Radiation Dose units

Units of Radiation

1. 'Curie' and 'Becquerel' :- are radiation units for quantity of radionucleotide disintegration per second.

2. 'Rad', 'Gray', 'cGy' are units of Absorbed dose of Radiation.

3. 'Sievert' :- is the S.I. Unit of Equivalent dose of Radiation

What is Equivalent dose of Radiation ?

A: Equivalent dose of radiation = Absorbed Dose of Radiation x Weighing Ratio (WR). 

Radiation units

• Activity is the transformation (disintegration) rate of a radioactive substance
  • Curie (Ci)
  • Becquerel (Bq) - S.I. Unit

  1 Bq = 1 disintegration per second (dps)
  1 Ci = 3.7 x 10¹⁰ dps
  1 Ci = 3.7 x 10¹⁰ Bq

• Absorbed dose is a physical quantity which represents the energy imparted by radiation onto an absorbing material.
  • Rad
  • Gray (Gy) - SI Unit

    1 Gy = 1 joule per kilogram
    1 Gy = 100 rads
    

• Dose Equivalent (DE) may be regarded as an expression of dose in terms of its biological effect. DE takes account of the fact that, for a given absorbed dose, such as 1 Gray, a radiation of one type and/or energy may give rise to a greater biological effect than a radiation of another type and/or energy.
  
  

  DE = Absorbed Dose x Quality Factor (Q)

  • Q depends on the type of radiation.
    Q = 1 for gamma, x-ray and beta
    Q = 10 for alpha
    
    Q is used to compare the biological damage producing potential of various types of radiation, given equal absorbed doses. The effectiveness of radiation in producing damage is related to the energy loss of the radiation per unit path length. The term used to express this is linear energy transfer (LET). Generally, the greater the LET in tissue, the more effective the radiation is in producing damage.
  • REMS
    
  • SIEVERT (Sv) - S.I. Unit
    
    1 Sv = 100 rems
    
    
• Exposure is a quantity that expresses the ability of radiation to ionize air and thereby create electric charges which can be collected and measured
  • Roentgen (R)
    1 R = 2.58 x 10^-4 c/kg of air