RADIOLOGY - salivary gland imaging Flashcards
where does the parotid gland lie?
in the preauricular and retromandibular region
extends anteriorly
lies over the masseter muscle
where does the parotid duct lie?
passes from the main gland across the masseter
through the buccal fat pad to pierce the buccinator to form the duct orifice in buccal mucosa adjacent to maxillary molars
where does the submandibular gland lie?
in the submandibular fossa
deep on the lingual aspect of the body of the mandible
wraps inferior into the submandibular space
where does the submandibular duct lie?
extends from the submandibular gland
passes between the mylohyoid and hyoglossus muscles
extends anteriorly in the FOM to form the duct orifice at the lingual frenum
where do the sublingual glands lie?
in the sublingual fossa in the anterior FOM
duct orifice is (shared with the submandibular gland) at the lingual frenum
where do you find minor salivary glands?
within the mucosa of the oral cavity overlying hard and soft palate, retromolar pad, and FOM
when would minor salivary glands be visible on imaging?
if pathological changes present
why do we image salivary glands?
obstructions: mucous plug, salivary stones, neoplasms
dry mouth: sjogrens related/ radiotherapy changes
swelling: hx of swelling secondary to obstruction or bacterial/ viral infection/ malignancy
what imaging modalities can we use for imaging salivary glands?
plain radiographic techniques
ultrasound
injection of iodinated contrast (sialography)
CT (computed tomography)
MRI (magnetic resonance imaging)
nuclear medicine
what is the imaging protocol for salivary gland obstruction?
begin with a plain film or ultrasound
in practice, you may take a plain film then refer to supplement with an ultrasound
in hospital, you may take an ultrasound and supplement with a plain film
then sialography depending on what is found
what type of plain film radiographs are used to image salivary gland obstruction?
lower true occlusal
OPT
lateral oblique
why are true laterals and PA mandible not very useful when imaging salivary gland obstruction?
superimposition of anatomical structures
why do sialoliths have a heterogenous appearance with ill defined radiolucent areas?
due to the lay down of calcified products over time
what are other calcifications that can be mistaken for sialoliths?
tonsilloliths (tonisl stones)
phleboliths (calcifications in venous structures)
calcified plaques (atheromas) in carotid artery
normal anatomy (hyoid bone)
elongated/ calcified stylohyoid ligament
calcified lymph nodes
where do you find tonsil stones?
in tonsillar crypts
how may tonsil stones appear on DPT?
superimposed calcifications over the ascending ramus - no radiolucent halo
what may phleboliths look like on imaging?
target with concentric rings of radiolucency and radiopacity
how may atheromas present on DPT?
lie at level of bifurcation of the carotid artery
at C3/4 cervical vertebrae
lie lateral to hyoid bone
who may you find calcified lymph nodes in?
pts with a history of tuberculosis/ sarcoidosis or malignancy
- chronic inflammation
what is ultrasound?
high frequency sound waves
no ionising radiation
why is a coupling agent required for ultrasound?
sound waves have a short wave length which are not transmittable through air
the coupling agent helps sound waves get into tissues
how does ultrasound work?
transducer emits and detects sound waves/ echoes
transducer creates sound waves when electric current is given to crystals on transducer surface
sound waves enter body and reflect back to transducer when boundaries between different tissues are met
using speed of sound and time to return the echo, the tissue depths are calculated and the ultrasound unit creates a 2D image
what does hypoechoic mean in relation to ultrasound?
dark
what does hyperechoic mean in relation to ultrasound?
bright
what does homogenous mean in relation to ultrasound?
uniform density
what does heterogenous mean in relation to ultrasound?
mixed density
why is ultrasound good for salivary gland imaging?
glands are superficially positioned
can assess parenchymal pattern, vascularity, ductal dilatation or neoplastic masses
of all salivary glands, what gland is not superficially positioned?
the deep lobe of the parotid - it is hidden deep to the ramus
what is parenchymal pattern?
homogenous or heterogenous
what can be given to aid saliva flow prior to ultrasound?
sialogogue (citric acid)
list symptoms of obstructive salivary gland disease?
meal time symptoms
prandial swelling and pain
rush of saliva into mouth
bad taste
thick saliva
dry mouth
aetiology of obstructive salivary gland disease?
sialolith/ mucous plug
what gland is mucous plugging more common in?
parotid
what percentage of sialoliths are associated with the subman gland?
80%
what percentage of submandibular stones are radiopaque?
80%
why may we perform sialography?
for further demonstrating of ductal structure
to rule out strictures
what is sialography?
injection of iodinated radiographic contrast into salivary duct to look for obstruction
what imaging modalities are used for sialography?
panoramic (DPT)
skull views (rotated PA mandible + lateral oblique)
fluoroscopic approach
is LA needed for sialography?
no
what volume of contrast is injected for sialography?
