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202 MEDIMAGE > 6. X-Ray Hardware > Flashcards

6. X-Ray Hardware Flashcards

1
Q

what is beam filtration and what does it do to the beam

A

filtration hardens the x-ray beam

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2
Q

the standard bremsstrahlung spectrum is formed by which type of filtration

A

inherent filtration of machine

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3
Q

what is beam hardening

A

increases average energy of x ray beams by removing the lower energies because of presence of filtrating materials

lead to only higher energy beam passing through so higher quality

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4
Q

why are low energy photons undesirable

A

Low energy photon very unlikely to exit patient so not contributing to image quality at all so bad for patient as extra energy/radiation without any image benefits

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5
Q

what happens to the k edge of attenuation as you increase keV

A

increases but at a certain point you match the e- orbital and get extra absorption of photon and more attenuation

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6
Q

contrast between tumor and breast tissue gets smaller with increasing/decreasing kV

A

increasing

increase kV = lower contrast

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7
Q

what are compensating filters

A

modifies the x-ray beam intensity across the field of view

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8
Q

what is added filtration

A

filtration that is added to the port of x-ray tube

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9
Q

what does added filtration do in terms of the photon energy

A

absorbs more low energy photons while higher energy photons can exit

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10
Q

what are inherent filtration

A

filtration that is permanently in the path of the x-ray beam

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11
Q

what are the 3 components that contribute to the inherent filtration

A

envelope of the tube

oil that surrounds the tube

window of tube housing

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12
Q

what is the total filtration

A

sum of added and inherent filtration

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13
Q

what is compensating filtration

A

added to the primary beam to alter its intensity

used to image areas that are non-uniform in makeup and assist in producing more consistent exposure to the IR

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14
Q

what is the heat unit

A

amount of heat produced from any given exposure

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15
Q

what 2 factors does the HU depend on

A

type of x-ray generator

exposure factors selected

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16
Q

what is the equation for HU

A

HU = mA x time x kVp x generator factor

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17
Q

what are tube rating charts

A

gives the max current that you can run through the x-ray tube

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18
Q

what are the 2 factors that need to be satisfied in terms of the machines voltage source

A

Need to get voltage as high as we need

Need a way to keep voltage constant with the machinery

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19
Q

what are the 2 types of diodes in terms of bias

A

forwards and reverse bias

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20
Q

what are diodes and what are they made of

A

Diodes are solid state electrical device, has semi conductor type materials in it

allows current flow in one direction and restricts it in another (acts as a one way switch)

Inside you have 2 materials, one which we made slightly more positive than the other and the other you dope with some positive charge with some insulating material in the middle

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21
Q

what are forward bias diodes and what is their charge distribution

is there conduction

A

Top positive (where the + charges are) bottom negative (where the - charges are)

Positive charges are repelled downwards and produces a current and allows current to go through so is in the conductive state

e- and holes more across the junction

conduction

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22
Q

what are reverse bias diodes and what is their charge distribution

is there conduction

A

Top negative (where the + charges are) bottom positive(where the - charges are)

they’re attracted to opposite charge so don’t flow through insulating material and no conduction as stay away from junction in the middle

e- and holes stay away from the junction

no conduction

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23
Q

when the diode acts in a forward bias in a AC current what does the diode become in terms of conduction

A

becomes conductor

acts like a closed circuit

24
Q

when the diode acts in a reverse bias in a AC current what does the diode become in terms of conduction

A

diode does not conduct

no current flow

25
Q

a diode in a AC circuit produces what

A

half rectified waveform

26
Q

what does the diode do to the waveforms in a AC current

A

Can take signal that’s alternating and makes it completely positive so when its negative there’s no current at all but when its positive it allows current to flow

27
Q

what are transformers and what do they do in a electrical circuit

A

transfers electrical energy from one circuit to another

used to step up/down the voltage from an AC power supply

28
Q

the coils in transformers are not connected so what transfers the power

A

magnetic field

As each turn creates a magnetic field

29
Q

for transformers the amount of current produced depends on what

A

Amount of current you produce depends how many coils on the wire there are

30
Q

more secondary turns in a transformer than primary turns means there is an increase/decrease in voltage

what has happened to the power

A

More turns on the right means there is an increase in voltage = steps up the power

