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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
A large potential difference is between...
Th cathode (-ve) and anode (+ve)
26
What is the voltage change after passing though the step up transformer?
240v to 50-90kV
27
Name the important part on the cathode?
Focusing cup
28
What is the important part on the anode?
Target point
29
Where are the electron clouds at the cathode (tungsten filament) attracted to?
The positive anode
30
When high energy electrons hit the target point on the anode they...(3 points)
1. decelerate 2. release 99% heat 3. release 1% X-rays
31
What happens to the heat released? 2 stages
1. absorbed by the copper | 2. dissipated into the oil
32
what happens to the X-rays released? 2 things
1. the anode directs the X-rays through the unleaded window | 2. the leaded glass will absorb them (more than through unleaded window)
33
Name the two spectrum that lead to X-ray producing collisions
1. the continuous spectrum | 2. the characteristic spectrum
34
What is continuous spectrum?
- breaking radiation giving WIDE RANGE of photon energies
35
what is breaking radiation also known as?
bremsstrahlung radiation
36
what is characteristic spectrum?
- X-rays emitted by loss of electrons from K AND L shells
37
Which spectrum of X-ray producing collins is used in dentistry?
the characteristic spectrum as energy levels in K AND L shells nicely produce the desired X-rays
38
what is the characteristic spectrum dependant upon?
the type of material used in the anode.
39
what is the most common material used in the anode in dentistry? and why?
tungsten because it can be pulled into a fine wire without breaking
40
what happens when an outer electron is lost from the K shell (leaving it unstable)?
An outer electron from the L shell moves down leaving it unstable.
41
Give 8 properties of X-rays.
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
define scattering
- random, unpredictable change in direction of X-rays after hitting something - can cause an issue with radioation protection as unpredictable
43
define absorption
deposition of ENERGY in tissues
44
define intensity
the NUMBER of X-ray photons in a DEFINED AREA of the beam
45
define attenuation
the REDUCTION in the INTENSITY of a beam
46
what can cause attenuation? 2 things
-scattering & absorption
47
define ionisation
the removal of an electron from a NEUTRAL ATOM to give a NEGATIVE ION and a POSITIVE ION
48
give a positive and a negative of ionisation
``` positive = required to produce and image negative = can be harmful to lining tissues ```
49
define penetration
the ability of photons to pass THROUGH or INTO tissues
50
give the 4 possible interactions of the X-ray beam
1. completely scattered (no loss of energy) 2. scattered (some absorption and energy lost) 3. absorbed (total loss of energy) 4. transmitted unchanged
51
what is the photo electric effect?
where you have pure absorption of X-rays and a total loss of energy at an atomic level
52
what is the first stage in the photo electric effect?
incoming X-rays interacts with the K shell (INNER shell)
53
what is the 2nd stage in the photo electric effect?
an electron is ejected from the K shell with HIGH energy (now it is called a photo electron)
54
what happens to the X-ray photon during this 2nd stage?
it is totally absorbed and has deposited all its energy
55
what is the 3rd stage in the photo electric effect? and what is given out during this stage
- outer shell electron cascade to try and stabilise the the inner shell - excess very low radiation is given out - light
56
what does the ejected photo electron act like?
the initial high energy X-ray photon - initiates the ejection of other electrons as it passes through the tissues
57
what is responsible for the ionising interactions in the tissues?
the high energy electrons being ejected
58
how is atomic stability achieved in both the photoelectric effect and the compton effect?
a free electron will join the outer shell
59
what is the compton effect?
where you have scatter radiation and absorption at an atomic level
60
what is the first stage of the compton effect?
incoming X-ray photon interacts with loosely bound, OUTER shell electron
61
the 2nd stage in the compton effect is..?
where the electron is ejected with SOME energy of the X-ray photon and is now called the compton recoil electron
62
what happens to the X-ray photon during this stage of the compton effect?
it is scattered from it's original path as a scattered photon. This can still cause ionisation as it still has energy
63
what does the compton recoil electron cause?
ionisation in the tissues.
64
what can the compton recoil electron undergo?
further cotton reaction or photoelectric reactions
65
give another name for being fully scattered with no energy loss
the rayleigh (unmodified) scattering
66
what is responsible for producing contrast between tissues?
the photo-electric effect

Radiology! (10 decks)

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