MR SCANNER

Typical Number in Hospital: 1

Cost Bands: 8

References:

Previously known as a nuclear magnetic resonance (NMR) scanner, the word 'nuclear' has been dropped to avoid confusion with devices producing harmful radiations. This can produce images of selected planes within the body which are similar in general appearance to CT scans, but the image relates to the state and content of water at each point within the scan plane.

The technique has the potential to identify other aspects of the chemical structure of tissues but at present medical imaging is limited to information derived from the spin resonance of the hydrogen nucleus. The hydrogen nucleus forms a small magnet which will absorb and emit radio-frequency energy at a resonant frequency depending on the strength of an applied magnetic field. By the application of a magnetic field gradient the resonant frequency will depend on position in the field. An extension of this principle allows the construction of 2- and 3-dimensional images.

The scanners currently available have solved the various construction problems (particularly those of the large magnets required) in various ways, but it will probably be some years before MR imaging facilities are generally available, partly because of the high capital and operating costs. A major advantage of an MR scanner is that there are no (known) harmful effects.