Roentgen
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.[1] The Roentgen was established in 1908 and named after the German physicist who discovered x-rays, Wilhelm Röntgen.[2] 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.[3] However, it is still used as a unit of x-ray and gamma radiation.[4] One roentgen is equivalent to 0.000258 coulomb per kilogram or 1R = 2.58x10-4 C/kg.[5] 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.[6]
The following table shows radiation quantities in SI and non-SI units.[7][8]
| Quantity | Name | Symbol | Unit | System |
|---|---|---|---|---|
| Exposure | Roentgen | R | 2.58x10-4 C/kg | Non-SI |
| Absorbed Dose | Rad Grey |
rad Gy |
10-2 Gy Jkg-1 |
Non-SI SI |
| Activity | Curie Becquerel |
c Bq |
3.7x1010 Bq s-1 |
Non-SI SI |
| Dose Equivalent | Roentgen Equivalent Man Sievert |
rem Sv |
10-2 Sv Jkg-1 |
Non-SI SI |
References
- ↑ ] 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.
- ↑ RTstudents. (2010), “Radiology Innovators, Wilhelm Conrad Röntgen” [Online]. Available: http://www.rtstudents.com/radiology/wilhelm-conrad-rontgen.htm
- ↑ NIST. (2016) “Roentgen (Unit) – History – NIST Definition” [Online]. Available: http://www.liquisearch.com/roentgen_unit/history/nist_definition
- ↑ 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.
- ↑ NIST. “International System of Units, Units outside the SI” [Online]. Available: http://physics.nist.gov/cuu/Units/outside.html
- ↑ 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
- ↑ 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
- ↑ 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