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2016FA PHYSICS (K. Greene) > EXAM #2 (Ch. 8-10, 17, 21) > Flashcards

EXAM #2 (Ch. 8-10, 17, 21) Flashcards

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1
Q

High frequency generators are __ % ripple.

A

High frequency generators are ~ 1% ripple.

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2
Q

True / False

High frequency generators are the most efficient generators

A

True

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3
Q

True / False

High frequency generators are large

A

False

High freq. generators are small in size

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4
Q

[*] Variation in peak voltage waveform.

Single phase = __%

Three phase 6 pulse = __%

Three phase 12 pulse = __%

High frequency = __%

A

Single phase = 100%

Three phase 6 pulse = 14%

Three phase 12 pulse = 3%

High frequency = ~1%

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5
Q

What do exposure timers do

Typical time interval?

A

Allow us to know exactly how long the electrons boiled off will take to cross the circuit

10-15 miliseconds

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6
Q

What’s a mechanical timer in terms of:

  • What units are they used in?
  • What kind of design?
  • Typical time interval?
A

Used in portable or dental units

Clockwork design

Only for times >250ms

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7
Q

What are synchronous timers in terms of:

  • Type of motor
  • Typical time interval?
A

Electric motor spinning at precisely 60rev/s

Time intervals of multiples of 1/60 s

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8
Q

What are electronic timers in terms of:

  • Prevalence
  • Accuracy
  • Price
  • Circuitry
  • Times
  • Usage
A
  • Most common timer
  • Most accurate
  • Expensive
  • Complex circuitry
  • Time = ~1ms
  • Can be used for rapid exposures (fluoroscopy)
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9
Q

What are mAs timers?

• How can you tweak mAs?

A

Tell it what mAs you need and it selects maximum mA and minimal time

Example: I want 300 mAs, how can I get to 300 mA and s?

300 mA (300 electrons) for 1 second
600 mA for .5 second
1200 mA for .25 second

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10
Q

[*] What are AEC in terms of:

What does it stand for?

How does it work?

When will the X-ray turn off for safety?

A

Automatic Exposure Control

As the exposure is being made, the beam is turned off once enough radiation has reached through to the cells in the bucky

Turns off for safety after 6 seconds / 600 mAs

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11
Q

POWER = _____ • _____

WATTS = _____ • _____

A

POWER = CURRENT • POTENTIAL

WATTS = AMPERES • VOLTS

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12
Q

What’s the maximum available power?

A

When you use the maximum tube current, mAs, at 100 kVp for 100ms

Example:

60kW

POWER = 600mA • 100kVp
POWER = 60kW
(100kVp, 100ms, and 600 mA = 60,000W)

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13
Q

Power ratings are expressed in what unit?

A

Kilowatts, not watts

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14
Q

What is the three phase and high-frequency generator equation?

• What is the single phase generator equation?

A

kW=(mAs x kVp) / 1000

• kW= 0.7 x {(mAs x kVp) / 1000}
0.7 is used to account for waveform ripple

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15
Q

What are the 3 external structures of the x-ray tube?

A

Support structure

Protective housing

Glass/metal envelope

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16
Q

What are the 2 internal structures of the x-ray tube?

A

Cathode

Anode

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17
Q

What purpose do external structures serve?

• What are the two types of support systems?

A

Supports tube housing and allows tube movement

Floor-to-ceiling support
+
Floor mounted support

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18
Q

X-ray tube housing must limit radiation leakage to ___ Mr/hour @ ___ meter(s)

• What is Mr?

A

X-ray tube housing must limit radiation leakage to 100Mr/hour @ 1 meter

Mr = milliroentgen

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19
Q

What is the purpose of the X-ray tube housing?

  • What provides an outlet for the beam to exit?
  • What is the purpose of the oil?
  • How does it decrease shock risk?
A

Protects tube from damage and reduces radiation exposure from non-useful beam

  • The window
  • Allows heat from tube to go to the oil and cool the tube (sometimes a fan)
  • High voltage receptacles decrease shock risk
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20
Q

What is the cathode?

  • Is the cathode the negative or positive side of the tube?
  • What material is it made of and why?
  • Can vaporization be detected prior to tube failure?
A

A low current flows to the cathode to keep it at a set temperature to prepare it for exposure (too much heat when it’s cold will break it)

  • Negative side of the tube
  • Often composed of tungsten because it can sustain high temperatures and has good longevity
  • Yes, vaporization can be detected prior to tube failure
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21
Q

[*] What is thermionic emission?

A

The coil of wire is hot enough now that it’s giving off electrons (boiling them off)

(this can take place before exposure)

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22
Q

What is the focusing cup in the cathode?

