Ultrasonic Characterization of Heterogeneous Media Using Focused Reflection Matrices
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Solution Overview
Problem
Conventional ultrasonic imaging methods face challenges in characterizing heterogeneous media due to variations in sound speed, leading to image distortion and degradation in resolution and contrast, especially in medical imaging where the medium is not homogeneous.
Innovation Solution
A method involving the generation of a series of incident ultrasonic waves and the determination of a focused reflection matrix with additional delays to locally probe the medium, allowing for the extraction of wavefront images and estimation of focusing quality, which helps in identifying preferred directions of anisotropy and local lesions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ultrasonic imaging methods are used in heterogeneous media, then the imaging process is simple and fast, but the image resolution and contrast are degraded due to sound speed variations
Solution Approach 1:
The patent applies preliminary action by performing wavefront sensing and aberration measurement before the main imaging process. The method first characterizes the medium's sound speed variations using probe signals, then uses this information to pre-correct the imaging process, thereby improving resolution without excessive complexity in the main imaging step.
Solution Approach 2:
The patent introduces an intermediary characterization step that measures wavefront aberrations caused by sound speed variations. This intermediary process creates a correction map that mediates between the heterogeneous medium and the imaging system, allowing high-resolution imaging without directly confronting the complexity of sound speed variations during imaging.
2Measurement precision
If focused beamforming is used to improve image resolution, then the resolution is improved, but the acquisition time increases significantly
Solution Approach 1:
The patent performs wavefront characterization and aberration measurement in advance before the actual imaging acquisition. By preparing correction information beforehand, the method enables faster imaging acquisitions while maintaining high resolution, as the correction is already in place rather than requiring time-consuming focused beamforming for each image.
Solution Approach 2:
The patent changes the approach from time-intensive focused beamforming to a method that uses pre-measured wavefront parameters and aberration corrections. By transforming the problem into one of parameter measurement and correction, the system achieves high resolution with significantly reduced acquisition time.
3Ease of operation
If the medium is assumed homogeneous with constant sound speed, then the imaging process is simplified, but the image quality is degraded due to aberrations
Solution Approach 1:
The patent applies local quality by measuring and correcting sound speed variations at different locations within the medium. Instead of assuming uniform sound speed everywhere, the method characterizes local aberrations using wavefront sensing and applies location-specific corrections, thereby maintaining simple imaging operations while improving image quality through localized adjustments.
Solution Approach 2:
The patent introduces an intermediary wavefront sensing process that measures the actual sound speed variations in the medium. This intermediary measurement creates a correction map that mediates between the simplified imaging assumption and the complex reality of heterogeneous media, allowing simple imaging operations to produce high-quality images.
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
This approach enables precise and local evaluation of focusing quality, improving image resolution and contrast by accounting for variations in sound speed, thereby enhancing the accuracy of ultrasonic characterization in heterogeneous environments.
Implementation Method 1
Conventional ultrasound methods use an array 10 of piezoelectric transducers 11 which can emit and/or receive ultrasonic pulses independently
Implementation Method 2
The speed of sound is therefore far from homogeneous, and can vary, for example, between 1450 ms for fatty tissue and 1600 ms for the liver. Variations in sound speed cause the waves to be phase-shifted differently depending on the locations through which they propagate
Implementation Method 3
This wave is reflected by the diffusers 21 of the medium 20 and the backscattered field is recorded by each of the transducers 11 as a function of time
Data Source
Figure 1A~1B
Figure 1C~2
Figure 3~4
AI summary
Ultrasonic characterization method of a medium comprising a step of generating a series of incident ultrasonic waves, a step of generating an experimental reflection matrix Rui(t) defined between the emission basis (i) at the input and a reception basis (u) at the output, a step of determining a focused reflection matrix RFoc(rin, rout, δt) of the medium between a virtual input transducer (TVin) calculated from an input focusing of the experimental reflection matrix and a virtual output transducer (TVout) calculated from an output focusing of the experimental reflection matrix, the responses of the virtual output transducer (TVout) being taken at a time instant shifted by an additional delay δt relative to a time instant of the responses of the virtual input transducer (TVin).