Quantifying hepatic shear modulus in vivo using acoustic radiation force.

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Acoustics

Background:

• Shear wave speed in tissue correlates with shear modulus, a key indicator of tissue stiffness.
• Acoustic radiation force can generate shear waves for tissue characterization.
• Noninvasive quantification of liver stiffness is crucial for diagnosing liver fibrosis and steatosis.

Purpose of the Study:

• Develop and validate a robust algorithm to quantify shear wave speed from ultrasound displacement data, even with poor signal-to-noise ratio.
• Apply the algorithm to in vivo human volunteer data to assess clinical feasibility for liver tissue shear modulus measurement.
• Establish a noninvasive method for longitudinal liver stiffness quantification in clinical settings.

Main Methods:

• Utilized focused, impulsive acoustic radiation force excitations to generate shear waves.
• Employed time-to-peak displacement data from ultrasonically tracked responses to characterize shear wave speed.
• Validated the algorithm using finite element method simulations and in vivo human volunteer datasets.

Main Results:

• Simulations showed accurate shear modulus reconstructions within 0.3 kPa for low stiffness (1.3-5 kPa) and 1.0 kPa for high stiffness (10-16 kPa).
• In vivo liver shear moduli were reconstructed between 0.9 and 3.0 kPa with an average precision of +/-0.4 kPa.
• Longitudinal measurements over 105 days demonstrated repeatable liver stiffness quantification with average moduli of 1.9 +/- 0.50 kPa and 1.8 +/- 0.4 kPa.

Conclusions:

• The developed algorithm accurately quantifies shear wave speed and reconstructs shear modulus from ultrasound displacement data.
• The method demonstrates clinical feasibility for noninvasive liver stiffness measurement in human volunteers.
• This technique shows promise as a reliable clinical tool for longitudinal assessment of liver stiffness in conditions like fibrosis and steatosis.