ABSTRACT
Magnetic resonance imaging (MRI) is a well-established medical imaging modality, characterized by excellent soft-tissue contrast in morphological images. The field of MRI is developing rapidly, also in applications related to tissue function, physiology, and microstructure, including imaging of flow, perfusion, cortical activation and diffusion. Information about tissue metabolites and biochemical aspects of various disorders can be obtained by magnetic resonance (MR) spectroscopy. Furthermore, MRI is becoming increasingly common in hybrid medical system designs, both for diagnostics and therapy – for example, in combination with positron emission tomography (PET) and radiation therapy linear accelerators. Hence, the basic principles of MRI are of relevance to most medical physicists, and the main part of this chapter deals with nuclear magnetic resonance physics, MR signal generation, spin relaxation, image contrast preparation, spatial encoding, and image reconstruction. Further topics comprise common clinical imaging pulse sequences, aspects of imaging quality (including common artefacts and signal-to-noise ratio issues), advanced MRI methods, and a brief summary of MRI hardware and safety.
