Radiology Flashcards
What does ionising radiation do?
Turns atoms into ions by knocking away electrons orbiting the nucleus
How much eV does each ionisation deposit?
35eV
What is are the direct effects of radiation on DNA?
Radiation interacts with the atoms of a DNA molecule or another important part of the cell
What are the indirect effects of radiation on DNA?
Radiation interacts with water in the cell producing free radicals which cause damage
What is the usual outcome for a single strand DNA damage?
Usually repaired
What is the usual outcome for double strand damage?
Sometimes repaired
May be faulty repair —> leads to mutations that affect cell function
What are the biological effects of radiation dependent on?
Type of radiation
Amount of radiation (dose)
Time over which the dose is recieved
Type of tissue/cell type irradiated
What is tissue radio sensitivity dependent on?
Function of the cells that make up tissues
If the cells are actively dividing (increased division = increased risk)
Which tissues are highly radiosensitive?
Bone marrow
Lymphoid tissue
Gastrointestinal glands
Gonads
Embryonic tissue
What tissues are moderately radiosensitive?
Skin
Vascular endothelium
Lungs
Lens of eye
What tissues are least radiosensitive?
Central nervous system
Bone and cartilage
Connective tissue
What are the three outcomes of DNA mutation?
Mutation repaired = viable cells
Cell death = unviable cells
Cell survives but is mutated = cancer
What is the absorbed dose?
Measurement of the energy deposited by radiation
Measures in Grays (Gy)
What is the equivalent dose?
Absorbed dose x weighting factor
Measured in Sieverts (Sv)
What is the equivalent dose of alpha?
20 Sv
What is the equivalent dose of beta, gamma and X-rays?
1 sV
What is the risk of cancer with a dose of 1mSv?
1 in 20,0000
What is the risk of cancer with an intra-oral x-ray?
1 in 10,000,000
What are the determinstic effects of radiation?
Tissue reactions (decreased bone marrow cells, cataract, sterility, hair loss)
Occur over certain (threshold) dose
Severity of effect related to dose
What are the stochastic effects of radiation?
The probability of occurence is related to dose received
Somatic: results in disease or disorder
Genetic: abnormalies in descendent
What are the effects of radiation during pregnancy?
Lethal potential with doses 100mGy before or immediately after after implantation of the embryo into uterine wall
During organogenesis >250mGy dose leads to growth retardation
What is the cancer risk in utero?
1 in 13,500 per 1mGy exposure
What is the effective dose of an intra-oral radiograph?
0.005mSv
What is the staff dose limit for body, skin and eyes?
Body: 20mSv
Skin/extremities: 500mSv
Eye: 20mSv
What is the minimum distance for staff from the X-ray machine?
1.5m
What percentage do circular collimators increase the dose by?
40%
What are the four factors of dose optimisation?
E speed or faster (film); fewer X-ray photons
KV range of 60-70kV
Fsd: >200mm
Rectangular collimation
What are the diagnostic reference levels in an adult for a digital sensor?
0.9mGy
What are the diagnostic reference levels in an adult for phosphor plates and film?
1.2mGy
What are the diagnostic reference levels in a child for a digital sensor?
0.6mGy
What are the diagnostic reference levels in a child with a phosphor plate and film?
0.7mGy
What are the two types of receptors?
Digital and Film
What are digital receptors made up of?
Phosphor plate
Solid state sensor
What are film receptors made of?
Direct action film
Indirect action film
How many shades of grey are in 8 bits?
256
What does DICOM stand for?
Digital Imaging and Communications in Medicine
What does PACs stand for?
Picture Archiving and Communication System
What are the two needs for radiographic localisation?
To determine location of a structure in relation to other structures
Only if clinical examination is insufficient to provide an answer
What are 5 clinical situations where radiographic localisation may be used?
Position of unerupted teeth
Location of roots/root canals
Relationship of pathological lesions
Trauma
Soft tissue swelling
What is required for radiographic localisation?
2 views required
Views should be at right angles in their projection geometry
Aid of opaque objects
What is the rule for parallax?
