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Radiology > Introduction to Radiology > Flashcards

Introduction to Radiology Flashcards

1
Q

What are X-rays

A

X rays are a form of high energy electromagnetic radiation that can be produced in packets of energy called photons.

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2
Q

Name the different types of waves on the EMS from longest to shortest wavelength

A 
Radiowaves
Microwaves
Infra Red Waves
Visible light
Ultra violet rays
X rays (ionising)
Gamma rays (ionising)
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3
Q

What is ionising radiation

A

This is radiation that has enough energy to detach electrons from atoms and molecules

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4
Q

In which direction do x-rays travel

A

In a straight line

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5
Q

How are x-rays produced

A

High-speed energetic electrons bombard a target material and are brought suddenly to rest

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6
Q

What are the functions of the cathode and the anode in an x-ray tube

A

The cathode produces electrons

The anode acts as a target for electrons and converts the high energy electrons into x-ray photons

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7
Q

What happens in an x-ray tube

A
  1. the cathode filament is heated and electrons are emitted by the hot filament
  2. These electrons travel to the anode
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8
Q

What is the cathode filament made out of

A

Tungsten

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9
Q

What is tube current and how is it measured

A

Tube current is the flow of electrons from the cathode to the anode and is measured in milliamperes (mA)

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10
Q

Why is a high voltage used between the cathode and the anode

A

To accelerate the electrons to provide the energy needed to remove an electron from the K shell of a tungsten atom

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11
Q

What is the targets in the anode made from and why

A

It is a small piece of tungsten, which is set into the angled face of a large copper block

The copper is used to allow the efficient removal of heat

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12
Q

Why do we use a vacuum chamber in an x-ray tube

A

Air molecules would block or scatter the electrons away from the target

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13
Q

What are the two types of x-ray producing collisions with the tungsten atom

A

Continuous spectrum

Characteristic spectrum

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14
Q

What is continuous spectrum x-ray production

A

This is when the high-speed electrons collide with a tungsten atom and slow down and change direction as they interact with the positively charged nucleus and produce an x-ray as they lose this energy

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15
Q

What is the name of the radiation produced in continuous spectrum x-ray production

A

Breaking radiation (bremsstrahlung radiation)

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16
Q

How does characteristic spectrum x-ray production work

A

Electrons collide with the K-shell electrons (strongest binding) in tungsten and if the displace it or move it to another electron shell

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17
Q

What is the critical voltage in an x ray tube

A

69.5 KV

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18
Q

What is combined spectrum x ray production and when is it used

A

Combined = characteristic + continuous and is used when the x ray tube uses above 69.5 KV.

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19
Q

What is scattering in terms of radiology

A

This is a change in the direction of photons with or without the loss of energy

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20
Q

What is absorption in terms of radiology

A

This is the deposition of energy like removal of energy from an atom

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21
Q

What is attenuation in terms of radiology

A

This is a reduction in the intensity of the main x-ray beam caused by absorption and scattering

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22
Q

Name and describe the different types of interaction and x-ray can have with patient tissue

A
  1. Unmodified/Rayleigh Scattering - Pure scatter = scatter without change
  2. Photoelectric effect = pure absorption*
  3. Compton effect = scatter + absorption*
  4. Pair production = pure absorption
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23
Q

How is heat produced in the X ray tube

A

When electrons change direction by colliding with outer shell tungsten electrons lose energy and form heat

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24
Q

Why does heat need to be removed in an X ray tube

A

To prevent damage to the target

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25
Q

Name some uses of X rays in dentistry

A
  • Developing dentition
  • Caries Diagnosis
  • Periodontal assessment (bone level)
  • Endodontics
  • Trauma
  • Implants
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26
Q

What is radiation absorbed dose, name its units and what is used to measure it

A

This is the amount of energy absorbed from the radiation beam per unit mass of tissue it is measured in milligray (mGy)

measured using dosimeter

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27
Q

What is equivalent those and what are the units

A

This is the dose quantitiy for individual organs and is based on the absorbed dose to an organ
Unit = sievert (Sv)

28
Q

What is the calculation for equivalent dose (Ht)

A

radiation absorbed dose x radiation weighing factor (Wr) of a particular tissue

29
Q

What is the radiation weighing factor (Wr)

A

This represents the biological effects of different radiation on different tissues.
more absorption into the tissue = higher value.

30
Q

What is the radiation weightings factor (Wr) for x-rays, gamma rays and beta particles

A

1

31
Q

What is a tissue weighting factor (Wt)

A

This is a value assigned to each organ to represent how likely it is to be damaged by radiation, higher factor = higher risk

32
Q

How can age affect risk of radiation

A

Risk is reduced as you get older, when you are young the risk is much higher.

