High-Resolution Deep-Tissue Microwave Thermometry

Streeter, Robert

Graduate Thesis Or Dissertation

High-Resolution Deep-Tissue Microwave Thermometry Public Deposited

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Citeable URL: https://scholar.colorado.edu/concern/graduate_thesis_or_dissertations/4x51hk517

Abstract

Temperature is a basic human vital sign. Current techniques for measuring human body temperature rely on either superficial layer measurements (infrared or tympanic membrane sensors), invasive techniques ranging from oral to rectal to implanted sensors, or are exclusive to clinical settings due to being prohibitively large, expensive, or power-dependent (such as magnetic resonance imaging). This thesis presents an alternative approach: microwave radiometry. All objects above zero Kelvin emit broad-spectrum electromagnetic radiation. In the low GHz frequency range, the power of that radiation is proportional to the physical temperature of the object doing the emitting. This power can be measured and analyzed with a receiver system that includes a near-field receiving probe, a sensitive radiometer and detector, as well as a software processing algorithm. This thesis presents three radiometer topologies in detail, including considerations of each element in the system, in addition to simulations and measurements. Temperature determination of a deeply buried tissue layer poses an ill-defined inverse problem. To help overcome this, the properties of each layer being measured must be known. This thesis further presents a frequency-domain characterization approach that shows great promise for determining the necessary properties of a stack of complex lossy dielectrics, such as human tissues. The applications for this new temperature measurement technique are deeply rooted in medical diagnosis, treatment, and monitoring, but extend into other fields, such as manufacturing and waste-to-fuel conversion.

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