NORD gratefully acknowledges Olivia Lanes, NORD Intern and David Cheng, MD, PhD, Associate Professor of Diagnostic Radiology, Yale University School of Medicine, Chief of Nuclear Medicine, Medical Director of Yale University PET Center, for assistance in the preparation of this report.
SummaryRadiation sickness describes the harmful effects--acute, delayed, or chronic--produced by exposure to ionizing radiation. An observable effect due to radiation exposure becomes quite certain after a single dose of several hundred rads. As a rule, large doses of radiation are of concern because of their immediate effects on the body (somatic), while low doses are of concern because of the potential for possible late somatic and long-term genetic effects. The effects of radiation exposure on an individual are cumulative. Although there is currently no treatment to repair cells that have already been damaged by radiation, the FDA has recently approved drugs that are very effective at removing radioactive elements from the body. Because the damage is irreversible, patients exposed to radiation that are experiencing symptoms should seek medical help immediately so that drugs can be administered.
IntroductionThe first observable cases of radiation sickness occurred after the nuclear bombing of Hiroshima and Nagasaki. Japanese doctors described an unknown disease with symptoms that "suddenly appeared in certain patients with no apparent injuries." It is now known that these first patients were suffering delayed effects of radiation exposure. Radiation sickness can result in patients with low exposure levels, such as cancer treatments, and leave them with symptoms similar to a case of the flu. However, in cases of extreme exposure caused from atomic weapons or a power plant meltdown, such as Chernobyl, the effects can be fatal. Total dose and dose rate determine somatic or genetic effects of radiation. The units of measurement commonly used in determining radiation exposure or dose are the roentgen, the rad, and the rem. The roentgen (R) is a measure of quantity of x or gamma ionizing radiation in air. The radiation absorbed dose (rad) is the amount of energy absorbed in any substance from exposure, and applies to all types of radiation. The R and the rad are nearly equivalent in energy for practical purposes. The rem is used to correct for the observation that some types of radiation, such as neutrons, may produce more biological effect for an equivalent amount of absorbed energy; thus the rem is equal to the rad multiplied by a constant called the "quality factor". For x and gamma radiation the rem is equal to the rad. The rad and the rem are currently being replaced in the scientific nomenclature by two units that are compatible with the International System of Units, namely the gray (Gy), equal to 100 rads and the Sievert (Sv), equal to 100 rem.
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