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Radiation protection > chapter 11 EXAM 5 > Flashcards

chapter 11 EXAM 5 Flashcards

1
Q

safety requirements are required for:

A 
tube housing 
xray control panel 
radiographic exam table
source to image distance indicator 
other devices and accessories
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2
Q

xray tube housing requirements

A

lead lined metal tube housing to protect patient and tech from leakage, scatter and off focus radiation

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3
Q

leakage radiation

A

radiation that does not exit form the collimator opening but penetrates the protective tube housing and the sides of the collimator

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4
Q

primary beam (direct radiation, useful beam)

A

radiation that emerges directly from the xray tube and moves without deflection toward a wall, door, etc

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5
Q

the tube housing is constructed so that leakage radiation measured at a distance of what from the xray source does not exceed what when the tube is at it’s highest mAs/Kv

A

1m from the xray source does not exceed 1 mGya/hr

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6
Q

the tube housing also does what

A

it confines high voltage to prevent electric shock

makes cooling of xray tube possible

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7
Q

control panel/console requirements

A

must indicate the conditions of exposure and indicate when xray tube is energized
usually satisfied with use of kVp and mAs

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8
Q

radiographic exam table requirements

A

must be strong and support the pt.

thickness must be uniform and radiolucent to absorb only a minimal amount of radiation

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9
Q

what is the xray table typically made of

A

carbon fiber material

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10
Q

source to image receptor distance indicator requirements

A

can be a tape measure or a laser

distance and centering indicators

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11
Q

distance and centering indicators must be accurate to within what of the SID

A

within 2% and 1% of the SID

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12
Q

t or f

under no circumstances should the xray beam exceed the size of the image receptor

A

true

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13
Q

collimation is accomplished primarily through the use of

A

a light localized, variable aperture collimator

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14
Q

other types of collimators include

A

aperture diaphragms

cones and cylinders

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15
Q

all collimation devices reduce what and improve what

A

scattered radiation and improves image quality

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16
Q

light localizing variable aperture rectangular collimators have 2 sets of adjustable lead shutters they do what

A
  1. reduces the amount of off focus radiaiton

2. consists of 2 pairs that can be adjusted independently

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17
Q

light localizing variable aperture rectangular collimators have

A

a light source and a mirror

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18
Q

skin sparing :
to minimize skin exposure to electrons produced by photon interaction with the collimator, the patient’s skin surface should be at least

A

15 cm below the collimator

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19
Q

space bars

A

some collimators contain space bars to prevent collimators from being closer than 15 cm to the pt.

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20
Q

what is luminance

A

the brightness and quantifies the intensity of a light source

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21
Q

brightness is measured in

A

nit or candela per square meter

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22
Q

a reading of 15 foot candles corresponds to a collimator light source with a lumincance of about

A

161 nit or 161 candela per square meter

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23
Q

the xray beam and the light beam must coincide to within what of the SID

A

within 2% of the SID

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24
Q

Positive Beam Limitation PBL

A

ensures that the radiographic beam is no larger than the IR

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25
Q

PBL was required on all xray systems in the US between the years of

A

1974 and 1994

not required anymore

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26
Q

state regulartoy standards require accuracy of

A

2% of the SID with PBL

some state may require only 3%

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27
Q

aperture diaphragm

A

simplest of all beam limiting devices

rectangular shape is most common and can be used in many systems

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28
Q

cones and cylinders

A

modifications of the aperture diaphragm
restricts the useful beam to the required size
reduce scatter and improve contrast resolution

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29
Q

t or f

sharper size restriction is achieved when the cone or cylinder is longer

A

true

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30
Q

filtration (also called hardening of the xray beam)

A

reduces exposure to patient’s skin and superfical tissue by absorbing most of the lower energy photons
increases the quality of the beam

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31
Q

2 types of filtration

A
  1. inherent filtration

2. added filtration

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32
Q

examples of inherent filtration

A

glass envelope
insulating oil
glass window

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33
Q

the inherent filtration material amounts to about what aluminum equivalent

A

0.5mm aluminum equivalent

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34
Q

the collimator provides an additional inherent filtration of what aluminum equivalent

A

0.1mm aluminum equivalent

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35
Q

added filtration

A

sheets of aluminum or the equivalent that are added to the tube

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36
Q

the inherent filtration and added filtration combine to equal

A

the required amount necessary to filter the useful beam

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37
Q

does the kVp of an xray unit determine the amount of filtration required?

