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Radiology > Radiation doses atc > Flashcards

Radiation doses atc Flashcards

1
Q

What is the approximate radiation does for a extra-oral DPT?

A

0.02 mSv

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2
Q

When were xrays first developed?

A

1895 by Roentgen

Edmund Kells took the first dental xray in 1896

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3
Q

Which radiation legislation do us as dentists use?

A

Ionising Radiation Regulations (IRR) 1999

Ionising Radiation Medical Exposure Regulation (IRMER) 2000

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4
Q

What does the IRR (ionising radiation regulation 1999) relate to?

A

It relates to the workplace and employees

It provides a framework for ensuring that exposure to ionising radiation arising from work activities, is kept as low as reasonably practical and does not exceed specific limits

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5
Q

What is IRMER 2000?

A

A document aimed towards patient protection

Minimies risks to patients undergoing medical exposures

It is enforced by the CQC England and the Healthcare inspectorate Wales

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6
Q

What 4 classes of duty holder does IRMER 2000 define?

A

Employer (legal person)

Referrer

Practioner

Operator

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7
Q

Who is the referrer?

A

An authorised person that requests the radiograph

The referrer has to perform an adequate history and examination and provide sufficient details regarding the clinical exposure to enable the practictioner or operator to justify the procedure

SUPPLY CLINICAL DETAILS TO ALLOW JUSTIFICATION

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8
Q

What is the function of the practitioner?

A

TO JUSTIFY THE PROCEDURE

do the benefits outweigh the risks?

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9
Q

Who is responsible for justifying the radiological procedure?

A

Practitioner

is the radiogrpah going to change the way that you manage the patient?

JUSTIFICATION SHOULD BE RECORDED IN THE PATIENT NOTES

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10
Q

What is meant by the term authorisation?

A

Recording that justification has been carried out prior to the exposure

(medico-legal exposures must be authorised by the dentist)

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11
Q

What is the function of the operator?

A

OPTIMISATION OF ALARA

identify the patient, position the tube head, set the exposure, develop the film, evaluate the film

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12
Q

How do you keep doses of radiation as low as possible to patients?

A

Justify the radigraph

use collomators

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13
Q

What is the dose limit for patients?

A

There is no written dose limit

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14
Q

What is the role of the IRMER Employer?

A

They have legal responsibilities to apply IRR and IRMER

they need to be suitably trained and know the dose limits and be able to carry out risk assessments

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15
Q

What does HSE stand for?

A

Health and saftey executive

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16
Q

When (in terms of radiography) will a dental practitioner need to contact the HSE?

A

When they want to take radiographs and would like to install equiptment

when there is new ownership of a practice or change of address

THE HSE DO NOT NEED TO BE CONTACTED WHEN EQUIPTMENT IS CHANGED OR RENEWED

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17
Q

Who is responsible for contacting the HSE?

A

The IRMER Employer

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18
Q

What is the HSE 5 step approach to risk assessment?

A
  1. Identify the hazards
  2. decide who might be harmed and how they might be protected
  3. evaluate the risks- protective measures
  4. record the findings
  5. review and revise the risk assessment.
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19
Q

Give 5 duties of the Employer

A

Undertake risk assessments

notify the HSE when required

ensure all neccessary systems are in place

establish a Quality Assurance programme (QA)

Ensure that written protocols are in place for every type of radiological exposure

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20
Q

What is the role of the medical physics expert?

A

To provide adive on:

  1. Patient dosage
  2. development and use of new and/or complex techniques
  3. other matters realting to radioation exposures for dental procedures
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21
Q

True of false

Each dental practice must have a Radiation Protection Advisor (RPA)

A

TRUE

The appointment must be in writing (IRR 1999)

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22
Q

What is the role of the Radiation Protection Advisor (RPA)?

A

Safety management

training

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23
Q

What does RPS stand for and what is their responsibility?

A

Radiation protection supervisor ( IRR 1999)

Each practice needs one. It is usually a dentist but can be a dental nurse

They ensure that the necessary rules are followed

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24
Q

What is a DRL?

A

A diagnostic reference level

ie the doses for typical examinations of the average sized patient

this information is usally displayed next to the xray machine

EMPLOYERS MUST TAKE ACTION IF THESE ARE EXCEEDED

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25
Q

When do you have to report an over exposure?

A

When a patient is perceived to have 20x the intended dose

The RPA must be contacted and the patient should be informed of the incident

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26
Q

What is the atomic mass of an atom?

