Other Imaging Modalities 1 Flashcards
Why do we image salivary glands?
Obstruction
-> neoplasia
-> mucous plugs- usually in parotid n
-> Salivary stones (sialoliths)
Dry mouth- sjogrens
Swelling- mumps, infection
Where are the major salivary glands located?
Parotid- pre auricular region
-> superficial lobe- close to skin
-> deep lobe- wraps around ramus
Submandibular- inferior to lower border of mandible (submandibular fossa)
Sublingual- on either side of intrinsic and extrinsic muscles of the tongue
Why is ultrasound good for looking at salivary glands?
Glands are superficially positioned
–> Apart from the deep lobe of the parotid (hidden deep to the
ramus)
Can assess parenchymal pattern, vascularity, ductal dilatation or neoplastic masses
Can give a sialogogue (ie citric acid) to aid saliva flow
–> Will allow better visualisation of dilated ducts
What is ultrasound?
No ionising radiation
High frequency short wavelength sound waves
–> Frequency that cannot be heard audibly
In simple terms how does ultrasound work?
Transducer directs waves into body- echoes return back and are converted into electric signals giving an image
Why does ultrasound require a coupling agent?
Not transmittable through air
–> Require coupling agent (gel) to help sound waves get into tissues
How are ultrasound images orientated?
Skin surface is at the top
-> as you go deeper into the body you move down the screen
How do glands appear on ultrasounds?
As a lighter shade of grey
Why does bone appear black on ultrasound?
Soundwaves cannot be transmitted through dense cortical bone and are stopped dead
What are the steps in the imaging protocol for salivary gland obstruction?
- Ultrasound
- Plain radiographs- mandibular true occlusal
- Sialography
What are the classical signs and symptoms of salivary gland obstruction?
“Meal time symptoms”
Prandial swelling and pain
“rush of saliva into the mouth”
Bad taste
Thick saliva
Dry mouth
What are the most common causes of salivary gland obstruction? Which imaging modalities are required?
Sialoliths- mostly in submandibular gland
-> 80% are calcified and therefore radiopaque- show up on plain radiographs
Mucous plugs- not calcified so need ultrasound
What is the term used in ultrasound for areas appearing darker?
Hypoechoic
How does ductal dilatation appear, what does it suggest?
As dark areas around gland- cause by obstruction
Why is it important to check the full duct structure when imaging salivary gland obstruction?
As there are often more than one stone
How do muscles appear on ultrasound?
Dark grey with white lines running across horizontally
How do stones appear on ultrasound?
Appear hyperechoic (White)
Lobulated appearance
Posterior shadowing present- tells us there are calcified structures within the gland itself
What is sialography?
Injection of iodinated radiographic contrast into salivary duct to look for obstruction (done with no LA)
Done either with Panoramic (DPT)/skull views (static) OR Fluoroscopic approach (see contrast going in in real time)
How much contrast is injected?
1-1.5ml
What are the indications for sialography?
Looking for obstruction or stricture (narrowing) of salivary duct -> could be leading meal time symptoms
Planning for access for interventional procedures (basket retrieval of stones or balloon dilatation of ductal strictures)
What are the contraindications for sialography?
Discomfort
Swelling
Infection- if pus reappoint in a week
Allergy to contrast (very rare- same contrast but lower dose than CT)
– MRI is alternative as no contrast used
Where do you inject the contrast into for each gland (Duct opening)?
Parotid duct- Buccal mucosa adjacent to upper 6
Submandibular/sublingual- either side lingual frenum in floor of the mouth
What is done by the patient between images in sialography?
They can rinse out
How do glands appear when injected with contrast normally?
Parotid gland- “tree in winter”
Submandibular gland- “ bush in winter”
If acinar changes– “snow storm appearance”
How can sialography be used to check function of gland?
Take 2 images:
Contrast phase with cannula in place
Emptying phase with time delay
-> Allows gland to work and produce saliva to excrete contrast.
How does obstruction appear in sialography?
Contrast doesn’t reach gland
-> appears as dark circle and ducts appear more dilated
How does stricture of gland ducts appear in sialography?
Sausage linking:
Areas of ductal dilation followed by very narrow parts
After emptying phase there will be a lot of contrast remaining
How is stricture of salivary gland ducts treated?
Gland removal
*Rarely- balloon dilation and stenting (likely to relapse due to scar tissue formation)
What sign indicates extravasated contrast in sialography?
Strange taste (occurs if canula too narrow or becomes dislodged)
Why is important that there is no air in syringe when injecting contrast in sialography?
As it can create air bubbles which appear like stones
-> potential misdiagnosis
What are the aspects of the selection criteria for stone removal surgery?
- Stone must be mobile
- Stone should be located within lumen on main duct distal to posterior border of mylohyoid (SMG)
- Stone should be distal to hilum or at anterior border of the gland (parotid)
- Duct should be patent and wide to allow passage of the stone
What is used as screening tool for sjogrens?
Ultrasound
What are the features of a gland affected by sjogrens on an ultrasound?
Lose outline of gland- in advanced stages it will be impossible to distinguish from other tissues
Dark hypoechoic regions in gland
Affects multiple glands- usually in pairs
Signs of atrophy
Heterogenous parenchymal pattern- leopard print
Fatty infiltration
Signs of MALT lymphoma
Which other investigations are used in diagnosis of Sjogrens?
Clinical findings
Blood tests (auto-antibodies)
Schirmer test – Sialometry
Labial gland biopsy
What is scintiscan and its function?
Injection of radioactive Technetium 99m
-> Assesses uptake to show how well the glands are working (no uptake suggests glands aren’t working)
What is the main issue with scintiscan ?
High radiation dose- other methods are preferred
What happens if a neoplastic swelling is found on ultrasound?
Fine needle aspiration for cytopathological diagnosis
Core biopsy for tissue histopathological diagnosis (used for lymphoma)
What are examples of benign salivary gland tumours?
Pleomorphic Adenoma
Warthins Tumour
What are the features of benign salivary gland tumours?
Well defined
Encapsulated- can draw around edge
Peripheral vascularity
No lymphadenopathy
What are examples of malignant salivary gland tumours?
Mucoepidermoid carcinoma
Acinic Cell Carcinoma
Adenoid Cystic Carcinoma
What are the features of malignant salivary gland tumours?
Irregular margins
Poorly defined
Increased/tortuous internal vascularity
Lymphadenopathy
What is the issue with low grade malignancy?
It mimics benign disease
-> this is why biopsy is always required
What is SUMP? (Provisional diagnosis)
Salivary gland neoplasm of unknown malignant potential
What is a ranula?
Cystic mass arising from submental gland
What is a lipoma? What are its features on ultrasound?
Benign fatty lump
-> Ovoid shape, fat striations (parallel to skin surface), no blood supply, dark
*If blood supply- liposarcoma (malignant)
When should MRI be considered for soft tissue imaging?
