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Number of chest X-rays resulting in same effective dose Skull radiography (X-ray) 0.015 1 Chest X-ray 0.013 1 Lumbar spine X-ray 0.44 30 Abdomen X-ray 0.46 35 Pelvis X-ray 0.48 35 Screening mammography (4 views) 0.2 15 Dental X-ray (intraoral) 0.013 1 Diagnostic fluoroscopy: barium swallow 1 70 Cardiac angiography 7 500 Head CT 2 150 Chest CT 10
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).
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.
In diagnostic radiology, the F-factor is the conversion factor between exposure to ionizing radiation and the absorbed dose from that radiation. In other words, it converts between the amount of ionization in air (roentgens or, in SI units, coulombs per kilogram of absorber material) and the absorbed dose in air (rads or grays).
Elihu Thomson deliberately exposed a finger to an x-ray tube over a period of time and experienced pain, swelling, and blistering. [31] Other effects, including ultraviolet rays and ozone were sometimes blamed for the damage. [32] Many physicists claimed that there were no effects from x-ray exposure at all. [31]
In the 1930s the roentgen was the most commonly used unit of radiation exposure. This unit is obsolete and no longer clearly defined. This unit is obsolete and no longer clearly defined. One roentgen deposits 0.877 rad in dry air, 0.96 rad in soft tissue, [ 9 ] or anywhere from 1 to more than 4 rad in bone depending on the beam energy. [ 10 ]
At the first ICRU meeting it was proposed that one unit of X-ray dose should be defined as the quantity of X-rays that would produce one esu of charge in one cubic centimetre of dry air at 0 °C and 1 standard atmosphere of pressure. This unit of radiation exposure was named the roentgen in honour of Wilhelm Röntgen, who had died five years ...
The definition was refined in 1950 as "that dose of any ionizing radiation which produces a relevant biological effect equal to that produced by one roentgen of high-voltage x-radiation." [ 19 ] Using data available at the time, the rem was variously evaluated as 83, 93, or 95 erg /gram. [ 20 ]