Exploiting Tissue Dielectric Properties to Shape Microwave Thermal Ablation Zones

Area of Science:

• Biomedical Engineering
• Electromagnetics
• Medical Devices

Background:

• Dielectric properties of tissues are crucial for effective microwave thermal ablation (MTA).
• Clinical application of MTA is often complicated by the presence of intervening fat layers near the target tissue.
• Understanding the dielectric contrast between fat and target tissue is essential for optimizing MTA procedures.

Purpose of the Study:

• To investigate how the dielectric contrast between fat and target tissue influences the shape and size of the ablation zone during MTA.
• To evaluate the impact of varying fat layer thickness and antenna alignment on MTA performance.
• To compare MTA outcomes in interface scenarios with a homogeneous reference scenario.

Main Methods:

• Numerical simulations of a 2.45 GHz monopole antenna placed parallel to a fat-tissue interface at 30 and 60 W for 60 s.
• Modeling different interface scenarios, including varying fat layer widths and antenna shifts.
• Experimental validation using ex vivo porcine tissue (N=10).

Main Results:

• Asymmetric heating patterns were observed in the fat-tissue interface scenarios.
• The ablation zone in the target tissue was 2-10 times larger than in the adipose tissue.
• Ablation zones were up to four times larger than in the homogeneous reference scenario.
• Adipose tissue reflected electromagnetic energy into the target tissue, enhancing heating in that direction.

Conclusions:

• The dielectric contrast between fat and target tissue significantly alters MTA outcomes.
• Interfacial fat layers can lead to larger and asymmetric ablation zones, primarily due to electromagnetic energy reflection.
• These findings are critical for improving pre-procedural planning and efficacy of MTA in clinical scenarios involving fat interfaces.