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BDS Finals > Radiology > Flashcards

Radiology Flashcards

1
Q

What type of current do X-Ray producers need

A

Direct current

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2
Q

How do X-Ray machines get current from the mains

A

They have generators which modify AC so that it becomes DC
This process is called rectification

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3
Q

Inverse Square Law - Radiology

A

The further the patient stands from the X-ray beam, the lower the dose

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4
Q

Parallax

A

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

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5
Q

What might X-Ray photons do as they travel through tissue (4)

A

Pass through unaltered
Scatter without losing energy
Scatter and be absorbed
Be absorbed

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6
Q

X-Ray attenuation (2)

A

Reducing in number of photons within beam
Result of absorption and scatter

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7
Q

What colour are areas on an X-Ray with complete attenuation

A

White

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8
Q

How can scatter be reduced

A

Reduction of area irradiated also called collimation

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9
Q

What is the absorbed radiation dose measured in

A

Greys

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10
Q

What is the effective radiation dose measured in

A

Sieverts

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11
Q

What guidelines govern radiology (2)

A

Ionising Radiation and Medical Exposure Guidelines (IRME)
Ionising Radiation Regulations (2017)

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12
Q

What should you ask the patient to do before taking a panoramic radiograph

A

Put their tongue to the roof of their mouth or there will be a dark line across teeth (air)

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13
Q

How is a film radiographic image produced (6)

A

Development
Rinsing
Fixation
Removing
Washing
Drying

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14
Q

What is KVP (2)

A

Peak Kilovoltage
Max voltage applied across X-ray tube

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15
Q

How does an increase in voltage effect scatter

A

Increases scatter

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16
Q

Film radiograph too dark

A

Overexposed
Developer left on too long

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17
Q

How often should radiology equipment be tested

A

Daily

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18
Q

How is a panoramic radiograph formed?

A

Simultaneous movement of beam and image receptor

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19
Q

DPT

A

Dental Panoramic Topograph

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20
Q

DPR

A

Dental Panoramic Radiograph

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21
Q

Impact of distance from rotation centre on panoramic radiology (3)

A

Further from rotation centre - faster movement
Anteriors closer to rotation centre so slower movement
Closer to rotation centre - narrower focal layer

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22
Q

Focal trough

A

The layer of tissues in focus

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23
Q

What must be done prior to panoramic radiograph

A

All metal objects removed

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24
Q

Reference plane for panoramic radiograph

A

Frankfort plane

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25
Q

Angulation of panoramic radiograph

A

Upwards at 8 degrees due to curve of monson

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26
Q

Where should the vertical canine line be on a panoramic radiograph

A

On the upper canines

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27
Q

Limitations of panoramic radiology (5)

A
  1. Big shoulders
  2. Long exposure time
  3. Width of layer in focus (structures may be present that cannot be seen)
  4. Horizontal distortion
  5. Positioning difficulties
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28
Q

Positioning difficulties for panoramic radiology (3)

A

Class II Div 1
Class III
Very young/very old

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29
Q

Panoramic - Patients canines behind canine guide line (3)

A
  1. Closer to source than machine expects
  2. Image magnified horizontally
  3. Beam too slow
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30
Q

Panoramic - Patients canines in front of canine guide line (3)

A
  1. Further from source than machine expects
  2. Beam too fast
  3. Teeth reduced in width
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31
Q

Common ghost images (4)

A
  1. Earrings
  2. Metal restorations
  3. Anatomical features
  4. Soft tissue calcifications - lymph nodes, salivary calcifications
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32
Q

Position of ghost images (3)

A
  1. Always higher due to angulation
  2. Horizontally magnified
  3. Usually further forward
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33
Q

Digital receptors (2)

A
  1. Phosphor plate
  2. Solid-slate sensor
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34
Q

Film Receptors (2)

A
  1. Direct action
  2. Indirect action
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35
Q

Size 0 Receptor

A

Anterior periapicals

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36
Q

Size 2 Receptor

A

Bitewings
Posterior periapicals

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37
Q

Size 4 Receptor

A

Occlusal Radiographs

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38
Q

Appearance of dentinogenesis imperfecta on radiographs

A

Sclerosis (thinning) of root canals

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39
Q

Types of skull radiograph (4)

