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Science and Technology 1 > X-ray Beam Production > Flashcards

X-ray Beam Production Flashcards

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Biology 101 flashcards
1
Q

What happens during excitation?
(3)

A

Energy is transferred to an orbiting electron

The electron jumps from lower to higher energy levels

The atom becomes excited

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2
Q

What happens during ionisation?
(3)

A

Energy is transferred to an orbiting electron

The electron is removed from the electric field of the nucleus

The atom is ionised

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3
Q

What causes heating?

A

When an electric current runs through a wire.

More current=more heat=more electrons=more interactions

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4
Q

What is thermionic emission?

A

The release of electrons due to heat.

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5
Q

What are the 2 processes that produce x-rays?

A

Characteristic x-rays

Bremsstrahlung

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6
Q

What happens in characteristic x-rays to produce x-rays?
(6)

A

Electrons crash into the target material, hoping that they’ll hit some orbito (inner) electrons in the target material

When they collide, it causes a vacancy

The atom becomes unstable

The inner shell wants to fill the vacancy, as they only have 1 electron instead of 2

In order to replace the electron, characteristic x-rays are produced, which stabilises the atom

These x-rays use the outer electron to replace the inner electron. The change of energy causes photon x-rays

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7
Q

How do auger electrons come about?

A

After the inner shell vacancy is filled by characteristic x-rays, it’s possible for an outer shell electron to be ejected instead of a photon- this emitted electron is an Auger electron

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8
Q

How many times smaller is the nucleus compared to an atom?

A

The nucleus is 10 000x smaller than the atom

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9
Q

What charge does the nucleus have?

A

Positive charge (+)

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10
Q

What charge do electrons have?

A

Negative charge (-)

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11
Q

How does Bremsstrahlung radiation produce x-rays?
(4)

A

The electron interacts with the nucleus of the target material (rather than colliding with inner electrons like in characteristic x-rays)

The electron loses (kinetic) energy and slows down

The electron changes path

The release in energy causes the release of photon energy

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12
Q

What type of photon is produced during Bremsstrahlung when the electron loses lots of energy?

A

A high energy photon

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13
Q

What type of photon is produced during Bremsstrahlung when the electron loses a little bit of energy?

A

A low energy photon

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14
Q

When the electron collides directly with the nucleus during Bremsstrahlung, how much energy does it lose?

A

All its energy

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15
Q

What is kVp?

A

The peak voltage

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16
Q

What determines whether we get characteristic x-rays or not?

A

The changing energy in the x-ray tube, which changes the maximum energy of electrons

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17
Q

Why are filters needed?

A

To remove low energy x-rays because they get absorbed by the patient but don’t contribute to the image. This contributes to radiation dose

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18
Q

What does attenuated mean?

A

Absorbed

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19
Q

What type of energy radiation is more likely to be attenuated/absorbed?

A

Low energy radiation

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20
Q

When would we see a greater change in radiation?

A

When the radiation is passing through more material in the low energy part of the spectrum

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21
Q

What is beam hardening?

A

When the average energy of the beam increases

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22
Q

What does a change in quantity mean?

A

The distribution of energies stays the same, but the number of photons change

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23
Q

How can we change the quantity?

A

By changing the mAs of the tube, e.g. running more current in the filament to cause more interactions

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24
Q

What does a change in quality mean?

A

The distribution of energies changes as well as a change in the whole number of energies

25
Q

How can we change the quality?

A

By changing the kV of the tube, e.g. providing more energy to the electrons causing the x-ray production

26
Q

What does changing the quality result in?

A

A change to the shape and height of the spectra

27
Q

What does the material in an x-ray tube have to be able to do?

A

Withstand heat

28
Q

What does the filament in an x-ray tube have to be able to do?

A

Sustain/tolerate high amounts of thermionic emission

29
Q

What does the target in an x-ray tube have to be able to do?
(2)

A

Dissipate heat

Produce x-rays in the desired energy range

30
Q

What does the housing do in the x-ray tube?

A

It shields the undesired x-rays

31
Q

In which direction are x-rays produced in?

A

All directions

32
Q

What does the window in an x-ray tube do?
(2)

A

It allows the x-rays to go in the desired direction

It contributes to inherent filteration

33
Q

What is the focal point?

A

An area of the target which leads to blurring but allows better heat dissipation

34
Q

What do physical limitations of the focal point cause?

A

They cause blurring, but allows for better heat dissipation

35
Q

What is the focal point size controlled by?
(2)

A

The focusing cup

Filament size

36
Q

What does a small focal point do to the unsharpness?

A

It causes a smaller amount of unsharpness

37
Q

What is unsharpness?

A

A shadow

38
Q

What’s good about having a small focal point?

A

There’s a smaller amount of unsharpness (shadow), so there’s a higher resolution of the image.

39
Q

When can a small focal point be used?

A

When using small amounts of energy

40
Q

What does a larger focal point do the unsharpness?

A

There’s higher amounts of unsharpness

41
Q

Why are larger focal pints worse?

A

They cause higher amounts of unsharpness, which causes a lower resolution of the image

42
Q

When can a larger focal point be used?

A

When using big amounts of energy

43
Q

How can we minimise unsharpness?
(2)

A

Put the detector close to the patient

Use the smallest focal spot size you can

44
Q

What happens if the area of the target material being hit is wider?
(3)

A

More electrons hit more of the target material

More heat is dissipated over a larger area

This causes more unsharpness

45
Q

What does a large focal spot size allow us to do to the anode?

A

It allows us to put more hat into the anode without damaging it

46
Q

What does increasing the anode angle do?
(4)

A

It results in a less steep slope facing the filament

It increases focal spot size, which reduces the resolution and increases the unsharpness

It improves heat loading

It increases the field coverage

47
Q

What does the anode heel mean?

A

It’s the idea that when x-rays are produced, electrons will be emitted at different angles. The electrons that pass through more of the target material will have less energy, and the electrons that pass through less of the target material will have more energy

48
Q

Where dos attenuation occur?

A

In the target material

49
Q

What does a longer path within the anode do to the attenuation?

A

It increases attenuation

50
Q

Where is the anode heel effect useful in radiography?

A

In mammography

51
Q

What is the anode heel impacted by?

A

The anode angle

52
Q

What does the anode heel cause?

A

It causes different intensities of photons across the x-ray field

53
Q

What minimises/eliminates the effect of the anode heel?

A

Digital corrections

54
Q

Why is the anode heel useful in mammography?

A

Because in mammography, we expect a difference in anatomy thickness across the x-ray field

55
Q

What does a larger anode angle do to the anode heel effect?

A

It reduces the anode heel’s effect

56
Q

What does the x-ray spectra depend on?
(3)

A

Accelerating voltage

Target material

Window material

57
Q

Where is the advanced tube design used?

A

In mammography

58
Q

What does the advanced tube design say?

A

It says that the adjustment (change) of both the target material and the tube window can cause changes in very different x-ray spectra

Science and Technology 1 (17 decks)

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