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Freshman Exit Exam > Physics > Flashcards

Physics Flashcards

1
Q

source of rad in XR tube

A

focal spot

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2
Q

bc of line focus principle, the effective focal spot size decreases w decreasing?

A

target angle

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3
Q

high capacity tube rotors revolve at?

A

10,000 rpm

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4
Q

XR intensity (I) is lower on the anode side of the tube bc of the

A

heel effect

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5
Q

cathode side of tube should be towards the _______ part of pt

A

thicker

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6
Q

formula for heat units (HU) for a 3-phase, 6-pulse XR machine?

A

1.35 x kVp x mA x s

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7
Q

tube failure can occur from?

A

long exposure T’s

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8
Q

a dual focus tube has 2?

A

filaments

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9
Q

ea tube has it’s own tube rating chart to show?

A

max exposure T’s

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10
Q

the _______ is/are outside the glass envelope?

A

stators

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11
Q

heel effect is caused by the?

A

anode angle

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12
Q

the effective focal spot size is ________ the actual focal spot size.

A

smaller than

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13
Q

projectile e-‘s travel from?

A

cathode to anode

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14
Q

during an exposure most of the ______ energy of the projectile e-‘s is converted to _____

A

kinetic; heat

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15
Q

the efficiency of XR production increases as _____ increases

A

kVp

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16
Q

approx. ___ of the kinetic energy of the projectile e-‘s is converted to XRs at the target

A

1%

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17
Q

e- interactions @ the inner shell of target atoms produce ________ rad

A

characteristic

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18
Q

most of the heat generated at the target is due to?

A

outer-shell excitation

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19
Q

production of heat @ anode is directly proportional to?

A

tube current

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20
Q

useful characteristic XRs from tungsten targets are ______ XRs

A

K-shell

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21
Q

characteristic K-shell XRs have an effective energy of _____ keV

A

69

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22
Q

most XRs produced at the target are ________

A

bremsstrahlung

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23
Q

at 55 kVp ______ of the XRs produced are bremsstrahlung

A

100%

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24
Q

bremsstrahlung XRs are produced by _____ at the target

A

slowing e-‘s

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25
Q

characteristic XRs are produced by

A

released binding energy

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26
Q

quantity of bremsstrahlung rad increases proportionately w increased _____

A

mAs

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27
Q

an exposure taken at 100 kVp would have a continuous emission spectrum w a max energy of _____ keV

A

100

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28
Q

the ____ of an XR beam is higher when the peak of the emission spectrum is further to the ______

A

quality; right

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29
Q

an increase in mAs would _____ the ________ of the emission spectrum

A

increase; amplitude only

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30
Q

an increase in kVp would ______ the ________ of the emission spectrum

A

increase; amplitude & pos.

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31
Q

changes in ________ result in directly proportional changes in the amplitude of the emission spectrum

A

mA & T

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32
Q

the discrete portion of the XR emission spectrum would change pos. w a change in?

A

target material

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33
Q

amplitude of emission spectrum is _______ w a ________ generator than/as w a 3-phase generator

A

lower; single-phase

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34
Q

a 15% increase in kVp is = to

A

doubling mAs

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35
Q

how does added filtration affect the emission spectrum?

A

reduced amplitude and shift to R

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36
Q

Roentgens (or grays) is the measurement for XR?

A

quantity, exposure, & Intensity

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37
Q

of useful XRs in the beam defines the XR

A

quantity

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38
Q

standard XR machines produce about ____ mR/mAs at 70 kVp measured at 100cm SID

A

5

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39
Q

XR quantity increases in direct proportion to increases in?

A

mAs

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40
Q

if the distance from the source to the img (SID) is reduced by 1/2, how is the XR intensity at the img affected?

A

increased 4x’s

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41
Q

if filter thickness is _____, then XR intensity is _____

A

increased, reduced; or reduced, increased (inversely proportional)

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42
Q

a 10% increase in kVp has _____ effect on XR intensity than/as a 10% increase in mAs

A

much greater

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43
Q

if XR quantity is doubled, the optical density (OD) on the finished radiograph will be?

