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33 Cards in this Set
- Front
- Back
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What is the direct theory? |
Photons collide with important cell chemicals and breaks them apart by ionization, causing critical damage to large molecules |
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How much of biological alterations from x-radiation exposure results from direct effect? |
1/3 |
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What is Indirect theory of radiation? also known as (radiolysis of water) |
Based on the assumption that radiation can cause chemical damage to the cell by ionization the water within it. |
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How much biological alterations from x-radiation exposure results from indirect theory |
2/3 |
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What is the Law of B and T? |
The degree of susceptibility of various cells and body tissues to radiation. |
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What does the law of B and T state: |
1. actively dividing cells, such as red blood cells are more sensitive than slowly dividing cells
Actively dividing cells= more sensitive (red blood cells)
2. more specialized a cell is the more radiolucent it is.
Exceptions are: white blood cells and reproductive cells
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What has the highest sensitivity? |
White Blood Cells (Lymphocytes)
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What has the lowest sensitivity? |
Muscle cells |
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In what order from highest to lowest is sensitivity? |
White Blood Cells Red Blood Cells Immature reproductive cells Epithelial cells endothelial cells Connective tissue cells Bone Cells Nerve cells brain cells Muscle cells |
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When does Somatic effect occurs when? |
Biological change or damage occurs in the irradiated individual, but is not passed along to offspring |
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When does Genetic effect occur? |
describes the changes in hereditary material that do not manifest in the irradiated individual,but in future generations
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Which cells are somatic |
all cells of the body EXCEPT
reproductive cells |
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Threshold dose- response curve Indicates what? |
that there is a "thresh-old" amont of radiation below which no biological response would be expected
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A nonthreshold dose- response curve indicates what? |
that any amount of radiation, no matter how small, has potential to cause a biological response
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What does ALARA stand for? |
as low as reasonably achievable |
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When does the latent period occur? |
Following the initial exposure and before the first detectable effect occurs, a time lag occurs |
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How long does the latent period last |
Could be short could be long depending on the initial dose and other factors
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Period of Injury: |
Following Latent Period |
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What Effects can be observed during the period of injury? |
Stopping of mitosis, or cell division in growing tissues that have been exposed.
This can be temporary or Permanent |
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Recovery Period: |
Following exposure to radiation |
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Can any recovery take place during the recovery period? |
some recovery can take place |
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Name the sequence of events that may follow exposure to radiation in order? (3) |
Latent Period
Period of Injury
Recovery Period |
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Deterministic Effect is what? |
When the severity of the change is dependent on the dose |
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Stochastic Effect is what? |
When a biological response is based on the probability of occurrence rather than the severity of change |
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Cancer is an example of what effect and why? |
Stochastic Effect/
An all or nothing occurrence. when the dose of radiation is increased, the "probability" of the stochastic effect (cancer) occurring increases but not its severity |
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How long does it take for short term effects of irradiation to be seen? |
Seen in minutes, days, or weeks after exposure |
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How long does it take for long term effects of irradiation to be seen? |
Years after original exposure |
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What are some symptons that can occur because of short term effects of irradiation? |
Nausea, vomiting, diarrhea, hemorrhage, and hair loss |
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What are some symptons that can occur because of long term effects of irradiation? |
Cancer, Embryological defects, cataracts, and genetic mutations. |
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What are the most critical tissues of the head and neck |
mandible (red bone marrow)
The lens of the eyes
the thyroid gland
hypothalamus pituitary- thyroid combinations |
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The exact amount of radiation exposure produced depends on what? (3) |
Film speed
Technique Used
Collimation type Whether it's circular or rectangular |
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Discuss the risk versus benefits of dental radiographs |
Dental radio-graphs should be taken only when the benefit outweighs the risk of biologic injury to the patient
There have been no reports of radiation injuries caused by normal dental procedures since the safety protocols have been adopted |
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When should dental radio-graphs be taken? |
Only when the benefit outweighs the risk of biologic injury to the patient |