Same
Lingual
Opposite
Buccal
What is the definition of parallax?
An apparent change in the position of an object caused by a real change in the position of the observer
What are the uses of radiographs?
Diagnosis
Treatment planning
Monitoring
What is the difference between radiology and radiography?
Radiology is a specialty of medicine
Radiography is an imaging technique
What does ALARA stand for?
As Low As Reasonably Practitionable
What is the main risk of dental radiology?
Carcinogenesis
What does IRR 2017 stand for?
Ionising Radiation Regulations 2017
What does IR(ME)R stand for?
Ionising Radiation (Medical Exposure) Regulation
What are some examples of justifications for radiographs?
Caries detection
Investigating infection
Orthodontic planning
What are the principles for radiographic protection?
Justification
Optimisation
Dose Limitation
What is processing in radiology?
Conversion of a latent image to a permanent visible image
Either digitally or chemically
What is the kV of a dental machine?
60-70kV
What are the three interactions with matter?
No effect
Complete absorption
Absorption and scatter
What is the receptor size for an anterior periapical?
0
What is the receptor size for a posterior periapical?
2
What is the receptor size for a bitewing?
2
What is the receptor size for an occlusal?
4
What side of the receptor should face the X-ray beam?
Blank side
What can be used to orientate a bitewing?
Curve of Spee
What are the specific attenuation interactions?
Photoelectric effect: complete absorption
Compton effect: partial absorption and scattering
When does the photoelectric effect take place?
Occurs when the energy of the incoming photon is equal to or just greater than the binding energy of an inner shell electron
What does the photoelectric effect result in?
Prevents X-ray photons from reaching the receptor- leads to lighter area on radiograph
What is the formula for the probability of the photoelectric effect?
Pe= p x Z3 / E3
P= proportion to physical density
Z3= cubed atomic number
E3= photon energy cubed
What is E3 affected by?
KV
What is the Z3 of lead?
551,368
What is the dose of a Periapical or Bitewing?
5uSV
What is the dose of a maxillary occlusal radiograph?
8
What is the dose of a lat cephalogram?
3
When does the Compton effect occur?
Energy of proton is much greater than binding energy of the electron
What do recoil electrons do?
Ionise and cause potential damage to adjacent tissues
Which photons cause forward scatter?
Higher energy
Which photons cause back scatter?
Lower energy
What does forward scatter present as
Darkening or fogging
What factors are associated with the probability of the Compton effect?
Independent of Z
Weakly proportionate to photon energy
Proportionate to density of material
What is the effect of collimation?
Decreased irradiated surface area
Decreased volume of irradiated tissue
Decreased number of scattered photons in tissue
Decreased scattered photons interacting with receptor
Decreased loss of contrast on image
What is the effect of lowering the kV?
Lower x-ray tube potential difference (kV)
Overall lower photon energy produced
Increased photoelectric interaction
Increased contrast between tissues with different Z (good)
Increased absorbed dose (bad)
What is electomagnetic radiation?
Flow of energy created by simultaneously varying electrical and magnetic fields
What are the features of electromagnetic radiation?
No mass
No charge
Travels at speed of light
Can travel in a vacuum
What is frequency in regard to EM waves?
How many waves per unit time
Measured in Hertz
What is speed in regard to EM waves?
Speed= frequency x wavelength
What is eV?
Energy gained by one electron moving across a potential difference of one volt
What are x ray photon energies?
124eV-124keV
What is amps?
How much charge flows past a point per second
What is current?
Flow of electrical charge
What is voltage?
Difference in electrical potential between two points in an electrical field
Synonymous with potential difference
What is the annual background radiation dose?
2.2mSv
How can dose be limited in radiology?
Rectangular collimation
High kVp
Digital/fast film screens
What are the roles in taking radiographs?
Referrer
Operator
Practitioner
Employer
What are the roles in taking radiographs?
Referrer
Operator
Practitioner
Employer
What does the referrer do?
Requests exposure
What does the operator do?
Take the radiograph
What does the practitioner do?
Decides if the exposure is justified
What is the focal trough?
