Other imaging modalities Flashcards
What are the 3 salivary glands
- parotid
- submandibular
- sublingual
Where does the parotid sit
Sits in the periauricular region
Extends to angle of the mandible
Crosses masseter into buccal fat pad
Where is the orifice of the parotid
into buccal mucosa adjacent to first and second molars
How many lobes does the parotid gland have
Has a superficial + a deep lobe which sits medially
What is the predominant acini in the parotid gland
serous
Where does the submandibular gland sit
In the inferior border of the mandible
Sits lingual to the mandible in the submandibular fossa
What type of acini does the submandibular gland have
mixed
What type of acini does the sublingual gland have
mucous mainly
What are indications for imaging of salivary glands
- obstruction
- dry mouth
- swelling
What can cause obstructions of the salivary glands
- mucous plugs
- dry mouth
- swelling
What are salivary stones also known as
sialoliths
Where are mucous pligs most common
- Mucous obstructions are more common in the parotid glands despite it having mainly serous acini, cause is unknown
How can a neoplastic mass cause destruction
Benign/malignant tumour preventing saliva from entering the oral cavity
Why do we image for a dry mouth
Sjogren changes have a very characteristic appearance on an ultrasound
Why is ultrasound used on salivary glands
o The salivary glands are superficially positioned in exception of the deep lobe of the parotid which is hidden deep to the ramus and is not viewed on an ultrasound
o Can assess the parenchymal pattern, vascularity, ductal dilatation or neoplastic masses
o Can give a sialagogue (i.e citric acid) to aid salivary flow which will allow better visualisation of dilated ducts as at rest, dilatation is minimal
Why is ultrasound beneficial
does not utilise ionising radiation
How does ultraound work
- It uses high frequency sound waves which are not audible
- The sound waves have a short wavelength which are not transmittable through air and require a coupling agent to help sound waves get to tissues
- A gel is used to transmit the sound waves to the tissue
- Various body tissues conduct sound differently and some tissues absorb sound waves while other reflect them and the density of the tissues dictate the speed at which the echoes return
What is an ultrasound image called
a sonogram
What results in a black image
ultrasound
- When the sound waves easily travel through uniform substances such as water then no echoes are generated which results in a black image
What results in a white/grey image
ultrasound
When the sound waves encounter a tissue that absorbs/transmits the sound, a wave is reflected back to the probe which results in a white/gray image depending on the intensity of the reflection
What is the imaging protocol for salivary glands
- Ultrasound (due to no ionising radiation)
- Plain film (mandibular true occlusal) – especially if a submandibular stone is suspected
- Sialography
What are the signs and symptoms of obstructive disease
salivary gland
o Symptoms at mealtimes due to increase in saliva production close to mealtimes
o Prandial swelling and pain
o Bad taste (salty)
o Thick saliva
o Dry mouth
What is the aetiology of obstructive disease
salivary gland
o Sialolith or mucous plug
o 80% of salivary stones associated with submandibular gland
o 80% of submandibular stones are radiopaque
What would we expect to see on the ultrasound when obstruction is present
o Would expect to see ductal dilatation anterior to the obstruction
o Salivary stone will appear white as the stone is hyperechoic
Why does the salivary stone appear hyperechoic
It has a lobular surface
Sound waves hit the stones because of the level of the calcification and the sound waves are fully absorbed resulting in white with posterior shadowing
What is sialography
- It is the injection of iodinated radiographic contrast into salivary duct orifice to look for obstruction & strictures (narrowing)
- Done with either a panoramic (DPT), skull views or fluoroscopic approach
What is the fluoroscopic approach (sialography)
o Fluoroscopic approach allows direct visualisation of it going into duct structure but results in more radiation
Does sialography require LA
No
What happens if the contrast gets into the soft tissues
contrast is iso-osmolar (same osmolarity) and water based so if it goes into the soft tissues it will not cause a tissue reaction
What are the indications of sialography
o Looking for obstruction or stricture of salivary duct which could be leading to mealtime symptoms
o Planning for access for interventional procedures (basket retrieval of stones or balloon dilatation of ductal strictures)
What are the risks of sialography
o Discomfort (putting contrast against flow)
o Swelling
o Infection
o Allergy to contrast (very rare) – MRI is alternative as no contrast used
Why is infection a risk of sialography
Should not be used when there are signs of infection as it leads to the risk of pushing bacteria further into the gland which could result in an acute infection
Pus coming out of the gland means antibiotic and reappoint
What does the parotid gland resemble in a normal finding in sialography
a tree in winter
What does a submandibular gland resemble in a normal finding in sialography
bush in winter
If there are acinar changes, what would be seen on the sialography
snow storm appearance
seen in advanced sjogrens/sialonitis
How many images should be taken in sialography
2
o The first one should be in the contrast phase with the cannula in place
o The second one should be the emptying phase with time delay (5 minutes) to allow the gland to work and produce saliva to excrete contrast
What are technical considerations for sialography
o Don’t overfill the tube or use a cannula that is too small as can result in extravasated contrast
o The red arrow shows the result of contrast sitting in the floor of the mouth and has come flowing out from the cannula
o The yellow arrows show the result of air in the syringes causing small air locules in the contrast phase and can be misdiagnosed as stones
What are interventional options used for
salivary glands
o Not routine in Scotland
o Is an option for some cases where they are not suitable for an intra oral approach but also aren’t indicated yet for gland removal
What are the interventional salivary gland options
o Can try lithotripsy to break up stones
o Can attempt to dilate strictures (narrowing) of the duct (balloon dilatation)
What is the selection criteria for salivary gland stone removal
o Stone must be mobile
o Stone should be located within lumen on main duct distal to posterior border of mylohyoid
o Stone should be distal to hilum or at anterior border of the gland (parotid)
o Duct should be patent and wide to allow passage of the stone
What are signs of sjogrens on an ultrasound
o Atrophy
o Heterogenous parenchymal pattern (leopard print)
o Hyperechoic gland (darker)
o Fatty infiltration into the gland itself
Why should sjogren patients be routinely scanned if there is a swelling in the gland
there is a chance of MALT lymphoma developing
What is sciptiscan
o Consist of injection of radioactive technietium 99m
o It is another way of viewing the glands and assess how well the glands are working
o There will be uptake into glands if they are working well and will appear as if it is lit up
o Not done much now due to high radiation dose
What is the first line of imaging for salivary gland swelling
o Ultrasound is first line imaging technique to rule out obstruction or neoplasia
If neoplastic changes identified, what are the further investigations required
o Fine needle aspiration for cytopathological diagnosis
o Core biopsy for tissue histopathological diagnosis
What are the signs of a benign salivary gland tumour
o Well defined
o Encapsulated
o Peripheral vascularity
o No lymphadenopathy
What are the signs of a malignant salivary gland tumour
o Irregular margins
o Poorly defined
o Increased/tortous internal vascularity
o Lymphadenopathy
o Low grade malignancies can mimic benign ones so biopsy always required
What are examples of benign salivary gland tumours
pleomorphic adenoma or warthins tumour
What are examples of malignant salivary gland tumours
mucoepidermoid carcinoma
