Supercritical Nitrogen Cryogenic System for Rapid Tissue Freezing
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Solution Overview
Problem
Current cryotherapy systems face limitations in efficiently delivering liquid cryogen to cryoprobes, leading to slow tissue freezing and increased hospitalization times, postoperative morbidities, and treatment costs, due to reliance on moderate to high pressures and inefficient passive subcooling methods.
Innovation Solution
A cryogenic medical device that converts liquid nitrogen to supercritical nitrogen, which is subcooled and delivered through flexible cryoprobes with minimal friction, using a closed or semi-closed system with pressurized cylinders, a baffled linear heat exchanger, and a series of valves for controlled flow and cooling, allowing for rapid tissue freezing and reutilization of cryogen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If liquid nitrogen is delivered through high pressure systems, then the cryogen can be delivered to the probe, but the system cannot withstand pressures greater than 34.5 Bar and operates inefficiently
Solution Approach 1:
The patent changes the phase parameter of nitrogen from liquid to supercritical state, allowing the system to operate at higher pressures (above 34.5 Bar) while maintaining efficient cryogen delivery to the probe tip
Solution Approach 2:
The system utilizes phase transition of nitrogen between liquid, supercritical, and gaseous states to achieve efficient cryogen delivery. Liquid nitrogen is converted to supercritical nitrogen for high-pressure delivery, then expands to gas at the probe tip to create the freezing effect
2Temperature
If passive heat exchangers with coils in cryogen bath are used, then cooling can be achieved, but the subcooling process is time-consuming and inefficient
Solution Approach 1:
The patent replaces passive thermal conduction-based heat exchangers with an active mechanical pressurization system that converts liquid nitrogen to supercritical nitrogen, enabling rapid and efficient cryogen delivery without time-consuming passive subcooling
Solution Approach 2:
The system performs preliminary pressurization and phase conversion of nitrogen to supercritical state before delivery, so that when the cryogen reaches the probe tip, it is already prepared for immediate expansion and tissue freezing, eliminating delays
3Volume of moving object
If liquid nitrogen is delivered through small tubes, then the delivery system becomes more compact, but the flow rate decreases and freezing time increases
Solution Approach 1:
The patent changes the physical state of nitrogen to supercritical phase, which has unique properties allowing it to flow through small tubes with minimal friction while maintaining high density and cooling capacity, thus achieving both compact delivery and rapid freezing
Solution Approach 2:
The system uses pressurized supercritical nitrogen flow dynamics to deliver cryogen through small-bore catheters and probes, utilizing the compressible fluid properties to maintain adequate flow rates and cooling power despite restricted geometry
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 rapid tissue freezing within 15 seconds to 5 minutes, reduces hospitalization time, decreases postoperative morbidities, and lowers treatment costs by improving cryogen delivery efficiency and reutilization, enhancing its applicability for multiple disease states.
Implementation Method 1
By converting liquid nitrogen to supercritical nitrogen (SCN) in a cylinder/cartridge cooled by atmospheric liquid nitrogen (-196°C)
Implementation Method 2
heat is absorbed (nucleate boiling) along the inner surface of the tip
Implementation Method 3
activate these devices circulate a cryogen (such as liquid nitrogen) to a probe to create a heat sink, thus resulting in tissue freezing
Implementation Method 4
The device is a closed or semi-closed system in which the liquid cryogen is contained in both the supply and return stages
Data Source
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AI summary
A cryogenic medical device for delivery of subcooled liquid cryogen to various configurations of cryoprobes is designed for the treatment of damaged, diseased, cancerous or other unwanted tissues. The device is a closed or semi-closed system in which the liquid cryogen is contained in both the supply and return stages. The device is capable of generating cryogen to a supercritical state and may be utilized in any rapid cooling systems. As designed, the device comprises a number of parts including a vacuum insulated outer dewar, submersible cryogen pump, baffled linear heat exchanger, multiple pressurization cartridges, a return chamber, and a series of valves to control the flow of the liquid cryogen interconnected with cryotreatment devices including cryoprobes and catheters. The cryogenic medical device promotes subcooling to the tips of various external cryogenic instrument configurations