Bronchoscopic Microwave Ablation Applicator with Liquid Cooling
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Solution Overview
Problem
Current microwave ablation devices face challenges in delivering sufficient energy to lung tumors due to energy attenuation in thin coaxial cables, leading to increased heating and complications such as pneumothorax, and are limited by size constraints of bronchoscopic working channels.
Innovation Solution
A flexible microwave ablation applicator with a thin and flexible coaxial cable, capable of navigating tight bends, and a coolant system to mitigate cable heating, along with a partially encapsulated antenna to minimize energy loss, allowing for precise delivery of microwaves through bronchoscopic/endoscopic approaches.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a thin and flexible coaxial cable is used to navigate tight bends in bronchoscopic working channels, then the ability to access peripheral lung tumors is improved, but energy attenuation increases leading to insufficient delivery of microwave energy to the target
Solution Approach 1:
A liquid barrier (dielectric medium) is introduced as an intermediary substance filling the space between the antenna and the cable insulation. This liquid barrier serves multiple functions: it prevents microwave energy from traveling backward along the cable (reducing energy loss), provides cooling to the antenna, and maintains the flexibility of the thin cable while enabling effective energy delivery to the target tissue
Solution Approach 2:
The patent changes the physical state and properties of the cable system by introducing a liquid dielectric medium that alters the electromagnetic field distribution. This parameter change allows the thin, flexible cable to maintain its mechanical advantages (flexibility, small diameter) while overcoming its electromagnetic disadvantage (energy attenuation) through the modified field environment created by the liquid barrier
2Power
If higher microwave power is delivered to compensate for cable attenuation, then sufficient energy reaches the target, but cable heating increases causing thermal damage and complications such as pneumothorax
Solution Approach 1:
The liquid barrier acts as a thermal intermediary that absorbs excess heat from the antenna and cable interface, preventing it from propagating along the cable and causing thermal damage. This mediator allows high power delivery to the target while protecting the cable and surrounding tissues from harmful heating effects
Solution Approach 2:
A fluid circulation system is implemented where liquid (saline or contrast agent) is pumped through the catheter, providing continuous cooling to the antenna and cable. This hydraulic approach actively removes heat generated during high-power microwave delivery, enabling sustained treatment without thermal complications
3Loss of energy
If a larger diameter cable is used to reduce energy attenuation, then energy delivery is improved, but the device cannot be delivered through narrow bronchoscopic working channels
Solution Approach 1:
The liquid barrier serves as an electromagnetic intermediary that compensates for the small cable diameter. By filling the space around the antenna, it creates a controlled electromagnetic environment that reduces energy loss along the cable, allowing thin cables to perform as if they were larger diameter cables without the mechanical disadvantages
4Power
If the antenna is fully exposed to deliver maximum energy, then ablation efficacy is improved, but energy loss along the cable increases
Solution Approach 1:
The liquid barrier is strategically positioned only in the region where it is most needed - between the antenna and the cable insulation. This localized application allows the antenna to remain exposed for effective energy delivery to tissue while the liquid barrier specifically addresses the energy loss problem in the cable region, optimizing both ablation efficacy and energy efficiency
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 enhances treatment efficacy by reducing energy loss, minimizing thermal damage, and improving safety, enabling more accurate and effective ablation of lung tumors with reduced risk of complications.
Implementation Method 1
Heat is produced when the rapidly oscillating radiated electric field induces rotation of polar molecules in tissue (such as water) which attempt to align with the orientation of the applied field
Implementation Method 2
The coolant flowing through the catheter may absorb some of the microwaves emitted from the antenna thereby cooling the cable
Implementation Method 3
Microwave ablation (MWA) is one of several energy modalities in clinical use for thermal treatment of cancer
Data Source
AI summary
A novel microwave ablation applicator includes a flexible tubular shaft and a partially encapsulated antenna. The applicator is adapted to be used with an endoscope in order to access remote targets deep within an organ of a patient. Microwave power is emitted from the antenna in a desired radiation pattern by circulating an attenuating liquid through the shaft and across a portion of the antenna. Microwave ablation systems and methods are described.