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Radiologic Physics > for the final > Flashcards

for the final Flashcards

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1
Q

sampling breaks an image into _____

A

pixels

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2
Q

a byte consists of ______ bits

A

8

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3
Q

bit depth determines the imaging systems _____

A

contrast resolution

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4
Q

as spatial frequency increases, spatial resolution _____

A

increases

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5
Q

as matrix size gets bigger, spatial resolution _____

A

increases

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6
Q

a 4-bit system would display ___ shades of gray?

A

16

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7
Q

digital fluoroscopy systems with hybrid capabilities use both _____

A

temporal and energy subtraction

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8
Q

the computed radiography image has

A

Wide exposure latitude and improved contrast resolution

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9
Q

the dynamic range determines the degree of _____ in the image.

A

contrast resolution

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10
Q

an increase in mAs

A

effect on x-ray energy: none
x-ray intensity: increased

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11
Q

an increase in kVp

A

effect on x-ray energy: increased
x-ray intensity: increased

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12
Q

an increase in distance

A

effect on x-ray energy: none
x-ray intensity: reduced

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13
Q

an increase in filtration

A

effect on x-ray energy: increased
x-ray intensity: reduced

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14
Q

the number of gray shades that an imaging system can reproduce is called its

A

dynamic range

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15
Q

each pixel of information in the CT image contains numerical information in ____ units

A

Hounsfield

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16
Q

the CT scanner must be calibrated so that the CT number for water is zero?

A

True

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17
Q

a pixel is

A

2-d image cell

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18
Q

as signal-to-noise increases, image quality

A

increases

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19
Q

if an image receptor has a high probability of interacting with the x-ray beam, then it

A

DQE - detective quantum efficiency

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20
Q

the ability to distinguish different shades of gray or brightness levels is called?

A

contrast resolution

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21
Q

as spatial resolution increases, lp/mm

A

increases

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22
Q

currently, the imaging modality with the highest spatial resolution

A

mammography

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23
Q

when doing soft tissue radiography, the differential absorption between _____ and _____

A

glandular;fat;muscle

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24
Q

Which has the lowest spatial resolution?

A

Nuclear Medicine or Sonography

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25
Q

image noise limits

A

contrast resolution

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26
Q

Which of the following is a high contrast modality.

A

C.

A. CT
B. MRI
C. radiography
D. All of the above

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27
Q

the highest occupational exposure of diagnostic x-ray personnel occurs during

A

fluoroscopy

28
Q

In digital radiography images are made up of discrete picture elements called?

A

pixels

29
Q

the greater the dynamic range, the better the contrast resolution.

A

True

30
Q

computed tomography has better ______ resolution than radiography.

A

contrast

31
Q

For the digital image, the grid of rows and columns is called

A

matrix

32
Q

The process of creating a series of pixels is called?

A

sampling

33
Q

increasing the sampling rate…

A

increases spatial resolution

34
Q

In digital radiography, spatial resolution is improved with increased

A

matrix size

35
Q

The larger the voxel the ___________ the spatial resolution.

A

voxel size doesn’t affect

36
Q

Spatial frequency is used to describe the quality of spatial resolution in terms of _____________

A

line pairs

37
Q

image detail is also called

A

spatial resolution

38
Q

Of all radiographic imaging systems, _____________ has the best contrast resolution

A

CT
has the best contrast resolution of all x-ray imaging systems because of x-ray beam collimation and the resultant reduction in scatter radiation

39
Q

The image intensifier improved fluoroscopy by increasing

A

image brightness

40
Q

The _______ in the retina are stimulated by _______ light; the _______ are stimulated by _______ light.

A

rods, low; cones, bright

41
Q

The principal drawback of the first-generation CT scanner was the _______________

A

long scanning time

42
Q

The third generation of CT scanners allowed for further reduction in _____________

A

scanning time and scattered radiation

43
Q

CT imaging has excellent ______________ because of the narrow beam collimation

A

contrast resolution

44
Q

Each sweep of the source-detector around the body during CT is called a __________

A

translation

45
Q

As discussed in class, an advantage of digital fluoroscopy is it ________________ patient radiation dose

A

decreases

46
Q

Noise can affect image quality in what way?

A

decreased contrast resolution

47
Q

As image noise decreases, contrast resolution…….

A

increases

48
Q

Quantization is the same as sampling.

A

False

49
Q

As DQE is increased, the amount of radiation necessary to produce an image ______________

A

decreases

50
Q

Bit depth determines the imaging systems ……

A

contrast resolution

51
Q

DF have faster image acquisition and _______ to enhance image contrast.

A

post processing

52
Q

The higher the spatial frequency, the ______ the spatial resolution

A

HIGHER

53
Q

Select all of the following which can image in ‘realtime’?

A

fluoroscopy and sonography

54
Q

An imaging system bit depth determines what aspect of image quality?

A

contrast resolution

55
Q

Perfusion is associated with which imaging modality?

A

SPECT

56
Q

A gamma camera records…

A

gamma rays

57
Q

The only difference between x-rays and gamma rays is their ____.

A

origin

58
Q

Which modality utilizes rectangular pixels?

A

MRI

59
Q

Perfusion imaging is typically done by which modality?

A

SPECT

60
Q

Of the following, which is the dominant radioisotope used in NM?

A

technicium

61
Q

Today, new MR scanners are typically

A

3.0 Tesla

62
Q

Which of these are contrast materials/media for radiography and CT?

A

barium and iodine

63
Q

more shades of gray is

A

better contrast resolution

64
Q

Requires the highest spatial resolution of ALL imaging modalities

A

Mammography

65
Q

____ resolution image loses detail; _____ resolution image shows detail

A

low; high

Radiologic Physics (6 decks)

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