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Radiation Protection > Week 11 - Equipment Design > Flashcards

Week 11 - Equipment Design Flashcards

1
Q

What do the designs of radiologic equipment all technologists to do?

A
  • Optimize the quality of the image
  • Reduce radiation exposure to patients
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2
Q

Who are protected when radiographic equipment is used safely?

A

Patients and all personnel

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3
Q

What are the two required features for every diagnostic imaging system?

A
  • protective tube housing
  • correctly functioning control panel
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4
Q

What other components of diagnostic systems have been designed to reduce patient dose?

A

Radiographic exam tables and other devices

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5
Q

What material is required of tube housing?

A

Needs to be lead lined

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6
Q

What does a lead-line tube housing protect patients and personnel from?

A

Off focus or leakage radiation

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7
Q

How do lead lined tube housing reduce off-focus and leakage radiation?

A

Restrict the emission of x-rays to the area of the primary beam

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8
Q

What are the leakage requirements for tube housing?

A

It needs to be constructed so that any leakage measured 1 m from the x-ray source does not exceed 0.88 mGy/hr

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9
Q

Where does a control panel/console need to be located?

A

Behind a suitable protective barrier

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10
Q

What are the features of the suitable protective barrier?

A

Has a radiation-absorbent window that permits observation of the patient during a procedure

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11
Q

What features are required of a control panel?

A

Must indicate the conditions of exposure and provide a positive indication when the tube is energized

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12
Q

How are exposure conditions represented on a console?

A

Through visible mA and kVp readouts

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13
Q

What happens on the console when the exposure begins?

A

A tone is emitted and then stops when it terminates

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14
Q

What does the audible sound indicate?

A

That the x-ray tube is energized and ionizing radiation is being emitted

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15
Q

What is the main feature of a radiographic examination table?

A

It needs to be strong enough to support patient whose weight is in excess of 400 lbs

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16
Q

What feature do exam table usually have?

A

A floating tabletop that makes it easier to maneuver a patient

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17
Q

What needs to remain uniform on an exam table?

A

Thickness

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18
Q

What is an important function of the material of a exam table?

A

Needs to be radiolucent so that it only absorbs a minimum amount of radiation

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19
Q

What material are exam tables usually made of?

A

Carbon fiber

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20
Q

What are two additional features of an exam table?

A

Have a grid and slot cover

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21
Q

What does the SID indicator provide?

A

A way to measure the distance from the anode focal spot is maintained

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22
Q

What are used to measure SID?

A

Lasers or tape measures

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23
Q

At what range are distance and centering indicator accurate?

A

Within 2% and 1% of the SID, respectively

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24
Q

What is a standard rule for the primary beam?

A

That it should be not larger than the size of the IR being used

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25
Q

What is light-localizing variable-aperture rectangular collimator used for?

A

Its used to adjust the size of the x-ray beam automatically or manually

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26
Q

What is the predominant x-ray beam limitation device?

A

Collimator

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27
Q

What is the purpose of a collimator?

A

To reduce scatter radiation

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28
Q

How are light-localizing variable-aperture rectangular collimators constructed?

A

With 2 sets of lead shutters, a light source and a mirror

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29
Q

What do the 1st shutter placed close to the window do?

A

Reduce off-focus radiation

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30
Q

What are the minimum skin sparing distance for fixed machines?

A

15 cm

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31
Q

What is the minimum skin sparing distance for mobile machines?

A

30 cm

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32
Q

What is luminance?

A

Brightness of the light source

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33
Q

What are the benefits of restricting x-ray field size to only include area of interest?

A
  • Significant reduction in patient dose, because less scatter is produced
  • Improves overall quality of the image
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34
Q

What is positive beam limitation?

A

When the beam of light is automatically adjusted to the size of the IR being used

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35
Q

What must the radiographer ensure when PBL is in use?

A

That the collimation is accurate and adjusted to the size of the part and no bigger than the IR

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36
Q

What are radiographic cones?

A

Circular metal tubes that attach to the x-ray tube housing and limit the beam to a predetermined size and shape

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37
Q

What are the two types of cones?

A

Flared metal tubes and straight cylinders

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38
Q

What types of cones are used in dental radiography?

A

Beam-defining cones

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39
Q

What is another type of beam limiting device?

A

Aperture diaphragm

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40
Q

What is an aperture diaphragm?

A

A flat piece of lead with a hole in it of a designated size and shape

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41
Q

Where is an aperture diaphragm placed?

A

Directly below the window of the x-ray tube to confine the primary beam to the given size of the hole

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42
Q

What do sizes of aperture diaphragms relate to?

