatable. There is no variation in the gain and the electronics. All of the machines worldwide are the same, which means that a true attenuation measurement ca, be obtained on any machine and compared to attenuation measurements from all other machines, which is not true of ultrasound scanners. This technology has been patented and is specific to FibroScan®.