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What charges are at the cathode and anode end of the x-ray machine?
- Cathode = negative
- Anode = positive
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Why is tungsten used in x-ray machines?
- 1) High melting point
- 2) high atomic number for better picture
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T/F: X-rays are waves and particles?
T
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What happens to wavelength and frequency as the energy of the x-ray increases?
- wavelength: decreases
- frequency: increases
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What do low, moderate, and high x-rays interact with? Which is most common?
- Low: entire atom
- Moderate: electrons
- High: nuclei
- ** Moderate is most common
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How much x-ray is lost due to heat?
99%
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What happens to other 1% of x-ray not lost to heat?
- 10% = characteristic (deflected)
- 90% = Bremsstrahlung, braking radiation
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Where do the characteristic and Bremsstrahlung interactionc occur?
Anode
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What are 3 rxns of x-rays after leaving anode and coming into contact with the body?
- 1) non-attenuating
- 2) absorbed
- 3) scattered
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Name the two important diagnostic x-ray interactions?
- 1) Comptom effect: scattering of electrons
- 2) Photelectric effect: making the picture via absorption
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What does a Compton effect photon interact with?
Outer shell electrons
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kVp effects on Compton and Photelectric effects?
- kVP increases = compton increases (very fuzzy)
- kVp decreases = Photoelectric increases (dangerous)
- ***a common ground must be established for a safe and effective x-ray
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What does photoelectric effect come in contact with?
absorbed in inner shell electrons
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Which type of material interacts more with the photoelectric effect, bone or skin? Why?
Bone b/c of higher density
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What color is a radiopaque and radiolucent x-ray?
- Radiopaque: white
- Radiolucent: black
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What is kVp?
Kilovolt potential: quality of x-ray, can change the miliamp number causing it to drop
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What is mAs?
Miliamps per second: quantity of x-rays (decreases with high kVp)
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What is the Anode Heel effect?
higher x-ray intensity at cathode (-) end than anode (+) end so you want larger structures placed by cathode
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What happens to the anode heel effect as the anode angle decreases?
Increases
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What safety feature is used to reduce scatter radiation?
Grids
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T/F: Low ratio grids are better at picking up scatter radiation
F, high ratio grids are more effective
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What safety feature is used to reduce x-ray amounts to the patient?
Filters
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2 filters used in podiatry and their mm Al equivalents?
- 1) Inherent 1.5mm Al
- 2) Added 1.0mm Al
- Total 2.5mm Al
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What safety feature is used to reduce the does of x-ray needed?
Screens
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How many screens are used in podiatry?
1
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Name the five steps of conventional x-ray making?
- Developing
- rinsing
- fixing
- wash and dry
- temp and time
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What plays the highest role on image reception and exposure?
kVp
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Contrast:kVp ratios
- increase kVp = decrease contrast (long scale)
- Decrease kVp = increase contrast (short scale)
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Why is exposure time decreased during x-rays?
Avoid blurriness from patient movement
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15% rule of kVp?
15% increase in kVp decrease mAs by 2 (vice-a-versa as well)
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Common SID measurement?
21-40 inches
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Inverse square law of x-rays
- Radiation intensity inversely proportional to square of distance from source
- ** Smaller distance = greater intensity
- ** larger distance = less intensity
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T/F SID affects quality of x-ray beam
F
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common focal spot size?
1.0 mm
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T/F kVp should be change in increments of 2?
F, increments of 5
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