Radiology Flashcards
1
Q
What type of current do X-Ray producers need
A
Direct current
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
3
Q
Inverse Square Law - Radiology
A
The further the patient stands from the X-ray beam, the lower the dose
4
Q
Parallax
A
An apparent change in the position of an object caused by a real change in the position of the observer
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
6
Q
X-Ray attenuation (2)
A
Reducing in number of photons within beam
Result of absorption and scatter
7
Q
What colour are areas on an X-Ray with complete attenuation
A
White
8
Q
How can scatter be reduced
A
Reduction of area irradiated also called collimation
9
Q
What is the absorbed radiation dose measured in
A
Greys
10
Q
What is the effective radiation dose measured in
A
Sieverts
11
Q
What guidelines govern radiology (2)
A
Ionising Radiation and Medical Exposure Guidelines (IRME)
Ionising Radiation Regulations (2017)
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)
13
Q
How is a film radiographic image produced (6)
A
Development
Rinsing
Fixation
Removing
Washing
Drying
14
Q
What is KVP (2)
A
Peak Kilovoltage
Max voltage applied across X-ray tube
15
Q
How does an increase in voltage effect scatter
A
Increases scatter
16
Q
Film radiograph too dark
A
Overexposed
Developer left on too long
17
Q
How often should radiology equipment be tested
A
Daily
18
Q
How is a panoramic radiograph formed?
A
Simultaneous movement of beam and image receptor
19
Q
DPT
A
Dental Panoramic Topograph
20
Q
DPR
A
Dental Panoramic Radiograph
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
22
Q
Focal trough
A
The layer of tissues in focus
23
Q
What must be done prior to panoramic radiograph
A
All metal objects removed
24
Q
Reference plane for panoramic radiograph
A
Frankfort plane
25
Angulation of panoramic radiograph
Upwards at 8 degrees due to curve of monson
26
Where should the vertical canine line be on a panoramic radiograph
On the upper canines
27
Limitations of panoramic radiology (5)
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
28
Positioning difficulties for panoramic radiology (3)
Class II Div 1
Class III
Very young/very old
29
Panoramic - Patients canines behind canine guide line (3)
1. Closer to source than machine expects
2. Image magnified horizontally
3. Beam too slow
30
Panoramic - Patients canines in front of canine guide line (3)
1. Further from source than machine expects
2. Beam too fast
3. Teeth reduced in width
31
Common ghost images (4)
1. Earrings
2. Metal restorations
3. Anatomical features
4. Soft tissue calcifications - lymph nodes, salivary calcifications
32
Position of ghost images (3)
1. Always higher due to angulation
2. Horizontally magnified
3. Usually further forward
33
Digital receptors (2)
1. Phosphor plate
2. Solid-slate sensor
34
Film Receptors (2)
1. Direct action
2. Indirect action
35
Size 0 Receptor
Anterior periapicals
36
Size 2 Receptor
Bitewings
Posterior periapicals
37
Size 4 Receptor
Occlusal Radiographs
38
Appearance of dentinogenesis imperfecta on radiographs
Sclerosis (thinning) of root canals
39
Types of skull radiograph (4)
1. Occipitomental
2. Postero-anterior mandible
3. Reverse Towne's
4. True lateral skull
40
What area is mainly assessed by occipitomental radiographs
Midface
41
What area is mainly assessed by postero-anterior mandible radiographs
Posterior mandible excluding condyles
42
Reference line used for most skull radiographs
Orbitomeatal line
43
Angles for occipitomental radiographs (4)
0
10
30
40
44
How would facial fractures be assessed with radiographs (2)
1. Occipitomental
2. Typically 2 angles used
45
OM Radiograph Positioning (4)
1. Face towards receptor
2. Orbitomeatal line 45 degrees to receptor
3. 0 degrees - beam central/perpendicular to receptor
4. Nose-chin position
46
Why is a PA mandible radiograph not suitable for viewing facial skull
Superimposition of skull base
47
Fractures that indicate an OM radiograph (5)
1. Le fort
2. Zygomatic complex
3. Naso-ethmoidal complex
4. Orbital blow out
5. Coronoid process (not fracture)
48
