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Radiology! > The Production Of Xrays > Flashcards

The Production Of Xrays Flashcards

1
Q

The two types of transformer in the tube head are…?

A

1- step-up transformer

2- step-down transformer

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2
Q

What is the tube head composed made of and what is included in that (3 things)

A

Glass which has 1. Filament 2. Copper block 3. Target

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3
Q

What is the function of the step-up transformer

A

Steps up the mains voltage (240v) to the high voltage (kV) required across the X-ray tube

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4
Q

Step-down transformer function…

A

Step-down the mains voltage (240v) to the low voltage current (mA) required to heat the filament

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5
Q

The 5 main components of the X-ray tube

A 
1- the tube head 
2- the positioning arm 
3- the control panel 
4- circuitry 
5- the collimator (part of the tube head)
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6
Q

What is the function of the lead shield?

A

To minimise radiation leakage (may have an unleaded window though)

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7
Q

What is the function of oil in the tube head?

A

To facilitate heat removal

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8
Q

What metal is in the filter that removes the harmful low energy x-rays?

A

Aluminium

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9
Q

What does the collimator do?

A

Restricts the size and shape of the X-ray beam to a rectangle

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10
Q

Name a part of the collimator also known as a spacer cone?

A

BID - beam indicating device

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11
Q

What is the fsd?

A

Focus to skin distance

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12
Q

Above 60kV what is the ideal fsd?

A

200mm

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13
Q

Below 60kV what is the ideal fsd

A

100mm

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14
Q

1 quantum of energy = ?

A

1 photon

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15
Q

How many photons are in one x-ray beam?

A

Millions

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16
Q

You usually get (more/less) energy out than was put in

A

Less

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17
Q

1st step in the production of energy is…

A

Electricity on = vibration/excitation of electrons

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18
Q

What does electron excitation create?

A

A small current (8-10mA)

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19
Q

Where does the small current pass through and what happens?

A

Through the step-down transformer which alters the current

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20
Q

The altered current then …

A

Passes through the filament

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21
Q

How is the filament heated?

A

By the vibrating electrons

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22
Q

Name the type of filament in the x-Ray tube?

A

Tungsten

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23
Q

What does extreme excitation lead to?

A

The loss of electrons from the outer shell

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24
Q

What happens after electrons are lost from the outer shell?

A

The electron cloud of newly free electrons gather at the filament (giving it a -ve charge) making the filament a cathode

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25
Q

A large potential difference is between…

A

Th cathode (-ve) and anode (+ve)

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26
Q

What is the voltage change after passing though the step up transformer?

A

240v to 50-90kV

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27
Q

Name the important part on the cathode?

A

Focusing cup

28
Q

What is the important part on the anode?

A

Target point

29
Q

Where are the electron clouds at the cathode (tungsten filament) attracted to?

A

The positive anode

30
Q

When high energy electrons hit the target point on the anode they…(3 points)

A
  1. decelerate
  2. release 99% heat
  3. release 1% X-rays
31
Q

What happens to the heat released? 2 stages

A
  1. absorbed by the copper

2. dissipated into the oil

32
Q

what happens to the X-rays released? 2 things

A
  1. the anode directs the X-rays through the unleaded window

2. the leaded glass will absorb them (more than through unleaded window)

33
Q

Name the two spectrum that lead to X-ray producing collisions

A
  1. the continuous spectrum

2. the characteristic spectrum

34
Q

What is continuous spectrum?

A
  • breaking radiation giving WIDE RANGE of photon energies
35
Q

what is breaking radiation also known as?

A

bremsstrahlung radiation

36
Q

what is characteristic spectrum?

A
  • X-rays emitted by loss of electrons from K AND L shells
37
Q

Which spectrum of X-ray producing collins is used in dentistry?

A

the characteristic spectrum as energy levels in K AND L shells nicely produce the desired X-rays

38
Q

what is the characteristic spectrum dependant upon?

A

the type of material used in the anode.

39
Q

what is the most common material used in the anode in dentistry? and why?

A

tungsten because it can be pulled into a fine wire without breaking

40
Q

what happens when an outer electron is lost from the K shell (leaving it unstable)?

A

An outer electron from the L shell moves down leaving it unstable.

41
Q

Give 8 properties of X-rays.

A
  1. ionising (biological harm)
  2. travel in straight line in open space (even in vacuum where no air molecules present)
  3. X-ray photons form a divergent beam
  4. they are not detectable by human senses
  5. they produce a LATENT image on film EMULSION
  6. they cause certain salts to fluoresce and emit light
  7. they can be absorbed and scattered
  8. they penetrate matter (through)
42
Q

define scattering

A
  • random, unpredictable change in direction of X-rays after hitting something
  • can cause an issue with radioation protection as unpredictable
43
Q

define absorption

A

deposition of ENERGY in tissues

44
Q

define intensity

A

the NUMBER of X-ray photons in a DEFINED AREA of the beam

45
Q

define attenuation

A

the REDUCTION in the INTENSITY of a beam

46
Q

what can cause attenuation? 2 things

A

-scattering & absorption

47
Q

define ionisation

A

the removal of an electron from a NEUTRAL ATOM to give a NEGATIVE ION and a POSITIVE ION

48
Q

give a positive and a negative of ionisation

A 
positive = required to produce and image 
negative = can be harmful to lining tissues
49
Q

define penetration

A

the ability of photons to pass THROUGH or INTO tissues

50
Q

give the 4 possible interactions of the X-ray beam

A
  1. completely scattered (no loss of energy)
  2. scattered (some absorption and energy lost)
  3. absorbed (total loss of energy)
  4. transmitted unchanged
51
Q

what is the photo electric effect?

A

where you have pure absorption of X-rays and a total loss of energy at an atomic level

52
Q

what is the first stage in the photo electric effect?

A

incoming X-rays interacts with the K shell (INNER shell)

53
Q

what is the 2nd stage in the photo electric effect?

A

an electron is ejected from the K shell with HIGH energy (now it is called a photo electron)

54
Q

what happens to the X-ray photon during this 2nd stage?

A

it is totally absorbed and has deposited all its energy

55
Q

what is the 3rd stage in the photo electric effect? and what is given out during this stage

A
  • outer shell electron cascade to try and stabilise the the inner shell
  • excess very low radiation is given out - light
56
Q

what does the ejected photo electron act like?

A

the initial high energy X-ray photon - initiates the ejection of other electrons as it passes through the tissues

57
Q

what is responsible for the ionising interactions in the tissues?

A

the high energy electrons being ejected

58
Q

how is atomic stability achieved in both the photoelectric effect and the compton effect?

A

a free electron will join the outer shell

59
Q

what is the compton effect?

A

where you have scatter radiation and absorption at an atomic level

60
Q

what is the first stage of the compton effect?

A

incoming X-ray photon interacts with loosely bound, OUTER shell electron

61
Q

the 2nd stage in the compton effect is..?

A

where the electron is ejected with SOME energy of the X-ray photon and is now called the compton recoil electron

62
Q

what happens to the X-ray photon during this stage of the compton effect?

A

it is scattered from it’s original path as a scattered photon. This can still cause ionisation as it still has energy

63
Q

what does the compton recoil electron cause?

A

ionisation in the tissues.

64
Q

what can the compton recoil electron undergo?

A

further cotton reaction or photoelectric reactions

65
Q

give another name for being fully scattered with no energy loss

A

the rayleigh (unmodified) scattering

66
Q

what is responsible for producing contrast between tissues?

A

the photo-electric effect

Radiology! (10 decks)

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