Quantitative Assessment of Thin-Layer Tissue Viscoelastic Properties Using Ultrasonic Micro-Elastography With Lamb...

Area of Science:

• Biomedical Engineering
• Materials Science
• Acoustics

Background:

• Characterizing viscoelastic properties of thin tissues (e.g., arteries, corneas) at the micro-level is challenging.
• Existing micro-elastography techniques often neglect medium boundary conditions, potentially causing inaccurate property estimations.
• Accurate assessment of tissue viscoelasticity is crucial for understanding physiological function and disease states.

Purpose of the Study:

• To develop and validate an ultrasonic micro-elastography system integrated with the Lamb wave model for accurate viscoelastic property measurement in thin-layer tissues.
• To address the limitations of previous methods by incorporating boundary condition considerations.
• To validate the system's performance using phantoms and ex vivo biological tissues.

Main Methods:

• An ultrasonic micro-elastography system utilizing a 4.5-MHz ring transducer for acoustic radiation force and a 4.5-MHz needle transducer for wave detection was employed.
• Guided waves were generated and their propagation analyzed in k-space using impulse and harmonic methods to determine phase velocity and attenuation.
• The Lamb wave model, coupled with the Kelvin-Voigt model, was used to fit the measured phase velocity and estimate shear viscoelastic properties.

Main Results:

• Phantom experiments with varying thicknesses (2-4 mm) of gelatin and agar demonstrated consistent elasticity, aligning with bulk phantom mechanical tests and shear wave rheological models.
• The trend of measured attenuations correlated with viscosity results derived from the Lamb wave model.
• Ex vivo experiments on porcine cornea and rabbit carotid artery yielded shear viscoelasticity values: cornea (8.2-9.6 kPa with 0.8-0.9 Pa·s viscosity) and artery (26.5-27.9 kPa with 0.1 Pa·s viscosity).

Conclusions:

• The integrated Lamb wave model and ultrasonic micro-elastography system accurately characterizes the viscoelastic properties of thin-layer biological tissues.
• The developed method overcomes limitations of previous techniques by accounting for boundary conditions, leading to more reliable estimations.
• This approach offers a promising tool for non-invasive assessment of tissue biomechanics in clinical and research settings.