Doctor of Philosophy (PhD), Wright State University, 2023, Engineering PhD

Blood flow dynamics plays a critical role in maintaining tissue health, as it delivers nutrients and oxygen while removing waste products. It is especially important when there is a disruption in cerebral autoregulation due to trauma, which can induce ischemia or hyperemia and can lead to secondary brain injury. Thus, there is a need for noninvasive techniques that can allow continuous monitoring of blood flow during intervention. Optical techniques have become increasingly practical for measuring blood flow due to their non-invasive, continuous, and relatively lower-cost nature. This research focused on developing a low-cost, scalable optical technique for measuring blood flow by implementing speckle contrast optical spectroscopy using a fiber-camera-based approach. This technique is particularly well-suited for measuring blood flow in deep tissues, such as the brain, which is challenging to access using traditional optical methods. A two-channel continuous wave speckle contrast optical spectroscopy device was developed, and the device was rigorously tested using phantoms. Then, it is applied to monitor blood flow changes in the brain following traumatic brain injury (TBI) in mice. The results indicate that trauma-induced significant blood flow decreases consistent with the recent literature. Overall, this approach provides noninvasive continuous measurements of blood flow in preclinical models such as traumatic brain injury.

Committee: Ulas Sunar Ph.D. (Advisor); Tarun Goswami Ph.D. (Committee Member); Keiichiro Susuki Ph.D. (Committee Member); Robert Lober M.D., Ph.D. (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Biophysics; Engineering; Optics

Master of Science in Biomedical Engineering (MSBME), Wright State University, 2019, Biomedical Engineering

Neurovascular coupling is an important concept that indicates the direct link between neuronal electrical firing with the vascular hemodynamic changes. Functional Near Infrared Spectroscopy (fNIRS) can measure changes in cerebral vascular parameters of oxy-hemoglobin and deoxyhemoglobin concentrations and thus can provide neuronal activity through neurovascular coupling. Currently many commercial fNIRS devices are available, but they are limited by the number of channels (usually having only 8 detectors), which can limit the sensitivity, contrast, and resolution of imaging. High-density imaging can improve sensitivity, contrast, and resolution by providing many measurements and averaging the signals originating from the target cerebral focus area compared to background tissue. Here a multi-channel, low-cost, high-density imaging system based on scientific CMOS (Complementary Metal-Oxide-Semiconductor) detector will be presented. The CMOS camera is fiber-coupled such that on one end fibers are focused on the pixels on the CMOS camera, which allows individual pixels (or binned sub-pixels) to act as detectors, while the other end of the fibers can be positioned on a wearable optical probe. After the device details, I will show the device validation using a series of the dynamic flow phantom experiments mimicking the brain activation and finally human motor cortex experiments (finger tapping experiments). The results demonstrate that this system can obtain high-density data sets with higher contrast and resolution. This wearable, high-density optical neuroimaging technology is expected to find many applications including pediatric neuroimaging at clinics and assessing human cognitive performance.

Committee: Ulas Sunar Ph.D. (Advisor); Keiichiro Susuki Ph.D. (Committee Member); Tarun Goswami Ph.D. (Committee Member) Subjects: Biomedical Engineering; Biomedical Research; Engineering; Optics

Master of Science, The Ohio State University, 2017, Allied Medicine

Objective: Patient physiological monitoring creates a large number of alarms, most of which are false. High numbers of false alarms inhibit discrimination between true and false alarms leading to the neglect of future alarms, both false and true, risking slower identification and reaction to hazardous conditions. This study introduces several methods, especially novel visualizations, to discern how alarms are temporally distributed, and how alarms coalesce as sets of alarms. Methods: Retrospective evaluation of data extracted from a hospital-system-wide middleware alarm escalation software database containing million of alarms over a time period of 16 to 18 months. Multiple comparison of means is employed as well as several visualizations including, box-and-whisker plots, periodograms, and a novel Gantt-inspired visualization in combination with a histogram. Results: Multiple comparison of means finds statistically significant differences between alarms occuring on an hourly, daily, and shift-wise basis. Box-and-whisker visualization of alarms by hour over a week reveals visual signatures of alarm occurence varying on a unit-by-unit basis. Periodograms reveal multiple periodicities in alarm occurrence varying on a unit-by-unit basis. Study of simultaneous alarms uncovers quantizations such as the highest numbers of alarms occuring by unit (6 to 10 simultaneous alarms). Gantt-style visualization of simultaneous alarm occurences uncovers interesting alarm signatures such as threshold hovering of alarms, appearing as a visual stutter, or the redundancy of certain alarms (e.g. bradycardia and low heart rate) which occur in parallel.Long-term, there is a large percentage of time that at least one alarm is sounding on a unit (18.1% to 62.2%). Conclusions: Retrospective evaluation of a middleware alarm escalation software database in combination with novel visualization provides a valuable heuristic tool.

Committee: Emily Patterson (Advisor); Laurie Rinehart-Thompson (Committee Member); Michael Rayo F (Committee Member) Subjects: Engineering; Health Care; Health Sciences; Information Science; Information Systems; Medicine