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SEM VI - RAD REVIEW > **Saia Unit 5 > Flashcards

**Saia Unit 5 Flashcards

1
Q

Battery/DC power

A

Provides electric potential

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2
Q

AC power

A

Provides electric potential

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3
Q

Capacitor

A

Temporarily stores an electric charge

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4
Q

Ammeter

A

Measures current

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5
Q

Voltmeter

A

Measures electric potential

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6
Q

Switch

A

Controls ON/OFF

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7
Q

Transformer

A

Increase or decrease voltage

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8
Q

Rheostat

A

Variable resistor

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9
Q

Diode/rectifier

A

Electrons flow in only one direction

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10
Q

Ground

A

A neutral object ready to receive electrons

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11
Q

Rectifier

A

Converts AC to DC

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12
Q

Imaging system contains 3 systems

A

Operators console
High voltage-generator/section
X-ray tube

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13
Q

Components of the Operators console function on relatively

A

Low voltage and amperage for Personnel safety

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14
Q

High voltage generator/section function on relatively

A

High voltage and amperage making them unsafe to be located near humans

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15
Q

X-ray tube functions on

A

High voltage and amperage which is Insulated for safety

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16
Q

Resistor

A

Inhibits electron flow

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17
Q

The operators console allows the radiographer to control

A

The X-ray tube current (mAs), voltage (KVP), and exposure time

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18
Q

MAs= quantity

A

Refers to the number of X-rays in the beam

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19
Q

KVP= quality

A

Refers to the penetrability of the beam

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20
Q

Exposure time =

A

How long voltage is applied

Current will only flow when voltage is applied

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21
Q

Operators console also includes

A

AEC selection
Bucky selection
On/off switch

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22
Q

Line compensation

A

Adjusts the incoming voltage to the precise value that the system is designed to operate on - most operate on 220V however the power companies voltage can vary by as much as 5% thus the need for a compensator to keep voltage at a constant 220V

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23
Q

Auto transformer

A

Variable ratio transformer which supplies a precise voltage to the filament circuit and to the high voltage circuit.

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24
Q

Once the voltage has passed through the auto transformer

A

It is no longer susceptible to fluctuations or surges in the line voltage

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25
Q

KVP selector

A

The secondary side of the autotransformer ,the percentage of available voltage is selected by the technologist, usually in 2 control selectors, a major (steps of 10KV) and minor KV (steps of 1-2KV)

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26
Q

Selected voltage from secondary of auto transformer is delivered to

A

The high voltage(step up) transformer

High voltage transformer has a fixed ratio of 1000:1, every volt becomes a kilovolt

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27
Q

The filament circuit

A

High amperage is required for thermionic emission in the filament, it is necessary to step-down the voltage - as voltage decreases amperage increases.

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28
Q

MA selector (part of the filament circuit)

A

Resistors or a rheostat along the filament circuit which controls the amperage delivered to the filament

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29
Q

Most filaments operate at between

A

3-6 amps,

As amperage to filament increases thermionic emission increases

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30
Q

MA =

A

The number of electrons thermionically emitted per second

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31
Q

Exposure timers (5 different types)

A

Mechanical (wind up timer)
Synchronous (measures voltage pulses -capable of 1/120 of a second)
MAS (delivers a selected mAs w/o setting the “S”)
Electric (modern - capable of 1/1000 of a second)
AEC (automatic exposure control)

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32
Q

High voltage generator

A

Increases voltage to kilovolts, increases amperage for thermionic emission, converts AC to DC

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33
Q

A high voltage generator consists of 3 main parts

A

High voltage transformer - step up
Filament transformer - step down
Rectifier - converts AC to DC

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34
Q

The high voltage transformer

A

Reconfigures wattage from primary to secondary, wattage remains constant between primary and secondary sides of the transformer

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35
Q

The more turns on a transformer

A

The stronger the magnet, the stronger the magnet the higher the voltage

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36
Q

Watt

A

The unit of electrical power

- volts x amps = watts

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37
Q

The primary side of the transformer

A

Is the side of the transformer that is initially supplied with current

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38
Q

The secondary side of the transformer

A

The side of the transformer in which current is induced to flow

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39
Q

Transformers can change voltage and/or amperage between primary and secondary sides of the transformer but…

A

Wattage remains constant between primary and secondary sides of the transformer

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40
Q

Step up transformer

A

Voltage is increased from primary to secondary sides

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41
Q

Step down transformer

A

Voltage is decreased from primary to secondary

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42
Q

Transformer “stepping”

