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Radt. 3011 > Exam 4 Ch 36- Design for Radiation Protection > Flashcards

Exam 4 Ch 36- Design for Radiation Protection Flashcards

1
Q

more than ______ are associated w: modern x-ray equipment-

A

100 individual radiation protection features

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2
Q

many protection features are specific to-

A

radiography or fluoro

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3
Q

2 radiographic protection features for radiography & fluoroscopy-

A

tube housing & control panel

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4
Q

tube housing must reduce leakage radiation to-

A

less than 1 mGA/hr @ distance of 1m

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5
Q

job of tube housing-

A

protect tube

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6
Q

leakage radiation-

A

radiation that exits tube at any place other than window/useful beam

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7
Q

control panel protection feature must identify-

A

-conditions of exposure (kVp & mA indicators)
-positively indicate when tube is energized (visible/audible)

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8
Q

SID Indicator protection feature must-

A

-be present
-be accurate within 2% of SID

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9
Q

collimation protection feature-

A

-light-localized variable-aperture rectangular collimation should be provided
-must be within 2% of SID

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10
Q

attenuation of useful x-ray beam must be equal to-

A

attenuation of protective housing

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11
Q

PBL protection features-

A

-auto. collimator
-must be accurate to 2% of SID
-no longer required, but is common in new sys.

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12
Q

beam alignment protection features-

A

IR must be aligned w: center of primary beam

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13
Q

total filtration (inherent + added) must be at least-

A

-2.5 mm Al above 70 kVp
-1.5 mm Al b/w 50-70 kVp
-.5 mm Al for tubes below 50 kVp

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14
Q

filtration for most diagnostic sys. used today-

A

have at least 2.5 mm Al

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15
Q

reproducibility should be-

A

-constant from one exposure to another/reproduce the same image using the same factors multiple times
-shouldn’t exceed 5% intensity change

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16
Q

linearity protection features-

A

-adjacent mA stations (when time is adjusted to maintain mAs) should produce same intensity
-shouldn’t exceed 10% change in intensity
-refers to the proportional accuracy of the output of the mA station in relation to another

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17
Q

linearity ex-

A

output of 100 mA station should be double output of 50 mA station

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18
Q

operator shield protection features-

A

-design of console should prevent exposure by tech. while in room
-exposure button should be fixed

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19
Q

mobile x-ray imaging system protection features-

A

-lead apron should be assigned to each portable machine
-exposure switch must be on a cord
-useful beam MUST be directed away from tech

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20
Q

length of the cord of the exposure switch on a mobile x-ray imaging sys.-

A

at least 2 m in length (6ft)

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21
Q

fluoro beam intensity at table top-

A

-20 mGya/min for each mA of operation @ 80 kVp
-no high level control- 100 mGya/min
-w: high level control- 200 mGya/min

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22
Q

as source to skin distance (SSD) increases, what decreases?

A

entrance skin exposure

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23
Q

source to skin distance (SSD) must not be-

A

-stationary fluoro- not less than 38cm (15”)
-mobile fluoro- not less than 30cm (12”)

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24
Q

fluoro Primary Protective barrier-

A

image intensifier

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25
Q

fluoro total filtration-

A

no less than 2.5 mm Al equivalent

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26
Q

fluoro collimation-

A

must be visible on the monitor

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27
Q

fluoro exposure control must be ___ type-

A

dead-man type (requires constant pressure for it to engage)

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28
Q

fluoro bucky slot cover-

A

must be 0.25mm Pb equiv. (made of led)

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29
Q

fluoro protective curtain must be-

A

at least 0.25 mm Pb equiv.

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30
Q

fluoro cumulative timer-

A

audible signal to denote 5 min. beam on timer

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31
Q

design of protective barriers considerations-

A

adjacent rooms & floors in rad. facilities

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32
Q

2 types of protective barriers-

A

primary & secondary

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33
Q

primary protective barriers are-

A

any wall to which useful beam CAN be directed to is designated a PPB

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34
Q

NCRP report #49-

A

detail structural design requirements

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35
Q

in fluoro ____ is a primary protective barrier-

A

image intensifiers

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36
Q

primary protective barriers required size-

A

-1/16 of an inch of led/led equiv.
-at least 7 ft. high

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37
Q

secondary protective barriers considerations-

A

-any wall, floor, or ceiling that could have scatter or secondary radiation incident on it
-should never aim primary beam at console

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38
Q

______, ______, & _____ are considered for secondary protective barriers-

A

scatter, secondary, & leakage radiation

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39
Q

__________ is ALWAYS ONLY behind secondary protective barriers-

A

operating consoles

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40
Q

secondary protective barriers required size-

A

-1/32 of an inch of led/led equiv.
-no height requirement

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41
Q

factors affecting barrier thickness (6)-

A

-distance
-adjacent room occupancy
-control
-workload
-use factor
-kVp

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42
Q

distance from source to barrier decreases-

A

required thickness increases

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43
Q

adjacent room occupancy increases-

A

required thickness increases

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44
Q

full adjacent room occupancy-

A

work areas

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45
Q

frequent adjacent room occupancy examples-

A

corridors, restrooms, patient rooms

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46
Q

occasional adjacent room occupancy ex-

A

waiting rooms, stairwells, outside areas, & janitor’s closet

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47
Q

controlled areas occupied by-

A

mostly by rad. personnel & pts.