• Is it positive or negative, and why?

A
  • Holds filament in the metal cup

* The cup is negatively charged and thus repulses the negative electrons in a certain direction (like charges repel)

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23
Q

What are dual focus tubes?

  • In what situations are both components used?
  • Their FSS on the anode?
A

Tubes with 2 filaments (one small + one large)

  • one small filament (small focal spot) - low mA used, more detail
  • one large filament (large focal spot) - high mA used, less detail

• size on anode:
small FSS = 0.1 - 0.6mm
large FSS = 1.0 - 1.2mm

FSS = focal spot size

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24
Q

Is the anode positive or negative?

  • What machines have stationary anodes?
  • Why do anodes rotate?
A

The positive side of the tube where the x-ray is produced

  • Stationary is used in portable and dental units, which require low current and power
  • Rotating allows the disk to rotate which allows greater heat capacity, dissipation, current, and power
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25
Q

What are the 3 PURPOSES of the anode?

A

electrical conductor = returns electrons to high voltage generator

mechanical support = hold target / FS

thermal conductor = must be able to conduct large amounts of heat quickly to prevent melting of RS and anode

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26
Q

Why do we have two filaments

A

small is for more detail and small parts

big is for big parts that are more dense

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27
Q

What might the anode be made of

• The track?

A

molybdenum
rodium
graphite

track = tungsten

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28
Q

Line focus principle

A

allows for large actual FSS and small effective FSS

actual FSS is large to dissipate heat

small effective FSS allows for small detail

different angled tubes for different effective FSS (the larger the angle, the larger the effective FSS)

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29
Q

At what amperage does the thermionic emission take place in the filament

A. 1
B. 2
C. 3
D. 4

A

D. 4

21% of class correct

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30
Q

The focusing cup of the cathode must be _____ in electrical charge

A. Positive
B. Negative
C. Neutral

A

B. Negative

positive only when timer is present in grid x-ray tubes

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31
Q

increasing the anode angle from 7 to 15 degrees causes a _____ in the EFSS

A. increase
B. decrease
C. no change

A

A. increase

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32
Q

What is heel effect?

• light/dark in terms of exposure?

A

X-ray intensity on cathode side is more intense than the anode side

(because of the thickness of the disc of the anode)

Darker = more exposure
Lighter = less exposure
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33
Q

Small focal spots have limited/small _____ __ _____

A

Small focal spots have limited/small fields of view (FoV)

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34
Q

What is an application of anode heel effect?

A

Thicker parts of body towards cathode end

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35
Q

What is the beam intensity at the CR

A

100%

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36
Q

What can a single excessive exposure do

A

Causes pitting, melting, target vaporization, and cracking

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37
Q

What can long exposure (don’t hold rotor) times do

A

Causes rotor and bearings to heat leading to increased friction and imbalance of rotor

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38
Q

What is filament vaporization

A

Filament burns off and leaves a coating on the inside of the tube which disrupts electron flow and may cause arcing and sparking

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39
Q

What is the purpose of radiographic rating charts?

A

Provides safe exposure factors to be used

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40
Q

What is the purpose of anode cooling charts?

A

Illustrates the time it will take for tube to cool

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41
Q

What is the purpose of housing cooling charts?

A

Illustrates the time it takes for housing to cool

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42
Q

[*] heat units

single phase

three phase 6 pulse

three phase 12 pulse

A

HU = kVp x mA x sec

HU = 1.35 x kVp x mA x sec

HU = 1.41 x kVp x mA x sec

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43
Q

How are anodes cooled down?

A

Oil and/or fan(s)

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44
Q

What do the following 3 abbreviations stand for?

S.O.D.

S.I.D.

O.I.D.

A

Source to object

Source to image distance

Object to image distance

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45
Q

How does x-ray beam production work?

• What radiation is produced?

A

The beam is produced due to the interaction of accelerated electrons from the cathode to the anode

Two types of radiation are produced, represented by the x-ray emission brem’s

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46
Q

[*] __% of the kinetic energy from the electrons is converted into heat at the anode, while the other __% is used to create x-rays

A

99% of the kinetic energy from the electrons is converted into heat at the anode, while the other 1% is used to create x-rays

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47
Q

Increases in _____ do not improve the efficiency of production; however, increases in _____ does.

A

Increases in current do not improve the efficiency of production; however, increases in kVp does.

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48
Q

Increases in _____ do not improve the efficiency of production; however, increases in _____ does.

A

Increases in current do not improve the efficiency of production; however, increases in kVp does.

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49
Q

A K shell electron was removed with a binding energy of 69 KeV, it was replaced by an L shell electron with a binding energy of 12 keV, what’s my x-ray’s energy?

