Algorithm :

Computer program which modifies the raw data to alter the characteristics of the final image; e.g. bone or high spatial frequency algorithm gives high spatial resolution to the image but increases image noise, soft-tissue or low spatial frequency algorithm reduces image resolution but reduces image noise.

   Aliasing (fold-over or wrap-around) :

An artefact that occurs, as a result of the nature of the image encoding process, when the field of view (FOV) is smaller than the area being imaged. There is folding-over of the anatomy outside the FOV back into the image.

   Alphas :

An alpha is a particle emitted from the nucleus of an atom that contains two protons and two neutrons. It is identical to the nucleus of a Helium atom, without the electrons.

   Angular Frequency :

Frequency of oscillation or rotation (measured in radians/second).

   Back projection :

The computer technique used to convert the raw CT data into an image. Filtered back projection is performed, the digital filtration alters the data prior to back projection in order to optimize the image spatial resolution and noise and to reduce artefacts.

   Bandwidth :

A measure of the range of frequencies within which the MR system is tuned to receive the signal (receiver bandwidth) or the range of frequencies within an RF pulse delivered by the transmitter (transmitter bandwidth).

   Becquerel (Bq) :

The Becquerel is a unit used to measure a radioactivity. One Becquerel is that quantity of a radioactive material that will have 1 transformations in one second. Often radioactivity is expressed in larger units like: thousands (kBq), one millions (MBq) or even billions (GBq) of a becquerels. As a result of having one Becquerel being equal to one transformation per second, there are 3.7 x 1010 Bq in one curie.

   Betas :

A beta is a high speed particle, identical to an electron, that is emitted from the nucleus of an atom