Fractures that indicate PA mandible radiograph (4)
1. posterior third of body of mandible
2. Angles of mandible
3. Ramus
4. Low condylar necks
49
Other indications for PA mandible radiograph (2)
1. Mandibular hypo/hyperplasia
2. Maxillofacial deformities
50
PA mandible radiograph positioning (4)
1. Face towards receptor
2. Head tipped forward so orbitomeatal line perpendicular to receptor
3. Beam central and perpendicular
4. Forehead nose position
51
Why is x-ray projects from the posterior side of the head for skull radiographs (2)
Reduced magnification of face - less distortion of relevant features
Reduced effective dose for sensitive structures - lens
52
What is shown on a reverse Towne's radiograph
Condylar heads and necks
53
Indications for reverse Towne's radiograph (3)
1. High fractures of condylar necks
2. Intracapsular fractures of TMJ
3. Condylar hypoplasia/hyperplasia
54
How does a reverse Towne's differ from a PA mandible (2)
Mouth is open
Slightly different beam angle
55
Reverse Towne's positioning (4)
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
What does the pts mouth being open for reverse Towne's do to condylar heads
Moves condylar heads out of glenoid fossa
57
What does CBCT stand for
Cone beam computed tomography
58
What is CBCT
Cross sectional imaging suitable for assessing radio dense structures
59
What shape is the x ray beam in CBCT
Conical/Pyramidal
60
Head positioning for CBCT (2)
1. Unit dependant (sitting/standing/supine)
2. Head level with ground - frankfort
61
Benefits of CBCT over plain radiography (4)
1. No superimposition
2. Ability to view subject from any angle
3. No magnification/distortion
4. Allows for volumetric (3D) reconstruction
62
Disadvantages of CBCT over plain radiography (5)
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
CBCT benefits over CT (4)
1. Lower radiation dose
2. Potential for sharper image
3. Cheaper
4. Smaller footprint
64
CT benefits over CBCT (3)
1. Soft tissues better differentiated
2. Cleaner images (better signal to noise ratio)
3. Larger field of view possible
65
CBCT Common dental uses (4)
1. 8s and ID canal
2. Alveolar bone dimensions for implants
3. Root canal morphology
4. Cystic jaw lesions
66
Drawbacks of 3D volume reconstruction from CBCT (2)
1. Can create misleading images
2. Poor at showing thin bone
67
FOV
Field of view
68
Voxel size for CBCT
Never as small as intraoral radiographs
69
How does voxel size impact radiation dose
Decreased voxel size, increased radiation dose
70
How does voxel size impact scan time
Decreased voxel size, increased scan time
71
What are voxels
3D pixels
72
How much more irradiated are patients for a CBCT compared to a panoramic
~2-3x
73
Types of artefacts of CBCT (2)
1. Movement
2. Streak
74
CBCT Movement artefacts (2)
1. Affects whole scan
2. Leads to general blurriness or extra contours
75
What causes streak artefacts in CBCT
High attenuation objects like metals
76
Main issues with streak artefacts in CBCT (2)
1. Can prevent caries assessment in adjacent teeth
2. Prevents assessment of root canals in adjacent teeth
77
Contra-indications for CBCT (5)
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
Radiographic lesion describing (7)
1. Location
2. Shape
3. Margins
4. Locularity
5. Multiplicity
6. Effect on surrounding anatomy
7. Tooth condition
79
Radicular cyst margins
Corticated and continuous with lamina dura of non-vital tooth
80
Dentigerous cyst vs dental follicle (4)
1. Consider cyst if > 5mm
2. Assume cyst if >10mm
3. Normal space 2-3mm
4. Consider cyst if radiolucency asymmetrical
81
Radiographic appearance of OKC (4)
1. Often scalloped margins
2. 25% multilocular
3. Often displacement of teeth
4. Characteristic expansion
82
Cyst vs Incisive fossa (3)
<6mm assume fossa
6-10mm monitor
>10mm suspect cyst
83
Why do we image salivary glands (3)
1. Obstruction
2. Swelling
3. Dry mouth - to exclude Sjogrens
84
Which area of which salivary gland can not be assessed by ultrasound
Deep lobe of parotid - MRI best
85
Why is ultrasound good for salivary glands (5)
1. Superficially positioned
2. Parenchymal pattern
3. Ductal dilation
4. Vascularity
