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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
How much filtration should we have for an x ray machine running at up to and including 70 kV
1.5mm aluminium
26
How much filtration should we have for an x ray machine running greater than 70 kV
2.5mm aluminium
27
What are the benefits of a rectangular collimator
Shapes and limits the beams size Can reduce the dose by 50% compared to circular collimation
28
When should rectangular collimation be used
For ALL: 1. Periapicals 2. Bitewings 3. Occlusal radiographs
29
What does the spacer Cone determine
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
What does a longer spacer cone result in
1. Improved image quality 2. Reduced patient dose
31
What does FSD stand for
focal spot to skin distance
32
What FSD should the spacer cone give
A focal spot to skin distance (FSD) of at least 20cm
33
Where should the end of the spacer Coen be in relation to the patient
As close the patients skin as possible without touching it
34
What concept governs the effect of the spacer cone length
Inverse square law
35
What does the inverse square law state
Beam intensity reduces by the increase in distance squared (intensity= 1/d^2)
36
What does the inverse square law mean in lay terms
Doubling the distance of a spacer cone reduces the intensity by factor 4
37
Which image receptor should we select
The fastest available system compatible with a satisfactory diagnostic result should be selected
38
Which film should we use
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
Name the different speed film
D speed film E speed film F speed film
40
Name the different dental digital imaging systems
Phosphor plates solid states (CCD/CMOS)
41
What do digital imaging systems offer
Offer a dose reduction fro intra oral radiography
42
What is essential for digital imaging systems
Direct current wave form
43
When is a thyroid collar used
When the thyroid Gland is unavoidably in the primary beam of the x ray exposure so it protects the thyroid From radiation
44
When may a thyroid collar be indicated
1. Cephalometric 2. CBCT/panoramic examinations where Field Of View extends below mandible 3. Other situations where thyroid in primary beam
45
Should we make patients wear protective lead aprons
NO only carers who may need to be present during an abdomen x ray
46
How can we view radiographs
1. Digital display screen 2. Digital ambient light 3. Film
47
What can be adjusted in a digital sepals screen
Brightness and contrast
48
What are the benefits of viewing a digital radiogrpah in ambient light
Reduces glare and increases contrast
49
How do we view a film radiogrpah
Light box ajustable ambient light film masking magnification 2x
50
What errors can occur due to poor technique
1. Cone cutting 2. Elongation 3. Over exposure 4. Underexposure 5. Incorrect placement in the mouth so wrong teeth captured
51
What technique do we use to take periapicals
Paralleling periodical technique
52
what must are ensure to get a good Periapical using the paralleling Periapical Technique
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
What are the requirements for a High quality bitewing
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
What is the importance of having good technique when taking radiographs
to produce Geometrical reproducible radiographs
55
what should we ensure we use to ensure we take an appropriate panoramic radiograph
Light beam diaphragms
56
Talk through how we use the light beam diaphragms
1. Make sure occlusal plane is parallel to the floor 2. Appropriate anteroom posterior position 3. No rotation
57
Where does staff exposure from radiographs come from
1. The primary beam 2. Radiation leakage from the tube-head 3. Scatter from the patient
58
How can we limit the dosage of radiation to staff members practically
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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