Layer in patient containing structures of interest
Affected by distance, X-ray beam width
How do ghost images present?
Opposite side of
Horizontally stretched
Higher
How are X-rays produced?
Rapid deceleration of electrons fired at high speed and collide, releasing kinetic energy which is converted into EM radiation and heat
How can Compton scatter be reduced?
Collimation
Lead foil lining packers
How can absorbed dose be decreased?
Using higher energy electrons
What are the benefits of digital radiographs?
Faster
Digital manipulation
No physical space
What are the disadvantages of digital radiographs?
Poorer resolution
Takes up data
What are lateral cephalograms for?
Standardised and reproducible true lateral views of the facial bones
What does an intensifying screen result in?
Less photons
Reduced dose
What are the stages of radiograph development?
Develop
Wash
Fix
Wash
Dry
What are the requirements for localisation?
Stable reference point
Horizontal /vertical tube shift
What is the angle of a panoramic radiograph?
8 degrees
What are examples of common abnormalities that can be seen on a radiograph?
Caries
Periodontal diseases/lesions
Impacted teeth
Hypodontia
Skeletal relationships
What are examples of uncommon abnormalities that can be seen on a radiograph?
Jaw lesions such as cysts and tumours
Supernumeraries
Foreign bodies
What does the term jaw lesions describe?
Cysts
Benign neoplasms
Cancers
Developmental abnormalities
Reactive lesions
Genetic conditions
What are the seven factors in lesion description?
Site
Size
Shape
Margins
Internal structure
Effect on adjacent anatomy
Number
What factors should be considered when discussing the site of a radiographic lesion?
Where is it?
Is there a notable relationship to another structure?
What is its position relative to a particular structure?
What factors should be considered when discussing the size of a radiographic lesion?
Measure (estimate) dimensions
Describe the boundaries
What factors should be considered when discussing the shape of a radiographic lesion?
General: rounded, scalloped, irregular
Locularity: unilocular, pseudolocular, multilocular
What descriptions should be considered when discussing the margins of a radiographic lesion?
Well defined and corticated
Well defined and non corticated
Poorly defined and blending into the adjacent normal anatomy
Poorly defined and ragged or moth eaten
What does a corticated lesion suggest?
Benign lesion
What does a moth eaten lesion suggest?
Malignancy
What descriptions should be considered when discussing the internal structure of a radiographic lesion?
Entirely radiolucent
Radiolucent with some radiopacity
Radiopaque (homogenous or heterogenous)
What factors should be considered when discussing the internal structure of a radiographic lesion?
Amount- scant, multiple, dispersed
Bony septae; thin/coarse, prominent/faint, straight/curved
Particular structure: enamel and define radio density
What can cause radiolucency in jaw lesions?
Resorption of bone
Decreased mineralisation of bone
Decreased thickness of bone
Replacement of bone with abnormal less mineralised tissue
What can cause radiopacity in jaw lesions?
Increased thickness of bone
Osteosclerosis of bone
Presence of abnormal tissue
Mineralisation of normally non-mineralised tissues
What factors should be considered when discussing the involvement of tooth of a radiographic lesion?
Around apex/apices
At side of root
Around crown
Around entire tooth
What is the effect of jaw lesions on teeth?
Displacement/impaction
Resorption
Loss of lamina dura
Widening of pdl space
Hypercementosis
What is the effect of jaw lesions on bone?
Displacement of cortices
Perforation of cortices
Sclerosis of trabecular bone
What is the effect of jaw lesions on the inferior alveolar canal/ maxillary sinus/nasal cavity?
Displacement
Erosion
Compression
What factors should be considered when discussing the number of a radiographic lesion?
Single
Bilateral
Multiple
What do multiple jaw lesions suggest?
Syndrome
What are the potential causes of a periapical radiolucency?
Periapical granuloma
Periapical abscess
Radicular cyst
Perio-endo lesion
Cemento-osseous dysplasia (in early stage)
Surgical defect (following peri-radicular surgery)
Fibrous healing defect (following resolution of lesion)
Ameloblastoma occurring next to tooth
What features should be considered when facing a periapical radiolucency?
