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Radiology > X-ray machines > Flashcards

X-ray machines Flashcards

1
Q

what is contained within the negative cathode?

A

filament

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2
Q

what is contained within the positive anode?

A

tungsten target

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3
Q

how do you heat up a cathode?

A

pass a current through it

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4
Q

what happens when you heat a cathode?

A

e- in outer shell gets enough energy to escape (emits e-)

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5
Q

Where is the focusing cup located?

A

negative cathode

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6
Q

How is an x-ray formed?

A

hitting target

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7
Q

what does the negative focusing cup do?

A

focuses e- into a narrow beam toward anode (e- don’t diffuse away)

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8
Q

where is the tungsten target located?

A

copper stem in anode

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9
Q

what is the function of tungsten target?

A

converts kinetic energy of colliding e- into x-ray photons

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10
Q

what is the function of the copper stem?

A

dissipates heat produced

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11
Q

Once e- hits target, most of the energy is converted to –

A

heat (>99%)

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12
Q

Once e- hits target, some of the energy is converted into –

A

x-rays (1%)

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13
Q

increase likelihood that e- hits target by – (e- move towards target faster)

A

high potential difference between cathode and anode (70 kwatts)

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14
Q

x-rays are – by calcified tissues (bones)

A

blocked

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15
Q

x-rays are – by soft tissues

A

absorbed

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16
Q

clearer images from a – source of radiation

A

point (small)

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17
Q

umbra =

A

sharp

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18
Q

penumbra =

A

fuzzy

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19
Q

focal spot size of dental x-ray tubes

A

0.4 to 0.7 mm

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20
Q

what kind of anode is mostly used?

A

stationary

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21
Q

why do you angle target?

A

seemingly smaller source of radiation –> clearer image

22
Q

unlike visible light, x-rays are not –

A

reflected (produce at 360 degrees)

23
Q

How does a rotating anode decrease heat buildup at the anode?

A

e- hit a different surface on anode

24
Q

panoramic, CT, and cone-beam use what kind of anode?

A

rotating

25
Q

best to use – anode for radiographs that have extended time periods

A

rotating

26
Q

rotating anodes make x-rays from a – point

A

narrow

27
Q

describe energy x-ray photons

A

broad spectrum of energy

28
Q

e- attracted to positive nucleus in anode but the orbiting e- forces the incoming e- to –

A

deviate

29
Q

e- that hit closer to the nucleus give off – energy

A

more

30
Q

All x-ray photons produced are not monoenergetic describes – radiation

A

Bremsstrahlung

31
Q

x-ray photons with discrete energies describes – radiation

A

characteristic

32
Q

describe e- movement in characteristic radiation

A

incoming e- collides with e- in orbit
outer shell moves in
inner shell is lost

33
Q

the difference between the outer and inner shell of a characteristic radiation has – energy

A

discrete

34
Q

Ideal range of photon energy that can be blocked by bone but not tissue

A

20-50 keV

35
Q

How can you control the energy produced?

A 
milliamperage (mA)
exposure time (seconds)
peak kilovoltage (kVp)
36
Q

What is mA

A

how much current goes thru filament

37
Q

What happens when you heat filament more?

A

more electrons produced/liberated –> more x-ray photons

38
Q

How long is the general exposure time?

A

0.1-0.4 seconds

39
Q

What happens when you increase the kVp (diff b/t cathode and anode)?

A

more electrons produced –> more photons

40
Q

How can you increase mA?

A

heat filament more

41
Q

What happens when you double mA?

A

double photons but same energy (keV)

42
Q

Why is it better to increase mA than exposure time to get more photons?

A

same radiation but lower patient movement

43
Q

Adjusting kilovolt (peak) depends on –

A

size of object (hand vs skull)

44
Q

What influences both energy and number of photons?

A

kVp

45
Q

How should you adjust kVP if it’s the same amount of bone but less calcified?

A

lower kVp

46
Q

describe useful energy

A

sufficient energy to penetrate tissue and reach film (cause some ionization but w/o these there’s no image)

47
Q

What is the function of Al filter?

A

removes low energy photons

48
Q

describe low energy photons

A

absorbed by tissue (damaging) and no image

49
Q

What is the function of collimation?

A

limit radiation beam to examined region

50
Q

what does collimation reduce?

A

radiation exposure and scatter radiation

51
Q

inverse square law

A

beam intensity is inversely proportional to square of distance from radiation source

Radiology (6 decks)

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