Radiation protection dosimetry Anne Laure Lebacq, Olivier Van Hoey Belgian Nuclear Research Centre SCK•CEN Photo by SCK•CEN
Why do we need dosimetry?
Radiation induces health effects Photo by Wikipedia / CC BY SA Photo by www.oramed-fp7.eu Skin burns Cataract Cancer
2 types of health effects Deterministic effects Stochastic effects E.g. burns, cataract, hair loss, organ failure E.g. cancer, inheritable effects Only above threshold dose No threshold dose Severity increases with dose above threshold Probability increases with dose Appear typically immediately Appear typically after several decades
3 pillars of radiation protection • Justification • ALARA = As Low As Reasonably Achievable • Dose limits
How can we express and measure the dose?
How much energy is deposited in the body? Organ absorbed dose D T Energy deposited per unit of mass for tissue T Expressed in Gy (gray) = J/kg Photo by www.oramed-fp7.eu
How harmful is the radiation? Radiation weighting factor w R Expresses how much more damaging radiation type R is with respect to photons for the same organ absorbed dose Dimensionless
How harmful is the radiation? Radiation type R Radiation weighting factor w R Photons, electrons, 1 muons Protons, charged 2 pions Alpha’s, heavier 20 nuclei Neutrons w R ( E )
How sensitive are the affected tissues? Tissue T Tissue Tissue weighting factor w T weighting factor w T Expresses which fraction of Red bone marrow, colon, 0.12 stochastic effects occurs in lung, stomach, breast, remaining tissue T for a uniform whole Gonads 0.08 body radiation exposure Bladder, oesophagus, liver, 0.04 Dimensionless thyroid Bone surface, brain, salivary 0.01 glands, skin
� Quantification of deterministic effects Organ equivalent dose H T 𝐼 " = $ 𝑥 & 𝐸 ",& Photo by www.oramed-fp7.eu & Expressed in Sv (sievert) = J/kg Photo by SCK•CEN
� Quantification of stochastic effects Effective dose E 𝐹 = $ 𝑥 " 𝐼 " Photo by SCK•CEN " Expressed in Sv (sievert) = J/kg ~ 5% extra cancer risk per Sv Photo by SCK•CEN Photo by SCK•CEN
Photo by SCK•CEN
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