Cryoablation Device Freeze-Warm Cycle Control
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Solution Overview
Problem
Cryoablation procedures face inefficiencies due to the need for repeated freeze-thaw cycles, which increase radiation exposure from fluoroscopy and complicate device repositioning, as the ice ball formed during tissue ablation temporarily adheres to the treatment site but requires thawing for repositioning.
Innovation Solution
A method and system utilizing a control unit to manage coolant flow rates to achieve a freeze-warm cycle, allowing the cryoablation device to maintain contact with the tissue while adjusting temperatures to optimize lesion creation and minimize radiation exposure by continuously delivering coolant at varying flow rates to maintain cryoadhesion without complete thawing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a freeze-thaw-freeze cycle is used to improve tissue ablation efficiency, then lesion creation is enhanced, but the ice ball thaws and requires device repositioning
Solution Approach 1:
The system dynamically adjusts coolant flow rates to control the temperature of the treatment element, transitioning between freeze and warm phases. By modulating flow rate parameters, the system achieves effective tissue ablation while maintaining cryoadhesion through precise temperature control, eliminating the need for complete thawing and repositioning.
Solution Approach 2:
The system implements periodic freeze-warm cycles where the coolant flow rate is alternated between high (for freezing) and low (for warming) rates. This periodic action creates efficient lesions through repeated freeze-thaw cycles while the ice ball remains partially adherent to the treatment element, allowing continuous treatment without complete detachment and repositioning.
2Ease of operation
If the ice ball is completely thawed to reposition the device, then device repositioning is enabled, but radiation exposure from fluoroscopy increases
Solution Approach 1:
The system replaces the mechanical/visual verification method (fluoroscopy) with a thermal control method. By using temperature sensors and flow rate control to monitor and maintain cryoadhesion, the system eliminates the need for fluoroscopic imaging to verify device position, thereby reducing radiation exposure while maintaining operational capability.
Solution Approach 2:
The treatment element self-verifies its position and adhesion status through temperature monitoring and cryoadhesion maintenance. The system uses its own thermal state and the presence of the ice ball as feedback to confirm proper positioning, eliminating the need for external fluoroscopic verification and reducing radiation exposure.
3Productivity
If high coolant flow rate is used to maintain low temperature for ablation, then tissue ablation is effective, but cryoadhesion may be broken
Solution Approach 1:
The system dynamically adjusts coolant flow rates based on real-time temperature feedback. During freeze phases, high flow rates maintain effective ablation temperatures. During warm phases, flow rates are reduced to prevent complete thawing and maintain cryoadhesion. This dynamic adjustment allows the system to optimize both ablation effectiveness and adhesion stability throughout the treatment cycle.
Solution Approach 2:
The system changes coolant flow rate parameters to achieve different temperature states. High flow rates produce low temperatures for effective ablation, while reduced flow rates allow temperature rise to maintain cryoadhesion. By modulating this critical parameter, the system resolves the contradiction between achieving effective ablation and maintaining stable adhesion.
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 enhances lesion creation efficiency and reduces the need for fluoroscopy, improving patient safety by maintaining effective tissue ablation without the need for frequent device repositioning and associated radiation exposure.
Implementation Method 1
a pressurized refrigerant is circulated within the tip of a cryoablation catheter, where the refrigerant expands and absorbs heat from surrounding tissue
Implementation Method 2
As the tissue freezes, blood adjacent the treatment site may also freeze, creating an 'ice ball'
Implementation Method 3
supplying coolant to the distal portion of the medical device at a first flow rate, the first flow rate causing the distal portion of the medical device to reach a first temperature
Implementation Method 4
the tissue freezes, blood adjacent the treatment site may also freeze, creating an 'ice ball' that temporarily adheres the treatment element to the tissue at the treatment site, a phenomenon called cryoadhesion
Data Source
AI summary
A method and system for improved lesion creation. The method generally includes positioning a treatment element of a medical device proximate an area of target tissue and operating a control unit in accordance with a duty cycle, that includes at least one freeze-warm cycle, each freeze-warm cycle including: supplying coolant to the treatment element at a first flow rate that causes the treatment element to reach a first temperature, the first temperature causing ablation of the target tissue and cryoadhesion between the treatment element and target tissue, and supplying coolant to the treatment element at a second flow rate that causes the treatment element to reach a second temperature, the second temperature being higher than the first temperature and the second flow rate being lower than the first flow rate, the second temperature being above a temperature at which ablation occurs and below a temperature at which cryoadhesion is broken.