chapter 5 Flashcards
What are the two kinds of radiation?
Natural , Manmade
X-rays collide with cell chemicals, breaks them apart, create ionization and therefore, cell damage. Which biological theory is this?
Direct-HIt (target)
Radiation causing chemical damage of the water within a cell through ionization.
Which biological theory is this?
in-direct action (poison water)
Explain the law of B & T.
Actively dividing cells are more sensitive than slowing dividing cells.
The more specialized the cell, the more radio-resistant it is.
Rank the order of the cell sensitivity.
White blood cells Red blood cells Endothelial cells Bone cells Muscle cells
What is the dose-response curve?
A relationship between an administered dose and the response produced.
What is a threshold does-response curve?
It indicates that there is a “threshold” amount of radiation which no biological response would be expected.
What is a nonthreshold dose-response curve?
It indicates that any amount of radiation no matter how small, has the potential to cause a biological response.
What are the radiation injury factors?
Total dose Dose rate Area exposed Variation in species Individual sensitivity Variation in cell sensitivity Variation in tissue sensitivity Age
What is the radiation injury factor total does?
The total dose of the radiation depends on the type, energy, and duration of the radiation. The greater the dose, the more severe the probable biological effect.
What is the radiation injury factor dose rate?
The rate at which the radiation is administered or absorbed is very important in the determination of what effects will occur. Because a considerable degree of recovery occurs from the radiation damage, a give does will produce less effect if it is divided (thus allowing time for recovery between dose increments) than if it is given in a single exposure.
What is the Event Sequence After Radiation Exposure?
Latent Period, Period of Injury, Recover period.
Explain short-term effects of radiation.
seen within a reasonably short amount of time after exposure.
Acute radiation syndrome (ARS) is associated with.
Explain why short- term ARS is not seen in dentistry.
because dental x-ray machines cannot produce the very large exposures nessessary to cause it.
Explain the long-term effects of radiation.
it is seen years after the original exposure. The latent period is much longer than associated with ARS. Delayed radiation effects may result from previous acute, high-exposure that the individual has survived or from chronic low-level exposures delivered over many years.
What are the long-term effects related to dentistry?
Cancer Embryological defects Low birth weight Cataracts Genetic mutations – changes in genetic material. Small dental contribution
Risk varies depending on what three factors?
speed of film, collimation, and the technique used.
Explain risk vs. benefit.
Radiographs are to be taken only when the benefit outweighs the risk of injury.
What conditions determine a cell’s sensitivity to radiation exposure?
As the law of B & T points out , cells with a potential for rapid division are more sensitive to radiation than those that do not divide.
What role does effective dose equivalent play in comparing a medical chest x-ray with a dental periapical radiograph?
According to table 5-3 a periapical is equivalent to .2 days of natural exposure. While the chest x-ray is equivalent to 10 days.
What is the difference between stochastic and deterministic (non-stochastic) effects?
Deterministic is used when referring to a tissue response whos severity is directly related to the radiation does, while the Stochastic is the tissue response based on the possibility of occurence.
What are examples of Deterministic, and Stochastic?
Deterministic- Erythema (redness of skin) would not be expected to occur just from seconds of sunlight.
Stochastic - the occurence of cancer because it is an all or nothing response.
Explain the cumulative nature of radiation exposure.
Much of the low-level radiation damage we receive is repaired within the cells of the body. Some repeated radiation damage remains unrepaired and accumulates in the body.
Retaking a radiograph because of a technique or processing error causes an increase in radiation exposure for the patient. Discuss ways a retake radiograph affects the factors that determine radiation injury.
Total Dose- so the greater the dose the more sever the probable biological effect.
Dose rate- the rate at which the radiation is administered.
