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Radiology Imaging III > Chapter 11 Equipment Design for Radiation Protection > Flashcards

Chapter 11 Equipment Design for Radiation Protection Flashcards

1
Q

What kind of radiation does the tube housing protect the patient and personnel from?

A

off focus or leakage radiation

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2
Q

What does the tube housing prevent?

A

electrical shock, damage to rough handling, helps with cooling of the tube

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3
Q

What is the tube housing lined with?

A

lead

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4
Q

Off focus radiation creates what?

A

ghosting

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5
Q

The limit of off focus radiation for the tube housing is to not exceed ____ one meter away at highest voltage

A

.88 mGya/hr (100 mR/hr)

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6
Q

Who required an audible sound and visible radiation symbol?

A

Radiation Control for Health and Safety Act of 1968

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7
Q

What is required of radiographic tables and why?

A

must be as radiolucent as possible so that it will absorb only a minimal amount of radiation reducing the patients radiation dose

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8
Q

What are the radiographic tables made of?

A

carbon fiber material

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9
Q

The _____ to IR is the source to image receptor distance indicator

A

anode focal spot

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10
Q

The accuracy of the indicator must be accurate within ____ of the indicated SID and centering must be within _____ of SID indicator

A

2%
1%

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11
Q

How large should the primary beam be?

A

collimated to no larger than the size of the IR

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12
Q

Image quality is increased when collimating by _____ the amount of ______ radiation

A

decreasing
scatter

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13
Q

What were earlier collimation devices made of?

A

Cones and cyllinders

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14
Q

This is the automatic or manual collimator that is used on digital units today

A

light localizing variable aperture rectangular collimator

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15
Q

The first set of shutters is ____ to the tube window and ____ off focus radiation but ______ do anything to reduce primary beam

A

close
reduces
does not

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16
Q

The second set of shutters is the ____ ____ type and is _____ on the underside of the collimator head when looking at the light

A

variable aperture
visible

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17
Q

The patient skin surface should be at least _____ below the collimator head on fixed units and _____ on mobile units

A

15cm
30cm

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18
Q

______ refers to the brightness of a surface and quantifies the intensity of light source

A

luminance

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19
Q

The unit of measure is ____ for luminance

A

nit - candela per square meter, intensity measured at 40” should be 15 foot-candles = 161 nit

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20
Q

Coincidence between radiographic beam and localizing light beam must be within ____ of SID

A

2%

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21
Q

This must ensure that the collimation is adequate by collimating the radiographic beam so that it is no larger than the IR

A

positive beam limitation

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22
Q

The state requirements for the positive beam limitation is _____ of the SID

A

2-3%

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23
Q

______ reduces exposure to patient skin and superficial tissue by absorbing most lower-energy photons, increases beam quality and test rid of soft rays

A

filtration

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24
Q

Filtration is also referred to as

A

hardening the beam

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25
Q

reducing exposure to the skin ______ absorbed dose

A

decreases

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26
Q

What are the two types of filtration?

A

inherent and added

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27
Q

Where is inherent filtration?

A

glass envelope, insulating oil, glass window

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28
Q

What is the normal aluminum equivalency, light localizing collimator equivalency and minimum aluminum filtration?

A

.5mm
1mm
1.5mm

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29
Q

1.5mm equivalent aluminum filtration is also called

A

intrinsic filtration

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30
Q

Added filtration is located _____ the glass envelope but _____ the collimator shutters

A

outside
above

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31
Q

inherent + added = ______

A

total filtration

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32
Q

70 kVp and above is ____ AI Eq
50-70 kVp is _____ AI Eq
below 50 kVp is _____ AI Eq

A

2.5mm
1.5mm
.5mm

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33
Q

Aluminum has an atomic number of

A

13

34
Q

Aluminum ______ low energy photons from a poly energetic beam without severely _____ the intensity of the beam

A

removes
decreasing

35
Q

Why is aluminum used?

A

lightweight, sturdy, inexpensive, easily available

36
Q

Quality assurance test to check filtration, thickness of absorber to decrease the intensity of the primary beam by 50%, measure of beam quality

A

half value layer

37
Q

The _____ act of _____ required to have adequate filtration in all tubes

A

Radiation Health and Safety Act of 1968

38
Q

kVp _____ determines the amount of required filtration

A

potential

39
Q

Compensating filters help with dose _____ and provides ______, made up of aluminum or lead acrylic

A

reduction
uniformity

40
Q

What are the two types of compensating filters and where do they go?