A

increased by a factor of 2

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44
Q

if a tech changes the technique from 70 kVp @ 200 mAs to 70 kVp @ 400 mAs, the the XR intensity will _______ and optical density (OD) will _______

A

double, double

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45
Q

the inverse square law has the same effect on optical density (OD) and XR __________

A

intensity, exposure, & quantity

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46
Q

an increase of 15% in kVp is = to increasing mAs _________

A

100%

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47
Q

if the intensity of a 70 kVp exposure at 20 mAs is 100 mR, what would it be at 5 mAs?

A

25 mR

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48
Q

if an exposure is 50 mR at an SID of 40”, what would the exposure be at an SID of 60”?

A

22.2 mR

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49
Q

XR intensity is proportional to?

A

kVp^2

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50
Q

penetrability of an XR beam is called XR _______

A

quality

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51
Q

an XR beam that should pass through dense tissue would have high?

A

penetrability & quality

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52
Q

a low quality beam would also have low?

A

penetrability

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53
Q

beam quality is affected by?

A

kVp & filtration

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54
Q

the half value layer (HVL) of XR beam is a measurement of beam?

A

quantity

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55
Q

img contrast is affected by?

A

beam quality & kVp

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56
Q

the HVL is lowered by a decrease in?

A

kVp

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57
Q

XR beam quality is improved by

A

increased filtration

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58
Q

main purpose os added filtration is to reduce

A

pt dose

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59
Q

added filtration will _____ beam quality and ______ beam quantity

A

increase, decrease

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60
Q

a compensating filter is used to create _____ optical density (OD) w a body part of ______ thickness

A

uniform; non-uniform

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61
Q

2 primary forms of XR interaction in the diagnostic range are

A

Compton scattering & photoelectric absorption

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62
Q

an incident XR interacts w an atom without ionization during __________

A

coherent scattering

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63
Q

an outer-shell e- is ejected & the atom is ionized w?

A

Compton interactions

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64
Q

which XR interaction involves the ejection of the K-shell e-?

A

photoelectric absorption

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65
Q

the scattered XR from a Compton interaction usually retains _____ of the energy of the indecent photon

A

most

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66
Q

Compton scatter is directed at (a) _______ angle from the incident beam

A

any

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67
Q

as kVp _____, the probability of photoelectric absorption ________

A

increases, decreases

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68
Q

there is complete absorption of the incident XR photon w

A

photoelectric effect

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69
Q

_________ only occurs at the very high energies used in rad therapy and in nuclear med PET imaging.

A

pair production

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70
Q

only at energies above 10 MeV can _______ take place

A

photodisintegration

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71
Q

when the mass density of the absorber is ______, it results in ______ Compton scatter

A

increased, increased; OR decreased, decreased (direct relationship)

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72
Q

K-shell binding energy increases w increasing ______

A

atomic #

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73
Q

what has the greatest mass density?

A

bone

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74
Q

img fog is caused by?

A

Compton scatter/interactions

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75
Q

bc of differential absorption, about ____ of the incident beam from the XR tube contributes to the finished img

A

0.5%

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76
Q

differential absorption is dependent on?

A

the kVp of exposure, atomic number (Z) of absorber, & mass density of absorber

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77
Q

attenuation is caused by?

A

absorption & scattering

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78
Q

Ba is a good contrast agent bc of it’s

A

high Z

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79
Q

the use of contrast agents increases the amount of?

A

differential absorption, Compton Scatter, photoelectric absorption

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80
Q

a neg. contrast agent is?

A

air

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81
Q

XR transmitted without interaction contribute to

A

the radiographic img

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82
Q

Compton interactions, photoelectric absorption, & transmitted XRs ALL contribute to?

A

differential absorption

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83
Q

high kVp techniques reduce

A

pt dose

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84
Q

if 5% of an incident beam is transmitted through a body part, then 95% of that beam was

A

attenuated

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85
Q

smallest quantity of any type of electromagnetic rad

A

photon

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86
Q

velocity of all electromagnetic rad?

