H-FIRE Interpulse Delay Patterns for Stable Tissue Ablation
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Solution Overview
Problem
Existing pulsed electric field treatments for tissue ablation, such as high-frequency irreversible electroporation (H-FIRE), face challenges with high lethal electric field thresholds, muscle contractions, bubble formation, and electrical arcing, which complicate clinical applications and reduce efficacy.
Innovation Solution
The use of extended interpulse delays in bipolar and monopolar pulse delivery strategies to minimize bubble formation and arcing, while maintaining effective tissue ablation, by adjusting the temporal infrastructure of pulsed electric fields.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional long monopolar pulses are used for IRE treatment, then tissue ablation is achieved, but muscle stimulation and arrhythmias occur
Solution Approach 1:
The patent segments the single long monopolar pulse into multiple shorter bipolar pulses with alternating polarity. Each bipolar pulse consists of a positive phase followed by a negative phase, with the negative phase occurring after a delay period. This segmentation allows the treatment to achieve cumulative electroporation effects while preventing continuous muscle stimulation, as each negative phase provides local repolarization that reduces excitation of voltage-gated sodium channels.
Solution Approach 2:
The patent implements periodic bipolar pulsing with alternating polarity phases. The waveform delivers multiple bipolar pulses in rapid succession, with each pulse containing a positive phase followed by a negative phase after a delay. This periodic alternating polarity action maintains electroporation efficacy through cumulative effect while preventing sustained muscle contraction by providing repeated repolarization opportunities.
2Object-affected harmful factors
If high-frequency bipolar pulses with short interpulse delays are used, then muscle contractions are reduced, but bubble formation and electrical arcing increase
Solution Approach 1:
The patent introduces a delay period between the negative phase of one bipolar pulse and the positive phase of the next bipolar pulse. This preliminary delay action allows time for bubble dissolution and electrode repolarization before the next pulse delivers energy. By implementing this delay, the system prevents bubble accumulation that would otherwise lead to electrical arcing, while maintaining the high-frequency pulsing pattern that reduces muscle contractions.
3Volume of moving object
If higher voltages are applied to achieve similar ablation volumes with H-FIRE, then aablation volume increases, but heat production and tissue damage increase
Solution Approach 1:
The patent employs dynamic adjustment of pulse parameters including variable pulse widths, adjustable delays between phases, and modulated pulse amplitudes. The system can adapt the temporal infrastructure of the bipolar pulses to optimize the balance between achieving sufficient ablation volume and minimizing thermal damage. By dynamically controlling the timing and duration of electrical phases, the system achieves effective electroporation with reduced Joule heating compared to static high-voltage approaches.
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 reduces muscle stimulation, bubble formation, and arcing, allowing for more controlled and efficient tissue ablation with lower energy dosages and potentially eliminating the need for neuromuscular blocking agents.
Implementation Method 1
Electroporation is a biological phenomenon in which cells exhibit increased membrane permeability upon exposure to high amplitude electric fields. Increased permeabilization is presumably due to creation of defects in the cell membrane that increase transport of ionic species and macromolecules
Implementation Method 2
This is due to the local repolarization that occurs with each negative phase prior to activation of the minimum number of voltage-gated sodium channels (VGSCs) required for excitation
Implementation Method 3
Unlike conventional ablative therapies in which temperature is manipulated to nonspecifically denature proteins, IRE directly affects cellular membranes without significant local heating
Implementation Method 4
Electrochemical events occurring at the electrode-tissue interface mediate the charge exchange between the metallic electrodes and electrolyte. Conventional irreversible electroporation (IRE) and high-frequency IRE (H-FIRE) are typically delivered using one or more pairs of monopolar or bipolar needle electrodes
Data Source
AI summary
High-frequency irreversible electroporation (H-FIRE) is a tissue ablation modality employing bursts of electrical pulses in a positive phase-interphase delay-negative phase-interpulse delay pattern. Despite accumulating evidence suggesting the significance of these delays, their effects on therapeutic outcomes from clinically-relevant H-FIRE waveforms have not been studied extensively. The present invention provides methods of pulse delivery, including delays, that mitigate bubble formation and/or minimize the risk of arcing, such as due to the presence of bubbles, and/or minimize muscle stimulation are described herein.