A

57 keV

69 - 12 = 57

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50
Q

[*] what shell gives us a useful x-ray

A

K shell

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51
Q

An M shell electron with the keV of 3 is replaced by P shell keV of ~0 — what’s my x-ray’s energy?

A

3 keV

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52
Q

The keV of the K shell in tungsten

A

69 keV

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53
Q

[*] Can I have a [useful] characteristic interaction with the K shell electron if the incoming electron is 50 keV

A

No, because it’s not strong enough to bounce the 69 keV electron out

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54
Q

__ - __% of x-ray beam is Brem’s

A

85-100% of x-ray beam is Brem’s

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55
Q

To increase the KE of an electron one may _____.

A. increase the e- mass

B. increase the e- velocity

C. E- KE cannot be changed

A

B. increase the e- velocity

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56
Q

What percent of the electrons reaching the anode creates x-rays

A. 1
B. 10
C. 100

A

A. 1

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57
Q

Characteristic radiation production requires

A. Slowing of electrons

B. Electron removal from an atom

C. Electron addition to atom

D. None of the above

A

B. Electron removal from an atom

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58
Q

Brem’s radiation production @ 70% kVp accounts for what % of the beam

A. 15
B. 50
C. 85
D. 100

A

C. 85%

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59
Q

What is emission spectrum

A

Illustrates the different x-ray energies present in the beam

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60
Q

What is the 15% rule

A

An increase of 15% in kV equals a doubling of mAs

A decrease of 15% kV quals in halving the amount of mAs

(higher efficiency with kV increase + less exposure than using 2x mAs for the same image)

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61
Q

Why do we filter the beam?

• Why is it done?

A

Reduces quantity of beam while increasing average quality of beam

Low energy x-rays filtered out and high energy x-rays to patient (low unnecessary radiation sent to patient)

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62
Q

Increasing the atomic number _____ the amount of Brem’s and _____ the energy of the rays.

A

Increasing the atomic number increases the amount of Brem’s and increases the energy of the rays.

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63
Q

If I increase mAs what happens to the emission spectrum

A

Height change, same shape

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64
Q

An x-ray beam may be described as which of the following

A. Mono-energetic
B. Poly-energetic
C. Homogenous
D. Heterochromatic

A

B. Poly-energetic

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65
Q

The emission spectrum crosses the X-axis at what percentage of the kVp

A. 100
B. 10
C. 1
D. 0.1

A

A. 100

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66
Q

An increase in the amplitude of the emission spectrum only indicates an increase in _____?

A. kVp
B. filtration
C. generator
D. mA

A

D. mA

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67
Q

The three essential conditions for the production of x-rays?

A
  • source of free electrons
  • acceleration of electrons
  • deceleration of electrons
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68
Q

The three essential parts of an x-ray system?

A
  • Control console
  • High-voltage generator
  • X-ray tube
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69
Q

What controls the quality of the X-ray beam?

A

kVp

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70
Q

What controls the quantity of the X-ray beam?

A

mA

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71
Q

What does an autotransformer do?

A

Provides exact, constant voltage to equipment in the low voltage side of the circuit

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72
Q

What does the filament transformer do?

A

Decreases voltage, increasing current

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73
Q

What current is required for thermionic emission to happen?

• How is this current creation accomplished?

A

high-amperage

(friction between electrons produced to heat wire)

• Accomplished through a step-down transformer + resistors

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74
Q

What are the 3 advantages to AEC?

A
  • Consistent exposures
  • Reducing repeated exposures
  • Reducing radiation exposure to patients
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75
Q

What are the usual kVp ranges in diagnostic imaging (WIP: see page 140, I have it for generators but need the typical range)

  • Single-phase?
  • 3-phase, 6 phase?
  • 3-phase, 12 phase?
  • High-frequency?
A

Single-phase = 33%

3-phase, 6P = 91%

3-phase, 12P = 97%

High-freq. = 99%

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76
Q

What are the disadvantages to AEC?

A

Grids, cassettes, and detector plates lie behind the AEC detectors so the system has no way of knowing when they are changed

Can become a crutch for radiographers who don’t want to use manual parameters

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77
Q

What are the three components of the high-voltage circuit

A
  • Autotransformer
  • Step-up transformer
  • Rectifier bridge
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78
Q

The high-voltage current flows from cathode/anode to cathode/anode.

A

The high-voltage current flows from cathode to anode.

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79
Q

What is voltage rectification and why do we need it?

• Where does voltage rectification take place?

A

Voltage rectification ensures that electrons will always enter the x-ray tube in the right direction at the filament end—no matter which way the electrons flow into the rectifier bridge

• Takes place in the high-voltage section and is the last step before sending electricity to the x-ray tube

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80
Q

Amperage is the measure of _____.

