The Basics of Functional Magnetic Resonance Imaging

Abstract

This chapter consists of four parts. In the first part, the basics of magnetic resonance imaging (MRI) are described, including the MR effect, the use of magnetic field gradients for spatial encoding and the relaxation times T1, T2 and T2*. After introducing k-space, the echo planar imaging (EPI) sequence, which is frequently used in functional studies, is described. Subsequently, the difference between T2*-weighted gradient echo and T2-weighted spin echo sequences is explained. The last section of this part introduces the specific absorption rate (SAR) which corresponds to the energy absorbed by tissue during an MR experiment. The second and third parts are dedicated to the cerebral blood flow (CBF) and cerebral blood volume (CBV), respectively. In each case, the respective parameter is introduced quantitatively, including typical values in brain tissue, and the most important measurement techniques are described. The last part introduces the blood oxygenation level-dependent (BOLD) effect, which is the basis of most functional studies.