roentgen
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roent·gen
also rönt·gen (rĕnt'gən, -jən, rŭnt'-) 
n. (Abbr. R or r)
A unit of radiation exposure equal to the quantity of ionizing radiation that will produce one electrostatic unit of electricity in one cubic centimeter of dry air at 0°C and standard atmospheric pressure.
n. (Abbr. R or r)
A unit of radiation exposure equal to the quantity of ionizing radiation that will produce one electrostatic unit of electricity in one cubic centimeter of dry air at 0°C and standard atmospheric pressure.
[After Wilhelm Konrad ROENTGEN.]
roentgen roent'gen adj.Oxford Dictionary of Chemistry:
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roentgen
The former unit of dose equivalent (see radiation units). It is named after the discoverer of X-rays, W. K. Roentgen (1845–1923).
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[Etymology: W. K. Röntgen; Germany 1845-1923] radiation physics Symbol R, röntgen. An obsolescent unit of ionizing electromagnetic radiation, being the quantity of x-rays or gamma rays that, through ionization, produces 2.58 × 10-4 coulombs of electricity per kilogram of dry air at s.t.p.
The roentgen was originated relative only to x-rays, being agreed in 1928 as the amount that would produce 1 electrostatic unit of electric charge from 1 cubic centimetre of standard dry air. In 1937, for practical reasons, mass replaced volume for the reference amount of air, making the amount 1.293~ mg of air. The 1978 decision of the CIPM considering it acceptable to continue to use the roentgen with the SI still stands.
Such ionization displaces electrons from individual atoms to produce negatively charged free electrons and matching positively charged ions; 1 roentgen produces 1.61~ × 1015 of each per kilogram. The energy required for such displacing is 8.69~ mJ·kg-1 or 11.2~ mJ·m-3.
Using this energy figure of 8.69~ mJ·kg-1, the roentgen was extended to apply to materials other than air, and to the particulate radiation of alpha and beta rays. In this extended form it was called the tissue roentgen or, much more usually, the roentgen equivalent physical, abbreviated to and universally called the rep. However, the roentgen itself was often so used; until 1956 it was used in a radiological context not only as a measure of exposure (which it correctly is) but also as a measure of absorbed dose; the rad took over the latter role.
Until 1952 the British authorities used a version about 8% less.
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[ܒrentgǝn; ܒrǝnt-; -jǝn]
See the Introduction, Abbreviations and Pronunciation for further details.
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(DOD, NATO) A unit of exposure dose of gamma (or X-) radiation. In field dosimetry, one roentgen is essentially equal to one rad.
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Rontgen
IN BRIEF: n. - German physicist who discovered x-rays and developed x-ray photography (1845-1923).
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or roentgen
symbol R; the unit of exposure (def. 3) to X- or gamma radiation, expressed in terms of the amount of ionization caused in air. Defined originally (1928, 1937) as that quantity of radiation having a corpuscular emission per 0.001293 gram of air (equivalent of 1 cm3 of dry air at stp) producing, in air, ions carrying one electrostatic unit quantity of electricity of either sign. Expressed in SI units, 1 R causes the production in air of ions (of one sign) carrying a charge of 2.58 × 104 C kg−1; this corresponds to the formation of 1.61 × 1015 ion-pairs per kg of air and to an absorption of energy by air equal to 0.00869 J kg−1. The energy absorption by water or tissue from 1 R of x- or gamma-radiation is about 0.0096 J kg−1. Prior to 1956, the röntgen was used in clinical work to express both exposure and absorbed dose. See also rad (def. 2), rem, rep. [After Wilhelm Konrad von Röntgen (1845 — 1923), German physicist, discoverer of X-rays.]
symbol R; the unit of exposure (def. 3) to X- or gamma radiation, expressed in terms of the amount of ionization caused in air. Defined originally (1928, 1937) as that quantity of radiation having a corpuscular emission per 0.001293 gram of air (equivalent of 1 cm3 of dry air at stp) producing, in air, ions carrying one electrostatic unit quantity of electricity of either sign. Expressed in SI units, 1 R causes the production in air of ions (of one sign) carrying a charge of 2.58 × 104 C kg−1; this corresponds to the formation of 1.61 × 1015 ion-pairs per kg of air and to an absorption of energy by air equal to 0.00869 J kg−1. The energy absorption by water or tissue from 1 R of x- or gamma-radiation is about 0.0096 J kg−1. Prior to 1956, the röntgen was used in clinical work to express both exposure and absorbed dose. See also rad (def. 2), rem, rep. [After Wilhelm Konrad von Röntgen (1845 — 1923), German physicist, discoverer of X-rays.]
| ryanodine receptor, ryanodine, rutinose | |
| röntgen rays, s, s |
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roentgen
A superseded international unit of x- or γ-radiation; it is the quantity of x- or γ-radiation such that the associated corpuscular emission per 0.001293 g of air produces, in air, ions carrying 1 electrostatic unit of electrical charge of either sign. Abbreviated R. Now replaced by coulomb/kg (C/kg); see coulomb. 1 R = 2.58 × 10−4 C/kg; 1 C/kg = 3876 R.
