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<onlyinclude>The '''Roentgen''' or ''R'' is a non-[[SI]] [[units| unit]] for [[x-ray]] and [[gamma decay| gamma]] [[ionizing radiation| radiation]] in normal conditions under any given [[volume]] of [[air]] or [[ionization]] chamber.</onlyinclude> It was assumed that the energy absorbed by a given volume of air was equivalent to the amount of energy accumulated in an equal amount of soft tissue.<ref>] S.T. Cantril et al., “''The Tolerance Dose'',” United States Atomic Energy Commission, Argonne National Laboratory, Technical Information Division, Oak Ridge, Tenn. MDDC-1100. 1945.</ref> The Roentgen was established in 1908 and named after the German physicist who discovered x-rays, Wilhelm Röntgen.<ref>RTstudents. (2010), “''Radiology Innovators, Wilhelm Conrad Röntgen''” [Online]. Available:  http://www.rtstudents.com/radiology/wilhelm-conrad-rontgen.htm</ref> In 1998, the American national institute of standard and technology or NIST re-defined the use of the roentgen and is now strongly unsupported as an acceptable unit for dose of any type of ionizing radiation.<ref>NIST. (2016) “''Roentgen (Unit) – History – NIST Definition''” [Online]. Available: http://www.liquisearch.com/roentgen_unit/history/nist_definition</ref> However, it is still used as a unit of x-ray and gamma radiation.<ref>''Recommendations of the International Commission on Radiological Protection and of the International Commission on Radiological Units'', no.47, U.S. Department of Commerce, National Bureau of Standards, Washington, DC, 1950, pp. 2, 23.</ref> One roentgen is equivalent to 0.000258 [[coulomb]] per [[kilogram]] or 1R = 2.58x10<sup>-4</sup> C/kg.<ref>NIST. “''International System of Units, Units outside the SI''” [Online]. Available: http://physics.nist.gov/cuu/Units/outside.html</ref> Mathematically, roentgen is considered a form of [[exposure]] (''X'') which refers to the charge transmitted (''∆Q'') by a certain mass of air (''m'') which can thus be expressed as the equation: ''X''=''ΔQ''/''m''.<ref>R.L Murray, K.E. Holbert, “''The Rise of Nuclear Physics, Gas Encounters''” in Nuclear Energy, 7th ed. Waltham, MA, USA: Elseveier Inc, 2015, Ch.8.1, 12.2, pp. 109, 181</ref>
[[File:Wilhelm-conrad-roentgen-copy-2-original-jpg-640x455.jpg|thumb|Figure 1. German physicist Wilhelm Röntgen and the first X-ray image in history: of his wife Bertha's hand.<ref>Cuaderno de Cultura Cientifica (2015). (Accessed July 13, 2026). ''Radiografiando el arte'' [Online]. Available: https://culturacientifica.com/2015/11/09/radiografiando-el-arte/</ref>]]
<onlyinclude>The '''Roentgen''' or ''R'' is a non-[[SI]] [[units|unit]] for [[x-ray]] and [[gamma decay|gamma]] [[ionizing radiation|radiation]] in normal conditions under any given [[volume]] of [[air]] or [[ionization]] chamber.</onlyinclude> It was assumed that the energy absorbed by a given volume of air was equivalent to the amount of energy accumulated in an equal amount of soft tissue.<ref>] S.T. Cantril et al., “''The Tolerance Dose'',” United States Atomic Energy Commission, Argonne National Laboratory, Technical Information Division, Oak Ridge, Tenn. MDDC-1100. 1945.</ref> The Roentgen was established in 1908 and named after the German physicist who discovered x-rays, Wilhelm Röntgen (Figure 1).<ref>RTstudents. (2010), “''Radiology Innovators, Wilhelm Conrad Röntgen''” [Online]. Available:  http://www.rtstudents.com/radiology/wilhelm-conrad-rontgen.htm</ref>
 
In 1998, the American national institute of standard and technology (or NIST) re-defined the use of the roentgen and is now strongly unsupported as an acceptable unit for dose of any type of ionizing radiation.<ref>NIST. (2016) “''Roentgen (Unit) – History – NIST Definition''” [Online]. Available: http://www.liquisearch.com/roentgen_unit/history/nist_definition</ref> However, it is still used as a unit of x-ray and gamma radiation.<ref>''Recommendations of the International Commission on Radiological Protection and of the International Commission on Radiological Units'', no.47, U.S. Department of Commerce, National Bureau of Standards, Washington, DC, 1950, pp. 2, 23.</ref> One roentgen is equivalent to 0.000258 [[coulomb]] per [[kilogram]] or 1R = 2.58x10<sup>-4</sup> C/kg.<ref>NIST. “''International System of Units, Units outside the SI''” [Online]. Available: http://physics.nist.gov/cuu/Units/outside.html</ref> Mathematically, roentgen is considered a form of [[exposure]] (''X'') which refers to the charge transmitted (''∆Q'') by a certain mass of air (''m'') which can thus be expressed as the equation: ''X''=''ΔQ''/''m''.<ref>R.L Murray, K.E. Holbert, “''The Rise of Nuclear Physics, Gas Encounters''” in Nuclear Energy, 7th ed. Waltham, MA, USA: Elseveier Inc, 2015, Ch.8.1, 12.2, pp. 109, 181</ref>