A

Current

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81
Q

What is the voltage ripple for the 5 types of generators?

  • Single-phase, half-wave?
  • Single-phase, full-wave?
  • 3-phase, 6 phase?
  • 3-phase, 12 phase?
  • High-frequency?
A
  • Single-phase, half-wave = 100% ripple
  • Single-phase, full-wave = 100% ripple
  • 3-phase, 6 phase = 14% ripple
  • 3-phase, 12 phase = 3% ripple
  • High-frequency = ~ 1% ripple
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82
Q

What are the pulses per second for the following types of generators?

  • Single-phase, half-wave?
  • Single-phase, full-wave?
  • 3-phase, 6 phase?
  • 3-phase, 12 phase?
A
  • Single-phase, half-wave = 60 pulses
  • Single-phase, full-wave = 120 pulses
  • 3-phase, 6 phase = 360 pulses
  • 3-phase, 12 phase = 720 pulses
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83
Q

What is power rating?

A

An indication of a generator or transformer’s overall quality

(expressed in kW)

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84
Q

What is space charge effect?

A

Cloud of negative electrons surrounding the filament deters continued thermionic emission

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85
Q

What is the purpose of the filament?

A

A heated filament provides a source of free electrons, producing thermionic emission

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86
Q

What is the purpose of the focusing cup?

A

Pushes electrons back toward the middle of the beam as they leave the filament

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87
Q

What is the cathode?

A

The negatively charged end of the x-ray tube including the focusing cup and filament

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88
Q

What is the purpose of the anode?

A

Positively charged side of the x-ray tube allows for electrons to come from negative cathode

89
Q

What is the purpose of focal spots?

• Where is it?

A

The primary controlling factor for sharpness of recorded detail in an image

• Area on the anode target surface where the electron beam is directed to produce x-rays

90
Q

What is the atomic number of tungsten?

• At what kVp does characteristic radiation occur?

A

74

• 69 kVp

91
Q

What causes tube failure?

A

Electrical arcing is the most common cause for tube failure

• Over time, tungsten from the filament and anode vaporize and coat the inside of the tube which electricity can arc down to, zapping it and cracking the tube

92
Q

What causes tube failure?

A

Electrical arcing is the most common cause for tube failure

• Over time, tungsten from the filament and anode vaporize and coat the inside of the tube which electricity can arc down to, zapping it and cracking the tube

93
Q

What is anode heel effect?

A

The loss of x-ray output toward the anode end of the x-ray tube due to increased thickness of the anode itself

94
Q

What is Brem’s radiation?

• How is it made?

A

Account for a majority of x-rays in a beam

• As a negatively charged electron passes a positively charged nucleus of an atom, the electron begins to slow down and then emits an x-ray as a product of a loss in KE

95
Q

What is the FDA minimum filtration requirement?

A

2.5mm Al eq.

96
Q

What is the purpose of filtration?

A

It eliminates unnecessary patient exposure, blocking non-penetrating x-rays from reaching the patient (considered to be useless for creating images)

97
Q

What is off focus radiation?

A

X-rays that are produced anywhere in the x-ray tube outside of the focal spot area

98
Q

What are characteristic x-rays?

A

X-rays produced when electrons fall from higher to lower orbits in a large atom

99
Q

What is the efficiency of x-ray production?

  • Percentage of x-rays produced?
  • Percentage of bi-product produced?
A

Low efficiency

  • 0.5 % of the energy deposited by projectile electrons into the anode is converted into x-rays
  • 99.5% is lost as heat, infrared, and light
100
Q

Describe the importance of target material

A

The higher the atomic number of the material, the more efficient it is and more x-rays are produced

Higher atomic number of target material also improves the quality of an x-ray beam

101
Q

What is emission spectrum?

  • On the graph, what will a change in mAs look like?
  • On the graph, what will a change in kVp look like?
  • On the graph, what will a change in filtration look like?
A

Illustrates the different energy x-rays present in a beam and how many of each respective energy there are

  • Shows effects of altering kVp, mAs, time or filtration
  • Change in mAs = change in amplitude, height of spectrum, but not shape
  • Change in kVp = change in both the amplitude and a shift to the right for an increase or left for a decrease
  • Change in filtration = less amplitude and low keV
102
Q

What is a stator?

A

Electromagnetic induction motor that spins anode using magnets around the neck of the tube

103
Q

What is a rotor?

A

Electromagnetic shaft powered by current to spin the anode

104
Q

When should you ramp up the rotor?