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roentgen ray
(rent′gən)
n
r
n
r
An international unit based on the ability of radiation to ionize air. The exposure to x or gamma radiation such that the associated corpuscular emission per 0.001293 Gm of air produces, in air, ions carrying 1 esu of quantity of electricity of either sign (2.083 billion ion pairs).
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categories related to 'roentgen'
- Nuclear and Particle Physics - roentgen: standard unit that measures ionizing radiation from X-rays or gamma rays
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Roentgen (unit)
- Not to be confused with roentgen equivalent man or roentgen equivalent physical
The roentgen (R, also röntgen) is an obsolete unit of measurement for the kerma of X-rays and gamma rays up to 3 MeV. It is named after the German physicist Wilhelm Röntgen, the man who discovered X-rays. Originating in 1908, this unit has been redefined and renamed over the years.[1] It was last defined by the US National Institute of Standards and Technology (NIST) in 1998 as 2.58×10−4 C/kg, (1 C/kg = 3876 R,) with a recommendation that the definition be given in every document where the roentgen is used.[2] One roentgen of air kerma deposits 0.00877 gray (0.877 rad) of absorbed dose in dry air, or 0.0096 gray (0.96 rad) in soft tissue.[3] One roentgen (air kerma) of X-rays may deposit anywhere from 0.01 to more than 0.04 gray (1 to 4 rad) in bone depending on the beam energy.[4] This tissue-dependent conversion from roentgen to rad is called the F-factor in radiotherapy contexts. The conversion depends on the ionizing energy of a standard medium, which is ambiguous in the latest NIST definition. Even where the standard medium is fully defined, the ionizing energy of the calibration and target mediums are often not precisely known.
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History
The roentgen has its roots in the Villard unit defined in 1908 by the American Roentgen Ray Society as "the quantity of radiation which liberates by ionisation one esu of electricity per cm3 of air under normal conditions of temperature and pressure."[1] Using 1 esu ≈ 3.33564×10−10 C and the air density of ~1.293 kg/m³ at 0°C and 101kPa , this converts to 2.58×10−4 C/kg, which is the modern value given by NIST. This definition was used under different names (e, R, and German unit of radiation) for the next 20 years. In the meantime, the French Roentgen was given a completely different definition which amounted to 0.444 German R.
ICR definitions
In 1928, the International Congress of Radiology (ICR) defined the roentgen as "the quantity of X-radiation which, when the secondary electrons are fully utilised and the wall effect of the chamber is avoided, produce in 1 cc of atmospheric air at 0°C and 76cm of mercury pressure such a degree of conductivity that 1 esu of charge is measured at saturation current." [1] The stated 1 cc of air would have a mass of 1.293 mg at the conditions given, so in 1937 the ICR rewrote this definition in terms of this mass of air instead of volume, temperature and pressure.[5] The 1937 definition was also extended to gamma rays, but later capped at 3 MeV in 1950.
GOST definition
The USSR all-union committee of standards (GOST) had meanwhile adopted a significantly different definition of the roentgen in 1934. GOST standard 7623 defined it as "the physical dose of X-rays which produces charges each of one electrostatic unit in magnitude per cm3 of irradiated volume in air at 0°C and normal atmospheric pressure when ionization is complete."[6] The distinction of physical dose from dose caused confusion, some of which may have led Cantrill and Parker report that the roentgen had become shorthand for 83 ergs per gram (0.0083 Gy) of tissue.[7] They named this derivative quantity the roentgen equivalent physical (rep) to distinguish it from the IRC roentgen.
