Harmonic Shear Wave Imaging Using Sinusoidal Modulation
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Solution Overview
Problem
Existing shear wave elastography methods, particularly transient methods, face biases due to ultrasound frequencies, transducer types, and imaging depths, which complicate the measurement of shear modulus in tissues, and require additional equipment like external mechanical drivers, making them less optimal for clinical use.
Innovation Solution
The Harmonic Shear Wave Imaging (HSWI) method uses a single array transducer to generate narrowband shear waves by varying the acoustic intensity of ultrasound pulses sinusoidally, allowing for controlled frequency shear wave production and measurement, enabling accurate shear wave speed mapping without the need for separate drivers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transient shear wave methods are used, then shear wave speed can be measured, but biases are introduced due to ultrasound frequencies, transducer types, and imaging depths
Solution Approach 1:
The patent uses periodic sinusoidal modulation of push pulse intensities at a controlled frequency to generate narrowband shear waves. This periodic action creates harmonic shear waves with a single dominant frequency, eliminating the bandwidth-related biases present in transient methods while maintaining measurement accuracy across different ultrasound parameters.
Solution Approach 2:
The patent changes the temporal characteristics of the excitation from impulsive (broadband) to sinusoidal (narrowband). By modulating the push pulse intensities sinusoidally at a specific frequency, the method transforms the shear wave generation process to produce narrowband waves, thereby reducing parameter-dependent biases in shear wave speed measurements.
2Measurement precision
If external mechanical drivers or separate focused ultrasound transducers are used for harmonic elastography, then narrowband shear waves can be generated, but device complexity increases
Solution Approach 1:
The patent makes the imaging transducer perform dual functions: it both generates the shear waves through sinusoidally modulated push pulses and detects the resulting tissue displacements. This eliminates the need for separate mechanical drivers or dedicated excitation transducers, reducing device complexity while maintaining precise frequency control through electronic modulation.
Solution Approach 2:
The patent combines the shear wave generation and detection functions into a single transducer system. The imaging transducer elements that normally only detect ultrasound are also used to generate shear waves by applying sinusoidally modulated acoustic radiation force, merging two previously separate functions into one integrated system.
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
HSWI provides robust, accurate, and consistent measurements of shear wave speed and viscoelastic properties using a single transducer, comparable to magnetic resonance elastography, suitable for clinical applications and capable of measuring tissue stiffness and viscoelastic properties across a broad frequency range.
Implementation Method 1
Each push pulse generates an acoustic radiation force that pushes the tissue and creates an individual shear wave propagating through the tissue
Data Source
AI summary
A method of performing shear wave elastography in tissue includes transmitting successively a series of ultrasound push pulses in the tissue in a region of interest (ROI) using a single array transducer. The acoustic intensities of the push pulses are sinusoidally modulated with a modulation frequency, Each push pulse generates an acoustic radiation force that pushes the tissue and creates an individual shear wave propagating through the tissue. The amplitudes of the shear waves, and therefore, the displacements produced by the push pulses, are positively proportionally to the intensities of the push pulses. The successively created individual shear waves with different amplitudes sum together to form a continuous, harmonic summed shear wave with a single frequency the same as the modulation frequency of the push pulses.