A
  1. Occipitomental
  2. Postero-anterior mandible
  3. Reverse Towne’s
  4. True lateral skull
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40
Q

What area is mainly assessed by occipitomental radiographs

A

Midface

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41
Q

What area is mainly assessed by postero-anterior mandible radiographs

A

Posterior mandible excluding condyles

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42
Q

Reference line used for most skull radiographs

A

Orbitomeatal line

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43
Q

Angles for occipitomental radiographs (4)

A

0
10
30
40

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44
Q

How would facial fractures be assessed with radiographs (2)

A
  1. Occipitomental
  2. Typically 2 angles used
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45
Q

OM Radiograph Positioning (4)

A
  1. Face towards receptor
  2. Orbitomeatal line 45 degrees to receptor
  3. 0 degrees - beam central/perpendicular to receptor
  4. Nose-chin position
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46
Q

Why is a PA mandible radiograph not suitable for viewing facial skull

A

Superimposition of skull base

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47
Q

Fractures that indicate an OM radiograph (5)

A
  1. Le fort
  2. Zygomatic complex
  3. Naso-ethmoidal complex
  4. Orbital blow out
  5. Coronoid process (not fracture)
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48
Q

Fractures that indicate PA mandible radiograph (4)

A
  1. posterior third of body of mandible
  2. Angles of mandible
  3. Ramus
  4. Low condylar necks
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49
Q

Other indications for PA mandible radiograph (2)

A
  1. Mandibular hypo/hyperplasia
  2. Maxillofacial deformities
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50
Q

PA mandible radiograph positioning (4)

A
  1. Face towards receptor
  2. Head tipped forward so orbitomeatal line perpendicular to receptor
  3. Beam central and perpendicular
  4. Forehead nose position
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51
Q

Why is x-ray projects from the posterior side of the head for skull radiographs (2)

A

Reduced magnification of face - less distortion of relevant features
Reduced effective dose for sensitive structures - lens

52
Q

What is shown on a reverse Towne’s radiograph

A

Condylar heads and necks

53
Q

Indications for reverse Towne’s radiograph (3)

A
  1. High fractures of condylar necks
  2. Intracapsular fractures of TMJ
  3. Condylar hypoplasia/hyperplasia
54
Q

How does a reverse Towne’s differ from a PA mandible (2)

A

Mouth is open
Slightly different beam angle

55
Q

Reverse Towne’s positioning (4)

A
  1. Head tipped forward - orbitomeatal line parallel to floor
  2. Mouth open
  3. Beam 30 degrees below perpendicular line to receptor and centred through condyles
  4. Forehead nose
56
Q

What does the pts mouth being open for reverse Towne’s do to condylar heads

A

Moves condylar heads out of glenoid fossa

57
Q

What does CBCT stand for

A

Cone beam computed tomography

58
Q

What is CBCT

A

Cross sectional imaging suitable for assessing radio dense structures

59
Q

What shape is the x ray beam in CBCT

A

Conical/Pyramidal

60
Q

Head positioning for CBCT (2)

A
  1. Unit dependant (sitting/standing/supine)
  2. Head level with ground - frankfort
61
Q

Benefits of CBCT over plain radiography (4)

A
  1. No superimposition
  2. Ability to view subject from any angle
  3. No magnification/distortion
  4. Allows for volumetric (3D) reconstruction
62
Q

Disadvantages of CBCT over plain radiography (5)

A
  1. Increased radiation dose to patient
  2. Not as ‘sharp’
  3. Susceptible to artefacts
  4. Equipment more expensive
  5. More training to interpret, justify, operate
63
Q

CBCT benefits over CT (4)

A
  1. Lower radiation dose
  2. Potential for sharper image
  3. Cheaper
  4. Smaller footprint
64
Q

CT benefits over CBCT (3)

A
  1. Soft tissues better differentiated
  2. Cleaner images (better signal to noise ratio)
  3. Larger field of view possible
65
Q

CBCT Common dental uses (4)

A
  1. 8s and ID canal
  2. Alveolar bone dimensions for implants
  3. Root canal morphology
  4. Cystic jaw lesions
66
Q