Clinical symptoms and signs
Condition of tooth, periodontal condition, treatment history
Patient demographic
What can happen to infected cysts over time?
Can lose their well-defined, corticated margins
Can mimic radiographic features of malignancy
Check for signs of secondary infection- pain, swelling, purulent exudate
What are some examples of not uncommon radiopacities?
Idiopathic osteosclerosis
Sclerosis osteitis
Hypercementosis
Buried retained roots
What is idiopathic osteosclerosis?
Localised area of increased bone density of unknown cause
Asymptomatic
Discuss the incidence of idiopathic osteosclerosis
6% population
Presents in adolescents
Commonly affects premolar region of mandible
What is the radiographic presentation of idiopathic osteosclerosis?
Well defined radiopacity- often homogenous without radiolucent margin
Variable shapes- round, elliptical, irregular
Usually <2cm
Not associated/ not affecting teeth
What is sclerosis osteitis?
Localised area of increased bone density in response to inflammation
May be symptomatic due to inflamamtion
What is the radiographic presentation of sclerosis osteitis?
Well defined or poorly defined radiopacity
Variable shape
Associated with infective source
How can we determine the difference between sclerosis and idiopathic osteosclerosis?
Look for signs/symptoms of infection
What is hyper cementosis?
Excessive deposition of cementum around root- non-neoplastic and asymptomatic, tooth usually vital
Unknown cause
Can make extractions more difficult
How does hypercementosis present on radiographs?
Single or multiple teeth involved
Homogenous radiopacity continuous with root surface
PDL space of tooth extends around periphery
Margins well defined and often smooth
Where is the greatest biting force generated?
Between 1st molars- greatest root area
What does the term clinical evaluation mean?
Covers the interpretation and documentation of any findings relevant to the patient’s management, treatment or prognosis
Covers the entire image
Must be recorded for every exposure and completed on the same day
What is the difference between a clinical evaluation and a radiograph report?
A radiograph report is more comprehensive
What are skull radiographs primarily used for?
Maxilofacial trauma
What types of maxilofacial trauma is not assessed using a skull radiograph?
Extensive/complex cases
What are examples of skull radiographs?
Occipitomental
Postero-anterior mandible
Reverse towne’s
True lateral skull
What is the main use of occipitomental radiographs?
Fractures of midface
What is the main use of a postero-anterior mandible radiograph?
Fractures of the posterior mandible (except condyles)
What is the main use of reverse towne’s radiograph?
Fractures of mandibular condyles
What is the main use of reverse towne’s radiograph?
Fractures of mandibular conduces
What is the x-ray machine like for skull radiographs?
Has a specialised skull unit
Patient positioned either standing up (erect) or lying on back (supine)
What is the receptor like for skull radiographs?
Digital and larger enough to capture relevant areas
What is the orbitomeatal line?
Reference line used in patient positioning for skull radiographs
What is the orbitomeatal line also known as?
Canthomeatal line or radiographic baseline
What are the landmarks for the orbitomeatal line?
Outer canthus of eye
Centre of external auditiory meatus
What do occipitomental radiographs show?
Facial skeleton (avoiding superimposition of skull base)
Can be taken at different angles
What are the indications for occipitomental radiographs?
Middle third fractures-
Le Fort I, II, III
Zygomatic complex (inc arch)
Naso-ethmoidal complex
Orbital blow out
Coronoid process fractures
How is an occipitomental radiograph positioned?
Face towards receptor
Head tipped back so that orbitomeatal line is 45 degrees to receptor.
Where should the X-ray Beam be positioned in a 0 degree OM?
Perpendicular to receptor and centred through occiput
Where should the x-ray beam be positioned in a 30 degree occipitomental?
30 degrees above perpendicular line to receptor and centred through lower border of orbit
Why is the postero-anterior radiograph not suitable for viewing facial skeleton?
Superimposition of base of skull and nasal bones
What are the indications for a postero-anterior radiograph?
