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ODDR > Radiation Physics > Flashcards

Radiation Physics Flashcards

1
Q

What are the ironising radiation medical exposure regulations (IRMER)

A

Concerns Patient protection and it’s enforced by the care quality commission (CQC)

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2
Q

What do the IRMER regulations apply too?

A

Patient exposure

Volunteer exposure

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3
Q

What is the IRMER philosophy

A 
Avoid unnessicary exposure 
Every exposure must have net benefit 
Optimise exposures 
Ensure quality of exposures 
Written clinical evaluation 
Define responsibilities or operators etc
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4
Q

What must medical radiation equipment do

A

Capable or restricting exposure to a patient
Fitted with an indicator of radiation
Subject to lots of testing
Subject to quality assurance testing

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5
Q

What happens in quality assurance?

A

Measure the dose and check it matches with what the devices says

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6
Q

What are the main 2 IRMER principles

A

X-rays must have net benefit

X rays must be in as low as reasonably practical

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7
Q

What must the employers procedures include IRMER

A 
There must be written procedures for referees pro action era and operators. Justification for medical exposure. Non medical exposure procedure
Pregnant patients 
Career exposure 
Written standard operating protocols
Clinical evaluation 
Diagnostic reference levels 
Audit review
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8
Q

What is the IRMER referrer

A

Anyone the employer decides is entitled to refer, could be dentists, GP or healthcare professional.
Referred must provide significant and correct information to identify the patient and clinical information justifying the X-ray
Must be provided with written criteria

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9
Q

IRMER Practitioner

A

Anyone the employer decides can justify a dental radiograph
Only clinically justified
Justification must be written prior to exposure
Process must identify individual response
Radiograph only based on referrals info practitioner must justify and authorise

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10
Q

IRMER who is the operator

A 
Anyone who operates on the outcome of the successful medical exposure is an operator 
Dentist 
Nurse 
Hygienist 
Physics staff 
Responsibilities must be clearly defined
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11
Q

IRMER operator role

A 
Optimise exposure 
Balancing act between as little as possible exposure but successful radiograph
Ensure correct patient 
Ensure correct examination 
Ask about pregnancy 
Use right exposure factors 
Position patient correctly
Minimise field size
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12
Q

IRMER training

A

Practitioners and operators schedule 3 training

Theoretical knolage relevant to function such as radiation physics management or radiation protection

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13
Q

IRMER patient ID procedure

A

The patient must be identified before exposure
Ask name DoB and address
If they cannot correctly ID then the patient will be sent back to the referrer
It’s the operators responsibility to do this

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14
Q

What is the legislation of IRMER and pregnancy

A

No one should carry out radiograph unless there is sufficient net benefit

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15
Q

What are the diagnostic reference levels

A

Guide the acceptable levels of dose, there are nationally set levels of patient dose thes can be exceeded in individual cases investigated when the are exceeded routinely

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16
Q

What is the average patient entrance dose (PED) for an adult then child

A

Adult 1.37

Child 0.63 mGy

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17
Q

What is the effective dose

A

Adults 4 uSv

Children 1 uSv

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18
Q

What is the average dose of area product (DAP)

A

Adult 80

Child 56 mGy.cm2

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19
Q

Effective dose or area product

A

Adult 10

Child 6 uSv

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20
Q

What is the national diagnostic reference level for DAP

A

Adult 93

Child 67

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21
Q

IRMER image evaluation

A

Carried out and recorded including info on dose etc

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22
Q

IRMER audit

A

All policies must be regularly gone over proving they still work
Clinical audit must be carried out proving it (process) still work
Audit includes procedures are being followed
Quality control of processing
Percentage scoring in levels of images
Written evaluation and comparison with previous audit

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23
Q

IRMER investigations?

A

Patient exposure much greater then intended
Equipment malfunction and unintended exposure

If you think a larger exposure occurs to staff or patient it must be recorded

Incidents: 
Wrong person named on request 
Wrong patient 
Appointment letter goes to the wrong patient 
Not following identification procedure

Doing the wrong x Ray
Duplicated request card or being used twice

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24
Q

IRMER17?