A

3 x 10^8 m/s

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87
Q

rate of rise and fall of a sine wave is called its

A

frequency

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88
Q

a hertz (Hz) is = to

A

1 cycle per sec

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89
Q

electromagnetic wave equation?

A

c=f⋋

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90
Q

the _____ of electromagnetic rad is constant

A

velocity

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91
Q

if the wavelength of a beam of electromagnetic rad increases by a factor of 2, then its frequency must

A

decrease by 1/2

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92
Q

the intensity of rad _____ in _____ proportion to the square of the distance of the object from the source

A

decreases, inverse

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93
Q

the reduction of rad intensity due to scattering & absorption is called ______

A

attenuation

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94
Q

velocity of light?

A

c = 3 x 10^8 m/s

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95
Q

max # of e-‘s that can exist in an electron shell is calculated w?

A

2n^2

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96
Q

the shell # of an atom is called the

A

principal quantum #

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97
Q

the unit of measure of rad in the air is the

A

roentgen

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98
Q

the ______ is the unit used to describe the dose of ionizing rad received by a pt

A

rad

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99
Q

what unit is used to measure occupational dose?

A

rem

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100
Q

a measure od 10^-3 rads is a?

A

millirad

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101
Q

quantity of matter as described by its energy equivalence

A

mass

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102
Q

what has form/shape & occupies space

A

matter

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103
Q

energy of motion

A

kinetic

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104
Q

ability to do work

A

energy

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105
Q

rate of doing work

A

power

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106
Q

standard unit of mass in SI system?

A

kg

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107
Q

atoms & molecules are the fundamental building blocks of

A

matter

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108
Q

radio waves, light, & XRs are all ex’s of ________ energy

A

electromagnetic

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109
Q

removal of an e- from an atom

A

ionization

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110
Q

ionizing rad is capable of removing ________ from atoms as it passes through matter

A

e-‘s

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111
Q

biggest source of manmade ionizing rad exposure to the public

A

diagnostic XRs

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112
Q

Wilhelm Roentgen discovered XRs while experimenting w?

A

Crookes tube

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113
Q

radioactive material measured in

A

curies

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114
Q

which of the following is ionizing electromagnetic rad? (beta rays, gamma rays, radio waves, alpha rays)

A

gamma rays

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115
Q

Newton’s 2nd law is written mathematically as?

A

F=MA

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116
Q

who invented fluoroscopic machine?

A

Thomas Edison

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117
Q

term “atom” was first used by the

A

Greeks

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118
Q

smallest particle that has all the properties of an element is a(n) ______

A

atom

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119
Q

periodic table of elements was developed by _______ in the late 19th century

A

Mendeleev

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120
Q

a pos. charged nucleus surrounded by neg. charged e-‘s in well-defined orbits is the _______ model of the atom

A

Bohr

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121
Q

fundamental particles of an atom?

A

proton, e-, neutron

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122
Q

chem element is determined by the # of ____ in the atom

A

protons

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123
Q

an atom in a normal state has an electric charge of

A

zero

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124
Q

the binding energies or energy levels of e-‘s are represented by their?

A

shells

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125
Q

when an atom has the same # of protons, but diff # of neutrons, its called an

A

isotope

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126
Q

when atoms of various elements combine, they form

A

molecules

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127
Q

an atom that loses/gains 1+ e- is an ____

A

ion

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128
Q

neutral atom has the same # of ______ & e-s

A

protons

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129
Q

innermost e- shell is

A

K-shell

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130
Q

atomic # symbolized w

A

Z

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131
Q

Aluminum has a Z of 13. how many protons does it have?

A

13

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132
Q

atomic # of molybdenum is 42 and the atomic mass # is 98. how many neutrons does it have?

