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RADT 156 Equipment Operation > Tomo & AEC > Flashcards

Tomo & AEC Flashcards

(85 cards)

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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
large or small FSS for tomo?
small
26
why do we use long time for tomo
allow the tube to move during the exposure
27
what steps need to be taken to prepare the tomo unit
inform the patient the tube will move, move tube into starting position, unlock the bucky
28
tomo sweeps across tissue creating streaks is known as
phantom images
29
takes multiple exposures onto digital plate to make slices and recreate 3D structures
digital radiography tomosynthesis
30
mode of tomosynthesis that takes exposures repeatedly, IR then sends each image then reconstructs
stop and shoot
31
mode of tomosynthesis that uses a continuous beam
sweep
32
another name for constant beam in tomo
analog
33
what reconstructs images as a 3D model or radiograph in tomosynthesis?
a computer algorithm
34
when few projections are acquired in tomosynthesis
blurred ripple (phantom shadows)
35
peripheral info is cut off (vignetting)
truncation
36
what causes truncation
sweeping effect of the tube
37
Part moves during series of exposures creates artifact called
motion
38
3 types of DRT artifacts
blurred ripple, truncation, motion
39
AEC intensifying screen converts
photons to visible light
40
main purpose of automatic exposure control
terminate exposure time when predetermined charge is reached
41
what do photocells measure
ionization and electric charge, then terminate exposure when predetermined charge is reached
42
ADC type used by Hodges for photo-fluorography
ionization chamber type, used to react to different areas of anatomy
43
meaning of ADC
automatic density controls
44
meaning and purpose of AED
automatic exposure device, created to terminate exposure time automatically
45
process of determining correct amount of intensity is reached by image receptor for a specific degree of blackening
AEC - automatic exposure control
46
what do you lose control over when using AEC systems
mAs, time, density
47
when do ionization chamber type systems terminate exposure?
when the ionization chambers reach a predetermined charge
48
how many ionization chambers are typically found on an image receptor
3 - 5
49
single purpose of ionization chamber type systems
terminate exposure time
50
thickness of the thin parallel plate ionization chamber
6 mm
51
where electrons are put into motion to trigger the termination of exposure time in ionization chamber types
electrode (wire lead)
52
what ionizes during exposure in ionization chamber system
air
53
transmits electrons in current, is charged during ionization
electrode
54
amount of charge in ionization chamber is equivalent to
amount of radiation hitting the chamber
55
where does the current travel to in order to terminate exposure time
timer circuit
56
which sensor will have the greatest influence on density
the sensor receiving the greatest amount of exposure
57
when using multiple sensors, when is exposure terminated?
when average predetermined voltage is reached
58
when does a photomultiplier system terminate exposure time
when a predetermined amount of charge reaches the CAPACITOR
59
component in photomultiplier system that will trigger the exposure timer switches
capacitor
60
what determines when exposure switch is triggered in photomultiplier system
amount of fluorescence at phototube
61
what does the phototube convert
visible light to electrons
62
electrons in motion are called
current
63
maximum capacity of charge a capacitor can hold
capacitance
64
purpose of a capacitor
to hold charge
65
what does the fluorescent screen convert
photons to visible light
66
brightness in fluorescent screen is directly related to
intensity of the x-ray beam
67
photomultiplier tube )phototube) is coated with
alkali metal such as potassium and cesium
68
in a phototube, the amount of current is directly proportional to
the amount of light energy
69
another name for thyraton or thyristor
"trigger tube"
70
three electrodes of the thyraton or thyristor (triode)
anode, cathode, grid
71
part of photomultiplier system that conducts voltage and triggers timer relay switch
thyraton or thyristor
72
faster trigger tube that allows 1 msec delays
thyristor
73
part that is triggered by the thyraton (mouse trap)
relay
74
purpose of the relay
sends current to the exposure switch
75
when is exposure switch opened
when excessive current increases potential difference on its contacts
76
system that combines AED with computerized exposure chart
anatomically programmed system
77
what does the anatomically programmed system pre-select?
kV, mA, FSS, ionization chambers used
78
what does AEC not control?
image quality
79
if sensors are collimated off, image will be over or underexposed?
overexposed
80
purpose of back up time
to protect the unit and patient
81
at above 50 kV, what mAs are generators required to terminate exposure at?
600 mAs
82
what percentage of anticipated manual exposure is the back up time set at
150% of anticipated exposure
83
types of anticipated errors that back up time protects from
inaccurate sensor selection, shielding, tube not centered
84
minimum response time of AEC
0.05 or 0.001 sec depending on unit and IR
85
Type of tomography where the patient moves but the tube does not
Autotomography

RADT 156 Equipment Operation (4 decks)

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