Analysis of microwave ablation antenna optimization techniques

Abstract

Microwave ablation is a minimally invasive treatment modality for malignant and benign tumors in several organs. While many microwave ablation antennas have been described in the literature, most have been designed assuming normal ambient tissue and have not accounted for tissue property changes that occur during intense heating. We analyzed three optimization approaches for canonical monopole and dual‐slot antennas: minimal reflection, spherical specific absorption rate (SAR) pattern, and spherical ablation zone. Simulated ablations with each optimal design were also validated in ex vivo liver tissue. Optimized designs for minimal reflection matched previously published results, while designs optimized for spherical SAR and spherical ablation yielded novel geometries. Surprisingly, optimization for spherical SAR rendered the most spherical ablation zones in ex vivo tissue. Optimizations for minimal reflection and spherical ablation zone did not achieve the most spherical ablation zones in experiments. These results point to the need for greater accuracy in dielectric and thermal tissue models to improve simulation‐aided design, and to the potential for continued refinement in microwave ablation antenna design.

Evaluation of tissue deformation during radiofrequency and microwave ablation procedures: Influence of output energy delivery

“…Previous studies have suggested that changes in dielectric properties can produce elongation of the electric field along the antenna, leading to elongation of the ablation zone itself . Other studies have attempted to create more spherical ablations through antenna design optimization . The present study demonstrated that for all powers and energy types, the primary direction of tissue contraction was orthogonal to this antenna design, with mean principal angles of −8.1º to 5.4º, dependent on the ablation powers and energy types (Fig.…”

“…[34][35][36][37][38] Other studies have attempted to create more spherical ablations through antenna design optimization. [39][40][41] The present study demonstrated that for all powers and energy types, the primary direction of tissue contraction was orthogonal to this antenna design, with mean principal angles of À8.1°to 5.4°, dependent on the ablation powers and energy types (Fig. 11).…”

Sensitivity analysis of critical parameters affecting the efficacy of microwave ablation using Taguchi method

“…nos. 12,15,18,20,21,23, and 24. The analysis of variance (ANOVA) has also been performed to analyze the relative influence of selected parameters on the ablation volume attained for different experiments of Taguchi's L27 orthogonal array during FIGURE 4 Shapes of ablation volumes (corresponding to isotherm of 60 C) attained after 5 min of MWA application for different experiments of Taguchi's L27 orthogonal array MWA.…”

“…Although, in vivo animal studies and clinical trials are useful for evaluating the efficacy of any device, but numerical modeling could play a crucial role, specifically, during the design of devices for MWA; serving as a quick, convenient and inexpensive evaluation to isolate and optimize the device during prototyping . Several computational studies are available in the literature on mathematical modeling of MWA, specifically in one compartment model of the hepatic tissue . Most of these reported studies are based on axisymmetric model, with few incorporating temperature dependent parameters.…”

“…17 Several computational studies are available in the literature on mathematical modeling of MWA, specifically in one compartment model of the hepatic tissue. [18][19][20][21][22][23][24][25][26] Most of these reported studies are based on axisymmetric model, with few incorporating temperature dependent parameters. Importantly, the outcome of all these studies is quantified by the qualitative assessment of the ablation volume at the end of MWA procedure.…”