A

56

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133
Q

only diff btw XRs & gamma rays is

A

their origin

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134
Q

the _______ is the least penetrating form of ionizing rad

A

alpha particle

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135
Q

gamma rays are produced in the _______ of the atom

A

nucleus

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136
Q

the T required for a quantity of radioactivity to be reduced to 1/2 of its original value

A

1/2 life

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137
Q

examples of particulate rad?

A

alpha & beta particles

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138
Q

what’s common amongst all electromagnetic rad’s?

A

their velocity

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139
Q

alpha particles are compared to a ________ nucleus

A

helium

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140
Q

the force that keeps an e- in orbit is the?

A

centripetal & centrifugal force

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141
Q

87º Fahrenheit is equal to _____ Celsius

A

Tc=5/9(Tf - 32)
Tc = 5/9 (87 - 32)
Tc = 30.5ºC

142
Q

1/2 the distance from crest of a sine wave to the valley is the

A

amplitude

143
Q

in a sine wave, the distance from one valley to another valley (or crest to crest) is

A

wavelength

144
Q

of wavelengths that pass a point of observation per sec

A

frequency

145
Q

in a sine wave, the shorter it’s wavelength, the _______ its frequency

A

higher

146
Q

the energy of a photon is directly proportional to its

A

frequency

147
Q

the ___________ describes the relationship btw rad intensity and distance from the rad source

A

inverse square law

148
Q

when white light goes through a prism, it gets

A

refracted

149
Q

the study of fixed/stationary electric charge

A

electrostatics

150
Q

fundamental unit of electric charge is

A

Coulomb

151
Q

according to ________, electrostatic force is directly proportional to the product of the electrostatic charges and inversely proportional to the square of the distance btw them

A

Coulomb’s law

152
Q

what states that “when an object becomes electrified, the electric charges are uniformly distributed throughout the object or on its surface”

A

electrostatic law #3

153
Q

what states that “the electric charge of a conductor is concentrated along the sharpest curvature of its surface”?

A

electrostatic law #4

154
Q

unit of electric potential?

A

volt

155
Q

study of electric charges in motion is known as

A

electrodynamics

156
Q

silicone & germanium are examples of

A

semiconductors

157
Q

the property of some materials to exhibit no resistance below certain critical temp is illustrated as a concept known as

A

superconductivity

158
Q

any property of the circuit that opposes/hinders the flow of the current is known as

A

resistance

159
Q

what factors affect resistance?

A

material, diameter, length, & temp of conductor

160
Q

which law states that the voltage across the total circuit or any portion of the circuit is = to the current multiplied by the resistance?

A

Ohm’s law

161
Q

if the e- flows alternatively in opposite direction, it is called

A

alternating current

162
Q

______ is = to 1 ampere of current flowing through an electric potential of 1 volt

A

1 watt

163
Q

any charged particle in motion creates

A

a magnetic field

164
Q

the direction of the magnetic field is ________ to the motion of a charged particle

A

perpendicular

165
Q

the ability of a material to attract the lines of magnetic field intensity is known as

A

magnetic permeability

166
Q

degree to which various material can be magnetized is known as

A

magnetic susceptibility

167
Q

what is considered as paramagnetic

A

MRI contrast

168
Q

which transformer works under the principle of self-induction?

A

auto transformer

169
Q

transformer law formula?

A

Vs/Vp = Ns/Np

170
Q

a step up transformer has 500 coils at the primary & 7000 coils at the secondary. If 220 volt is supplied at the primary, how much voltage will be produced at the secondary?

A

3100v

171
Q

the transformer loss due to the resistance of the wire is known as

A

Copper loss

172
Q

a transformer has 600 coils on its primary side and 30 coils on its secondary side. what s the voltage on the secondary side when the primary side is 220 V?

