Year: 2019
Type: dissertation
Abstract: ENGLISH ABSTRACT: This thesis entails the development of a proof-of-concept device which may \nbe used for measuring volumetric blood flow. Blood circulation is primarily \ndetermined by measuring blood velocity in arteries. This does not take into \naccount that blood vessel diameter can vary with various medical conditions \nand result in insufficient oxygenated blood being delivered to organs. Insuffi- \ncient volume blood flow to the brain and kidney can cause strokes, death of \nbrain tissue, heart attacks and even death. \nA device capable of measuring diameter and velocity was developed. Diameter \nwas measured using a bioimpedance catheter while velocity was measured using \na self-mixing interferometer. Validation testing as well as in vitro testing \nwas performed on each. \nValidation testing and in vitro testing of the bioimpedance catheter was performed \nin various sized vials filled with horse blood to simulate various sized \nblood vessels. The voltage over the catheter electrodes was measured and \nrecorded. It could be seen that there is an inverse relation between vial diameter \nand measured voltage due to the varying impedance in different sized vials. \nThe self-mixing interferometer was validated by tracking the excitation frequency \nof a speaker diaphragm. A magnitude peak could be seen on a FFT \nat various excitation frequencies of the speaker. During in vitro testing it was \nfound that the signal-to-noise ratio was insufficient to reliably measure the \nDoppler frequency of red blood cells in flow. Various iterations were made to the device to decrease noise, but ultimately it was determined that the sensitivity \nof the photodiode used to monitor the self-mixing signal was limiting \nthe device. It was apparent that the signals reflected from the red blood cells \nwere too small to be detected by the specific photodiode used. \nIt was concluded that it is feasible to measure volume flow by using a combination \nof bioimpedance and a self-mixing interferometer provided a higher grade \nlaser module with a higher sensitivity photodiode is used. In vivo testing will \nbe necessary to determine the effiects of tissue surrounding blood vessels on \nbioimpedance measurements.
Author: Philipp Frohmann
Language: English
Subfield: Biomedical Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2948013435