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arrt prep > Imaging equipment: Image production terms > Flashcards

Imaging equipment: Image production terms Flashcards

1
Q

what are the 3 parts of an x ray circuit

A
  1. primary circuit
  2. secondary circuit
  3. filament circuit
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2
Q

what is the primary circuits job?

A
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3
Q

what is on the primary circuit side?

A
  1. Circuit breaker
  2. Autotransformer
  3. Kvp Meter
  4. Primary side of step up transfer
  5. Exposure timer
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4
Q

what does the circuit breaker do?

A

breaks the circuit, incase the x-ray machine drives too much power

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5
Q

what does the autotransformer do?

A

changes the kvp to certain settings. Kvp selection
- it is self induction
-single coil of wire
-works off of Alternating current

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6
Q

what does the exposure timer do?

A

controls how long the exposure stays on

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7
Q

what does the primary side of the step-up transformer do?

A

steps up the voltage from volts to kilo volts.
-uses mutual induction
-2 coils of wire

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8
Q

what components are on the secondary side of the circuit?

A
  1. Rectifier
  2. X-ray tube
  3. Secondary side of step up transformers
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9
Q

what does the rectifier do

A

converts alternating current into direct current
think * AC DC

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10
Q

What does the x-ray tube do?

A

converts electrons into x-rays

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11
Q

secondary side of step-up transformers

A

converts volts to kilovolts

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12
Q

what components make up the filament circuit

A
  1. Rehostat
  2. step down transformer
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13
Q

what does a rehostat do?

A

a variable resister that is connected to the mA selector controls the heat in the filament.
-selects the mA
-“turn up the heat” think of a thermostat (when you chose the mA, correlate that with thermoinioc emission)
-also called variable resistor, and mA selector**

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14
Q

what does the step down transformer do?

A

Voltage is being decreased, then the mA increases.
Has 2 jobs: decreases voltage and increases amperage

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15
Q

single phase

A

100% ripple is the worst

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16
Q

3-phase, 6 pulse

A

14%, old equipment = bad

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17
Q

3-phase, 12 pulse

A

4 %, not as bad but still not the best

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18
Q

High frequency

A

1 %= best! new equipment

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19
Q

more ripple = higher % which is

A

bad!!!!

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20
Q

secondary circuit electricity is in?

A

kilo volts

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21
Q

what is the filament circuits job?

A

modifies the incoming- line power to produce the thermionic emission from the filament wire of the x-ray tube by a sequence of devices

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22
Q

what does the line voltage comp senator do?

A

measures the incoming line voltage

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23
Q

what is the incoming voltage coming into the circuit?

A

220 volts
-alternating current

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24
Q

which transformer comes first in the circuit?

A

autotransformer

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25
Q

the autotransformer works on what type of induction?

A

self induction

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26
Q

the step up and step down transformer work on what type of induction?

A

mutal induction

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27
Q

what is the difference between direct and alternating current?

A

direct= electrons only flow in one direction
alternating= electrons change directions

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28
Q

x-ray tube uses what type of current?

A

direct current due to anode to cathode

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29
Q

transformers can only function using what type of current?

A

alternating current

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30
Q

Ohm’s law

A

V = Voltage
I = Amperes
R= Resistance

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31
Q

series circuit

A

all the resisators connect in a continuous line

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32
Q

parallel circuit

A

current can flow beyond one continuous line and is made up of multiple sections, meaning the circuit can still work if there is a break

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33
Q

what is the focusing cup made out of?

A

Nickle, or molybdenum

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34
Q

what is the anode target made out of?

A

Tungsten- rehiuem

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35
Q

what spins the anode?

A

the rotor

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36
Q

what is the anode heel effect?

A

-Anode heel effect refers to the lower field
intensity towards the anode in comparison to
the cathode due to lower x-ray emissions from
the target material at angles perpendicular to the
electron beam.
-The anode surface is not flat, it is at an angle.
-“Fat Cat”
-Put the thicker part under the “cat”

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37
Q

why is the anode side weaker?

