Low-Profile Microwave Ablation Probe for Spherical Heating Control

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Solution Overview

Problem

Existing microwave ablation probes often produce elongated or teardrop-shaped heating zones due to backward current along the probe, causing unintended tissue damage and requiring a larger profile, while maintaining a small size and predictable heating zones is desirable.

Innovation Solution

Incorporating a cooling system with a choke structure and varying diameter cooling tube to limit backward current and achieve a more spherical heating zone, using materials like stainless steel and polymers to maintain a low profile and effective cooling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a microwave ablation probe is designed with a larger profile to accommodate cooling systems and choke structures, then effective cooling and current control are improved, but the probe size increases causing damage to surrounding tissues

Engineering Contradiction:

Improvecooling effectivenessVSAvoiddamage to surrounding tissues

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The cooling tube is positioned inside the shell and radially outward of the cable, creating a nested concentric structure. The choke is electrically coupled to the outer conductor of the cable and positioned within the probe structure. This nesting allows multiple functional components (cooling system, choke, antenna) to be integrated within a compact probe diameter, effectively cooling the probe while controlling backward current without increasing the overall probe size that would damage surrounding tissues.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The cooling tube has varying diameter along its length, with a first portion having a first outer diameter and a second portion having a second outer diameter greater than the first. This dimensional variation along the axial dimension allows optimized cooling flow distribution and choke structure accommodation without increasing the radial probe profile, thus maintaining small probe size while improving cooling effectiveness.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of manufacture

If the cooling tube has uniform diameter, then manufacturing is simplified, but effective cooling distribution and choke accommodation are compromised

Engineering Contradiction:

Improvecooling tube fabricationVSAvoidcooling effectiveness

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The cooling tube is designed with different diameters at different axial positions. The first portion has a first outer diameter and the second portion has a second outer diameter greater than the first. This local variation in diameter allows the cooling tube to effectively accommodate the choke structure in the second portion while maintaining appropriate cooling flow characteristics in the first portion, optimizing cooling effectiveness without requiring uniform diameter throughout.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If the probe maintains a small diameter to prevent tissue damage, then safety is improved, but the heating zone becomes unpredictable and elongated

Engineering Contradiction:

Improvedamage to surrounding tissuesVSAvoidheating zone predictability

Core Design Contradiction:

Object-affected harmful factorsVSManufacturing precision

Solution Approach 1:

The choke structure is electrically coupled to the outer conductor of the cable and is positioned within the probe to limit backward current flow. By extracting and controlling the backward current path through the choke, the heating zone shape is corrected from elongated/teardrop to spherical, improving predictability without requiring an increase in probe diameter that would compromise safety.

Inventive Principle:

Principle #2Taking out (Extraction)

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

Implementation Method 1

a cooling tube positioned between the cable and the shell defining a cooling path for delivery of a cooling fluid

Methodology Applied

Scientific EffectFluid cooling: Convection

Implementation Method 2

an antenna configured to deliver Radio Frequency (RF) energy... The heating zone can then be reliably delivered to the target tissue

Methodology Applied

Scientific EffectRadio Frequency heating: Dielectric Heating

Implementation Method 3

Incorporating a cooling system with a choke structure and varying diameter cooling tube to limit backward current

Methodology Applied

Scientific EffectElectromagnetic current control: Electrical Resistance

Data Source

PatentUS12588948B2Fluid-cooled low-profile microwave ablation probe with spherical ablation zone

Publication Date: 2026.03.31 VARIAN MEDICAL SYSTEMS INC

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.