Beta particles

are electrons (beta-minus) or positrons (beta-plus) that are emitted by the nucleus of a radioactive atom.

Biological half-life

is the time required for the body or an organ system to eliminate half of the dose of an administered compound.


is radiation therapy using sealed radioactive sources placed inside or on the surface of the patient. These may be intercavitary (within body cavities), interstitial (within tissues), after loaded (i.e., put in after tubes, holders, etc., to contain them are placed in the patient), high dose rate (i.e., using large amounts of radioactivity to get the maximum effect in a short time), or low dose rate.

Byproduct material

is defined under the Atomic Energy Act of 1954, 42 SC 2014 Sec. 11(e) to mean: (1) any radioactive material (except special nuclear material) produced during the process of producing or utilizing special nuclear material, and (2) the tailings or wastes produced during the extraction or concentration of uranium or thorium from any ore. This latter category is of no relevance in medicine.


is the commonly used term for any malignant neoplasm.

Chain reaction

denotes any process in which some of the reaction products become reaction raw materials. In particular, nuclear reactors consume and produce neutrons simultaneously as nuclei fission in a chain reaction.


is the treatment of disease with chemical compounds. The term is generally used in connection with the use of chemical for treatment for malignant disease.

Committed effective dose equivalent

is the sum of the products of the applicable weighting factors for each of the body organs or tissues that are irradiated multiplied by the committed dose equivalent to that area.

Computed tomography (CT),

or x-ray transmission computed tomography, is an x-ray technique in which the x-ray tube and possibly the detector are rotated around the patient; the detected signal produced by transmitted x-rays is processed by a computer to create transaxial images of x-ray attenuation in the patient. The technique enhances contrast by decreasing the contribution of scattered x-rays to the image.

Contamination, radioactive,

is the deposition of radioactive material where its presence is not desired.

Contrast agents

are pharmaceuticals used to enhance the distinction of bright and dark tones of images by changing some property in the patient. Many x-ray contrast agents contain iodine or barium, which attenuate x-rays more than the elements in the body.

Contrast of images

refers to the distinction between bright and darktones.

Cosmic rays

are radiation that originates outside the earth's atmosphere.

Curie (Ci)

is the unit of radioactivity used in the older literature; it is equal to 3.7 × 1010 disintegrations per second. The Système Internationale d'Unités

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