Contrast

Question 1

• makes details visible
• a psychovisual perception
• the variation in density levels that makes detail visible

Answer 1

contrast

Question 2

• caused by attenuation and differential absorption
• variation, changes or differentiation of adjacent densities on the radiograph
• produced by photoelectric effect

Answer 2

contrast

Question 3

its primary function is to make detail visible

Answer 3

contrast

Question 4

differentiations between densities or details be readily made

Answer 4

satisfactory contrast

Question 5

___ controls differential absorption of the x-ray beam by the body because of its control of x-ray beam energy

Answer 5

kVp controls differential absorption of the x-ray beam by the body because of its control of x-ray beam energy

Question 6

• inherent in the screen-film combination
• influenced somewhat by processing of the film

Answer 6

image receptor contrast

Question 7

• affected by film (IR), film type & direct/IS exposure
• affected by range of ODs and film processing technique

Answer 7

image receptor contrast

Question 8

film-screen images have _______ contrasts than direct film exposure images

Answer 8

film-screen images have HIGHER contrasts than direct film exposure images

Question 9

controlled by anatomy and pathology; affects contrast through variations of Z, tissue thickness, and tissue density

Answer 9

subject contrast

Question 10

most important factor in controlling subject contrast

Answer 10

kVp

Question 11

subject contrast
↓ kVp = _ contrast

Answer 11

subject contrast
↓ kVp = ↑ contrast

Question 12

photoelectric effect varies in proportion to the cube of Z

Answer 12

effective atomic number

Question 13

enhances contrast by enhancing photoelectric absorption

Answer 13

contrast media

Question 14

objects that coincide with the x-ray beam have high subject contrast

Answer 14

object shape

Question 15

caused by the shape of the structure

Answer 15

absorption blur

Question 16

• The difference in density/brightness between adjacent values are great.
• The transition from white to black areas are fast and abrupt.
• Can be achieve with the use of low kVp.
• Is usually pleasing to the eye, but does not give better diagnostic value.

Answer 16

high contrast

Question 17

high contrast

↑ contrast = _ gray tones / short-scale contrast

Answer 17

high contrast
↑ contrast = ↓ gray tones / short-scale contrast

Question 18

low contrast

↓ contrast = _ gray tones / long-scale contrast

Answer 18

low contrast
↓ contrast = ↑ gray tones / long-scale contrast

Question 19

• The differences in density/brightness between adjacent values are small
• Transition from black to white areas are slow and there are many shades of gray that represent varying tissues in the body
• Can be achieve with the use of high kVp.

Answer 19

low contrast

Question 20

means the range of optical densities from the lightest to the blackest part of the radiograph

Answer 20

scale of contrast

Question 21

there is great differences between available densities
high contrast
low kVp

Answer 21

short scale contrast

Question 22

there is little differences between available densities
many shades of gray
low contrast
high kVp

Answer 22

long scale contrast

Question 23

____ is the only factor that can control contrast of the radiograph

Answer 23

kVp is the only factor that can control contrast of the radiograph

Question 24

controls the differential absorption of the x-ray beam in the body

Answer 24

kVp

Question 25

OID

↑ OID (15 to 25 cm) = air gap technique = _ scatter cleanup (equivalent to 8:1 grid ratio) = _ contrast

Answer 25

↑ OID (15 to 25 cm) = air gap technique = ↑ scatter cleanup (equivalent to 8:1 grid ratio) = ↑ contrast

Question 26

air gap technique disadvantage

_ magnification, _ SID, _ mAs to maintain density

Answer 26

air gap technique disadvantage

↑ magnification, ↑ SID,↑ mAs to maintain density

Question 27

Grid

↓ scatter reaching the image receptor = _ scatter fog = _ gray tones = _ contrast

Answer 27

↓ scatter reaching the image receptor = ↓ scatter fog = ↓ gray tones = ↑ contrast

Question 28

limits are being irradiated

Answer 28

beam restriction

Question 29

beam restriction

↓ field size = _ number of Compton interactions
= _ scatter = _ patent dose = _ gray tones = ↑ contrast

Answer 29

↓ field size = ↓ number of Compton interactions
= ↓ scatter = ↓ patent dose = ↓ gray tones = ↑ contrast

Question 30

as filtration is ↑, beam becomes ______ (average photon striking the patient has shorter wavelength)

Answer 30

as filtration is ↑, beam becomes HARDER (average photon striking the patient has shorter wavelength)

Question 31

↑ filtration = harder photons = _ Compton scatter = _ contrast

Answer 31

↑ filtration = harder photons = ↑ Compton scatter = ↓ contrast

Question 32

air-gap technique = _ contrast (owing to air filtration)

Answer 32

air-gap technique = ↓ contrast (owing to air filtration)

Question 33

aka subject contrast

Answer 33

anatomy and pathology

Question 34

cause differential absorption of x-ray photons, which results in contrast

Answer 34

anatomy and pathology

Question 35

anatomy and pathology

↑ atomic number = _ contrast
(owing to photoelectric effect)

↑ tissue density = _ contrast
(owing to Compton scattering)

↑ tissue thickness = _ contrast
(owing to Compton scattering)

use of a contrast agent = _ contrast
(owing to photoelectric effect)

Answer 35

↑ atomic number = ↑ contrast
(owing to photoelectric effect)

↑ tissue density = ↓ contrast
(owing to Compton scattering)

↑ tissue thickness = ↓ contrast
(owing to Compton scattering)

use of a contrast agent = ↑ contrast
(owing to photoelectric effect)

Question 36

↑ processing time = ↑ chemical fog = _ contrast

Answer 36

↑ processing time = ↑ chemical fog = ↓ contrast

Question 37

↑ chemical temperature = ↑ chemical fog = _ contrast

Answer 37

↑ chemical temperature = ↑ chemical fog = ↓ contrast

Question 38

In digital images, _______ can be enhanced through post-processing and is mostly affected by the pixel bit depth available in the system.

Answer 38

In digital images, CONTRAST can be enhanced through post-processing and is mostly affected by the pixel bit depth available in the system.

Question 39

number of bits available for each pixel

Answer 39

pixel bit depth