Browsing by Subject "biomedical"
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Item Impedance Spectroscopy Systems Suitable for Biomedical Cell Impedance Measurement(2013-06-03) Huang, HaoImpedance spectroscopy (IS) is an important technique for monitoring and detection of biomaterials. In order to enable point-of-care systems, low-cost IS systems capable of rapidly measuring a wide range of biomaterials are required. This thesis presents two IS systems, one in Printed Circuit Board level and the other in Integrated Circuit level. The board level system is built for preliminary experimental data collection; it is capable of measuring impedance from 1KHz to 100KHz with 200mV signal injection into cell sample. Experimental results show that magnitude and phase error are less than 6.6% and 2.2%, respectively. An IC level IS front-end is also proposed which utilizes a time-to-digital converter (TDC) and a peak detector circuit (PDC) for quick measurement of both impedance phase and magnitude, respectively. Designed in a 0.18?m CMOS process, the front-end is capable of performing impedance measurements in 6?s at frequencies ranging from 100Hz-10MHz and with a 100?-1M? dynamic range. Simulation results with cell impedance models show that the system achieves <2.5% magnitude and <2.2 degree phase error. The front-end consumes 28mW total power and occupies 0.4mm^2 area.Item Ultrasound-modulated optical tomography for biomedical applications(Texas A&M University, 2004-11-15) Li, JunI experimentally studied ultrasound-modulated optical tomography, which holds the promise for biomedical diagnosis. I measured the degree of polarization of laser speckles generated by scattered light transmitted through turbid media, investigated three signal-detection schemes for extracting the intensity of the ultrasound-modulated light, carried out experiments to image thick biological-tissue samples, and studied two techniques providing resolution in the cross-sections containing the ultrasonic axis. The study of degree of polarization presented results important for the understanding of polarization phenomena in turbid media. I explored an optical-filtering based signal detection scheme, improved the parallel-lock-in speckle detection scheme and proposed a speckle-contrast detection scheme. With the speckle-contrast detection scheme, I successfully obtained images of biological-tissue samples up to 50 mm thick. Further I studied frequency-swept ultrasound-modulated optical tomography for sub-millimeter resolution imaging, and developed ultrasound-modulated optical computed tomography that was based on a back-projection image reconstruction method and obtained clear images of biological-tissue samples.