Antenna Designs for Microwave Tissue Ablation

Abstract

Microwave (MW) ablation has emerged as a minimally invasive therapeutic modality and is in clinical use for treatment of unresectable tumors and cardiac arrhythmias, neuromodulation, endometrial ablation, and other applications. Components of image-guided MW ablation systems include high-power MW sources, ablation applicators that deliver power from the generator to the target tissue, cooling systems, energy-delivery control algorithms, and imaging guidance systems tailored to specific clinical indications. The applicator incorporates a MW antenna that radiates MW power into the surrounding tissue. A variety of antenna designs have been developed for MW ablation with the objective of efficiently transferring MW power to tissue, with a radiation pattern well matched to the size and shape of the targeted tissue. Here, we survey advances in percutaneous, endocavitary, and endoscopic antenna designs as an integral element of MW ablation applicators for a diverse set of clinical applications.

Broadband lung dielectric properties over the ablative temperature range: Experimental measurements and parametric models

“…The transient temperature profiles at the measurement site were also independently measured and stored at a sampling rate of 1 Hz. Initially, the hot plate temperature was set to 130–152 C, in order to achieve a rate of heating similar to that achieved during MWA with cooled applicators at distances of 10 mm from the applicator; it is noted that rates of heating adjacent to the applicator may vary across systems as a function of operating frequency and antenna design . When the sample temperature reached ∼94 C, the hot plate surface temperature was set to 200 C (maximum setting) in order to overcome the latent heat of water vaporization, and raise the tissue temperatures above 100 C.…”

“…Initially, the hot plate temperature was set to 130-152 C, in order to achieve a rate of heating similar to that achieved during MWA with cooled applicators at distances of 10 mm from the applicator 5 ; it is noted that rates of heating adjacent to the applicator may vary across systems as a function of operating frequency 33 and antenna design. 34 When the sample temperature reached $ 94 C, the hot plate surface temperature was set to 200 C (maximum setting) in order to overcome the latent heat of water vaporization, and raise the tissue temperatures above 100 C. The open end of the coaxial probe and fiber optic temperature sensors was thoroughly cleansed with alcohol before use on another experimental tissue sample.…”

Helical Slot Antenna for the Microwave Ablation

“…e operating range can be controlled by the input power delivered to the antenna. Additionally, when the double-slot antenna is applied, the MW radiation range is concentrated compared with the single-slot applicator, but when the input power increased, the range to be transmitted becomes higher again [7][8][9][10][11][12][13][14][15][16][17].…”

Microwave Ablation: A Potential Minimally Invasive Solution for Gastric Motility Disorders

“…For this pilot study, we investigated a coaxial monopole antenna [9], centered within a water-filled balloon. The antenna is formed by exposing a length of the inner conductor at the distal end of a flexible coaxial cable.…”

“…Like cardiac ablation, the goal of the ablation is to inhibit electrical conduction in a localized region to block dysrhythmias. For most microwave ablation devices in clinical use (predominantly, needle-based tumor ablation [9,10]), the ablation zone extends up to the device surface. The device in this study will use water to cool the surface at the stomach wall, therefore sparing the mucosa.…”