Chapter 13 - Screens

Question 1

What is an intensifying screen?

Answer 1

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

Question 2

What are the 4 layers of a screen?

Answer 2

base
reflective layer
phosphor
protective coating

Question 3

What is the function of the base layer?

Answer 3

support for phosphor layer

Question 4

What is the function of the reflective layer?

Answer 4

redirects the light to the film

Question 5

The reflective layer is composed of

Answer 5

a shiny substance

Question 6

What is the function of the phosphor?

Answer 6

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

Question 7

What is the active substance in the phosphor?

Answer 7

rare earth crystals

Question 8

What is luminescence?

Answer 8

any material that emits light in response to some outside stimulation

Question 9

What are the 2 types of luminescence?

Answer 9

fluorescence & phosphorescence

Question 10

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

Answer 10

flourescense

Question 11

Which type of luminescence is NOT desirable?

Answer 11

phosphorescence

Question 12

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

Answer 12

screen speed

Question 13

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

Answer 13

resolution

Question 14

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

Answer 14

low resolution

Question 15

what is the undesirable fluctuation in optical density

Answer 15

image noise

Question 16

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

Answer 16

quantum mottle

Question 17

what is the ability to produce an accurate and clean image

Answer 17

spatial rasolution

Question 18

What is the holder that contains the film and intensifying screen

Answer 18

cassettes

Question 19

as screen speed increases, density ________

Answer 19

increases

Question 20

adding screens or increasing screen speeds, ________ contrast

Answer 20

increases

Question 21

increasing screen speed, _______ detail

Answer 21

decreases

Question 22

as screen speed increases, patient dose _______

Answer 22

decreases

Question 23

what is the formula for screen speed conversion?

Answer 23

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

Question 24

radiation exiting the window of the tube

Answer 24

primary radiation

Question 25

radiation produced after primary interacts with patient

Answer 25

secondary radiation

Question 26

radiation exiting the tube housing

Answer 26

leakage radiation

Question 27

radiation exiting the patient

Answer 27

remnant radiation

Question 28

how does kvp affect scatter?

Answer 28

higher kvp, more scatter

Question 29

How does collimation affect scatter?

Answer 29

smaller collimation, less scatter

Question 30

How does patient size affect scatter?

Answer 30

larger patient, more scatter

Question 31

How does tissue density affect scatter?

Answer 31

more dense, less scatter

Question 32

What is the feature of radiographic collimators that automatically adjusts the radiation field to the size of the image receptor?

Answer 32

positive beam limitation (PBL)

Question 33

What is the removal of low energy x-rays from the useful beam with aluminum or another metal?

Answer 33

filtration

Question 34

Increasing filtration does what to patient dose?

Answer 34

decreases!