Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

BDS3 > Radiology > Flashcards

Radiology Flashcards

1
Q

Radiographs

A

Images created by Xray which have been projected through and object and interacted with a receptor
Different shades of grey on the image correspond to the different types of tissue and thicknesses of tissue involved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why are radiographs useful?

A

Provide ability to see structures within the body, particularly mineralised tissues - many dental related conditions affect the mineral content of tissues
Can show normal anatomy and pathology
Aid diagnosis, treatment planning and monitoring

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Common intra and extra oral dental radiographs

A

Intra
Bitewings
Periapical
Occlusal
Extra
Panoramic
Lateral cephalogram

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Electromagnetic radiation

A

Flow of energy created by simultaneously varying electrical and magnetic fields
No mass
No charge
Travels at speed of light
Can travel in a vacuum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

EM spectrum

A

Shorter wavelength, higher frequency. higher energy
Gamma
Xray
UV
Visible light
Infrared
Microwaves
Radiowaves
Longer wavelength, lower frequency, lower energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Frequency of EM waves

A

How many times one full wave cycle is repeated per unit time in Hertz
One Hz = One cycle per second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Speed of EM waves formula

A

Speed = frequency x wavelength

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Energy of EM waves

A

Measured in electron volts
1 eV = energy (in joules) gained by one electron moving across a potential difference of one volt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Xray photon energies

A

124eV - 124 keV
Medical imaging uses mostly hard Xrays >5keV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Hard Xrays vs soft Xrays

A

Have higher energies and are able to penetrate human tissues
Soft are easily absorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the difference between Xrays and Gamma rays?

A

Gamma occur naturally

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Production of Xrays

A

Electrons are fired at atoms at very high speed and on collision the kinetic energy of the electrons is converted into EM radiation and heat
Xray photons are aimed at a substance
Xrays cause ionisation - displace electrons from atoms/molecules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Electron shells

A

Orbits around atom where electrons are found
Electrons fill available spaces in innermost shells first
Shells are called K, L, M, N etc

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Max number of electrons in a shell

A

2n^2 where n is shell number

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Binding energy

A

Energy required to exceed electrostatic force between an electron and it’s nucleus, and remove the electron
Higher atomic number = higher electrostatic force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Amps

A

Measure of how much charge flows past a point per second

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Current

A

A flow of electrical charge usually by movement of electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why must Xray units modify mains electrical current?

A

Mains is alternation current, Xray requires direct current - rectification of the curren

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Voltage

A

Difference in electrical potential between two points in an electrical field and is related to how forcefully a charge will be pushed through an electrical field
Measured in volts V
Synonymous with potential difference

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Electrical supply to Xray unit

A

UK mains electricity is AC 13 amps or less, 220-240 volts
Dental Xray requires a direct current with 2 different voltages - one as high as 10s of thousands of volts, one as low as around 10
Transformers alter voltage from one circuit to another
One transformer mains -> Xray tube (cathode - anode)
One transformer mains -> filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Xray beam

A

Made up on millions of Xray photons directed in the same general direction
They travel in straight lines but diverge from Xray source
Intensity is the quantity of photon energy passing through a cross sections area of the beam per unit time
Increased number or energy of photons = increased intensity, proportional to the current in the filament and voltage across the Xray tube

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Intensity of Xray compared to distance from source

A

The intensity of Xray beam is inversely proportional to the square distance between the Xray source and the point of measurement
Doubling the distance will quarter the dose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Xray production basic outline

A

Electrons accelerated towards atoms at very high speed
On collision, the kinetic energy of these electrons is converted to heat and electromagnetic radiation (ideally Xray photons)
The Xray photons are aimed at a subject

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Components of Xray unit

A

Tubehead
Collimator
Positioning arm
Control panel
Circuitry

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

Xray tube

A

Made up of a glass envelope with a vacuum inside, containing -ve cathode (filament and focussing cup)and +ve anode (target and heat dissipating block)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What material is the heat dissipating block in Xray tube?

A

Copper

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What material is the focussing cup in Xray tube?

A

Molybdenum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What material is the filament in Xray tube?

A

Tungsten, because of its high melting point 3422C and high atomic number 74 so lots of electrons per atom to be released
It is also suitably malleable to form the coiled wire

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What occurs at the cathode in the Xray tube?

