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Radiation Protection

Patient Protection

QuestionAnswer
What will reduce involuntary motion unsharpness on x-rays ? Use a short exposure time.
Voluntary motion unsharpness is caused by ? Poor patient instructions or communication.
What is an example of involuntary patient motion ? heart contraction / relaxation, bowel peristalsis.
Pig-o-stat, sponges, sand bags, tape are examples of ? Immobilization devices.
When a primary proton interacts with an outer-shell electron and changes direction and becomes a scattered photon, it is a ? Compton interaction.
Beam restriction results in ? Fewer primary photons being emitted, creating less scatter radiation.
Less scatter means ? Less patient dose.
How does kilovoltage affect the beam ? Penetrability.
What happens to photons when kVP is higher ? Fewer interactions with matter / patient occur and more photons reach the image receptor.
What are the predominate type of interactions that occur in diagnostic X-ray ? Photoelectric and Compton.
If kVp increases, the percentage of what type of interactions will increase? Compton.
If kilovoltage alone is increased, without any other changes in technical factors, what is the result ? More scatter.
What are the principal factors affecting the amount of scatter produced ? Kilovoltage and irradiated material.
With an increase in kVP, an accompanying reduction in mAs will result in ? a decrease in scatter.
What affects the amount of scatter created? The volume and atomic weight of the material being irradiated.
To decrease scatter production, what needs to be done ? The operator needs to use the smallest field size.
What are types of beam-limiting devices? Diaphragms, cones, collimators.
What type of beam-limiting device is used in dental radiography? Cones.
In diagnostic x-ray the most common beam-restricting device is the ? Variable aperature collimator.
Collimators are required to be accurate within ? 2% of the SID.
Collimators are used too ? Regulate the field size to the anatomical structure of interest.
What is the purpose of lead shutters? To restrict x-ray beam to field of interest.
What is the purpose of the upper shutters in the variable-aperature collimator ? To absorb off-focus radiation before it leaves the x-ray tube.
When low energy photons are absorbed by filters, we say the beam is ? Hardened.
When low energy photons are absorbed by filters, patient dose is ? Reduced.
The glass window of the x-ray tube and oil surrounding the tube housing are ? Inherent filtration.
Aluminum or aluminum equivalent outside of glass window of the tube housing are ? Added Filtration.
What is total filtration? Added filtration and inherent filtration.
What is the total filtration requirement in fixed radiographic equipment operating above 70 kVp ? 2.5 mm Al eq.
What is the total filtration requirement in fixed radiographic equipment operating below 50 kVp ? 0.5 mm Al eq.
What is the total filtration requirement in fixed radiographic equipment operating between 50 and 70 kVp ? 1.5 mm Al eq.
What determines adequate filtration of the diagnostic x-ray beam ? The half-value layer measurement.
What is the Half Value Layer ? The thickness of material that will reduce the x-ray intensity to half its original value.
Created by: ervickie