A

11V

173
Q

an electric current can be induced in a coil of wire if it is places near a(n)

A

electromagnet

174
Q

the reduction of rad intensity due to scattering & absorption is called

A

attenuation

175
Q

gamma rays are produced in the _____ of the atom

A

nucleus

176
Q

photons w the highest frequencies have the

A

shortest wavelengths

177
Q

like charges _____ and unlike charges _______

A

repel, attract

178
Q

electrostatic force is _____ proportional to the distance btw charges and _______ proportional to the product of the charges

A

inversely, directly

179
Q

charges on an electrified object are distributed

A

evenly throughout the object

180
Q

on the surface of an electrified object the charges concentrate

A

on the sharpest curvatures

181
Q

_______ is a source of a direct current

A

a battery

182
Q

an alternating current (AC) is represented by a __________ line

A

sinusoidal

183
Q

________ uses direct current? (hair dryer, toaster, microwave, flashlight)

A

flashlight

184
Q

Ohm’s law? (formula)

A

I = V/R

185
Q

SI unit of magnetic field strength

A

tesla

186
Q

what type of material can be made magnetic when placed in an external magnetic field?

A

ferromagnetic

187
Q

if 3 resistors of 3 ohms, 4 ohms, & 6 ohms ea are connected in a series what will be the total resistance?

A 
Rt = R1 + R2 + R3
Rt = 3+4+6
Rt = 13 Ohm's
188
Q

if the current flowing through a circuit is 2A and the potential difference is 110V, what will be its resistance?

A 
V = IR  -->   R = V/I
R = 110V/2A
R = 55 Ohm's
189
Q

if a pt receives 100 mR standing at a distance of 72” from an XR source, what will be the rad dose to the pt if the pt is standing at a distance of 40”?

A

I1/I2 = D2^2/D1^2
100 mR/!2 = 40^2/72^2
1600I2 = 518400
I2 = 324 mR

190
Q

what determines quality of XR beam?

A

kVp

191
Q

what determines quantity of XR beam?

A

mA & exposure T

192
Q

heating a coil of wire to produce e-‘s is known as

A

thermionic emission

193
Q

the flow of e- from filament to anode is known as

A

tube current

194
Q

the alternating current can be converted to direct current w the use of a

A

rectifier

195
Q

if a tech uses 70 kVp, 400 mA, & 1/10 s exposure T for a KUB, what will be the mAs produced?

A

40

196
Q

what is located btw the auto-transformer & the step up transformer?

A

kVp meter

197
Q

what transformer works under the principle of self-induction

A

auto transformer

198
Q

what is located btw the step up transformer & XR tube?

A

rectifier

199
Q

XR of L-spine needs 40 mAs. the tech wants to use the 200 mA station. what should be the exposure T?

A

0.20 s

200
Q

a tech wants to use 110 kVp & 80 mAs for a L-spine. the tech wants to use 200 millisec exposure T. what mA station should be chosen?

A

400 mA

201
Q

what is located at the secondary side of the step up transformer?

A

mA meter

202
Q

two basic types of induction are _____ induction & ______ induction

A

self, mutual

203
Q

a transformer converts

A

electrical potential to higher/lower intensity

204
Q

the current to a transformer must be supplied by a(n)

A

AC source

205
Q

variations in power distribution to the XR machine are corrected by the

A

line voltage compensator

206
Q

the 1st component to receive power in the XR circuit is the

A

autotransformer

207
Q

the ______ circuit provides e-‘s for the XR tube current

A

filament

208
Q

thermionic emission at the filament determines the _______ across the XR tube during an exposure

A

milliamperage

209
Q

a step-down transformer is located in the ______ circuit

A

filament

210
Q

the most accurate type of timer is the ______ timer

A

electronic

211
Q

the AEC terminates the exposure when

A

sufficient rad reaches the IR

212
Q

the ionization chamber is located

A

btw the pt & the IR

213
Q

the f(x) of the photodiode is

A

to convert light to electric signal

214
Q

the principal material used in the formulation of a solid state diode is

A

silicon

215
Q

process by which alternating current is converted into pulsating direct current is termed

A

rectification

216
Q

type of unit most likely to possess the smallest voltage ripple is a

A

high frequency unit (1%)

217
Q

1 3-phase, 12-pulse wave formula has _____ ripple

A

4%

218
Q

a high frequency wave form has ____ ripple

A

1%

219
Q

a 3-phase, 6-pulse wave form has ____ ripple

A

14%

220
Q

a single-phase wave form has ______ ripple

A

100%

221
Q

a 3-phase, 6-pulse unit has an effective kV of about _____ of the peak kVp

A

86%

222
Q

during capacitor discharge, the voltage falls at a rate of

A

1 kV/mAs

223
Q

the e- cloud around the filament is known as

A

space charge

224
Q

tungsten is the material of choice for the target bc?

