Radiation biology Flashcards
1
Q
Exposure:
- Define.
- Units?
A
- The ability of XRs to ionize air. It is the concentration, in air, of radiation at a specific point.
- Roentgens.
2
Q
Absorbed dose:
- Define.
- Units?
- How many rads in this unit?
A
- Amount of energy absorbed per unit mass.
- Grays or rads
- 1 Gy = 100 rads.
3
Q
Rads, Grays, Sieverts
- # rads / Gy?
- SI defn Gray
- What do Sieverts measure?
- How many rems in 1 Sv?
A
- 100 rads/Gy
- 1 Gy = 1 joule/kg (hence, Gy is defined as amt of energy absorbed per unit mass)
- Health/biologic effect of ionizing radiation.
- 1 Sv = 100rem.
4
Q
Equivalent dose:
- Define.
- Units?
- Weighting factors for: photons (XRs, gamma rays), neutrons, alpha particles.
A
- Radiation dose to tissue based on the type of radiation.
- Sieverts, as it measures health effect (or rem).
- Photons: 1; neutrons = 5-20; alpha particles = 20.
5
Q
Effective dose
- Define.
- Units
- Equation
- What is the value if all the radiation is absorbed (1 Gy, say)?
- Give tissue weighting factors for the most & least sensitive tissues.
A
- Takes into account whether radn has been absorbed by the specific tissue.
- Sv.
- dose x radn weighting factor x tissue weighting factor, so essentially this is EqD x tissue weighting factor.
- If 1 Gy absorbed, then 1 Sv.
- Most: 0.12; bone marrow, colon, lung, breasts, stomach.
- Least: 0.01; bone, skin, brain.
6
Q
- Draw the table of exposure & the 3 dose types: definitions, units & other notes.
7
Q
What is the risk of developing a fatal cancer with 1 Sv radn?
A
5.5% chance.
8
Q
Radn dose (Gy) that causes instant cell death?
A
1,000 Gy
9
Q
- Which clinical syndrome is most sensitive to XRs.
- Which is most sensitive to UV radn?
A
- Ataxia telangiectasia.
- Xeroderma pigmentosa. (mnemonic: dermis gets pigmented by UV)
10
Q
- What is the dose for a CTAP?
- What is a dose that makes you sick?
- What total body dose will cause nausea 30% of the time?
A
- 30 mGy.
- Gy, e.g., 2 Gy messes w/your bone marrow.
- 0.75-1.25 Gy.