Short pulsed microwave ablation: computer modeling and ex vivo experiments

Aleksandar Radosevic,Diego Prieto,Fernando Burdío,Enrique Berjano,Punit Prakash,Macarena Trujillo

doi:10.1080/02656736.2021.1894358

Abstract

Purpose To study the differences between continuous and short-pulse mode microwave ablation (MWA). Methods We built a computational model for MWA including a 200 mm long and 14 G antenna from Amica-Gen and solved an electromagnetic-thermal coupled problem using COMSOL Multiphysics. We compared the coagulation zone (CZ) sizes created with pulsed and continuous modes under ex vivo and in vivo conditions. The model was used to compare long vs. short pulses, and 1000 W high-powered short pulses. Ex vivo experiments were conducted to validate the model. Results The computational models predicted the axial diameter of the CZ with an error of 2–3% and overestimated the transverse diameter by 9–11%. For short pulses, the ex vivo computer modeling results showed a trend toward larger CZ when duty cycles decreases. In general, short pulsed mode yielded higher CZ diameters and volumes than continuous mode, but the differences were not significant (<5%), as in terms of CZ sphericity. The same trends were observed in the simulations mimicking in vivo conditions. Both CZ diameter and sphericity were similar with short and long pulses. Short 1000 W pulses produced smaller sphericity and similar CZ sizes under in vivo and ex vivo conditions. Conclusions The characteristics of the CZ created by continuous and pulsed MWA show no significant differences from ex vivo experiments and computer simulations. The proposed idea of enlarging coagulation zones and improving their sphericity in pulsed mode was not evident in this study.

Highlights

Microwave ablation (MWA) is a minimally invasive technique which delivers microwave (MW) power through an antenna to selectively heat tumors, causing their destruction by thermal coagulative necrosis [1]
Some of these studies have focused on characterizing the temperature dependence of thermophysical and dielectric properties [21,22,23,24,25,26], optimizing MWA applicator designs [27,28,29,30,31,32], and exploring how to model some important phenomena involved in MWA such as tissue shrinkage or vaporization [23,33,34,35]
Other computer modeling studies focused on other specific questions related to hepatic MWA such as the impact of working frequency (915 MHz vs. 2.45 GHz) [15], effect of tumor size on the shape of the coagulation zone created by MWA [36], effect of applicator placement relative to the tumor location [26], influence of different characteristics of tumor and healthy tissue [26], and the effect of blood perfusion [26,37]

Summary

Introduction

Microwave ablation (MWA) is a minimally invasive technique which delivers microwave (MW) power through an antenna to selectively heat tumors, causing their destruction by thermal coagulative necrosis [1]. Other computer modeling studies focused on other specific questions related to hepatic MWA such as the impact of working frequency (915 MHz vs 2.45 GHz) [15], effect of tumor size on the shape of the coagulation zone created by MWA [36], effect of applicator placement relative to the tumor location [26], influence of different characteristics of tumor and healthy tissue [26], and the effect of blood perfusion [26,37]

Methods

Results

Discussion

Conclusion