A

How voltage is affected from primary to secondary sides of a transformer

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43
Q

High voltage transformer

A

Step up transformer
2 iron cores, operates by mutual induction
Fixed ratio - approximately 1000:1
Primary side initially supplied w/volts and amps
Secondary side induced kilovolts and milliamps

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44
Q

Filament transformer

A

Step down transformer
2 iron cores, operates by mutual induction
Fixed ratio - approximately 1:3
Primary side initially supplied with volts and amps
Secondary side induced volts and amps

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45
Q

If grid ratio is greater than 1

A

Step up transformer

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46
Q

If grid ratio is less than 1

A

Step down transformer

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47
Q

Voltage rectification

A

Converting AC to DC

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48
Q

Why convert from AC to DC

A

Transformers only work on AC

X-ray tube is most efficient on DC

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49
Q

Solid state diode/rectifier

A

Uses material which is semi conductive

Current is conducted through a diode only in one direction, opposed in the other

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50
Q

Cathode is uniquely designed to emit electrons

A

But not receive

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51
Q

Anode is uniquely designed to receive electrons but

A

But not to emit

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52
Q

Filament current

A

Amperage delivered to filament for thermionic emission

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53
Q

Tube current

A

Electrons traveling from cathode to anode (mAs)

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54
Q

The higher the current voltage, the greater the

A

Amplitude of the wave

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55
Q

During the positive cycle of the unrectified waveform

A

Anode is energized with positive charge
Cathode is energized with negative charge
Electrons flow from cathode to anode

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56
Q

During the negative cycle of the unrectified waveform

A

Anode is energized with negative charge
Cathode is energized with positive charge
Electrons cannot flow from cathode to anode

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57
Q

Half wave rectification is accomplished with

A

2 diodes which only allow the positive cycle of AC waveform to be conducted through the circuit.
1/120 second of dead time between pulses

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58
Q

Full wave rectification is accomplished with

A

4 diodes for each phase of power, two diodes block the negative pulse, two redirect it so that it is traveling the same direction as the positive pulse

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59
Q

Cycles per second is measures in

A

Hertz

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60
Q

Each cycle has a positive and negative and positive pulse

A

(2pulses), 120 pulses per second

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61
Q

Have wave rectification

A

60 pulses per second, only the positive pulse of AC waveform used to make xray, 100% voltage ripple

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62
Q

Full wave rectification

A

120 pulses per second, both the positive and negative pulses used to make xray, 100% voltage ripple

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63
Q

3 phase power

A

3 independent voltage waveforms working together in phase for mor efficient way to use voltage. Each voltage waveform has 120 pulses per second

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64
Q

3 phase 6 pulse -

A

360 pulses per second. 13% ripple

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65
Q

3 phase 12 pulse -

A

720 pulses per second, 4% ripple

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66
Q

High frequency generator

A

Modern system of powering an xray system, more efficient usage of available voltage.
Creates “square” waveforms of extremely high frequency creating high efficient power.
Only 1% ripple - less mAs required, lower patient exposure.

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67
Q

Voltage ripple

A

How far the voltage waveform falls from its peak

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68
Q

Main breaker

A

This is where the alternating current comes from the power circuit

69
Q

Exposure switch

A

When you push the button to start an exposure this switch closes to the start the exposure

70
Q

Auto transformer

A

This is where you adjust the KVP for exposure

71
Q

Timer circuit

A

This part of the circuit stops the exposure

72
Q

High voltage step up transformer

A

Bumps the voltage up so that the X-ray tube has very high voltage to make the electrons have enough energy to form X-rays

73
Q

Four diode rectification circuit

A

This makes the current only go in one direction through the X-ray tube

74
Q

Filament circuit variable resistor

A

Adjusts the current going into the filament

75
Q

Filament step down transformer

A

Steps the voltage down and therefore the current up.

76
Q

X-ray tube

A

Where X-rays are created

77
Q

Motor stator

A

This rotates the anode

78
Q

X-rays are created on demand, the technologist controls

A

When X-rays are created (exposure switch)
Strength of X-rays created (KVP adjustment)
How many X-rays created (mAs adjustment)
How long X-rays created (exposure timer)
All are controlled at the operators console

79
Q

X-rays are created by a conversion of energy to another

A

Electrical energy into electromagnetic energy through a series of energy conversions.
Electrical, thermal, potential, kinetic, electromagnetic

80
Q

Voltage

A

In xray this is the Force/strength of electron propulsion

81
Q

Amperage

A

In xray this is the number of electrons in motion

82
Q

Voltage

A

Also known as potential difference or potential or electromotive force (emf)
The force that propels electrons

83
Q

Amperage

A

Also known as current or impedance.

