Microwave Applicator Probe Cooling via Segmented Flow Channels
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Solution Overview
Problem
Existing microwave applicators for medical use face issues with probe heating due to power losses, microwave energy absorption, and back-conducted heat, leading to potential patient burns and the need for large cooling passages that increase the probe diameter, complicating the design.
Innovation Solution
A microwave applicator with an elongate shaft featuring an external tubular wall and internal flow dividing means that creates discrete cooling fluid passages, eliminating the need for complex cooling pipes and allowing for a thinner, more minimally invasive design, while incorporating a transmission line and optional thermocouple wires for temperature sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If cooling fluid passages are made large to achieve desired flow rates, then cooling effectiveness is improved, but the probe diameter increases
Solution Approach 1:
The internal space of the tubular wall is segmented into multiple discrete flow passages by the flow dividing means, allowing cooling fluid to flow through multiple parallel paths. This segmentation enables adequate cooling flow rates while maintaining a compact overall probe diameter, as the cooling function is distributed across multiple smaller passages rather than requiring a single large passage.
Solution Approach 2:
The flow dividing means and flow passages are nested within the existing tubular wall structure of the probe. The cooling passages are formed internally within the wall thickness, utilizing the existing structural envelope without requiring additional external space. This nesting approach allows effective cooling while maintaining a thin probe diameter suitable for minimally invasive procedures.
2Temperature
If complicated pipes and formers are used to create flow and return passages, then cooling function is improved, but device complexity increases
Solution Approach 1:
The flow dividing means serves multiple functions simultaneously: it divides the cooling fluid into separate flow and return passages, provides structural support within the tubular wall, and enables the cooling function without requiring separate pipes or formers. This merging of functions reduces the overall number of components and simplifies the device structure while maintaining effective cooling capability.
Solution Approach 2:
The tubular wall structure is designed to serve dual purposes: providing mechanical support for the probe and housing the cooling fluid passages. The flow dividing means is integrated into this universal structure, eliminating the need for dedicated cooling components. This multi-functional design reduces device complexity while achieving the required cooling function.
3Ease of operation
If probe diameter is reduced for minimally invasive use, then ease of insertion is improved, but space for cooling passages is reduced
Solution Approach 1:
The cooling passages are formed by utilizing the wall thickness dimension of the tubular structure, rather than requiring additional radial space. The flow dividing means creates passages that extend through the wall thickness, effectively using the existing dimensional envelope of the thin-walled probe. This approach enables adequate cooling passage volume while maintaining a thin overall probe diameter for minimally invasive insertion.
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 solution effectively cools the probe, minimizes the risk of patient burns, and reduces the probe's diameter, enhancing its non-invasive capabilities and ease of construction while maintaining effective temperature monitoring.
Implementation Method 1
cooling fluid can be passed along the first passage to cool the probe, the cooling fluid then returning along the second passage
Implementation Method 2
A thin elongate microwave transmission line extends inside the probe from the handle to a radiating tip disposed at or adjacent the distal end of the probe. In use, the microwave field radiated from the tip heats and ablates the surrounding tissue
Implementation Method 3
said flow dividing member may comprise a tube or a cable carrying at least one wire of a thermocouple
Data Source
AI summary
A microwave applicator having a probe which comprises an elongate shaft (14), the shaft having an external tubular wall (18), a radiating portion (15) disposed at the distal end of the shaft (14), a transmission line (17) extending to the radiating portion internally of the tubular external wall (18), and an elongate flow dividing member (19) which co-extends with the transmission line (17) longitudinally of the shaft (14), the side wall of the transmission line (17) and the side wall of the flow dividing member (19) contacting each other and contacting the internal surface of the external tubular wall (18) at two-spatially separated discrete positions, thereby defining a pair of flow channels (20, 21) inside the shaft (14). In use, cooling fluid can pass down one channel (20) and return via the other channel (21). The structure of the probe is uncomplicated and the probe is straightforward to assemble.