What is Magnetic Resonance?

Nuclear Magnetic Resonance (NMR) a phenomenon exhibited by the nucleus and electrons of many elements. The discovery of nuclear magnetic resonance in 1945 was accredited to Bloch and Purcell, for which they were awarded the Nobel prize. The development of magnetic resonance technology has had a profound impact upon many areas of science, a fact recognized by the award of no fewer than seven Nobel prizes to pioneers of applications of magnetic resonance in chemistry, biochemistry and medicine. Magnetic resonance is used to determine molecular structures of a wide range of materials, from organic compounds and synthetic polymers to biologically important molecules such as proteins, enzymes and nucleic acids in solution and in the solid state. MR imaging maps the distribution of water within the subject and produces exquisite anatomical images of the human body as well as other subjects such as plants, animals and materials. MRI has revolutionized diagnostic radiology and is a major research tool for studying the structure and function of living systems. There are more than 20,000 MRI scanners installed in hospitals throughout the world.

How does MR work?

Electrons and the nucleus of many elemental isotopes, such as hydrogen, possess a property known as spin. These charged spinning atomic particles behave like small magnets and in the presence of a magnetic field will align themselves either with or against the direction of this applied magnetic field. Typically, the magnets used have fields hundreds of thousands times stronger than the earth's magnetic field. If energy is applied to the sample, usually in the form of radiofrequency waves, these small magnets rotate out of alignment and begin to spin, or precess, about the direction of the applied field. Just as a spinning magnet generates current in a coil of wire in an electric motor, the precessing spins induce a signal in a detector coil. A similar phenomenon, known as Electron Paramagnetic Resonance (EPR), discovered in 1944, is observed for molecules containing one or more unpaired electrons. This signal contains highly valuable information about the spatial and chemical environment of the atom. This information can be used to determine the molecular structure of the sample, identify unknown components, analyze chemical mixtures, learn about the physical properties of materials such as polymers, study the structure, function and interactions of biological molecules and drugs, and produce visual images for medical diagnosis and structural analysis.

To learn more about the principles and applications of magnetic resonance, the links below are an excellent starting point.

MR imaging

NMR spectroscopy

NMR spectroscopy basic principles

EPR basic principles

NMR spectroscopy in chemistry

NMR information server

Applications of Magnetic Resonance

High Resolution NMR

High resolution NMR spectroscopy is an extremely powerful tool for chemical analysis and molecular structure determination. Unique information about physical structure, solution chemistry and molecular dynamics can be obtained.

Solid-State NMR

Solid-state NMR spectroscopy permits the characterisation of insoluble materials, such as crosslinked polymers, coals, minerals and ceramics. A wealth of information can be obtained, including connectivity of chemical structures, domain sizes in heterogenous materials, mechanisms of mechanical relaxation in materials, orientation of chemical groups and conformation of chains.

Electron Paramagnetic Resonance (EPR)

Electron paramagnetic resonance (EPR) and electron spin resonance (ESR) are synonymous terms for describing the resonant absorption of microwave radiation bya paramagnetic substance in a static magnetic field.

Multifrequency EPR spectroscopy is a powerful tool for characterising paramagnetic molecules or centres within molecules which contain one or more unpaired electrons. Examples include free radicals, transition metal ions and multiatom clusters found in such diverse areas as physics, materials science (high TC superconductors, organic molecular ferromagnetics and catalysts), chemistry (inorganic, organic and polymeric compounds), biochemistry (metalloproteins and free radical chemistry), food science, radiation dosimetry and medicine (diseases associated with the mitochondrial electron transfer chain, free radical damage, and irradiation). An integral component in elucidating structural information from complex EPR spectra is the determination of spin Hamiltonian parameters. Towards this end, a general purpose computer simulation software suite named Xsophe has been developed.

NMR Imaging and Localised Spectroscopy

Magnetic Resonance Imaging (MRI) is an ideal tool for studying live subjects because radio waves and magnetic fields are relatively safe for biological tissue. The Centre has facilities for imaging small animals in vivo, without harming the animal. Information can be obtained about the anatomy and condition of major organs including the brain, liver, kidney and spinal cord. The Centre also has instruments dedicated to MR microimaging which are used for high resolution imaging of a wide variety of samples.