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Donny Radiologic Sciences 1 > Exam 3 Review (s1) > Flashcards

Exam 3 Review (s1) Flashcards

Review exam 3 (79 cards)

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1
Q

What is the Typical incoming line voltage to the high voltage circuit?

A

220 volts

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2
Q

Autotransformer:

A

makes adjustments to voltage before it is stepped-up
on low-voltage side of the high voltage circuit for safety

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3
Q

3 ways the exposure switch and exposure time initiates/terminates

A

manual timer
mAs timer
Automatic exposure control (AEC)

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4
Q

What is part A in the xray machine?

A

Main power switch
&
circuit breaker

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5
Q

What is part B in the xray machine?

A

Autotransformer

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6
Q

What is part C in the xray machine?

A

Exposure switch
&
exposure timer

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7
Q

What is part D in the xray machine?

A

Kvp Meter
(parallel circuit)

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8
Q

What is part E in the xray machine?

A

Step-up transformer
turn ratio 500:1 to 1000:1

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9
Q

What is part F in the xray machine?

A

mA meter
(series circuit)

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10
Q

What is part G in the xray machine?

A

Rectification bridge
(changes alternate to direct current)

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11
Q

What is part H in the xray machine?

A

x-ray tube
thermionic emission- cathode (-)
x-ray production- anode (+)

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12
Q

What is part I in the xray machine?

A

Rotor switch
anode spin at 3400 RPM
heats up the filament
boils off electrons from filament due to high amps and high resistance

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13
Q

What is part J in the xray machine?

A

mA selection
(resistors)

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14
Q

What is part K in the xray machine?

A

Step Down Transformer
ratio 1:44

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15
Q

Main power switch and circuit breaker (step?):

A

A
typical incoming line voltage to the high voltage circuit is 220V

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15
Q

Autotransformer (step?):

A

B
adjusts voltage before stepping up

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16
Q

Exposure switch and time (step?):

A

C
initiates exposure and terminates 1 of 3 ways:
Manual timer
mAs Timer
Automatic exposure control (AEC)

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17
Q

Kvp Meter (step?):

A

D
measures the Kvp
(parallel)

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18
Q

Step-up transformer (step?):

A

E
turns ratio 500:1- 1000:1

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19
Q

mA meter (step?):

A

F
Measures the amount of mA
(series)

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20
Q

Rectification bridge (step?):

A

G
Diode changes alternate to direct current
electrons approach ā€œnā€ side, electrons are repelled towards bridge
p is positive side that repels holes toward the bridge

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21
Q

x-ray tube (step?):

A

H
thermionic emission (cathode)
x-ray production (anode)

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22
Q

rotor switch (step?):

A

I
spins anode 3400 rpm
heats up filament in the x-ray tube
thermionic emission due to high amperage and high resistance

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23
Q

mA selection (step?):

A

J
Resistors
more resistors less amperage (vice versa)

