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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).
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
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).
AP chest x-rays are harder to read than PA x-rays and are therefore generally reserved for situations where it is difficult for the patient to get an ordinary chest x-ray, such as when the patient is bedridden. In this situation, mobile X-ray equipment is used to obtain a lying down chest x-ray (known as a "supine film").
Natural color X-ray photogram of a wine scene. Note the edges of hollow cylinders as compared to the solid candle. William Coolidge explains medical imaging and X-rays.. An X-ray (also known in many languages as Röntgen radiation) is a form of high-energy electromagnetic radiation with a wavelength shorter than those of ultraviolet rays and longer than those of gamma rays.
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 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 ]
Using early Crookes tube X-Ray apparatus in 1896. One man is viewing his hand with a fluoroscope to optimise tube emissions, the other has his head close to the tube. No precautions are being taken. Monument to the X-ray and Radium Martyrs of All Nations erected 1936 at St. Georg hospital in Hamburg, commemorating 359 early radiology workers.