Pulsed Cryogen Delivery for Flexible Cryoprobes Under High Pressure
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current cryotherapy systems face limitations in efficiently delivering liquid cryogen to cryoprobes, particularly in terms of pressure capacity and heat exchange efficiency, which hampers rapid tissue freezing and increases treatment time and costs.
Innovation Solution
A cryogenic medical device that converts liquid nitrogen to supercritical nitrogen, allowing for subcooling and efficient delivery through flexible cryoprobes with minimal friction, utilizing a closed or semi-closed system with a vacuum insulated dewar, submersible pump, and a baffled linear heat exchanger for enhanced heat transfer and return of cryogen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If liquid nitrogen is delivered through moderate to high pressure on the entire system, then cryogen can be delivered to the probe, but the system cannot withstand pressures greater than 500 psi and cannot achieve rapid tissue freezing
Solution Approach 1:
The system is divided into two distinct pressure zones: a low-pressure delivery system (0-500 psi) for safe cryogen transport through flexible probes, and a high-pressure generation system (up to 3000 psi) localized at the probe tip through a micro-balloon expander. This segmentation allows each component to operate within its optimal pressure range, achieving both safe delivery and rapid freezing capability.
Solution Approach 2:
The invention changes the pressure parameter dynamically through the micro-balloon expander mechanism. Liquid cryogen is delivered at low pressure, then rapidly expanded to high pressure at the probe tip through the expander, creating a pressure spike that enables instantaneous tissue freezing without requiring the entire delivery system to withstand high pressures.
2Temperature
If heat exchangers are used with coils placed into a bath of cryogen, then passive subcooling of the cryogen can be achieved, but the process is time consuming and inefficient
Solution Approach 1:
The invention replaces the passive thermal conduction-based heat exchanger system with an active mechanical expansion system. Instead of relying on slow heat transfer from cryogen baths through coils, the system uses the micro-balloon expander to mechanically compress and rapidly expand the cryogen, achieving subcooling and delivery in seconds rather than minutes or hours.
Solution Approach 2:
The system employs periodic pulsing of the micro-balloon expander to deliver cryogen in controlled bursts. This periodic action allows for efficient heat exchange during each pulse cycle, where the rapid expansion and compression cycles enhance heat transfer efficiency compared to continuous passive cooling.
3Productivity
If liquid cryogen is delivered through small tubes to enable rapid delivery, then treatment efficiency can be improved, but friction losses increase and delivery becomes difficult
Solution Approach 1:
The invention uses pneumatic principles through the micro-balloon expander to overcome friction losses in small tubes. The expandable balloon mechanism creates positive displacement pumping action that pushes liquid cryogen through narrow bore flexible tubes, maintaining adequate flow velocity and pressure despite the small tube dimensions and associated friction losses.
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
Enables rapid tissue freezing with reduced treatment times and costs, facilitating quicker recovery and increased utilization for multiple disease states by improving cryogen circulation and delivery efficiency.
Implementation Method 1
The device includes a vacuum insulated dewar, submersible pump, and a baffled linear heat exchanger for enhanced heat transfer
Implementation Method 2
a baffled linear heat exchanger for enhanced heat transfer and return of cryogen
Implementation Method 3
the SCN can be injected into one or more flexible cryoprobes, the SCN flows with minimal friction to the tip of the probe
Implementation Method 4
In the tip, SCN pressure drops due to an increased volume and outflow restriction, heat is absorbed (nucleate boiling) along the inner surface of the tip, micro bubbles of nitrogen gas condense back into a liquid, and the warmed SCN reverts to pressurized liquid nitrogen
Data Source
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. The cryogenic medical device promotes the subcooling to any external cryogenic instrument.