A

because the anode is at an angle
-whereas the cathode doesn’t have anything in it’s way

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38
Q

decrease anode angle

A

-anode angle is smaller
-it increases the heel effect!!!

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39
Q

what effects the anode heel effect?

A
  1. Degree of anode angle
    a. Decrease anode angle (steeper) = increase in anode heel effect
  2. SID
    a. Decrease in SID = increase anode heel effect (Not as present at 72”). Would increase at a shorter SID
  3. Field Size
    a. Increase field size = increase in anode heel effect.
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40
Q

mAs repciprocity law

A

mA and time are inversely proportional. they go in the opposite directiosn

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41
Q

FOV

A

the size of your light field is the field of view

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42
Q

increasing FOV =

A

decrease collimation = larger light field

43
Q

positive beam limitation

A

light field is limited to the size of the IF place in the bucky tray

44
Q

patient size in collimation 

A

-increase in patient size =how absorption of the beam into the tissue
-less photons will reach the IR =less receptor exposure 

45
Q

decrease collimation = increase field of view which is

A

a larger light filed

46
Q

for larger patients

A

decrease filed of view!!!
also increases collimation

47
Q

what is the relationship between beam restriction and receptor exposure?

A

increasing beam restriction will reduce receptor exposure.
-Receptor exposure is a collection of both primary and secondary radiation a larger Lightfield will increase the amount of radiation reaching the plate.

48
Q

what is FSS

A

focal spot size is used to control spatial resolution ( detail)
-small focal spots: produce less blurring and better visibility of detail ( extremity work and ribs)
-large focal spots: have a greater heat- dissipating capacity. (chest and abdomen)

49
Q

size distortion

A

magnification of the part
-primarily controlled by OID
-secondary controller is SID


50
Q

SID can be used to compensate for increase in OID

A

for every 1 inch increase in OID a 7-8 inch increase in SID should be used to compensate 

51
Q

1 inch =

A

2.54 cm

52
Q

40 inch

A

102 cm

53
Q

72 inch

A

183 cm

54
Q

shape distortion

A

is either elongation or foreshortening of the part 

55
Q

elongation

A

that part appears longer
resulting from the angle in the tube and image receptor (TIRE)
-we use this to help visualize anatomy for certain images, example and axial calcaneus 

56
Q

foreshortening

A

the part appears shorter
- angling the part
-happens in trauma

57
Q

what does filtration do

A

primary beam filtration reduces skin does by filtering out the low energy harmful rays 

58
Q

a filter is placed in the x-ray beam to remove long _________ x rays

A

wavelengths (low energy)
- Low energy, x-rays contribute nothing to the diagnostic image by increase patient toes through photo electric effect 

59
Q

has low energy x-rays are removed the average energy of the beam _____

A

increases

60
Q

removing the low energy raise results in a ________ patient dose 

A

lower
technologist never, just filtration it is only adjusted by the physicist 

61
Q

how will beam filtration affect the primary beam? 

A

It will make it more homogeneous by producing a beam of mainly high energy x-rays 

62
Q

filtration _____ the quantity of the beam

A

reduces

63
Q

filtration _______ receptor exposure

A

decrease

64
Q

filtration ______ the patient skin dose

A

reduces

65
Q

filtration _______ contrast

A

decreases

66
Q

what is inherent filtration

A

in the x ray tube
- in the glass envelope of the x-ray tube. Insulating oil around the tube. 

67
Q

added filtration

A

aluminum sheets placed in the path of the beam
-works as filters to attenuate low energy photons 

68
Q

what is total filtration

A

inherent + added

69
Q

Minimum filtration requirements NCRP 102

A

above 70 kvp= 2.5 mm Al equivalent

70
Q

compensating filters

A

compensating filters are external filters placed on the collimator of the x-ray tube. They are used to compensate for different thicknesses in densities. 