A

yes

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38
Q

the regulatory standard for total filtration of 2.5 mm Aluminum equivalent is required for fixed xray unit operating above

A

70 kVp

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39
Q

because each xray tube and collimator has a total inherent filtration of 1.5mm aluminum equivalent, the manufacturer place and additional

A

1mm Al Eq filter between the tube housing and collimator to meet the minimum regulatory requirement

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40
Q

stationary radiographic equipment operating at 50-70 kVp require a total filtration of

A

1.5 mm Al Eq

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41
Q

stationary radiographic equipment operating below 50 kVp requires a total filtration of

A

0.5mm Al Eq

42
Q

mobile diagnostic units and fluoroscopic equipment requre a minimum filtration of

A

2.5 mm Al Eq

43
Q

what are commonly used as filters in mammography

A

molybdenum and rhodium filters

44
Q

when the xray target is made of molybdenum each of the following filters may be used

A

a 0.3mm molybdenum filter

a 0.025 mm rhodium filter

45
Q

when the xray target is made of rhodium what filter can be used

A

a 0.025 mm rhodium filter

46
Q

as filtration is increased, so is what

but what is decreased

A

the beam quality increases but quantity is decreased

47
Q

Half value layer HVL

A

the thickness of a designated absorber necessary to reduce an xray beam to half of its original intensity

48
Q

for diagnostic beams the HVL is expressed in

A

millimeters of aluminum

49
Q

HVL is the best method for

A

specifying xray quality or effective energy of the xray beam

50
Q

compensating filters

A

devices that partially attenuate xrays directed toward a thinner or less dense area while permitting more xrays to strike the thicker or denser area

51
Q

2 kinds of compensating filters

A
  1. wedge

2. trough

52
Q

exposure reproducibility

A

consistency in output radiation intensity for identical generator settings from one individual exposure to subsequent exposures

53
Q

sequential radiation exposures should be reproducible within

A

+ or - 5%

54
Q

exposure linearity

A

the ability of a radiographic unit to produce a constant radiation output for various combos of mA and time

55
Q

exposure linearity must be within what for adjacent mA stations

A

10%

56
Q

intensifying screens are made up of

A

predominantly rare earth screens

57
Q

intensifying screens

A

convert xray energy into visible light to produce radiographic density on the film
significantly reduces exposure time
enhances film exposure process

58
Q

effect of faster screen film systems on patient dose:

when the speed of screen film systems doubles the radiation exposure is reduced by

A

50%

59
Q

as kV increases, effective screen speed

A

increases

increased kv with less mAs

60
Q

rare earth intensifying screens absorb about how much more energy than their predecessors

A

5x

61
Q

radiographic grids

A

remove scattered radiation before reaching the IR and improves contrast and visibility of detail

62
Q

when are grids used

A

when the pt. body part exceeds 10cm

63
Q

grids always increase what but improve what

A

increase patient dose

improves quality of recorded image

64
Q

an increase in what exposure factor is required with the use of a grid

A

increased mAs

65
Q

as grid ratio increases, patient dose

A

increases

66
Q

grid ratio

A

the ratio of the height of the lead strips in the grid to the distance between them

67
Q

t or f
high ratio grids reduce scatter more effectively than low ratio grids, however, high ratio grids require more radiation exposure increasing patient dose

A

true

68
Q

a source to skin distance of at least what must be used in mobile radiography for patient safety

A

30cm

69
Q

when the source to skin distance is short, the patient’s entrance exposure is

A

significantly greater than the exit exposure

70
Q

decrease in SID increases the

A

source to skin dose

71
Q

the sensitivity of the phosphor used in CR is about equal to a what speed screen film combination

