Thesis (M. Eng.)--Harvard-MIT Division of Health Sciences and Technology, 2008. / Includes bibliographical references (p. 105-121). / The skin microcirculation performs a range of vital functions, such as maintaining nutritional perfusion to the tissues and overall thermoregulation. Not only does impairment to the skin blood supply lead to tissue necrosis and other disease complications, increasing evidence shows that dysfunctional vasoreactivity in the skin microcirculation is associated with multiple disease states, including hypertension, diabetes mellitus, hypercholesterolemia, peripheral vascular disease, and coronary artery disease, and it is one of the earliest indicators of systemic endothelial dysfunction, the precursor to atherosclerotic disease. Endothelial dysfunction is functionally characterized by abnormal vasomotor response to either a pharmacological or flow-mediated stimulus and can be demonstrated in the skin by measuring reperfusion following a period of ischemia, a phenomenon known as post-occlusive reactive hyperemia (PORH). In my research, I have reviewed the literature regarding endothelial dysfunction and its association with a wide range of cardiovascular risk factors. I have also described the mechanisms thought to link endothelial function in the central vascular beds (i.e. coronary) to that of peripheral conduit vessels and the microcirculation. The knowledge thus gathered confirmed that the microcirculation of the skin is an appropriate site for endothelial function assessment. The ultimate goal of my thesis is to design a noninvasive sensor that is capable of obtaining a quantitative measure of skin perfusion, continuously and in real-time, using the principle of thermal diffusion in perfused tissue. I performed preliminary noninvasive endothelial function testing with a modified Thermal Diffusion Probe (TDP), which has been previously validated for absolute perfusion measurement in an invasive setting. / (cont.) Based on an initial analysis, I have shown that thermal surface perfusion measurements are feasible and reflect the natural perfusion and temperature fluctuations intrinsic to skin tissue. I also established guidelines for determining quantitative parameters of reactivity from tests of PORH as well as temporal parameters of perfusion variations over time through a spectral analysis of resting blood flow. After establishing the necessary thermal boundary conditions for obtaining surface perfusion measurements, I embarked on a process of computer-assisted modeling and rapid prototyping of various design iterations on an insulated sensor housing, with subsequent fabrication of first generation noninvasive sensors. As a result of these initial sensor designs, specifications for the sensor housing were created to ensure that the appropriate thermal field would be established at the skin measurement site - an important step as it permits the most accurate determination of tissue thermal properties. Finally, I propose a candidate design for an ideal sensor capable of improving the reproducibility of noninvasive perfusion measurements on skin. The development of a noninvasive measure of endothelial dysfunction in the skin is of great value in the early identification of individuals at risk for atherosclerotic complications. Furthermore, the nature of such a technique would provide quantitative information on the presence of a disorder, the extent of dysfunction, and the effectiveness of treatment interventions. / by Vivian V. Li. / M.Eng.
| Identifer | oai:union.ndltd.org:MIT/oai:dspace.mit.edu:1721.1/43874 |
| Date | January 2008 |
| Creators | Li, Vivian V. (Vivian Victoria) |
| Contributors | H. Frederick Bowman., Harvard University--MIT Division of Health Sciences and Technology., Harvard University--MIT Division of Health Sciences and Technology. |
| Publisher | Massachusetts Institute of Technology |
| Source Sets | M.I.T. Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 121 p., application/pdf |
| Rights | M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission., http://dspace.mit.edu/handle/1721.1/7582 |
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