ICRP definition
Towards the middle of the twentieth century, roentgens were used for the purpose of radiation protection. This replaced earlier practices that relied on time, film exposure, or fluorescence. The National Council on Radiation Protection established the first formal dose limit in 1931 as 0.1 roentgen per day.[8] The International X-ray and Radium Protection Committee, now known as the International Commission on Radiological Protection (ICRP) soon followed with a limit of 0.2 roentgen per day in 1934.[9] In 1950, the ICRP reduced their recommended limit to 0.5 roentgen per week for whole-body exposure. The International Commission on Radiation Units and Measurements (ICRU) took over the definition of the roentgen in 1953, defining it as "the quantity of X or γ-radiation such that the associated corpuscular emission per 0.001293 gram of air produces, in air, ions carrying 1 electrostatic unit of quantity of electricity of either sign."[10] The 3 MeV cap was no longer part of the definition, but the degraded usefulness of this unit at high beam energies was mentioned in the accompanying text. In the meantime, the new concept of roentgen equivalent man (rem) had been developped. Starting in 1957, the ICRP began to publish their recommendations in terms of rem, and the roentgen fell into disuse. The medical imaging community still has a need for ionization measurements, but they gradually converted to using C/kg as legacy equipment was replaced.[11] The ICRU recommended redefining the roentgen to be exactly 2.58 X 10-4 C/kg in 1971.[12]
European Union
In 1971 the European Economic Community, in Directive 71/354/EEC, catalogued the units of measure that could be used "for ... public health ... purposes".[13] The directive included the curie, rad, rem and roentgen as permissible units, but required that the use of the rad, rem and roentgen be reviewed before 31 December 1977. This document defined the roentgen as exactly 2.58X10-4 C/kg, as per the ICRU recommendation. Directive 80/181/EEC, published in December 1979, which replaced directive 71/354/EEC, explicitly catalogued the gray, becquerel and sievert for this purpose and required that the curie, rad, rem and roentgen be phased out by 31 December 1985.[14]
NIST definition
Today the roentgen is rarely used, and the International Committee for Weights and Measures (CIPM) never accepted the use of the roentgen. From 1977 to 1998, the US NIST's translations of the SI brochure stated that the CIPM temporarily accepted the use of the roentgen (and other radiology units) with SI units since 1969.[15] However, the only related CIPM decisions shown in the appendix are with regards to the curie in 1964 and the radian (symbol: rad) in 1960. The NIST brochures defined the roentgen as 2.58X10-4 C/kg, to be employed with exposures of x or γ radiation, but did not state the medium to be ionized. The CIPM's current SI brochure excludes the roentgen from the tables of non-SI units accepted for use with the SI.[16] The US NIST clarified in 1998 that it was providing its own interpretations of the SI system, whereby it accepted the roentgen for use in the US with the SI, while recognizing that the CIPM did not.[17] By then, the limitation to x and γ radiation had been dropped. NIST recommends defining the roentgen in every document where this unit is used.[2] The continued use of the roentgen is strongly discouraged by the NIST.[18]
Significance
An exposure of 500 roentgens in five hours is usually lethal for human beings.
The typical exposure to normal background radiation for a human being is about 200 milliroentgens per year, or about 23 microroentgens per hour.
When measuring dose absorbed in man due to exposure, units of absorbed dose are used (the related rad or SI gray), or, with consideration of biological effects from differing radiation types, units of equivalent dose, such as the related rem or the SI sievert.
See also
- Wilhelm Conrad Röntgen
- Rad (unit) — c.g.s. unit of absorbed dose
- Gray (unit) — SI unit of absorbed dose
- Roentgen equivalent man, or rem, a unit of radiation dose equivalent
- Sievert — The sievert (symbol: Sv) is the SI derived unit of dose equivalent.
- Microdose
- Orders of magnitude (radiation)
References
- ^ a b c Van Loon, R.; and Van Tiggelen, R., Radiation Dosimetry in Medical Exposure: A Short Historical Overview, 2004>
- ^ a b Hebner, Robert E. (1998-07-28). "Metric System of Measurement: Interpretation of the International System of Units for the United States". Federal Register (US Office of the Federal Register) 63 (144): p. 40339. http://www.gpo.gov/fdsys/pkg/FR-1998-07-28/pdf/98-16965.pdf. Retrieved 9 May 2012.
- ^ "APPENDIX E: Roentgens, RADs, REMs, and other Units". Princeton University Radiation Safety Guide. Princeton University. http://web.princeton.edu/sites/ehs/radsafeguide/rsg_app_e.htm. Retrieved 10 May 2012.
- ^ Sprawls, Perry. "Radiation Quantities and Units". The Physical Principles of Medical Imaging, 2nd Ed. http://www.sprawls.org/ppmi2/RADQU/3RADQU08.gif. Retrieved 10 May 2012.
- ^ Guill, JH; Moteff, John (June 1960). "Dosimetry in Europe and the USSR". Symposium on Radiation Effects and Dosimetry. Baltimore: ASTM International. p. 64. LCCN 60-14734. http://books.google.com/books?id=czTi4G6-Hq8C&pg=PA63. Retrieved 15 May 2012.