A

For crying babies and old patients

105
Q

Soft tissues require stronger/weaker x-ray beams compared to normal x-ray images

A

Weaker x-ray beams

106
Q

A vacuum (Collige) tube allows for increase/decreased efficiency

A

Increased efficiency

107
Q

Average kVp range?

A

50-150

108
Q

Average mAs range?

A

2-400

109
Q

True/False?

As the kinetic energy of the incident electron increases, so does the efficiency of the photon production.

A

True

110
Q

True/False?

In the diagnostic range, the kinetic energy of the incident electrons is high enough to eject an outer-shell electron causing ionization.

A

True

111
Q

True/False?

In a bremsstrahlung interaction, the closer the incident electron travels to the nucleus, the lower the energy of the resultant x-ray photon.

A

False

112
Q

True/False?

The electron ejected during a characteristic interaction is also known as the x-ray photon.

A

False

113
Q

True/False?

The creation of a characteristic photon is always the result of a K-shell electron ejection.

A

False

114
Q

True/False?

The creation of a characteristic photon in the diagnostic range is always the result of a K-shell electron ejection.

A

False

115
Q

True/False?

As the tube ages, the anode begins to pit and the glass envelope may gain a mild coating of vaporized metal. This will cause a decrease in inherent filtration.

A

False

116
Q

True/False?

Inherent filtration is the filtration found within the tube design.

A

True

117
Q

True/False?

In diagnostic radiology, filtration is typically added between the source and the patient.

A

True

118
Q

Almost all of the kinetic energy of the incident electrons is converted to:

a. a bremsstrahlung photon
b. a characteristic x-ray photon
c. light
d. heat

A

d. heat

119
Q

What percentage of target interaction results in the production of x-ray photons?

a. 1 percent
b. 50 percent
c. 99 percent
d. 100 percent

A

a. 1 percent

120
Q

The transfer of the incident electrons’ kinetic energy to the outer-shell electrons causing vibration of the outer-shell electron results in the emission of:

a. infrared radiation.
b. ultraviolet radiation.
c. light.
d. sound.

A

a. infrared radiation.

121
Q

The types of target interaction that occur in the production of diagnostic-range x-ray photons are dependent upon:

a. electron kinetic energy.
b. nuclear binding energy.
c. electron potential energy.
d. both a and b

A

a. electron kinetic energy.

122
Q

The energy of a bremsstrahlung photon is
a. equal to the kinetic energy of the entering electron.

b. equal to the kinetic energy of the exiting electron.
c. the sum of the entering and exiting kinetic energy of the electron.
d. the difference between the entering and exiting kinetic energy of the electron.

A

d. the difference between the entering and exiting kinetic energy of the electron.

123
Q

Bremsstrahlung interactions may occur only when the incident electron interacts with:

a. an inner-shell electron.
b. an outer-shell electron.
c. the force field of the nucleus.
d. none of the above

A

c. the force field of the nucleus.

124
Q

Characteristic interactions may occur only when the incident electron interacts with:

a. an inner-shell electron.
b. an outer-shell electron.
c. the force field of the nucleus.
d. none of the above

A

a. an inner-shell electron.

125
Q

During a characteristic interaction, the energy of the incident electron must be ____ the electron it knocks from its orbit.

a. less than that of
b. greater than that of
c. proportional to that of
d. characteristic of

A

b. greater than that of

126
Q

During a characteristic interaction, the dropping of a higher-energy state electron into a lower-energy state “hole” results in the emission of:

a. a photon of energy.
b. a high-energy electron.
c. a low-energy electron.
d. more than one of the above

A

a. a photon of energy.

127
Q

The energy of a characteristic photon is:

a. equal to the binding energy of the entering electron.
b. equal to the binding energy of the exiting electron.
c. the sum of the binding energy of the outer and inner shells between which the electron dropped.
d. the difference between the binding energy of the outer and inner shells between which the electron dropped.

A

d. the difference between the binding energy of the outer and inner shells between which the electron dropped.

128
Q

At the end of the characteristic cascade, the ____ shell is missing an electron.

a. innermost
b. K
c. outermost
d. characteristic

A

c. outermost

129
Q

The K-shell can hold a maximum of ____ electrons.

a. 1
b. 2
c. 6
d. 8

A

b. 2

130
Q

Filtration is the process of eliminating undesirable ____ by the insertion of absorbing materials into the primary beam.

a. high-energy x-ray photons
b. high-energy incident electrons
c. low-energy x-ray photons
d. low-energy incident electrons

A

c. low-energy x-ray photons

131
Q

Filtration permits the radiographer to ____ the photon emission spectrum into a more useful beam.

a. narrow
b. widen
c. soften
d. There is no effect.