48
Q

controlled areas barriers must reduce exposure rate to-

A

less than 1 mSv/wk (100 mrem/wk)

49
Q

uncontrolled areas-

A

occupied by anyone

50
Q

uncontrolled area barriers must reduce exposure rate to-

A

less than
-1 mSv/wk
-20 uSv/wk
-2mrem/wk

51
Q

workload increases-

A

barrier thickness increases

52
Q

use factor-

A

amt of time beam is energized & directed toward barrier

53
Q

what do many physicists say ab all barriers-

A

all barriers are secondary bec useful beam is always intercepted by pt. & IR

54
Q

kilovolt peak increases-

A

barrier thickness increases

55
Q

Radiation detection & measurement-

A

devices that detect, measure, or both

56
Q

radiation detection & measurement devices operate in-

A

pulse or rate mode

57
Q

pulse mode detects-

A

presence

58
Q

rate mode expressed in-

A

-mGya/hr
-mR/hr

59
Q

integrate mode-

A

detects & measures TOTAL amount of intensity of radiation

60
Q

why are radiation detection & measurement devices called dosimetry?

A

they use dosimeters

61
Q

types of dosimeters (4)-

A

-gas-filled detectors
-schintillation detectors
-TLDs
-OSL detectors

62
Q

3 types of gas-filled detectors-

A

-ionization chambers
-proportional counters
-geiger-muller detectors

63
Q

in gas- filled detectors, the gas in the chamber is maintained-

A

at constant voltage (voltage changes when hit w: x-radiation)

64
Q

any electrons liberated by x-radiation are-

A

detection & measurement

65
Q

measurement of electrons in gas-filled detectors are proportional to-

A

radiation intensity

66
Q

the larger the gas chamber-

A

the more sensitive the device

67
Q

pressurized chambers are-

A

more sensitive

68
Q

accuracy of gas-filled detectors depends on-

A

the design of the instrument

69
Q

voltage in gas chamber will-

A

increase in stages

70
Q

voltage in gas chamber increasing in stages, the stages represent-

A

gas filled stages detected

71
Q

R- region of recombination-

A

ions created don’t migrate toward central cathode

72
Q

Ion chamber Region-

A

every electron released is attracted to central electrode & collected

73
Q

Ion chamber regions operate at-

A

b/w 100-300 volts

74
Q

ion chambers used for-

A

detection & calibration

75
Q

proportion region-

A

voltage increases, electrons traveling to central electrode will create secondary electrons

76
Q

proportional region creates-

A

large electron pulse

77
Q

proportional detectors can distinguish b/w-

A

alpha & beta radiation

78
Q

Geiger Muller Region-

A

for every single ionization event, nearly all molecules of gas in the chamber are ionized

79
Q

for sequential detection in GM region-

A

counters must have an added quenching agent added to filling gas

80
Q

resolving time-

A

time required for gas to return to original condition

81
Q

Continual Discharge Region (CD)-

A

w: increased voltage, chamber reaches this point

82
Q

CD region no longer useful for-

A

detection

83
Q

continued operation in CD region will-

A

damage detector

84
Q

scintillation detector-

A

certain materials exhibits/emits light under the influence of x-rays

85
Q

scintillation detectors in CT & Nuclear Medicine-

A

gamma cameras

86
Q

amt. of light produced in scintillation detectors is proportional to-

A

energy absorbed

87
Q

activator atoms-

A

thallium

88
Q

thallium added to-

A

cesium iodide & sodium iodide

89
Q

scintillation detectors coated w:-

A

polished aluminum on all sides except the window

90
Q

hermetic seal-

A

aluminum also seals crystals from air & moisture

91
Q

crystals are hygroscopic-

A

-absorbs moisture if not sealed
-will swell, crack, & become less accurate

92
Q

light is incident on a-

A

photocathode made of cesium, antimony, & bismuth

93
Q

the number of electrons emitted in scintillation detectors are proportional to-

A

intensity of light

94
Q

electrons in scintillation detectors are accelerated to-

A

dynodes that amplify intensity by secondary electron production

95
Q

in scintillation, the detectors tube gain is-

A

dynode gained raised to the # of dynodes in the tube

96
Q

last element in scintillation detectors-

A

collecting electrode or collector

97
Q

scintillation detectors overall-

A

x-ray or gamma-light-electrons signal

98
Q

scintillation detectors used in x-ray (3)-

A

-cesium iodide
-sodium iodide
-gallenium occulosulfide

99
Q

cesium iodide-

A

most commonly used

100
Q

sodium iodide-

A

commonly used

101
Q

gallenium occulosulfide mainly in-

A

fluoro (in cathode intensifiers)

102
Q

TLDs-

A

material that glows when heated after irradiation

103
Q

in a TLD, subsequent light released is measured w:-

A

photomultiplier

104
Q

lithium fluoride in TLDs are-

A

most common

105
Q

in TLD, calcium fluoride activated w:-

A

manganese, which makes it more sensitive

106
Q

TLD can measure doses-

A

less than 50 uGya (5mrad)

107
Q

TLDs available-

A

different size & forms

108
Q

TLDs are-

A

-reusable
-responds proportionally
-rugged
-accurate

109
Q

optical stimulated luminescence detector developed-

A

in late 1990’s

110
Q

OSL detector uses-

A

aluminum oxide

111
Q

in an OSL, irradiation causes-

A

electrons to be raised to excited state

112
Q

in an OSL, laser light causes-

A

electrons to return to normal when visible light is released

113
Q

OSL detector minimal reportable dose/precision-

A

10 uGya (1 mrad)

114
Q

optical stimulated luminescence detector allows for-

A

reanalysis

115
Q

OSL detector-

A

-exposure condition information
-wide range dynamic
-long term stability
-DOES NOT PROVIDE ANY PROTECTION (acts as snitch)

Radt. 3011 (13 decks)

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