Dual-Stage Cryocooler Circuit for Low-Pressure Cryoablation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing cryoprobes struggle to form ice balls of desirable sizes and times when operating at pressures lower than typical cryoablation pressures, especially in navigating tortuous and narrow body passageways.
Innovation Solution
A dual-stage cryocooler system with a primary and secondary fluid circuit, featuring multiple heat exchangers and Joule-Thomson orifices, allows for recuperative heat exchange to achieve effective cooling or heating at the cryoprobe tip, even at reduced pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If cryofluid is delivered at pressures lower than typical supply pressure (e.g., 3500 psi), then the cryoprobe can navigate tortuous and narrow body passageways, but insufficient cooling is achieved and ice balls of desirable sizes are not formed within desirable times
Solution Approach 1:
The system performs preliminary cooling actions before the final cryoablation phase. A secondary fluid circuit with its own heat exchanger pre-cools the primary cryofluid before it reaches the expansion device, ensuring that even at reduced pressures, the fluid is sufficiently cold to form ice balls of desirable sizes within the required time frame
Solution Approach 2:
A secondary fluid circuit acts as an intermediary cooling system. This separate circuit with independent high and low pressure streams and heat exchangers provides additional cooling capacity to the primary cryofluid, enabling the primary system to operate at lower pressures while maintaining effective cooling performance
2Device complexity
If a single fluid circuit is used, then the device structure is simpler, but the cooling capacity is insufficient to form ice balls of desirable sizes within desirable times
Solution Approach 1:
The cooling system is segmented into two independent fluid circuits: a primary circuit for delivering cryofluid to the expansion device and a secondary circuit for providing additional cooling capacity. Each circuit has its own heat exchanger and fluid flow paths, allowing independent optimization of each cooling stage
Solution Approach 2:
The primary and secondary fluid circuits are merged at the heat exchange stage, where the low pressure stream of the secondary fluid provides additional cooling to the primary cryofluid. This combination of two separate cooling systems delivers the enhanced cooling capacity needed to form ice balls of desirable sizes within desirable times
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 enables the formation of ice balls suitable for cryoablation by precooling the primary fluid using the secondary fluid circuit, ensuring effective cryogenic or heating operations in flexible catheters.
Implementation Method 1
a cryoprobe uses the Joule-Thomson effect to produce cooling or heating of the probe tip. In such cases, the expansion of a cryofluid in the cryoprobe from a higher pressure to a lower pressure leads to cooling of the device tip
Implementation Method 2
Heat transfer between the expanded cryofluid and the outer walls of the cryoprobe leads to formation of an ice ball, in the tissue around the tip and consequent cryoablation the tissue
Data Source
AI summary
A cryoablation tool has a primary fluid circuit for cryogenically cooling or heating tissue surrounding the distal portion of the cryoablation tool. The primary fluid circuit has a primary-primary heat exchanger facilitating recuperative heat exchange between a high pressure stream of a primary fluid and a low pressure stream of the primary fluid. The cryoablation tool has a secondary fluid circuit having a secondary-secondary heat exchanger for permitting recuperative heat exchange between a high pressure stream of a secondary fluid and a low pressure stream of the secondary fluid. The secondary fluid circuit also has a primary-secondary heat exchanger permitting heat exchange between the high pressure stream of the primary fluid and the low pressure stream of the secondary fluid.