A

a. narrow

132
Q
  1. Filtration has what effect on patient dose?
    a. It has no effect on patient dose.
    b. It increases patient dose.
    c. It decreases patient dose.
    d. It increases occupational worker dose.
A

c. It decreases patient dose.

133
Q
  1. Which of the following materials is/are used as a filter?
    a. glass
    b. oil
    c. aluminum
    d. all of the above
A

d. all of the above

134
Q

All filtration can be expressed in terms of the thickness of:

a. HVL.
b. Pb/Eq.
c. Al/Eq.
d. Sn/Eq..

A

c. Al/Eq.

135
Q

The amount of material that will reduce the intensity of the primary beam to one-half its original value is the:

a. half-value layer.
b. radioactive half-life.
c. aluminum equivalency.
d. half-life equivalency.

A

a. half-value layer.

136
Q

Which of the following is affected by half-layer value?

a. anode construction
b. image quality
c. target longevity
d. patient exposure

A

d. patient exposure

137
Q

How many half-value layers must be added to the primary beam to reduce its intensity to less than 20 percent of its original value?

a. 1
b. 2
c. 3
d. 4

A

c. 3

138
Q

Which one of these statements is true?

a. The thickest portion of the wedge filter is placed over the densest part of the patient.
b. The thickest portion of the wedge filter is placed over the less dense part of the patient.
c. The thinnest portion of the wedge filter is placed over the less dense part of the patient.
d. A wedge filter should not be used to compensate for unequal subject density.

A

b. The thickest portion of the wedge filter is placed over the less dense part of the patient.

139
Q

True/False?

AC current is required in the x-ray tube, and DC current is required in the transformers

A

False

140
Q

The filament in the x-ray tube requires ______ amperes to emit electrons, thermionic emission.

0.5-1

1-2

3-5

not enough information to answer

A

3-5

141
Q

True/False?

The high voltage generator consistes of a high voltage transformer, rectifiers and an autotransformer

A

False

142
Q

The most likely found incoming line current in a modern radiography system is:

single phase power

three phase power

direct current

~ 60 volts

A

three phase power

143
Q

The incoming power to a step up transformer is 100 V, 10 A with a turns ration of 250:1.

What is the resulting voltage in this transformer?

25,000 kV
25,000 V
0.4 kV
0.4 V

A

25,000 V

144
Q

The voltage in the x-ray circuit is adjusted or fine tuned in the __________ for ease and safety.

filament transformer

high voltage transformer

rectifier circuit

autotransformer

A

autotransformer

145
Q

An induction motor is used in what area of imaging?

rotor rotation

power increase

x-ray table movement

all of the above

A

rotor rotation

146
Q

A filament transformer with a turns ration of 1:20 provides 3.1 amperes to the filament. What is the current flowing through the primary coil of the transformer?

62

  1. 2
  2. 55

.155

A

.155

147
Q

True/False

In single phase power systems, the potential never drops to zero.

A

False

148
Q

When full wave rectification is applied to three phase current, a varying(slight increases and decreases over time) ____ is produced.

current

star

double

voltage

A

voltage

149
Q

The electrical device used to adjust the mA station is the

autotransformer

stator

switch

precision resistor

A

precision resistor

150
Q

Nearly all hard wired equipment operates on incoming line voltage of

440 V

120 AC

120 Hz

210 A

A

440 V

151
Q

All of the following are radiographer operated controls except

kVp selection

generator selection

rotor switch

mA selection

A

generator selection

152
Q

A step down transformer has ______ windings in the secondary vs. primary side.

less

more

the same

none of the above

A

less

153
Q

True/False?

The basic x-ray circuit is divided into the main circuit and the anode circuit.

A

False

154
Q

A single phase full wave rectified system produces _____ pulses per cycle.

1

2

6

12

A

2

155
Q

True/False?

The mAs in a system controls the quality of the beam.

A

False

156
Q

At what point in the x-ray circuit is the rectification circuit located?

between the semiconductors and the valve tubes

between the step down transformer and the rheostat

between the step up transformer and the x-ray tube

between the thermionic diode tubes and the x-ray tube

A

between the step up transformer and the x-ray tube

157
Q

Which of the following transformers has one winding?

Filament transformer

Hi voltage transformer

Autotransformer

none of the above

A

Autotransformer

158
Q

Which of the following waveforms has the highest efficiency?

Three phase 6 pulse

Three phase 12 pulse

Single phase full wave

All are equal

A

Three phase 12 pulse

159
Q

What is the typical turns ratio?

A

500:1 and 1000:1

160
Q

The voltage input to an x-ray transformer is most likely _____.

A. 60
B. 220
C. 660
D. >660

A

B. 220

161
Q

A typical turns ratio in a step-up transformer is most likely _____.

