Clinical Applications of Electrical Impedance Tomography in Stroke and Traumatic Brain Injury

Electrical Impedance Tomography (EIT) is a medical imaging technology which uses voltage measurements on the boundaries to reconstruct internal conductivity changes. When applied to imaging brain function, EIT is challenged by the unique geometry of the head and the high variability in the conductivities of brain tissue. Stroke and Trau-matic Brain Injury (TBI) are two of the leading causes of death and long-term disability worldwide. It has been suggested that EIT, which is already in clinical use primarily as a means of assessing lung function, could be used as a pre-hospital diagnostic tool for stroke and TBI, and for bedside monitoring for brain injury patients. The main aim of this PhD thesis is to bring the application of EIT in brain injury closer to regular clinical use. Chapter 1 introduces the concepts of EIT, stroke and TBI, and provides a comprehensive review of clinically relevant neuroimaging techniques and the current state of brain EIT. Chapter 2 presents the results of a series of lab experiments designed to investigate the characteristics and mechanisms of drift in measured boundary voltages, which is the key technical barrier to brain monitoring with EIT. Ex-periments were conducted on lab phantoms, vegetable skin, and healthy human subjects. Chapter 3 describes a feasibility study of monitoring for brain injury with EIT over several hours, using noise recorded on real healthy volunteers. This study also compares the performance of different electrode types. Chapter 4 presents a clinical pilot study performed on acute stroke patients. Multi-frequency (MF) EIT data were record-ed on patients and healthy controls to create the first of its kind clinical EIT dataset to be used as a resource for future research for the EIT community. Finally, the ability to identify stroke patients is demonstrated on the clinical EIT dataset.