Cryoprobe Tip Temperature Estimation for Safe Iceball Release
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Solution Overview
Problem
The challenge of safely extracting a cryoprobe from tissue after forming an iceball without causing pain or tissue damage due to the iceball adhering to the probe's external surface.
Innovation Solution
Incorporating a heating element and temperature sensor at the probe's distal end, with a controller that delivers gas pulses to regulate temperature, using time differences between temperature readings to determine when the probe can be safely extracted.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the cryoprobe is extracted while the iceball is still formed, then the treatment is completed quickly, but the iceball adheres to the probe's external surface causing pain and tissue damage
Solution Approach 1:
The system performs preliminary heating of the probe's external surface before extraction to prevent iceball adhesion. The controller activates the heating element in advance, monitors the temperature via the sensor, and ensures the temperature reaches a safe level (indicated by the time difference threshold) before allowing probe extraction, thus preventing tissue damage and pain.
Solution Approach 2:
The system uses a temperature sensor positioned near the external surface to continuously monitor the probe temperature and provide feedback to the controller. The controller compares the monitored temperature (via time difference calculation) with a predetermined threshold and adjusts the heating element activation accordingly, ensuring the probe is safe for extraction only when the iceball will not adhere.
2Object-affected harmful factors
If the heater is activated continuously to prevent iceball adhesion, then tissue damage is avoided, but energy consumption increases
Solution Approach 1:
Instead of continuous heating, the system uses periodic or pulsed heating activation. The controller monitors the temperature sensor readings and activates the heating element only when the temperature drops below the threshold required to prevent iceball adhesion. This periodic activation maintains tissue safety while significantly reducing overall energy consumption compared to continuous heating.
Solution Approach 2:
The system allows the probe's thermal properties and the iceball's natural melting process to contribute to temperature regulation. The heating element provides supplemental heat only when needed, rather than continuously maintaining temperature, thereby reducing energy consumption while still preventing harmful adhesion.
3Measurement precision
If a temperature sensor is positioned close to the external surface to accurately measure surface temperature, then extraction safety is improved, but the sensor may be affected by the heater's direct thermal influence
Solution Approach 1:
The temperature sensor is positioned in a specific location that balances measurement accuracy and reliability - close enough to the external surface to accurately reflect surface temperature for extraction safety, but positioned such that it is not in direct contact with or immediately adjacent to the heating element. This localized positioning ensures the sensor measures the actual surface temperature that will contact the iceball, while avoiding direct thermal interference from the heater.
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 safe and pain-free removal of the cryoprobe by iteratively pulsing gas to estimate the external surface temperature, allowing extraction when the time difference indicates a suitable temperature for removal, regardless of iceball size.
Implementation Method 1
a heater, located in the probe distal end
Implementation Method 2
delivering a pulse of gas through the gas inlet so as to cool the probe distal end
Implementation Method 3
the temperature sensor consists of a thermocouple junction located between the heater and an internal surface of the probe distal end
Implementation Method 4
Cryoablation is a process that uses extreme cold to destroy tissue
Data Source
AI summary
Apparatus, consisting of a probe with a probe distal end having an external surface that contacts tissue when the distal end is inserted into a patient. A heater and a temperature sensor are in the distal end, and a gas inlet is coupled to the distal end to provide gas. While the heater is activated, a controller registers a first time when a temperature measured by the sensor equals or exceeds a preset temperature, and, in response to the temperature equaling or exceeding the preset temperature, delivers a gas pulse through the gas inlet so as to cool the probe distal end. The controller then registers a second time when the temperature measured by the sensor equals or exceeds the preset temperature, and, in response to a time difference between the second and first times, estimates a temperature of the external surface of the probe distal end.