Passive Cavitation Mapping for HIFU Therapy Monitoring
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Solution Overview
Problem
Current monitoring systems for high-intensity focused ultrasound (HIFU) therapy lack a reliable real-time method to detect and characterize cavitation, which is crucial for effective treatment, as existing methods are either invasive, less sensitive, or only detect post-treatment cavities.
Innovation Solution
A system comprising a plurality of pressure wave detectors and processing means that can operate in both active and passive modes, allowing for the localization and mapping of bubbles during HIFU treatment by detecting ultrasound emissions at frequencies different from the generator frequency, enabling real-time monitoring of cavitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If passive cavitation detectors (PCDs) are used to monitor cavitation during HIFU therapy, then cavitation detection capability is improved, but the system can only provide information for a fixed region due to fixed focus
Solution Approach 1:
The patent divides the monitoring system into multiple independently focusable detector elements arranged in an array. Each detector element can be electronically focused on different regions of interest, allowing the system to segment the monitoring task across multiple spatial zones rather than using a single fixed-focus detector.
Solution Approach 2:
The patent implements dynamic focusing capability where the focus of each detector element can be electronically adjusted in real-time. This allows the system to dynamically shift monitoring attention between different regions of the treatment zone, adapting to moving cavitation activity throughout the therapy process.
2Loss of information
If B-mode ultrasound imaging is used to detect cavities, then visualization of bubble activity is enabled, but detection is only possible after HIFU excitation has ceased due to interference
Solution Approach 1:
The patent extracts the cavitation detection function from the therapeutic HIFU signal by using passive detection of acoustic emissions. The system separates the monitoring function from the treatment function, allowing cavitation detection to occur independently during HIFU exposure without requiring the therapeutic ultrasound to be turned off.
Solution Approach 2:
The patent uses broadband acoustic emissions from cavitating bubbles as an intermediary signal for monitoring. These emissions serve as a mediator that carries information about cavitation activity at frequencies distinct from the therapeutic HIFU frequency, enabling simultaneous treatment and monitoring.
3Measurement precision
If high-frequency broadband transducers are used as passive cavitation detectors, then cavitation monitoring sensitivity is improved, but the detectors have fixed focus providing information for a fixed region only
Solution Approach 1:
The patent segments the monitoring function across multiple detector elements in an array, with each element capable of independent focusing. This segmentation allows the system to maintain high sensitivity at each focus point while collectively covering a larger monitoring area through coordinated operation of multiple elements.
Solution Approach 2:
The patent transitions from a single fixed-focus detector to a multi-element array system that adds spatial dimensionality to the monitoring capability. By electronically controlling the focus of each element, the system can sweep through different regions in three-dimensional space, effectively expanding the monitoring volume without sacrificing sensitivity.
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 provides effective real-time localization and mapping of cavitation, enhancing heat deposition and treatment monitoring, while avoiding interference with the therapeutic ultrasound, and can differentiate between inertial and stable cavitation types.
Implementation Method 1
The cavitating bubbles re-emit part of the incident ultrasound over a range of frequencies that are different to the HIFU excitation frequency
Implementation Method 2
One option is to use high-frequency broadband transducers to act as passive cavitation detectors (PCDs) that record the acoustic emissions from cavitating bubbles
Implementation Method 3
hyperechogenic regions in B-mode ultrasound images can enable detection and localization of bubble activity using time-of-flight information
Implementation Method 4
emissions that have a higher frequency content than the original HIFU source will be absorbed more readily by surrounding tissue, which means that cavitation can greatly enhance heat deposition
Implementation Method 5
The at least one detection frequency may comprise a range of detection frequencies, the generator frequency being outside the range. The range of frequencies that the detectors can detect may, for example, be determined by one or more filters arranged to filter the detector signal
Data Source
AI summary
Apparatus for locating bubbles in a subject comprises a plurality of pressure wave detectors arranged to operate as passive detectors to generate output signals in response to the receipt of pressure waves generated at a source comprising at least one bubble, and processing means arranged to receive signals from the detectors and to determine from the signals the position of the source.