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Shani Radsci 226 > Test 1 > Flashcards

Test 1 Flashcards

1
Q

The x-ray beam can be divided into what two portions?

A

Primary beam and remnant beam

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2
Q

Radiation emitted by the x-ray tube that has not yet passed through the patient

A

primary beam

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3
Q

radiation that emerges from the body tissues behind the patient or object and strikes the IR

A

Remnant

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4
Q

What part of the beam is the image-forming radiation

A

Remnant

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5
Q

radiation that moves in random directions

A

scatter radiation

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6
Q

Primary x-rays diverge _______, that is they fan out evenly as they travel toward the object being radiographed

A

isotropically

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7
Q

what part of the x-ray beam is not divergent

A

central ray

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8
Q

The precise center of the x-ray beam which lies perpendicular to the axis of the x-ray tube above

A

central ray

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9
Q

SID

A

source to image distance

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10
Q

How is SOD measured

A

From focal spot to the upper surface or entrance surface of the body or object

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11
Q

OID

A

Object to image receptor plate

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12
Q

How is SID measured

A

From the focal spot to the image receptor

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13
Q

SOD

A

Source to object distance

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14
Q

what are the 6 radiographic variables

A
  1. technical
  2. geometrical
  3. patient status
  4. Image receptor systems
  5. image processing
  6. viewing conditions
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15
Q

what variable includes all electrical factors such as the generator kVp and mA

A

technical variables

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16
Q

what variable includes carious distances (SID, SOD, OID), the angles and alignment of the x-ray beam, part of interest, and image receptor.

A

Geometrical variables

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17
Q

What variable includes general condition of the patient and the diseases or interventional changes that further alter the quality of the final image.

A

patient status

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18
Q

what variable includes all devices which alter the condition of the remnant beam after it has passed through the patients body, such as grids, tabletop and cassette materials

A

image receptor systems

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19
Q

What variable includes chemical processors and computer software programs

A

image processing

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20
Q

what variable includes lighting, view boxes, and computer screens

A

viewing conditions

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21
Q

What 3 types of interactions do x-rays have with a patient

A
  1. photoelectric
  2. Compton
  3. cohert
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22
Q

the interaction where the x-ray beams are completely absorbed by the patient tissue

A

photoelectric effect

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23
Q

the photoelectric effect is primarily responsible for the production of _____ contrast

A

subject

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24
Q

When atoms lose their electrons, they are considered _____

A

ionized

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25
Q

The photoelectric effect only occurs when the energy of the incoming x-ray photon is _____ ______ than the binding energy for the inner shell electron.

A

slightly higher

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26
Q

What effect takes place when only some of the x-rays are absorbed, and the left over is re-emitted as a new x-ray photon which scatters in random directions.

A

Compton

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27
Q

What are two other names for Compton effect

A
  1. modified scattering

2. incoherent scattering

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28
Q

The scatter radiation caused by the Compton effect are considered ____ photons

A

new

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29
Q

the rejected electron in a Compton effect is known as a

A

recoil electron

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30
Q

True or false: scattered x-rays can be emitted backwards, directly toward the incident beam

A

true

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31
Q

Radiation emitted from the patient that comes back toward the incident beam

A

backscatter

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32
Q

Scattered radiation carries the _____ from the original x-ray

A

energy

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33
Q

what does scatter radiation do to a radiograph, and what does it destroy

A

degrades the image, destroys subject contrast

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34
Q

what percent of scatter radiation is from the Compton Effect

A

97%

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35
Q

what percent of scatter radiation comes from the Coherent Effect

A

3%

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36
Q

When the incoming x-rays is less than the binding energy of the electron what effect will take place?

A

Coherent Scattering

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37
Q

are the atoms ionized in coherent effect

A

no

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38
Q

what two interactions can occur during the coherent effect

A

Rayleigh, and Thompson

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39
Q

what interaction is taking place when an entire atom is raised to a state of excitation for a brief moment

A

Rayleigh

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40
Q

The partial absorption of the x-ray beam

A

Attenuation

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41
Q

What three factors affect attenuation in a patient

A
  1. thickness
  2. density
  3. atomic number
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42
Q

The subtle differences in attenuation between all the carious tissues and parts of the human body

A

differential absorption

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43
Q

All of the different attenuation have a collective effects upon the remnant x-ray beam called _________ _______

A

subject contrast

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44
Q

The greater the x-ray attenuation of a tissue with relation to adjacent tissue, the _____ the subject contrast

