Shear Wave Imaging with Spatial-Temporal PRF Enhancement
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Solution Overview
Problem
The maximum pulse repetition frequency (PRF) in shear wave imaging is insufficient for tracking fast shear waves in highly stiff media, leading to under-sampling and inaccurate estimation of shear wave velocity.
Innovation Solution
Combining tissue displacements from different lateral locations, adjusting for shear wave velocities and attenuations, to form a smooth displacement profile, thereby increasing the effective sampling rate and accurately estimating shear wave velocity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the maximum pulse repetition frequency (PRF) is used for tracking shear waves, then the sampling rate is sufficient for soft tissue, but the sampling rate becomes insufficient for tracking fast shear waves in highly stiff media
Solution Approach 1:
The patent combines displacement measurements from multiple lateral locations to create a composite displacement profile. By merging data from several locations that are sampled at the maximum PRF, the system effectively increases the sampling rate for tracking fast shear waves in stiff media, thereby resolving the contradiction between speed and measurement precision
Solution Approach 2:
The patent transitions from single-location temporal sampling to multi-location spatial-temporal sampling. By adding the spatial dimension of multiple lateral locations to the temporal sampling, the system achieves effective oversampling of fast shear waves without requiring higher PRF at each individual location
2Productivity
If separable tracking transmissions at different frequencies or coded pulses are used to increase PRF, then the sampling rate increases, but artifacts from clutter noise and displacement estimation errors increase
Solution Approach 1:
The patent uses identical tracking pulses at the maximum PRF across multiple lateral locations, creating copies of the same measurement process at different spatial positions. This approach avoids the artifacts introduced by different frequencies or coded pulses while still achieving effective oversampling through spatial-temporal combining
Solution Approach 2:
The system uses the existing maximum PRF tracking capability to serve multiple locations simultaneously, and the combined data from these locations serves to effectively increase the sampling rate. The system leverages its own existing resources rather than introducing new pulse sequences that would cause artifacts
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 allows for more accurate estimation of shear wave velocity in both stiff and less stiff media by enhancing the effective sampling rate, providing more reliable diagnostic information.
Implementation Method 1
A transducer transmits a pushing pulse. The pushing pulse generates a shear wave in tissue of a patient.
Implementation Method 2
The ultrasound imaging system tracks tissue displacements over time at a plurality of locations in a region of interest. The tissue displacements occur in response to the shear wave
Data Source
AI summary
For shear wave imaging with ultrasound, the apparent pulse repetition frequency is increased by combining displacements from different lateral locations. Different combinations based on different shear wave velocities and corresponding time shifts and/or attenuations and corresponding scalings are tested to find a smooth displacement profile for the combination. Once the smooth displacement profile is found, the corresponding shear wave velocity is estimated or determined.