PhD Thesis Defense: Alicia Everitt

For Info on how to attend this video conference, please email alicia.c.everitt.TH@dartmouth.edu

"Electrical Impedance-based Monitoring for Intracranial Trauma"

Abstract

The intracranial space is notoriously difficult to monitor without a computed tomography (CT) or magnetic resonance imaging (MRI) scan. Bedside monitoring capabilities are limited to intracranial pressure (ICP) sensors, which only provide a single point metric incapable of differentiating a focal from diffuse injury. Intracranial trauma, including severe traumatic brain injury (TBI) and stroke, can have secondary injuries evolve anywhere from hours to days following the initial trauma. Prompt management of secondary injury is a clinical mainstay in improving patient prognosis. However, such injuries can vary in size, severity, location and presentation making monitoring crucial for management.

This thesis explores a novel approach to intracranial monitoring using electrical bioimpedance. Primary barriers to success in impedance-based intracranial sensitivity have been the high impedance boundary of the skull and poor current penetration. In this thesis we examine two novel approaches to interrogating the intracranial space, one invasive and one non-invasive. Within this work a novel bioimpedance-based monitor (BIM) for intracranial trauma was fully conceptualized, designed and characterized. This device was deployed in two extensive animal models developed to induce intracranial volume changes of varied conductivity and pathology. The BIM successfully detected focal injury within these large animal models, differentiated high impedance (e.g. ischemic) from low impedance (e.g. hemorrhagic) events, localized the region of injury within the skull, and showed feasible translation from an invasive to a non-invasive monitoring approach. Additional Finite Element Model analysis on an anatomically accurate human mesh supported the potential for translation to a human cohort. Within this study the implementation of novel electrode positioning was shown to significantly increase current density and sensitivity within the intracranial space. Finally, the BIM was redesigned for a patient-interface in an intensive care unit, enabling the start of a now underway first-in-human study. With continued effort, the work presented here may one day provide real-time, in-clinic, life- and brain-saving detection of evolving intracranial pathologies.

Thesis Committee

• Ryan Halter, PhD
• Keith Paulsen, PhD
• David Bauer, MD
• Fernando Seoane-Martinez, PhD

Contact

For more information, contact Theresa Fuller at theresa.d.fuller@dartmouth.edu.