2. Magnetic Resonance Imaging in a Nutshell

Magnetic Resonance Imaging (MRI) has evolved into a versatile tool for in-vivo examination of tissue, particularly soft tissue, since its invention in the early 1970s. Unlike X-ray Computed Tomography (CT) and Positron Emission Tomography (PET), MRI relies on strong magnetic fields and radio frequency waves to create images, making it non-invasive and safe for use in healthy subjects. This chapter delves into the nuclear magnetic resonance phenomenon, the Zeeman effect, and the macroscopic magnetization vector that forms the basis of MRI. It also explores the excitation and relaxation processes, spatial localization techniques, and various MRI modalities such as functional MRI (fMRI), diffusion-weighted MRI (dMRI), and multi-parameter mapping (MPM). Special attention is given to the unique capabilities of MRI in neuroimaging, providing a fascinating glimpse into the examination of the living brain. The chapter concludes with an overview of image formation and parallel imaging techniques, highlighting the advanced methods that continue to push the boundaries of medical imaging.