The number of electrons in motion

84
Q

1 amp =

A

6.3 x 10^23 electrons per second

85
Q

Density

A

The overall blackening of a film/image

86
Q

Density is referred to as ? With digital imaging

A

Brightness

87
Q

Controlling factors of density are

A

MA
Time
MAs

88
Q

MAs

A

The number of X-rays in the polyenergetic beam

89
Q

Contrast

A

The difference in adjacent shades across a radiographic image

90
Q

Primary function of contrast is to

A

Make recorded detail visible

91
Q

High contrast

A

Black and white, few grays

92
Q

Low contrast

A

Image with many grays

93
Q

Contrast is primarily controlled by

A

KVP.

94
Q

As KVP increases there is a greater variety of

A

Xray energies in the primary beam

95
Q

Energy deposited into the IR =

A

Density

96
Q

More energy values =

A

More shades of density

Shades of gray

97
Q

KVP =

A

Peak xray strength in the polyenergetic primary beam

- X-rays are created at all energy values up to the peak strength

98
Q

Fluoroscopy was developed

A

By Thomas Edison in 1896 as a real time dynamic image produced on glass plate covered with a layer of phosphor ,material.

99
Q

Flux gain

A

Few xray photons converted to many visible light photons

100
Q

Image intensifier for fluoroscopy

A 
Glass envelope (maintains vacuum)
Input phosphor (cesium iodide)
Photocathode (antimony)
Focusing lenses (electrostatic - mutual repulsion)
Anode (positive charge attracts electrons)
Output phosphor (zinc cadmium sulfide)
101
Q

Image intensifier for fluoro is like am X-ray tube which results in

A

1 xray photon is amplified to many light photons

The image is intensified

102
Q

Input phosphor for fluoroscopy

A

Cesium iodide - efficient at converting xray energy to visible light
Needle like crystals
Xray “Coming in” to the fluoro tube

103
Q

Output phosphor for fluoroscopy

A

Zinc cadmium sulfide - efficient at converting electron energy to visible light
Last stage of fluoro tube (last letter Z in alphabet - inc)

104
Q

Minification gain

A

Result of many electrons leaving the relatively large input phosphor/photocathode impacting the relatively small output phosphor

105
Q

As minification gain increases

A

The visible light image becomes brighter

106
Q

Minification gain formula

A

Minification gain = input phosphor diameter^2/output phosphor diamter^2

107
Q

Standard input phosphor/photocathode sizes are

A

6”, 9”, or 12”

108
Q

Total brightness gain

A

Minification gain x flux gain

How much has the image been intensified by the image intensifier tube

109
Q

ABC - automatic brightness control

A

Maintains a preset brightness level by automatically adjusting the exposure factors to compensate for varying subject

110
Q

Fluoro imaging techniques

A

Very low mA (0.5-5mA)

Higher KVP utilized

111
Q

SSD for fluoro

A

Fixed - 15”

Mobile - 12”

112
Q

Quantum mottle can be a problem with fluoroscopy due to

A

Not enough X-rays (mAs)

Not enough photons hitting the input phosphor

113
Q

Magnification tubes

A

Modern tubes can magnify images 1.5-4 times

As voltage increases the electrons are pushed closer to the input phosphor which causes the image to be magnified at the output phosphor

114
Q

The TV camera with fluoro

A

A camera is placed adjacent to the output phosphor in order to capture and transmit the output intensified image resulting in the radiologist no longer has to view image from phosphor screen and or be in the path of the beam

115
Q

Two basic types of fluoro cameras

A

Vidicon - general fluoro

Plumbicon - interventional fluoro

116
Q

Fluoro splitter

A

Able to split the signal from output phosphor to multiple components

  • monitor
  • video
  • digital video
  • hard film
117
Q

The smaller the mode, the more magnified the image

A

Mag mode increases scatter radiation

118
Q

Changes in voltage to the electrostatic focusing lenses causes

A

The electrons to narrow or widen their stream

119
Q

Common field size for angio

A

35/25/15 cm

120
Q

Common field sizes for general

A

25/17cm

121
Q

A conventional fluoro system often has multiple imaging devices

A 
TV camera
Spot films
Cine camera
Cassette
All use the image as displayed on the output phosphor
122
Q

Fluoro exposure should not exceed

A

10R/min for general fluoro

123
Q

5 minute timer

A

Fluoro unit must alarm every 5 minutes to alert radiologist/surgeon of fluoro time

124
Q

Magnification fluoro causes

A

Increased dose

125
Q

Fluoro is the rad techs #1

A

Source of exposure
-scatter from patient
Use inverse square law!

