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The roentgen or röntgen (/ ˈ r ɛ n t ɡ ə n,-dʒ ə n, ˈ r ʌ n t-/; [2] symbol R) is a legacy unit of measurement for the exposure of X-rays and gamma rays, and is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air (statcoulomb per kilogram).
It is the absorbed energetic dose before the biological efficiency of the radiation is factored in. The rep has variously been defined as 83 or 93 ergs per gram of tissue (8.3/9.3 mGy) [2] or per cm 3 of tissue. [3] At the time, this was thought to be the amount of energy deposited by 1 roentgen. [4]
For comparison, radiation levels inside the United States Capitol are 85 mrem/yr (0.85 mSv/yr), close to the regulatory limit, because of the uranium content of the granite structure. [14] The NRC sets the annual total effective dose of full body radiation, or total body radiation (TBR), allowed for radiation workers 5,000 mrem (5 rem). [15] [16]
Dose area product (DAP) is a quantity used in assessing the radiation risk from diagnostic X-ray radiography examinations and interventional procedures, like angiography.It is defined as the absorbed dose multiplied by the area irradiated, expressed in gray-centimetres squared (Gy·cm 2 [1] – sometimes the prefixed units dGy·cm 2, mGy·cm 2 or cGy·cm 2 are also used). [2]
Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning.Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1,000 of a rem and 1 rem equals 0.01 Sv.
The effects of the 1979 Three Mile Island nuclear accident are widely agreed to be very low by scientists in the relevant fields. The American Nuclear Society concluded that average local radiation exposure was equivalent to a chest X-ray and maximum local exposure equivalent to less than a year's background radiation. [1]
Marijuana plants for the adult recreational market are are seen in a greenhouse at Hepworth Farms in Milton, N.Y., July 15, 2022. New York has issued the first 36 cannabis dispensary licenses on ...
0.7 mSv [9] 175 flight-hours Public dose limit: limit: 1 mSv [15] 250 flight-hours Lumbar spine x-ray: singular: 1.5 mSv [9] 375 flight-hours Background radiation in Toronto, CA: annual: 1.6 mSv [5] 400 flight-hours Brain CT scan: singular: 2 mSv [9] 500 flight-hours Background radiation - worldwide average: annual: 2.4 mSv [5] 600 flight-hours ...