Feasibility Assessment of Microwave Ablation for Treating Esophageal Varices

Abstract

Esophageal varices are a significant complication of portal hypertension. Endoscopic variceal ligation (EVL) is one of the clinical standards for treating these varices and preventing their hemorrhage. Limitations of EVL include the risk of stricture formation and postband ulcer bleeding due to the damage caused to the esophageal mucosa, as well as the need for multiple endoscopic treatment sessions to eradicate the varices. The goal of this study is to develop a device and evaluate the technical feasibility of microwave ablation to seal esophageal varices, while preventing thermal damage to the surface mucosal tissue. A microwave applicator with a directional radiation pattern was developed for endoscopic ablation of esophageal varices. Electromagnetic and bioheat transfer computational models were employed to optimize the design of the microwave applicator and evaluate energy delivery strategies for this application. Experiments in ex vivo and in vivo tissue were employed to verify simulation results. Simulations predicted enhanced heating performance of the antenna using an angled monopole radiating element. Further, simulations indicate that while the endoscopic cap attenuated electric fields in tissue, it also enhanced surface cooling of tissue, increasing the likelihood of preserving mucosal tissue. Experiments in ex vivo tissue indicated the feasibility of sealing veins with 77 W microwave power delivered for 30 s. In vivo experiments demonstrated the ability to seal veins, while preserving surface tissue. This study demonstrated the technical feasibility of microwave thermal ablation for treating esophageal varices using a 2.45 GHz water-cooled directional microwave applicator.

Next-Generation Healthcare: Enabling Technologies for Emerging Bioelectromagnetics Applications

“…However, a directional heating pattern may be required for some specific scenarios where, for example, a target tumor is close to the bowel which should not be ablated. Different types of MWA antennas with directional heating patterns have been developed and reported [259]- [261].…”

Antenna Designs for Microwave Tissue Ablation

“…Sebek et al 9 integrated a modified version of the directional device of McWilliams et al 21 shown in Fig. 13a into a standard endoscopic cap for the application of treating esophageal varices (see Fig.…”

“…Examples of technologies for delivering ablative energy via (A) percutaneous, (B) intracavitary (adapted from Burtnyk et al 8 ), (C) endovascular (adapted from Fernández-Ruiz 10 ), (D) endoscopic approaches (adapted from Sebek et al 9 ).…”