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69 Cards in this Set
- Front
- Back
*Ionizing radiation is... |
harmful and produces biologic changes in living tissue |
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Radiation Biology |
the study of the effects of ionizing radiation on living tissue |
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Ionization Radiation |
Produces biologic changes in living tissues. |
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*A free Radical is... |
simply an atom with one or more unpaired electrons in its orbit |
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*Free Radical Formation results in |
hydrogen and hydroxyl free radicals (toxin) |
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To achieve stability, free radicals do 1 of 3 things: |
Recombine w/o causing changes in the molecule. |
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Characteristics of a free Radical: |
Uncharged Molecule |
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*Cell damage results when ionizing radiation directly hits critical areas within the cell (DNA) |
The Direct Theory |
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*X-ray photons are absorbed within the cell and cause the formation of toxins which in turn damage the cell (via free radicals) |
The Indirect Theory |
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The chance of free radical formation and indirect injury is great because cells are composed of... |
70-80% water |
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*Dose-Response Curve is used to |
correlate the "response" or damage of tissues with the dose or amount of radiation received. |
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Linear Relationship |
The response of the tissues-damage-is directly proportional to the dose. |
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Nonthreshold Relationship: |
A threshold dose level for damage doesn't exist-it's not as if you need a certain dose for damage to occur. (A response can be seen at any dose) -There is no absolute SAFE amount of radiation exposure. |
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*Radiation Injury sequence, repair and accumulation: |
varying amounts of time are required for changes to cellular tissue to appear. |
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The time that elapses between exposure to ionizing radiation and the appearance of observable clinical signs. (The more radiation received and the faster the dose rate, the shorter the latent period.) |
*Latent Period (Sunburn=Red) |
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Follows the latent period when cells show damage. |
*Period of Injury (Blisters) |
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*Recovery Period: |
Depending on a number of factors, cells can repair the damage caused by radiation (if allowed time to repair). |
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The effects of radiation exposure are additive and damage that remains un-repaired accumulates in the tissue |
*Cumulative Effects |
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What are the determining factors of Radiation Injury?* |
Total dose, dose rate, amount of tissue irradiated, cell sensitivity, age. |
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Total Dose: |
Quantity of radiation received. (Large quantities of Radiation=More damage) |
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Dose Rate: |
Dose/Time; more damage takes place with high dose rates because a rapid delivery of radiation doesn't allow time for the cellular damage to be repaired. |
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Amount of tissue irradiated: |
Extensive radiation injury occurs when large areas of the body are exposed because of the damage that occurs to the blood-forming tissues. |
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Cell Sensitivity: |
Rapidly dividing, young cells are more adversely affected |
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Age: |
Children are MORE susceptible to radiation than adults |
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Stochastic Effects: |
occur as a direct function of dose. |
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non-Stochastic effects (Deterministic): |
Somatic effects that have a threshold and increase in severity with increasing absorbed dose. EX. Sunburn, hair loss, cataracts, decreased fertility. |
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*Short Term Radiation Effects: |
Seen in Minutes, days, or weeks |
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*Long Term Effects: |
Genetic, seen after years, decades or generations |
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All the cells in the body EXCEPT the reproductive cells. |
Somatic Cells * |
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NOT seen in the person irradiated, but are passed on to future generations. |
Genetic Cells (aka. reproductive cells: ova, sperm) |
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Can Genetic Damage be repaired? |
NO |
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T or F: Cancer cells rapidly divide and are less differentiated. * |
TRUE: that's why radiation therapy can be successful in the treatment of cancer. |
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Define Critical Organ: |
Organ that if damaged diminishes the quality of a person's life |
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*Critical organs exposed during dental radiographs: |
Skin, Thyroid, Lens of the eye, Bone Marrow |
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*Radiation Measurements |
units are used to define 3 quantities of radiation: Exposure, Dose, Dose Equivalent. |
