(TLD) A thermoluminescent dosimeter contains a crystalline material (lithium fluoride, phosphor) for measuring radiation dose. TLDs are usually small crystals measuring 3 mm square by 1 mm thickness. Additional filters (absorbers) help to characterize the types of the impinging radiation. When heated, TLD crystals that have been exposed to ionizing radiation give off light proportional to the received energy.

A densitometer (also called absorptiometer) is used to measure the density of a film by the amount of light which shines through; or tissue density (e.g., bone, lung) by the amount of radiation transmission. The logarithm of the reciprocal of the transmittance is called the absorbance or density.

A gamma quantum is a distinct photon of electromagnetic radiation with the highest energy, shortest wavelength. The energy of a single photon is above 100 keV, the wavelength is below about 10 picometers. Gamma photons are generated by processes within the atomic nuclei.

See also Quantum.

The calibration factor helps to convert between the measured value of a parameter and the actual value of that parameter in a system.
This normalization is necessary in cases where detectors and sensors do not directly sample a parameter, for example the radiation energy is measured by a detector that produces an electrical pulse whose total charge is proportional to the supplied radiation.

The deep dose equivalent is related to the dose in tissue at a depth of one centimeter due to external radiation. Also called personnel dose equivalent at a depth of 1 cm. The unit for deep dose equivalent is J/kg or sievert (Sv).