In medical imaging, resolution is the ability to distinguish two adjacent objects and a measurement of image quality. The resolution of tomographic images is a function of slice thickness, field of view (FOV) and matrix size. The resolution in plane is a function of FOV / matrix size.

Transition is the nuclear change from one energy state to another, generally accompanied by the emission of particles or photons.

See Decay.

The attenuation of radiation is a decrease in intensity as a result of interactions by transmission through matter. X-ray beams attenuate due to photon absorption by the material or scattering. Both effects are energy dependent. The probability of absorption or scattering is a function of the photon energy. The photoelectric absorption is much more energy dependent than the Compton scatter effect.

See also Attenuation Correction, Linear Energy Transfer, Broad Beam and Ion Beam.

A calibration is a correction procedure that determines the relationship between the measured output of a system and the reference standard. Calibration procedures include scanning air or an appropriate test phantom.
The calibration of a CT system takes account of variations in beam intensity or detector efficiency in order to achieve best homogeneity within the field of view and the accuracy of CT numbers.

See also Calibration Factor and Acceptance Checking.

The (spot) compression of for example breast tissue, allows for greater reduction in thickness of the area of interest and improved separation of breast tissues by the use of a small compression device.
Compression can be also a software or hardware process that shrinks images to lessen the storage space. Compression is generally accomplished by removing the bits that define redundant like data blank spaces, and replacing them with a smaller symbolic code that represents the removed or redundant bits.