126
Q

Lead aprons must be worn in fluoroscopy that have at least

A

0.5mm Pb equivalent

127
Q

Fluoro Bucky slot covers and lead drapes =

A

At least 0.25mm Pb

128
Q

High contrast

A

Few shades of gray, increased contrast, lower KVP, “short scale” contrast

129
Q

Low contrast

A

Many shades of gray, decreased contrast, high KVP, “long scale” contrast

130
Q

Grid conversion factors

A

No grid = 1

5: 1 = 2
6: 1 = 3
8: 1 = 4
12: 1 = 5
16: 1 = 6

131
Q

Filtration a minimum of

A

2.5mm Al/eq

132
Q

The purpose of filtration

A

To remove weaker xray from the primary beam

133
Q

Half value layer

A

The amount of filtration required to lower xray intensity to 1/2 of its original value

134
Q

Collimator illuminance

A

Brightness of collimator bulb and field,

At least 15 foot candles (160 lux) at 40”

135
Q

Xray to light field

A

Collimator to xray beam alignment
+/- 2%
Semiannual

136
Q

Nine penny test

A

Test done for xray to light field (diameter of penny is .8 inches)

137
Q

Positive beam limitation

A

Auto collimation of light field to IR size. Can be smaller, can NEVER be larger!
+/- 2%
Semiannual

138
Q

Focal spot size is tested by

A

Pinhole camera, star pattern, slit camera
+/- 50%
Annual

139
Q

KVP accuracy is measured with

A

Voltmeter and radiation meter
+/- 10%
Annual

140
Q

Exposure timer accuracy

A

+/- 5% greater than 10ms

+/- 20% less than 10ms

141
Q

Exposure linearity

A

Using the same mAs but differing combinations of mA and S

i.e. 100mA @ 1/2S same as 200mA @ 1/4S

142
Q

AEC backup timer is set to self terminate if…

A

600 mAs reached

143
Q

If the AEC backup timer is manually set, it should be set to

A

150% of expected mAs

144
Q

AEC optical density versus change

A

+/- .30D

145
Q

Film illuminator standard is

A

15 Watt daylight bulb

146
Q

Fluoro rate ESE shall not exceed

A

10R/min

147
Q

IR exposure rate ESE shall not exceed

A

20R/min

148
Q

Repeat analysis goal

A

To minimize patient exposure

149
Q

Wire mesh test is used to evaluate

A

Contact between intensifying screen and film

Annually

150
Q

Speed uniformity is tested to assure

A

That all like speed intensifying screens respond to the same xray stimulation by releasing the same amount of visible light
+/- 10%
Annual

151
Q

Darkroom fog can be no greater than

A

.08 (xray) or .05 (mammo)

Semiannual

152
Q

Sensitometry

A

Measuring the response of film to exposure and processing

Daily

153
Q

Developer is sensitive to changes in

A

Temperature, oxidation, concentration, contamination

154
Q

Sensitometer

A

Device that emits varying intensities of light in a star pattern on a film

155
Q

Pemetrometer

A

Aluminum step wedge that is exposed to radiographic film and developed to measure xray penetration

156
Q

21 step sensitometer is

A 
Most common (41% difference between steps)
Also a 11 step (100% difference between steps)
157
Q

Densitometer

A

Reads/measures image density, measures how much light is emitted to film and how much is transmitted

158
Q

Optical density

A

Incident light striking the film to the intensity of light transmitters through film

159
Q

The higher the optical density, the less light transmitted

A

Therefore the greater density

160
Q

Density difference of contrast indicator

A

Found by subtracting the Dmin from Dmax

+/-.15OD

161
Q

Hyporetention (fixer=hypo)

A

Must be less than .05Gr/m^2
Emulsion turns brown in storage due to inadequate washing of film in processor
Quarterly

162
Q

+/-2%

A

Collimator dial accuracy (2% of SID)
SID accuracy (2% of SID)
Xray to light field
Positive beam limitation

163
Q

+/-5%

A

REPRO
Exposure reproducibility
AEC reproducibility

164
Q

+/-10%

A 
KVP accuracy
mR/mAs (from installation)
Exposure linearity
AEC density steps
Film illuminators (speed uniformity)
165
Q

+/- 50%

A

Focal spot size

166
Q

Daily

A

Sensitometry

167
Q

Quarterly

A

Hyporetention

168
Q

Semiannual

A

Collimator dial accuracy
Xray to light field
Positive beam limitation
Darkroom fog

169
Q

Annual

A 
Filtration
Half value layer
Collimator illuminance
SID accuracy
Focal spot size
KVP accuracy
mR/mAs
Exposure timer accuracy
Exposure linearity
Exposure reproducibility
Protective apparel
Film illuminators
Film screen contact
Speed uniformity

SEM VI - RAD REVIEW (8 decks)

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