Radiation biological unit

In radiation biology, the term "dose" has a specific meaning. Dose refers to the amount of radiation absorbed by the organ or tissue of interest per unit mass and is expressed in rads (grays). 

Daryl R. Myers is a Senior Scientist at NREl. In 1970 He received a Bachelor of Science in Applied Mathematics from the University of Colorado, Boulder, School of Engineering. Prior to joining NREL in 1978, he worked for four years at the Smithsonian Institution Radiation Biology Laboratory in Rockville Maryland, and is a Cold War veteran, serving as a Russian linguist in the United States Army from 1970 to 1974. He has over 32 years of experience in terrestrial broadband and spectral solar radiation physics, measurement instrumentation, metrology... 

The units used in radiation dosimetry are summarized in Table 22.1. The energy dose and the ion dose are also used in radiation chemistiy, whereas the equivalent dose is only applied in radiation biology and in the field of radiation protection. 

Rem rem A measure of the energy absorbed in matter as a result of exposure to specific forms of radiation. This unit takes into account the fact that different forms of radiation produce different biological effects. 1 rem is equal to 1 rad times a factor dependent on the type of radiation, rem = roentgen equivalent for man. 

UNSCEAR Report, Sources and Effects of Ionizing Radiation United Nations New York, 1993. Georghiou, S. Nordlund, T.M. Saim, A.M. Photochemistry and Photobiology 1985,41, 209. von Sonntag, C. The Chemical Basis of Radiation Biology Taylor and Francis New York, 1987. Hazra, D.K. Steenken, S. J. Am. Chem. Soc. 1983,105, 4380. 

Any control system that purports to respond to environmental stimuli must sense those stimuli. It may seem overly simple to realize that an environmental attribute does not really exist for that biological unit if the attribute cannot be sensed. Thus, humans cannot see ultraviolet radiation the way honey bees can, they cannot hear high frequency sound the way bats can, they cannot sense magnetic fields the way migrating birds can (birds have magnetite in their beaks to sense magnetic fields), and they are not aware of electrostatic fields as sharks are. To humans, lack of sensation... 

REM (Roentgen Equivalent Man) - Is defined as the amount of any type of ionizing radiation that produces the same damage to man as 1 roentgen of about 200kV radiation. The quantity of such biological units is named dose equivalent. 

The rem, a biological unit of radiation, is defined in Section 10.5. Source U.S. Atomic Energy Commission. 

Two methods, physical and biological, are used to describe quantities of radiation. Physical units indicate the activity of a source of radiation, typically in terms of the number of nuclei that decay per unit of time. Biological units are related to the damage caused by radiation and account for the fact that a given quantity (or number of particles) of one type of radiation does not have the same damaging effect on tissue as the same quantity of another type of radiation. 

The rem is a biological unit devised to account for health differences in various types of radiation. A 1-rad dose of ganuna radiation does not produce the same health effects as a 1-rad dose of alpha radiation. An additive unit was needed so that one unit of alpha had the same health effects as one unit of gamma. The devised unit is the rem, which stands for roentgen equivalent in man. One rem of any type of radiation has the same health effect as 1 roentgen of gamma rays or X-rays. The... 

Explain the difference between physical and biological units of radiation and give an example of each type. 

A physical unit of radiation, such as a curie, indicates the activity of a source of radiation in terms of the number of nuclear decays that occur per minute. A biological unit of radiation, such as a rem, indicates the damage caused by radiation in living tissue. 

International Commission on Radiation Units and Measurements (ICRU) http //www.icru. org/ (accessed August 26, 2010). Established in 1925, this organization has developed recommendations on (1) quantities and units of radiation and radioactivity (2) procedures suitable for the measurement and application of these quantities in diagnostic radiology, radiation therapy, radiation biology, and industrial operations and (3) physical data needed in the application of these procedures, the use of which tends to assure uniformity in reporting (from Web page). 

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