A

A low voltage, high current electricity is passed through the Xray filament, heating it til incandescent ~2200C
Electrons are then released from atoms in the wire creating a cloud of electrons around the filament

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

Focussing cup

A

Metal plate shaped around the filament
Negatively charged to repel electrons towards the anode target
Made of molybdenum due to its high mp 2623C

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

Between cathode and anode

A

Electrons are accelerated to a very high speed, and have high kinetic energy on collision with the anode target

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Kinetic energy of electrons in Xray tube

A

60-70keV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

Xray anode target

A

Metal block which gets bombarded with electrons, producing photons (and lots of heat)
Made of Tungsten due to its high mp and the fact that it creates xray photons of useful energies
Orientated at angle from filament as this reduces area from which Xray is emitted while increasing actual SA, for heat dissipation
Focal spot is the precise area on the target at which electrons collide and produce Xrays

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Penumbra effect

A

Blurring of radiographic image due to focal spot not being a single point, minimised by shrinking the focal spot

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

Glass envelope

A

Air tight vacuum so that air particles don’t get in the way of electron path
Leaded apart from one small window, so that Xray photons can only escape in the desired direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

Purpose of oil in glass envelope

A

Heat dissipation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

Aluminium filtration in Xray tube

A

Removes lower energy non diagnostic Xray from the beam as these are fully absorbed, not contributing to image but increased pt dose - reduces photoelectric effect
Thickness required <70kV-1.5mm 70kV+ - 2.5mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

Spacer cone

A

Helps direct beam
Creates desired focus to skin distance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

FSD

A

<60kV 100mm
60kV+ 200mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

Collimator

A

Lead diaphragm attached to the end of the spacer cone which reduces pt dose and focuses beam to shape and size of the receptor
When using size 2 receptors, rectangular collimators should (at min) crop the beam area to 50x40mm but preferably 45x35mmo

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

Why is rectangular collimation recomended?

A

Can reduce pt dose by approx 50% and improves image contrast by reducing scatter

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Xray control panel

A

On/off switch and light
Electronic timer
Exposure time selector and presets
Warning light and noise

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Continuous vs characteristic radiation

A

Continuous - produces continuous range of photon energies, maximum matches the peak voltage, bombarding electron interacts with the nucleus of target atom
Characteristic - produces specific photon energies, characteristic to the target element, photon energies depend on the binding energies of electron shells, bombarding electrons interact with inner shell electrons of target atom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Typical characteristic spikes of electron energy in Xray unit 70kV

A

59kV 67kV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

3 ways photons can interact with matter

A

Transmission - passes through unaltered
Absorption - stopped by the matter
Scatter - changes direction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

Result of absorption and scatter occurring

A

Attenuation - reduced intensity of Xray beam

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

What determines Xray number of photons?

A

Current in the filament mA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
48
Q

What affects the energy of Xray photons?

A

Voltage across Xray tube kV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
49
Q

Minimal attenuation appearance

A

Black

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
50
Q

Partial attenuation appearance

A

Grey

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
51
Q

Complete attenuation appearance

A

White

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
52
Q

Photoelectric effect

A

Complete absorption
Photon in Xray beam interacts with inner shell electron in subject, resulting in absorption of the photon and creation of a photoelectron - gives out light

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
53
Q

When does the photoelectric effect occur?

A

Energy of photon is equal to or just greater than the binding energy of inner shell electrons, therefore photoelectric effect predominates with lower energy photons, since human tissues have relatively low binding energies
Any excess photon energy becomes kinetic energy of photoelectron and this can ionise and potentially damage adjacent tissues
Inner electron shell them filled by cascade which produces light photons and/or heat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
54
Q

Probability of photoelectric effect

A

~ (p x Z^3)/ E^3
p - density of material
Z atomic number
E photon energy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
55
Q

Compton effect

A

Partial absorption and scatter
Photon in beam interacts with an outer shell electron in the subject and results in partial absorption and scattering of the photon and creation of a recoil electron

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
56
Q

When does the Compton effect occur?

A

When the energy of incoming photon is much greater than binding energy of electron, therefore it predominates between higher energy photons and outer shell electrons

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
57
Q

Effect of recoil electron production by Compton effect

A

Recoil electrons can ionise and potentially damage adjacent tissues

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
58
Q

What happens to a photon after it undergoes the Compton effect?

A

The photon loses energy and changes direction, it can still undergo the photoelectric or further Compton effect

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
59
Q

What is the effect of energy of photon on direction of scatter?

A

Higher energy are deflected more forward
Lower energy are deflected more backward

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
60
Q

What is the effect of photons being scattered slightly obliquely?