A

high Z, high thermal conductivity, high melting point

225
Q

according to line focus principle, the effective focal spot size is always ________ than the actual focal spot size

A

smaller

226
Q

smaller the anode angle the ______ heel effect

A

larger

227
Q

anode angle and effective focal spot size are

A

directly proportional

228
Q

anode angle and heel effect are

A

indirectly proportional

229
Q

to take advantage of the heel effect, the thicker body part must be positioned under the

A

cathode

230
Q

the effective focal spot size is larger on the ______ side

A

cathode

231
Q

the most frequent cause of abrupt tube failure is

A

e- arcing from the (open) filament

232
Q

which kVp selection would result in the most scattered XRs in the img-forming beam? (90, 75, 60, 50)

A

90 kVp

233
Q

decreasing kVp will increase

A

pt dose

234
Q

contrast res is improved by? (3)

A

tight collimation, lowering kVp, pt compression

235
Q

use of a compression device will increase _____

A

contrast

236
Q

the use of ______ improves contrast & reduces pt dose

A

collimation

237
Q

how can you improve img contrast w a heavy pt without increasing pt dose?

A

use tight collimation

238
Q

img contrast improves when more of ______ rad is removed

A

scattered

239
Q

a grid is constructed w _______ strips & _______ interspace material

A

radiopaque, radiolucent

240
Q

a radiograph w a long scale of contrast will also have _____ latitude & ______ contrast

A

wide, low

241
Q

grids are designed to remove scattered XRs before they reach

A

the IR

242
Q

what is the grid ratio of a grid w 3-mm height, 0.025-mm thick pb grid strips, and 0.3-mm thick interspace material?

A

10:1

243
Q

foreshortening is caused by a(n)

A

angled body part when the beam is perp to the IR

244
Q

optical density (OD) is directly controlled by changing the _____

A

mAs

245
Q

pt thickness affects img quality by affecting? (3)

A

magnification, rad contrast, focal spot blur

246
Q

best way to min. magnification is to use a

A

long SID & small OID

247
Q

subject contrast is affected by

A

pt thickness

248
Q

3 primary factors influencing the intensity of scatter in the img-forming beam are

A

kVp, field size, & pt thickness

249
Q

scatter rad increases as _______ increases

A

field size

250
Q

the most commonly used beam restricting device is the ____________

A

variable collimator

251
Q

the pos. beam limiting device (PBL) ensures that the XR beam is collimated to

A

the IR size

252
Q

________ is the degree of difference in optical density (OD) btw areas of an img

A

contrast

253
Q

amount of scatter absorption in a grid depends on? (3)

A

angle of scattered photon, height of the grid strips, & width of the interspace material

254
Q

formula for grid ratio?

A

h/D

255
Q

purpose of a grid is to achieve

A

improved img contrast

256
Q

the interspace material in grids is made of ________

A

either aluminum or plastic (fiber)

257
Q

grids generally have a frequency of _______ lines per in

A

60-110

258
Q

the most critical consideration when using a crossed grid is ____________

A

alignment (positioning latitude)

259
Q

how could contrast be improved on a bedside radiograph of a very large pt? (3)

A

use grid, lower kVp, use tight collimation

260
Q

spatial res improves w decreased? (3)

A

screen/motion/geometric blur

261
Q

radiographic ___________ is random fluctuation in the optical density (OD) of a radiograph

A

noise

262
Q

the slope of the _______ portion of the characteristic curve shows the film contrast.

