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Radiology Vcast05 > chapters 17 and 18 radio physics > Flashcards

chapters 17 and 18 radio physics Flashcards

1
Q

is it ever appropriate to repeat overexposed digital images?

A

no, unless there is analog-to-digital converter saturation

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2
Q

what does saturation cause in an image

A

causes the image to be clipped or burned out

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3
Q

what is data clipping

A

data is removed from the diagnostic range that can’t be recognized b/c it is above or below the diagnostic range
(OCCURS WHEN ADC REACHES SATURATION)

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4
Q

Philips DR uses __________ numbers

A

sensitivity (S)

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5
Q

Agfa CR uses_____________ numbers

A

log median exposure (LgM)

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6
Q

GE DR uses____________ numbers

A

detector exposure index (DEI)

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7
Q

Siemens uses_________ numbers

A

Exposure index (EXI)

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8
Q

what is the relation between S number and the amount of radiation striking the IP

A

the relationship is Inversely proportional

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9
Q

(EDR) exposure data recognizer is what?

A

optimal reading conditions are determined once the auto mode processing processes the image data in the IP

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10
Q

what allows more than one view be exposed on a single IP?

A

(EDR) Exposure data recognizer

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11
Q

what are the VOI (values of interest) for a Fuji

A

full anatomic area

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12
Q

what are the VOI (values of interest) for a Konica

A

recognition of relevant anatomy

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13
Q

how can you balance AEC

A

there are lots of ways b/c every manufacture comes up with different ways

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14
Q

does the EI number or the DI number have a direct relation to patient exposure

A

no there is no relation between EI/DI numbers and patient exposure

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15
Q

deviation index gives what to the technologist?

A

gives feedback to the technologist regarding technique and image quality based on signal-to-nosie ratio

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16
Q

what does a DI (deviation index) of 0 indicate

A

indicates that their is no diff. between the desired EI and the actual EI

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17
Q

diffrent IRs have________ detective quantum efficiency (DQE)

A

diffrent

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18
Q

A high DQE results in ______ noise level

A

lower

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19
Q

what is a usual EI number derived from

A

the mean detector entrance exposure which is derived from the MEAN PIXEL VALUE of the image

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20
Q

what is the dynamic range

A

the number of shades of gray an imaging system can produce

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21
Q

how do you calculate the amount of shades of gray

A

2^# of bit

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22
Q

what kind of function do Digital receptors have in a graph

A

linear receptor response function

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23
Q

CR and DR receptors____________ and does not________

A

can receive any radiation exposure; experience the toe and shoulder limitation of film/screen exposures

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24
Q

areas that receive very little radiation can be enhanced by the _____ instead of being______

A

computer; clumped at the toe

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25
Q

areas that receive greater exposure can be _____ into _____ instead of being _________

A

separated; visible densities; clumped around the shoulder

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26
Q

what = bite depth

A

2^n

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27
Q

how many bits make up a byte

A

8 bits make up 1 byte

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28
Q

spatial resolution

A

the ability to see small objects or fine recorded detail

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29
Q

spatial frequency

A

unit of line pairs per millimeter (ip/mm or in digital # of cycles/mm or micrometer

30
Q

what happens to the image when we have a very high spatial resolution

A

this will increase blur even though the resolution will be better

31
Q

which imaging system has the best spatial resolution

A

mammography 12 IP/mm

32
Q

Modulation transfer function (MTF)

A

responsible for converting contrast values of diff. sized objects into contrast intensity levels in the image

33
Q

what does high spatial frequency create

A

blur; results in reduced modulation- reduced amplitude of the signal

34
Q

as spatial frequency increases what happens to MTF (transfer of object contrast to image contrast)

A

MTF (modulation transfer function) will go decrease

35
Q

I.S spatial resolution is spatial frequency at ___ MTF

A

10%

36
Q

spatial frequency and MTF make up what

A

Spatial resolution

37
Q

in film screen radiography, what is the spatial resolution

A

8 Ip/mm

38
Q

what spatial resolution does mammography have

A

15 Ip/mm (minimal blur)

39
Q

what tool is used to measure spatial resolution in digital

A

lead bar pattern test tool

40
Q

what tool is used to measure spatial resolution in conventional units

A

resolution test tool

41
Q

the___ the # of line pairs the_____ the spatial resolution

A

greater, higher (remember we need a balance of line pairs and MFT)

42
Q

what are the primary factors of spatial resolution

A

matrix size, pixel size and pixel pitch

43
Q

pixel size in relation to spatial resolution

A

the smaller the pixel size the better spatial resolution

44
Q

pixel pitch is what

A

the space from the center of a pixel to the center of the adjacent pixel

45
Q

what does a narrow pixel pitch do to spatial resolution

A

increases spatial resolution

46
Q

what is the spatial resolution for conventional radiography and CR

A

10 Ip/mm, 5Ip/mm (dynamic range makes up for it because it allows more contrast resolution due to its ability to give more detail

47
Q

PSF

A

point spread function function unit (vert. line creates a point when it intersects with the horizontal imaging plane)

48
Q

LSP

A

line spread function unit (vert. line creates a point when it intersects with the horizontal imaging plane)

49
Q

ESF

A

Edge spread function unit (vert. line creates a point when it intersects with the horizontal imaging plane)

50
Q

noise

A

degeneration of image begins with increased image noise (low mAs and kVp create this)

51
Q

a 10x12 IP with 2k pixels will have a ______ spatial resolution than a 7x7 IP with 2k pixels b/c of the pixel size

A

worse

52
Q

Pixel Size (formula)

A

FOV/ Matrix Size

53
Q

DQE (detective quantum Efficiency)

A

is the measurement of x-ray absorption efficiency

54
Q

what does high DQE do to patient dose

A

it should decrease patient dose

55
Q

what is the speed class (DQE)

A

reflection of the amount of light (PSP); the level of exposure received by the IP (THE MEASURE OF X-RAY ABSORPTION EFFICIENCY)

56
Q

a luminescent level of 200= how much speed class

A

200 speed class

57
Q

what happens when speed class increases in relation to noise

A

noise will increase (b/c kVp is increased and mAs Isi decreased causing desist fluctuations as speed class increases

58
Q

the exposure index is ______ proportional to the speed class of operation

A

indirectly proportional

59
Q

E.I increased from 1400 to 1700 the speed class is ______ from 400 to ______

A

reduced, 200

60
Q

image noise is what

A

a fluctuation is density/ overall brightness

61
Q

if the signal is higher than the noise this will = ?

A

better spatial resolution

62
Q

S/N; 10/1= 10

A

good spatial resolution

63
Q

S/N; 1/10= .1

A

bad spatial resolution

64
Q

what specific part of the dynamic range controls contrast resolution in DR?

A

the ADC via the bite depth (2^n)

65
Q

does mAs affect contrast resolution?

A

yes mAs does have an effect on contrast resolution

66
Q

what process ensures that unnecessary info., such as scatter, outside the collimated edges become eliminated from the histogram analysis

A

(PRIEF) pattern recognizer for irradiated exposure field

67
Q

Auto mode processing?

A

allows IP image data to be sampled and used by the EDR

68
Q

what determines the range of the histogram data that should be included in the displayed image

A

VOIs

69
Q

a value that reflects the diff. between the desired or target exposure to the IR and the actual exposure to the IR is the

A

deviation index

70
Q

DI (deviation index) above 0=

A

increased exposure

71
Q

DI (deviation index) below 0=

A

decreased exposure

Radiology Vcast05 (18 decks)

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