Instrumentation for Functional Brain Monitoring with Intrinsic Optical Signals
Date
2019-12-05
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Abstract
Intrinsic optical signals are widely used in functional brain imaging techniques for measuring hemodynamic parameters, such as oxygen saturation and blood volume. These parameters indicate brain metabolism and serve as an indirect measurement of neural activity. In this thesis, I describe two techniques for hemodynamic monitoring from freely-moving animals. The first technique is single fiber spectroscopy, which enables measurements from a highly-localized volume in deep brain structures. I describe the optical system design for measuring reflectance spectra, Monte Carlo simulations for estimating the sampling volume, phantom experiments for rating the accuracy of hemodynamic parameter quantification, and finally, animal experiments for evaluating system performance in in-vivo experiments. I demonstrate that the single fiber spectroscopic system is capable of measuring spontaneous and stimulus-evoked hemodynamic response through a small diameter multimode fiber from non-line-of-sight brain regions in anesthetized and freely-moving animals. The second system is a miniaturized intrinsic optical sensing system (MiniIOS), a cost-effective, integrated system for measurement from the brain surface. The thesis covers the design and characterization of two versions of MiniIOS, the development of an empirical model for extracting hemodynamic parameters from the measured reflectance, as well as system validation in optical phantoms and animal experiments. The final system has a dimension of 5.5 mm×4.7 mm×1.8 mm and weight of 0.12 g. The system can be powered with a battery and operated as a stand-alone device integrating light source, detector, power supply, data acquisition and storage. Phantom experiments showed that the system was sensitive to both changes in oxygen saturation and blood volume fraction. A pilot animal experiment showed the system can be mounted on the head of a mouse without affecting its movement.
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Keywords
spectroscopy, brain, instrumentation, biophotonics, hemodynamics
Citation
Yu, L. (2019). Instrumentation for Functional Brain Monitoring with Intrinsic Optical Signals (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.