A

straight line

263
Q

if 10% of the view box light is transmitted through an area of film, what is the optical density in that area?

A

1

264
Q

a film w a characteristic curve showing a high slope would be useful when ________ is needed

A

high contrast

265
Q

the 3 primary geometric factors affecting img quality are?

A

magnification, distortion, & focal spot blur

266
Q

distortion can be reduced by

A

placing the object plane II to the IR

267
Q

focal spot blur can be reduced by using a

A

small focal spot

268
Q

XR img quality is improved when the ______ is increased.

A

SID

269
Q

_______ is defined as the ability to img 2 separate objects & visually detect one from the other

A

resolution

270
Q

higher speed img receptors generally produce img’s w

A

increased noise

271
Q

an img receptor w ________ can be used over a greater range of exposures

A

wide latitude

272
Q

formula for optical density (OD)

A

OD = log10 (Io/It)

273
Q

densities above 2.5 on a film are represented in the ________ portion of the characteristic curve

A

shoulder

274
Q

sharpness of detail can be improved by increasing ______

A

SID

275
Q

lowering kVp _____ pt dose & _______ img contrast

A

increases, increases

276
Q

modern rad film base is made of ________

A

polyester

277
Q

how thick is radiographic film base?

A

150-300 µm

278
Q

crystals in film emulsion consist of ______ & ______

A

silver bromide, silver iodide

279
Q

latent img formation occurs during film ________

A

exposure

280
Q

a contaminant in the silver halide crystal creates the

A

sensitivity speck

281
Q

the latent img can be seen

A

only after development

282
Q

the latent img is made up of ______ atoms

A

silver

283
Q

high contrast film contains ______ silver halide crystals (SHC) of _____ size

A

smaller, uniform

284
Q

film is made w double emulsion to enhance film _______

A

speed

285
Q

spectral matching is not a consideration when using

A

direct exposure film

286
Q

storing film in very low humidity conditions can cause

A

static artifact

287
Q

film should be stored at a temp of ______ or below & w humidity no higher than _______

A

68ºF; 60%

288
Q

the rollers in the automatic processor are part of the _______ system

A

transport

289
Q

replenishment of fixer & developer are controlled by the

A

microswitch

290
Q

the undeveloped silver halide is removed from the emulsion during

A

fixing

291
Q

name a rare earth phosphor?

A

lanthanum oxybromide

292
Q

an increase in _____ will increase both beam quality & beam quantity

A

kVp

293
Q

what are the 4 primary exposure factors?

A

kVp, mA, time, & SID

294
Q

changes in kVp affect? (3)

A

OD, img contrast, img noise

295
Q

an increase in mAs causes (an) _______ in beam quality & (an) ______ in beam quantity.

A

no change, increase

296
Q

there is a direct relationship btw the quantity of XRs & the _____

A

milliamperage

297
Q

if mAs are increased from 20 mAs to 40 mAs, the pt dose dose will

A

be doubled

298
Q

beam penetrability is increased if ______ is increased

A

kVp

299
Q

beam quality is improved when the _______ is increased, but ______ has no effect on beam quality.

A

kilovoltage, milliamperage

300
Q

both beam quality & beam quantity are increased by

A

increasing kVp & changing from a single-phase to 3-phase voltage

301
Q

to reduce img blur, what should tech do?

A

use shortest exposure T

302
Q

when looking at exposure techniques, how can you tell which one gives the highest pt dose?

A

the one with the highest mAs

303
Q

added filtration has the effect of _____ the beam quality & ______ pt dose

A

increasing, reducing

304
Q

when all other exposure factors remain the same, changes in focal spot size result in ____ in beam quality and _____ in beam quantity

A

no change, no change

305
Q

film can turn brown during storage due to a retention of ___________

A

ammonium thiosulfate

306
Q

filtration is added to XR machines during manufacturing so that the required total of ___ mm Al equivalent filtration is achieved.

A

2.5

307
Q

what kind of film is used in mammography?