Drawbacks of 3D volume reconstruction from CBCT (2)

A
  1. Can create misleading images
  2. Poor at showing thin bone
67
Q

FOV

A

Field of view

68
Q

Voxel size for CBCT

A

Never as small as intraoral radiographs

69
Q

How does voxel size impact radiation dose

A

Decreased voxel size, increased radiation dose

70
Q

How does voxel size impact scan time

A

Decreased voxel size, increased scan time

71
Q

What are voxels

A

3D pixels

72
Q

How much more irradiated are patients for a CBCT compared to a panoramic

A

~2-3x

73
Q

Types of artefacts of CBCT (2)

A
  1. Movement
  2. Streak
74
Q

CBCT Movement artefacts (2)

A
  1. Affects whole scan
  2. Leads to general blurriness or extra contours
75
Q

What causes streak artefacts in CBCT

A

High attenuation objects like metals

76
Q

Main issues with streak artefacts in CBCT (2)

A
  1. Can prevent caries assessment in adjacent teeth
  2. Prevents assessment of root canals in adjacent teeth
77
Q

Contra-indications for CBCT (5)

A
  1. If plain radiographs are sufficient
  2. Soft tissue evaluation
  3. Debilitating artefacts
  4. Pt unable to stay still
  5. Pt unable to fit in machine
78
Q

Radiographic lesion describing (7)

A
  1. Location
  2. Shape
  3. Margins
  4. Locularity
  5. Multiplicity
  6. Effect on surrounding anatomy
  7. Tooth condition
79
Q

Radicular cyst margins

A

Corticated and continuous with lamina dura of non-vital tooth

80
Q

Dentigerous cyst vs dental follicle (4)

A
  1. Consider cyst if > 5mm
  2. Assume cyst if >10mm
  3. Normal space 2-3mm
  4. Consider cyst if radiolucency asymmetrical
81
Q

Radiographic appearance of OKC (4)

A
  1. Often scalloped margins
  2. 25% multilocular
  3. Often displacement of teeth
  4. Characteristic expansion
82
Q

Cyst vs Incisive fossa (3)

A

<6mm assume fossa
6-10mm monitor
>10mm suspect cyst

83
Q

Why do we image salivary glands (3)

A
  1. Obstruction
  2. Swelling
  3. Dry mouth - to exclude Sjogrens
84
Q

Which area of which salivary gland can not be assessed by ultrasound

A

Deep lobe of parotid - MRI best

85
Q

Why is ultrasound good for salivary glands (5)

A
  1. Superficially positioned
  2. Parenchymal pattern
  3. Ductal dilation
  4. Vascularity
  5. Sialogogue
86
Q

Sialogogue

A

Citric acid to aid salivary flow which allows better visualisation of dilated ducts

87
Q

What is ultrasound (3)

A
  1. High frequency sound waves
  2. No ionising radiation
  3. Short wave length - not transmittable through air
88
Q

Types of salivary gland obstruction (3)

A
  1. Mucous plugs
  2. Salivary stones
  3. Neoplasia
89
Q

Salivary stones (2)

A

Sialoliths
More common in submandibular

90
Q

Salivary gland obstruction imaging protocol (3)

A
  1. Ultrasound
  2. Plain film (occlusal)
  3. Sialography
91
Q

Signs of obstructive disease (5)

A
  1. Dry mouth
  2. Prandial swelling and pain
  3. Rush of saliva into mouth
  4. Bad taste
  5. Thick saliva
92
Q

What percentage of sialoliths are submandibular

A

80%

93
Q

What percentage of submandibular stones are radiopaque

A

80%

94
Q

What is sialography

A

Injection of iodinated radiographic contrast into salivary gland to look for obstruction
(1-1.5ml)

95
Q

Indications for sialography (2)

A
  1. Checking for obstruction
  2. Planning for access for interventional procedures
96
Q

Risks of sialography (5)

A
  1. Discomfort
  2. Swelling
  3. Infection
  4. Allergy to contrast (rare)
  5. MRI alternative but no contrast needed
97
Q