A

greater

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45
Q

_____ _____ in the primary beam causes magnification and distortion of structures within the image

A

isotropic divergence

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46
Q

what effect is considered the “all-or-nothing” absorption of x-rays

A

photoelectric effect

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47
Q

_____ is responsible for subject contrast in the _______ image. and scattered radiation tends to destroy subject contrast in the ____ ______

A

photoelectric, radiographic, remnant beam

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48
Q

Compton effect occurs when the x-rays are much ____ than the energy of the electrons

A

higher

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49
Q

The latent image or signal is carried to the receptor by the ____ x-ray beam

A

remnant

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50
Q

The only nondiverging ray in the primary x-ray beam is the

A

Central ray

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51
Q

Positioning of the patient actually falls under what category of radiographic variables

A

geometrical

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52
Q

Even after the radiographic image is processed and stored, what other type of variables still can alter its quality

A

viewing conditions

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53
Q

microscopic white spots are produced in the image by which interaction

A

photoelectric

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54
Q

The ideal conditions for the photoelectric effect to take place are created when the average kV of incident x-ray photon is _____ _____ than the inner shell binding energies of tissue atoms

A

slightly higher

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55
Q

which of the two major interactions can occur in a series within the patient from a single x-ray photon

A

compton

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56
Q

in terms of the quantity of radiation scattered in each direction from the CR, where is the worst place for a radiographer to be standing

A

At a reverse oblique angle from the direction of the CR

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57
Q

within the remnant x-ray beam, scatter radiation forms a type of image ____ which is always destructive

A

noise

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58
Q

Thompson and Rayleigh scatter photons have the same ____ but a different ______ from the original x-ray photon

A

energy, direction

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59
Q

why doesn’t characteristic radiation produced withing the patient affect the image signal at the receptor plate

A

It has too low of energy to escape the patients baby

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60
Q

adjust radiographic technique by a factor of 2 for every ____ change in body part thickness

A

4cm

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61
Q

what other two aspects of body tissues, besides thickness affect x-ray attenuation

A

density, atomic number

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62
Q

when x-ray beam penetration is matched properly to the differential absorption of the tissues, every radiographic image detail should be depicted as a ______

A

shade of grey

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63
Q

______ of x-ray beams in tissueshelps create subject contrast

A

attenuation

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64
Q

the ratio of x-ray attenuation between two adjacent tissues

A

subject contrast

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65
Q

For ____ tissues x-ray attenuation increases

A

thicker

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66
Q

x-ray attenuation ______ in direct proportion to the physical density of tissue

A

increases

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67
Q

The subject contrast of the image is carried by the ____ x-ray beam and is reduced by _______ radiation

A

remnant, scatter

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68
Q

high levels of kVp cause less ______ effects to occur and more ______ effect

A

photoelectric, compton

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69
Q

______ densities are lost when ____ is too high

A

light, kVp

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70
Q

the greatest subject contrast is achieved when high atomic number tissue is combined with ___ kVp

A

low

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71
Q

Define subject contrast as it pertains to the remnant x-ray beam reaching the image receptor

A

Subject contrast is the difference in x-ray intensity between different portions of the remnant beam, (which constitute a latent image or signal).

72
Q

of the three types of x-ray interactions that occur within the patient, which ones contribute to subject contrast in the image carried by the remnant beam

A

all three of them

73
Q

of the three aspects of a tissue, which one has a proportional relationship to x-ray attenuation

A

density

74
Q

of the three aspects of a tissue, which one must be altered most dramatically to cause a substantive change in subject contrast

A

density

75
Q

atoms with high atomic number are more likely to absorb x-rays because of their high ____ density

A

electron

76
Q

scatter radiation reduces subject contrast because it adds an _____ amount of exposure to all local area of the image

A

equal

77
Q

As kVp is increased, which way and by how much does the occurrence of the Compton effect change

A

Occurrence of Compton interactions decreases, but only slightly

78
Q

ultimately, the subject contract in the image carried by the remnant beam is dependent not upon the raw number of the different x-ray interactions, but on their _____ in contributing to the image

A

Proportions

79
Q

Changes in the energy of the x-ray beam is controlled by?