71
Q

common names for compensating filters 

A
  • wedge
    -boomerang
    -trough
  • a t spine varies in thickness and density a wedge filter may be used to compensate for the variance 
72
Q

Half value layer 

A

amount of filtration that reduces the intensity of that to half of its original value.
-Divide by two.
-use lead or AL sheets done by a physicist

73
Q

if you increase KVP the HVL

A

also increases

74
Q

what is the half value layer definition? 

A

decrease the intensity of the primary beam by 50% of its initial value 

75
Q

how many have cellular hours will it take to reduce an x-ray beam who is intensity is 78R/min to an intensity of less than 20 R/min 

A

2
78/2= 39
39/2= 19

76
Q

attenuation means what

A

the reduction in intensity of the x ray beam as result of absorption scatter and divergence

77
Q

higher atomic # = ________ attenuation

A

increased

78
Q

increase part thickness = ________ attenuation

A

increased

79
Q

increase in kVp= ______ attenuation

A

lower

80
Q

absorption

A

absorption of the x ray photons happens through the photoelectric effect

81
Q

differential absorption

A

different objects absorb radiation differently

82
Q

air = ______ absorption

A

decrease since it shows up black and isn’t as dense as bone!
bone = increased absorption

83
Q

where is AEC located

A
  • AEC units are found in either the table, Bucky or wall Bucky not in the image receptor
  • between the patient and the IR
84
Q

what does the technologist set when using AEC ex.) kvp

A
  • KVP
    -mA
    -select the appropriate chambers
    -the ioniziation chamber will determine the exposure time and terminate the exposure when the part is fully penetrated
85
Q

what are advantages of AEC

A
  • decreased repeat exposure rate due to underexposure
  • decreased pt exposure with less repeat images
    -increased department efficiency with less repeat images
86
Q

ionization chamber

A

behind the patient and in front of IR
- the ionization chamber interacts with exit radiation before it reaches the IR

87
Q

failure to center correctly using an AEC

A

Failure to center part of interest over the selected photocell can result in an over or under exposure!!!

88
Q

PA chest

A

use two outer cells

89
Q

factor changes that will affect AEC

A

as mA increases = AEC( length of exposure time) decreases. why: due to mAs recpiatory
as kVp increases= AEC decreases. why: have a higher energy beam more penetrating less time
as SID increases = AEC increases why: it’s going to take more time to get their
as density setting increases = AEC increase. why: use density setting so it can more dense or less dense + 1 or +2

90
Q

disadvantages of AEC

A
  1. accuracy position over selected cells
  2. pathology
  3. prosthetic devices
  4. collimation
91
Q

exposure index is what

A

conserve as an indicator of the relative exposure, used for a particular exam. Technologist should be educated on exposure ranges for each equipment used. exposure ranges are specific to equipment type and manufactur

92
Q

CR= S number

A

inverse relationship
high number = underexposed (600)
low number = over exposed ( under 75)

93
Q

DR= EI, DEL, REX#

A

direct relationship
high number = over exposed
low number = under exposed

94
Q

Variable KVP

A

kvp varies
mAs is constant 

95
Q

fixed kVp

A

kvp is fixed
mAs varies

96
Q

anatomically programmed technique

A

A suggested technique of KVP an mAs

97
Q

high voltage

A

used for barium and chest x ray

98
Q

ideal MTF is

A

1
- spatial resolution

99
Q

what is exposure latitude

A

exposure latitude is defined as the range of exposures that produces quality images at an appropriate patient dose 

100
Q

the higher the pulse the ______ voltage ripple

A

lower

101
Q

rotating anodes are used an x-ray tube

A

 Increase tube heat dissipation

102
Q

A radiograph of the abdomen is obtained using automatic exposure control. Which of the following is likely to occur if a second image is obtained after the introduction of 250 mL of oral barium?

A

Increased exposure time

  • AC will increase the exposure time to maintain image receptor exposure, because barium absorbs more radiation, and therefore more exposure is needed to produce a quality radiograph. 
103
Q

what is the function of AEC?

A

To provide proper exposure, and therefore image receptor exposure is maintained 

arrt prep (24 decks)

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