A

May still reach the receptor but will interact with the wrong area, causing darkening of the image in the wrong place
Results in fogging of the image and reduces image contrast and quality

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
61
Q

Types of ionising radiation

A
  1. Byproducts of radioactive decay (alpha large 2n 2p particle, travels few inches, beta small particle travels few feet, gamma high energy travels long distance)
  2. Artificially produced radiation - Xray

Xray and gamma rays are identical apart from Xrays being produced artifically

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
62
Q

Most significant effect of ionising radiation

A

DNA in cells nuclei can be damaged - faulty repair of chromosome breaks resulting in the development of abnormal cell populations and therefore cancer
Can damage DNA directly (radiation interacts with DNA molecule or another important part of the cell) or indirectly (radiation reacts with water within the cell, producing highly reactive free radicals which can join in pairs to form hydroxyl radicals, which can cause damage to the cell)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
63
Q

Ionising radiation

A

Ionising radiation has enough energy to turn atoms into ions by knocking away electrons in the atoms orbit, this results in a positive ion and a free electron
Each ionisation process will deposit approx 35eV locally, greater than the energy involved in atomic bonds (approx 4eV)

64
Q

Damage to DNA double stranded helix

A

One broken strand - usually repairable
Double strand break - more difficult to repair, usually due to alpha radiation, if repair is faulty, can lead to mutations affecting cell function
Biological effect will depend on type of radiation, amount of radiation, time over which dose is received, tissue/cell type irradiated

65
Q

Organ cancer risks and radiation

A

There are only increased risks of cancer after irradiation of certain tissues
Most medical exposures do not irriadiate the body uniformly
Risk will vary depending on the organ getting the highest dose

66
Q

What determines radiosensitivity of tissues?

A

Function of the cells that make up the tissue
If the cells are actively dividing

67
Q

Highly radiosensitive tissues

A

Stem cells
Bone marrow
Lymphoid tissue
GI
Gonads
Embryonic tissue

68
Q

Moderately radiosensitive tissues

A

Skin
Vascular endothelium
Lung
Lens of the eye

69
Q

Least radiosensitive tissues

A

CNS
Bone
Cartilage
Connective tissue

70
Q

3 possible outcomes after radiation causes DNA mutation of a cell

A

Mutation repaired
Cell death
Mutated cell survives, can cause cancer

71
Q

What does LNT Linear No Threshold model estimate?

A

The long term biological damage from radiation

72
Q

Absorbed dose

A

Energy deposited by radiation
Units Gy Gray

73
Q

Equivalent dose

A

Absorbed dose multiplied by weighting factor depending on the radiation type
Beta, gamma, xray - weighting 1
Alpha weighting 20
Measured in Sieverts Sv

74
Q

Digital receptors

A

Phosphor plates
Solid state sensors
All multiple use

75
Q

What is the difference between digital and film radiography?

A

Differ in how the Xray beam is dealt with after it has interacted with the patient - difference in the film and how the film is processed
Digital has mostly taken fil radiography’s place due to multiple benefits but film is still sometimes used

76
Q

Film receptors

A

Direct action or indirect action
All single use

77
Q

Sizes of receptors

A

Variety, exact measurements may differ between companies
Size 0 - ant PA
Size 2 - BWs, post PA
Size 4 - Occlusal

78
Q

Xray shadow

A

When beam passes through an object some photons are attenuated - this cross section is an Xray shadow
The shadow is basically the image information held by the Xray photons after a beam has passed through an object
Image receptor detects this Xray shadow and uses it to create an image

79
Q

How do digital receptors create an image?

A

The receptor measure the Xray intensity in each defined area
Each area is given a value relating to the intensity (typically 0-225, most-least)
Each value corresponds with a shade of grey
Lower number darker shade
Displayed as a grid of squares called pixels
More pixels - better detail

80
Q

What is the effect of increasing the number of pixels on a digital Xray image?

A

Increases the resolution which will provide a more diagnostic image up to a limit

81
Q

Greyscale bit depth

A

Number of different shades of grey available
Typically at least 8 bits
Shades of grey = 2^8

82
Q

DICOM

A

Format for digital images
International standard format for handling digital medical images

83
Q

PACS

A

Picture archiving communication system
Storage and access to images
Not connected to dental practices
Main components - inputs, secure network, workstations, archive

84
Q

Environment for viewing digital radiographs

A

Subdued lighting
Avoid glare
Monitor - clean, adequate resolution, high enough brightness and suitable contrast level

85
Q

SMPTE test pattern

A

Society of Motion Picture and Television Engineers
Available online
Can be used to assess the resolution, contrast and brightness of your monitor