A

single emulsion film

308
Q

an exposure w an off-level grid will show grid cutoff

A

across the img

309
Q

what is the formula for Bucky factor?

A

pt dose w grid/pt dose without grid

310
Q

grid ratio is the _____ of the grid strips divided by the _____ of the interspace material

A

height, width

311
Q

tree artifacts are caused by

A

friction

312
Q

a high contrast XR has

A

short scale contrast

313
Q

if a tech did a knee w a non-grid exposure using 10 mAs & wanted to use an 8:1 grid, what mAs should be used to produce a XR w the same density?

A

40

314
Q

if a tech did a lat C-spine using a 12:1 grid & 10 mAs. if the tech is to be repeated using no grid, what should be the new mAs to produce a XR w the same density?

A

2

315
Q

if a tech uses 24 mAs w a 16:1 grid, how much mAs should he/she use w a 6:1 grid?

A

12

316
Q

which of the following technique chart causes less rad dose to the pt?

A

fixed kVp chart

317
Q

the mAs values must be changed ___% to produce a perceptible change in OD.

A

30%

318
Q

low humidity in the darkroom can cause

A

tree static

319
Q

the undeveloped silver is removed from the emulsion during ______

A

fixing

320
Q

Grid frequency

A

of pb strips per unit length (in/cm)

321
Q

Types of grids used in rad

A

Linear & crossed

322
Q

Most common grid type used

A

Linear

323
Q

Which grid type gives more contrast?

A

Crossed

324
Q

High or low ratio grid give more pos latitude?

A

Low ratio grid

325
Q

Main disadvantage of II grid

A

Less contrast, removes less scatter

326
Q

Main disadvantage of crossed grid?

A

Less pos latitude, absorbs more primary beam (May need to increase mAs to replace beam, which is more pt dose)

327
Q

3 factors that control/affect detail

A

Screen/geometric/motion blur

328
Q

As speed of IR increases, rad noise ______ & spatial res ______

A

Increases, decreases

329
Q

Avg grid frequency used in rad depts?

A

25-45 lines/cm, 60-110 lines/in

330
Q

4 most important characteristics of img quality?

A

Spatial res., contrast res., noise & artifacts

331
Q

Primary control of contrast?

A

kVp

332
Q

Primary control of OD

A

mAs

333
Q

3 geometric factors

A

Magnification, distortion, focal spot blur

334
Q

What controls detail?

A

Focal spot size

335
Q

Detail is influenced by what

A

SID/OID & motion (screen/geometric/motion blur)

336
Q

When are grid required?

A

Anatomical part 10+ cm or more than 60 kVp is needed

337
Q

High/low grid ratio gives better contrast?

A

High (absorbs more scatter)

338
Q

Grid is made w pb strips that are 16 mm long & separated by an interspacing material 2 mm wide. What’s grid ratio?

A

8:1

339
Q

How do you calculate the distance until grid cutoff?

A

D = SID/grid ratio

340
Q

What happens to img contrast when grids are used?

A

Img contrast approx doubles

341
Q

Random fluctuation in the OD of the img

A

Noise

342
Q

Ability to img small objects that have high subject contrast

A

Spatial res

343
Q

Factors that affect the visibility of detail

A

Img contrast & OD

344
Q

Random nature by which XRs interacts w IR

A

Quantum mottle

345
Q

What increases quantum mottle? How does it make img appear?

A

If produced w fewer XRs; grainy

346
Q

How do you min quantum mottle (3)

A

High mAs, low kVp, slow IR

347
Q

Ability to img 2 separate objects and visually distinguish btw the 2

A

Contrast res

348
Q

Study of the relationship btw exposure intensity & blackness (density) on img

A

Sensitometry

349
Q

Radiographic contrast is the product of ________ & ________

A

IR contrast & subject contrast

350
Q

How do you calculate the slope of a characteristic curve

A

Calculate the avg gradient

351
Q

Factors that affect magnification (4)

A

Size, shape, SID & OID

Freshman Exit Exam (6 decks)

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