Liver fibrosis assessment using transient elastography guided with real-time b-mode ultrasound imaging

Liver fibrosis is a kind of chronic damage of the liver. The progression of liver fibrosis will result cirrhosis which is one of the top 10 causes of death in the western world. Recently, a device developed based on transient ultrasound elastography, named as Fibroscan, shows promising results with high accuracy and good reproducibility. However, this device does not provide visual guidance for the liver being tested during measurement. We aim to design and validate a transient elastography system with real-time B-mode imaging for liver fibrosis assessment. Our development is based on a conventional B-mode ultrasound scanner, which consists of a B-mode ultrasound probe fixed along the axis of a mechanical vibrator. The induced shear wave propagates through the liver tissue. During measurement, B-mode ultrasound imaging with a frame rate of 30 f/s is generated in real-time to view the morphological information of the tissue, and an A-mode ultrasound with a frame rate of 6000 f/s is generated to track the propagation of shear wave at a selected location. The propagation speed of the shear wave is related to the tissue stiffness and Young's modulus is calculated. The system was tested using a series of custom-made phantoms with different stiffness and the results were compared with those measured by Fibroscan. For phantom A1, the Young's modulus is 32.4 kPa and 35.4 kPa obtained by Fibroscan and our system, respectively. For phantom A2, the modulus is 15.9 kPa and 19.8 kPa, respectively. For the preliminary in vivo assessment, the Young's modulus of a normal male subject is 5.8 kPa and 7.5 kPa obtained by Fibroscan and our system, respectively. In summary, we have successfully developed a transient ultrasound elastography system with real-time B-mode imaging for the assessment of liver fibrosis.