5. Sialogogue
86
Sialogogue
Citric acid to aid salivary flow which allows better visualisation of dilated ducts
87
What is ultrasound (3)
1. High frequency sound waves
2. No ionising radiation
3. Short wave length - not transmittable through air
88
Types of salivary gland obstruction (3)
1. Mucous plugs
2. Salivary stones
3. Neoplasia
89
Salivary stones (2)
Sialoliths
More common in submandibular
90
Salivary gland obstruction imaging protocol (3)
1. Ultrasound
2. Plain film (occlusal)
3. Sialography
91
Signs of obstructive disease (5)
1. Dry mouth
2. Prandial swelling and pain
3. Rush of saliva into mouth
4. Bad taste
5. Thick saliva
92
What percentage of sialoliths are submandibular
80%
93
What percentage of submandibular stones are radiopaque
80%
94
What is sialography
Injection of iodinated radiographic contrast into salivary gland to look for obstruction
(1-1.5ml)
95
Indications for sialography (2)
1. Checking for obstruction
2. Planning for access for interventional procedures
96
Risks of sialography (5)
1. Discomfort
2. Swelling
3. Infection
4. Allergy to contrast (rare)
5. MRI alternative but no contrast needed
97
Pus and sialography
If pus - antibiotics and postpone sialography
98
Sialography normal findings (3)
1. Parotid - tree in winter
2. Submandibular - bush in winter
3. If acinar changes - snow storm appearance
99
How many images should be taken with sialography (3)
1. 2 images
2. Contrast phase with cannula in place
3. Emptying phase - allows saliva to excrete contrast
100
Sialography technical considerations (3)
1. Contrast into oral cavity
2. Air bubbles in tubing mimic filling defect
3. Over filling (blushing)
101
Interventional sialography (2)
1. Not routinely done in Scotland
2. Option in some cases rather than surgical removal of stone
102
Selection criteria for salivary stone removal (2)
1. Stone must be mobile
2. Duct should be patent and wide to allow passage of stone
103
Selection criteria for stone removal from submandibular gland
Located within lumen on main duct distal to posterior border of mylohyoid
104
Selection criteria for stone removal from parotid
Located distal to hilum or at anterior border of gland
105
Signs of Sjogrens on ultrasound (4)
1. Atrophy
2. Heterogenous parenchymal pattern (leopard print)
3. Hypoechoic (darker)
4. Fatty infiltration
106
Scintiscan (3)
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
If neoplasia found on ultrasound what is the next step
Biopsy
108
Low grade malignancy
Mimics benign lesions on ultrasound
109
Signs of benign neoplasia on ultrasound (4)
1. Well defined
2. Encapsulated
3. Peripheral vascularity
4. No lymphadenopathy
110
Signs of malignancy on ultrasound (4)
1. Irregular margins
2. Poorly defined
3. Increased internal vascularity
4. Lymphadenopathy
111
SUMP
Salivary gland neoplasm of Unknown Malignant Potential
112
Ultrasound for minor salivary glands (4)
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
When should MRI be considered after ultrasound (2)
1. Vascular lesions
2. Too large to be seen on ultrasound in completeness
114
When would MRI be used for bony imaging
To check for changes in marrow
115
CT beam shape
Fan shaped
116
TMJ imaging (2)
1. Internal derangement - MRI
2. Degenerative - CBCT
117
What view of MRI should be used for TMJ internal derangement
Para saggital
118
Radionuclide for TMD (3)
1. Check for activity of the joint
2. Only used as screening method
3. High sensitivity, low specificity
119
H&N oncology imaging protocol (4)
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
MRI vs CT scan (3)
1. MRI has no radiation
2. MRI takes longer
3. More contraindications for MRI
121
What is and MRI better at assessing compared with CT (3)
1. Perineural spread
2. Bone invasion via bone marrow changes
3. Soft tissue characteristics of lesion
122
What does PET stand for
Positron emission tomography
123
What is a PET scan (5)
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
Frankfort vs orbitomeatal (2)
1. Frankfort for panoramics
2. Orbitomeatal for skull views
125
Where is the Y of Ennis usually found
Canine/Premolar area