A

kVp

80
Q

as kVp is increased _____ penetration is achieved

A

more

81
Q

Is Compton interaction affected by kVp

A

slightly

82
Q

What interaction become more prevalent at higher kVp

A

Compton

83
Q

Penetrating x-rays produce the ____ and ____ areas in the image

A

black, darker

84
Q

what produces the whites and lighter areas in the image

A

photoelectric interactions

85
Q

what produces the black and darker areas in the image

A

penetrating x-rays

86
Q

what lays down a blanket of fog at the image receptor

A

Compton scatter

87
Q

when higher contrast is wanted _____ kVp is used

A

lower

88
Q

What 4 components of an image may affect its visibility

A

brightness, intensity, contrast, and noise

89
Q

Most radiographic images are inherently _____ images

A

negative

90
Q

the divided ratio between the brightness of two adjacent details

A

radiographic contrast

91
Q

the range of brightnesses

A

gray scale

92
Q

what is considered to be the opposite to contrast

A

gray scale

93
Q

what should be adjusted first contrast or brightness

A

contrast

94
Q

anything that obscures the visibility of an image

A

noise

95
Q

what are the 5 noise factors

A

material, quantum mottle, off-focus radiation, electronic and algorithmic deviations, exposure artifacts

96
Q

what are the three visibility components of any image

A

brightness (density), Contrast (gray scale), noise

97
Q

the best amount of brightness or contrast to have in any image is an _____ amount

A

intermediate

98
Q

what is the radiographic opposite of image contrast

A

gray scale

99
Q

List three examples of different types of noise in an image

A

Any three of the following: Quantum mottle, receptor mottle, fog, exposure artifacts, patient artifacts, receptor artifacts, processing artifacts, electronic noise (snow), etc.

100
Q

To ensure that every image detail within the anatomy of interest is depicted as a shade of grey, producing sufficient gray scale in the image, x-ray beam ____ must be sufficient

A

penetration

101
Q

noise is broadly defined as anything that obscures the ____ of an image

A

visibility

102
Q

a short gray scale indicates ____ contrast

A

high

103
Q

the use of grids to reduce scatter radiation is an example of changing what portion of the SNR

A

noise

104
Q

increasing the kVp at the console is an example of changing what portion of the SNR

A

signal

105
Q

in the digital age, ____ has exceeded scatter radiation as the most common form of noise appearing in the final displayed image

A

mottle

106
Q

measures the rate of electricity flowing through the x-ray tube, and controls the rate of x-rays emitted from it

A

mA

107
Q

when the filament is heated to the point that a cloud of electrons is formed

A

thermionic emissions

108
Q

the product of exposure time and mA

A

mAs

109
Q

what controls the total amount of x-rays delivered from the x-ray tube during the exposure

A

mAs

110
Q

mA and exposure time are _____ related to each other

A

inversely

111
Q

what is the preferred controlling factor for total exposure

A

mAs

112
Q

a ____ focal spot should be used to maximize image sharpness

A

small

113
Q

which can result from insufficient mAs

A

quantum mottle

114
Q

True or false: the mAs does not affect the average energy or penetration characteristics of the x-ray beam

A

true

115
Q

Is mAs considered a factor in controlling subject contrast

A

no

116
Q

What exposure factor would you change if the patient keeps moving

A

shorter exposure time

117
Q

strictly speaking, mA is a unit which measures

A

The flow rate of electricity

118
Q

give two reasons why mAs should be considered as the prime factor in controlling x-ray exposure

A

1) It is directly proportional to exposure

2) It affects only the exposure level

119
Q

The mAs does not alter subject contrast in the remnant beam because it does not change the ____ or different types of interactions occurring within the patient

A

Proportion (percentage)

120
Q

for what type of radiographic procedure would a low mA and long exposure time be needed

A

Tomography including autotomography (breathing or wagging-jaw techniques)

121
Q

insufficient mAs can cause the appearance of _____in the image

A

quantum mottle

122
Q

generally short exposure times are desirable to minimize the probability of ____

A

motion

123
Q

x-rays are _____ (not all the same)

A

heterogeneous

124
Q

x-rays give off ____ when they go through matter

A

heat

125
Q

short gray scale = ____ contrast

A

high

126
Q

quantity of x-rays

A

mAs

127
Q

quality of x-rays

A

kVp

128
Q

the amount of radiation that strikes the image receptor

A

receptor exposure

129
Q

You use 10 mA and 0.5s for your first exposure. For the 2nd exposure you want to use 0.1s. What would your mA be?

A

10mA(.5) = 5mAs
xmA (.1) = 5mAs
XmA = 5/.1 = 50 mA

130
Q

what is the purpose of the 15% rule

A

to reduce patient dose while keeping the final image factors the same

131
Q

what is quantum mottle caused from

A

not having enough x-rays (low mAs)

132
Q

What charge does the cathode have

A

negative

133
Q

what charge does the anode have

A

positive

134
Q

what 3 things do you need to have to make an x-ray

A

a source of e-, a way to accelerate e- and a way to decelerate e-

135
Q

what are filaments made out of

A

Tungsten

136
Q

What is the purpose of the focusing cup and what charge does it have on it.