Takes the energy and steps it up due to difference in number of turns

you can also do the opposite if needed

31
Q

what are the 3 circuits in a full x-ray circuit

A

Primary
filament
secondary

32
Q

what is the purpose of the primary circuit in the full x-ray circuit

A

Primary = control parameter and produce power,

33
Q

what is the purpose of the filament circuit in the full x-ray circuit

A

Filament circuit controls heating of filaments so release e-

34
Q

what is the purpose of the secondary circuit in the full x-ray circuit

A

Secondary circuit allows rectifying and flattening out the waveform

35
Q

what is Electromagnetic induction

A

a changing magnetic field induces an electrical potential difference (voltage) in a nearby conductor and also in which a voltage is induced in a conductor moving through a stationary magnetic field.

36
Q

in Electromagnetic induction the magnitude of the induced voltage is proportional to what factor

A

The magnitude of the induced voltage is proportional to the rate of change of the magnetic field strength.

37
Q

what are power ratings

A

The power rating of an x-ray tube or generator is the maximal power that an x-ray tube focal spot can accept or the generator can deliver.

38
Q

what is an anode heating chart

A

shows the anode heat loading for various input powers (kW or HU/s) as the x-ray tube is operating, taking into account the cooling that simultaneously occurs

39
Q

the anode cooling curve is steeper for larger/smaller anode heat capacities

A

With larger anode heat capacities, the anode cooling curve is steeper

40
Q

what does the primary circuit do in terms of the power

A

supplies power from the mains to the x-ray circuit

41
Q

why are circuit breaker included in the primary circuit

A

protect against short circuits and electric shocks

42
Q

what 2 things does the primary circuit control and what one factor does it monitor

A

controls tube voltage and exposure time

monitor tube voltage

43
Q

what are the 6 components of the primary circuit

A

power supply
mains power switch

circuit breaker

tube voltage selector
voltage meter

exposure timer

44
Q

what do auto transformers do in the primary circuit

A

allows selecting of different powers

45
Q

what are the 4 components of the secondary circuit

A

step-up transformers
rectifier
current meter
x-ray tube

46
Q

what does the secondary circuit monitor

A

tube current (mA)

only monitoring NOT setting it!

47
Q

what does the secondary circuit do in terms of the power type and voltage

A

convert AC to DC power

creates potential difference across the x-ray tube (for e- to accelerate)

step up voltage to voltage that is suitable for x-ray production

48
Q

how many diodes are in the secondary circuit

how many will let current through and how many wont

what do they allow the current to do

A

4

2 will, 2 wont

allow current to flow in a forward reaction

49
Q

there is a positive tube voltage when there is a ____ ___ ___

A

positive input voltage

50
Q

there is a negative tube voltage when there is a ____ ___ ___

A

negative input voltage

51
Q

what does the bridge rectifier in the secondary circuit produce in an AC circuit

what does this mean for the voltage

A

fully rectified waveform

negative voltage isn’t just removed, it’s also turned into a positive waveform

52
Q

what is the voltage ripple

how is it dealt with

A

Ripple = difference between highest and lowest point

Take maximum of each one that’s going out of phase, produce a lower ripple

53
Q

why do we need to reduce voltage ripple

A

get a higher quality x ray and higher average x ray that gets rid of lower energy and makes most of characteristic peaks

54
Q

what does the filament circuit control

how is this accomplished

A

controls the tube current (mA)

change resistance to change the current

55
Q

what 3 things does the filament circuit do in terms of the filament

A

selects the filament to be used

produces a current in the filament

initiate thermionic emission

56
Q

what % of energy is converted to x-rays

what is the rest converted to

A

1% = x-rays

99% = thermal energy (heat)

57
Q

what is the power rating in terms of the focal spot and the generator

A

max power that a x-ray tube focal spot can accept

max power that x-ray generator can deliver

202 MEDIMAGE (18 decks)

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