A

This is emphasis on optimisation.
Registration and certification
Requirement for patient dose and monitoring.
Applies to basically anyone
Dose constraintis
Population dose monitoring
Accidental exposure policy must be in place
Estimation of population dose reported to secretary of state
Physics people advice in complacency with this regulation
It all go tributes to safe practise

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25
Q

What is IRR

A

Ionising radiation regulations 2017
Concerned with the protection of employees and general public
WiFi ever by the health and safety executive

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26
Q

IRR guidance

A

There are guidance notes for dental practitioners it’s a framework including ALARP principle
Flow charts should be created

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27
Q

What is a radiation protection adviser

A

Employer must consult this persons to be approved by the HSE

Check that employer is following correct regulations etc

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28
Q

Who are classified persons

A

People who are likely to receive a very high does over 6 throughout whole body

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29
Q

Investigation level

A

The employer must investigate wether an employees dose is more that 15mSv during a year
Hospitals normally set a lower threshold

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30
Q

Dental radiation controlled areas

A

Dedicated x Ray room

Or dental x ray sign meaning x rays 1.5m in any direction

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31
Q

Radiation controlled areas

A

Marked out restrictive monitoring

Power switch outside the room ensure patient safe equipment labels out of order

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32
Q

Define:
Radiology
Radiography
Radiation protection

A

Interpretation of the image
Techniques involved in producing an image
Protecting staff and patient

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33
Q

What’s a periapical radiograph

A

Includes full tooth

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34
Q

Bitewing?

A

Upper and lower crowns (common)

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35
Q

Upper and lower occlousals?

A

These are the odd ones that get the full arch (upper or lower)

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36
Q

Panoramic?(pantomogram)

A

What it says

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37
Q

Lateral cephalogram

A

This is extraordinary of the side profile of the full head

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38
Q

What are interesting anatomical marks seen in radiographs

A 
Incisive foramen 
Canine fossa 
Floor of nasal cavity 
Y shape of Ennis (runs above tooth roots) 
Floor of maxillary Antrum (floor of sinus septum)
Zygomaticus 
Pterygoid hamulus 
Coranoid process 
Submandibular fossa 
IA canal 
Mental foramen 
Lingual foramen
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39
Q

What are the layers of a direct action film

A

Plastic base (cellulose acetate)
adhesive
Emulsion (both sides of base silver halide)
Protective layer (gelatine)
Outer packet protects from saliva
Black paper lining (stops light exposure)
Lead foil absorbs radiation and prevents backscatter onto film

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40
Q

What is the detection film orientation

A

Embossed dot on one corner
Raised dot placed facing the X-ray because

Raised dot at occlousal plane for periapical

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41
Q

What’s an indirect action film

A 
Has intensifying screen in a cassette 
Intensifying screen emits light photons 
Film sensitive to light 
This is used for extraoral radiographs 
Silver halide is reactive to light (blue) 
Modified halides react to all light

Intensifying screen contains fluorescent phosphors convert x Ray energy into light photons by photoelectric affect
Different phosphors different colours

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42
Q

What’s a cassette

A

House image director and intensifying screen
They are light tight aluminium or carbon fibre
Film is between to intensifying screens
Sponge layer ensures smooth contact between film and screen.

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43
Q

How is the film processed

A 
Developed 
Washings 
Fixation (unsensitised crystals removed)
washing (removes fixer solution) 
Drying

The lack is where it has been sensitised and the black fixer sticks

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44
Q

What is film speed

A

This is the speed that the film takes to respond the the x Ray photons it’s related to the amount of crystals and there size in the emulsion.
Faster the larger the crystals
Faster the lower the dose
Always use fastest film

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45
Q

What is optical density

A

This is the degree of blackening in a radiograph

In diagnostic radiology the OD is 0.25-2.5

46
Q

What is fog

A

This is the degree of blackening with zero exposure caused by plastic base if development of u exposed crystals
Fog density should be less than 0.2

47
Q

What are the characteristics of image receptors

A 
Characteristic curve (variation in OD leads to different exposures)
Latitude range of exposures that cause a different OD 
Average gradient if it’s high good contrast but narrow latitude  if low poor contrast but large latitude
48
Q