Lesions and fractures involving: posterior third of body, angles, rami, low condylar necks
Mandibular hypoplasia/hyperplasia
Maxilofacial deformities
How is the patient positioned for an antero-postero radiograph?
Head tipped forward so that the orbitomeatal line is perpendicular to the receptor
How is the X-ray beam positioned for a postero-antero radiograph?
Perpendicular to receptor and centred through cervical spine at the level of rami
Why is the X-ray beam positioned posteriorly in a posterio-antero radiograph?
Reduces magnification of face (since close to receptor): less distortion of relevant structures, back of skull will be more magnified as a result but this is less important
Reduced effective dose: X-ray beam partly attenuated by back of skull before reaching face, lower radiation dose to radiosensitive tissues (lens of eye) as a result
What does a reverse Townes radiograph show?
Condylar heads and necks
What is the difference between an antero-postero and a reverse Townes?
Reverse Townes has a slightly different xray beam angle and the mouth is open
What are the indications for a reverse Townes radiograph?
High fractures of condylar necks
Intracapsular fractures of TMJ
Condylar hypoplasia/hyperplasia
What is the positioning for a reverse Townes radiograph?
Face towards the receptor
Head tipped forward so orbitomeatal line is perpendicular to receptor (forehead nose)
Mouth open
Why is the mouth open during a reverse Townes radiograph?
Moves condylar heads out of glenoid fossa
How is the xray beam positioned for a reverse Townes radiograph?
30 degrees below perpendicular line to receptor and centred through condyles
What is cone beam computed tomography?
A form of cross-sectional imaging that is used to assess radiodense structures
What are examples of non-DMFR used of CBCTs?
Temporal bone imaging
Paranasal sinus imaging
Orthopaedic imaging
Radiotherapy planning
What are the basic principles of CBCT?
Ionising radiation:
Conical/pyramidal x-ray beam and square digital receptor rotate around the head
What is the maximum beam rotations for a CBCT scan?
1
How does a CBCT scan work?
Captures many 2 dimensional images which are reconstructed into a cylindrical 3D image
What are the examples of unit types for CBCT?
CBCT only
CBCT + panoramic +/- ceph
What is the patient positioning for CBCT?
Sitting or standing (depending on unit)
Rarely supine
What is the head positioning for CBCT?
Same as panoramic:
Horizontal: Frankfort plane
Vertical: midsaggital line
What are the benefits of CBCT over plain radiography?
No superimposition
Ability to view subject from any angle
No magnification/distortion
Allows for volumetric (3D) reconstruction
What are the downside of CBCT over plain radiography?
Increased radiation dose to patient
Lower spatial resolution
Susceptible to artefacts
Equipment more expensive (initial, running and maintainance)
Images more complicated to manipulate and interpret
Requires additional training (to justify, operate and interpret)
What are the main benefits of CBCT in comparison to conventional CT?
Lower radiation dose
Potential for ‘sharper’ images
Cheaper (initial, running and maintenance costs)
Smaller footprint
What are the main benefits of conventional CT opposed to CBCT?
Able to differentiate soft tissues better
Cleaner images (better signal to nose radio)
Larger field of view possible
What are the common uses of CBCT in dentistry?
Clarifying relationship between impacted mandibular third molar and inferior alveolar canal prior to intervention (after a plain RG has suggested a possible close relationship)
Measuring alveolar bone dimensions to help plan implant placement
Visualising complex root canal morphology to aid endodontic treatment
Investigating external root resorption next to impacted teeth (if not clear on plain RG)
Assessing large cystic jaw lesions and their involvement of important anatomical structures
What are the common orthogonal planes?
Axial
Sagittal
Coronal
What are the uses of 3D volume reconstruction?
May help clinician to picture the extent/shape of disease
Can be an informative teaching aid for the patient
What are the drawbacks of 3D volume reconstruction?
It is a modified reconstruction of the data and so can create misleading images
When should imaging factors/variables be set for CBCT?
Before the scan starts
Should be considered case-by-case using ALARP
What are examples imaging factors/variables?
Field of view
Voxel size
Acquisition time (e.g. 10 seconds)
What is the field of view?
