Other Imaging Modalities Flashcards
Why do you image the salivary glands?
Obstruction
–mucous plugs
–salivary stones (sialoliths)
–neoplasia (masses, benign or malignant)
Dry Mouth
Swelling
Why is ultrasound used for salivary glands?
Glands are superficially positioned
Can assess parenchymal pattern (assesses chronic damage), vascularity (acute infection), ductal dilation (duct obstruction) or neoplastic masses
Can give a sialagogue (i.e. citric acid) to aid saliva flow (better visualisation of dilated ducts)
What is ultrasound?
How does it work?
No ionising radiation
High frequency sound waves
Require coupling agent to help sound waves get into tissues (ultrasound gel)
As the waves hit through different densities they reflect back onto the transducer and the length of time it takes for this travel back to the transducer creates the images and depth
What is the imaging protocol for Salivary Gland Obstruction?
Ultrasound to assess gland
Plain film (mandibular true occlusal)
Sialography (dependent on what other investigations show)
What are the symptoms of obstructive disease?
‘Meal time symptoms’
–swelling and pain
Prandial swelling and pain
‘Rush of saliva into the mouth’
Bad taste (typically salty)
Thick saliva
Dry mouth with no other symptoms suggesting sjogrens
What is sialography?
Injection of iodinated radiographic contrast into salivary duct to look for obstruction
Done either with panoramic, skull views or fluoroscopic approach
Very small volume of contrast injected (1-1.5ml) with no LA
Assess a narrowing or strictures of the ducts
What are the risk of sialography?
Discomfort (pressure of contrast being placed in the ducts)
Swelling (resolves within 24-48 hours)
Infection (obvious acute infection, pus from site- do not perform sialogaphy)
What are the normal appearances of the parotid and submandibular gland?
What is the appearance if there are acinar changes?
Parotid gland- tree in winter
Submandibular gland- bush in winter
Acinar changes- snow storm appearance
What are the technical considerations
Contrast into oral cavity (if the cannula is too small for the duct orifice)
Air bubbling in tubing (can mimic filling defects)
Over-filling ‘blushing’ (patient usually experiences discomfort or swelling if this occurs)
What is the selection criteria for stone removal?
Stone must be mobile (if it is adhered to duct can perforate the duct wall)
Stone should be located with lumen on main duct distal to posterior border of mylohyoid muscle
Stone could be distal to hilum or at anterior border of the gland
Duct should be patent and wide anteriorly to allow passage of the stone
What are scintiscans?
Injection of radioactive technetium 99m
Assess how well the glands are working
Uptake into the glands if they are working well
Scintiscan checks for gland function
What does the ultrasound look for in patients with dry mouth?
Atrophy
Heterogenous parenchymal pattern (leopard print)
Hypoechoic (darker) with areas of focal gland destruction
Fatty infiltration
When is an MRI used?
Pre-surgical assessment and deep margins of lesions that may not be seen on ultrasound
Try to do before biopsy
–inflammatory appearances will appear on the scan which may complicate diagnosis
What is used for minor salivary glands?
Ultrasound if superficial
MRI is beneficial if deeper or possible bony involvement
Only need to image if enlarged or pathological
What is CBCT?
Low dose multi-planar imaging
Images made up of isotropic voxels
-Cubes of data with equal measurements in height, width and depth
-Look at images in 3 planes (axial, coronal and sagittal)
