Adaptive MTI Filter for Ultrasonic Blood Flow Imaging
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Solution Overview
Problem
Conventional ultrasonic diagnostic apparatuses face challenges in achieving high aliasing velocity and low flow rate detectability, particularly when imaging blood flow, due to motion artifacts and low signal-to-noise ratios, especially when using the Moving Target Indicator (MTI) filter with unequally spaced data strings.
Innovation Solution
The apparatus employs a color Doppler processing circuit with adaptive MTI filtering, using both intra-frame and inter-frame correlation matrices to calculate filter coefficients, which are then used to process power and velocity signals, improving signal quality and reducing aliasing velocity by adding echo signals and applying MTI filtering between frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed coefficient MTI filter is applied to unequally spaced data string, then the processing is simple, but motion artifact is easily generated and it cannot cope with constant changes of living body motion
Solution Approach 1:
The patent applies dynamics by making the MTI filter coefficients adaptive rather than fixed. The filter coefficients are dynamically adjusted based on the correlation between current and reference data strings, allowing the filter to adapt to changing motion conditions of the living body. This resolves the contradiction by enabling the simple fixed-coefficient structure to become a dynamic adaptive structure that maintains reliability under varying conditions.
Solution Approach 2:
The patent implements feedback by using the correlation result between the current data string and reference data string to determine the filter coefficients. The system continuously monitors the correlation and adjusts the filter accordingly, creating a closed-loop control mechanism. This feedback mechanism allows the filter to automatically adapt to motion changes, resolving the contradiction between simplicity and reliability.
2Device complexity
If conventional MTI filtering is used for minute blood flow observation, then the processing is straightforward, but signal-to-noise ratio becomes problematic and low flow rate detectability is reduced
Solution Approach 1:
The patent makes the filter adaptive to the specific characteristics of the blood flow signal by calculating correlation-based coefficients. This dynamic adaptation allows the filter to optimize its performance for detecting minute blood flows while maintaining simplicity in the overall processing approach. The adaptive coefficients are specifically tuned to enhance low flow rate detectability and improve signal-to-noise ratio.
3Productivity
If data between frames is used to improve frame rate, then the frame rate increases, but aliasing velocity decreases
Solution Approach 1:
The patent uses feedback from the correlation analysis between current and reference data strings to determine appropriate filter coefficients that account for the inter-frame data usage. This feedback mechanism allows the system to maintain high frame rates while compensating for the aliasing velocity reduction through adaptive filtering that considers the temporal relationships in the unequally spaced data.
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 enhances the frame rate and signal-to-noise ratio, allowing for more accurate imaging of blood flow with reduced motion artifacts and improved sensitivity to low flow rates, effectively addressing the limitations of conventional methods.
Implementation Method 1
an ultrasonic probe 12, an input interface circuit 13, a monitor 14, an ultrasonic transmitting circuit 20, an ultrasonic receiving circuit 21... The piezoelectric vibrator transmits an ultrasonic wave to a desired direction in a scan region based on a driving signal from the ultrasonic transmitting circuit 20, and converts the reflected wave from the subject into an electrical signal
Implementation Method 2
a color Doppler processing circuit 24... In such a Doppler imaging method, a method is generally performed in which a plurality of times of transmission and reception are performed in the same direction, a moving target indicator (MTI) filter is applied with respect to a data string thereof
Data Source
AI summary
An ultrasonic diagnostic apparatus according to an embodiment performs ultrasonic scans having a plurality of times of ultrasonic transmission and reception as a basic unit, and acquires reception signals respectively for reception rasters allocated with respect to a predetermined region of a subject. The apparatus generates first signals corresponding to the reception rasters respectively by performing adding processing or low-pass filtering having a time of the ultrasonic scan as a unit with respect to the reception signals respectively acquired for the reception rasters, and acquires power information of a moving body in the predetermined region based on a second signal to be obtained by performing an MTI filtering with respect to the first signals. The apparatus acquires velocity information of the moving body based on a third signal obtained by performing the MTI filtering with respect to the reception signals respectively acquired for the reception rasters.