Computational Modelling of Electrical Properties of Thyroid and Parathyroid Tissue

Parathyroid gland identification is an important consideration in order to decrease the inci- dence of post-surgical complications associated with thyroid surgeries. Electrical Impedance Spectroscopy (EIS) based tissue differentiation recently emerged as a promising non-invasive technique that could enhance the tissues separation, and parathyroid preservation in a surgery setting. The aim of the work presented in this thesis is to implement a computational modelling approach in order to elucidate the differences between healthy thyroid and parathyroid tissue impedance spectra which could permit their differentiation during surgery. Multiscale finite element thyroid and parathyroid models have been constructed with the main objective to investigate the impact of morphology and composition on the bulk electrical behaviour of both tissues. The multiscale pipeline represents the hierarchical tissue structure from cellu- lar to tissue scale including a novel mesoscale for the thyroid follicular arrangements. A comprehensive inter- and intracompartmental sensitivity study provided an insight into the impact of the variations in geometrical and electrical properties of tissue structures on electrical impedance spectra of both tissue types suggesting a successful separability between the computed thyroid and parathyroid impedance spectra indices. Moreover, the modelled results obtained through the variation of geometrical parameters demonstrating the natural variability in tissue morphology provided a good agreement with the in vivo measured data acquired and published by Hillary et al. In addition, the verification of selected homogeneity assumptions and the exploration of measurement accuracy and di↵erent probe configurations provided further recommendations for future work concerning computational modelling, experimental data collection and EIS device design improvements. In particular, the outcomes of this computational study re- vealed the importance of additional experimental work concerning the electrical properties measurements of biological tissue materials, and the significance of tissue preparation and measurement accuracy in obtaining thyroid and parathyroid measurements with a tetrapolar EIS probe.