Browsing by Author "Singh, Manmohan"
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Item Assessing Mouse Brain Elasticity Using Air-Pulse Based Optical Coherence Elastography(2017-10-12) Goh, Megan; Liu, Chih-Hao; Singh, Manmohan; Raghunathan, RakshaCurrent diagnostic methods are able to detect severe brain trauma but are unable to detect the microscopic brain injuries that regularly occur during a concussion. Our research aims to explore a potential alternative method to detect a wider range of severity in concussions through comparing the changes in the biomechanical properties of pre- and post-concussed brain tissue using optical coherence elastography (OCE). This study is a proof of concept to see if OCE can distinguish different regions within the brain based on biomechanical properties. In this study, we hope to distinguish the hippocampus, a complex structure located in the medial temporal part of the brain beneath the cerebral cortex, from the rest of the brain. Our results show that the hippocampus is softer than the cortex of the brain, which corresponds to currently available literature. In this study, we were able to show that OCE could detect differences in the biomechanical properties of different regions of the brain.Item Assessing the Vasculature Changes in Murine Fetal Brain Upon Alcohol Exposure(2017-10-12) Nguyen, Jennifer; Raghunathan, Raksha; Wu, Chen; Singh, Manmohan; Liu, Chih-HaoFetal Alcohol spectrum disorder (FASD) refers to a broad spectrum of abnormalities that arise due to prenatal alcohol exposure (PAE). The severity of the abnormality depends on the amount of alcohol consumed and period of consumption during gestation. A large number of women continue to consume alcohol even during the second trimester of pregnancy, a critical period for fetal neurogenesis and angiogenesis. OCT is an optical analog of ultrasound. 3D non-invasive imaging technique with high spatial resolution. OCT has shown to be extremely useful in embryonic imaging. Speckle variance OCT (SVOCT), is a functional extension of OCT that has been used to study vasculature development in embryos. We use SVOCT, to detect vasculature changes in the embryonic brain in utero, minutes after maternal alcohol consumption. The results show that there is a decrease in fetal vessel diameter within the first 10 minutes and it persisted for 45 minutes after maternal alcohol consumption, indicating that ethanol is a possible vasoconstrictor on the fetal brain. This project was completed with contributions from Rajesh C. Miranda from the Neuroscience and Experimental Therapeutics, Texas A&M Health Science Center.Item Assessing Tissue Biomechanical Properties with Noncontact Dynamic Optical Coherence Elastography(2018-05) Singh, Manmohan; Larin, Kirill V.; Akay, Metin; Twa, Michael D.; Gifford, Howard C.; Mayerich, DavidThis dissertation reports the development of noncontact techniques to quantify the biomechanical properties of various tissues utilizing optical coherence elastography. These techniques are critical for screening, detection, and monitoring of disease onset and progression as well as evaluating the effectiveness of various therapeutic procedures. The dissertation is divided into two major sections: 1) analyzing the localized dynamic deformation and 2) analyzing elastic wave propagation to quantify tissue biomechanical properties. Each of these sections is further divided. The localized dynamic tissue deformation analysis section has two sub-sections: a) real-time visual feedback and biomechanical assessment of dermal filler injections and b) evaluating the changes in local cardiac biomechanical properties after myocardial infarction. The elastic wave propagation analysis section has seven sub-sections: a) evaluating the changes in corneal biomechanical properties due to riboflavin/UV-A corneal collagen cross-linking, b) comparing the changes in corneal biomechanical properties induced by riboflavin/UV-A and rose-bengal/green light collagen cross-linking, c) quantifying the effects of tissue hydration on the stiffness of the cornea, d) assessing the elastic anisotropy of the cornea as a function of intraocular pressure, e) evaluating the changes in cardiac elastic anisotropy after myocardial infarction, f) development of an ultra-fast, single-shot, elastography technique, and g) development of a noncontact technique ca pable of assessing corneal geometry, eye-globe intraocular pressure, and corneal stiffness with a single instrument. Finally, the spatio-temporal properties of air-pulse induced displacement were characterized, and the repeatability and sensitivity of the OCE techniques described in this dissertation were compared to the “gold standard” of mechanical testing. The contributions of this work are crucial steps for the further development and clinical application of rapid, accurate, robust, and safe techniques capable of evaluating tissue biomechanical properties for early detection and monitoring of diseases.