Characterization of the physical and structural changes undergone by a biological tissue during microwave thermal ablation procedures

The aim of the present doctoral project was to investigate the physical and structural changes occurring in biological tissue treated with microwave thermal ablation procedures, focusing the study on the evaluation and characterization of the shrinkage of the tissue, in correlation with the influence of the thermal changes. When the project started in 2013, few studies were conducted to comprehend the shrinking phenomenon (Diaz et al., 2008, Brace et al., 2009, Ganguli et al., 2008, Planché et al., 2013, Brace et al., 2010]. Nevertheless, the subject was of high interest for physicians and scientists involved in this field. The results reported from preliminary studies underlined that the volume occupied by the ablated tissue as measured at the end of the thermal ablation procedure is smaller than the volume occupied by the equivalent untreated tissue. Therefore, it resulted important to be able to adequately characterize the shrinkage of the tissue during a microwave thermal ablation procedure in order to correctly predict the true treatment volume; otherwise, the treatment safety as well as the efficacy can be compromised exposing peripheral structures to unwanted heating and affecting the assessment of the treatment’s technical success. The analysis and study of the thermally ablated tissue led mainly to perform extensive experimental investigations. Accordingly, ex vivo studies were conducted at four different laboratories: the Laboratory of the Division of Health Protection Technologies, ENEA Casaccia Research Centre, Rome (Italy); the Radiology Dept. of Regina Elena National Cancer Institute, Rome (Italy); the R&D laboratory of HS Hospital Service SpA, Aprilia (Italy); the Applied Radiology Laboratory of Hadassah Hebrew University Medical Center, Jerusalem (Israel), where I stayed for 6 months as visiting scholar. Moreover, thanks to the COST support, the laboratory of the Institute of Microbiology of the Academy of Sciences, Prague (Czech Republic), hosted me during a Short Term Scientific Mission (STSM) to conduct in vivo experiments of dielectric spectroscopy in the framework of a newborn joint scientific collaboration. In the present thesis, the conducted work is illustrated following the speculative project development. Specifically, the first chapter introduces the microwave ablation therapy, its operating principles, clinical and experimental applications and gaps; the second chapter concerns the used devices and the setups developed to conduct the experimental trials; and the third chapter illustrates the conducted experiments and their results. Finally, the outcomes are discussed in the conclusive chapter.