Non-stochastic effect :

Non-stochastic effects are effects that can be related directly to the dose received. The effect is more severe with a higher dose, i.e., the burn gets worse as dose increases. It typically has a threshold, below which the effect will not occur. A skin burn from radiation is a non-stochastic effect.

   Off-centre field of view :

A field of view (FOV) that is not centred at the isocentre of the magnet.

   Paramagnetic substance :

This describes a substance (e.g. gadolinium, methaemoglobin) with positive magnetic susceptibility (opposite of diamagnetic). The substances align themselves with the static magnetic field and affect the relaxation times of tissues containing them. Gadolinium-chelate contrast agents are used for this effect, reducing the T1 relaxation times (with subsequent increase in sign) of U tissues containing them.

   Phase encoding :

This allows the localization of an MR signal by applying a series of varying phase encode gradient pulses in order to alter the phase of spins prior to signal readout. The spins themselves retain memory of the effect of the separate phase encode pulses.

   Phase-contrast angiography(Phase map) :

A 2D or 3D imaging technique relying on velocity induced phase shifts to distinguish flowing blood from stationary tissues. This technique relies on the fact that the phase gain of flowing blood is proportional to its velocity, assuming constant velocity. The magnitude image shows the vasculature with the direction of flow given by the phase image.

   Pixel :

An acronym for picture element describing the smallest component of a digital image display.

   Proton density-weighted image :

These images show contrast related to the number of mobile protons in the structure and require scanning parameters that minimize the effects of T1 (long TR) and T2 (short TE) to obtain the appropriate weighting. Images usually have T1,T2 and bulk flow contributions, however, and are thus better termed “intermediate” (between T1 and T2) weighted.

   Rad (radiation absorbed dose) :

The rad is a unit used to measure a quantity called absorbed dose. This relates to the amount of energy actually absorbed in some material, and is used for any type of radiation and any material. One rad is defined as the absorption of 100 ergs per gram of material. The unit rad can be used for any type of radiation, but it does not describe the biological effects of the different radiations.

   Radiation :

Radiation is energy in transit in the form of high speed particles and electromagnetic waves. We encounter electromagnetic waves every day. They make up our visible light, radio and television waves, ultra violet (UV), and microwaves with a large spectrum of energies. These examples of electromagnetic waves do not cause ionizations of atoms because they do not carry enough energy to separate molecules or remove electrons from atoms.