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 treatment times, hospitalization periods, and costs, due to high pressures and inefficient passive subcooling methods.
Innovation Solution
A closed or semi-closed cryogenic medical device that converts liquid nitrogen to supercritical nitrogen, which is subcooled and delivered through flexible cryoprobes with minimal friction, using a series of pressurized cylinders, baffled linear heat exchangers, and vacuum-insulated dewars to facilitate rapid cooling and efficient cryogen circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If liquid nitrogen is delivered through high pressure systems, then cryogen can be delivered to cryoprobes, but the system cannot operate or withstand pressures greater than 500 psi and delivery efficiency is limited
Solution Approach 1:
The patent changes the pressure parameter of the cryogen delivery system from conventional high pressure (limited to 500 psi) to ultra-high pressure (exceeding 500 psi, up to 3000 psi or more). This parameter change enables the system to overcome the 500 psi limitation and achieve rapid cryogen delivery through small-bore catheters, directly resolving the contradiction between delivery efficiency and pressure tolerance.
Solution Approach 2:
The system employs intermittent or periodic delivery of liquid nitrogen bursts rather than continuous flow. This periodic action allows the system to build up ultra-high pressure behind the liquid nitrogen slug, achieving rapid delivery through the catheter while managing the overall pressure cycling to prevent excessive sustained pressure on system components.
2Temperature
If passive subcooling methods are used, then cryogen can be cooled, but the process is time-consuming and inefficient
Solution Approach 1:
The patent replaces passive thermal conduction-based subcooling with an active mechanical pressurization system. By using a syringe mechanism to rapidly inject liquid nitrogen under ultra-high pressure, the system achieves rapid cooling and delivery without relying on time-consuming passive heat exchange through walls or coils.
Solution Approach 2:
The system performs preliminary pressurization of the liquid nitrogen in the delivery syringe before injection into the patient. This preliminary action of pressurizing the cryogen beforehand eliminates the need for time-consuming subcooling during the delivery process, as the pre-pressurized liquid nitrogen can be rapidly injected and will flash-expand to create the freezing effect.
3Length of moving object
If liquid nitrogen is delivered through small tubes, then minimally invasive treatment is achieved, but delivery speed is reduced due to friction and pressure limitations
Solution Approach 1:
The system uses periodic or intermittent injection of liquid nitrogen slugs through the small-bore catheter. Each slug is delivered as a discrete burst under ultra-high pressure, allowing rapid delivery through the narrow lumen without requiring continuous high-velocity flow that would be limited by friction in small tubes.
Solution Approach 2:
The patent changes the pressure parameter to ultra-high levels (exceeding 500 psi, up to 3000 psi or more) to overcome the frictional resistance in small-bore catheters. This parameter change enables sufficient delivery speed through narrow tubes by increasing the driving pressure gradient, while still maintaining the minimally invasive benefit of small catheter diameter.
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 solution enables rapid tissue freezing within 15 seconds to 5 minutes, reduces hospitalization time, minimizes postoperative morbidities, and lowers treatment costs by improving cryogen delivery and circulation efficiency, thus enhancing the treatment of various disease states.
Implementation Method 1
baffled linear heat exchanger to subcool the liquid cryogen
Implementation Method 2
subcool the liquid cryogen
Implementation Method 3
vacuum insulation layer
Implementation Method 4
heat is absorbed (nucleate boiling) along the inner surface of the tip
Implementation Method 5
micro bubbles of nitrogen gas condense back into a liquid
Implementation Method 6
heat transfer and subcooling of the cryogen
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.