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Radt 1303 Physics > Comprehensive Exam > Flashcards

Comprehensive Exam Flashcards

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1
Q

what does ALARA mean?

A

As Low as Reasonably Achievable

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2
Q

Which of the following is a cardinal rule of radiation protection?

A

increase the distance from the source

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3
Q

Increased kVp has what effect on photoelectric (PE) absorption?

A

decreases PE absorption

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4
Q

To increase the quantity of radiation by adjusting the kVp to the same level as doubling the mAs, you need to increase kVp by a fact of what percentage?

A

15%

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5
Q

the rate of photoelectric absorption interactions _________ faster than the rate of Compton scattering

A

decreases

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6
Q

Exposure, dose, and dose equivalent are:

A

radiologic quantities

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7
Q

What is an expression of the relative risk to humans of exposure to ionizing radiation?

A

effective dose

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8
Q

factors affecting the photoelectric-compton ratio

A

Z# of the material
Photon energy

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9
Q

The probability of photoelectric interaction depends on the following:

A

The atomic number of the tissue atoms with which they interact
The incident x-ray photon energy

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10
Q

how does a higher atomic number (Z) affect PE absorption?

A

increases PE absorption

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11
Q

a radiolucent structure likely has which of the following properties?

A

low atomic number

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12
Q

the probability of compton scattering depends on the atomic number. true or false?

A

false

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13
Q

_____ creates less radiographic density

A

metal

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14
Q

____ creates more radiographic density

A

air

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15
Q

to produce a radiographic image that represents anatomy, which interactions must be present?

A

differential absorption, transmitted photons, photoelectric interactions

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16
Q

_______ dose is calculated for individual organs.
It is based on the absorbed dose to an organ, adjusted to account for the effectiveness of the type of radiation.
This dose is expressed in millisieverts (mSv) to an organ

A

Equivalent

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17
Q

_______ dose is calculated for the whole body.
It is the addition of equivalent doses to all organs, each adjusted to account for the sensitivity of the organ to radiation.
This dose is expressed in millisieverts (mSv)

A

Effective

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18
Q

What is atomic number?

A

the Z#
it represents the nuclear charge
the number of protons & neutrons in an atom

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19
Q

What is described as the rate of change in velocity over time?

A

acceleration

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20
Q

What is the equation for velocity?

A

velocity = distance / time

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21
Q

Based on the anode heel effect, an image taken at 40 inches SID distance may demonstrate:

A

decreases exposure towards the anode end of the beam

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22
Q

Assuming all other factors are accurately adjusted, the exposure time with AEC is adjusted to accommodate changes in:

A

patient anatomy

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23
Q

In an automatic exposure control system (AEC), where are the detectors placed?

A

between the patient and image receptor

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24
Q

Which term is the electromotive force or potential energy that produces electron movement?

A

voltage

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25
Q

The maximum number of electrons in each shell is found by using the equation:

A

2N^2
(N = shell number, ex: K = 1, L = 2, M = 3)

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26
Q

What is the average energy of the x-ray beam called?

A

beam quality

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27
Q

Which of the following exposure factors must be selected on the console which increases the quality and penetration of the x-ray beam?

A

kVp

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28
Q

What term defines the total number of x-ray photons in a beam?

A

x-ray quantity

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29
Q

Which term describes the reduction of the x-ray beam’s intensity as is passes through matter?

A

attenuation

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30
Q

What electromagnetic radiation has the lowest frequency?

A

radiowaves

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31
Q

What electromagnetic radiation has the highest frequency?

A

gamma rays

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32
Q

Members of electromagnetic spectrum from lowest to highest energy

A

Radiowaves
Microwaves
Infrared light
Visible light
Ultraviolet light
X-rays
Gamma rays

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33
Q

What unit is used to measure the frequency of a wave?

A

Hertz

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34
Q

electron shells # of electrons and binding energy from least to most

A

Q (7) 98 e-
P (6) 72 e-
O (5) 50 e-
N (4) 32 e-
M (3) 18 e-
L (2) 8 e-
K (1) 2e-

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35
Q

As the wavelength of a wave increases, how will frequency change proportionately?

A

decreases

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36
Q

What effect does frequency increasing have on energy?

A

increases energy

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37
Q

If the wavelength of a beam of electromagnetic radiation increases by a factor of 2, what happens to its frequency?

A

decreased by 1/2 (half)

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38
Q

Wavelength and frequency are:

A

inversely proportional

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39
Q

Which law states that the voltage (V) is equal to the product of the current (I) flowing through a conductor and the resistance (R) of that conductor?

A

ohm’s law

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40
Q

Which characteristic of a conductor will create the least resistance to the flow of electrons?

A

decreased temperature

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41
Q

A material that freely allows the flow of electrons is known as:

A

conductor

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42
Q

What does the anode function as?

