Radiation Exposure Units of Measure

Radiation Exposure Units of Measure 

Energy Absorbed from γ-rays and X-rays

                            Old   SI Units   Conversion

Radiation absorbed dose   Rad  Gray (Gy)   1   Gy  = 100 rad

                                                1 cGy  = 1 rad

Roentgen equivalent mass Rem Sievert (Sv)   1   Sv  = 100 rem 

Average Annual Exposure = 360 mRem or 0.0036 Sv

Chest X-Ray = 5-10 mrem   CT Scan = 5,000 mRem (0.05 Sv) 

Activity for Radiation Emission of Radionuclides

    Unit of Decay Ol d SI Unit Disintergrations/sec

• Curie  Ci -  1 Ci = 3.7 X 1010 dps

                                        1 Ci = 37 MBq

• Becquerel  - Bq  1 Bq = 1 dps

                                        1 MBq = 109 dps

Environmental (Natural) Radiation Exposure 

Average Annual Exposure

• 360 mRem or 0.0036 Sv

• Sources:

  • Cosmic radiation and radon

  • Cigarette smoke

  • Medical devices

  • Home appliances

  • Pharmaceutical agent

Specific Exposures

• 5-10 mRem:        Flight from New York to Los Angeles

• 5-10 mRem:  Chest radiograph

• 5,000 mRem (0.05 Sv): CT Scan