Histotripsy Excitation Sequences for Bubble Cloud Formation
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Solution Overview
Problem
Histotripsy therapy transducers with high F-numbers have low efficiency due to nonlinear acoustic propagation, leading to shockwave formation, which results in pre-focal thermal injuries when targeting deep tissues through skeletal anatomical obstructions, necessitating the development of optimized excitation sequences for enhanced tissue homogenization and reduced thermal injury.
Innovation Solution
The implementation of optimized excitation sequences for ultrasound therapy transducers, characterized by an initiation pulse followed by a shock scattering pulse with specific timing, pressure amplitude, and pulse repetition frequency, to create and maintain bubble clouds in tissues while minimizing tissue heating and preserving vital structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If Histotripsy therapy transducers with high F-numbers are used to target deep tissues, then the treatment depth is increased, but the efficiency decreases due to nonlinear acoustic propagation leading to shockwave formation and pre-focal thermal injuries
Solution Approach 1:
The patent applies preliminary action by delivering an initiation pressure waveform before the main scattering pressure waveforms. This initiation pulse creates the first bubble cloud that serves as a precursor, enabling subsequent shock scattering to occur more efficiently and reducing the overall energy required for deep tissue treatment while minimizing pre-focal thermal injury.
Solution Approach 2:
The patent employs periodic action through a specific pulse sequence structure: one initiation pressure waveform followed by multiple scattering pressure waveforms delivered at optimized intervals. This periodic pattern allows the bubble cloud to develop systematically, with each scattering pulse building upon the previous one to achieve cumulative cavitation effects deep in tissue without excessive heating.
2Quantity of substance
If high pressure amplitude acoustic pulses are delivered to induce controlled cavitation in deep tissues, then bubble cloud formation is achieved, but pre-focal thermal injuries occur due to energy deposition along the propagation path
Solution Approach 1:
The patent segments the acoustic energy delivery into distinct functional components: an initiation pressure waveform with specific characteristics followed by multiple scattering pressure waveforms. Each segment serves a specific purpose in bubble cloud development, allowing energy to be distributed more efficiently through time and space, reducing cumulative thermal load on pre-focal tissues while maintaining effective cavitation at the target.
Solution Approach 2:
The patent applies parameter changes by optimizing multiple variables including pressure amplitude, pulse duration, pulse repetition frequency, and time intervals between initiation and scattering pulses. These parameter adjustments enable the system to achieve threshold cavitation effects deep in tissue while keeping time-averaged energy deposition below thermal damage thresholds in intervening tissues.
3Reliability
If the pulse repetition frequency is increased to maintain bubble clouds in deep tissues, then cavitation efficacy is improved, but tissue heating increases
Solution Approach 1:
The patent uses periodic action with an optimized pulse repetition frequency that balances bubble cloud maintenance with thermal safety. The periodic delivery of scattering pressure waveforms at specific intervals allows the bubble cloud to persist through controlled cavitation cycles while providing thermal relaxation time between pulses, preventing excessive heat accumulation in deep tissues.
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 optimized sequences improve the efficiency of Histotripsy, reducing pre-focal heat, increasing the probability of initiating and maintaining bubble clouds, and allowing selective ablation of fibrous tissues while preserving vital structures, thus enhancing the safety and efficacy of deep tissue treatments.
Implementation Method 1
delivering an initiation pressure waveform from an ultrasound therapy transducer into tissue, the initiation pressure waveform being configured to produce at least one bubble in the tissue
Implementation Method 2
delivering a scattering pressure waveform within a life-cycle of the at least one bubble into the at least one bubble, and producing cavitation nuclei near the at least one bubble with the scattering pressure waveform
Data Source
AI summary
Methods and devices for producing cavitation in tissue are provided. In one embodiment, a shock scattering method of Histotripsy therapy comprises delivering an initiation pressure waveform from an ultrasound therapy transducer into tissue, the initiation pressure waveform being configured to produce at least one bubble in the tissue, delivering a scattering pressure waveform from the ultrasound therapy transducer into the at least one bubble within a life-cycle of the at least one bubble, and producing cavitation nuclei near the at least one bubble with the scattering pressure waveform. The scattering pressure waveform can be delivered during the life-cycle of the at least one bubble. In some embodiments, the scattering pressure waveform is delivered within 5 μs to 1 s of the initiation pressure waveform. Systems for performing shock scattering Histotripsy therapy are also discussed.