The size of the captured volume of data
What does an increased field of view lead to?
Increased radiation dose
Increased number of tissues irradiated
Increased scatter
What is voxel size?
The image resolution
What are voxels?
3D pixels
What is the comparison between CBCT and radiograph pixels?
IO radiograph pixels are smaller
What does decreased voxel size lead to?
(Indirectly) leads to increased radiation dose
Increased scan time
What is the typical range of options for voxel size in CBCT scans?
0.4mm3-0.085mm3
What imaging factors suit an endodontic case?
FOV as small as possible, unless there is large apical pathology
Small voxel size
What imaging factors suit an implant case?
FOV depends on number/position of implants
Larger voxel size
What does the radiation dose depend on in CBCT?
Equipment
Size of FOV
Position of FOV
Voxel size
What is the approximate dose for a CBCT?
13-82 uSv
What is the approximate effective dose for a CT?
474-1160 uSv
What is the approximate effective dose for panoramic radiographs?
3-24 uSv
What is the approximate dose for an intraoral radiograph?
4uSv
What are artefacts?
Visualised structures on the scan that were not present in the object investigate
What are the 2 main types of artefacts?
Movement artefacts
Streak artefacts
When does a movement artefact occur?
If the patient is not completely still during the full exposure
What are the features of a movement artefact?
Affects whole scan
Can lead to blurriness or extra contours
Typically reduced using fixation aids
What are examples of fixation aids?
Chin rest
Head strap
What are streak artefacts caused by?
High attenuation objects (metals)
What are the main issues with streak artefacts?
Can prevent caries assessment adjacent to restorations
Can prevent assessment of perforations/missed canals in RCT teeth
What are the contra-indications for CBCT?
If plain radiographs are sufficient
Pathology requiring soft tissue visualisation: malignancy, infection spreading in soft tissue
If high risk of debilitating artefacts
Patient factors; unable to stay still, unable to fit in machine
Why may a patient be unable to stay still in the CBCT machine?
Parkinson’s disease
Learning difficulties
Uncooperative child
Why may a patient be unable to fit in the CBCT machine?
Kyphotic patient (curving of the spine that causes bowling/rounding of back)
Unfavourable neck-shoulder ratio (obese, body builder)
What is the justification for CBCT scan?
Must be preceded by a clinical exam
Only if plain radiography unable to provide sufficient information
Why do we image salivary glands?
Obstuction- mucous plugs, salivary stones (sialoliths) and neoplasia
Dry mouth
Swelling
What are the benefits of ultrasounds for salivary glands?
Glands are superficially positioned (apart from deep lobe of parotid)
Can assess parenchymal pattern, vascularity, ductal dilatation or neoplastic masses
Can give a sialigogue (i.e. citric acid) to aid saliva flow
Where is the deep lobe of the parotid positioned?
Deep to the ramus
What are the benefits of a sialogogue?
Allow better visualisation of dilated ducts
What is ultrasound?
No ionising radiation
High frequency sounds waves- cannot be heard
Sound waves have short wave length which are not transmittable through air- require coupling agent
What is the imaging protocol for salivary gland obstruction?
Ultrasound
Plain film (mandibular true occlusal)
Sialography
What are the symptoms of obstructive salivary gland disease?
Meal time symptoms
Prandial swelling and pain
‘rush of saliva into mouth’
Bad taste
Thick saliva
Dry mouth
What is the aetiology of salivary gland obstruction?
Sialolith or mucous plug
What % of sialoliths are associated with the submandibular gland?
80%
What % of submandibiular stones are radiopaque?
80%
What is sialography?
Injection of iodinated radiographic contract into salivary duct to look for obstruction
Done with Panoramic (OPT), skull views or fluoroscopic approach
Very small volume injected (1.0-1.5ml)
What are the indications for sialography?
Looking for obstruction or stricture (narrowing) of salivary duct which could be leading meal time symptoms
Planning for access for interventional procedures (basket retrieval of stones or endoscopy)
What are the risks of sialography?
Discomfort
Swelling
Infection
Allergy to contrast
What are the normal findings of sialography?