A

The total number of protons and neutrons in an atom

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27
Q

What is the mass of an electron?

A

1/1840

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28
Q

What is the atomic number

A

The number of protons in an atom

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29
Q

If an atom is exctied, what happens to the electron?

A

It moves from an inner shell to an outer shell. Ie the electron moves to a higher energy level

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30
Q

What is the binding energy?

A

The energy required to overcome the attraction and remove an electron from an atom. The binding eneergy is greatest for the electron in the K shell, ie the one closest to the nucleus.

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31
Q

What is ionisation?

A

The removal of one or more electrons from an atom, giving it a positive charge

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32
Q

What is an xray?

A

Xrays are descibed as wave packets of energy. Each packet is called a photon.

Xrays are a form of electromagnetic radiation

Dental xrays are made up of millions of photons

33
Q

TRUE OR FALSE

XRAYS are a type of ionising radiation?

A

TRUE

34
Q

What is the greatest source of ionising radiation?

A

RADON

35
Q

Give 5 properties of Xrays

A
  1. They travel in straight lines
  2. They are invidible and weightless
  3. They travel at the speed of light in a vacuum
  4. They obey the inverse square law
  5. They have a range of wavelengths from 0.01-0.05 nm
36
Q

How do you produce Xrays

A

This needs to be done in a vacuum to prevent collision with other atoms

1. produce lots of electons

  1. accelerate them to a very high energy
  2. smash them into a target without destroying it
37
Q

What are the main components of the tubehead?

A
  1. Glass xray tube (filament, copper block and target)
  2. stepdown transformer
  3. step up transformer
  4. lead casing
  5. Oil
  6. Aluminium filtration
  7. Collimator
  8. Beam indicating device
38
Q

What charge is the anode and cathode?

A

Anode is positive

Cathode is negative

39
Q

How are xrays produced in the tubehead?

A
  1. Electrons are produced as the filament heats, thermionic emission - Cathode)
  2. The elctrons are accelerated towards the anode ny a high potential difference (kV)
  3. Rapid deceleration of the electrons as they hit the tungesten target
  4. As the electrons collide, the energy is converted as heat (99%) or xrays (1%)
  5. The heat is removed and dissipated by the oil and they copper block
40
Q

What is the relevance of kV, mA and Secs on a dental xray machine?

A

**kV - **Determines the quality of the xray beam, ie the energy of the photons. it affects their penetration and so the contrast of the film

**mA and time - **determines the quantity of the xray photons. Affects the degree of blackening of the film

41
Q

What are the two methods by which xrays can be produced?

A
  1. Bremsstrahlung Radiation
  2. Characteristic radiation
42
Q

What are the 3 components of a dental x ray set up?

A

Tubehead

positioning arms

control panel and circuitary

43
Q

What is the importance of the aluminium filtration in the tubehead?

A

It removed low energy photons and reduces the radiation dose to the patient

44
Q

What is the purpose of the rectangular collimator?

A

Tries to match the beam size to the image receptor size in order to reduce the dose to the patient

a rectangular collimator reduces the dose to the patient by 50%

45
Q

What are the advantages of a constant potential?

A
  1. Xray production per unit time is more efficient
  2. More high energy photons per exposure
  3. fewer low energy harmful photons are produced
  4. shorter exposure times
46
Q

What is the benefit of a beam indicating device?

A

it is a 20cm long cone

It produces a near parallel beam and so reduces any magnification and there is a less irradiated area

47
Q

What are the 2 types of conventional image receptors?

A
  1. Direct action film - the xray photons interact with the film
  2. Indirect action films - the photons interact with an intensifying screen which produces light that ineracts with the film
48
Q

What are the components of a film packets?

A
  1. Black paper
  2. Lead foil
  3. Moisture resistant outer cover
  4. Film
49
Q

TRUE OR FALSE

The intra oral xray film has one side coated with emulsion

A

FALSE

both sides are coated with an emulsion

50
Q

What is the composition and purpose of the emulsion on the film?

A

90% silver halide crystals in a gelatin matrix

10% silver iodo-bromide (increases sensitivity)

x-ray or light photons, sensitize the silver-halide crystals that they strike, forming a latent image

51
Q

What is meant by the film speed?

A

The amour of exposure a film needs to produce an optical density of 0.1 above the background fog

The faster the film speed, the less exposure required and the smaller the dose to the patient

52
Q

What film speed for we use at the BDH and how does that compare to digital radiographs?

A

F speed

Digital dose is 50% less that than of F speed

53
Q

What determines the film speed?