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24
Step down transformer (step?): mA increased by:
K ratio of 1:44 mA is increased by a factor of 44, up to 5 AMPS
25
Thermionic emission:
"BOILING OFF" electrons from filament due to high amperage and high resistance
26
Half wave/self-rectified circuits
60 pulses a second 100% voltage ripple 30% average Kvp
27
single-phase/ full wave rectified
120 pulses a second 100% voltage ripple 30% average Kvp
28
3 phase/ 6-pulse generators
360 pulses per second 14% voltage ripple 91% average Kvp
29
3-phase/ 12-pulse generators
720 pulses per second 4% voltage ripple 97% average Kvp
30
high frequency generators
greater than 500 pulses per second 500< 1% voltage ripple 100% average kvp hz is altered from 60 to 500-25,000 HZ
31
Ch 9: xray tube Cathode:
negative side of the x-ray tube Thermionic emission
32
Ch 9: xray tube How many filaments in x-ray tube?
2 filaments small= 1 cm large: 1.5-2 cm
33
What does focal spot do? Small? Large?
smaller focal spot creates sharper images large focal spot better for high heat x-rays (L-spine)
34
Filaments are made up of:
thorium-impregnated tungsten thorium z=90 helps with heat tolerance
35
Thermionic emission occurs in the: What is thermionic emission?
Cathode "boils off" electrons from the filament due to high current flow and high resistance
36
What is space charge?
electron cloud forms around the filament when the rotor button is pushed
37
focal spot (in anode) is _% of filament?
5% (0.5mm-1mm)
38
Focusing cup: What is its charge?
Negative charge prevents electrons from rushing away by surrounding the filament (negative focusing cup narrows the electrons due to the law of attraction)
39
Focal spot for hands/feet x-rays:
Small focal spot 1cm
40
focal spot for lateral lumbar:
large focal spot 1.5cm to 2cm
41
Anode:
positive side of the x-rays tube Xray production
42
Rotor: A part of what?
Anode Connects the shaft and spins when influenced by the stator (induction)
43
Target: A part of what?
area of the anode disk that is struck by the electrons made of tungsten and rhenium z=75
44
What is struck by electrons in the xray tube?
the target in the anode (anode disk) very durable to high amounts of heat
45
Main cause of x-ray tube failure?
arcing
46
What is arcing?
vaporized tungsten coats the inside of the tube type of short circuit: 1. cracks the glass 2. eliminates vacuum 3. burns out the filament
47
What is a way we can protect the x-ray tube?
warm up procedures to prevent thermal shock (hot water on cold glass=crack) avoid excessive rotoring calculate the heat units to prevent overheating of the anode
48
what is heat units for?
to measure how much heat the anode can withstand (a unit of measurement for anode heat capacity)
49
HU (heat units) formula:
1.4 (constant/ don't forget) x kVp x mA x s (seconds)
50
What is the purpose for a tube rating chart?
to ensure that a technique will not exceed the heat capacity of an x-ray tube
51
What is the anode cooling chart purpose?
how long will it take for the anode to cool before making another exposure.
52
stream of electrons: How fast?
using the voltages in x-ray electrons can accelerate at 1/2 the speed of light in just one inch
53
heat interactions:
99.5% of interactions at 60 Kv 99% of interactions at 100 kv
54
Bremsstrahlung:
"braking radiation" interactions with the nucleus
55
bremsstrahlung is responsible for the:
vast majority of x-rays
56
how does Bremsstrahlung work?
closer an electron passes to the nucleus, the more it will be declerated and more energy is lost in the form of an x-ray
57
In Bremsstrahlung was is the average kv exiting?
(The avg kv after filtration is 1/3 of kvp setting) the average KV exiting the xray tube after filtration is about 1/3 of the kVp setting
58
Characteristic:
projectile electron from CATHODE interacts with INNER shell electron it can be ejected
59
What are the steps of characteristic?
1. electron interacts with inner shell electron 2. outer shell electron will drop down to fill the vacancy (L to K) 3. The strength of the x-ray is equal to the difference between the two shell electrons
60
Any _____ can fill the vacancy in an inner shell electron, including ____ _______ outside the atom in characteristic
Electrons Free electrons
61
Characteristic cascade:
Inner shell electrons are replaced in sequence (k by L,L by M, M by N,N by O). MULTIPLE x-rays are created
62
The result of characteristic cascade is x-rays at _____ _________
Specific energies K shell- 57, 66, 68, 69 KV L shell- 9,11,12 KV
63
(T/F) when the Bremsstrahlung spectrum and characteristic spectrum are combined we have a complete graph of all the x-rays leaving the x-ray tube
True
64
What are factors that affect the x-ray emission spectrum?
1. Target material (mammography) 2. Milliampere-seconds (mAs) 3. added filtration 4. Kilovoltage-peak (kVp) 5. generator type (3 are of these are most common)
65
mAs directly controls the number:
of x-rays that exit the tube
66
Doubling mAs will:
double the amount of x-rays created
67
Filtration removes what kind of xrays? adding more filtration will:
Filtration removes weak x-rays and adding more filtration will remove even more weak ones Increasing the average kvp
68
When we filtrate more x-rays what happens to the average KV? What is this known as?
the average KV will go up this is known as "hardening" the x-ray beam
69
Increasing the kVp will move:
the x-ray emission spectrum to the right due to the increase energy from x-rays
70
How do generator type play a role in x-ray emission spectrum?
single phase high frequency etc (Changes the pulses, voltage ripple, average kvp)
71
Things to concentrate on:
The xray machine and circuits The x-ray tube read and do math on anode cooling chart read the max exposure time graph
71
How does target material play a role in the x-ray emission spectrum? (won't be tested much on)
(Certain material will lower the average kvp) like in mammography the material of the target will affect the average KV (ex: in mammography avg is 17 KV)
72
Focusing cup
Surrounds filaments Prevents electrons from rushing away from each other Resulting focal spot in anode is 5% size of filament -- 0.5 - 1 mm
73
Thermionic emission in the CATHODE:
a "boiling off" of electrons from the filament due to high current flow and high resistance
74
Average KV after exiting the x-ray tube after:
filtration is about 1/3 of the kVp setting
75
At the bridge current:
can flow
76
(T/F) free electrons outside of the atom can fill the vacancy of the inner shell?
True ANY electron
77
Hardening the x-ray beam:
adding more filtration for weak x-rays thus increasing the average kVp

Donny Radiologic Sciences 1 (5 decks)

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