Magnetic resonance signal :

The electromagnetic signal produced by the precession of the transverse magnetization of the spins. The rotation of the transverse magnetization induces a voltage in the receiver coil. It is this voltage that is amplified by the receiver and forms the signal.

   Magnetic susceptibility :

The ability of a substance to become magnetized or to distort a magnetic field. This is described in terms of diamagnetic, paramagnetic, superparamagnetic and ferromagnetic materials and refers to their respective electronic magnetic moments.

   Magnetization transfer contrast (MTC) :

This is a relatively new technique in which the image contrast is manipulated by selectively saturating a pool of protein-bound water. It should be noted that protons in the protein-hound water have a resonant frequency, approximately 500-2500 Hz away from the bulk water protons. By applying an off-resonance pulse (i.e. the centre frequency of the pulse being 1000-2000 Hz removed from the Larmor frequency for protons together with a wide bandwidth) these protons are suppressed. Because the protein-bound water and the bulk water protons are in rapid exchange, the saturation is transferred to the bulk phase of the water protons. This leads to a reduction in the signal from bulk water. MTC is used in the following situations: (1) In MRA of the brain as a means of enhancing visualization of small peripheral vessels and aneurysms by suppressing the background brain tissue; (2) In conjunction with gadolinium chelate enhancement, making the enhanced areas more conspicuous; (3) Combined with T2-weighted images in the detection of early demyelination or protein destruction.

   Maximum intensity projection (MIP) :

An algorithm for producing multiple projections from a 2D or 3D volume data set. This volume data set is processed along selected angles in which the highest signal intensity pixel is projected as a 2D image. This technique is used in magnetic resonance angiography (MRA), whereby flowing blood has high signal intensity, and in MR cholangiopancreatography (MRCP) in which bile is of high signal.

   MRI Artefact :

An error that occurs in the reconstructed image which does not correspond to any anatomical region or pathological lesion within the patient.

   Multislice CT :

CT scanner in which the detector bank is split into several adjacent rows so that the data acquisition from a single gantry rotation can be used to produce multiple adjacent thin slices from a beam collimated to one thicker section.

   Neutrons :

Neutrons are neutral particles that are normally contained in the nucleus of all atoms and may be removed by various interactions.

   Non-ionizing radiation :

Non-ionizing radiation is radiation without enough energy to remove tightly bound electrons from their orbits around atoms. Examples are microwaves and visible light.