A

a target for electrons, an electrical conductor, a conductor for heat

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43
Q

The property of an element in a circuit that resists or impedes the flow of electricity:

A

resistance (ohm)

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44
Q

What is the unit of measure for power?

A

watts

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45
Q

What does the ampere measure?

A

electric current

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46
Q

The potential difference that will maintain a current of 1 ampere in a circuit with a resistance of 1 ohm is the definition of:

A

volt

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47
Q

Coulomb’s law (calculation)

A

F = k (Q1 Q2 / d^2)

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48
Q

a volt is the ratio of _____ to _______

A

joules to coulombs
volt = joules/coulombs

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49
Q

1 coulomb is equal to the electrical charge of _________ electrons

A

6.25 x 10^18

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50
Q

How can you double the beam quantity?

A

double the mAs

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51
Q

In which direction is the correct flow of electrons?

A

from a negative cathode toward a positive anode

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52
Q

Which type of current is created by use of rectifiers?

A

direct current

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53
Q

electrons flow in only one direction (cathode to anode)
waveform begins at zero and moves to its maximum potential at its peak
ex: batteries and rectifiers

A

direct current (DC)

54
Q

electrons flow in one direction for the first half of the cycle and then in the other for the second half of the cycle
ex: U.S. current (60 Hz)
positive cycle: 1/120 second

A

alternating current (AC)

55
Q

the potential difference (voltage) across the total circuit or any part of that circuit is equal to the current (amperes) multiplied by the resistance

A

ohm’s law

56
Q

What is it called when a moving magnetic field (created by AC) is placed near a secondary coil, and electricity is induced to flow in the secondary coil

A

mutual induction

57
Q

What conditions and materials are necessary for mutual induction to occur?

A

magnetic flux and a solenoid

58
Q

The _____ is the SI unit equivalent to the Curie which measures radioactivity

A

Becquerel

59
Q

What is used to convert AC to DC?

A

rectifiers

60
Q

transformer law for voltage:

A

Vs / Vp = Ns / Np

61
Q

transformer law for current:

A

Is / Ip = Np / Ns

62
Q

the relation of voltage to current in a transformer is:

A

Is / Ip = Vp / Vs

63
Q

A step-up transformer ______ voltage and a step down transformer ______ voltage

A

increases, decreases

64
Q

Where is the step-down transformer located?

A

filament ciruit

65
Q

By regulation, x-ray tube leakage radiation can be no more than:

A

100 mR per hour at a distance of one meter

66
Q

to help dissipate the heat produced during x-ray production, what fills the x-ray tube housing?

A

oil

67
Q

Place the following events leading to the production of x-rays in order, from first to last:
1. alternating current is converted to direct current
2. voltage is adjusted at the autotransformer
3. kilovoltage leaves the step up transformer
4. voltage goes to primary side of the step up transformer

A

2, 4, 3, 1

68
Q

Place the following events leading to the production of x-rays in order, from first to last:
1. resistance is adjusted at the rheostat
2. filament is heated
3. filament current is increased
4. electrons are boiled off filament

A

1, 3, 2, 4

69
Q

Which are a part of an AC induction motor?

A

stator and rotor

70
Q

Where are the ionization chambers?

A

between the patient and image receptor

71
Q

Electricity coming from the wall. Hz, Volts, etc.

A

AC at the wall outlet is 60 Hz

72
Q

Which part of the x-ray circuit functions by means of self-induction?

A

autotransformer

73
Q

Where are the rectifiers located?

A

secondary circuit

74
Q

Where is the rheostat located?

A

filament circuit

75
Q

Where is the timer circuit located?

A

primary circuit

76
Q

What is the purpose of the filament circuit?

A

boil off electrons, provide additional energy

77
Q

A tungsten button embedded in a copper rod
The target does not move.
Disadvantage: the rapidly building heat can damage the tube, which limits use

A

stationary (static) anode

78
Q

Why is molybdenum used in a rotating anode?

A

it is light but strong

79
Q

Which is an advantage of angling the anode?

A

spreads the heat generated over a larger area of the anode

80
Q

heat units definition & calculation

A

a measure of the amount of heat stored in a particular device
kVp x mA x s x c

81
Q

calculation for single phase

A

mA X time X kVp

82
Q

calculation for three phase

A

mA X time X kVp X 1.35

83
Q

calculation for high frequency:

A

mA X time X kVp X 1.40

84
Q

Involves the K-shell (first shell around the nucleus, has the strongest binding energy)
Only the interactions involving K-shell are of sufficient energy to be useful

A

Characteristics Interactions

85
Q

The tissue atom is ionized and the inner-shell vacancy makes the
atom unstable
To regain stability, a ________________ occurs, producing secondary x-ray photons
These secondary photons are of low energy, are absorbed by the body in other photoelectric events, and contribute to patient dose

A

characteristic cascade
photoelectric interactions

86
Q

The incident x-ray photon interacts with the inner-shell electron of a tissue atom and removes it from orbit
X-ray photons are totally absorbed

A

photoelectric interaction

87
Q

During the bremsstrahlung interaction, what happens to the filament electron?