86
Q

Phosphor plates/photostimulable phosphor plate/storage phosphor plate

A

Not connected to computer
Thinner than solid state
After receptor is exposed to Xrays, it must be put in a scanner and read to create final image

87
Q

Image creation using phosphor plates in patient’s mouth

A

Receptor exposed to Xray beam
Phosphor crystals in receptor excited by the Xray energy, resulting in the creation of a latent image

88
Q

Image creation with phosphor plates in the scanner

A

Receptor scanned by a laser
Laser energy causes the excited phosphor crystals to emit visible light
This light is detected and creates the digital image

89
Q

Types of solid state sensors

A

CCD charge coupled device
CMOS complimentary metal oxide semiconductor

90
Q

Solid state sensors image creation

A

Usually wired but can be wireless
Latent image created and immediately read within the sensor itself
Final image created virtually instantly

91
Q

Solid state sensor components

A

Back housing and cable
Electronic substrate
CMOS imaging chip
Fibre optic face plate
Scintillator screen
Front housing

92
Q

Identification dot

A

Located in corner of receptor to aid orientation of image
Only useful if receptor was positioned correctly during exposure

93
Q

Cross infection control when taking digital radiographs

A

Intra oral receptors have purpose made covers to prevent saliva contamination - single use
Receptors still disinfected between uses

94
Q

Why is careful handing of digital receptors important?

A

Certain types of damage will impact every subsequent image obtained from that receptor
Reduces their diagnostic value and may render receptor unusable
Hold by their edge not their flat surfaces

95
Q

What causes white lines on digital receptors??

A

Scratches/tears
Fingerprints
Bending/creases

96
Q

Phosphor plates vs solid state sensors

A

PP - thinner, lighter, usually flexible, wireless (more comfortable). Variable room-light sensitivity, risk of impaired image, latent image needs to be scanned separately, handling similar to film, delicate
SS - bulkier, more rigid, usually wired, smaller active area, no issues with room-light control, replace less often, more expensive

97
Q

Components of film packet

A

Radiographic film
Protective black paper to protect film from light exposure, damage from fingers, saliva
Lead foil backing to absorb some excess Xray photons
Outer wrapper usually plastic which prevents saliva ingress, and indicated which side of the packet is the front

98
Q

Radiographic film

A

Material in which the actual image is formed
Sensitive to Xray and visible light photons
Photons interact with emulsion on film to produce latent image which only becomes visible after chemical processing

99
Q

Radiographic film structure

A

Transparent plastic base to support the emulsion
Adhesive to attach emulsion
Emulsion layered on both sides
Protective coat of clear gelatin to shield the emulsion from mechanical damage

100
Q

Radiographic emulsion

A

Silver halide crystals embedded in gelatine binder
Microscopic crystals effectively become the pixels of the final image
Film generally higher resolution than digital

101
Q

Silver halide crystals in film radiography

A

Usually silver bromide
Become sensitised on interaction with Xray (and v. light) photons
During processing sensitised crystals are converted to particles of black metallic silver -> dark parts of final image and non sensitised crystals are removed -> light parts of final image

102
Q

Lead foil in film radiography

A

In packet, behind the film
Absorbs some excess photons - those in the beam that continue past the film AND those scattered by pt tissues and returning back to the film
Embossed textured pattern to make it obvious if receptor was placed the wrong way around

103
Q

Film speed

A

Relates to the amount of Xray exposure required to produce an adequate image
Increase speed leads to reduced radiation required to receive an image
Affected by number and size of silver halide crystals in the emulsion
Larger crystals -> faster film but poorer resolution, because crystals act as pixels

104
Q

Film speeds

A

E 2x faster than D, half the exposure time, half the dose
F 20% faster than E, 20% reduction in time and dose
If changing to different film speed, you must either convert settings on Xray unit or install a filter to absorb part of the primary Xray beam

105
Q

Intensifying screens

A

Used alongside indirect action film for extra oral radiographs (too bulky for intraoral use)
Reduce radiation dose but also reduce detail
Becoming less common as digital receptors become more commonplace
Indirect action film placed inside a cassette with an intensifying screen either side
Screens release v light upon exposure to xrays, this visible light creates the latent image on the film

106
Q

Film processing

A

Sequence of steps which converts the invisible latent image into a visible permanent image
MUST be carried out under controlled standardised conditions to ensure consistent image quality
Different methods - manual, automated, self developing (less common)

