Ultrasonic Imaging Phase Cancellation Microbubble Contrast
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Solution Overview
Problem
Current ultrasonic imaging techniques face challenges in achieving a high signal-to-noise (S/N) ratio for contrast echo images, particularly in distinguishing microbubble contrast medium signals from tissue harmonic components, leading to suboptimal diagnostic images.
Innovation Solution
The method involves summing three echo signals transmitted with a common envelope signal and rotating the carrier wave phase by 120° for each operation, canceling fundamental and second-order harmonic components from linear scattering bodies, and using a specific hardware configuration to suppress unwanted signals, allowing for clear differentiation between contrast medium and tissue harmonic components without the need for filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional ultrasonic imaging techniques are used to obtain contrast echo images, then the imaging process is simple, but the signal-to-noise ratio is low and it is difficult to distinguish microbubble contrast medium signals from tissue harmonic components
Solution Approach 1:
The imaging process is segmented into multiple transmitting/receiving operations (first, second, and third operations) with different carrier wave phases. Each operation captures echo signals that contain different combinations of fundamental wave components and harmonic components. By separating the acquisition into distinct phased operations, the system can later selectively cancel unwanted components through signal processing, achieving high S/N ratio while maintaining manageable process complexity through systematic segmentation.
Solution Approach 2:
The system changes the phase parameter of the carrier wave across different transmitting/receiving operations (0°, 120°, and 240° phases). This parameter change enables the fundamental wave components from linear scattering bodies to accumulate with different phases, allowing them to be canceled out through coherent summation. Meanwhile, the nonlinear harmonic components from microbubbles maintain consistent phase relationships, preserving their signal integrity and achieving high contrast visualization.
2Measurement precision
If multiple transmitting/receiving operations are performed to improve signal discrimination, then the signal-to-noise ratio improves, but the imaging time increases
Solution Approach 1:
The system employs periodic transmitting/receiving operations with carrier waves phased at 0°, 120°, and 240°. This periodic structure allows for systematic cancellation of fundamental wave components when the three echo signals are coherently summed. The periodic nature of the phase progression enables efficient signal processing that achieves high signal discrimination while minimizing the number of required operations, thus reducing imaging time compared to non-periodic approaches.
3Measurement precision
If filtering methods are used to separate contrast medium signals from tissue harmonics, then signal separation is achieved, but image resolution deteriorates
Solution Approach 1:
The system extracts and cancels fundamental wave components from linear scattering bodies by performing coherent summation of echo signals with 120° phase differences. This extraction method selectively removes unwanted tissue harmonic components while preserving the nonlinear harmonic components from microbubble contrast media. The approach achieves signal separation without requiring post-processing filters that would degrade image resolution, as the cancellation occurs in the signal domain before image reconstruction.
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 the acquisition of high-resolution, high-S/N ratio images that effectively distinguish microbubble contrast medium signals from tissue harmonic components, enhancing diagnostic capabilities in medical imaging.
Implementation Method 1
the microbubbles with a diameter of about one micron vibrate with great amplitude in resonance with the ultrasonic wave of several megahertz that is used for ultrasonic diagnosis, efficiently scatter the ultrasonic waves of this frequency range as a result
Implementation Method 2
Microbubble-based ultrasonic contrast media are characterized by their strong nonlinearity. This is because the microbubbles have the nature that an increase in their volume under negative pressure becomes much greater than a decrease in their volume under a positive pressure of the same amplitude. For this reason, an echo signal that has been scattered by the microbubbles contains the large quantity of second-order harmonic components having twice the frequency of the transmitted signal
Implementation Method 3
the microbubbles with a diameter of about one micron vibrate with great amplitude in resonance with the ultrasonic wave of several megahertz that is used for ultrasonic diagnosis
Implementation Method 4
summing three echo signals obtained by transmitting/receiving a sound pressure pulse three times with a common envelope signal and rotating a phase of a carrier wave in steps of 120° enables components up to the second-order harmonic component to be canceled
Data Source
AI summary
This invention provides an ultrasonic imaging system that implements imaging by distinguishing sharply and definitely the echo components generated by scattering in a microbubble contrast medium, from the tissue harmonic components generated by nonlinear propagation of a transmitted pulse. This ultrasonic imaging system, constructed to transmit/receive ultrasonic pulses to/from a living body and form a contrast image of the inside of the living body by using the contrast-imaging microbubbles, repeats the transmitting/receiving operations four times in all, under the same transmitting/receiving focus conditions at different phase angles [(a)=0°, (b)=120°, (c)=−120°, (d)=180°] of the carrier of a transmitted pulse wave including a common envelope signal, sums up three time-series receive echo signals associated with (a), (b), (c), forms the contrast image, sums up two time-series receive echo signals associated with (a), (d), forms an image of the living body having a nonlinear pulse propagation property, and makes a superimposed display of the two kinds of images.