Ultrasound Autofocusing via Microbubble Phase Correction
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Solution Overview
Problem
Current ultrasound focusing techniques, particularly for transcranial procedures, face challenges due to skull attenuation and irregularities, leading to suboptimal focusing and potential damage to healthy tissue, especially when using short pulses in histotripsy, where precise alignment of pulse peaks is crucial for effective treatment.
Innovation Solution
The approach combines time-of-flight measurements with phase adjustments to align pulse peaks and envelopes, ensuring precise alignment of short pulses and phase alignment using transient acoustic reflectors like microbubbles, allowing for improved focusing and energy delivery during ultrasound therapy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional ultrasound focusing techniques are used for transcranial procedures, then the treatment can be performed noninvasively, but the skull attenuation and irregularities cause suboptimal focusing and potential damage to healthy tissue
Solution Approach 1:
The system performs preliminary measurements of acoustic reflections from microbubbles before the actual treatment. These pre-treatment measurements are used to calculate phase correction values that will be applied during the treatment phase, allowing the system to compensate for skull aberrations in advance and achieve precise focusing without requiring invasive probes
Solution Approach 2:
The patent introduces microbubbles as an intermediary acoustic reflector between the ultrasound transducer and the target tissue. These microbubbles serve as a temporary reference target that enables the system to measure and characterize the acoustic path through the skull, allowing for precise phase correction and focusing without requiring direct contact with the brain tissue
2Manufacturing precision
If phase correction is performed using pre-treatment measurements, then focusing precision is improved, but the treatment time increases due to the need for measurements and calculations
Solution Approach 1:
The system performs all necessary phase correction calculations and parameter optimizations before the actual treatment begins. By completing the measurement and computation phases in advance, the system establishes the optimal transmission parameters beforehand, allowing the actual treatment to proceed more efficiently without requiring real-time adjustments
Solution Approach 2:
The system uses the microbubble reflections to automatically characterize the acoustic path and generate the necessary phase correction values without requiring manual intervention or real-time external measurements. The microbubbles themselves serve as the reference target, eliminating the need for separate calibration procedures or invasive probes during treatment
3Productivity
If short pulses are used for histotripsy, then the treatment efficiency is improved, but the alignment precision of pulse peaks becomes more difficult to achieve
Solution Approach 1:
The patent introduces microbubbles as an intermediary reference that enables precise measurement of acoustic path differences. By using these microbubbles as temporary targets, the system can accurately determine the phase corrections needed for short pulse alignment, even though the pulses themselves are too short to provide sufficient measurement data directly
Solution Approach 2:
The system replaces direct mechanical alignment methods with acoustic field-based phase correction. Instead of relying on mechanical positioning or direct observation of pulse peaks (which is difficult with short pulses), the system uses acoustic reflections from microbubbles to calculate and apply precise phase corrections, enabling accurate alignment of short pulses for effective histotripsy treatment
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 method enhances the accuracy and efficiency of ultrasound focusing through the skull, ensuring that ultrasound energy is effectively concentrated at the target site with minimal damage to surrounding tissue, even with short pulses, thereby improving therapeutic outcomes.
Implementation Method 1
The transducer converts an electronic drive signal into mechanical vibrations, resulting in the emission of acoustic waves
Implementation Method 2
The transducer may be geometrically shaped and positioned along with other such transducers so that the ultrasound energy they emit collectively forms a focused beam at a 'focal zone' corresponding to (or within) the target tissue region
Implementation Method 3
Impediments to transcranial ultrasound procedures include strong attenuation and the distortions caused by irregularities in the skull's shape, density, and sound speed
Implementation Method 4
Another approach to estimating the wave aberrations resulting from the skull involves use of an acoustic reflector (e.g., a small cloud of microbubbles) in the focus zone. By transmitting the ultrasound waves to the microbubbles and receiving reflections therefrom, the amplitudes and/or phases associated with the reflected ultrasound can be determined
Implementation Method 5
During tumor ablation, a piezoceramic transducer is placed externally to the patient, but in close proximity to the tissue to be ablated
Data Source
AI summary
In an ultrasound system, echo focusing is performed to align ultrasound pulse peaks, establishing the phase delay required for each ultrasound transducer element, and the temporal displacements among pulses are determined using, for example, time-of-flight (ToF) measurements. The combined approach aligns the phases and the envelopes of pulses delivered by the active transducer elements that contribute energy during treatment. Moreover, it permits long pulses to be used for phase alignment in the preparatory stage and perfectly aligned short pulses in the sonication stage.