RT: 34 > Circuitry > Flashcards

Circuitry Flashcards

(59 cards)

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1
Q

What are the 3 main parts of the x-ray imaging system

A
  1. Operating console
  2. High Voltage generator
  3. X-ray Tube
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2
Q

Where is the ____ located at:

  1. Operating console
  2. High voltage generator
A
  1. Inside the room but outside the radiation area

2. Adjacent to the x-ray tube in a cabinet or closet

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3
Q

What is the function that all diagnostic x-ray imaging systems perform?

A

Provide ionizing radiation for medical imaging

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4
Q

Most imaging systems operate at ____ kVp and ____ mA?

A
  1. 25-150 kVp

2. 100-1200 mA

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5
Q

What is between the operator and the radiation area?

A

Leaded wall equipped with leaded glass

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6
Q

The operating console provides control for:

A
  • is a Low voltage circuit*
    1. Line compensation
    2. kVp
    3. mA
    4. Exposure time
    5. AEC controls
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7
Q

All of the circuits withing the console are ______ to protect us from electric shock

A

Low voltage

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8
Q

What are 3 functional parts of the x-ray circuit

A
  1. Primary Circuit
  2. Secondary Circuit
  3. Filament Circuit
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9
Q

Describe the primary circuit

A
  1. Consists of:
    - Console panel
    - Auto transformer
    - kVp selector
    * * It is low voltage circuit*
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10
Q

Describe what the secondary circuit houses (5)

and what side of the tube does it enter

A 
= High voltage circuit
Houses:
1. Step up transformer
2.Rectifier 
3.mA meter
4.Ground
5.Focal spot selector ( it only houses, Function is part of the filament circuit)

It Enters anode side of tube

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11
Q

Describe what the filament circuit consists of

  • What is its function:
A
  1. mA selector
  2. Focal spot selector
  3. Step down transformer
  4. Resistors

Function:

  • Controls current
  • Controls temp to filament
  • determines level of thermionic emission
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12
Q

Define line compensator

A

Measures and adjust the voltage to 220 V

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13
Q

Supplied voltage from the power company can vary by ____ %, Which is why line compensatory measure and regulate voltage

A

5%

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14
Q

If the power supply from the wall can vary up to 5%, what are the repercussions of the variance?

A

Beam intensity will vary by 5% which can affect the image quality leading to repeats.

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15
Q

220 V are supplied from the wall but ____ is needed when we create x-ray

A

kilo volts (kV)

  • So the power supply (V) must go through the auto-transformer to convert V into kV
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16
Q

Describe autotransformers

A
  • Consists of a single winding and single core
  • Operates on self induction
  • Supplies regulated voltage to : Filament circuit & High voltage circuit
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17
Q

The power supplied to the x-ray imaging system is delivered first to the ____

A

Auto transformer

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18
Q

Auto transformers are designed to “step up” the voltage approx. ____ the input voltage

A

2x’s

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19
Q

Primary voltage comes from ____

A

Input voltage from the wall

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20
Q

secondary voltage comes from?

A

Output voltage from the auto transformer

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21
Q

Describe the primary side of the main x-ray circuit

A
  • Located on the console panel
  • Consists of:
  • *preselected kVp meter
  • *auto transformer
  • *Line compensator
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22
Q

_____ on the primary side of the main x-ray circuit , “reads the output voltage”

-Why does the meter scale register in kV

A

kVp meter

– Measure in kV because it is programmed with the turn ratios across the auto transformer

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23
Q

What are the 3 types of timer selectors (circuits)

A
  1. Electronic timer:
    (most common & accurate to 1 ms)
  2. mAs timer:
    (Located on secondary side to monitor tube current)
  3. AEC timer:
    ( it is time dependant on proper amt. of radiation hitting the chambers
    - It is back up electronic timer)
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24
Q

