Chapter 12 Flashcards
What are the three principal factors that affect x-ray emissions that are under direct control of the radiographer?
The prime factors; mAs, kVp, and distance
What are two terms that can describe the x-ray beam?
quantity and quality
What is x-ray quantity?
a measure of the number of x-ray photons in the useful beam.
What is another name for x-ray quantity?
x-ray output, intensity, or exposure
What is the measurement of x-ray quantity?
roentgen (R)
What are the factors that directly affect x-ray quantity?
mAs, kVp, and filtration
What is x-ray quality?
a measurement of the penetrating ability of the x-ray beam
What does penetrability describe?
the distance an x-ray beam travels in matter
Which travels farther high energy photons or low energy photons?
high energy photons; therefore they penetrate more
What is another name for highly penetrating x-rays?
hard x-rays
What is another name for low-penetrating x-rays?
soft x-rays
How is x-ray quality numerically represented?
the half-value layer
What is the half-value layer of an x-ray beam?
that thickness if absorbing material needed to reduce the x-ray intensity(quantity) to half its original value
What are the factors that directly affect x-ray quality?
kilovoltage and filtration
What are the factors that control quantity and/or quality of x-ray emission?
the prime factors and filtration
Can radiographers control filtration from exposure to exposure?
no
What is milliampeage (mA)?
a measurement of x-ray tube current- the number of electrons crossing the tube from cathode to anode per second
Milliamperage is directly or inversely proportional to tube current?
directly
When mA doubles, what else doubles?
the number of electrons able to cross the tube
What is the number of electrons reaching the target controlled by?
the length of time the tube is energized
How is the x-ray exposure time measured?
seconds
X-ray quantity is directly or inversely proportional to mAs?
directly
What else doubles when the mAs doubles?
x-ray exposures
What records the image that is then displayed on the monitor for viewing?
the image receptor
What is radiographic density?
the degree of blackening of an x-ray film
How is radiographic density created?
by deposits of black metallic silver within the emulsion fo an x-ray film that has been exposed to light or x-ray and then processed.
What happens to the image if the EI and IR exposure numbers are outside of the acceptable range?
the image has then been underexposed or overexposed and must be repeated
Insufficient amount of mAs will result in?
an underexposed image
Excessive amount of mAs will result in?
an overexposed image
What does kVp control?
both the quantity and quality of the x-ray beam
What will happen if you increase the kVp on the x-ray control panel?
it will cause and increase in the speed and energy of the electrons applied across the x-ray tube
What does the 15 percent rule state?
an increase in kVp by 15 percent will cause a doubling in IR exposure, the same effect as doubling the mA or doubling exposure time
The intensity of x-rays varies greatly with changes in ____.
distance
The x-ray intensity will ____ as the distance is increased.
decrease
What is x-ray intensity(exposure) measured in?
roentgens (R)
What does the inverse square law state?
that the intensity of radiation at a given distance from the point source is inversely proportional to the square of the distance
