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)
What is the whole body dose that will kill 50% of people within 30 days (LD 50/30)?
3-4 Gy without treatment
What is genetically significant dose?
GSD is an index of radiation received by the
genetic pool, which determines the progeny
of a given population. The annual GSD is
obtained by weighting the individual gonad
doses received during x-ray examinations
by the number of individuals examined and
by the relative contribution of those persons to the expected number of future
children to be produced by the population.
It is expected that this dose, if received by
every member of the population, would result in the same total genetic effect to the
population as the doses which are in fact
received by individuals within the population.
The limit to remember is 0.25 mSv.
What dose to a fetus during the first two weeks after conception may cause fetal loss? If fetal loss does not occur, what ill effects are predicted?
50-100 mGy. If fetal loss doesn’t occur, no ill effects are expected (all or nothing).
What is the most vulnerable period for a fetus?
8-15 weeks after conception
What dose during 8-15 weeks for a fetus are associated with small head size and mental retardation?
100-200 mGy
A drop of how many IQ points is commonly expected with a dose of 1 Sv to a fetus from 8-15 weeks?
30 IQ points
What is the most likely childhood cancer to occur due to fetal radiation exposure? And at what dose?
Leukemia, 10-20 mSv
When does the fetal thyroid start to take up iodine? aka after when should you not give the mother radioactive iodine?
8 weeks after conception
Between weeks 3-8, what is the most expected ill effect due to fetal radiation exposure and what is the dose threshold?
growth retardation, >250 mSv
What is the risk of cancer for the general public per Sv using the BEIR 5 and UNSCEAR models?
4-5%
What skin dose causes Early Transient Erythema and what is the time of onset?
2 Gy skin dose, onset within hours
What skin dose causes Severe Erythema and what is the time of onset?
6 Gy skin dose, 1 week
What skin dose causes Telangiectasia and what is the time of onset?
10 Gy skin dose, 1 year
What skin dose causes Dry Desquamation and what is the time of onset?
13 Gy skin dose, 4 weeks
What skin dose causes Moist Desquamation and what is the time of onset?
18 Gy skin dose, 4 weeks
What skin dose causes Secondary Ulceration and what is the time of onset?
24 Gy skin dose, > 6 weeks
What skin dose causes Temporary epilation (hair loss) and what is the time of onset?
3 Gy, 21 days
From warmachine: 3x7 = 21
What skin dose causes Permanent epilation (hair loss) and what is the time of onset?
7 Gy, 21 days
From warmachine: 3x7 = 21
Senile Cataracts tend to involve the ___ lens. Radiation induce cataracts tend to involve the ___ lens.
Senile Cataracts tend to involve the anterior lens. Radiation induce cataracts tend to involve the posterior lens.
Acute dose thought to cause radiation induce cataracts?
2.5 Gy
Annual limit dose to lens for workers
150 mSv (if 150 mSv isn’t an answer and 20 mSv is, go with 20 mSv. This is the new limit in Europe that will likely be adopted by the NRC soon)
Dose for male temporary sterility?
0.15 - 2.5 Gy
Dose for male permanent sterility?
5 Gy
Dose for female sterility age 12?
10 Gy
Dose for female sterility age 45?
2 Gy
Dose that can suppress circulating lymphocytes?
0.25 Gy WB (whole body)
Effective dose from background radiation in the US?
3 mSv per year
What contributes the most to the radiation dose to the US population?
Radon Gas exposure
What MAN MADE thing contributes the most to the radiation dose to the US population?
medical imaging
What is the dose trigger for additional patient care/follow up and is considered a sentinel event?
15 Gy to a single exposure field
What is the exposure limit to an adult worker?
50 mSv/year
What is the exposure limit to a worker under the age of 18?
5 mSv/year
What is the exposure limit to the extremity of a worker?
500 mSv/year
What is the limit of public radiation exposure?
5 mSv/year
What is the limit of public radiation exposure if continuous?
1 mSv/year
What is the occupational exposure limit to a fetus via the mother?
5 mSv/pregnancy (another 0.5 mSv is allowed if mother is already at or above 5 mSv at declaration)
What is the occupational exposure limit to the fetus after declared pregnancy?
0.5 mSv/month
What dose limit is accepted in a controlled area?
50 mSv/year
What dose limits is accepted in an uncontrolled area?
5 mSv/year or 0.02 mSv/hour
Does radiation induce sterility in males affect hormone levels?
No
Does radiation induce sterility in females affect hormone levels?
Yes, basically creates a postmenopausal state