A. 7:1
B. 70:1
C. 700:1
D. 7000:1

A

C. 700:1

162
Q

Variation of x-ray tube voltage with time is best described as the:

A. ripple
B. pulse frequency
C. uniformity
D. nonlinearity

A

A. ripple

163
Q

The percentage of ripple of a high-frequency generator is most likely:

A. 1
B. 5
C. 10
D. >10

A

A. 1

164
Q

The number of pulses per cycle of a half-wave rectified single-phase generator is _____.

A. 1/2
B. 1
C. 2
D. 6

A

B. 1

165
Q

Which generator has the lowest ripple?

A. single pulse
B. six pulse
C. twelve pulse
D. high-frequency

A

D. high-frequncy

166
Q

Which generator is most likely to reduce the kVp during an exposure?

A. portable
B. dedicated chest
C. R/F unit
D. Interventional radiology

A

A. portable

167
Q

The maximum distance (mm) energetic electrons travel to the x-ray tube tungsten target is most likely _____.

A. 0.05
B. 0.5
C. 5
D. 50

A

B. 0.5

168
Q

The maximum Bremasstrahlung energy (keV) produced at 80 kVp is most likely _____.

A. 100
B. 80
C. 70
D. 35

A

B. 80

169
Q

The percentage of Bremasstrahlung radiation at 120 kVp is most likely _____%.

A. 1
B. 10
C. 50
D. 90

A

D. 90

170
Q

The average Bremsstrahlung energy (keV) produced at 100 kVp is most likely _____.

A. 100
B. 70
C. 55
D. 40

A

D. 40

171
Q

Tungsten characteristic K-shell x-rays have an energy (keV) of _____.

A. 85
B. 65
C. 35
D. 18

A

B. 65

172
Q

The percentage of K-shell characteristic x-rays at 55 kVp in a tungsten target is _____.

A. 0
B. 5
C. 10
D. >10

A

A. 0

173
Q

An x-ray spectrum shows a graph of the number of photons on the vertical axis against _____ on the horizontal axis.

A. kVp
B. keV
C. mAs
D. mA

A

B. keV

174
Q

The highest intensity in a spectrum from a tungsten target is most likely at the _____.

A. low energies
B. middle energies
C. high energies
D. low and high energies

A

B. middle energies

175
Q

1 roentgen is approx. equal to _____ mGy.

A. 0.1
B. 1
C. 10
D. 100

A

C. 10

176
Q

An x-ray tube current is a flow of:

A. electrons
B. protons
C. neutrons
D. ionized atoms

A

A. electrons

177
Q

Doubling the x-ray tube current, and quadrupling exposure time, increases x-ray tube output by _____.

A. 2x
B. 4x
C. 8x
D. 16x

A

C. 8x

178
Q

The most likely x-ray tube output (mGy/mAs) 100cm from the x-ray tube focus is most likely _____.

A. 0.05
B. 0.5
C. 5
D. 50

A

A. 0.05

179
Q

Doubling the mAs increases x-ray production efficiency by ______%.

A. 0
B. 10
C. 50
D. 100

A

A. 0

180
Q

Doubling the x-ray tube voltage would likely increase the x-ray tube output by _____%.

A. 50
B. 100
C. 200
D. 400

A

D. 400

181
Q

Doubling the x-ray tube voltage would likely increase the x-ray tube output by _____%.

A. 50
B. 100
C. 200
D. 400

A

D. 400

182
Q

Doubling the x-ray tube mAs is equivalent to increasing the x-ray tube voltage by _____%.

A. 5
B. 15
C. 50
D. 100

A

B. 15

183
Q

Which x-ray component is most likely to store the heat generated during an x-ray?

A. anode
B. cathode
C. target
D. filament

A

A. anode

184
Q

The formula for computing the generator power is:

A. voltage + current
B. voltage • current
C. voltage / current
D. (voltage / current)^-1

A

B. voltage • current

185
Q

Anode heat capacity is most likely expressed in terms of:

A. heat units
B. watts
C. temperature
D. specific heat

A

A. heat units

186
Q

How many heat units is 1J?

A. 0.35
B. 0.7
C. 1.35
D. 1.7

A

C. 1.35

187
Q

Which of the following is not a method for heat dissipation?

A. conduction
B. radiation
C. convection
D. spallation

A

D. spallation

188
Q

The length of an x-ray tube filament is most likely _____ mm.

A. 0.15
B. 1.5
C. 15
D. 150

A

B. 1.5

189
Q

X-ray tube filaments are most likely made of:

A. moly
B. silver
C. tungsten
D. lead

A

C. tungsten

190
Q

The most likely x-ray tube filament current is _____ A.

