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5th Yr - CP5- IRMER > dose reduction > Flashcards

dose reduction Flashcards

1
Q

What are the 3 things we need to consider to protect the patients from radiation

A
  1. Risk associated with radiation exposure
  2. Level of risk
  3. The acceptability of the risk
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2
Q

What are the 3 core principles for protecting patients from ionising radiation

A
  1. Justification
  2. Optimisation
  3. Limitation
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3
Q

What do we mean by justification

A

there must be a net benefit of the procedure to the patient

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4
Q

What is the justification for radiogrpahs

A

Normally provides new information to aid patients management

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5
Q

What is the principle of justification for radiographs based on

A

Evidence based selection criteria

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6
Q

What do mean by optimisation

A

Technique and getting the radiograph right first time

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7
Q

We keep doses ALARP what does ALARP stand for

A

As
Low
As
Reasonably
Practicable

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8
Q

What do we mean by limitation

A

Dose limits should not be excessed for workers and the public

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9
Q

Is there a dose limit for patients?

A

No instead justification protects patients from clinically un warranted examination

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10
Q

What factors fall under optimisation

A
  1. Equipment factors
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11
Q

When looking at intra oral radiography what do we consider to assess optimisation

A
  1. Method of x ray generation
  2. Kilovoltage
  3. Filtration
  4. Colimation
  5. Cone length
  6. Image receptor
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12
Q

What are the different methods of x ray generation

A

Constant potential
Direct current waveform

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13
Q

What do we mean by direct current waveform

A

The kildovoltafge is kept at its peak throughout the exposure so production of x stays is more efficient

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14
Q

Describe the energy produced by direct current waveforms

A

More high energy useful x ray photos are produced and few low energy harmful x rays are produced
more effeicnt

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15
Q

Describe the energy produced by direct current waveforms

A

More high energy useful x ray photos are produced and few low energy harmful x rays are produced
more efficient

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16
Q

Which do we want more high or low energy photons

A

High energy

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17
Q

Why do we not want as many low energy photons

A

As they are scattered and cause harm to patient

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18
Q

Do modern x ray sets use Constant potential or Direct current waveform

A

Direct current

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19
Q

What do direct current waveform x rays machines allow for

A
  1. Eliminated the filament warm up time from exposure time
  2. More efficient production of photons which contribute to the image
  3. Allows for Digital equipment
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20
Q

What kilovoltage should new x ray equipments operate at

A

60-70kV

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21
Q

What happens at lower kV values

A

The photoelectric effect predominates which is pure absorption due to low energy photons
this can increase damage to patients

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22
Q

What does a high kV value result in

A

Lower dose and lower contrast

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23
Q

What factors influence the exposure time

A
  1. What needs to be x rayed
  2. Child vs adult
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24
Q

What does filtration do

A

Removes low energy photons which contribute most to dose

25
Q

How much filtration should we have for an x ray machine running at up to and including 70 kV

A

1.5mm aluminium

26
Q

How much filtration should we have for an x ray machine running greater than 70 kV

A

2.5mm aluminium

27
Q

What are the benefits of a rectangular collimator

A

Shapes and limits the beams size
Can reduce the dose by 50% compared to circular collimation

28
Q

When should rectangular collimation be used

A

For ALL:
1. Periapicals
2. Bitewings
3. Occlusal radiographs

29
Q

What does the spacer Cone determine

A

The distance between the point at which the x ray beam is generated and the point at which the x ray beam exits the collimator to the patients

30
Q

What does a longer spacer cone result in

A
  1. Improved image quality
  2. Reduced patient dose
31
Q

What does FSD stand for

A

focal spot to skin distance

32
Q

What FSD should the spacer cone give

A

A focal spot to skin distance (FSD) of at least 20cm

33
Q

Where should the end of the spacer Coen be in relation to the patient

A

As close the patients skin as possible without touching it

34
Q

What concept governs the effect of the spacer cone length

A

Inverse square law

35
Q

What does the inverse square law state

A

Beam intensity reduces by the increase in distance squared (intensity= 1/d^2)

36
Q

What does the inverse square law mean in lay terms

A

Doubling the distance of a spacer cone reduces the intensity by factor 4

37
Q

Which image receptor should we select

A

The fastest available system compatible with a satisfactory diagnostic result should be selected

38
Q

Which film should we use

A
  1. Fastes available S speed or E speed
  2. F speed 20% faster than E speed
  3. D Speed speed should no longer be used
39
Q

Name the different speed film

A

D speed film
E speed film
F speed film

40
Q

Name the different dental digital imaging systems

A

Phosphor plates
solid states (CCD/CMOS)

41
Q

What do digital imaging systems offer

A

Offer a dose reduction fro intra oral radiography

42
Q

What is essential for digital imaging systems

A

Direct current wave form

43
Q

When is a thyroid collar used

A

When the thyroid Gland is unavoidably in the primary beam of the x ray exposure
so it protects the thyroid From radiation

44
Q

When may a thyroid collar be indicated

A
  1. Cephalometric
  2. CBCT/panoramic examinations where Field Of View extends below mandible
  3. Other situations where thyroid in primary beam
45
Q

Should we make patients wear protective lead aprons

A

NO only carers who may need to be present during an abdomen x ray

46
Q

How can we view radiographs

A
  1. Digital display screen
  2. Digital ambient light
  3. Film
47
Q

What can be adjusted in a digital sepals screen

A

Brightness and contrast

48
Q

What are the benefits of viewing a digital radiogrpah in ambient light

A

Reduces glare and increases contrast

49
Q

How do we view a film radiogrpah

A

Light box
ajustable ambient light
film masking
magnification 2x

50
Q

What errors can occur due to poor technique

A
  1. Cone cutting
  2. Elongation
  3. Over exposure
  4. Underexposure
  5. Incorrect placement in the mouth so wrong teeth captured
51
Q

What technique do we use to take periapicals

A

Paralleling periodical technique

52
Q

what must are ensure to get a good Periapical using the paralleling Periapical Technique

A
  1. The image receptor and the tooth should be parallel (priority)
  2. Make sure there is a short tooth to image receptor distance to minimise distortion
  3. make sure X-ray beam is perpendicular to tooth and image receptor
53
Q

What are the requirements for a High quality bitewing

A
  1. Image receptor and teeth should be parallel
  2. There should be a short tooth to image receptor distance
  3. Make sure x ray beam is perpendicular to teeth and image receptor
54
Q

What is the importance of having good technique when taking radiographs

A

to produce Geometrical reproducible radiographs

55
Q

what should we ensure we use to ensure we take an appropriate panoramic radiograph

A

Light beam diaphragms

56
Q

Talk through how we use the light beam diaphragms

A
  1. Make sure occlusal plane is parallel to the floor
  2. Appropriate anteroom posterior position
  3. No rotation
57
Q

Where does staff exposure from radiographs come from

A
  1. The primary beam
  2. Radiation leakage from the tube-head
  3. Scatter from the patient
58
Q

How can we limit the dosage of radiation to staff members practically

A
  1. Appropriate equipment management
  2. Application of local rules and enforcement of the controlled are
  3. NEVER hold the image receptor in the patients mouth during exposure
  4. NEVER hold the x ray tube head during exposure

5th Yr - CP5- IRMER (6 decks)

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