A

the focusing has a negative charge. The negative charges of the e- repel each other, they then repel away from the focusing cup which refocuses them

137
Q

what are the three main function of the anode

A

electrical conductor, thermal dissipater, target

138
Q

Calculating cool down

If you did an exposure with the factors of 90kVp, 200 mA, and .25s and you took three exposures how do you calculate the heat

A

1.4(kVp)(mA)(s)(# of exposures)

1.4(90)(200)(.25)(3) = 18900
You would then use the graph to find the minutes and subtract the minutes on the graph from the largest amount of minutes

139
Q

kVp increase both the ______ and the _____ of the x-rays

A

quantity, energy

140
Q

kVp should be set so that there is _____ penetration through all tissue

A

partial

141
Q

No amount of ____ can ever compensate for insufficient kVp

A

mAs

142
Q

subject contrast in the remnant x-ray beam depends on the level of _____

A

kVp

143
Q

for the 15% Rule of thumb when you increase your kVp by 15%, what will happen to mAs

A

it will be halved

144
Q

kVp has no direct impact on what three geometrical aspects of the image

A

sharpness, magnification and distortion

145
Q

The most important function of kVp is to produce sufficient ____ of the x-ray beam

A

penetration

146
Q

what electronic device is controlled by the kVp setting at the x-ray machine console

A

The autotransformer

147
Q

why is higher kVp, rather than higher mAs, particullarly recommended when changing from the AP projection of the lumbar spine to the lateral L5-S1 spot view

A

There is a greater bone-to-soft tissue ratio in the lateral pelvis

148
Q

does scatter radiation cause blurring of the image

A

no

149
Q

Suppose you reduce the kVp by 3 steps of 15 percent each. Even though you doubled the mAs three times, the radiograph may still turn out underexposed because of

A

Insufficient penetration through the anatomy

150
Q

radiation that is produced when electrons are deflected to other pars of the x-ray tube outside the focal spot

A

off-focus

151
Q

what is responsible for ghost images at the edges of a collimated field

A

off-focus radiation

152
Q

true or false: off-focus and scatter radiation are the same thing

A

false

153
Q

to allow for inaccuracies in field light alignment, always allow ___ cm of field light beyond each edge of the anatomy of interest

A

1cm

154
Q

excessive field size reduces ______ ______ in the remnant beam

A

subject contrast

155
Q

what are the two purposes of reducing field size

A

1) Improve subject contrast in the remnant beam signal, 2) reduce patient dose

156
Q

how does collimation affect the concentration or intensity of the primary beam

A

It has no effect on it

157
Q

why is a secondary set of shutters or second aperture in a collimating device desirable

A

To absorb off-focus radiation

158
Q

where is off-focus radiation produced

A

In the x-ray tube, but outside the focal spot

159
Q

what does PBL stand for

A

“Positive-beam limitation”

160
Q

it is acceptable to override an automatic collimator in order to

A

Collimate the field size smaller than the image receptor plate size

161
Q

if anatomy of interest is clipped from a view due to overzealous collimation, how much is patient exposure increased for that view upon repeating it

A

100% or double

162
Q

the anode disc is spun at high speeds to do what

A

disperse the heat

163
Q

why must an x-ray tube be vacuumed of all gas

A

Air molecules impeded some of the projectile electrons from reaching the anode.

164
Q

what is the approximate efficiency of x-ray production by an x-ray tube

A

0.5%

165
Q

what type of x-ray tube uses a wire mesh to hold back space charge

A

A grid-controlled tube

166
Q

name 3 things that happen during bucky radiography when the rotor switch is depressed

A

1) The filament is brought up to full temperature, 2) the rotor spines the anode disc,3) the bucky grid mechanism is engaged

167
Q

name the process that provides a source of free electrons in the x-ray tube

A

Thermionic emission

168
Q

what is the focusing cup usually made of

A

Molybdenum or nickel

169
Q

what element is added to the tungsten filament to extend its life

A

Thorium

170
Q

what element is added to the tungsten focal track to help balance the spin of the anode disc

A

Rhenium

171
Q

The copper anode cylinder in the tube and the stator windings outside the tube, together form a

A

Induction motor

172
Q

why are high mA stations not accessible when the small focal spot is engaged

A

Focusing a large amount of electrons on a very small focal spot would overheat the
anode focal track.

173
Q

as an x-ray tube ages, the effective mA produced at the filament ____

A

increases

174
Q

what is the cause of pits or melts on the anode surface

A

Failure of the rotor motor or ball bearings to spin the anode

175
Q

why does focal spot blooming occur at high mA stations

A

An increased number of electrons in the space charge cloud results in them repelling each other farther away.

Shani Radsci 226 (2 decks)

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