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The curie (symbol Ci) is a non-SI unit of radioactivity originally defined in 1910. According to a notice in Nature at the time, it was to be named in honour of Pierre Curie , [ 1 ] but was considered at least by some to be in honour of Marie Skłodowska-Curie as well, [ 2 ] and is in later literature considered to be named for both.
The commission has been responsible for defining and introducing many of the following units of measure. The number of different units for various quantities is indicative of changes of thinking in world metrology, especially the movement from cgs to SI units. [6] The following table shows radiation quantities in SI and non-SI units.
The unit of activity is the becquerel (symbol Bq), which is defined equivalent to reciprocal seconds (symbol s −1). The older, non-SI unit of activity is the curie (Ci), which is 3.7 × 10 10 radioactive decays per second. Another unit of activity is the rutherford, which is defined as 1 × 10 6 radioactive decays per second.
In the 1930s the roentgen was the most commonly used unit of radiation exposure. This unit is obsolete and no longer clearly defined. This unit is obsolete and no longer clearly defined. One roentgen deposits 0.877 rad in dry air, 0.96 rad in soft tissue, [ 9 ] or anywhere from 1 to more than 4 rad in bone depending on the beam energy. [ 10 ]
The becquerel is a special name for second to the power minus one, to be used as the SI unit of activity. curie: 1 Ci = 3.7×10 10 Bq (exactly) ⋮ absorbed dose: D: For any ionizing radiation, the mean energy imparted to an element of irradiated matter divided by the mass of this element gray: Gy: 1 Gy = 1 J/kg
This allows physicians to deliver high doses of radiation even when tumors are close to sensitive organs and tissue. A proton therapy beam's powerful energy is focused directly on a patient's tumor. Once released, the energy stops – there is no exit dose and no additional radiation unlike X-ray beams and gamma knife rays. [11]
For applications in radiation protection and dosimetry assessment, the International Commission on Radiological Protection (ICRP) and the International Commission on Radiation Units and Measurements (ICRU) have published recommendations and data on how to calculate equivalent dose from absorbed dose.
Radiation exposure was expressed in the historical unit of working level month (WLM). This unit of measurement was introduced in the 1950s specifically for occupational safety in uranium mines in the U.S. [87] to record radiation exposure resulting from radioactive exposure to radon and its decay products in the air we breathe. [88]