Introduction Flashcards

1
Q

ionization

A

electron is removed –> ion pair

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2
Q

ionizing radiation sources

A

cosmic, radon, imaging

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3
Q

radon gas

A

largest source of natural radiation

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4
Q

x-ray discovery

A
  • 11/9/95, Wilhelm Roentgen
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5
Q

x-ray properties

A
  • penetrability
  • ionizating
  • fluoresce and emit light
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6
Q

imaging system components

A
  • tube
  • operating console
  • high-V generator
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7
Q

x-rays are emitted..

A

isotropically (all directions)

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8
Q

cathode

A
  • negative end

- thoriated tungsten –> heat resistant filament

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9
Q

thermionic emission

A

filament temp rises until outer shell electrons “boil off”

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10
Q

focusing cup

A

(-) charged and confines accelerated electrons toward anode

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11
Q

anode

A
  • (+)
  • target (conductor)
  • dissipates heat
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12
Q

rotating anodes

A

reduced heat damage to tube

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13
Q

disadvantage of line-focus principle

A

anode heel-effect: electrons interact with target at various depths

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14
Q

uniform tissue exposure

A

anode must face thinner body part

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15
Q

Will the grid reduce extrafocal radiation?

A

NO

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16
Q

x-ray (high voltage) generator

A

modifies incomig voltage and current

17
Q

control panel

A

technical factors (mA, kV, Time)

18
Q

transformer

A

modifies voltage

19
Q

step-up transformer

A

V increase and I decreases for greater beam energy

20
Q

step-down transformer

A

V decrease and I increase to heat cathode for thermionic emission

21
Q

rectifiers

A

AC –> DC

22
Q

high-frequency power generator

A

provides constant potential V waveform which doubles radiation

23
Q

collimator

A

restricts x-ray to target area

24
Q

added filtration

A

aluminum filters to harden beam and improve penetrability and lessen scatter radiation

25
bucky system
grid that removes scatter radiation
26
Radiographic film
polyester and coated with emulsion containing silver halide crystals (SHC)
27
mAs
- milliamperage per second | - mAs --> x-ray quantity
28
kVp
- kilovoltage peak | - kVP --> x-ray quality (penetrability)
29
4 % kVp change
visible film changes
30
change of 5-10 kVp = ...
50% change in mAs
31
change in visible optical density
30 % change in mAs
32
10 kVp rule
change kVp by 10 results in same image density change as by increasing/decreasing mAs by 50 %
33
penumbra
- " almost, nearly" - blurring of image - increasing object film distance will increase penumbra
34
radiation intensity
inversely related to the square of the distance from the source