33
Q

What are the classifications of the potential biological effects of x-rays

A
  • somatic deterministic
  • somatic stochastic
  • genetic stochastic
34
Q

What are somatic deterministic effects

A

These are the damaging effects to the body that definitely results from a high specific dose of radiation
The higher the dose the more severe the effect and in most cases below a certain threshold dose there will be no effect

35
Q

What are somatic stochastic effects and gives some examples

A

These are effects that occur by chance and their development is random - leukaemia and certain tumours

36
Q

How can indirect damage occur from x rays

A

Water in cells are ionised and cause free radicals to form Hydrogen peroxide and hydroperoxyl that can damage DNA

37
Q

AY BAWS CAN I HABE DE NOTE PLZ

A

must be able to clinically justify the use of X rays

38
Q

What are the 4 techniques used to reduce x ray doses

A
  • Equipment
  • Clinical Decision
  • Practical Technique
  • Diagnostic Interpretation
39
Q

What is Aluminium Filtration used for in X rays

A

To remove harmful low energy x rays (soft x rays)

40
Q

Why are soft x rays harmful

A

they dont really pass through and get absorbed

41
Q

What is a collimator and what does it do

A

This is a metal barrier that has a hole that reduces the size and shape of x ray beam, it minimises scattered radiation, provides sharper image, less exposure innit

42
Q

What are the different types of collimator

A

Diaphragm, round, rectangular and slit,

rectangular is most effective at reducing radiation

43
Q

What are the 3 principles of radiology use defined by the International Commission on Radiological Protection (ICRP)

A
  1. Justification - availability and findings of previous radiographs, objectives of treatment, level of benefit to patient, alternative techniques
  2. Optimisation - all exposures kept as low as possible
  3. Limitation - equivalent dose shouldnt exceed limits recommended by the ICRP to protect, patients, radiation workers and general public
44
Q

How often should X ray tubes and all be checked

A

1-3 years

45
Q

What is a Beam Indicating Device (BID) and what is it used for

A

used for indicating the direction of the beam

setting ideal distance from focal spot on the target to skin

46
Q

What is a focusing device used for

A

Aims the stream of electrons at the focal point on the target

47
Q

Why is lead used in radiation protection

A

Has a high atomic number so the probability of photoelectric interactions is quite high

48
Q

What is the penumbra effect and how does it relate to X ray use

A

Means that the focal spot (source of the x rays) should be a single point source to reduce blurring of the image

49
Q

What is the voltage of the main supply to the tube voltage (KV)

A

240V

50
Q

How is the voltage of the main supply to the tube voltage (KV) altered in the X ray tube

A

Step up transformer = higher voltage to accelerate electrons = more compton effect, higher penetrating energy of photons, so less absorbed energy and less damage to tissue

Step down transformer= low voltage used to heat the filament

51
Q

What is film speed and what determines it

A

This is the sensitivity of the radiograph to radiation

  • size of the silver halide crystals
  • thickness of emulsion
  • presence of radiosensitive dyes
52
Q

What are the speeds of film categorised as and what is the fastest

A

D, E and F

F is the fastest

53
Q

How can digital imaging be used to reduce dose

A

Both types of digital image receptors are much more
efficient at recording photon energy than conventional
film.

54
Q

Gives an example of direct digital imaging

A
  • Sensor or imaging plate, replacing conventional film
55
Q

Give examples of indirect digital imaging and roughly how they work

A
  • Real time/corded CCD
  • Cordless, photostimulated phosphor plates (PSP)

scanning and digitalising a film captured image

56
Q

How do solid state sensors compare to PSP sensors and why do PSP sensors

A

solid stat sensors allow much more dose reduction as PSP sensors have a wide dynamic range (latitude), which can result in higher doses

57
Q

Should lead aprons be used routinely in dental radiography

A

no there is no justification and is positively discouraged

58
Q

How can pregnancy affect dental radiography

A

the associated risk is regarded as negligible but patient is given option of delaying radiography due to emotive nature

59
Q

What does IRMER stand for

A

Ionising Radiation (Medical Exposures) Regulations

60
Q

What is the role and duty of the referrer in X rays stufffs

A

A health professional is entitled to refer a patient for medical exposure and must supply sufficient info to justify an exposure

61
Q

What is the role and duty of the practitioner in X rays stufffs

A

Health professional entitled to take responsibility for a medical exposure

62
Q

What is the role and duty of the operator in X rays stufffs

A

Pratical element of medical exposure, exposure of radiograph and processing film

63
Q

What is the role and duty of the employer in X rays stufffs

A

Ultimate responsibility for a radiological installation

64
Q

Who should you notify if there is a radiograph equipment malfunction

A

Health and Safety office

65
Q

Who should you notify if there is a clinical error, error of judgement, operator error

A

IRMER inspectorate

Radiology (6 decks)

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