Radiation Biology Flashcards
What is radiation exposure and what unit is it measured it?
The ability of xrays to ionize air, measure in Roentgens (R). aka the concentration of radiation in air at a specific point.
What is absorbed radiation dose or radiation dose? What units are used for it?
The amount of energy absorbed per unit mass at a specific point, measuring in Gy or Rads (1 Gy = 100 rads).
What is equivalent dose and what unit is it measured in?
The absorbed dose of different types of radiation creates different levels of biologic damage (measured in Sv).
Equivalent dose = dose x weight factor
Weight factor is 1 for xray or gamma ray, 20 for alpha particles
What is effective dose and what unit is it measured in?
This takes equivalent dose and adds another weighting factor for specific tissue sensitivity to radiation. (in Sv)
Effective dose =equivalent dose x tissue factor
What is higher? Tissue dose or air Kerma?
Tissue dose is about 10% higher due to internal scattering.
How does Kerma-Area Product (KAP) change with distance?
It doesn’t. KAP=Dose x area. Dose decreases as inverse squared and area increases as the square so they cancel out.
Geometric magnification will ___ entrance skin KERMA and _____ KAP.
Geometric magnification will INCREASE entrance skin KERMA and with not change the KAP.
Collimation will ____ the KAP.
Collimation will decreased the KAP.
Collimation will ____ the entrance air kerma?
Collimation will slightly increase the entrance air kerma due to the AEC increasing dose.
Air Kerma or KAP is an indicator of deterministic risk (i.e. skin burns)?
Air Kerma or KAP is an indicator of stochastic risk (cancer)?
Air Kerma is an indicator of deterministic risk (i.e. skin burns)?
KAP is an indicator of stochastic risk (cancer)?
Deterministic or Stochastic effects has a threshold, severity is dose related, and dose not include cancer risk?
Deterministic effects has a threshold, severity is dose related, and dose not include cancer risk.
Deterministic or Stochastic effects has no threshold, severity is not dose related, probability of effect increases with dose, includes heritable effects and carcinogenesis?
Stochastic effects has no threshold, severity is not dose related, probability of effect increases with dose, includes heritable effects and carcinogenesis?
What is Linear Energy Transfer (LET), what types of radiation are considered high LET and what are considered low LET?
LET is the average amount of energy deposited per unit path.
High LET: Neutrons, Protons, Alpha Particles, and Heavy Ions
Low LET: Photons, Gamma Rays, Electrons, Positrons
What is the difference between direct and indirect ionizing radiation?
Direct = radiation acts directly on the DNA
Indirect = radiation acts on water in the cytoplasm creating a free radical which then damages DNA.
Which process is promoted by the presence of oxygen, direct radiation or indirect radiation?
Indirect radiation is promoted by the presence of oxygen.
Which process is more common and is more likely for low LET radiation, direct or indirect radiation?
Indirect radiation is more common and is more likely for low LET radiation.
What syndrome is most sensitive to x-rays?
Ataxia Telangiectasia
Cells are most sensitive to radiation during which cell phase? Least sensitive during which phase?
Cells are most sensitive to radiation during the M phase and least sensitive during the S phase.
Cells are more sensitive to radiation the ___ they turn over and the ___ differentiated they are.
Cells are more sensitive to radiation the more they turn over and the less differentiated they are.
What part of the GI tract is the most radiosensitive?
The small bowel
With low LET, what is the ‘shoulder’ on cell survival curves?
The quasi-threshold dose, the low dose part of the curve where cell repair mechanisms are kicking in.
What are the most sensitive blood cells in the body?
Lymphocytes
How can one use lymphocytes as a marker of whole body dose exposure?
Average body radiation dose can be estimated by scoring the number of chromosomal aberrations at the first mitotic division of lymphocytes stimulated to divide.
A total body dose of ___ will cause nausea about 30% of the time.
0.75-1.25 Gy
With acute radiation syndrome, what whole body radiation dose is needed for Bone Marrow syndrome, the GI syndrome, and the CNS syndrome?
Bone marrow: >2 Gy
GI: > 8 Gy
CNS: > 20-50 Gy
What is a sign of poor prognosis in acute radiation syndrome?
Early vomiting (less than 1 hour after exposure is really bad)