A. 0.04
B. 0.4
C. 4
D. 40

A

C. 4

191
Q

The melting point of tungsten targets in x-ray tubes is most likely _____ °C.

A. 34
B. 340
C. 3,400
D. 34,000

A

C. 3,400

192
Q

The material added to tungsten targets in x-ray tubes is most likely:

A. rhenium
B. silver
C. thorium
D. iron

A

A. rhenium

193
Q

The target of a mammography x-ray tube is most likely:

A. moly
B. silver
C. aluminum
D. copper

A

A. moly

194
Q

X-ray tube targets are most likely embedded in the:

A. anode
B. cathode
C. housing
D. focusing grid

A

A. anode

195
Q

The most likely rotation speed of an anode in a chest radiograph x-ray tube is _____ RPM.

A. 50
B. 500
C. 5,000
D. 50,000

A

C. 5,000

196
Q

The type of gas in an x-ray tube is most likely:

A. air
B. oxygen
C. nitrogen
D. none (vacuum)

A

D. none (vacuum)

197
Q

Vaporized tungsten coated on the x-ray tube glass envelope is most likely to result in:

A. arcing
B. leakage radiation
C. gas leaks
D. secondary radiation

A

A. arcing

198
Q

X-ray production in an x-ray tube is most likely to be emitted towards:

A. anode
B. cathode
C. filament
D. isotropically

A

D. isotropically

199
Q

The area of an x-ray window is most likely _____ cm^2.

A. 5
B. 50
C. 500
D. 5000

A

A. 5

200
Q

Radiation that escapes through the protective housing is most likely called:

A. primary
B. secondary
C. leakage
D. scatter

A

C. leakage

201
Q

The most likely material between the protective housing and the x-ray tube is:

A. oil
B. water
C. air
D. acrylic

A

A. oil

202
Q

The shape of an aperture diaphragm is least likely a(n):

A. circle
B. square
C. rectangle
D. ellipse

A

D. ellipse

203
Q

Field size is most severely restricted by use of a(n):

A. cylinder
B. cone
C. diaphragm
D. alignment mirror

A

A. cylinder

204
Q

The lead thickness of collimator leaves is most likely _____ mm.

A. 0.003
B. 0.03
C. 0.3
D. 3

A

D. 3

205
Q

The minimum filtration required in a diagnostic x-ray tube is most likely _____ mm Al.

A. 1.0
B. 1.5
C. 2.5
D. 4.0

A

C. 2.5

206
Q

Added filtration is most likely made of:

A. moly
B. rhenium
C. aluminum
D. silver

A

C. aluminum

207
Q

The inherent aluminum equivalence of light mirror is most likely _____ mm.

A. 0.01
B. 0.3
C. 1
D. 3

A

C. 1

208
Q

The small focal spot size in a conventional (W target) x-ray tube is most likely _____ mm.

A. 0.1
B. 0.3
C. 0.6
D. 1.2

A

C. 0.6

209
Q

The limiting tube current on a small focal spot size is most likely _____ mA.

A. 3
B. 30
C. 300
D. 3000

A

C. 300

210
Q

The maximum tube current for a typical diagnostic x-ray tube is most likely _____ mA.

A. 100
B. 1,000
C. 10,000
D. 100,000

A

B. 1,000

211
Q

The maximum tube voltage for a typical diagnostic x-ray tube is most likely _____ kV.

A. 15
B. 150
C. 1,500
D. 15,000

A

B. 150

212
Q

The most likely exposure time(s) for a synchronous timer would be _____ second.

A. 1/50
B. 1/60
C. 1/70
D. 1/80

A

B. 1/60

213
Q

The lowest exposure time of an electronic timer is most likely _____ second.

A. 0.001
B. 0.003
C. 0.010
D. 0.030

A

A. 0.001

214
Q

The most important factor affecting the heel effect is most likely the anode:

A. angle
B. rotation
C. size
D. density

A

A. angle

215
Q

Which field size (cm x cm) is likely to show the highest heel effect?

A. 35 x 43
B. 30 x 35
C. 24 x 30
D. 18 x 25

A

A. 35 x 43

216
Q

Off-focus radiation is best controlled by the use of:

A. high kVp
B. high mA
C. collimators
D. a grid

A

C. collimators

217
Q

X-ray tubes that are used with reduced techniques are most likely to have:

A. longer lives
B. off-focus radiation
C. microprocessor failures
D. repeat rates

A

A. longer lives

218
Q

Which target will result in the most x-rays, assuming a constant x-ray tube kVp?

A. Mo
B. Rh
C. W
D. no difference (all the same)

A

C. W

2016FA PHYSICS (K. Greene) (13 decks)

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