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Radiation Protection
Patient Protection
Question | Answer |
---|---|
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. |