Monitoring Thermal Ablation via Microwave Tomography: An Ex Vivo Experimental Assessment.

Rosa Scapaticci,Marta Cavagnaro,Rosanna Pinto,Lorenzo Crocco,Vanni Lopresto

doi:10.3390/diagnostics8040081

Abstract

Thermal ablation treatments are gaining a lot of attention in the clinics thanks to their reduced invasiveness and their capability of treating non-surgical patients. The effectiveness of these treatments and their impact in the hospital’s routine would significantly increase if paired with a monitoring technique able to control the evolution of the treated area in real-time. This is particularly relevant in microwave thermal ablation, wherein the capability of treating larger tumors in a shorter time needs proper monitoring. Current diagnostic imaging techniques do not provide effective solutions to this issue for a number of reasons, including economical sustainability and safety. Hence, the development of alternative modalities is of interest. Microwave tomography, which aims at imaging the electromagnetic properties of a target under test, has been recently proposed for this scope, given the significant temperature-dependent changes of the dielectric properties of human tissues induced by thermal ablation. In this paper, the outcomes of the first ex vivo experimental study, performed to assess the expected potentialities of microwave tomography, are presented. The paper describes the validation study dealing with the imaging of the changes occurring in thermal ablation treatments. The experimental test was carried out on two ex vivo bovine liver samples and the reported results show the capability of microwave tomography of imaging the transition between ablated and untreated tissue. Moreover, the discussion section provides some guidelines to follow in order to improve the achievable performances.

Highlights

Thermal ablation is a therapeutic procedure used to destroy unhealthy tissue by way of a very high and localized temperature increase
The setup consisted of two main parts: the ‘therapeutic’ one, on the right side of the picture, which was in charge of performing microwave thermal ablation (MTA), and the ‘monitoring’ part, on the left side, which gathered the data required for the Microwave tomography (MWT) processing
The study aimed at assessing the feasibility of MWT as a real-time monitoring tool for thermal ablation treatments

Summary

Introduction

Thermal ablation is a therapeutic procedure used to destroy unhealthy tissue by way of a very high and localized temperature increase. The target temperature is close to 60 ◦ C in the zone of ablation, which for tumor treatment should include the pathologic lesion plus a 5−10 mm safety margin of healthy tissue [1,2]. At this temperature, an almost instantaneous cell death by way of coagulative necrosis is achieved [1]. Microwave thermal ablation (MTA), in which the energy source is an electromagnetic field in the Industrial, Scientific and Medical (ISM) frequency band. Diagnostics 2018, 8, 81; doi:10.3390/diagnostics8040081 www.mdpi.com/journal/diagnostics (typically at 915 MHz or 2.45 GHz), is gaining an increasing attention in the clinical practice [4,5], owing to its capability of treating larger tumors in a shorter time with respect to other ablation modalities [2].

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Results

Discussion

Conclusion