107
Q

Common steps of all film processing methods

A

Developing - converts sensitised crystals to black metallic silver particles
Washing - removes residual developer solution
Fixing - Removes non sensitised crystals and hardens emulsion (which contains the black metallic silver)
Washing - removes the residual fixer solution
Drying - Removes water so that film is ready to be handled/stored

108
Q

Manual (or wet) cycle

A

Person dips film into different tanks of chemicals at precise concentrations and temps for specific durations, then washes film after each tank
Must be carried out in a dark room with absolute light-tightness and adequate ventilation
Fairly laborious process

109
Q

Automated cycle

A

More common way of film processing
All necessary steps are carried out within a machine
Exposed film goes in one end, processed film comes out other
Faster and more controlled than manual processing and avoids the need for a dark room
BUT more expensive

110
Q

Opening a film packet for automated processing

A

Disinfect the surface of the packet
Hold the packet under the hood of the processor unit
Peel back flap of outer wrapper
Fold back lead foil
Pull back paper flap
Hold film by edges and slide out
Insert film into processor slot/shelf

111
Q

Self developing films

A

Not recommended
Advantages - no darkroom or processing facilities required, faster
Disadvantages - poorer image quality, image deteriorated more rapidly over time, no lead foil, easily bent, difficult to use in positioning holders, relatively expensive

112
Q

Processing issues with developing

A

Developing (silver halide -> black metallic silver) involves a chemical reaction affected by time, temp and concentration, developer solution oxidises in air and becomes less effective in time - needs to be replaced regularly

113
Q

Potential causes of a pale image in film radiography

A

Exposure issue - radiation exposure factors too low
Developing issue - film removed from solution too early, solution too cold, dilute or old

114
Q

Potential issues in fixing stage of film developing

A

Fixing involves a chemical reaction which removes non sensitised crystals and hardens the remaining emulsion
Inadequate fixing means non sensitised crystals are left behind meaning
Image greenish-yellow or milky
Image becomes brown over time

115
Q

Potential issues in fixing stage of film developing

A

Fixing involves a chemical reaction which removes non sensitised crystals and hardens the remaining emulsion
Inadequate fixing means non sensitised crystals are left behind meaning
Image greenish-yellow or milky
Image becomes brown over time

116
Q

Potential issues with film developing washing stage

A

Developer and fixer solution will continue to act if not washed off

117
Q

Advantages of digital radiograhy

A

Computer filing - easy storage and archive
Easy back up of images
Images can be integrated into pt notes
Easy transfer of images
Images can be manipulated
No chemical processing required

118
Q

Disadvantages of digital radiography

A

Worse resolution - risk of pixelation
Requires diagnostic level computer monitors for optimal viewing
Risk of data corruption/loss
Hard copy print outs generally have reduced quality
Image enhancement can create misleading images

119
Q

Extra oral radiography

A

Xray source and receptor outside patient
Allows visualisation or teeth, jaws, facial bones etc

120
Q

Extra oral radiography purposes

A

Imaging larger sections of the dentition
Alternative when pt unable to tolerate intra oral
Imagine non dento-alveolar regions

121
Q

Common extra oral radiograph types

A

Panoramic
Cephalometric - lateral, postero-anterior
Oblique lateral
Skull radiographs - occipitomental, poster-anterior skull/mandible, Reverse Towne’s, true lateral

122
Q

True vs oblique

A

True - Xray beam perpendicular to head
Oblique - not perpendicular, off at an angle

123
Q

Mid sagittal plane

A

Line down middle of the face

124
Q

Interpupillary line

A

Connects both pupils

125
Q

Frankfort plane

A

Connects infraorbital margin and superior border of external auditory meatus

126
Q

Orbitomeatal line

A

Connects outer canthus and centre or EAM

127
Q

Cephalostat

A

On all units that take cephalograms
Ensure standardised positioning of equipment and patients head - avoids discrepancies between radiographs and reduces magnification/distortion
Includes ear rods and forehead support

128
Q

Lateral cephalograms receptor to focal spot distance

A

1.5-1.8m from Xray focal spot to receptor, to minimise magnification

129
Q

Problem and solutions for visualising soft tissues on lateral cephalograms

A

Soft tissues show up poorly when exposure settings are optimised for hard tissues
Solutions
Place an aluminium wedge filter in the unit to attenuate the specific area of the beam exposing the soft tissues
or
Used software to enhance the soft tissues post exposure

130
Q

Thyroid collar

A

Almost always used when taking lateral cephalograms
Thyroid gland is relatively radio sensitive
May obscure hyoid bone and cervical vertebrae, irrelevant to most cases, but sometimes used to assess maturity of skeleton

