BIS Seminar

Speaker: Luis Hernandez-Garcia

Bio: I received my bachelor's degree in applied science from the University of North Carolina at Chapel Hill in 1992. I stayed at UNC-CH for my Master's (1994) and Ph.D. degrees (1998), although the last two years were spent conducting my research at the Nathan Kline Institute in Orangeburg, NY. I held a post-doctoral fellowship at Wake Forest University in Winslon-Salem, NC from 1998-1999. I then moved to the University of Michigan in Ann Arbor, MI, where I currently work as a research professor in the Radiology department.

I have been Principal investigator and co-investigator on multiple NIH funded projects and collaborated with a wide range of multi-disciplinary teams including the departments of Biostatistics, Neurology, Biomedical Engineering, Electrical Engineering, Psychology and Psychiatry. My research goals are centered on the development of non-invasive, image guided neuromodulation.

I have done some work in the development of transcranial magnetic stimulation (TMS), direct current stimulation (TDCS) and focused ultrasound stimulation (FUS), but the largest share of my research career so far has been spent on the development of techniques to image brain function using MRI. I have spent significant effort working in Functional MRI using both the BOLD effect and perfusion imaging using arterial spin labeling. Arterial spin labeling (ASL) imaging methods are very attractive because they can image brain perfusion and other hemodynamic parameters quantitatively without the need for contrast agent injections. These parameters are important indicators of the brain's activity as well as being important biomarkers. I have worked extensively on developing ASL acquisition and analysis methods, including a series of papers to establish a consensus in the perfusion imaging community.

Abstract: In this presentation, I will discuss a new MRI-based technique to measure the velocity distribution of water inside each voxel of an image by using modified velocity-selective RF pulses to encode the three-dimensional velocity distribution of convective flow in each voxel, analogously to Diffusion Tensor and Q-space imaging. I will discuss the physical principles behind velocity spectrum imaging. I will also discuss its implementation challenges, and our efforts to validate and optimize this technique on flow phantoms with known characteristics and preliminary results on human participants.

This technique may prove to be extremely useful for the validation of complex computational fluid dynamic models. However, the current motivation for this project is to study "the glymphatic system" and its involvement in neurodegenerative disorders.

The "glymphatic" system consists of a set of pathways for the clearance of metabolites and other waste in the brain through the extravascular space. There is increasing evidence that impaired clearance of metabolite waste plays a major role in the etiology of diseases like Alzheimer's, Parkinson's and vascular dementia. Velocity Spectrum Imaging may provide a tool to characterize the microscopic convective movement of water in brain tissue without the use of invasive procedures or contrast agents.