Magnetic resonance imaging and spectroscopy

Abstract

Nuclear Magnetic Resonance (NMR) was first described in the scientific literature 50 years ago when Bloch and Purcell, working independently, showed how certain nuclei placed in a magnetic field absorbed energy in the radiofrequency range and re-emitted this energy during their transition back to the relaxed state (Bloch 1946, Purcell 1946). This phenomenon has since revolutionized medical imaging with its application in Magnetic Resonance Imaging (MRI) and in vivo Magnetic Resonance Spectroscopy (MRS). MRI produces pictures of `slices' through the human body with exquisite detail and contrast without the use of radiation, while in vivo MRS provides chemical information from selected areas in a similarly non-invasive way. This article describes some of the principles involved in the two techniques.