Yueh-Chi Wu
BME PhD Proposal Presentation

Date: 2026-05-05
Time: 13:00-15:00PM
Location / Meeting Link: HSRB / https://emory.zoom.us/j/93282915123

Committee Members:
Erin M. Buckley, PhD(Advisor) John Oshinski, PhD Ofer Sadan, MD, PhD Shella Keilholz, PhD David Myers, PhD


Title: Diffuse Correlation Spectroscopy for Assessing Microvascular Cerebral Hemodynamics and Predicting Outcomes After Subarachnoid Hemorrhage

Abstract:
This proposal addresses a central unmet need in aneurysmal subarachnoid hemorrhage (SAH): the lack of bedside tools that directly measure microvascular physiology and identify patients who remain at risk for delayed cerebral ischemia despite vasospasm-directed therapy. Diffuse optical techniques, including diffuse correlation spectroscopy (DCS) and speckle contrast optical spectroscopy (SCOS), are noninvasive bedside methods that can continuously quantify regional cerebral hemodynamics and autoregulatory function. These tools therefore offer a unique opportunity to monitor brain health in real time and to move beyond conventional large-vessel surveillance toward direct assessment of treatment-responsive microvascular physiology. In Aim 1, I will determine whether microvascular cerebral blood flow (CBF) increases in response to intrathecal nicardipine treatment and whether a blunted response is associated with delayed cerebral ischemia (DCI) and exploratory functional outcome. Preliminary data support this aim: DCS detected significant increases in relative CBF after intrathecal nicardipine on treatment days 1, 2, and 3, while the largest prognostic differences by DCI and modified Rankin Scale (mRS) were observed on day 1. These findings suggest that the early microvascular response to treatment may provide clinically meaningful prognostic information. In Aim 2, I will determine whether microvascular autoregulation is impaired after SAH, whether dysfunction is worse in patients with vasospasm, and whether autoregulatory responses to treatment predict outcome. Using SCOS- and DCS-derived autoregulatory metrics, this aim will extend bedside monitoring beyond treatment- responsive flow changes to dynamic cerebrovascular control. Preliminary data suggest that autoregulatory metrics, particularly on day 2, may distinguish poor from favorable outcome, supporting the feasibility of autoregulation-based risk stratification in this population. In Aim 3, I will improve the accuracy of DCS-derived cerebral blood flow estimation in adults by comparing homogeneous, layered, modified Beer-Lambert law (MBLL)-based, and pressure-modulation-constrained approaches against arterial spin labeling MRI (ASL-MRI). Preliminary analyses show that a semi-infinite MBLL method significantly correlates with MRI-derived relative CBF change, and that a two-layer pressure-modulation MBLL approach shows even stronger agreement, suggesting that pressure-constrained layered modeling may improve separation of extracerebral and cerebral signals. Together, these studies will define treatment-responsive and autoregulatory microvascular biomarkers while strengthening the methodological foundation needed to translate DCS and SCOS into practical bedside tools for individualized monitoring and treatment guidance after SAH.