Magnetic Susceptibility Anisotropy of Central Nervous System

INTRODUCTION : Magnetic susceptibility difference between brain gray and white matter results in strong phase contrast between these two types of tissues at high magnetic field strength (1, 2). Here, we report, for the first time, a surprising observation of tissue-level magnetic susceptibility anisotropy in the central nervous system (CNS) using a mouse model. Specifically, we propose a method for calculating intrinsic susceptibility maps by solving three complementary equations. This method removes a common streaking artifact. More importantly, we found that susceptibility of the white matter exhibits strong orientation dependence. Such orientation variation is extensive throughout the white matter area, but is relatively weak in the gray matter. We anticipate that imaging this anisotropy will provide a unique tissue contrast that is unknown previously. In addition, it will provide a novel tool to further quantify the substructures of the central nervous system.