X-ray Quality and Quantity Flashcards
penetrability
ability of x-rays to penetrate deeper in tissue
x-rays that have high penetrability are termed:
high-quality x-rays
factors affecting x-ray beam quality:
kVp
filtration
target material
generator type
kVp is:
the max voltage applied to the tube
increasing kVp:
increases the kinetic energy of the electrons therefore creating more photons
required total filtration:
2.5 mm Al
collimator and an additional filter (added) provides how much filtration?
2.0 mm Al
inherent filtration provides
how much filtration?
0.5 mm Al
what is the primary purpose of adding filtration?
remove low energy photons from the beam
increasing filtration:
increases the average quality of the beam
what does increasing filtration create?
more monoenergetic and harder average beam
target material affects both:
the number and average quality of photons produced
higher energy x-rays increase in number to a ________________ than low-energy photons
greater extent
what will shift the effective energy of the x-ray spectrum?
target material
what doesn’t target material shift?
the position of spectrum along the x-axis
half value layer (HVL)
thickness of a material needed to cut the intensity in half
as beam quality goes up,
so does the HVL
the HVL measures the quality of
the x-ray beam
what happens if a HVL isn’t enough for a certain kVp amount?
additional sheets of filtration are added
as more filtration is added, what happens to the HVL?
HVL increases in order to reduce the intensity in half
factors affecting quantity:
mA
kvp
exposure time
filtration
quantity is directly proportional to:
mA
when mA is doubled:
the electrons are doubled, therefore the number of x-rays emitted is doubled
when exposure time is doubled,
the number of x-rays emitted is doubled
increasing filtration will:
decrease the quantity of the beam
higher kVp =
higher quantity
due to more electron attraction, resulting in greater photon amount (quantity)
saturation current:
current at its max value because all electrons have been used up
doubling kvp increases intensity by a factor of:
4!!
the higher the Z number of a material:
the higher the quantity of x-rays
the greater the anode angle, the lesser the:
anode heel effect
the greater the target angle,
the greater the quantity
less anode heel effect =
greater quantity
a more powerful generator will:
produce a higher quantity of x-rays
variable-kVp techniques
uses a fixed mAs value and a kVp that varies according to the
thickness of the anatomical part
produces shorter scale images
fixed-kVp technique
kVp is selected as the optimum required for penetration of the part. The mAs is then adjusted according to thickness
produces longer gray scale images
mA
heat (temp) of the filament
unit of measure for tube current
mA
x-ray production require greater quantities of what?
voltage
longer exposure time =
more x-rays produced
SID:
distance from the Actual focal spot to the IR
what is the best protection from radiation?
distance
required HVL at 130 kVp
3.5 mm Al
two factors that determine an x-ray photon’s keV
kVp
proximity to nucleus
what’s the relationship between anode angle and beam quantity?
direct (more photons can escape anode)
what is the controlling factor for beam quality?
kVp
the HVL test is a measure of ________ that uses ________ as a unit of measurement
quality, quantity
why is kVp not used to make adjustments in beam quantity?
changes in kVp affect beam quality
what characteristic makes a target material an “efficient” target, when it comes to quantity?
high Z number
the required HVL at 90 kVp is:
2.5 mm Al
the prime exposure factor that affects both quality and quantity (described as the “big wrench”)
kVp
increasing SID has what effect on beam quality?
none (moving the tube doesn’t affect the energy)
changing a 50 kVp setting to a 100 kVp (doubling kVp) will have what effect on beam quantity?
increases by 4x
who is responsible for performing an annual HVL test?
physicist
increasing filtration has what effect on HVL?
increase
x-ray beam quality and differential absorption share what type of relationship?
indirect
x-ray beam average quality improves by what?
filtration
what is the difference between intensity and quantity?
intensity is the number of photons that land in a certain area due to SID
quantity is the number of x-rays exiting the tube
Law of Reciprocity:
exposure will be the same if mAs is constant
mAs = mAs = mAs