What is the function of the mAs timer

Study These Flashcards
A

made to operate highest tube current for short exposure

25
The number of electrons emitted by the filament is determined by the ___ ?? It is controlled by the -?
1.temperature of the filament (thermionic emission) 2. Controlled by current (Amperes) ( current increases , then temp increases which results in more "boiling off of electrons)
26
Define thermionic emission
emission of electrons from a heated surface
27
What stops exposure in 1. X-ray 2. Fluor
1. Radiographer starts & the Console stops | 2. Radiographer starts and stops the exposure in fluoro
28
What is the exposure back up set at?
max. mAs = 600 mAs or 6s ( whichever comes first)
29
What does the filament circuit control
Controls: - Current (A) - # of electrons emitted by filament - these circuits normally bump up amps
30
filament circuit bumps up amps to ___- ___ A. How ?
1. 3-6 Amps | 2. It is done by step down transformer which decreases volts and therefore increases amps
31
What type of "step" transformer is the filament transformer - What is its purpose - and voltage it supplies
Step down transformer = provides current to the heat filament = Decreases Voltage to 12 V, increases A
32
Describe the voltage path from the auto transformer to the filament circuit
Voltage is supplied to the mA selector from the secondary connections of the auto transformer - Then the voltage travels to the filament switch - Then to the filament transformer ( this is where the voltage is decreased to 12 v)
33
The filament circuit enters which side of the x-ray tube
cathode side
34
Which circuit is : 1. Low voltage 2. High voltage
1. Primary circuit ( operating console) | 2. Secondary circuit High voltage generator
35
____ of the x-ray imaging system is responsible for increasing the output voltage from the auto transformer to the kV necessary for x-ray production
High voltage generator
36
In which part of the circuitry is the focal spot selector located in
Located in the high voltage side ( secondary circuit) but is part of the filament circuit
37
The high voltage generator consists of 3 parts:
1. High voltage transformer 2. Filament transformer 3. Rectifiers
38
In regards to Filament components: The primary circuit houses the : ___ & The secondary circuit houses the: ___
1. mA selector | 2. Focal spot selector 3.Step down transformer slide 41
39
Why is the filament circuit separate from the primary and secondary circuits?
Because it's components lie in both primary and secondary circuits
40
Which circuit is a "step up transformer" and why?
Secondary circuit is a "step Up transformer" because it converts the voltage received from the auto transformer into kV
41
____ is the process of converting AC to DC. Why is it needed
= Rectification * needed to ensure electrons travel one way once they reach they reach the x-ray tube ( From cathode to anode)
42
Describe the difference between old rectifiers and new ones
Old rectifiers were vacuum tubes called "Valve tubes" Current rectifiers = solid state diodes made of silicon
43
____ conduct electricity in one direction
Rectifiers
44
___ is an electronic device that contains 2 electrodes
Diodes * arrowhead of the diode symbol indicates the direction of the current ( opposite of electron flow)
45
What does the filament circuit consists of?
- mA selector - Focal spot selector - Step down filament transformer
46
Describe un-rectified voltage
Located on the secondary side of high voltage step up transformer -Wave form looks the same as the primary side except that the amplitude is larger
47
Describe half wave rectification
=Voltage can not swing negatively during the negative half of the cycle ( bottom part of wave) Therefore: - only 1/2 the supply power is used - Takes twice the exposure time - Consists of 0,1 or 2 diodes - X-ray pulse 60 times/s
48
Describe full wave rectification
- Entire AC wave is rectified - Contains at least 4 diodes - Exposure time is cut in half - X-ray pulse 120/s
49
Which generator do we use today to produces a nearly constant potential voltage waveform, improving image quality at lower dose
High frequency generators
50
Name advantages of the high frequency generator
-Smaller than single phase & three phase - less costly - More efficient
51
High frequency generators are used in which exams:
1. Mammograhy 2. Portable units 3. CT
52
____ is the measure of variation in voltage waveform
Voltage ripple
53
What is the voltage ripple for: 1. Single phase waveform: 2. 3 phase, 6 pulse wave form 3. 3 phase, 12 pulse waveform: 4. High frequency generator:
1. 100% - This is because voltage varies from 0 to its max value 2. 14% - Voltage never falls below 0. 3.4% 4. 1% = constant exposure
54
less voltage ripple results in ___?
increase x-ray quantity & Quality
55
Which generator is used in portable x-ray machines
High frequency because them are much more compact and less costly.
56
We use ____ rectification with _____ generation in almost all stationary x-ray imaging systems today
1. Full wave rectification 2. High frequency voltage generator = Ensures integrity of power is constant
57
What is the purpose of a capacitor
stores high voltage then discharges | 1 kV/mAs during exposure
58
During exposure the capacitor discharge generator discharges ____ during exposure
1 kV/mAs
59
The secondary circuit enters the _____ side of the tube
Anode
RT: 34
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