A

The number and the size of the silver halide ions

the larger the crystals, the faster the film speed, although there will be some loss in quality

WE SHOULD USE THE FASTEST FILM ALONG WITH ONE THAT WILL PROVIDE ADEQUATE DIAGNOSTIC RESULTS

54
Q

What do extra-oral cassettes consist of?

A

contain a film sandwiches between two light intensifying screens

the cassette itself is made from light-tight aluminium or carbon fibre

55
Q

How do intensifying screens reduce patient does to ionising radiation?

A

One x-ray photon produces many light photons

fewer xray photons are therfore needed to produce an image

patient dose is reduced at the expense of resolution

56
Q

What is meant by image resolution?

A

The ability to differentiate between different stuctures that are close together on the radiograph

DRIECT ACTION FILM RESOLUTION - approximately 10 line paris per mm

INDIRECT ACTION FILM RESOLUTION - approximately 5 line pairs per mm

57
Q

How can a film become overexposed in a developer?

A

if it in there for too long

it the temperature of the solution is too hot

If the developing solution is too strong

58
Q

(a) What pH is the developing solution?
(b) how often should it be changed?
(c) what happens if it is too old?

A

10.5

every 14 days

film is too pale and underdeveloped

59
Q

What are the 4 stages when developing a film?

A
  1. Development ( the developing solution hads a pH of 10.5)
  2. Fixation (the fix is acidic pH 4.0-4.5)
  3. Washing - to remove any residula fixer. If fixer is retained the film becomes stained brown
  4. Drying
60
Q

What fo fixer and developer splashes look like on a film fault?

A

Fixer - White dots

Developer - dark black dots

61
Q

What is meant by justification?

A

Is taking the radiograph going to change the diagnosis and management of the patient

62
Q

When might we take a dental radiograph?

A
  1. pathology affecting a tooth +/- supporting tissues
  2. detecting caries
  3. teeth present
  4. assessing root morphology
  5. localisation of foregin bodies
63
Q

Which type of intr-oral radiographs might we take?

A

Bitewings (hoizontal and vertical)

PAs

Occlusal

64
Q

What extra-oral radiographs might we take?

A

DPT

Lateral ceph

lateral oblique

65
Q

Why might we take bitewings?

A

caries detection

monitor caries/ previous restorations

assessment of periodontal status (vertical bitewings for pockets ~6mm)

66
Q

Why would you take bitewings for caries diagnosis?

A

bitewings have a diagnositc yield 4x greater than clinical diagnosis for interproximal caries

However, 50% demineralisation is required before you can visualise caries on a radiograph

67
Q

Does a low kV give you a better or worse contrast?

A

Better (good for caries diagnosis)

A high kV is better for looking at bone levels eg for perio

68
Q

How often should you take posterior bitewings for caries diagnosis?

A

High risk - 6 months

Moderate risk - annually

Low risk - 24 months in the permanent dentition

12-18 months in the decidous dentition

69
Q

What 2 tecniques are there for taking a pericapiacal radiograph?

A

long cone Parralleling technique

bisecting angle

70
Q

What might you take a periapical?

A

Assess root morphology

assess periaplic infection

Extent of crown pathology in anterior teeth

Assessment of local anatomy, including tooth development

71
Q

Why would you take periapical radiographs for periodontal disease?

A

Determine the severity through bone loss and furcation involvement

to identify any causative factors e.g calculus

to evaluate treatment and assist in other treatment planning

72
Q

When might you take horizontal bitewings for periodontal diagnosis?

A

When there is uniform pocketing <6mm with little or no recession

73
Q

When might you retake a radiographs during endodontic treatment?

A

if the apex has been missed

if the master file/GP point is >2mm from the apex

74
Q

How many years after completion, may you want to retake an radiograph following endodontic treatment?

A

1 year

4 years

FOR ASYMPTOMATIC TEETH

75
Q

When would you take a radiograph for trauma?

A

A baseline radiograoh is manditory following all but minor tooth trauma

76
Q

When would you take a DPT

A
  1. Prior to surgery under GA e,g odontome
  2. Where a boney lesion or unerupted tooth is of a size or positions which precludes complete demonstration on an intra-oral film
  3. ortho/implant assessment
77
Q

What is the taken for severe TMJDS?

A

MRI

78
Q

Why would you take a lateral ceph?

A

Look at the skeletal pattern

to look at the incisal angulation

orthognathic surgical planning

Radiology (2 decks)

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