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RADT 156 Equipment Operation > Tomo & AEC > Flashcards

Tomo & AEC Flashcards

1
Q

what move during tomo

A

tube and image receptor

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2
Q

Where is blur created in tomography

A

planes above and below area of interest

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3
Q

intentional motion unsharpness in tomo

A

blur

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4
Q

as the tomo angle increases, blur ___

A

increases

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5
Q

where is blur the greatest

A

above the focal point because OID

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6
Q

other names for tomo

A

body section radiography, planography, zonography, laminography, autotomography

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7
Q

most common type of tomo rotation / movement

A

linear

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8
Q

which part connects the tube to the bucky

A

armature

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9
Q

device that selects the pivotal point which the armature and image receptor rotate

A

fulcrum

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10
Q

selects the distance from the image receptor where the sharp focal plane will be imaged

A

fulcrum

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11
Q

the distance the tube travels, expresed in degrees

A

tomographic angle / arc / amplitude

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12
Q

point where the x-ray beam intersects

A

focal point

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13
Q

area of sharply defined structures

A

focal plane

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14
Q

angle created in the movement of the tube

A

tomographic angle

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15
Q

angle that beam is on during exposure

A

exposure angle

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16
Q

another name for tomographic angle

A

stroke distance

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17
Q

distance in inches the tube will travel in a certain time frame

A

stroke velocity

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18
Q

distortion of objects outside of focal plane as a result of motion of the tube / IR

A

blur

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19
Q

if the tomo angle is small, will the section be thick or thin?

A

thick

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20
Q

what determines the thickness of the sharp image section

A

tomographic angle / arc / amplitude, otherwise known as stroke distance

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21
Q

where is blur the greatest?

A

above the focal point

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22
Q

selection of the thickness of the section depends on:

A

the size of the part, the number of sections to be imaged through part

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23
Q

what factors determine the amount of blur?

A

distance from focal plane, distance from IR, tube travel orientation, tomographic angle

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24
Q

true or false: SID changes do NOT change tomographic angle

A

true

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25
Q

large or small FSS for tomo?

A

small

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26
Q

why do we use long time for tomo

A

allow the tube to move during the exposure

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27
Q

what steps need to be taken to prepare the tomo unit

A

inform the patient the tube will move, move tube into starting position, unlock the bucky

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28
Q

tomo sweeps across tissue creating streaks is known as

A

phantom images

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29
Q

takes multiple exposures onto digital plate to make slices and recreate 3D structures

A

digital radiography tomosynthesis

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30
Q

mode of tomosynthesis that takes exposures repeatedly, IR then sends each image then reconstructs

A

stop and shoot

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31
Q

mode of tomosynthesis that uses a continuous beam

A

sweep

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32
Q

another name for constant beam in tomo

A

analog

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33
Q

what reconstructs images as a 3D model or radiograph in tomosynthesis?

A

a computer algorithm

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34
Q

when few projections are acquired in tomosynthesis

A

blurred ripple (phantom shadows)

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35
Q

peripheral info is cut off (vignetting)

A

truncation

36
Q

what causes truncation

A

sweeping effect of the tube

37
Q

Part moves during series of exposures creates artifact called

A

motion

38
Q

3 types of DRT artifacts

A

blurred ripple, truncation, motion

39
Q

AEC intensifying screen converts

A

photons to visible light

40
Q

main purpose of automatic exposure control

A

terminate exposure time when predetermined charge is reached

41
Q

what do photocells measure

A

ionization and electric charge, then terminate exposure when predetermined charge is reached

42
Q

ADC type used by Hodges for photo-fluorography

A

ionization chamber type, used to react to different areas of anatomy

43
Q

meaning of ADC

A

automatic density controls

44
Q

meaning and purpose of AED

A

automatic exposure device, created to terminate exposure time automatically

45
Q

process of determining correct amount of intensity is reached by image receptor for a specific degree of blackening

A

AEC - automatic exposure control

46
Q

what do you lose control over when using AEC systems

A

mAs, time, density

47
Q

when do ionization chamber type systems terminate exposure?

A

when the ionization chambers reach a predetermined charge

48
Q

how many ionization chambers are typically found on an image receptor

A

3 - 5

49
Q

single purpose of ionization chamber type systems

A

terminate exposure time

50
Q

thickness of the thin parallel plate ionization chamber

A

6 mm

51
Q

where electrons are put into motion to trigger the termination of exposure time in ionization chamber types

A

electrode (wire lead)

52
Q

what ionizes during exposure in ionization chamber system

A

air

53
Q

transmits electrons in current, is charged during ionization

A

electrode

54
Q

amount of charge in ionization chamber is equivalent to

A

amount of radiation hitting the chamber

55
Q

where does the current travel to in order to terminate exposure time

A

timer circuit

56
Q

which sensor will have the greatest influence on density

A

the sensor receiving the greatest amount of exposure

57
Q

when using multiple sensors, when is exposure terminated?

A

when average predetermined voltage is reached

58
Q

when does a photomultiplier system terminate exposure time

A

when a predetermined amount of charge reaches the CAPACITOR

59
Q

component in photomultiplier system that will trigger the exposure timer switches

A

capacitor

60
Q

what determines when exposure switch is triggered in photomultiplier system

A

amount of fluorescence at phototube

61
Q

what does the phototube convert

A

visible light to electrons

62
Q

electrons in motion are called

A

current

63
Q

maximum capacity of charge a capacitor can hold

A

capacitance

64
Q

purpose of a capacitor

A

to hold charge

65
Q

what does the fluorescent screen convert

A

photons to visible light

66
Q

brightness in fluorescent screen is directly related to

A

intensity of the x-ray beam

67
Q

photomultiplier tube )phototube) is coated with

A

alkali metal such as potassium and cesium

68
Q

in a phototube, the amount of current is directly proportional to

A

the amount of light energy

69
Q

another name for thyraton or thyristor

A

“trigger tube”

70
Q

three electrodes of the thyraton or thyristor (triode)

A

anode, cathode, grid

71
Q

part of photomultiplier system that conducts voltage and triggers timer relay switch

A

thyraton or thyristor

72
Q

faster trigger tube that allows 1 msec delays

A

thyristor

73
Q

part that is triggered by the thyraton (mouse trap)

A

relay

74
Q

purpose of the relay

A

sends current to the exposure switch

75
Q

when is exposure switch opened

A

when excessive current increases potential difference on its contacts

76
Q

system that combines AED with computerized exposure chart

A

anatomically programmed system

77
Q

what does the anatomically programmed system pre-select?

A

kV, mA, FSS, ionization chambers used

78
Q

what does AEC not control?

A

image quality

79
Q

if sensors are collimated off, image will be over or underexposed?

A

overexposed

80
Q

purpose of back up time

A

to protect the unit and patient

81
Q

at above 50 kV, what mAs are generators required to terminate exposure at?

A

600 mAs

82
Q

what percentage of anticipated manual exposure is the back up time set at

A

150% of anticipated exposure

83
Q

types of anticipated errors that back up time protects from

A

inaccurate sensor selection, shielding, tube not centered

84
Q

minimum response time of AEC

A

0.05 or 0.001 sec depending on unit and IR

85
Q

Type of tomography where the patient moves but the tube does not

A

Autotomography

RADT 156 Equipment Operation (4 decks)

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