Pus and sialography

A

If pus - antibiotics and postpone sialography

98
Q

Sialography normal findings (3)

A
  1. Parotid - tree in winter
  2. Submandibular - bush in winter
  3. If acinar changes - snow storm appearance
99
Q

How many images should be taken with sialography (3)

A
  1. 2 images
  2. Contrast phase with cannula in place
  3. Emptying phase - allows saliva to excrete contrast
100
Q

Sialography technical considerations (3)

A
  1. Contrast into oral cavity
  2. Air bubbles in tubing mimic filling defect
  3. Over filling (blushing)
101
Q

Interventional sialography (2)

A
  1. Not routinely done in Scotland
  2. Option in some cases rather than surgical removal of stone
102
Q

Selection criteria for salivary stone removal (2)

A
  1. Stone must be mobile
  2. Duct should be patent and wide to allow passage of stone
103
Q

Selection criteria for stone removal from submandibular gland

A

Located within lumen on main duct distal to posterior border of mylohyoid

104
Q

Selection criteria for stone removal from parotid

A

Located distal to hilum or at anterior border of gland

105
Q

Signs of Sjogrens on ultrasound (4)

A
  1. Atrophy
  2. Heterogenous parenchymal pattern (leopard print)
  3. Hypoechoic (darker)
  4. Fatty infiltration
106
Q

Scintiscan (3)

A
  1. Injection of radioactive technetium 99m
  2. Assess how well the glands are working
  3. Uptake into the glands if they are working well
107
Q

If neoplasia found on ultrasound what is the next step

A

Biopsy

108
Q

Low grade malignancy

A

Mimics benign lesions on ultrasound

109
Q

Signs of benign neoplasia on ultrasound (4)

A
  1. Well defined
  2. Encapsulated
  3. Peripheral vascularity
  4. No lymphadenopathy
110
Q

Signs of malignancy on ultrasound (4)

A
  1. Irregular margins
  2. Poorly defined
  3. Increased internal vascularity
  4. Lymphadenopathy
111
Q

SUMP

A

Salivary gland neoplasm of Unknown Malignant Potential

112
Q

Ultrasound for minor salivary glands (4)

A
  1. Only need if enlarged or pathological
  2. Ultrasound if superficial
  3. MRI if deeper or bony involvement
  4. Minor salivary glands tend to have higher chance of malignancy if pathological than major salivary glands
113
Q

When should MRI be considered after ultrasound (2)

A
  1. Vascular lesions
  2. Too large to be seen on ultrasound in completeness
114
Q

When would MRI be used for bony imaging

A

To check for changes in marrow

115
Q

CT beam shape

A

Fan shaped

116
Q

TMJ imaging (2)

A
  1. Internal derangement - MRI
  2. Degenerative - CBCT
117
Q

What view of MRI should be used for TMJ internal derangement

A

Para saggital

118
Q

Radionuclide for TMD (3)

A
  1. Check for activity of the joint
  2. Only used as screening method
  3. High sensitivity, low specificity
119
Q

H&N oncology imaging protocol (4)

A
  1. Cross sectional imaging with contrast (CT/MRI)
  2. Ultrasound guided biopsy of cervical lymphadenopathy
  3. PET/CT
  4. OPT for dental assessment pre radiotherapy
120
Q

MRI vs CT scan (3)

A
  1. MRI has no radiation
  2. MRI takes longer
  3. More contraindications for MRI
121
Q

What is and MRI better at assessing compared with CT (3)

A
  1. Perineural spread
  2. Bone invasion via bone marrow changes
  3. Soft tissue characteristics of lesion
122
Q

What does PET stand for

A

Positron emission tomography

123
Q

What is a PET scan (5)

A
  1. Radioactive fluorine labelled glucose injected
  2. Goes to metabolically active tissues
  3. Doesn’t give anatomical detail so overlaid onto CT or MRI
  4. Good for looking for unknown primary tumours
  5. Good for follow-up/recurrence
124
Q

Frankfort vs orbitomeatal (2)

A
  1. Frankfort for panoramics
  2. Orbitomeatal for skull views
125
Q

Where is the Y of Ennis usually found

A

Canine/Premolar area

BDS Finals (23 decks)

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