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Traditional/Standard system of measurement: |
-Roentgen (R) -Roentgen Equivalent in man (rem) |
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International System of Measurement: |
Coulombs/kilogram (C/kg)- electrical charge. |
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Both ____ and _____ are measured in 1 cc/Kg of air |
Roentgen & Coulomb |
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*Gray (Gy): |
1 Gy= 100 rads (Radiation absorbed Dose) |
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*Sievert: |
1 Sv= 100 REM's OR |
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Background Radiation |
Form of radiation that is all around us (enviornment) -Sea level is less than the U.S average |
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*likelihood of adverse effects or death resulting from exposure to a hazard |
Risk |
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Risk of dental radiography inducing a fatal cancer in approx. is ... |
3/1,000,000 |
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*Thyroid Gland est. dose of ____mrad is necessary to produce cancer. |
600mrad |
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Skin: ____mrads |
Skin: 250 mrads, 500 dental films in 14 days Eyes: 60 mrads, so low the scientists no longer consider the lens of the eye a critical organ. |
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Collimation: use of rectangular instead of round reduces radiation by... |
60-70% |
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T or F: The benefit of disease detection DOESN'T outweigh the risk of damage of radiation. |
FALSE. The benefit of disease detection outweighs the risk of radiation. |
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Q: The Latent period in radiation biology is the time between: A) Exposure of film and developing |
D) Exposure to x-radiation and clinical symptoms |
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Whats the difference between Direct and Indirect? |
Direct: Cell damage results when ionizing radiation directly hits critical areas within the cell (DNA)
Indirect: X-ray photons are absorbed within the cell and cause the formation of toxins which in turn damage the cell (via free radicals) |
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Which of the follow are incorrect: C) In dental radiography, the benefit of disease detection outweighs the risk of damage of radiation |
A) X-radiation is not harmful to living tissues |
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First important step in limiting the amount of x-radiation exposure |
Prescribing Dental Radiographs |
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FMS (18 films) with lead apron recieves ___REM to the uterus |
FMS: 1mREM to uterus |
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Provided by the glass window of the x-ray tube, the insulating oil, and the tubehead seal. |
Inherent filtration |
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*Al disks placed in the path of the x-ray between the collimator and the tubehead seal; used to filter out the longer wavelength, low energy x-rays. |
Added Filtrations |
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T or F: inherent filtration alone does not meet standards. You need ALL layers. |
TRUE |
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collimation: |
Used to restrict the size and shape of the X-ray beam, reducing patient exposure. |
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*Which Position-Indicating Device (Rectangular or Conical) is more effective? |
Rectangular is more effective than round at reducing patient exposure; disadvantage is that it's easier to "cone"-cut. -Reduces x-radiation exposure by 60-70% |
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What is the difference of collimation and filtration of the x-ray beam? |
Collimation focuses the beam, and filtration takes away wavelengths. |
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T or F: The thyroid collar IS recommended for use with extraoral films |
FALSE: it is NOT recommended for use with extraoral films. |
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What is the single most effective method in reducing a pt's exposure to x-radiation? |
Fast Film* |
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E speed and F speed are the fastest intraoral film available, compared to the D speed film, it requires only ___ the exposure time. |
Half* |
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Dental Radiography must stand at least how many feet away from the tubehead? |
6 feet* |
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Any radiation with the exception of the primary beam that is emitted from the dental tubehead |
Leakage radiation |
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Radiation Control for Health and Safety Act: enacted in ____ to standardize the performance of x-ray equipment. |
1968* |
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Consumer-Patient Radiation Health and Safety Act: enacted in _____ and addressed the certification of persons using radiographic equipment. |
1981* |
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Occupationally exposed (work in a nuclear plant or constantly around radiation) person: |
5.0 rem/yr*
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Nonoccupationally exposed (we are considered nonoccupational) persons: |
.01 rem/year* |
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Maximum Accumulated Dose (MAD)* is determined by... |
worker's age (minimum age requirement is 18) |
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what does ALARA stand for? |
"As Low As Reasonable Achievable" |