LATE EFFECTS OF RADIATION AND HEALTH PHYSICS Flashcards
What is health physics concerned with?
Providing occupational radiation protection and minimizing radiation dose to the public.
A radiation scientist focused on research, teaching, or operational aspects of radiation safety.
health physicist
What is the rationale behind practicing ALARA?
The linear nonthreshold radiation dose-relationship (LNT) for stochastic effects
What are examples of stochastic effects?
Cancer, leukemia, and genetic effects.
How should time be managed to minimize radiation exposure?
Keep the exposure time as short as possible.
What is the effect of minimizing time in radiography?
Reduces motion blur.
How is radiation dose related to exposure duration?
It is directly related.
Sequences on-off to reduce exposure rather than continuous use.
fluoroscopic footswitch
Reminds the radiologist of the elapsed fluoroscopic time.
5-minute reset timer
How long do most fluoroscopic procedures take?
Less than 5 minutes.
How does distance affect radiation dose?
Radiation dose is inversely related to the distance from the source.
What law applies to distance and radiation intensity?
The inverse square law.
What is an x-ray tube target considered as?
A point source of radiation.
Lines representing positions of equal radiation exposure
isoexposure lines
How much is the exposure rate at a normal position in a fluoroscopy room?
300 mR/hr or 3 mGya/hr.
How does moving two steps back affect the exposure rate in fluoroscopy?
Reduces it to 5 mR/hr.
What is assumed about occupational effective dose?
It is assumed to be 10% of the monitor dose.
How does a protective apron reduce occupational exposure?
0.5 mm Pb apron reduces exposure to 25%.
The thickness of absorber needed to reduce radiation intensity by half.
half-value layer (HVL).
The thickness of absorber needed to reduce radiation intensity to one-tenth.
tenth-value layer (TVL).
What is the effective dose in radiation terms?
The equivalent whole-body dose.
What is the tissue dose for a CT of the abdomen and pelvis?
2000 mrad.
What is the effective dose for a PA chest radiograph?
1.35 mrad.
What is the weighting factor for gonads?
0.20.
What is the weighting factor for active bone marrow?
0.12.
What is the weighting factor for the colon?
0.12.
What is the weighting factor for the liver?
0.05.
A sealed radioactive source that directly exposes people.
Radiation Exposure Device (RED)
What is not required for a RED?
Decontamination, as it does not disperse radioactive material.
A bomb that disperses radioactive contamination over a wide area.
Radiologic Dispersal Device (RDD)
A device containing nuclear material capable of a nuclear explosion.
Improvised Nuclear Device (IND)
At what exposure rate is the inner boundary established in a radiologic event?
10 R/hr.
How should radiation detection equipment alarms function?
Emit alarms at 10 mR/hr, 10 R/hr, and 50 R/hr.
What is the main basis for radiation protection guides?
Late effects of radiation and linear, nonthreshold dose-response relationships.
What are late effects of radiation also known as?
Stochastic effects.
What are principal late effects of radiation exposure?
Radiation-induced malignancy and genetic effects.
What does the stochastic radiation response indicate?
The probability of a biologic response as a function of dose, with no threshold.
What type of exposure do radiology personnel typically experience?
Low dose, low LET, and chronic exposure.
What can high-LET radiation, like neutron and proton radiation, cause?
High RBE for the production of cataracts.
What device did E.O. Lawrence develop in 1932?
The first cyclotron.
What is the threshold dose for cataract formation from acute x-ray exposure?
200 rad.
What is the life span shortening expectation for radiation workers?
About 12 days of life lost.
What type of leukemia is rare and not linked to radiation exposure?
Chronic lymphocytic leukemia
What is the at-risk period for radiation-induced leukemia?
20 years after exposure.
What type of cancer did watch dial painters develop?
Bone cancer due to radium ingestion.
How does radium behave in the body?
It acts like calcium and deposits in bones.
What is the half-life of uranium in the context of lung cancer risk?
10⁹ years.
What type of cancer is caused by Thorotrast exposure?
Liver cancer.
What is the main pregnancy concern before conception?
Interrupted fertility.
What is the main pregnancy concern during gestation?
Potential congenital effects in the newborn.
What are the effects of in utero irradiation?
Prenatal death, congenital malformation, malignancy, growth impairment, and genetic effects.
Why are the first two weeks of pregnancy considered least concerning for radiation?
Due to the all-or-nothing response.
What happens during major organogenesis (2nd-10th week)?
Risk of skeletal and organ abnormalities.
What is the relative risk of childhood leukemia after in utero exposure?
1.5 overall, but 8.3 during the first trimester.
what is the time frame for congenital abnormalities risk in pregnancy?
2-10 weeks.
What is the natural occurrence rate of spontaneous abortion?
25%.
What is the radiation-induced risk for congenital abnormalities?
1% with 10 rad exposure.
Who reported the genetic effects of radiation on fruit flies?
H.J. Muller.
What did H.J. Muller conclude about radiation-induced mutations?
They are linear and nonthreshold.
What is the doubling dose in radiation genetics?
The dose needed to double the frequency of genetic mutations.
What is a key characteristic of most radiation-induced mutations?
They are recessive and may not show for generations.
What does the radiation response of mental retardation depend on?
Time of exposure, with the highest risk at 2-15 weeks.
What is the primary concern for post-pregnancy radiation exposure?
Potential genetic effects.
What cancer risk is associated with dusty mine environments?
Lung cancer, especially among uranium miners.
What did the first cyclotron developed in 1932 accelerate?
Charged particles to high energies.
What are examples of high-LET radiation with high cataract RBE?
Neutrons and protons
What radiation-induced cancers have no threshold?
Stochastic effects, like thyroid and skin cancer.
What was Thorotrast used for historically?
As a contrast agent in angiography.
What is the half-life of radium
1620 years.
How long is the latent period for radiation-induced cataracts?
Can range from 5 to 30 years.
What are isotopic sources of radiation in medical use?
Tritium and promethium.
What was a common treatment in early radiology that caused skin cancer?
Orthovoltage x-ray therapy.
What are the most sensitive periods for radiation exposure in pregnancy?
The first trimester and organogenesis weeks.
What dose of radiation to the eye lens is unlikely to be reached occupationally?
More than 1000 rad.
What is the average effective dose for a CT scan of the abdomen?
740 mrem.
