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28 Cards in this Set

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Screen phosphors should have
1. a high atomic number
2. high conversion efficiency
3. light matched to film used
4. minimal afterglow
primarily silver halide crystals in gelatin
May be coated on one or both sides of the film
Emulsion speed is a function of grain diameter or surface area
k-edge absortion and intensifying screens
all rare earth materials have atomic numbers < tungsten
therefore, all K shell EBF are less than tungsten
this is why rare earth phosphors absorb more photon energy than calcium tungstate
use KVP values that exceed the K shell EBF for your screens, usually over 60 KVP
the random distribution of a small number of photons over the surface of the intensifying screen and film
quantum mottle
Noise or graininess
How it’s created: very fast film/screen combinations and high frequency generators
How to find it: look on a full spine radiograph of a thin patient in the region of the liver
quantum mottle
4 parts of screen
protective coating
phosphor layer
reflective layer
importance of Reflective layer in screen
light is produced isotropically
takes light produced by screen moving away from the film and directs it toward the film
increases the speed of the screen by doubling the number of photons reaching the film
importance of base:
provides mechanical support for phosphor layer
Flat (tabular grains) purpose in film:
offer a larger cross section with more light gathering capability than conventional grains

Tabular grains are more tolerant to developer activity (more forgiving)
Emulsion speed is a function of
of grain diameter or surface area
which is advantages of duplitizing film over single emulsion film?
the blue dye in a film emulsion helps to
reduce eye fatigue in reading films
which will increase contrast
decrease kvp
function of screen inside cassette is
reduce patient exposure.
emit light to be absorbed by film.
k edge absoprtion:
use KVP values that exceed the K shell EBF for your screens, usually over 60 KVP
international community uses gray (Gy) and sievert (Sv)
what are they?
gray is patient dose
sievert is occupational exposure
Do I need to adjust the tube’s position when using a 15 degree tube tilt at 40”? This AP lower cervical technique requires an exposure dose of 15 mr for a proper exposure
yes use inverse square law
should get 14 % decrease
Velocity of light
3 x 108m/s
why phosphor thickness for films
The thicker the phosphor layer, the higher the number of x-rays converted to light.
High speed screens have thick layer. Detail screens have a thin layer.
purpose of crystals in screen
Larger crystal produce more light per interaction. Detail screens have small crystals.
purpose of spatial resolution
Image detail is the result of spatial resolution and contrast resolution.
Generally the conditions that increase speed reduce spatial resolution.
what is the focal spot
is the area of the anode from which the x-rays are emitted.
The angling of the target is know as
line focus principle
By angling the anode target, one makes the the effective focal spot ____than the actual area of interaction
much smaller
is the beam projected onto the patient.
effective focal spot
as the anode angle decreases
the effective focal spot decreases.
The advantage of Line focus
provides the sharpness of the small focal spot with the heat capacity of the large large focal spot.
Tube life is extended by
Use of minimum mAs & kVp appropriate for the exam.
Use of faster images receptors require lower mAs and kVp. They extend tube life