It should be emphasized that this presentation is intended to be instructional and is subject to the limitations of present available knowledge. Attempts have been made to quote authorities, but there is no intention to submit this as a handbook or authoritative guide.
Radiation Units and Equivalents*
—The exposure (x-rays or γ-rays) causing in 1 cc. of air, under standard conditions, production of positive and negative ions, either kind of them having altogether the charge of one electrostatic unit. The roentgen is a purely physical unit and has no direct relation to absorption or biological effect of radiation.
Roentgen Equivalent Physical (rep).
—Obsolete. Exposures of any kind of radiation resulting in ionization equivalent to 83 ergs per gram of air or 93 ergs per gram of tissue.
Radiation Absorbed Dose (rad).
—The radiation energy absorbed by a small volume of tissue divided by this volume. Its unit is
PETERSON RE, BARON JG, KENT BM, EVANS TC. Reviews of Internal MedicineA Primer on Radiation Hazards for Physicians. AMA Arch Intern Med. 1959;103(2):308–328. doi:10.1001/archinte.1959.00270020136015
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