Liver shear wave vibroelastography

点击翻译按钮获取中文摘要

Liver disease affects hundreds of millions of people worldwide. Hepatitis and fatty liver disease are major problems in Asian and North American populations. Liver disease management is critically dependent on an accurate assessment of physical changes in the liver tissue, which manifest themselves as an increase in the liver stiffness, typically assessed qualitatively by palpation by a physician. It is possible to quantitatively assess the level of advancement of liver disease, from stage 0 (normal) to stage 4 (cirrhosis), using tissue pathological analysis (magnified slides obtained from tissue samples extracted with a biopsy core needle), but this requires a needle biopsy. It is also possible to measure the "bulk" properties of the liver tissue without biopsy by using a measurement of the propagation speed of shear waves in tissue. Currently, the wave propagation can be measured by applying a knock, like a gentle hammer action, to tissue, and measuring the speed of the resulting wavefront with ultrasound. In an alternative technique, the knock can be generated by the clinical ultrasound transducer itself. Finally, it is also possible to measure the localized state of liver fibrosis throughout the volume of the liver by using magnetic resonance elastography, a technique in which a steady vibration is applied to tissue and the wave pattern throughout the tissue volume is visualized. The wave pattern can be quantitatively related to tissue stiffness. Our goal is to show that we can measure the localized state of liver fibrosis with ultrasound, by mimicking the magnetic resonance elastography technique. For this purpose, we will work with our industrial partner to acquire three-dimensional images of the steady-state wave pattern introduced in the liver by a mechanical vibrator. We will obtain liver stiffness images from ultrasound and we will compare them with those generated by magnetic resonance elastography in volunteers and in a small number of patients. The technique we propose has the advantage of being able to image the liver volume at depth, through a much simpler examination than by magnetic resonance elastography. Its successful implementation has the potential to make a significant impact on how liver disease management.