A

wedge - foot
trough - chest

41
Q

The thick part of the compensating filter goes over the ____ part of the body

A

thin

42
Q

The function of a compensating filter is to even out ______ of the body part with different _______, helps with dose reduction and uniformity

A

densities
thicknesses

43
Q

Consistency of exposures of same technique set throughout the day, variance of _____ or less is acceptable

A

exposure reproducibility
5%

44
Q

must be less than .1 (10%), consistency in output radiation intensity at selected kVp settings when generator settings are changed from one mA and time setting to another

A

exposure linearity

45
Q

Radiographic grids are used to _____ image quality and _____ scatter

A

improve
reduce

46
Q

Grids use _____ dose

A

more

47
Q

_____ grid ratios increase the patient dose

A

higher

48
Q

Virtual grids work in post processing by the system removing _____

A

scatter

49
Q

In mobile radiography at least _____ source to skin distance is required

A

30cm (12”)

50
Q

When the SSD is small, the patient entrance exposure is significantly ______ than exit exposure

A

greater

51
Q

The larger the image matrix and smaller the individual units the ______ the resolution

A

better

52
Q

The size of a pixel is about ____micrometers

A

50

53
Q

What are the three materials used for image receptors

A

amorphous silicon - scintillator that converts x-ray energy to visible light
charge coupled device - converts visible light into electrical signals
amorphous selenium - converts x-ray directly into electrical signals

54
Q

What are advantages to digital imaging

A

lower dose
ease of use and faster exams
immediate images
image manipulation

55
Q

What are disadvantages to digital imaging

A

more costly
one IR size

56
Q

The computed radiography plate is made of _____

A

europium activated barium fluorohalide phosphors

57
Q

_____ ______ is the process of using automatic settings leading to an increased dose because you are not paying attention to exposure index numbers

A

dose creep

58
Q

____ is more sensitive to scatter so grids should be used ____ often

A

CR
more

59
Q

_____ produces the greatest patient exposure rate in diagnostic radiology

A

fluoroscopy

60
Q

What are three benefits of fluoroscopy

A

brighter image
low mA
image intensifier tubes

61
Q

How much brighter are fluoroscopy tubes

A

10,000 times

62
Q

how low can mA settings go during fluoro

A

new systems 1-1.5 mA
old systems 3-5 mA

63
Q

What are the two multi field or magnification phosphors and what are they made of?

A

input phosphor - cesium iodide
output phosphor - zinc cadmium sulfide

64
Q

magnification produces a smaller area but causes it to be more magnified which ______ the mA

A

increases

65
Q

magnified images have more of an ____ appearance so there is _____ noise

A

even
less

66
Q

the ____ _____ _____ feature should be used to reduce patient and personnel dose

A

last image hold

67
Q

for pulsed and interrupted fluoroscopy the kVp increases, the tube SSD should for fixed units should be no less than _____ and ____ for mobile units

A

38cm
30cm

68
Q

The half value layer for pulsed and interrupted fluoroscopy should be ____ aluminum for 80-100 kVp

A

3mm-4.5mm

69
Q

_____ ______ _____ is an alarm that is sounded after 5 minutes of Fluoro time, all fluoroscopy time should be documented at the end for physician and radiologist

A

cumulative timing device

70
Q

The exposure rate limitations for entrance skin exposure should be ______ per minute at 30cm

A

88 mGya (10 R)

71
Q

The fluoroscopy exposure control switch is what type of switch

A

dead man

72
Q

The image intensifier should be _____ to the patient to reduce scatter

A

as close as possible

73
Q

Weakest scatter is _____ in relation to the patient

A

on top of the patient

74
Q

What is used in vascular imaging

A

digital subtraction angiography

75
Q

reference image of the same area before contrast is administered

A

mask

76
Q

remove of overlying structures to view vessels more clearly

A

roadmapping

77
Q

When are high level control interventional procedures done

A

catheters, vascular type studies, fluid drainage, occlusions

78
Q

visualization of smaller and lower contrast objects requires a ______ exposure rate

A

higher

79
Q

When did the FDA issue warnings about high level control fluoro

A

1974

80
Q

in 1994 the FDA limited table top exposure rates to _____

A

100 mGy/minute (10 R/min)

Radiology Imaging III (12 decks)

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