Estimating the Thickness of the Cerebral Cortex

PLACE:	Clark 314
EVENT:	CIS Seminar Series
DATE:	September 28, 2004
TIME:	1:00 - 2:00

Abstract

The human cerebral cortex is a laminar structure about 3 mm thick, and is easily visualized with current magnetic resonance technology. The thickness of the cortex varies locally by region, and is likely to be influenced by such factors as development, disease and aging. Thus, accurate measurements of local cortical thickness are likely to be of interest to other researchers. We develop a parametric stochastic model relating the laminar structure of the cerebral cortex to MR image data. Parameters of this model include local thickness, and statistics describing white, gray and cerebrospinal (CSF) image intensity values as a function of the normal distance from the center of a voxel to a local coordinate system anchored at the Gray/White matter interface. Our fundamental data object, the intensity-distance histogram (IDH), is a 2-dimensional generalization of the conventional 1-dimensional image intensity histogram, which indexes voxels not only by their intensity value, but also by their normal distance to the Gray/White interface. We model the IDH as a marked Poisson process with the marking process being a Gaussian random field model of image intensity indexed against normal distance. We relate the parameters of the IDH model to the local geometry of the cortex, and use a maximum-likelihood framework for estimation. We will describe estimates for cortical thickness in several brain regions, discuss Cramer-Rao bounds on these estimates, and indicate further directions for refining the model and extending these results to segmentation, estimation of surface area, and several other biologically interesting problems.

Brief biography

Patrick Barta, M.D., Ph.D. is an Associate Professor of Psychiatry and Behavioral Sciences at Johns Hopkins University School of Medicine and a member of the faculty at the Whitaker Biomedical Engineering Institute of the Johns Hopkins University. Dr. Barta is an active full-time staff member at the Johns Hopkins Hospital, and his clinical expertise is Schizophrenia and related disorders. He is also involved in creating platform-independent software for image display and measurement to be used in structural and functional brain imaging analysis. Dr. Barta has authored two programs (MEASURE and BLOX) that are currently used by PNI for image visualization and analysis. He also collaborates with researchers at the Center for Imaging Science on developing quantitative methods for segmentation, cortical surface area measurement and structure/ function integration.