A

Each size IR and SID

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43
Q

What is the purpose of beam filtration?

A

To remove low energy photons

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44
Q

How does beam filtration effect patient dose?

A

It lowers patient dose, by hardening the beam and making it more penetrating

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45
Q

How is the energy of the beam affected by filtration?

A

The effective energy of the beam is increased

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46
Q

What are the 3 types of filtration?

A
  • inherent
  • added
  • total filtration
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47
Q

How do beam filters work?

A

They absorb the low energy photons and permit high energy photons to pass through

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48
Q

What is the minimum total filtration required when more than 70 kVp is used?

A

2.5 mm Al equivalent

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49
Q

What is the minimum total filtration required when 50-70 kVp is used?

A

1.5 mm Al equivalent

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50
Q

What is the minimum total filtration required when less than 50 kVp is used?

A

0.5 Al equivalent

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51
Q

How is filtration most widely expressed?

A

In aluminum or its equivalent

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52
Q

What is the required Al eq for inherent filtration?

A

0.5 mm Al eq - glass and oil
1.0 mm Al eq - collimator mirrors

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53
Q

What is the required Al eq for added filtration?

A

1.0 Al (thin sheets of aluminum

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54
Q

What is the Al equivalent for total filtration?

A

2.5 Al eq

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55
Q

What is the minimum Al eq filtration for mobile diagnostic and fluoroscopic equipment?

A

2.5 mm Al eq

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56
Q

What is half value layer?

A

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

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57
Q

Why must the HVL be measured?

A

To verify that the x-ray beam is adequately filtered

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58
Q

Who should obtain the HVL measurement?

A

A radiologic physicist

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59
Q

When should a radiologic physicist obtain the HVL?

A

At least once a year, after an x-ray tube is replaced or when the housing or collimator have been repaired

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60
Q

How is HVL expressed?

A

In millimeters of aluminum

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61
Q

What does HVL measure specifically?

A

Beam quality or effective energy of the x-ray beam

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62
Q

What are compensating filters made up of?

A

Aluminum, lead acrylic or other suitable material

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63
Q

What are compensating filters used for?

A

To accomplish dose reduction and uniform imaging of body parts that vary considerably in thickness/tissue composition

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64
Q

How do compensating filters work?

A

They partially attenuate x-rays directed towards the thinner areas and allow more x-rays to strike the thicker areas

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65
Q

What are the two types of compensating filters?

A
  • wedge filter
  • trough, or bilateral wedge filter
66
Q

What are the two required radiation exposure characteristics?

A
  • Exposure reproducibility
  • Exposure linearity
67
Q

What does exposure reproducibility provide?

A

Consistency in output radiation intensity for identical generator settings between individuals

68
Q

What variance is accepted for exposure reproducibility?

A

A variance of 5% or less

69
Q

How can reproducibility be verified?

A

By using the same technical exposure factors to make a series of repeated exposures and then observing with a calibrated ion chamber and seeing how the intensity varies

70
Q

What does exposure linearity provide?

A

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

71
Q

What is linearity?

A

The ratio of the differences in mSv/mAs or mR/mAs between two successive generator stations to the sum of these mSv/mAs or mR/mAs values

72
Q

What does the linearity ratio need to be?

A

Less that 0.1

73
Q

What is the variation percent when settings are changed from one mA to a neighboring mA station?

A

10%

74
Q

What is AEC?

A

An x-ray terminating device that ends the radiation when a predetermined amount of radiation is received by an arrangement of sensors

75
Q

What does AEC produce?

A

An acceptable image while limiting radiation exposure to a patient

76
Q

What is a safety feature that is part of AEC?

A

A backup timer

77
Q

What is phototiming?

A

Old terminology referring to photomultiplier tubes

78
Q

What do today’s AEC systems utilize?

A

Ionization chambers

79
Q

What is a radiographic grid?

A

A device made of parallel radiopaque strips alternately separated with low-attenuation strips of aluminum, plastic or wood

80
Q

Where is a radiographic grid placed?

A

Between the patient and the IR

81
Q

What do radiographic grids do?

A

Remove scattered x-ray photons that emerge from the patient before it can reach the IR and decrease image quality

82
Q

What impact do radiographic grids have on image quality?

A

They increase radiographic contrast and visibility of detail

83
Q

What size parts require the use of radiographic grids?

A

Parts that are 10 cm or more

84
Q

What is grid ratio?

A

Refers to the height of the lead strips divided by the distance between each strip

85
Q

What is the minimum SSD that should be used for mobile units?

A

Minimum SSD is at least 30 cm (12 inches)

86
Q

What is the distance generally used for mobile radiography?

