Active and Passive Microwave Radiometry for Transcutaneous Measurements of Temperature and Oxygen Saturation

In this work we explore two novel uses of microwave technology in biomedical applications. Introductory material on the electrical properties of biological tissues is presented to form the groundwork for the basic theory behind both techniques. First, we develop a technique that uses 60 GHz signals to detect changes in blood oxidation levels. Several atmospheric propagation models are adapted to predict oxygen resonance spectra near this frequency. We are able to predict and observe the changes in these levels as the blood ages up to 48 hours. Identical testing procedures performed using arterial blood gas (ABG) calibration samples with controlled oxygen levels show similar results to those obtained as bovine blood ages. We then discuss a potential application of this technique to the detection and diagnosis of skin cancer. The second application involves non-invasive measurement of internal body temperatures. Conventional methods of body temperature measurement provide a numerical value for a specific location on the body. This value is then applied to the remaining body systems as a whole. For example, a measurement of 37° C obtained orally can possibly lead to the erroneous conclusion that temperature is normal throughout the body. Temperature measurements made on specific internal organs can yield more information about the condition of the body, and can be invaluable as a tool for performing remote diagnostic evaluations. We explore the use of microwave radiometry in the low GHz spectrum to show that temperature information can be obtained directly and non-invasively for internal organs. We use the principles of black-body radiation theory combined with the reflection and transmission characteristics of biological tissues to predict the temperature delta that would be externally measured, given specific changes in the internal temperature. Data taken using a microwave radiometer and planar structures made with biological phantoms are compared to analytical results, showing that detection of internal temperature changes of can be performed externally in this manner