What are digital receptors used for

A

Periapical or bitewing
Extraoral
Occlousal and lateral obliques

49
Q

How is the digital image made

A

Captured in pixels
Each pixel represents a cube (voxel)
Each pixel measures he total absorb ace through that cube
Each cube given a grey scale value there are 256 options of the scale (black)0-255(white)

50
Q

What’s a solid state sensor ccds

A

Direct digital is a charge coupled device with silicone chips embedded in an electrical circuit.
These pixels arranged in rows called and array or matrix.
Surface scintillation layer of rare earth type material most have wire or cable linking to computer

51
Q

How does a solid state sensor work

A

X-ray photons hit scintillation layer and are converted to light which interacts with silicone via photoelectric affect.
Creates a charge packet which is concentrated by electrodes this is sent to the computers analogue to digital converts to make the image

52
Q

That is a solid state sensor (cmos)

A

Complementary metal oxide detectors these are like the ccds but each pixel is separated from the one around it
Charge packet from each pixel is transferred directly to transistor as a voltage
Allows each pixel to be assessed separately

53
Q

What are the good and bad of solid state sensors

A

Immediate image viewing

Not autoclavable so require protective film
Smaller detector surface than film
Bulky detector and wire
Wireless are bulkier due to extra electronics

54
Q

What do extraoral digital sensors do how are the made

A

Have long thin linear arrays

Scanning motion

55
Q

What are photostimulable phosphor storage plates

A

Similar to film (range of sizes)
Wireless
Reusable
Protective embolisms used for cross infection
Barium flurohalide phosphor on a flexible plastic backing the phosphor layer absorbs and stores the X-ray energy image which’s is scanned by laser then the light is released which is converted to a voltage and related by the computer

56
Q

What does a narrow window mean (low number)

A

Less grey shades more contrast

Higher is more grey shades and greater contrast

57
Q

What’s scatter

A

This is where photons scatter and cause overall darkening if the image

58
Q

How is contrast effected

A

Determined by average slope of the useful part of the characteristic curve
Steeper slope = higher contrast
Affected by exposure processing and background fog
Viewing in monitor reduction in ambient light helps see contrast

59
Q

What happens if film image is too pale

Too dark

A 
Too short developing 
Too cold 
Too dilute 
Exhausted developer 
Underexposed 
Too long in developer 
Too concentrated developer 
Too hot 
Fogged 
Over exposed
60
Q

Resolution

A

Ability if a system to differentiate objects to close together
Can be influenced by penumbra

61
Q

What is a penumbra

How is it reduced

A

Area of partial shadow along object caused by diverging X-ray photons

Object close to receptor
Decreasing focal spot size
Increasing focal spot to detector distance

62
Q

What’s distortion

A

This is where magnification is different in different parts of the object

Arises when the film is not parallel to the object when the X-ray beam is not perpendicular to the receptor.
Can cause foreshortening and elongation

63
Q

What is bad about intensifying screens

A

Amplify photons and cause them to spread out

64
Q

How do digital images become blurry

A

If a pixel lies on a border it will come out a colour in the middle causing blur

65
Q

How much radiation that’s man made comes from medical

How much radiation is manmade

A

97%

16.5%

66
Q

What is the average annual diagnostic dose

A

440uSv

67
Q

What is the current opinion on radiation

A

Harmful in any dose but benefit will outweigh the risk

68
Q

What are the three things that happen with radiation when fired at a human

A

Transmitted (allows us to see radiographs)
Absorbed (harmful)
Scattered harm to others

69
Q

When are cells most vulnerable to radiation

A

In the replication stage more active cells with higher replication rates are more vulnerable

70
Q

How does radiation damage cells

A

Causes ionisation of water to form molecules that can damage chromosomes like free radicals

71
Q

What’s deterministic exposure

A

High dose over short time causes radiation sickness would not occur in dental radiology

72
Q

What’s stochastic exposure

A

Occur at high and low doses causing chronic and potentially long term effects.

73
Q

What dose causes deterministic effects?

