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Radt. 3011 > Exam 3 Ch 21- Medical Image Descriptors > Flashcards

Exam 3 Ch 21- Medical Image Descriptors Flashcards

1
Q

Medical image quality-

A

refers to fidelity with which anatomy under investigation is rendered

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2
Q

spatial resolution-

A

-ability to image small objects that have high subject contrast
-improves with smaller pixel size

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3
Q

contrast resolution-

A

ability to distinguish anatomical structures of similar subject contrast such as liver-spleen & gray matter-white matter

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4
Q

pixel-

A

element of the picture

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5
Q

Dell

A

detector element

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6
Q

noise-

A

random fluctuation of x-ray interaction on the IR
(simplified version- signal not caused by the subject)

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7
Q

quantum mottle-

A

reduced with the use of high mAs & low kVp

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8
Q

speed medical imaging quality rules-

A

-fast IR- high noise & low contrast resolution
-slow IR- low noise & high contrast resolution
-spatial resolution is limited to pixel size

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9
Q

preferred technique-

A

high kVp & low mAs to reduce pt. dose

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10
Q

3 types of radiographic quality-

A

-IR Factors
-Geometric Factors
-Subject Factors

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11
Q

IR Factors-

A

pixel size, dynamic range, intensity response, signal to noise, & post-processing

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12
Q

Geometric Factors-

A

magnification, distortion, & focal-spot blur

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13
Q

Subject Factors-

A

contrast, thickness, density, atomic #, & motion

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14
Q

magnification-

A

ability of system to draw/render image at appropriate size

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15
Q

What is the magnification factor (MF) formula?

A

image size / object size

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16
Q

When OID increases, what also increases?

A

magnification & distortion increase

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17
Q

Which exams does magnification occur on?

A

all exams

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18
Q

What is the formula used when the actual measurement of an object size may be impossible?

A

MF = SID / SOD

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19
Q

When minimizing MF, what does a large SID do?

A

when SID increases, magnification decreases

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20
Q

When minimizing MF, what does a small OID do?

A

when OID increases, it also increases magnification & distortion

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21
Q

What is shape distortion caused by?

A

positioning the tube/part, or IR is angled

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22
Q

distortion is concerned with-

A

with the part being imaged being unequal shape & size

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23
Q

3 things distortion depends on-

A

-object thickness
-shape
-position

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24
Q

foreshortening-

A

angled IR against a part

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25
Q

elongation-

A

angled IR against the tube

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26
Q

Teleradiology

A

sending images over a phone line

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27
Q

Telerinkenology

A

long range radiology (x-rays at 72”)

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28
Q

What does magnification distortion reduce?

A

image quality

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29
Q

thick objects are more ____ than thin objects

A

distorted

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30
Q

proper positioning is important because-

A

irregular shapes appear more distorted when outside the center of the CR

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31
Q

Objects that are further from the IR or Inclined (tilted back) objects aren’t centered correctly & can present with-

A

distortion

32
Q

2 types of blur-

A

focal spot & motion

33
Q

focal-spot blur has to do with-

A

the shape of FS & the location on the IR relative to FS

34
Q

because of effective spot, the way it works is due to-

A

line focus principle

35
Q

What do you do to get a small affected FS?

A

angle the anode face

36
Q

the beam diversion of 1 source would cause FS itself to-

A

diverge

37
Q

presentation of projected FS will have-

A

different shapes depending where it lands on a rectangular IR

38
Q

____ will have the least amount of blur because of FS location relative to the IR-

A

anode side & center

39
Q

____ will have the most amount of blur because of FS location relative to the IR-

A

cathode side & not center

40
Q

helps reduce blurring on edges of anatomy-

A

short OID

41
Q

an increased OID is equal to-

A

a decreased SOD

42
Q

reduce FS blur-

A

short OID & centering

43
Q

subject factors- (5)

A

-subject contrast
-part thickness
-tissue mass density
-effective atomic #
-object shape

44
Q

the key to radiographic contrast

A

subject contrast

45
Q

helps display subj. contrast-

A

contrast capabilities of the IR, system, & monitor

46
Q

where is subject contrast inherent?

A

in the subject

47
Q

as part thickness increases-

A

-scatter & technique increase
-transmission decreases

48
Q

tissue mass density-

A

photoelectric effect affected by atomic #

49
Q

when the effective atomic # is high, contrast is-

A

contrast is high

50
Q

transmitted x-rays demonstrated on a radiograph are-

A

black

51
Q

relative to cortical bone, on a radiograph soft tissue will show up-

A

black

52
Q

photoelectric effect is demonstrated on a radiograph as-

A

white

53
Q

job of contrast media-

A

artificially influence subject contrast

54
Q

the base of all imaging is-

A

subject contrast

55
Q

iodine Z#-

A

53

56
Q

barium Z#-

A

56

57
Q

Iodine & barium alter-

A

subject contrast to increase contrast

58
Q

when the Z# is high & increases, photoelectric effect-

A

increases rapidly

59
Q

2 types of contrast-

A

positive & negative

60
Q

site contrast-

A

iodine & barium

61
Q

iodine & barium shows up _____ on a radiograph

A

white

62
Q

as photoelectric effect increases, transmission ____.

A

decreases

63
Q

object shape-

A

the more the shape coincides with the x-ray beam, the greater the contrast

64
Q

the closer the shape of the object is closer to beam divergence at the level you’re imaging at, you’re going to get the least amount of-

A

least amount of distortion & blur demonstrated

65
Q

2 types of motion blur-

A

voluntary & involuntary

66
Q

voluntary motion-

A

movement from the patient such as breathing

67
Q

how can you reduce voluntary motion in a radiograph?

A

give good patient instructions

68
Q

involuntary motion-

A

peristalsis or the heart beating

69
Q

how can you reduce involuntary motion in a radiograph?

A

short exposure times

70
Q

reduce the likely hood of motion- (5)

A

-large SID
-reduced OID
-short exposure time
-good patient instructions
-immobilization devices

71
Q

tools for improving image quality- (5)

A

-proper patient positioning
-AP v. PA
-AEC selection
-good patient instructions
-breathing instructions

72
Q

method to improve image quality-

A

proper positioning of the entire patient so the part being imaged is displayed properly

73
Q

principle of imaging-

A

want the part of interest as close to IR as possible

74
Q

image receptor-

A

pixel size affects the patients relative dose

75
Q

small pixels require-

A

higher dose

76
Q

large pixel requires-

A

lower dose

77
Q

good technical factors selection-

A

high kVp aids in short exposure times & overall reduces patient dose & improves image quality

Radt. 3011 (13 decks)

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