=<small>Radiation-related quantities</small>=
=<small>Radiation-related quantities</small>=
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| Exposure || Roentgen || R || 2.58x10<sup>-4</sup> C/kg || Non-SI
| Exposure || Roentgen || R || 2.58x10<sup>-4</sup> C/kg || Non-SI
|-
|-
| Absorbed Dose || Rad <br/> Grey || rad <br/> Gy || 10<sup>-2</sup> Gy <br/>Jkg<sup>-1</sup>  || Non-SI <br/> SI
| rowspan="2" | Absorbed Dose || Rad || rad || 10<sup>-2</sup> Gy || Non-SI  
|-
|-
| Activity || Curie <br/> Becquerel || c <br/> Bq || 3.7x10<sup>10</sup> Bq <br/> s<sup>-1</sup> || Non-SI <br/> SI
|Grey
|Gy
|Jkg<sup>-1</sup>
|SI
|-
|-
| Dose Equivalent || Roentgen Equivalent Man <br/> Sievert || rem <br/> Sv || 10<sup>-2</sup> Sv <br/> Jkg<sup>-1</sup> || Non-SI <br/> SI
| rowspan="2" | Activity || Curie || c || 3.7x10<sup>10</sup> Bq || Non-SI  
|-
|-
|Becquerel
|Bq
|s<sup>-1</sup>
|SI
|-
| rowspan="2" | Dose Equivalent || Roentgen Equivalent Man || rem || 10<sup>-2</sup> Sv || Non-SI
|-
|Sievert
|Sv
|Jkg<sup>-1</sup>
|SI
|}
|}
== For Further Reading ==
* [[X-ray]]
* [[Gamma decay]]
* [[Radiation]]
* [[Coulomb]]
* Or explore a [[Special:Random|random page]]


==References==
==References==
{{reflist}}
{{reflist}}
[[Category: Uploaded]]

Latest revision as of 20:43, 4 August 2026

Figure 1. German physicist Wilhelm Röntgen and the first X-ray image in history: of his wife Bertha's hand.[1]

The Roentgen or R is a non-SI unit for x-ray and gamma radiation in normal conditions under any given volume of air or ionization chamber. It was assumed that the energy absorbed by a given volume of air was equivalent to the amount of energy accumulated in an equal amount of soft tissue.[2] The Roentgen was established in 1908 and named after the German physicist who discovered x-rays, Wilhelm Röntgen (Figure 1).[3]

In 1998, the American national institute of standard and technology (or NIST) re-defined the use of the roentgen and is now strongly unsupported as an acceptable unit for dose of any type of ionizing radiation.[4] However, it is still used as a unit of x-ray and gamma radiation.[5] One roentgen is equivalent to 0.000258 coulomb per kilogram or 1R = 2.58x10-4 C/kg.[6] Mathematically, roentgen is considered a form of exposure (X) which refers to the charge transmitted (∆Q) by a certain mass of air (m) which can thus be expressed as the equation: X=ΔQ/m.[7]

Radiation-related quantities

The following table shows radiation quantities in SI and non-SI units.[8][9]

Quantity Name Symbol Unit System
Exposure Roentgen R 2.58x10-4 C/kg Non-SI
Absorbed Dose Rad rad 10-2 Gy Non-SI
Grey Gy Jkg-1 SI
Activity Curie c 3.7x1010 Bq Non-SI
Becquerel Bq s-1 SI
Dose Equivalent Roentgen Equivalent Man rem 10-2 Sv Non-SI
Sievert Sv Jkg-1 SI

For Further Reading

References

  1. ↑ Cuaderno de Cultura Cientifica (2015). (Accessed July 13, 2026). Radiografiando el arte [Online]. Available: https://culturacientifica.com/2015/11/09/radiografiando-el-arte/
  2. ↑ ] S.T. Cantril et al., “The Tolerance Dose,” United States Atomic Energy Commission, Argonne National Laboratory, Technical Information Division, Oak Ridge, Tenn. MDDC-1100. 1945.
  3. ↑ RTstudents. (2010), “Radiology Innovators, Wilhelm Conrad Röntgen” [Online]. Available: http://www.rtstudents.com/radiology/wilhelm-conrad-rontgen.htm
  4. ↑ NIST. (2016) “Roentgen (Unit) – History – NIST Definition” [Online]. Available: http://www.liquisearch.com/roentgen_unit/history/nist_definition
  5. ↑ Recommendations of the International Commission on Radiological Protection and of the International Commission on Radiological Units, no.47, U.S. Department of Commerce, National Bureau of Standards, Washington, DC, 1950, pp. 2, 23.
  6. ↑ NIST. “International System of Units, Units outside the SI” [Online]. Available: http://physics.nist.gov/cuu/Units/outside.html
  7. ↑ R.L Murray, K.E. Holbert, “The Rise of Nuclear Physics, Gas Encounters” in Nuclear Energy, 7th ed. Waltham, MA, USA: Elseveier Inc, 2015, Ch.8.1, 12.2, pp. 109, 181
  8. ↑ NIST. (2016, February 10). Chapter 5. Guide to the SI, Units Outside the SI [Online]. Available: http://www.nist.gov/pml/pubs/sp811/sec05.cfm
  9. ↑ NIST. (2016, February 19). Chapter 4. Guide to the SI, The Two Classes of SI Units and the SI Prefixes [Online]. Available: http://www.nist.gov/pml/pubs/sp811/sec04.cfm
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