Model-Independent Viscoelastic Tissue Quantification
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current elasticity imaging techniques require the use of rheological models to quantify tissue viscoelastic properties, which introduces a significant computational burden and may not accurately describe material behavior at all frequencies, making them less general and desirable.
Innovation Solution
A system and method for model-independent quantification of tissue viscoelastic properties using time-dependent creep response induced by acoustic radiation force, where the complex shear modulus is estimated from tissue displacement measurements without relying on a rheological model, and calibrated using shear wave dispersion ultrasound vibrometry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If rheological models are used to quantify tissue viscoelastic properties, then measurement precision can be achieved, but device complexity and computational burden increase significantly
Solution Approach 1:
The patent extracts and eliminates the rheological model fitting step from the viscoelastic properties quantification process. By using a model-independent approach based on shear wave dispersion and attenuation measurements, the method removes the complex model fitting operation while maintaining measurement precision through direct physical parameter measurement.
Solution Approach 2:
The patent replaces the mechanical/mathematical model fitting system with a direct physical measurement system. Instead of using rheological models to infer viscoelastic properties, the method directly measures shear wave dispersion and attenuation to calculate complex shear modulus, substituting complex computational mechanics with straightforward physical parameter extraction.
2Measurement precision
If rheological models are used to describe material behavior, then viscoelastic properties can be estimated, but adaptability across different frequencies is reduced
Solution Approach 1:
The patent changes the fundamental parameters used for characterization from model-based rheological parameters to direct shear wave dispersion and attenuation parameters. This parameter transformation enables the method to accurately describe material behavior across a broader frequency range without being constrained by the limitations of specific rheological models.
Solution Approach 2:
The patent creates a universal measurement approach that can characterize viscoelastic properties across different frequency ranges without requiring frequency-specific models. The shear wave dispersion and attenuation-based method provides a single unified framework that works universally for various frequency conditions, eliminating the need for multiple specialized models.
3Measurement precision
If shear wave propagation methods are used, then tissue mechanical properties can be quantified, but measurement range is limited to short distances due to attenuation
Solution Approach 1:
The patent employs periodic shear wave propagation at multiple frequencies to overcome the limited penetration distance. By measuring shear wave dispersion across a spectrum of frequencies and using the attenuation characteristics, the method can infer mechanical properties with greater accuracy and extended effective measurement range compared to single-frequency methods.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables non-invasive, fast, and robust estimation of viscoelastic properties without the need for model fitting, providing a more general and accurate measurement of tissue mechanical properties across a range of frequencies.
Implementation Method 1
Shear waves are usually generated by external mechanical vibration or by acoustic radiation force from a focused ultrasound beam. The advantage of using acoustic radiation force is that if an acoustic window is available then the ultrasound system can create a focused beam to apply radiation force to push tissue.
Implementation Method 2
The motion of the tissue is measured using pulse-echo ultrasound techniques. Shear wave speeds at a number of frequencies are measured and subsequently fit with a theoretical dispersion model to inversely solve for tissue elasticity and viscosity.
Implementation Method 3
Tissue creep response to an applied step-force by means of acoustic radiation force has been shown in several studies. However, as in shear wave propagation methods, a rheological model needs to be fit to the MSSER experimental data to solve for viscoelastic parameters.
Implementation Method 4
In SDUV, a focused ultrasound beam that operates within FDA regulatory limits, is applied to a subject to generate harmonic shear waves in a tissue of interest. The propagation speed of the induced shear wave is frequency dependent, or 'dispersive,' and relates to the mechanical properties of the tissue of interest.
Implementation Method 5
These shear waves propagate a short distance, such as only a few millimeters, because of tissue absorption and shear wave attenuation.
Data Source
AI summary
A model-independent method for producing a viscoelastic tissue property metric using ultrasound is provided. A mechanical stress, such as an acoustic force, is applied to a tissue using an ultrasound system and tissue displacement resulting from the applied acoustic force is measured. From the tissue displacement measurements, a complex modulus, such as a relative complex modulus, is extracted. A loss tangent is calculated from the extracted complex modulus. Using the calculated loss tangent, viscoelastic tissue property metrics may be calculated.