NMR Imaging

Abstract In 1946, the phenomenon of nuclear magnetic resonance (NMR) was first observed independently by Felix Bloch and Edward Purcell. NMR is a phenomenon exhibited by atoms with an odd number of protons or neutrons which possess nuclear spin angular momentum. In the classical description the phenomenon can be described as spinning charged spheres which produce a small magnetic moment. Developments in NMR over the decades that followed, including the spin echo and different RF pulse sequences, led to widespread use of NMR spectroscopy, a method of analyzing the composition of chemical samples. In 1970, Raymond Damadian discovered the basis for using NMR as a tool for in‐vivo cancer diagnosis. In 1973, Paul Lauterbur proposed the use of gradient magnetic fields for spatial encoding of NMR signals to form the first magnetic resonance images. Magnetic resonance imaging (MRI) has since developed rapidly into a widely used clinical imaging modality, and is now used to image virtually every part of the body in clinical practice. MRI has the important advantage over X‐ray imaging modalities that it does not use ionizing radiation. MRI also allows arbitrary selection of the scan plane and true three‐dimensional imaging. Unlike any other medical imaging modalities, image contrast in MRI is based on multiple physical parameters, resulting in the unique ability to generate excellent soft‐tissue contrast that can be tailored for specific applications.