Radiation Protection & Legal Aspects Flashcards
~73% of the background radiation is from
radon
- Decay of uranium-238
- One of the most naturally ocurring radioactive element
- Second cause for lung cancer
- Releases alpha particles
- ~73% of the background radiation
Radon-222
What kind of space radiation:
Composed of subatomic particles
Large quantity is blocked by
terrestrial electromagnetic shield
Harmful to astronauts
Primary
What kind of space radiation:
Affects living beings on Earth
Interaction of primary radiation with the atmosphere
Increases with the altitude
~11% of background exposure
Secondary
~9% of background exposure is from
internal radionuclides
What kind of radiation:
Radioactive nuclides in the soil
Potassium-40 and decay products of uranium-238 and thorium-232
~7% of background exposure
terrestrial radiation
Cigarette smoking
* Building materials
* Air travel
* Combustion of fossil fuels
* ~4% of non-background exposure
Consumer products
The principal risk of oral and maxillofacial radiography is the unlikely chance of
radiation-induced cancer
In general, these studies demonstrate reasonable evidence that cancer risk
increases linearly with radiation exposures greater than
100 mSv
linear relationship between dose and the risk of inducing a new cancer, even at very
low doses
no threshold or “safe dose” below which there is no added cancer risk
Linear no-threshold (LNT) hypothesis
The ___ model is currently accepted as the approach to develop radiation protection
guidelines
LNT
Which guiding principle?
Benefit of the diagnostic exposure exceed the Risk of harm
justification
Which guiding principle?
Dentists should use all possible means to reduce unnecessary exposure to their patients, staff and themselves
optimization
The radiation dose to the patient should be kept as
low as possible
Optimization - ALARA (as low as reasonably achievable)
The radiation dose to the patient should be kept as
low as diagnostically acceptable
Optimization - ALADA (as low as diagnostically achievable)
The individual effective dose shall not exceed the limits recommended by the International Commission on Radiation Protection (ICRP)
Dose limitation
Good performance of Dentistry → Average dose of ____ mSv (1% of the limit)
0.2
Is there a defined dose limit for patients?
No
Rectangular collimation can reduce the effective dose by as much as 80 % and it improves image quality by reducing _____
scatter
Rectangular collimation of the x-ray beam shall be used routinely for ____ and _____ radiography
periapical ; bitewing
_______ limits the amount of radiation, both primary and scattered, to which the patient is exposed
collimation
An added benefit of rectangular collimation is an
improvement in contrast as a result of a reduction in fogging caused by _____ and _____ radiation
secondary ; scattered
Since a rectangular collimator _____ the radiation dose by up to fivefold as compared with a circular one, radiographic equipment should provide
rectangular collimation for exposure of periapical and bitewing radiographs
decreases
Which patient protection measure?
To filter out the photons with less energy
filtration
Which patient protection measure?
The most sensitive receptor compatible with indicated
examination should be used
imaging receptors
Film speeds available for dental radiography are D-speed, E-speed and F-speed, with D-speed being the
____ and F-speed the _____
slowest ; fastest
Switching from D to E speed can produce a ______ percent reduction in radiation exposure
30-40%
The use of F-speed film can reduce exposure ______ compared to use of E-
speed film, without compromising diagnostic quality
20-50%
Digital imaging provides an opportunity to further reduce the radiation dose by ______ percent
40-60%
Image receptors of speeds slower than ANSI Speed Group E/F (AKA D-SPEED) shall not be
used for _____ radiography
intraoral
Which patient protection measure:
The longer the distance, the less divergent the photons will be, and the lower the irradiated area
Source-to-skin distance
Use of long source-to-skin distances of 40 cm, rather than short distances of 20 cm,
decreases exposure by _______ percent
10-25%
Which patient protection measure:
They should be used whenever possible
Reduce the number of repetitions
Receptor holding devices
The ideal differential potential is between ____ and ____ kVp
Factors should be adjusted to obtain a great quality image, avoiding over or underexposure
Proper exposure time is essential!
60 and 70 kVp
The optimal operating potential of dental x-ray units is between ___ and ____ kVp
60 and 70 kVp
For a given beam, the intensity is _________ to the square of the distance from the source
inversely proportional
The reason for the decrease in intensity regarding distance is that an x-ray beam spreads out as it moves ____ its source
from
When shielding is not possible, the operator should stand at least ___ meters from the tube head and out of the path of the primary beam
2
Maximum dose will generally be in line with the primary beam as it ___ the patient
exits
