Charged particles (ions) range from lighter electrons and positrons to heavier alpha particle and other not neutral nuclei. The charge is measured in coulomb.

A display is a computer monitor that shows the processed data from the scanned area. Displays can be black-and-white or color, small or large depending upon the model and price of the machine.

See also Display Field of View, Display Matrix, Window Width, Bit Range, Hounsfield Scale, Interpolation, Minimum Intensity Projection, and Printer.

A distributed source is a one dimensional area or volume source compared to the dimensions of the detector and which may produce a radiation beam over a wide range of angles of incidence on the measurement area.

Epithermal neutrons are unbound moderately severe neutrons. The energy of epithermal neutrons is in the range from 0.025 to 1 eV. Unbound neutrons are produced in fission and in some radioactive decay processes.

See also Neutron Activation Analysis, Neutron Capture.

X-rays contain a range of energies (polychromatic photons), the higher energies pass through the patient, the lower energies are absorbed or scattered by the body. Ideally, the x-ray beam should be monochromatic or composed of photons having the same energy. Strong filtration of the beam results in more uniformity. The more uniform the beam, the more accurate the attenuation values or CT numbers are for the scanned anatomical region.
There are two types of filtration utilized in CT:
Inherent tube filtration and filters made of aluminum or Teflon are utilized to shape the beam intensity by filtering out the undesirable x-rays with low energy. Filtration of the x-ray beam is usually done by the manufacturer prior to installation. The half value layer provides information about the energy characteristics of the x-ray beam. Too much filtration produces a loss of contrast in the x-ray image.
A mathematical filter such as a bone or soft tissue algorithm is included into the CT reconstruction process to enhance resolution of a particular anatomical region of interest.