A

1000 mSv or above

74
Q

What is the current view of cancer and radiation

A

That cancer risk is 1 in 20000 per mSv
Risks in kids higher then the elderly
Hereditary risk is 1 in 100000 per mSv

75
Q

What are the risks of a dental x Ray

A

1 in 20000 rush of fats cancer for each 1mSv radiation

76
Q

What are the ICRP principles for protection

A

Limitation
Justification
Optimisation

77
Q

What are the effective doses for and adult and child

A
  1. 004 mSv

0. 001 child

78
Q

The risks of cancer from dental intraoral

A

Less than 1 in 6 million

79
Q

What’s a bitewing

A

Shows the crowns with minimal enamel overlap
Half thickness of enamel is acceptable
Used to detect aproximal occlusal recurrent caries
Check for calculus deposits

80
Q

How do you take a bite wing

A

Use film holder long axis of film horizontal use size 2 film film as close to teeth as possible

81
Q

What’s a vertical bitewing

A

Long axis of film is vertical shows more alveolar bone

82
Q

What’s good about a film holder

And bad

A

Simple
Not displaced by tongue
Beam always right angle to film

Uncomfortable
Expensive

83
Q

What’s the adhesive tab technique

A

This is where original tab attached to the middle of the film at a right angle and patient would bite on it. It’s still good for kids

84
Q

What’s a periapical

A

Shows all of tooth used for trauma abscess infection endo etc
It has to be further away from tooth due to anatomical things film size 1 or 2

85
Q

What’s the paralleling technique

A

This is where everything is parallel to the root of the tooth to make a sharp and true image approximately caries well show.

86
Q

What’s the bisecting angle technique

A

Film not perpendicular to beam it’s at and angle this causes elongation etc
Irradiated ginger when doing occlousals from holding film in place
Bone levels not accurate

87
Q

What are occlousals

A

Image of an occlousal arch dot faces arch being imaged can assess impacted teeth etc used for trauma. Or submandibular duct stones
True is where beam is perpendicular
Oblique is where the beam is at an angle

88
Q

Maxillary oblique?

A

Take down through tip of nose at 60-70 degree angle

89
Q

Mandubular true occlousal

A

Up through the mandible

90
Q

Lower anterior occlousal

A

Fired from front of face up through jaw at 45 degree to the film

91
Q

Lower oblique occlousal

A

Fired up through the jaw from one side

92
Q

What’s eV

A

Electron volt

93
Q

What’s photon energy

A

E=he/y

94
Q

How is a bremsstrahlung X-ray made

A

Electron does not collide flies round the nucleus of an atom and emits X-ray

95
Q

How are characteristic xrays produced

A

Electron removed from inner shell

Electrons from outer shell have to move inwards for this emoting xrays.

96
Q

What are the X-ray tube components

A 
Cathode (electron source) 
Anode target 
Glass envolope filters 
Cooling oil 
Shield
97
Q

What does the evacuated glass tube do

A

No other atoms for electrons to interact with provides insulation between anode and cathode

98
Q

What does the metal shield do

A

Stops xrays flying everywhere

99
Q

What does the window do

A

The area that the xrays emerge

100
Q

What is electron energy proportional to

A

Voltage (kV)

101
Q

What is the robe potential

A

KVp quantity if xrays and intensity

102
Q

What is the tube current

A

Electrons flowing from the cathode to anode can be measured in miliamps mA

103
Q

What is x Ray intensity proportional too

A

Tube current

104
Q

What’s filtration

A

Removes low energy photons reduces patient dose

Filtered has lower intensity but greater average photon energy

105
Q

What size focal spot do you want.

A

Small to make a sharper image

106
Q

What is attenuation

A

This is the overall reducing I tensity of an x Ray

107
Q

What’s the photoelectric effect

A

Photon collides wit an electron and causes it to give up all its energy and it no longer exists

108
Q

What’s the Compton scatter effect

A

This is where photon collides wit and electron then gives it some energy and bounces off in a different direction causing scatter

109
Q

What does Compton scatter cause

A

Reduced sharpness image

110
Q

How is scatter avoided

A

Specific range of x rays 30/
-70
Reduce kV (this increases dose )
Anti scatter grids

111
Q

How do you reduce noise

A

Increase the number of x Ray photons

112
Q

What does magnification do

A

Increases dose and all the other things

ODDR (5 decks)

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