摘自 energyeducation 网站。
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 = 2.58x10-4C/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]
1单位伦琴是在0摄氏度，760毫米汞柱气压的1立方厘米空气中造成1静电单位正负离子的辐射强度，而非测算其他物质，例如人类皮肤的辐射吸收量的单位。现在已废弃使用。
