UNITS OF RADIATION
Radioactivity is measured in Becquerel (Bq) per second. 1 Bq means one disintegration per second. It is also measured in Curie (Ci), named for Madam Curie, who shared Nobel Prize with her husband. 1 Curie = 3.7 x 1010 Bq or disintegrations per second. The radiation absorbed dose is measured in Gray, rad, rem and Sievert (Sv).
In the United States, absorbed dose is commonly given in rad or Gray and other protection quantities, such as equivalent dose and effective dose, are given in rem. The following table is provided to help avoid confusion among persons not familiar with these quantities. The use of the newer system of units would be particularly useful during radiological incidents involving international responders.
Conversions for Effective Dose, Equivalent Dose, Dose Equivalent, and ambient dose equivalent
0.001 rem = 1 mrem = 0.01 mSv
0.01 rem = 10 mrem = 0.1 mSv
0.1 rem = 100 mrem = 1 mSv = 0.001 Sv
1 rem = 1000 mrem = 10 mSv = 0.01 Sv
10 rem = 100 mSv = 0.1 Sv
100 rem = 1000 mSv = 1 Sv (Sievert)
1000 rem = 10 Sv
Conversions for Absorbed Dose
0.001 rad = 1 mrad = 0.01 mGy
0.01 rad = 10 mrad = 0.1 mGy
0.1 rad = 100 mrad = 1 mGy = 0.001 Gy
1 rad = 1000 mrad = 10 mGy = 0.01 Gy
10 rad = 100 mGy = 0.1 Gy
100 rad = 1000 mGy = 1 Gy (Gray)
1000 rad = 10 Gy
Measured Dose (Temporary Measurements) – gamma radiation or X-rays
1 R (roentgen) = 0.01 Gy = 0.01 Sv
NCRP Report No. 138, Oct. 24, 2001, “Management of Terrorist Events Involving Radioactive Material,” Recommendations of the National Council on Radiation Protection and Measurements, Bethesda, MD
“An Evaluation of Radiation Exposure Guidance for Military Operations, Interim Report,” Committee on Battlefield Radiation Exposure Criteria, Fred A. Mettler, Jr, Chairman, Medical Follow-up Agency, Institute of Medicine of the National Academy of Sciences, National Academy Press, Wash., DC, 1997.