- ^ Ardashnikov, S. N.; and Chetverikov, N. S. (1957). "The definition of the roentgen in the “Recommendations of the International Commission on Radiological Units. 1953”". Atomic Energy 3 (3): 1027-1032. doi:10.1007/BF01515739.
- ^ Cantrill, S.T; H.M. Parker (1945-1-5). The Tolerance Dose. Argonne National Laboratory: US Atomic Energy Commission. http://oai.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA322447. Retrieved 14 May 2012.
- ^ Meinhold, Charles B. (April 1996). One Hundred Years of X Rays and Radioactivity -- Radiation Protection: Then and Now. International Congress. Vienna, Austria: International Radiation Protection Association. http://www.irpa.net/irpa9/cdrom/VOL.1/V1_2.PDF. Retrieved 14 May 2012.
- ^ Clarke, R.H.; and J. Valentin (2009). "The History of ICRP and the Evolution of its Policies". Annals of the ICRP. ICRP Publication 109 39 (1): pp. 75-110. doi:10.1016/j.icrp.2009.07.009. http://www.icrp.org/docs/The%20History%20of%20ICRP%20and%20the%20Evolution%20of%20its%20Policies.pdf. Retrieved 12 May 2012.
- ^ Oosterkamp, W. J. (1954). "General considerations regarding the dosimetry of roentgen and gamma radiation addendum". Applied Scientific Research, Section B 3 (1): 477-478. doi:10.1007/BF02919922.
- ^ Carlton, Richard R.; Adler, Arlene McKenna (1 January 2012). "Radiation Protection Concepts and Equipment". Principles of Radiographic Imaging: An Art and a Science (5th ed.). Cengage Learning. p. 145. ISBN 978-1-4390-5872-5. http://books.google.com/books?id=5mbrJ43Oo7IC&pg=PA145. Retrieved 12 May 2012.
- ^ ICRU Report 19, 1971
- ^ "Council Directive 71/354/EEC: On the approximation of the laws of the Member States relating to units of measurement". The Council of the European Communities. 18 October 1971. http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=DD:I:1971_III:31971L0354:EN:PDF. Retrieved 19 May 2012.
- ^ The Council of the European Communities (1979-12-21). "Council Directive 80/181/EEC of 20 December 1979 on the approximation of the laws of the Member States relating to Unit of measurement and on the repeal of Directive 71/354/EEC". http://eur-lex.europa.eu/LexUriServ/LexUriServ.do?uri=CELEX:31980L0181:EN:NOT. Retrieved 19 May 2012.
- ^ International Bureau of Weights and Measures (1977). United States National Bureau of Standards. ed. The international system of units (SI). NBS Special Publication 330. Dept. of Commerce, National Bureau of Standards. http://books.google.com/books?id=YvZNdSdeCnEC&pg=PA12. Retrieved 18 May 2012.
- ^ International Bureau of Weights and Measures (2006), The International System of Units (SI) (8th ed.), ISBN 92-822-2213-6, http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf
- ^ Lyons, John W. (1990-12-20). "Metric System of Measurement: Interpretation of the International System of Units for the United States". Federal Register (US Office of the Federal Register) 55 (245): pp. 52242-52245.
- ^ Taylor, BN, "Units temporarily accepted for use with the SI", NIST Guide for the Use of the International System of Units (SI), chapter 5, Physics Laboratory Publications, April 1995, retrieved and archived [1] 12th June 2008
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Translations:
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Roentgen
idioms:
- roentgen rays røntgenstråler
Français (French)
n. - Röntgen
idioms:
- roentgen rays rayons Röntgen
idioms:
- roentgen rays Röntgenstrahlen
Ελληνική (Greek)
n. - ακτίνες Χ, ακτίνες Ραίντγκεν
idioms:
- roentgen rays ακτίνες Ραίντγκεν
- roentgen rays raggi X
Português (Portuguese)
idioms:
- roentgen rays raio x
idioms:
- roentgen rays рентгеновские лучи
Español (Spanish)
n. - rayos roentgen
idioms:
- roentgen rays rayos X
Svenska (Swedish)
n. - (fys) Röntgen (enhet)
中文（简体）(Chinese (Simplified))
伦琴
idioms:
- roentgen rays X光射线
中文（繁體）(Chinese (Traditional))
n. - 倫琴
idioms:
- roentgen rays X光射線
日本語 (Japanese)
n. - レントゲン
adj. - レントゲンの
idioms:
- roentgen rays レントゲン線
العربيه (Arabic)
(الاسم) الوحدة الدوليه لأشعه إكس
עברית (Hebrew)
n. - צילום או שיקוף בקרני רנטגן
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