0.8-1.5ml
what are indications for sialography?
looking for obstruction/ stricture (narrowing) of salivary duct which could be leading to meal time symptoms
planning access for interventional procedures (basket retrieval of stones/ balloon dilatation of ductal strictures)
what are the risks of sialography?
discomfort
swelling
infection
any stone could move
allergy to contrast (very rare)
what is an alternative to sialography if the pt is allergic to the contrast?
MRI sialography
- heavy T2W scan
- gets rid of all tissues apart from fluid
what type of sialography is used to image salivary glands?
fluoroscopic
what must staff wear during fluoroscopic sialography?
lead aprons due to the increased dose
what is the approach for fluoroscopic sialography so that only contrast is seen?
subtraction approach
what are the phases of sialography?
- pre contrast
- contrast filling
- emptying
describe the pre contrast sialography phase?
not always done at the time of sialogram
exclude other pathology which could account for symptoms e.g., odontogenic pathology
use as a base line
describe the contrast/ filling phase of sialography?
contrast has been injected via canula
describe the emptying phase of sialography?
roughly 5 minute time delay following removal of the canula
contrast should have emptied from the gland and duct into the oral cavity (if normal functioning gland)
features of the contrast used for sialography?
iodine based
aqueous rather than oil based
iso-molar
e.g., omnipaque
what are normal findings for salivary glands undergoing sialography?
parotid gland “tree in winter” (thick main duct and narrowings of 2nd and 2rd ductal structures)
submandibular gland “bush in winter”
if acinar changes - “snow storm appearance”
when may there be acinar changes?
chronic inflammation and ductal dilatation
sjogrens
what does a sausage like appearance of a gland imply?
a pin point stricture - chronic sialadenitis secondary to stricture
with sialography, what does ductal dilatation with no contrast in the gland imply?
total stricture of duct
on a sialogram emptying phase, the filling defect has moved anterior and there is nearly complete removal of contrast. what does this imply?
mobile obstruction
what are technical consideration in sialography?
contrast into oral cavity if too much pressure
air bubbles, which then appear the same as small defects
over-filling “blushing” - pt will feel alot of pressure
is sialography used as intervention?
not routinely in Scotland
it is an option in some cases rather than surgical removal of stone view incision or EO removal of gland
can attempt to dilate strictures of the duct
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 (parotid)
- duct should be patent and wide to allow passage of the stone
what study looked at the success rate of balloon dilatation and what were the results?
Brown et al (1997)
technical success - 87%
complete resolution on follow up - 56%
some improvement on follow up - 36%
unchanged - 8%
what are other tests are used alongside imaging (typically ultrasound) for sjogrens?
blood tests (autoantibodies)
schirmer test
siolometry
labial gland biopsy
what appearance is likely to be seen on an ultrasound in which sjogrens is present?
- atrophy
- heterogenous parenchymal pattern (leopard print)
- hypoechoic (darker)
- fatty infiltration
what are sjogrens pts at risk of developing?
MALT lymphoma
what may lymphoma present as in the parotid gland?
very hypoechoic
no internal vascularity
well defined margins
what is the lead modality for imaging sjogrens?
ultrasound
is sialography used for sjogrens?
has been done historically
still apart of the European diagnostic criteria checklist
what are the increasing levels of sjogrens severity seen on imaging?
stage 1 - punctate
stage 2 - globular
stage 3 - cavitation
stage 4 - destructive
what is scintigraphy and what material is used?
intravenous injection of radioactive technetium 99m pertechnetate (half life 6 hours)
gamma camera used to gain images
what is scintigraphy used for?
assess how well the glands are working
uptake into the glands if they are working well
what will tumours present like under sctinigraphy?
reduced uptake
*apart from warthins tumour
what is the 1st line imaging technique to rule out obstruction or neoplasia?
ultrasound
if suspected neoplasm found on ultrasound, what is then required?
a biopsy
- FNA for a cytopathological diagnosis
- core biopsy for tissue histopathological diagnosis
give an example of a benign salivary gland tumour?
pleomorphic adenoma
warthins tumour
describe a benign salivary gland tumour?
well defined
encapsulated
peripheral vascularity
no lymphadenopathy
give an example of a malignant salivary gland tumour?
mucoepidermoid carcinoma
acinic cell carcinoma
adenoid cystic carcinoma
describe a malignant salivary gland tumour?
irregular margins
poorly defined
increased vascularity/ tortous internal vascularity
lymphadenopathy
when may you use MRI for salivary gland imaging?
useful for pre-surgical assessment and deep margins of lesions that may not be seen on ultrasound
try to do before a biopsy as inflammatory appearances will appear on the scan which may complicate diagnosis
if you have to take MRI before biopsy for salivary gland imaging, how long should you wait?
2 weeks
what is SUMP?
salivary gland neoplasm of unknown malignant potential - a provisional diagnosis
what type of imaging is used for minor salivary glands?
ultrasound if superficial
MRI if deeper or possible bony involvement
