Non-invasive, point-of-care monitoring of shifts in intracranial biofluid volume using an electromagnetic skin patch sensor
Intracranial pressure (ICP) is an important diagnostic indicator of central nervous system function in disease states such as hydrocephalus, pseudotumor cerebri, subarachnoid hemorrhage and under various activities such as in high-speed fighter pilots and astronauts. Variations in ICP are driven by fluid volume changes of the primary components within the cranial cavity; these components include brain tissue, blood, and cerebrospinal fluid (CSF). This study will evaluate the hypothesis that changes in effective permittivity resulting from shifts in intracranial fluid volume in the human head can be non-invasively detected and monitored using an open circuit spiral resonator. The EM sensor consists of a single baseline component configured into a rectangular planar spiral with a self-resonant frequency response when impinged upon by external radio frequency sweeps. In this thesis, we have developed and evaluated a wearable, electromagnetic (EM) skin patch sensor to non-invasively detect shifts in fluid volume in a benchtop edema model and during induced intracranial bio-fluid volume shifts in human participants. Methods for inducing bio-fluid shifts include a 15 degree head down tilt (simulated microgravity) and application of lower body negative pressure (representative of countermeasure for astronauts and hyper-gravity experienced by fighter pilots). Additionally, a predictive model is constructed to estimate changes in an easyto- interpret medical parameter, intracranial pressure, corresponding with the sensor's signal response during induced bio-fluid shifts, over time. The leveraging of the change in dielectric properties during induced bio-fluid shift to detect and estimate shifts in ICP establishes a foundation for future work to develop a non-invasive, wearable ICP monitoring system utilizing microwave sensing and imaging (MSI).
Thesis (M.S.)-- Wichita State University, College of Engineering, Dept. of Biomedical Engineering