ECE PhD Prospectus Defense: Bingxue Liu

Title: Advancing functional ultrasound and laser speckle based techniques to study cerebral hemodynamics and tissue dynamics

Presenter: Bingxue Liu

Advisor: Professor David Boas

Chair: Professor Lei Tian

Committee: Professor David Boas, Professor Lei Tian, Professor Jerome Mertz, Professor Anna Devor and Professor Irving Bigio

Abstract: Measuring cerebral microvascular flow dynamics and tissue dynamics associated with cellular function is important for studying neurovascular physiology in pathologies such as stroke. Functional ultrasound technique is capable to image deep brain-wide hemodynamics in rodents with high spatiotemporal resolution. However, the signal obtained with traditional power Doppler functional ultrasound results from a mixture of factors including the blood volume, blood flow and the ultrasound pressure distribution, making it difficult to interpret the results. Laser speckle contrast imaging (LSCI) measures 2D maps of cerebral blood flow in small animal brains such as mice. The contrast measured in LSCI also includes the static and slow varying components that contains information of brain tissue dynamics. But these components are less studied as compared to the fast dynamics of blood flow. In traditional wide-field LSCI, the contrast measured in the tissue is largely contaminated by neighboring blood vessels which reduces the static and slow components.

In this prospectus, I will focus on advancing technologies that exploit both ultrasound and laser speckle to measure blood flow and tissue dynamics. Firstly I will introduce an ultrasound speckle decorrelation-based time-lagged functional ultrasound technique (tl-fUS) which allows quantification of the relative changes in cerebral blood flow speed (rCBF-speed), cerebral blood volume(rCBV) and cerebral blood flow (rCBF), enabling more specific interpretation of the results. Then I will utilize laser speckle analysis to evaluate slow tissue dynamics by proposing a fiber-based laser speckle contrast optical spectroscopy (fb-SCOS) to improve the sensitivity to tissue dynamics. Lastly, I will apply ultrasound localized microscopy (ULM) to study the micro vascularization as well as functional reactivity during the treatment for striatal stroke.