Graduate Studies

 

First Advisor

Gregory R. Bashford

Second Advisor

Yingying Wang

Committee Members

Steven Barlow

Date of this Version

11-2024

Document Type

Thesis

Citation

A thesis presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of Requirements for the degree of Master of Science

Major: Agricultural and Biological Systems Engineering

Under the Supervision of Professors Gregory R. Bashford and Yingying Wang

Lincoln, Nebraska, November 2024

Comments

Copyright 2024, Fatima Sibaii. Used by permission

Abstract

Stroke remains a leading cause of death and disability worldwide, with over 12.2 million new cases every year. Ischemic stroke occurs when a cerebral blood vessel becomes obstructed, leading to neural death in brain regions affected by loss of blood.

Functional Transcranial Doppler (fTCD) is a neuroimaging modality that measures cerebral blood flow change in the brain following stimulation. Functional near-infrared spectroscopy (fNIRS) is a complementary modality that estimates regional cerebral blood flow change in oxygenated and deoxygenated hemoglobin in the brain following stimulation. Both modalities are useful in monitoring cerebral blood flow in real time.

Pneumo-tactile somatosensory stimulation may have therapeutic effects for acute ischemic stroke due to its initiating collateral blood flow which may protect cerebral areas at risk of loss of oxygen. This kind of stimulation consists of pressure pulses travelling across the skin. The long-term goal of this work is to apply pneumo-tactile somatosensory stimulation to stroke patients in the acute phase to improve stroke outcomes, while the short-term goal is to understand the effects of pneumo-tactile stimulation on cerebral blood flow in healthy subjects.

Simultaneous fNIRS and fTCD were used to study cerebral hemodynamic changes during pneumo-tactile somatosensory stimulation of the right palm at a speed of 25 cm/s under two different sizes of area stimulated (thumb + index [one-finger] versus thumb + index + middle [two-finger]). The cerebral blood flow response recorded by fNIRS and fTCD as a function of time was compared to gaining more understanding of similarities and differences between the two modalities.

Interestingly, fTCD results showed significance contralaterally during the one-finger condition, as expected, but ipsilaterally during the two-finger condition, which was unexpected. Pulsatility index percent change was significantly different from zero during both conditions bilaterally, suggesting a stimulus-evoked change in downstream arterial diameters. The change in HbO concentration measured by fNIRS was significantly different from 0 during the two-finger condition bilaterally, and the one- and two-finger conditions were significantly different. The recorded amplitude features of fNIRS and fTCD were somewhat comparable, with similar trends but a few differences. This work demonstrates the feasibility of simultaneous recording of fNIRS and fTCD.

Advisors: Gregory R. Bashford and Yingying Wang

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