Doppler Measurement System Random Sweep Clutter Suppression
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Solution Overview
Problem
Conventional Doppler ultrasound systems face challenges in accurately measuring high-velocity blood flow due to the attenuating effect of frame compounding on fast-moving objects, which results in biased velocity estimates and reduced frame rates, leading to aliasing and compromised beam profiles.
Innovation Solution
A Doppler shift flow measurement system utilizing a random generator to produce a sequence of ultrasonic transmit pulses with adjustable steering angles, allowing for a random sweep that suppresses clutter by spreading the clutter spectrum, eliminating the need for compounding and enabling high-resolution imaging with unaliased Doppler frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If frame compounding is used to improve beam profile and suppress off-focus echoes, then spatial resolution is improved, but fast-moving objects are attenuated and velocity estimates become biased
Solution Approach 1:
The patent segments the Doppler measurement process into two independent parts: (1) using a small number of plane wave angles (e.g., 3-5 angles) to acquire high-frame-rate Doppler data, and (2) using separate beamforming techniques to suppress off-focus echoes. This segmentation allows each part to be optimized independently, avoiding the trade-off present in conventional compounding where increasing the number of angles improves resolution but reduces frame rate and attenuates fast movers.
Solution Approach 2:
The patent extracts the clutter suppression function from the frame compounding process. Instead of using compounding to simultaneously achieve both resolution improvement and clutter suppression, the patent separates these functions: it uses a limited number of plane wave angles to preserve high frame rates for Doppler measurement, and applies additional signal processing specifically for clutter suppression, thereby preventing attenuation of fast-moving objects.
2Manufacturing precision
If the number of plane wave angles N is increased to improve beam profile, then spatial resolution is improved, but the slow-time sampling rate is reduced and unaliased Doppler frequency limit is reduced
Solution Approach 1:
The patent segments the imaging function from the Doppler measurement function. It uses a small number of plane wave angles (N=3-5) specifically for acquiring high-frame-rate Doppler data, while separately applying beamforming and clutter suppression techniques. This segmentation decouples the beam profile quality from the Doppler sampling rate, allowing both to be optimized independently without the trade-off that exists in conventional compounding.
3Reliability
If conventional compounding is used to suppress off-focus echoes, then image quality is improved, but frame rate is reduced to PRF/N
Solution Approach 1:
The patent segments the image formation process from the Doppler data acquisition process. It acquires Doppler data using a limited number of plane wave angles at high frame rates, then applies separate beamforming and clutter suppression processing. This segmentation allows the system to maintain high frame rates (PRF) rather than reducing to PRF/N, while still achieving high image quality through the separate processing steps.
Solution Approach 2:
The patent extracts the clutter suppression function from the frame compounding operation. Instead of using compounding to simultaneously achieve both image quality improvement and high frame rates, it separates these functions: acquiring Doppler data at high frame rates with minimal angles, then applying dedicated signal processing for clutter suppression, thereby preserving productivity while maintaining reliability.
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 system achieves improved spatial resolution and unaliased Doppler frequencies, effectively suppressing clutter and providing accurate velocity measurements even at high velocities, while maintaining high frame rates.
Implementation Method 1
ultrasonic pulses are directed into a human subject along a path which intersects a blood vessel or its surrounding tissue
Implementation Method 2
ultrasound energy from a transmitted pulse is backscattered from blood within the vessel or chamber and returns to a transducer
Implementation Method 3
A Doppler shift occurs when the frequency of the scattered echoes is shifted, in relation to the frequency of the transmitted pulse, as occurs for example if the blood has a velocity component along the direction of propagation
Data Source
AI summary
A Doppler measurement system includes a random generator outputting a control signal encoding a random selection, and an ultrasonic array transducer for emitting a sequence of transmit pulses at a target at either an adjustable steering angle (plane wave imaging) or from a selectable non-sequential transducer element order (synthetic aperture imaging) corresponding to the random selection and for receiving an echo of each transmit pulse reflected from the target. Each transmit pulse is independently adjusted to a steering angle (plane wave imaging) or selectable transducer element order (synthetic aperture imaging) corresponding to a unique random selection so that the sequence of transmit pulses is a random sweep. The system can also include a memory for storing echo data, and a processor connected to the memory for using transmit data and echo data to extract a Doppler parameter. Methods of Doppler measurement and computer-readable medium can incorporating the measurement system.