A

it is attracted to the nucleus

88
Q

through what type of interaction are the majority of x-rays produced?

A

bremsstrahlung

89
Q

What increases the “average” energy of an x-ray beam?

A

added filtration

90
Q

What influences quality and quantity of the x-ray beam?

A

quality: kVp
quantity: mAs

91
Q

What energy does the incident photon need to enable the photoelectric effect / absorption?

A

it needs to be the same or greater than the binding energy of an inner-shell electron

92
Q

What is the minimum amount of energy an x-ray photon must have to create a pair production?

A

1.02 MeV

93
Q

Is the x-ray beam heterogeneous or homogenous?

A

heterogeneous

94
Q

What metal is used for filtration? Collimators? Protection?

A

filtration: aluminum
collimators: tungsten
protection: lead

95
Q

the result of the formation of limb’s as a result of irradiation that stick to adjacent parts of the macromolecule or neighboring molecules, creating an unnatural framework

A

cross-linking

96
Q

refers to a breakage of the major structure (framework) of the macromolecule itself

A

main chain scission

97
Q

the result of damage to a single chemical bond

A

point lesions

98
Q

one half-value layer (HVL) reduces the intensity of the x-ray beam to _____ of its original

A

one half

99
Q

measures beam quality
defined as the thickness of absorbing material necessary to reduce the energy of the beam to one-half its original intensity
found by measuring beam intensity with a radiation detector

A

half value layer (HVL)

100
Q

what is the normal HVL of a diagnostic beam?

A

3-5 mm Al

101
Q

Why would an anode crack?

A

maximum heat or exposure factors

102
Q

Anode heel effect. Which side has more intensity?

A

cathode

103
Q

Stator and rotor. Where are they?

A

stator: outside the tube enclosure
rotor: iron core, surrounded by coils, located in center of stator within enclosure

104
Q

Photoelectron calculation

A

Ei = Eb + Eke
Ei = Incident photon energy
Eb = Electron binding energy
Eke = Photoelectron kinetic
energy

105
Q

What tissues have more PE interactions?

A

those with higher atomic numbers

106
Q

Where does the technologist get their dose?

A

compton back scattering

107
Q

In which interaction with matter does an x-ray interact with an atom without ionizing it?

A

coherent scattering

108
Q

SI unit for mass?

A

kilogram

109
Q

Which is the most radiosensitive molecule in the body?

A

DNA

110
Q

Which describes the force that holds the protons and neutrons. together in the nucleus?

A

Nuclear binding energy

111
Q

At what speed do electromagnetic waves travel?

A

speed of light: 3 x 10^8 m/s

112
Q

Planks formula for wavelength:

A

wavelength = constant / frequency
(constant = 3 x 10^8 m/s)

113
Q

Planks formula for energy:

A

E = hf
(h = 6.626 x 10^-34 J sec)

114
Q

Plank’s formula for frequency:

A

f = c / λ
(constant = 3 x 10^8 m/s)

115
Q

What is the velocity of electromagnetic radiation?

A

3 x 10^8 m/s

116
Q

On which day did Roentgen first discover x-radiation?

A

November 8, 1895

117
Q

the length of time it takes for half the remaining atoms in an amount of the element to decay

A

half-life

118
Q

inverse square law

A

I1 / I2 = d2^2 / d1^2

119
Q

Three-phase, full-wave rectification has what percentage of ripple?

A

13% to 3.5%

120
Q

Single-phase full-wave rectified current has what percentage of ripple?

A

100%

121
Q

Which has the least amount of ripple?

A

high frequency generators
(<1% ripple)

122
Q

An adjustable transformer
controlled by the kilovolt peak (kVp) selector on the
operating console

A

autotransformer

123
Q

Where is the autotransformer located?

A

primary circuit

124
Q

What is the only adjustable transformer in the x-ray circuit?

A

autotransformer

125
Q

essential to tube head assembly
the target window is the primary contributor

A

Inherent filtration

126
Q

In a general radiography tube head assembly, this comes in the form of another 2.0 mm Al placed between the target window and the top of the collimator

A

added filtration

127
Q

Serves the same role as timer
The patient’s body part of interest is the variable in
determining when to terminate exposure
Uses a device called an ionization chamber

A

Automatic exposure control (AEC) device

128
Q

The nature of magnetic materials is that the orbital electrons of their atoms spin in predominately one direction

A

electromagnetism

129
Q

The ___________ of a charged particle in motion is perpendicular to the motion of that particle.

A

magnetic field

130
Q

How is magnetic field strength measured?

A

Tesla

131
Q

Which refers to the relationship between the actual focal spot size, the effective focal spot size, and the anode target angle?

A

the line-focus principle

Radt 1303 Physics (8 decks)

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