A

100 cm (40 inches) or 120 cm (48 inches)

87
Q

What effect does SSD have on patient entrance exposure?

A

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

88
Q

When are mobile units used?

A

For patients who can’t be transported to a fixed unit

89
Q

What are the 5 digital processed radiography imaging modes?

A
  • Computed tomography (CT)
  • Computed radiography (CR)
  • Digital Radiography (DR)
  • Digital Fluoroscopy (DF)
  • Digital Mammography (DM)
90
Q

What are negative features of conventional radiography: analog images?

A
  • Latent image creation and latent imaging processing
  • Time consuming processing time
  • Images often lost
91
Q

What is a positive feature of conventional radiography: analog images?

A

Produced optimal-quality images

92
Q

What has conventional radiography: analog images been replaced by?

A

Digital imaging

93
Q

What is digital imaging?

A

Process of producing an electronic image

94
Q

What are some limitations of digital imaging?

A

Inherent limitations with respect to spatial and contrast resolution due to dimensions of pixels

95
Q

What is digital imaging subject to?

A

Artifacts because digital imaging are produced collectively by a matrix of elements and are subject to noise

96
Q

How are images formed in digital imaging?

A

Latent image is formed by x-ray photons on a radiation detector

97
Q

What is brightness in digital imaging?

A

The amount of luminance (light emission) on a display monitor

98
Q

What are digital images composed of?

A

Numerical data that is stored in rows and columns called the image matrix

99
Q

How does digital radiography work?

A

Image receptors convert energy into electric signals

100
Q

What is a scintillator?

A

Converts x-ray energy into visible light and is made of amorphous silicone

101
Q

What is visible light transformed into in digital radiography?

A

Transformed into electrical signals by charge-coupled devices (CCDs)

102
Q

What is a photoconductor?

A

Converts x-ray energy directly into electrical signals which are then read by transistors.

103
Q

What are photoconductors made of?

A

Amorphous selenium

104
Q

Where can digital images be accessed?

A

At multiple workstations

105
Q

What are the two types of conversion in digital imaging?

A

Indirect and direct conversion

106
Q

What are the two types of indirect conversion?

A

Scintillator > Photodiode > Thin-film transistor array > Electrical signals

Scintillator > Charge-coupled device array > Electrical Signals

107
Q

What is the process of direct conversion?

A

Photoconductor > Thin-film transistor array > Electrical signals

108
Q

How are images generated in computed radiography?

A

Using photostimulable luminescence (PSL)

109
Q

How is CR different than DR?

A

CR uses conventional radiographic equipment, traditional positioning and standard technical exposure factors

110
Q

What doe CR cassettes contain?

A

Photostimulable phosphors

111
Q

How are images read in CR?

A

A read unit scans the photostimulable phosphor plate with a laser beam and then displays it on a monitor

112
Q

Which type of radiography has a greater KV flexibility?

A

CR

113
Q

What type of radiography requires a more frequent use of grids?

A

CR since the imaging patients are more sensitive to scatter

114
Q

What are the advantages of DR?

A
  • lower doses
  • greater ease of use and faster patient throughput
  • immediate imaging results
  • additional image manipulation
  • less overall maintenance
115
Q

What are the disadvantages of DR?

A
  • more costly
  • not cross compatible
  • single detector size
  • PSP imaging plates are subject to mechanical damage and chemical oxidation
  • high replacement costs
116
Q

What are the 3 types of artifacts DR are subject to?

A

Image aliasing, Moire patterns and contouring defects

117
Q

How does DR eliminate the need for retakes?

A

Improper technical selections that produce contrast or brightness issues can be manipulated after image acquisition

118
Q

Why is there an increased repeat rate in DR?

A

Because of the ease of repeating images

119
Q

How are mispositioning repeats monitored?

A

An independent quality control technologist at a separate monitor

120
Q

Where does the body area need to be positioned on a CR IR?

A

In or near the center of the IR

121
Q

What are fluoroscopic procedures used for?

A

To capture dynamic or active motion images of selected anatomic structures

122
Q

Which type of radiography produces the greatest patient radiation exposure rate?

A

Fluoroscopic radiography

123
Q

How are fluoroscopic procedures performed?

A

With a fluoroscopic tube inside the xray table facing up toward the surface of the table

124
Q

How does an image intensifier fluoroscopic unit work?

A

It converts the pattern of x-rays transmitted through the patient into a corresponding and amplified visible light patternW

125
Q

What are the benefits of image intensification fluoroscopy?

A
  • increased image brightness
  • saving of time for the radiologist
  • patient dose reduction
126
Q

How is an image intensifier used?