Parotid gland- tree in winter
Submandular gland- bush in winter
If acinar changes- snow storm appearance
What are the 2 images to be taken in sialography?
Contrast phase with cannula in place
Emptying phase with time delay- allows gland to work and produce saliva to excrete contrast
What are the technical considerations which taking a sialography?
Contrast into oral cavity
Air bubbles in tubing
Over filling- blushing
What are examples of intervention treatments for sialoths?
Basket retrieval
Ductal dilatation
What is the selection criteria for stone removal?
Stone must be mobile
Stone should be located within lumen on main duct distal to posterior border of mylohyoid
Stone should be distal to hilum or at anterior border of the gland
Duct should be patent and wide to allow passage of the stone
What is the technical success rate of balloon dilatation in sialoths?
87%
What investigations can be carried out for patients with dry mouth?
Blood tests (auto-antibodies)
Schirmer test
Sialometry
Labialk gland biopsy
What are you looking for when investigating dry mouth in a sialography?
Atrophy
Heterogenous parenchymal pattern (leopard print)
Hypoechoic (darker)
Fatty infiltration
What is a scintiscan?
Injection of radioactive Technetium 99jm
Assesses how well the glands are working
Uptake in the glands if they are working well
What kind of biopsy is required for cytopathological diagnosis?
Fine needle aspiration
What kind of biopsy is required for histopathological diagnosis?
Core biopsy
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How would a benign tumour appear on an ultrasound?
Well defined
Encapsulated
Peripheral vascularity
No lymphadenopathy
How would a malignant tumour appear on an ultrasound?
Irregular margins
Poorly defined
Increased/tortous internal vascularity
Lymphadenopathy
What are examples of benign lesions?
Pleomorphic adenoma
Warthins Tumour
What are examples of malignant lesions?
Mucoepidermoid carcinoma
Acinic Cell Carcinoma
Adenoid Cystic Carcinoma
What are the benefits of MRI?
Useful for pre-surgical assessment and deep margins of lesions that may not be seen on ultrasound
What is SUMP?
Salivary Gland Neoplasm of Unknown Malignant Potential
What are the methods of bony imaging?
CBCT or CT
MRI to check for marrow changes
What is CBCT?
Low dose multi-planar imaging
Images made up from isotropic voxels; cubes of data with equal measurements, in three planes (axial, coronal and saggital), No distortion of images in any plane.
What are the features of CBCT?
Cone shaped beam
Low dose
Poor soft tissue contrast
Radiographic contrast not required
Patient sitting upright/standing
What are the features of CT?
Fan shaped beam
High dose
Good soft tissue contrast (windowing)
Radiographic contrast can be used if indicated
Patient lying horizontal
What is the effective dose of CBCT?
18-674 uSv
What is the effectove dose of a CT of facial bones?
430-860 uSv
What are the methods of TMJ imaging?
Myofascial- no imaging required
Internal derangement- MRI (GS) or ultrasound
Degenerative- CBCT
What can an MRI of internal derangement of the TMJ determine?
If with or without reduction and which direction the disc moves in relation to the condyle
Need to view para-sagittal and para-coronal
What are the features of radionuclide (SPECT)?
99mTc used
Check for activity of joint
High sensitivity, low specificity
Screening method only
What imaging techniques are used following history and examination of a H&N oncology patient?
Cross-sectional imaging with contrast: CT, MRI
Ultrasound guided biopsy of cervical lymphadenopathy
PET/CT
DPT for dental assessment prior to radiotherapy
What is the comparison between CT and MRI?
MRI has no radiation dose to patient
MRI scan takes longer
MRI has more contraindications- pacemakers, cochlear implants, claustrophobia
MRI better for assessing- perineural spread, Bone invasion via bone marrow changes, soft tissue characterisations of lesion
What is PET?
Positron Emission Tomography
Radioactive fluorine labelled glucose injected (18-FDG)
Goes to metabolically active tissues
Doesn’t give anatomical details (so overlaid onto CT or MRI)
Used for follow up and recurrence
