Chapter 5 Flashcards
At what dose of whole-body radiation would an observable short-term effect of acute radiation syndrome result?
1.5 Gy
If the dose of radiation is large enough (generally over 1.0 Gy or 100 rads, whole body), the resultant signs and symptoms that comprise these short-term effects are collectively known as acute radiation syndrome (ARS).
What is the term for the damage that cannot be repaired and tissues remain weakened, especially with repeated exposures?
Cumulative effect
A cumulative effect refers to the theory that radiation-exposed tissues accrue damage and may function at a diminished capacity with each repeated exposure.
What theory of radiation damage to cells results from free radicals combining to form toxins such as hydrogen peroxide?
Indirect theory
Indirect theory is based on the assumption that radiation can cause chemical damage to the cell by ionizing the water within it.
What does a threshold dose-response relationship indicate?
The first statement is false. The second statement is true.
A nonthreshold dose-response relationship indicates that any dose, regardless of amount, can be expected to produce a biologic response.
Do scientists know whether low levels of radiation exposure carry health risks?
TRUE
Scientists do not know whether a threshold level exists, below which radiation would be safe.
Is a less specialized cell more radioresistant?
FALSE
According to the law of Bergonié and Tribondeau, the more specialized a cell is, the more radioresistant the cell.
Does a nonthreshold dose-response curve indicate a certain level of radiation below which no biological response should be anticipated?
FALSE
A threshold dose-response curve indicates that there is a threshold amount of radiation below which no biological effects would be expected.
What does the ALARA concept mean?
As low as reasonably achievable.
Radiation protection guidelines assume that every dose of radiation produces damage and should be kept to the minimum necessary.
Do all humans have the same sensitivity to radiation?
FALSE
Individuals vary in sensitivity within the same species.
Do all cells in the human body have the same sensitivity to radiation?
FALSE
There is a wide variation in sensitivity to radiation among different types of cells and tissues.
Have X-rays been shown to have carcinogenic effects?
TRUE
X-rays can cause cancer by a variety of mechanisms.
Are the structures of the oral and facial regions relatively radioresistant?
TRUE
The maxillofacial structures are composed largely of specialized tissues such as bone, nerve, and muscle.
When are cells most sensitive to radiation injury?
During mitosis (cell division).
Actively dividing cells are more sensitive than slowly dividing cells.
Can the biological effects of very low levels of radiation be predicted?
TRUE
Radiobiologists have been unable to determine what effects result from exposure to very low levels of radiation.
What does radioresistant refer to?
Tissues that are not easily injured by ionizing radiation.
Radioresistant refers to a substance or tissue that is not easily injured by ionizing radiation.
What is the latent period?
The time between exposure to radiation and the first clinically observable symptoms.
It does not refer to the ionization of molecules.
What is a somatic effect?
Damage occurs to the affected individual but is not passed along to offspring.
This occurs when somatic cells are irradiated.
What is the LD 50/30 for humans?
4.5 grays.
This is the average whole-body lethal dose to kill 50 percent of exposed humans in 30 days.
Why are children more susceptible to radiation than adults?
Young cells divide more rapidly than mature cells.
More rapidly dividing cells are more sensitive to the effects of radiation.
When do the effects of irradiation occur?
Following the latent period.
Effects can occur within a short or long latent period depending on the type of cell.
Does the severity of a stochastic effect increase with increased radiation dose?
No.
The probability of a stochastic effect increases but not its severity.
Who is more sensitive to equal doses of radiation exposure—adults or children?
Children.
Their cells are generally primitive and rapidly dividing.
Can dental x-rays cause cataracts in the lens of the eye?
No.
At least 5,000 millisieverts (mSv) of radiation exposure is required to cause cataract formation.
