Chapter 13 - Screens Flashcards

1
Q

What is an intensifying screen?

A

a device that converts the energy of the x-ray beam into visible light

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2
Q

What are the 4 layers of a screen?

A

base
reflective layer
phosphor
protective coating

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3
Q

What is the function of the base layer?

A

support for phosphor layer

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4
Q

What is the function of the reflective layer?

A

redirects the light to the film

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5
Q

The reflective layer is composed of

A

a shiny substance

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6
Q

What is the function of the phosphor?

A

convert the energy of the x-ray beam to visible light

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7
Q

What is the active substance in the phosphor?

A

rare earth crystals

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8
Q

What is luminescence?

A

any material that emits light in response to some outside stimulation

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9
Q

What are the 2 types of luminescence?

A

fluorescence & phosphorescence

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10
Q

Which type of luminescence is visible light only while the phosphor is stimulated?

A

flourescense

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11
Q

Which type of luminescence is NOT desirable?

A

phosphorescence

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12
Q

What quantitates the efficiency of conversion of x-rays to light?

A

screen speed

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13
Q

What is a measure of the ability of a system to image two separate objects and visually distinguish one from the other

A

resolution

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14
Q

factors such as fast screen speed, large phosphor crystal size, thick phosphor, high kvp will result in what type of resolution?

A

low resolution

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15
Q

what is the undesirable fluctuation in optical density

A

image noise

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16
Q

what is the mottled or noisy appearance of the film due to the number of photons exposing it

A

quantum mottle

17
Q

what is the ability to produce an accurate and clean image

A

spatial rasolution

18
Q

What is the holder that contains the film and intensifying screen

19
Q

as screen speed increases, density ________

20
Q

adding screens or increasing screen speeds, ________ contrast

21
Q

increasing screen speed, _______ detail

22
Q

as screen speed increases, patient dose _______

23
Q

what is the formula for screen speed conversion?

A

old mAs * new RS
—————————- = new mAs
old RS

24
Q

radiation exiting the window of the tube

A

primary radiation

25
radiation produced after primary interacts with patient
secondary radiation
26
radiation exiting the tube housing
leakage radiation
27
radiation exiting the patient
remnant radiation
28
how does kvp affect scatter?
higher kvp, more scatter
29
How does collimation affect scatter?
smaller collimation, less scatter
30
How does patient size affect scatter?
larger patient, more scatter
31
How does tissue density affect scatter?
more dense, less scatter
32
What is the feature of radiographic collimators that automatically adjusts the radiation field to the size of the image receptor?
positive beam limitation (PBL)
33
What is the removal of low energy x-rays from the useful beam with aluminum or another metal?
filtration
34
Increasing filtration does what to patient dose?
decreases!