1.Understand the different components of fMRI signals and hemodynamic functions.
Blood oxygen level dependent (BOLD) is the main contrast in fMRI signal. However, there are different components in fMRI signals, such as inflow, etc. In this project, we will explore the different components of fMRI signals and how the location of the voxel in the brain influence these components. More importantly, we will explore the novel ways to extract these components and use them to assess different aspect of the brain.
2.Denoise fMRI/fNIRS signal using novel “catch-all” nuisance regressors
Functional MRI/NIRS have emerged as a key imaging technique for obtaining the brain functions. Significant disease-related changes in resting state and task activations have been found in patients with Alzheimer, Schizophrenia, Parkinson, traumatic brain injury, etc. However, interpretation of fMRI/NIRS signals is complex, because BOLD (fMRI)/oxygenation signals (NIRS) are blood-related and indirectly represents neuronal activations through the neurovascular coupling. Therefore, any physiological fluctuations that change blood flow/volume and oxygenation may also alter these signals, resulting in “false” result. In this project, we will explore different methods in 1) recording “catch-all” nuisance regressors, which reflect pure physiological fluctuations, concurrently with the functional experiments; 2) remove these nuisance regressors from functional data.
3.Develop intrinsic perfusion bolus to track cerebral blood flow.
The ability to track cerebral blood flow in the brain is crucial in assessing many brain diseases. The “golden” standard of perfusion MRI is to inject exogenous contrast agent, such as gadolinium, and track its passage through the brain using MRI. This method could be harmful to some subjects and has limited study time. In this project, we will extract a spontaneous intrinsic oscillation of the blood oxygen level dependent (BOLD) fMRI signal from human subjects. It will be used as a natural “bolus” and tracked throughout the brain. We will try to develop a set of perfusion parameters based on this natural bolus and validate them using standard perfusion MRI or Arterial spin labeling.
4.Enhance perfusion parameters using gas-challenge (NIRS/MRI)
Cerebral vascular health can be evaluated by a “stress” test, such as respiratory challenges. In this project, we will develop stress test using elevated CO2. Since CO2 is vessel dilator, elevated CO2 can test cerebral blood vessels by dilating them. Moreover, we will modulate these respiratory challenges by varying CO2 level periodically and use these “encoded” oscillations to assess the cerebral blood flow. The resulting flow and dilation parameters can be used to assess cerebral vascular health in populations, such as high school American football player.
5.Understand Brain-body vascular relationships using NIRS
Vascular disease affects millions of Americans. It is known that vascular system consists of many components, such as cerebral, coronary and peripheral systems. All these systems are highly related. In this project, we will use small NIRS system to assess vascular integrity at the peripheries, such as fingertips and toes. The goal is to 1) develop effective imaging biomarkers to assess and have early detection of peripheral artery disease; 2) understand the relationship between peripheral vascular health and cerebral and coronary vascular health; and 3) use easy peripheral vascular measurement to infer the health of cerebral and coronary vasculature.
6.Study brain networks on craving in cigarette smokers.
In this project, we will study how brain activation changes in response to smoking tobacco cigarettes that contain different amounts of nicotine. We will use fMRI and NIRS to monitor and compare blood flow changes in your brain before and after you smoke a cigarette. The dynamic changes in the resting state networks between these two state will 1) shed light on the effect of cigarette smoking on craving of smokers and 2) help us to distinguish the effects of smoking and nicotine on the brain.