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

Exam 3 Review (s1) Flashcards

Review exam 3

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 “n” 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
Q

Step down transformer (step?):
mA increased by:

A

K
ratio of 1:44
mA is increased by a factor of 44, up to 5 AMPS

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25
Q

Thermionic emission:

A

“BOILING OFF” electrons from filament due to high amperage and high resistance

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26
Q

Half wave/self-rectified circuits

A

60 pulses a second
100% voltage ripple
30% average Kvp

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27
Q

single-phase/ full wave rectified

A

120 pulses a second
100% voltage ripple
30% average Kvp

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28
Q

3 phase/ 6-pulse generators

A

360 pulses per second
14% voltage ripple
91% average Kvp

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29
Q

3-phase/ 12-pulse generators

A

720 pulses per second
4% voltage ripple
97% average Kvp

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30
Q

high frequency generators

A

greater than 500 pulses
per second 500<
1% voltage ripple
100% average kvp
hz is altered from 60 to 500-25,000 HZ

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31
Q

Ch 9: xray tube
Cathode:

A

negative side of the x-ray tube
Thermionic emission

32
Q

Ch 9: xray tube
How many filaments in x-ray tube?

A

2 filaments
small= 1 cm
large: 1.5-2 cm

33
Q

What does focal spot do?
Small?
Large?

A

smaller focal spot creates sharper images
large focal spot better for high heat x-rays (L-spine)

34
Q

Filaments are made up of:

A

thorium-impregnated tungsten
thorium z=90 helps with heat tolerance

35
Q

Thermionic emission occurs in the:
What is thermionic emission?

A

Cathode
“boils off” electrons from the filament due to high current flow and high resistance

36
Q

What is space charge?

A

electron cloud forms around the filament when the rotor button is pushed

37
Q

focal spot (in anode) is _% of filament?

A

5%
(0.5mm-1mm)

38
Q

Focusing cup:
What is its charge?

A

Negative charge
prevents electrons from rushing away by surrounding the filament (negative focusing cup narrows the electrons due to the law of attraction)

39
Q

Focal spot for hands/feet x-rays:

A

Small focal spot
1cm

40
Q

focal spot for lateral lumbar:

A

large focal spot
1.5cm to 2cm

41
Q

Anode:

A

positive side of the x-rays tube
Xray production

42
Q

Rotor:
A part of what?

A

Anode
Connects the shaft and spins when influenced by the stator (induction)

43
Q

Target:
A part of what?

A

area of the anode disk that is struck by the electrons
made of tungsten and rhenium z=75

44
Q

What is struck by electrons in the xray tube?

A

the target in the anode (anode disk)
very durable to high amounts of heat

45
Q

Main cause of x-ray tube failure?

A

arcing

46
Q

What is arcing?

A

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
Q

What is a way we can protect the x-ray tube?

A

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
Q

what is heat units for?

A

to measure how much heat the anode can withstand
(a unit of measurement for anode heat capacity)

49
Q

HU (heat units) formula:

A

1.4 (constant/ don’t forget)
x
kVp
x
mA
x
s (seconds)

50
Q

What is the purpose for a tube rating chart?

A

to ensure that a technique will not exceed the heat capacity of an x-ray tube

51
Q

What is the anode cooling chart purpose?

A

how long will it take for the anode to cool before making another exposure.

52
Q

stream of electrons:
How fast?

A

using the voltages in x-ray electrons can accelerate at 1/2 the speed of light in just one inch

53
Q

heat interactions:

A

99.5% of interactions at 60 Kv
99% of interactions at 100 kv

54
Q

Bremsstrahlung:

A

“braking radiation”
interactions with the nucleus

55
Q

bremsstrahlung is responsible for the:

A

vast majority of x-rays

56
Q

how does Bremsstrahlung work?

A

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
Q

In Bremsstrahlung was is the average kv exiting?

A

(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
Q

Characteristic:

A

projectile electron from CATHODE interacts with INNER shell electron
it can be ejected

59
Q

What are the steps of characteristic?

A
  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
Q

Any _____ can fill the vacancy in an inner shell electron, including ____ _______ outside the atom in characteristic

A

Electrons
Free electrons

61
Q

Characteristic cascade:

A

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
Q

The result of characteristic cascade is x-rays at _____ _________

A

Specific energies
K shell- 57, 66, 68, 69 KV
L shell- 9,11,12 KV

63
Q

(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

A

True

64
Q

What are factors that affect the x-ray emission spectrum?

A
  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
Q

mAs directly controls the number:

A

of x-rays that exit the tube

66
Q

Doubling mAs will:

A

double the amount of x-rays created

67
Q

Filtration removes what kind of xrays?
adding more filtration will:

A

Filtration removes weak x-rays and adding more filtration will remove even more weak ones
Increasing the average kvp

68
Q

When we filtrate more x-rays what happens to the average KV?
What is this known as?

A

the average KV will go up
this is known as “hardening” the x-ray beam

69
Q

Increasing the kVp will move:

A

the x-ray emission spectrum to the right due to the increase energy from x-rays

70
Q

How do generator type play a role in x-ray emission spectrum?

A

single phase
high frequency
etc
(Changes the pulses, voltage ripple, average kvp)

71
Q

Things to concentrate on:

A

The xray machine and circuits
The x-ray tube
read and do math on anode cooling chart
read the max exposure time graph

71
Q

How does target material play a role in the x-ray emission spectrum?
(won’t be tested much on)

A

(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
Q

Focusing cup

A

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
Q

Thermionic emission in the CATHODE:

A

a “boiling off” of electrons from the filament due to high current flow and high resistance

74
Q

Average KV after exiting the x-ray tube after:

A

filtration is about 1/3 of the kVp setting

75
Q

At the bridge current:

A

can flow

76
Q

(T/F) free electrons outside of the atom can fill the vacancy of the inner shell?

A

True
ANY electron

77
Q

Hardening the x-ray beam:

A

adding more filtration for weak x-rays
thus increasing the average kVp

Donny Radiologic Sciences 1 (5 decks)

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