Shear Wave Measurement Correction for Ultrasound Beam Geometry Bias
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Solution Overview
Problem
Shear wave speed measurements in ultrasound vibrometry are biased due to the three-dimensional structure of both the ultrasound push and detection beams, leading to overestimation and position dependence, especially at shallow focal depths where the force field has split peaks.
Innovation Solution
A method to correct shear wave measurements by obtaining a correction factor from either a look-up table or mathematical modeling of the ultrasound energy intensity field, accounting for the geometry of the beams, allowing for accurate calculation of tissue mechanical properties like stiffness and viscosity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ultrasound push beam is used to generate shear waves, then shear waves are produced for tissue characterization, but measurement bias is introduced due to the three-dimensional structure of the beam
Solution Approach 1:
The patent applies preliminary action by pre-calculating correction factors based on the known ultrasound beam geometry before actual measurements are taken. The system characterizes the push beam and detection beam three-dimensional structures in advance, stores correction factors in lookup tables, and applies these pre-computed corrections to measured shear wave speeds, thereby eliminating measurement bias without adding real-time computational complexity.
2Use of energy by moving object
If detection is performed closer to the push beam, then more signal strength is obtained, but shear wave speed overestimation increases
Solution Approach 1:
The patent implements feedback by incorporating beam geometry correction into the measurement process. The system measures the actual beam characteristics, determines the appropriate correction factor based on the distance between push and detection beams, and applies this correction to the measured shear wave speed. This feedback mechanism ensures that measurements taken at any distance can be accurately corrected, allowing optimal signal strength while maintaining measurement precision.
3Measurement precision
If shallow focal depths are used, then better spatial resolution is achieved, but measurement bias increases due to split peaks in the force field
Solution Approach 1:
The patent applies local quality by providing position-dependent correction factors that are specific to each measurement location and beam configuration. Instead of using a single universal correction, the system tailors the correction factor to the local conditions including focal depth, beam focus position, and detection location. This allows shallow focal depths to be used with high spatial resolution while applying appropriate corrections to maintain measurement reliability and consistency.
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
The method effectively corrects for biases in shear wave speed measurements, providing more accurate assessments of tissue mechanical properties by accounting for beam geometry, reducing overestimation and position dependence, and improving the reliability of measurements across different tissue types and depths.
Implementation Method 1
a focused ultrasound beam, operating within FDA safety limits, is applied to a subject to generate harmonic shear waves in a tissue of interest
Implementation Method 2
These shear wave speeds are estimated from the phase of tissue vibration that is detected between two or more points with known distance along the shear wave propagation path
Data Source
AI summary
A system and method for measuring mechanical properties of a tissue using an ultrasound system is provided. Ultrasound energy is applied to the tissue using the ultrasound system in order to produce shear waves that propagate in the tissue. Measurement data are then acquired by directing ultrasound detection pulses into the tissue. Information about the intensity field of the ultrasound energy used to produce the shear waves is obtained and used to produce a correction factor. This correction factor is applied to the measurement data to correct the measurement data for errors arising from the geometry of the ultrasound energy used to produce the shear waves. From the corrected measurement data, mechanical properties of the tissue are calculated.