A

200 speed screen film combination

72
Q

kv controls

A

radiographic contrast

73
Q

what are the advantages that DR systems have over both CR and conventional screen film systems

A

lower dose
ease of use
immediate imaging results
manipulation of the image

74
Q

what is a disadvantage to DR systems

A

they don’t allow the user to change the grid or have a preinstalled grid that is not easily accessible to the user

75
Q

fluoroscopic systems inculde

A

xray tube
image intensifier
c arm

76
Q

what are the 3 advantages of image intensification

A
  1. increased image brightness
  2. saving of time for the radiologist
  3. patient dose reduction
77
Q

image intensification requires less milliamperage than old fashioned fluoro. how much mA with image intensification is used

A

1.5-2 mA is used in image intensification

3-5 mA was used before

78
Q

in fluoro the increase in magnification results in a decrease in

A

image clarity and the resulting image is dimmer

79
Q

intermittent of pulsed fluoro significantly decreases

A

patient dose, especially in long procedures

80
Q

integral dose

A

product of dose and volume of tissue irradiated

81
Q

the source to skin distance for stationary fluoro must not be less than
and for mobile fluoroscopes

A 
38 cm
30 cm (mobile)
82
Q

fluoroscopic technical factors for children need a decrease in kVp by as much as

A

25%

83
Q

a minimum of how much filtration must be permanently installed in the path of the useful beam of the fluoroscopic unit

A

2.5 mm Al Eq

84
Q

with image intensification a total of how much filtration should be used

A

a total of 3 mm Al Eq or greater is preferred

85
Q

patient dose decreases by how much during fluoro procedures when aluminum filtration increase from 1 to 3 mm of Al

A

dose decreases by 1/4th

86
Q

when kVp ranges from 80-100 in standard image intensification fluoroscopy, an xray beam HVL of how much is considered acceptable

A

3-4.5

87
Q

cumulative timing device

A

a resettable device that times the dray beam on time that will sound an audible alarm or temporarily interrupt the exposure after it has been activated for 5 mins

88
Q

current federal standards limit entrance exposure rates of general purpose intensified fluoroscopic units to a max of

A

100 mGya per minute

89
Q

entrance exposure rates for fluoroscopy equipment equipped with high level control may produce a skin entrance exposure rate as high as

A

200 mGya per minute

90
Q

high level fluoro is used in what procedures

A

interventional procedures

91
Q

a primary protective barrier of how much is required for a fluoroscopic unit

A

a primary protective barrier of 2mm lead equivalent

92
Q

t or f
the exposure control switch/foot pedal on fluoro units must be the dead-man type AKA only continuous pressure applied by the operator will keep it activated

A

true

93
Q

t or f

image intensifier distance should be as short as possible to reduce patient entrance dose

A

true

94
Q

t or f

cine procedures can result in the highest patient dose of all diagnostic procedures

A

true

95
Q

in cine procedures, when film rates are high so is

A

patient dose

96
Q

when a smaller viewing mode or a lower speed cine film is used, patient exposure

A

increases

97
Q

pulse progressive systems

A

xray beam is turned off while image is being scanned, decreasing dose and pulsed back on for the next image.

98
Q

High level control fluoro HLCF

A

an operating mode in which exposure rates are substantially higher than those normally allowed in routine procedures

99
Q

the higher exposure rate of the HLCF allows

A

visualization of smaller and lower contrast objects that don’t usually appear during routine fluoro

100
Q

in 1994 the FDA limited tabletop exposure rate of fluoroscopic equipment to what?
unless HLC mode was present in which case routine fluoro was limited to what when the system was not in HLC mode and what when it was in HLC mode

A

100 mGya/min

50 mGya/min

unlimited

101
Q

FDA has recommended a notation be placed in the patient’s record if a skin dose in the range of what is received
the location of the area of the pts. skin should also be recorded

A

a dose of 1-2 Gyt

102
Q

since 2000, alarmed state regulatory agencies have imposed a restricition on high level radiation exposure rates with the image intensifier at a distance of 30 cm above the tabletop, the max continous fluoro entrance exposure rate for HLCF is

A

200 mGya / min

Radiation protection (12 decks)

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