131
Q

Thyroid collar

A

Almost always used when taking lateral cephalograms
Thyroid gland is relatively radio sensitive
May obscure hyoid bone and cervical vertebrae, irrelevant to most cases, but sometimes used to assess maturity of skeleton

132
Q

Benefits of CBCT

A

No superimposition or magnification of anatomy
Images can be viewed at any angle
(not indicated currently due to increased radiation dose)
Indicated for orthognathic surgery for pre op assessment

133
Q

Benefits of CBCT

A

No superimposition or magnification of anatomy
Images can be viewed at any angle
(not indicated currently due to increased radiation dose)
Indicated for orthognathic surgery for pre op assessment

134
Q

Benefits of CBCT

A

No superimposition or magnification of anatomy
Images can be viewed at any angle
(not indicated currently due to increased radiation dose)
Indicated for orthognathic surgery for pre op assessment

135
Q

Benefits of CBCT

A

No superimposition or magnification of anatomy
Images can be viewed at any angle
(not indicated currently due to increased radiation dose)
Indicated for orthognathic surgery for pre op assessment

136
Q

Oblique lateral radiography

A

Provides view of posterior jaws without superimposition of contralateral side
Uncommon nowadays - difficult to master technique
Superseded by panoramic in most situations

137
Q

Oblique lateral radiography

A

Provides view of posterior jaws without superimposition of contralateral side
Uncommon nowadays - difficult to master technique
Superseded by panoramic in most situations

138
Q

Indications for oblique lateral radiography

A

(Similar to panoramic)
Assessment of dental pathology
Assessment of presence/position of unerupted teeth
Detection of mandibular fractures
Evaluation lesions/conditions affecting jaws

As an alternative to panoramic when pre-cooperative, learning difficulties, tremors, unconscious

139
Q

Cone beam CT

A

Sectional images - thin slices 0.4mm or thinner

140
Q

Why do we use radiographic localisation?

A

To determine location of a structure or pathological lesion in relation to other structures

141
Q

Clinical situations where radiographic localisation may be used

A

Positions of unerupted teeth - most common
- normal but ectopic or impacted, supernumerary, proximity to important structures
Location of roots/canals for endo or surgery
Relationship of pathological lesions to normal features
Trauma
Soft tissue swellings

142
Q

Parallax

A

An apparent change in position of an object caused by a real change in the position of the observer

143
Q

Sequence of events for parallax

A

Identify direction of tube head shift
Identify structure we want to know the location of
Choose a reference point which can be seen in both images
Observe the movement of the desired structure in relation to the reference point

144
Q

Options for parallax with horizontal tube shift

A

Equivalent views such at 2 PAs, 2 BWs, 2 oblique occlusals

145
Q

Options of radiographs for parallax with vertical tube shift

A

Different views such as panoramic and oblique occlusal, panoramic and bisecting angle lower periapical

146
Q

Purpose of quality assurance in dental radiology

A

To ensure consistently adequate diagnostic information, whilst radiation doses to patients (and others) are kept ALARP taking into account the relevant requirements from IMRER17 and IRR17

147
Q

Quality assurance programme components

A

Procedures - risk assessment, local rules, contingency plans
Staff training
Xray equipment
Patient dose
Display equipment
Image quality

148
Q

Regular checks for digital image receptors

A

Check receptor itself for visible damage
Check image uniformity by exposing the receptor and checking if image is uniform - constant shade of grey
Check image quality - radiograph of a test object

149
Q

How does delamination of digital receptors appear?

A

White areas around edge

150
Q

How does cracking of digital receptors appear?

A

Network of white lines

151
Q

How do scratches on digital receptors appear?

A

White lines

152
Q

What could black marks on digital radiographs be caused by?

A

Sensitisation of radiographic emulsion

153
Q

Quality assessment of image quality 3 parts

A

Image quality rating - grading
Image quality analysis - reviewing images to calculate success rate and identify any trends for suboptimal images, carried out periodically e.g. every 4 month, last 150 images reviewed
Reject analysis - recording and analysing each unacceptable image

154
Q

Diagnostically acceptable positioning factors for BWs

A

Show entire crowns of upper and lower teeth
Include distal aspect of the canine and mesial aspect of last standing tooth (may require more than one)
Every approximal surface shown at least once without overlap (where possible, may be impossible if crowding)

155
Q

Diagnostically acceptable positioning factors for PAs

A

Shows entire root
Shows periapical bone
Shows crown

BDS3 (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions