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Rad Bio > Chapter 11 > Flashcards

Chapter 11 Flashcards

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1
Q

Measures must be taken to ensure that radiographic equipment operates safely to protect:

A

Patients
All personnel

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2
Q

Every diagnostic imaging system must have a:

A

Protective tube housing
Correctly functioning control panel

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3
Q

What type of tube housing is required to protect the patient

A

Lead-lined metal

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4
Q

Lead-lined metal housing protects the patient and personnel from what type of radiation

A

Off-focus or leakage

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5
Q

What is off-focus radiation

A

Radiation that is not useful - outside of the primary beam

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6
Q

What is the maximum leakage radiation allowed at 1m from the x-ray source

A

1 mGy/hr (100 mR/hr)

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7
Q

Where is the control panel located?

A

Behind a suitable protective barrier that has a radiation-absorbent window

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8
Q

Control panel must indicate the conditions of exposure and provide a ______ indication when the x-ray tube is energized

A

Positive

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9
Q

Control panel must have visible ___ and ___ digital readouts

A

mA and kVp

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10
Q

Radiographic examination table is frequently made of _______________ material

A

Carbon fiber

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11
Q

How is SID measured

A

From anode focal spot to the IR

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12
Q

SID distance and centering indicators must be accurate to within ___% and ___% of the SID, respectively

A

2% distance
1% centering

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13
Q

How is the x-ray beam limited to the size of the IR

A

Light-localizing variable-aperture rectangular collimator

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14
Q

Types of x-ray beam limitation devices

A

Light-localizing variable-aperture rectangular collimator

Aperture diaphragms

Cones

Cylinders

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15
Q

Benefit of restricting x-ray field size to include only the anatomic structures of clinical interest

A

Significant reduction in patient dose because less scatter radiation is produced

Improves the overall quality of the image

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16
Q

Simplest of all beam limitation devices

A

Aperture diaphragms

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17
Q

What x-ray beam limitation device is used most in dental radiography

A

Cones

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18
Q

What types of cones are used for limitation devices

A

Flared metal tubes and straight cylinders

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19
Q

Purpose of filtration

A

Removes low-energy photons (long wavelength or “soft” xrays) by absorbing them

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20
Q

Minimum total filtration required for radiographic units operating above 70 kVp

A

2.5mm Al eq

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21
Q

Types of filtration used for mammographic equipment

A

Molybdenum and rhodium

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22
Q

The thickness of a designated absorber required to decrease the intensity of the primary beam by 50% of its initial value

A

Half-value layer

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23
Q

Who measures the half-value layer to verify the x-ray beam is adequately filtered

A

Radiologic physicist

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24
Q

How often must the HVL be measured

A

Annually and after an x-ray tube is replaced or repairs have been made on the housing or collimation system

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25
Q

HVL is expressed in:

A

mm of Al

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26
Q

HVL is a measure of beam:

A

Quality

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27
Q

Compensating filters are made of

A

Aluminium
Lead-acrylic

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28
Q

Types of compensating filters

A

Wedge
Trough

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29
Q

Consistency in output in radiation for identical generator settings from one indvidual exposure to subsequent exposures

A

Exposure reproducibility

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30
Q

What is the variance percentage for exposure reproducibility

A

5% or less

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31
Q

How is reproducibility verified

A

Using the same technical factors for repeated exposures and then observing with a calibrated ion chamber how intensity varies

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32
Q

Consistency in output radiation intensity at selected kVp settings when generator settings are changed from one mA and time combination to another

A

Exposure linearity

33
Q

Ratio of the different in mR/mAs values between two successive generator settings to the sum of those mR/mAs values

A

Linearity

34
Q

What must the value be of linearity

A

Less than .1

35
Q

When settings are changed from one mA to a neighboring mA station, the most that linearity can vary is:

A

10%

36
Q

Intensifying screens convert xray energy into ______ to produce radiographic density on the film

A

Visible light

37
Q

Appox ___% of the radiographic density of the recorded image results from the visible light photons that are emitted from the intensifying screens

A

95%

38
Q

A single x-ray photon can produce how many light photons with an intensifying screen

A

80 to 95

39
Q

Intensifying screens enhances the film exposure process and __________ exposure time

A

Reduces

40
Q

Rare-earth screen phosphors

A

Gadolinium
Lanthanum
Yttrium

41
Q

What are the speeds for rare-earth screens and matching film combinations

A

200-1200

42
Q

What screen-film speeds are currently standard for general radiography

A

400 speed

43
Q

When the speed of the screen-film system doubles, radiation exposure is reduced by

A

50%

44
Q

As kV increases, effective screen speed __________ for rare-earth screens, which _________ patient dose

A

Increases
Reduces

45
Q

What is used as a front material in screen-film

A

Carbon

46
Q

Carbon fiber absorbs approximately ____ as much radiation as previously used materials

A

Half

47
Q

What is the result of using asymmetric film emulsion and intensifying screen combinations

A

Image with greater uniformity and a decrease in patient dose

48
Q

A device made of parallel radiopaque strips alternately separated with low-attenuation material

A

Grid

49
Q

What are the strips made of in a grid

A

Aluminum, plastic or wood

50
Q

Minimum skin-to-source distance for mobile radiography

A

30cm (12 inches)

51
Q

Distance generally used for mobile radiography is

A

100cm - 120cm (40-48 inches)

52
Q

With _________ SSD there is a more uniform distribution of exposure throughout the patient

A

Increased

53
Q

CR produces what type of image

A

Analog

54
Q

DR produces what type of image

A

Digital

55
Q

How are x-rays turned into electrical signals in indirect conversions using thin-film transistor arrays

A

Scintillator
Photodiode
TFT array
Electrical signals

56
Q

How are x-rays turned into electrical signals in indirect conversions using CCD

A

Scintillator
CCD
Electrical signal

57
Q

How are x-rays turned into electrical signals in direct converions

A

Photoconductor
TFT array
Electrical signal

58
Q

How are repeat rates in DR effected

A

Eliminates the need for retakes due to improper technical selection

Does not effect reports for positoning

59
Q

CR contains what type of phosphor

A

Photostimulable

60
Q

What type of laser beam is used to read the PSP plate

A

Helium-neon laser

61
Q

Sensitivity of the phosphor used in CR is approximately equal to a ______ - speed screen-film combination

A

200

62
Q

CR has a ______ kV flexibility than does conventional screen-film radiography

A

Greater

63
Q

CR is _________ sensitive to scatter so a grid should be used more frequently

A

More

64
Q

What type of imaging has the greatest patient radiation exposure rate in diagnostic radiology

A

Fluoroscopy

65
Q

Benefits of image intensification in Fluoroscopy

A

Increased image brightness
Saving of time for the radiologist
Patient dose reduction

66
Q

What is the kVp range for fluoroscopic procedures on adults

A

75-110

67
Q

What is the SSD for stationary fluoroscopes

A

Not less than 38cm (15 inches)

68
Q

In fluoroscopic procedures, how is kVp changes for children

A

Decrease by as much as 25%

69
Q

How to minimize exposure to children

A

Decrease technical factors
Maintain SSD
Minimize the height of the image intensifier entrance surface above the patient

70
Q

What is the HVL for fluoroscopy units when the kVp is between 80-100

A

3-4.5mm aluminum

71
Q

What is the maxium exposure rate limitation for general purpose fluorscopy

A

100 mGy per minute (10 R/min)

72
Q

What is the maximum exposure rate for high-level control fluorscopic units

A

200 mGy per minute (20 R/min)

73
Q

What is the primary protective barrier required for a fluoroscopic unit

A

2-mm lead

74
Q

Fluoroscopic exposure control switch must be what type

A

Dead-man

75
Q

For C-arms, source-to-end of collimator assembly distance is required to a minimum of

A

30cm (12 inches)

76
Q

For C-arms, patient-image intensifier distance should be as ______ as possible to reduce entrance does

A

Short

77
Q

Dose reduction methods when using fluoro

A

Pulsed imaging
Last-image-hold

78
Q

FDA has recommended that a notation be placed in the patient’s record if a skin dose is in the rank of:

A

1 to 2 Gy

79
Q

Procedures involving extended fluoroscopic time

A

Percutaneous transluminal angioplasty
Radiofrequency cardiac catheter ablation
Vascular embolization
Stent and filter placement
Thrombolytic and fibrinolytic procedures
Percutaneous thanshepatic cholangiopancreatography
Transjugular intrahepatic portosystemic shunt
Percutaneous nephrostomy
Biliary drainage
Urinary or biliary stone removal

Rad Bio (14 decks)

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