Fluid-Cooled Microwave Ablation Probe for Spherical Heating Zones

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Solution Overview

Problem

Existing microwave ablation probes often produce elongated or teardrop-shaped heating zones, causing unintended tissue damage and requiring larger profiles, while maintaining a small size and producing predictable spherical heating zones is desirable.

Innovation Solution

The design incorporates a cooling tube with varying diameters and a choke to limit backward current, combined with a low-profile shell and antenna configuration, ensuring a spherical heating zone and minimizing tissue damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a conventional microwave ablation probe design is used, then the probe can deliver RF energy to heat target tissue, but the heating zone becomes elongated or teardrop-shaped causing unintended tissue damage

Engineering Contradiction:
Improveheating zone shape controlVSAvoidunintended tissue damage
Core Design Contradiction:
Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The cooling tube is designed with varying diameter along its length, creating different cooling effects at different locations. The larger diameter section is positioned at the proximal end to provide enhanced cooling where needed, while the smaller diameter section allows adequate cooling at the distal end. This non-uniform cooling distribution transforms the heating pattern from elongated/teardrop-shaped to a more spherical ablation zone, preventing unintended tissue damage.

Inventive Principle:
Principle #3Local quality

2Volume of moving object

If the probe size is reduced to minimize damage to surrounding tissues, then the profile becomes smaller, but it becomes difficult to maintain a known and repeatable heating zone

Engineering Contradiction:
Improveprobe sizeVSAvoidheating zone repeatability
Core Design Contradiction:
Volume of moving objectVSReliability

Solution Approach 1:

The cooling tube diameter is changed along its length, with the proximal portion having a larger diameter and the distal portion having a smaller diameter. This parameter variation in the cooling system allows the probe to maintain a consistent, repeatable spherical heating zone pattern even while keeping the overall probe profile small. The differential cooling compensates for heat distribution variations, ensuring reliable and predictable ablation zones.

Inventive Principle:
Principle #35Parameter changes

3Device complexity

If a uniform diameter cooling tube is used, then the structure is simpler, but the cooling effectiveness varies along the length causing non-spherical heating zones

Engineering Contradiction:
Improvecooling tube structureVSAvoidheating zone geometry
Core Design Contradiction:
Device complexityVSShape

Solution Approach 1:

The cooling tube is designed with varying diameter along its length, creating different cooling effects at different locations. The larger diameter section is positioned at the proximal end to provide enhanced cooling where needed, while the smaller diameter section allows adequate cooling at the distal end. This non-uniform cooling distribution transforms the heating pattern from elongated/teardrop-shaped to a more spherical ablation zone, preventing unintended tissue damage.

Inventive Principle:
Principle #3Local quality

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 achieves repeatable, spherical heating zones with reduced tissue damage and a smaller probe diameter, enhancing treatment efficacy and safety.

Implementation Method 1

A microwave ablation antenna can be included in the probe and be used to deliver Radio Frequency (RF) energy such as microwave energy to a target tissue to heat the target tissue and destroy the target tissue

Methodology Applied
Scientific EffectRadio Frequency (RF) energy delivery: Electromagnetic Induction

Implementation Method 2

thermal ablation can be used to destroy undesirable tissue such as malignant cells in a body

Methodology Applied
Scientific EffectThermal ablation: Heating

Implementation Method 3

a cooling tube positioned inside the shell and positioned radially outward of the cable

Methodology Applied
Scientific EffectFluid cooling: Convection

Data Source

PatentEP4295799B1Fluid-cooled low-profile microwave ablation probe with spherical ablation zone
Publication Date: 2026.01.28 VARIAN MEDICAL SYSTEMS INC
  • EP4295799B1 patent drawingFigure 1~2
  • EP4295799B1 patent drawingFigure 3~5
  • EP4295799B1 patent drawingFigure 6~8

AI summary

A microwave ablation probe includes a cable extending in an axial direction and also includes an antenna configured to deliver Radio Frequency (RF) energy. The probe includes a shell positioned radially outward of the cable and a choke electrically coupled to an outer conductor of the cable. The probe also includes a cooling tube positioned inside the shell and positioned radially outward of the cable. The cooling tube including a first portion with a first outer diameter and a second portion with a second outer diameter. The second portion located radially outward of the choke and the second outer diameter being greater than the first outer diameter.