Appendix I: Definitions

Dosimeter - A device worn by an individual that records the integrated dose from radiation. Examples of dosimeters are film badges, TLDs and direct reading pocket dosimeters.

Extremities - Hands, elbows, arms below the elbows, feet, knees and legs below the knees.

Gamma (y) radiation - Radiation energy in the form of photons, given off by processes that affect the nucleus of an atom. Gamma radiation differs from beta or alpha radiation, which are particles with measurable mass.

Internal Organs - Major internal organs such as the lung, thyroid, stomach, etc.

Lens of the Eye - The eye, as measured to a depth of 0.3 cm.

Rad - Unit of absorbed dose as used in the United States. The rad is used most commonly in radiation therapy or dosimetry. It is the measure of energy absorbed per unit mass of any material. 1 rad = 100 ergs/gram or 0.01 joules (J) per kilogram.

Radioactive materials - Any material, composed of atoms that spontaneously emit radiation. Typical radioactive materials emit a, b, g, x or neutron radiation.

Rem - Unit of dose equivalent as used in the United States. The term is used to equate the variances in human tissue, biological effect and energy transfer of radiation. Equal to absorbed dose in rads times a quality factor (QF) specific to the type and energy of radiation. For x, g and b radiation, the QF = 1, so 1 rad = 1 rem.

Roentgen - Unit of radiation exposure. This unit is used to describe the intensity of a radiation field in air, as a measure of ionization. Equal to 2.58 x 10-4 Coulombs (C) per kilogram of air at standard temperature and pressure (STP).

Thermoluminescent Dosimeter (TLD) - A device, usually a small chip of lithium or calcium fluoride, which stores energy from radiation proportional to the absorbed dose. When a TLD is heated, it gives off visible light photons that can be counted and related to dose. TLDs are commonly used as personnel dosimeters.

Whole Body, Deep Dose - The dose received by an individual to the head, trunk (including gonads), arms above the elbow or legs above the knee. The deep dose is from radiation of sufficient energy to penetrate past the skin.

Whole Body, Shallow Dose - The dose received to the skin of the whole body. In some cases, an individual may be exposed to radiation that does not penetrate any deeper than the skin (0.007 cm). When such radiation is present, the shallow dose may be higher than the deep dose. In the case that only penetrating radiation is present, the shallow dose to the skin will equal the deep dose.

X-rays - Radiation energy in the form of photons, given off by processes which affect the electrons of an atom. X-rays differ from beta or alpha radiation, which are particles with measurable mass.

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