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Publication Monitoring microwave thermal ablation using electrical impedance tomography: an experimental feasibility study(IEEE, 2020) Bottiglieri, Anna; Dunne, Eoghan; McDermott, Barry; Cavagnaro, Marta; Porter, Emily; Farina, Laura; European Research Council; Horizon 2020; Science Foundation Ireland; European Regional Development FundLow-cost and reliable methods for monitoring the size of the ablation zone during microwave thermal ablation (MTA) are crucial in the oncological clinical practice. The aim of this work is to test the performance of electrical impedance tomography (EIT) for the real-time monitoring of the ablation area where relevant temperature increases occur. In this work, two experimental studies were performed with a 16-electrode EIT system using a liver-mimicking agar phantom. First, an EIT system was tested to monitor the cooling of the phantom from an initial temperature of about 72SC. Secondly, the heating and the consequent cooling of the phantom were monitored. The heating was performed using the MTA applicator operating at 30W for 10 minutes at 2.45GHz. The results reporting the voltage and temperature data acquired, as well as the reconstructed time series images, confirm the feasibility of EIT to monitor the changes of the electrical conductivity with temperature.Publication Detailed dielectric characterisation of the heart and great vessels(IEEE, 2020-03-15) Istuk, Niko; McDermott, Barry; Porter, Emily; Santorelli, Adam; Abedi, Soroush; O’Halloran, Martin; Joachimowicz, Nadine; Roussel, Helene; Horizon 2020The dielectric properties of biological tissues play a significant role in the planning and development of electro- magnetic thermal therapies. In most cases in the literature, heart is considered as a homogeneous organ and its dielectric properties values are reported as such. In this paper, the results of dielectric property measurements on nineteen different parts of four ovine hearts are presented. The results of the measurements indicate that the dielectric properties vary between the different parts of the heart and therefore, the heart should not be considered to be homogeneous for accurate electromagnetic modelling.Publication An empirical dielectric mixing model for biological tissues(IEEE, 2019-03-31) Salahuddin, Saqib; McDermott, Barry; Porter, Emily; O’Halloran, Martin; Elahi, Muhammad Adnan; Shahzad, Atif; European Research Council; Science Foundation Ireland; Irish Research CouncilDielectric properties of biological tissues are critically important for various electromagnetic based medical therapeutic and diagnostic technologies. This paper attempts to develop an empirical dielectric mixture model using the classical dielectric mixture theory and water content information to estimate the in-vivo dielectric properties of biological tissues over the microwave frequency range.Publication Bi-Frequency Symmetry Difference (BFSD) EIT in stroke diagnosis(EIT2019, 2019-07-01) McDermott, Barry; O'Halloran, Martin; Porter, Emily; Horizon 2020; European Research Council; Hardiman Research Scholarship, NUI GalwayBFSD-EIT can detect deviations in the inherent normal symmetry of the head due to, for example, the presence of a bleed or clot in stroke. We assess the potential of BFSD-EIT to robustly detect lesions under a series of modelling errors and calculate tolerable error levels before lesion detection is confounded.Publication Brain haemorrhage detection through SVM classification of impedance measurements(NUI Galway, 2018-07-17) McDermott, Barry; O'Halloran, Martin; Porter, Emily; Santorelli, AdamMachine Learning is becoming increasingly important in interpreting biological signals. In this work, we examine the potential for classification in brain haemorrhage detection. Numerical head and brain models with and without haemorrhagic lesions are designed. Impedance measurements from an electrode array positioned on the exterior of the head are used to train and test linear support vector machine (SVM) classifiers. The results show that this emerging measurement technique may have promise for detection and diagnosis of brain haemorrhage when coupled with such classifiers.Publication Static lesion detection in symmetric scenes using dual-frequency electrical impedance tomography(NUI Galway, 2019-01-18) McDermott, Barry; O'Halloran, Martin; Porter, Emily; Royal Academy of Medicine in Ireland Section of BioengineeringTissues have characteristic frequency dependent impendence to electrical current. This property is exploited by Electrical Impedance Tomography (EIT), an emerging biomedical imaging technique. In EIT, electrical conductivity maps of the interior of a body of interest can be reconstructed from voltage measurements collected from electrodes placed on the boundary in response to a prescribed pattern of injected electrical current. The ill-posed, poorly conditioned nature of the reconstruction problem has resulted in EIT having most success applied to time difference imaging, while simultaneously challenged by static scenes. Stroke is a biomedical imaging problem featuring a static lesion (a bleed or a clot), with effective treatment only possible once the aetiology is known. It is an application where the low-cost, portable, cheap and hazard free nature of EIT could be used to accelerate the patient treatment path and improve outcomes without the delay for CT or equivalent imaging. Here we present a novel algorithm for lesion detection, identification and location in numerical models of stroke using EIT measurements from two symmetrically equivalent electrode arrays, taken at two different frequencies of current stimulation.Publication 3D printable solid tissue-mimicking material for microwave phantoms(IEEE, 2018-09-10) McDermott, Barry; Porter, Emily; O’Halloran, Martin; Poudel, Anup; Biggs, Manus; Karode, Nireeksha S.; Coffey, Austin B.; Science Foundation Ireland; Horizon 2020; Hardiman Research Scholarship, NUI GalwayPhantoms provide valuable platforms for testing of medical devices including microwave diagnostic systems. This work describes a 3D printable solid tissue-mimicking material (TMM) for the production of such phantoms. The TMM is fabricated from ABS, SEBS and Carbon Black. The polymers ABS and SEBS produce a material that is 3D printable, robust and mechanically stable. Adjustment of the percentage of Carbon Black in a mixture alters the dielectric properties of the mixture. A variety of such mixtures were fabricated into 3D printable spools and the dielectric properties were measured across the 0.5 8.5 GHz band. The dielectric properties of a wide biological range are covered with the ability to emulate tissues within the range. The material hence can be used to print anatomically realistic and dielectrically accurate phantoms that can be multi- layered and as complex as desired depending on the study.