Shear Wave Velocity Mapping in Biological Tissues
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Solution Overview
Problem
Conventional elastography methods that utilize acoustic radiation force excitations and displacement encoding with MR imaging require long acquisition times and produce low resolution elastography maps, limiting their effectiveness in mapping shear wave velocity and shear modulus in biological tissues.
Innovation Solution
A method and system that use an ultrasound transducer to generate mechanical excitations at multiple locations within a region of interest, with an MRI system capturing phase images encoded by motion encoding gradients, allowing for the generation of high-resolution shear wave velocity maps by combining shear wave speed values from multiple excitations, and optionally using a reference image to minimize phase variations not caused by mechanical excitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional elastography methods use acoustic radiation force excitations with displacement encoding and MR imaging, then shear wave velocity and shear modulus can be measured in biological tissues, but the acquisition time is long and the resolution of elastography maps is low
Solution Approach 1:
The patent segments the measurement process by acquiring multiple phase images at different time points after mechanical excitation. Each phase image captures the shear wave at a different propagation stage, and these segmented measurements are then combined to construct high-resolution elastography maps. This segmentation approach enables both high resolution and reduced acquisition time by parallelizing the measurement of different spatial locations.
Solution Approach 2:
The patent employs periodic mechanical excitation using acoustic radiation force to generate shear waves at regular intervals. By applying periodic excitations and capturing phase images at corresponding periodic time points, the system efficiently collects data from multiple locations without requiring continuous scanning, thereby reducing overall acquisition time while maintaining high measurement precision.
2Measurement precision
If multiple phase images are acquired to generate shear wave velocity maps, then high resolution measurements can be achieved, but the acquisition time increases
Solution Approach 1:
The patent performs preliminary mechanical excitation of the tissue before image acquisition begins. The acoustic radiation force excitation is applied in advance, generating shear waves that propagate through the tissue during the phase image acquisition. This preliminary action allows multiple phase images to be captured simultaneously at different time points without requiring sequential excitation, thereby improving acquisition rate while maintaining precision.
Solution Approach 2:
The system maintains continuous useful action by acquiring phase images continuously after the initial mechanical excitation. Rather than stopping between measurements or using discrete sequential acquisitions, the system continuously captures the propagating shear wave at multiple time points, maximizing the information obtained from each excitation event and improving overall productivity.
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 rapid acquisition of high-resolution shear wave speed maps within a short breath-hold time, improving the precision and spatial extent of measurements, and allowing for the determination of shear modulus values, which can be used for detecting diseased tissue and assessing mechanical changes.
Implementation Method 1
mechanical excitations may be generated, for example, using acoustic radiation force (ARF) impulses applied to the region of interest
Implementation Method 2
Motion encoding gradients (MEGs) encode a propagating shear wavefront caused by the mechanical excitation
Data Source
AI summary
A method for mapping shear wave velocity in biological tissues includes using an ultrasound transducer to generate mechanical excitations at a plurality of locations in a region of interest. An MRI system is used to capture a phase image of each mechanical excitation, wherein motion encoding gradients (MEGs) of the MRI system encode a propagating shear wavefront caused by the mechanical excitation. A plurality of shear wave velocity maps is generated based on the phase images, wherein each shear wave velocity map depicts velocity between adjacent propagating shear wavefronts. The shear wave speed values are combined to generate a composite shear wave velocity map of the region of interest.