A bioimpedance - based re-configurable electrode method for early detection of arteriosclerosis indicators

Arteriosclerosis is a medical condition that is associated with the stiffening of arteries due to the loss of elasticity as a result of ageing and is often asymptomatic. It occurs in almost every person and can lead to life-threatening diseases, including heart attacks and strokes. Approximately 50% of all stroke cases world-wide result from asymptomatic atherosclerosis - a type of arteriosclerosis - of the carotid artery. The standard non-invasive methods for detection of atherosclerosis are ultrasonography, computed tomography and magnetic resonance imaging. Only confirmed symptomatic cases are referred for such examinations. This is because these methods are either expensive, heavily operator dependent, not always accurately handled, potentially harmful, significantly cumbersome, or only available at well-equipped medical centres. Therefore, there is a need for routine screening of major arteries like the carotid artery. Doing so might help identify potentially millions of cases that are either asymptomatic or symptomatic patients in rural areas or who are poor. This thesis describes how bio-impedance can overcome the limitations of the aforementioned methods - without attempting to replace them in terms of clinical validity or accuracy - to eventually provide indicative outcomes for routine screening that would allow even asymptomatic patients to be refereed for further clinical assessment if needed. Work done includes the design, implementation and evaluation, through idealised FEM simulations and phantom experiments, of a bioimpedance- based re-configurable electrode method for early detection of arteriosclerosis indicators. It utilises impedance measurements taken from an array of electrodes by means of a novel scanning method, to transcutaneously detect vascular structures as well as vascular occlusions. It also explores the possibility of grouping multiple small electrodes to form re-configurable electrodes, in terms of size, shape and position. The results from simulations and experiments demonstrate that the proposed scanning method can overcome the need for accurate electrode placement by identifying vessel orientation and features and by selecting the electrode that are more relevant to the targeted vascular structure with high accuracy. The results also show that the resulting localised electrodes exhibit approximately 25% improved sensitivity when compared to conventional electrodes. It was also confirmed that occlusions could be detected both through area scans with an accuracy of 98% as well as through localised flow measurements