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Radiologic Science > Radio Science - Exam 3 Review > Flashcards

Radio Science - Exam 3 Review Flashcards

1
Q

Typical incoming voltage to high voltage circuit

A

220 V

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2
Q

Autotransformer

A

Makes adjustment to voltage before it’s stepped up

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3
Q

Location of Autotransformer

A

Low-voltage side of High Voltage Circuit for safety

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4
Q

Exposure switch/timer

A

Initiates exposure & terminates it in 1 of 3 ways

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5
Q

3 ways exposure switch/timer

A
  1. Manual timer
  2. mAs timer
  3. Automatic Exposure Control AEC
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6
Q

Step-up transformer turns ratio range

A

500:1 to 1000:1

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7
Q

Rectification bridge

A

-Diode that changes AC to DC
-When electrons approach n side, the electrons are repelled toward bridge
-Positive charge on p side repels its holes toward bridge
-At bridge, current can flow

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8
Q

2 components of X-ray tube

A

Cathode
Anode

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9
Q

Cathode

A

Negative side of X-ray tube
Thermionic emission

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10
Q

Anode

A

Positive side of X-ray tube
X-ray production

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11
Q

Rotor switch

A

Begins anode spin - 3400 rpm
Heats up filament within X-ray tube

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12
Q

Thermionic emission

A

Boiling off electrons from filament due to high amperage & high resistance

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13
Q

mA selection

A

Resistors

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14
Q

Step-down transformer

A

Ratio of 1:44
mA increased by factor of 44, up to 5 amps

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15
Q

Half-wave rectified & self-rectified circuits

A

60 pulses/sec
100% voltage ripple
30% average kVp

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16
Q

Single-phase, Full-wave rectified

A

120 pulses/sec
100% voltage ripple
30% average kVp

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17
Q

3-phase, 6-pulse generator

A

360 pulses/sec
14% voltage ripple
91% average kVp

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18
Q

3-phase, 12-pulse generator

A

720 pulses/sec
4% voltage ripple
97% average kVp

19
Q

High frequency generator

A

< 500 pulse/sec
<1% voltage ripple
100% average KV = Peak KV
Smooth waveform

20
Q

Cathode contains ___ filaments

A

2
small = 1 cm
large = 1.5 - 2 cm

21
Q

Filaments are made of ___

A

Thorium-impregnated tungsten
Z= 90

22
Q

Purpose of thorium

A

Helps w/ heat tolerance

23
Q

Space charge

A

Electron cloud forming around filament when rotor button is pushed

24
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

25
Q

Rotor

A

Connects to shaft & spins when influenced by stator (induction)

26
Q

Stator

27
Q

Target

A

Area of anode disk that’s struck by electrons
Made of tungsten & Rhenium (Z=75)

28
Q

X-ray tube failure

29
Q

Arcing

A

-Vaporized tungsten coats inside of tube & leads to arcing during exposure
-Type of short circuit
-Cracks glass
-Eliminates vacuum
-Burns out filament

30
Q

Protecting X-ray tube

A

Warm-up procedure
Avoid excessive rotoring
Heat units
Tube rating chart
Anode cooling chart

31
Q

Warm-up procedure to prevent ____

A

thermal shock

32
Q

Heat units

A

Capacity of anode to withstand heat
Heat units = constant x kVp x mA x exposure time
Heat units = 1.4 x kVp x mA x time

33
Q

Tube rating chart

A

Ensure technique will not exceed heat capacity of X-ray tube

34
Q

Electrons can accelerate to speeds of more than ___ the speed of ___ in ___ inch

A

1/2
speed of light
1 inch

35
Q

Anode interactions

A

Heat
Bremsstrahlung
Characteristic

36
Q

Anode interactions - heat

A

99.5% of interactions at 60 kV
99% of interactions at 100 kV

37
Q

Anode interactions - Bremsstrahlung

A

Braking radiation due to interactions w/ nucleus
Closer an electron passes to nucleus, the more it will be decelerated, more energy is lost in form of X-ray
Average kV exiting X-ray tube after filtration is 1/3 the kVp setting
Responsible for majority of created X-rays

38
Q

Characteristic X-ray formation

A
  1. Projectile electron from cathode interacts w/ INNER shell electron - electron is ejected
  2. Outer shell electron drops down to fill vacancy - energy released in form of X-ray
  3. Free electrons outside atom can fill vacancy too
  4. Strength of X-ray = difference between 2 binding energies
39
Q

Characteristic Cascade

A

Inner shell electrons replaced in sequence - multiple X-rays created
K replaced by L, L by M, M by N, etc

40
Q

X-ray beam/emission spectrum

A

Complete graph of all X-rays exiting X-ray tube from combination of Bremsstrahlung & characteristic spectrum

41
Q

Factors affecting X-ray emission spectrum

A

Target material
kVp
mAs
Added filtration
Generator type

42
Q

X-ray emission spectrum - mAs

A

mAs directly controls number of X-rays exiting X-ray tube
Doubling mAs will double number of X-rays created

43
Q

X-ray emission spectrum - Added filtration

A

Removes weak X-rays
Thus, increases average kV
Known as Hardening the X-ray beam

44
Q

X-ray emission spectrum - kVp

A

Increasing kVp will move X-ray emission spectrum to the right due to increased energy of resulting X-ray

Radiologic Science (3 decks)

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