A

It’s placed over the patient on this table during the examination and is used in conjunction with the tube

127
Q

How much is the brightness of the fluoroscopic image increased compared to non-image intensified fluoroscopy?

A

10,000 times

128
Q

How much mA is reduced when fluoroscopic vs intensified fluoroscopic?

A

Reduced from 3-5 mA to 1-1.5 mA

129
Q

What does an image intensifier tube produce?

A

A magnified image

130
Q

What are the benefits of pulsed and interrupted fluoroscopy?

A
  • Significantly decreases patient dose
  • Extends tube life
  • Has a last-image hold feature
131
Q

What is the standard kVp range for adult patients using non-digital fluoroscopic imaging systems?

A

75-100 kVp

132
Q

What is the SSD for stationary fluoroscopes?

A

No less that 38 cm

133
Q

What is the SSD for mobile fluoroscope?

A

No less than 30 cm

134
Q

How should kVp be adjusted for children in non-digital fluoroscopic imaging systems?

A

KVp should be decreased as much as 25%

135
Q

In what ways are exposures limited for children using fluoroscoping imaging systems?

A
  • Decreasing technical factors, maintaining SSD and minimizing height of image intensifier entrance surface above patient
136
Q

What is the HVL for non-digital fluoroscopic image systems?

A

HVL of 3-4.5 mm Al acceptable when kVp ranges from 80-100

137
Q

Who sets up current standard limits for entrance skin exposure rates?

A

Federal government

138
Q

What is the maximum entrance skin exposure rate for non-digital fluoroscopic imaging systems?

A

Maximum of 88 mGya/min (10R/min)

139
Q

What is the maximum entrance skin exposure for fluoroscopic units equipped with high level control?

A

Maximum of 176 mGya/min (20 R/min)

140
Q

What is the primary protective barrier of non-digital fluoroscopic imaging systems?

A

2mm lead equivalent

141
Q

What type of exposure control switch does fluoroscopic machine need to have?

A

A dead man type

142
Q

What is the shape of a portable fluoroscopic unit?

A

C shaped with c-ray tube attached at one end and an image intensifier at the other

143
Q

What are portable fluoroscopic units used for?

A

In the operating room for orthopedic procedures, cardiac imaging and interventional procedures

144
Q

What risk do patients and personnel have with mobile fluoroscopic units?

A

Risk of large radiation doses from scatter

145
Q

What must C-arm equipment operate have?

A

Appropriate education and training to ensure they follow safety guidelines and meet safety protocols

146
Q

What is the source to end collimator distance required for mobile fluoroscopic units?

A

30 cm

147
Q

What should the distance be for image-intensifiers in mobile fluoroscopy units?

A

As short as possible to reduce entrance dose

148
Q

How should the C arm be positioned to reduce patient dose?

A

Under the patient since it limits scatter

149
Q

What happens when the C arm is positive over the patient?

A

Scatter becomes more intense and exposure increases correspondingly

150
Q

What system do digital fluoroscopy systems use for dose reduction?

A

Pulse progressive systems

151
Q

What is last image hold?

A

The last image formed remains on the monitor so that no further radiation exposure is needed to regenerate it

152
Q

What are interventional procedures?

A

Locate high contrast using small objects such as catheters, stems or electrical leads

153
Q

What is digital subtraction angiography?

A

Visualization of blood vessels

154
Q

What is roadmapping?

A

A static image of the vasculature may be obtained through subtraction, pre and post contrast injection

155
Q

Where is a catheter inserted?

A

Into vessels or tissues

156
Q

What is the purpose of a catheter?

A
  • Drainage
  • Biopsy
  • Alteration of vascular occlusions or malformation
157
Q

What is High-level-control fluoroscopy?

A

An operating mode for state of the art fluoroscopic equipment in which exposure rates are substantially higher than those normally allowed in routine procedures

158
Q

What has the FDA recommended for procedures involving fluoroscopic radiology?

A

That a notation be placed in their record if skin dose is in the range of 1-2 Gy received

159
Q

What are the procedures that involve extended fluoroscopic time?

A
  • percutaneous transluminal angioplasty
  • radio frequency cardiac catheter ablation
  • vascular embolozation
  • stent and filter placement
  • thrombocytes and fibrinolytic procedures
  • Percutaneous trashepatic cholangiograpy
  • Endoscopic retrograde cholangiopancreatography
  • transjugular intrahepatic portosystemic shunt
  • percuraneous neprostomy
  • biliary drainage
  • urinary or biliary stone removal
160
Q

What do non-radiologist physicians need when using fluoroscopic equipment?

A

Ongoing education and training

Radiation Protection (17 decks)

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