Honors Theses

Date of Award

5-2024

Document Type

Undergraduate Thesis

Degree Name

BS

Department

Mechanical Engineering

Faculty Mentor

michael Francis

Advisor(s)

David Nelson, Josh Keller

Abstract

Peripheral Artery Disease (PAD) is a progressive cardiovascular condition characterized by atherosclerosis in the extremities. It affects up to 10 million adults in the United States and is associated with an elevated risk of heart attack and stroke. Up to 50% of people with PAD are asymptomatic and undiagnosed. This presents the need for a rapid, inexpensive, and noninvasive screening tool that can be easily used to diagnose PAD. We developed a device, REFLO (Rapid Electromagnetic FLOw device), to detect low blood flow and diagnose PAD. The device uses lowpower radio frequency energy (35 GHz) to heat the skin and measure the subsequent temperature change. There is a relationship between skin surface temperature and volumetric blood flow in the skin, and we hypothesized that the rate of skin heating in response to millimeter wave irradiation is a function of the underlying volumetric blood flow.

This work presents the results of two cohorts of controlled flow experiments on humans. Each experiment was performed as a series of 3-minute heating periods followed by 3-minute natural cooling periods during baseline, occluded, and post-occluded hyperemic flow. Nonlinear regression analysis was used to fit temperature data and obtain a thermal constant, k. In the pilot study, N = 7 and each subject volunteered for 1 visit. During the heating period, significance was observed between the k-values in the baseline and post-occlusion periods (p = 0.0039). During the cooling period, significance was observed between the baseline and occlusion periods (p = 0.0014), as well as between the occlusion and post-occlusion periods (p = 0.0469). In the reliability study, N = 5 and each subject returned for 3 visits. During the heating period, significance was observed between the baseline and post-occlusion period (p = 0.0128), as well as between the occlusion and post-occlusion periods (p = 0.0160). During the cooling period, significance was observed between the baseline and occlusion periods (p = 0.0004), as well as between the baseline and post-occlusion periods (p = 0.0044). Two-way ANOVA revealed that flow and subject had a significant effect on the rate of skin heating and cooling, while visit had no effect.

Results suggest that millimeter wave irradiation can be used to distinguish between different volumetric blood flow rates in humans. Utilizing the rate of skin cooling rather than skin heating has proven to be more consistent for distinguishing flow rates. Future clinical testing and device modifications will improve REFLO’s ability to distinguish between flow rates and evaluate the device’s ability to discern PAD patients from individuals without cardiovascular disease.

Comments

© 2024 Julia Nelson ALL RIGHTS RESERVED

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