unit 4 review

Question 1

why would an image be too dark

Answer 1

to many photons hitting IR, too dense

Question 2

how to fix an image that is too dark

Answer 2

window level adjustment

Question 3

why would an image appear too light

Answer 3

not enough photons hitting the IR, underexposed

Question 4

how to fix an image that is too light

Answer 4

can’t , repeat image

Question 5

controlling factor affecting density / IR exposure

Answer 5

mAs

Question 6

influencing factor affecting density / IR exposure

Answer 6

kVp

Question 7

more kVp =

Answer 7

more scatter

Question 8

mAs must be changed from ____% to see a visible change in density

Answer 8

25-35

Question 9

mAs & density are

Answer 9

directly proportional; BUT just because we double mAs does not mean density is doubled

Question 10

in digital what are the graphic representations of the IR exposure

Answer 10

histograms

Question 11

the width of the histogram

Answer 11

displays the range of exposures

Question 12

the 2 ways kVp alters intensity

Answer 12

a change in kV alters the intensity of the beam when all other factors remain the same & affects the production of scatter

Question 13

kVp being altered affects both

Answer 13

quality & quantity (scatter)

Question 14

with a large focal spot

Answer 14

size bloom may occur , increases IR exposure

Question 15

__% density variation from anode to cathode

Answer 15

45

Question 16

as distance increases IR exposure

Answer 16

decreases

Question 17

density / IR exposure decreases when filtration is

Answer 17

increased

Question 18

compensating filters require an ____ in technique (mAs)

Answer 18

increase

Question 19

beam restriction (collimation) reduces

Answer 19

the total # of photons, reducing IR exposure & density

Question 20

air ( radiolucent contrast)

Answer 20

increases density/ IR exposure

Question 21

barium / iodine (radiopaque contrast)

Answer 21

decreases density/ IR exposure

Question 22

the more efficient the grid

Answer 22

the less density IR /exposure

Question 23

high grid ratios will

Answer 23

decrease density / IR exposure

Question 24

wide dynamic range “margin of error”

Answer 24

— higher latitude over film screen

Question 25

DQE - detective quantum efficiency is

Answer 25

how efficiently a system converts the incoming x ray into an image - determines the latitude

Question 26

contrast is

Answer 26

the difference in adjacent densities/ IR exposure

Question 27

dynamic range is the concept of

Answer 27

contrast as it is DISPLAYED on a monitor

Question 28

what is the digital processing function on the display that controls the range of brightness / contrast

Answer 28

window width

Question 29

contrast / dynamic range / window width all describe the

Answer 29

grayscale bit depth

Question 30

image contrast is

Answer 30

the amount of contrast acquired from the IR

Question 31

subject contrast

Answer 31

results from the anatomical part being radiographed ( NOT talking about IR)

Question 32

high contrast

Answer 32

black & white , fewer shades of gray (think extremities)

Question 33

low contrast

Answer 33

more shades of grays , long scale

Question 34

the # of useful visible density or shades of gray

Answer 34

scale of contrast

Question 35

short scale is

Answer 35

maximal differences (black & white) high contrast

Question 36

long scale is

Answer 36

minimal differences between densities but maximal total number of densities - low contrast

Question 37

the number of different shades of gray that can be stored and displayed by a computer system - monitor function

Answer 37

gray scale

Question 38

physical contrast

Answer 38

densities/ IR exposures that can be recorded by the IR

Question 39

visible contrast

Answer 39

total range of densities and IR exposure that can be perceived by the human eye

Question 40

term used to describe the ability of an IR to distinguish between objects having similar contrast

Answer 40

contrast resolution

Question 41

increased contrast, low kVp, short (narrow) dynamic range / window width

Answer 41

high contrast

Question 42

decreased contrast , high kVp, large wide dynamic range

Answer 42

low contrast

Question 43

kVp only affects

Answer 43

pre exposure

Question 44

kVp is controlled by

Answer 44

LUT

Question 45

Subject contrast is dependent on

Answer 45

kVp & tissue type/ thickness

Question 46

digital image receptor contrasts primary controller is

Answer 46

window width manipulations

Question 47

asses the range and quality of IR exposures

Answer 47

histogram

Question 48

will produce higher contrast because low energy photons will be absorbed by thicker parts — will not reach IR - more contrast

Answer 48

low kVp

Question 49

Will be able to penetrate more equally and reach IR, thus causing a more uniform image - less contrast

Answer 49

high kVp

Question 50

as body part thickness increases x-ray absorption

Answer 50

increases

Question 51

overall thicker part =

Answer 51

decreased subject contrast

Question 52

overall thinner part =

Answer 52

increased subject contrast

Question 53

mAs affecting contrast; if IR exposure is too high (overexposed) or to low ( underexposed)

Answer 53

contrast will be decreased

Question 54

influencing factors affecting contrast

Answer 54

mAs, focal spot size, anode heel effect, distance, filtration, beam restriction, anatomical part, grid

Question 55

SID - since IR exposure is affected by distance

Answer 55

so is contrast

Question 56

beam restriction

Answer 56

Reduces scatter therefore increases contrast

Question 57

images are improved with a

Answer 57

Larger matrix size with a larger number of pixels

Question 58

The square picture elements making the matrix - individual boxes

Answer 58

pixel