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radiology > salivary gland and ST imaging > Flashcards

salivary gland and ST imaging Flashcards

1
Q

reasons for imaging salivary glands

A

obstruction
dry mouth e.g. SS
swelling

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2
Q

causes of obstruction

A

mucous plugs
salivary stones/sialoliths
neoplasia - secondary obstruction

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3
Q

causes of swelling

A

obstruction
neoplastic mass
traumatic ranula
sialosis

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4
Q

properties of US

A

no ionising radiation

high freq sound waves - cannot be heard audibly

sound waves have short wavelength which are not transmittable through air - require coupling agent to help sound waves get into tissues - water-based gel

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5
Q

why is US good for salivary glands?

A

superficially positioned
can assess parenchymal pattern, vascularity, ductal dilatation or neoplastic masses
- also visualise nearby LNs
can give a sialogogue (ie citric acid) to aid saliva flow
- will allow better visualisation of dilated ducts

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6
Q

which part of which salivary gland cannot be visualised with US?

A

deep lobe of parotid (deep to ramus)

need CT/MRI

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7
Q

how US works

A

transducer uses Piezo-electric crystals
vibrates when electrical signal applied - produces high freq sound pressure waves - US
also works in reverse
produces echos which go back to crystals
- as they encounter different tissues in body
converted to image

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8
Q

interpreting US

A 
top skin surface, work deep
SC fat below skin
hypo echoic - black - muscles
hyper echoic - white - calcified stones
 - stops soundwaves passing through, get posterior shadowing behind calcified material
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9
Q

imaging protocol for salivary gland obstruction

A

1 - US
2 - plain film (mandibular true occlusal)
- e.g. if clear obstructive history but US not clear, see potential salivary stone on US
3 - sialography
- if considering mucous plug
- look for strictures

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10
Q

obstructive disease symptoms

A 
meal time symptoms
 - chewy, citrus, sour = worse
prandial swelling and pain
"rush of saliva into mouth" when swelling resolves
bad taste
thick saliva
dry mouth
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11
Q

usual aetiology of obstruction

A

sialolith (calcified stone) or mucous plug

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12
Q

what % of sialoliths are associated with the SM gland?

A

80%

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13
Q

what % of SM stones are radiopaque and what is the implication of this?

A

80%

see on US and plain film

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14
Q

what is sialography?

A

injection of iodinated radiographic contrast into salivary duct to look for obstruction
done either with panoramic, skull views (lat oblique or PA mandible) or fluoroscopic approach

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15
Q

what type of contrast is used for sialography?

A

iodinated

water-based, isoosmolar to cells of body

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16
Q

vol of contrast injected in sialography

A

v small 1-1.5ml

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17
Q

indications for sialography

A

looking for obstruction/stricture (narrowing) of salivary duct which could be leading mealtime symptoms

planning for access for interventional procedures (basket retrieval of stones or endoscopy)

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18
Q

risks of sialography procedure

A

discomfort
swelling
allergy to contrast
infection

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19
Q

risks of sialography procedure - discomfort

A

going against salivary flow so sore

up to 48hrs after

20
Q

risks of sialography procedure - swelling

A

up to 48hrs (if delayed release of saliva)

show pt how to milk gland to allow saliva flow - bimanual palpation

21
Q

risks of sialography procedure - allergy to contrast

A

v rare
check shellfish allergy
check if they have had contrast before e.g. CT scan
MRI alternative as no contrast is used

22
Q

risks of sialography procedure - infection

A

if pt attends with infection don’t proceed - give ABs and rebook

23
Q

normal findings sialography - parotid gland

A

tree in winter

24
Q

normal findings sialography - SM gland

A

bush in winter

25
Q

findings sialography - acinar changes

A

snowstorm appearance

e.g. SS or chronic sialadenitis

26
Q

sialography procedure

A

dilate duct orifice with probe/balloon dilator
insert catheter
inject contrast (small amount first to check no reflux)
take at least 2 images
- contrast phase with cannula in place - can see any blockages/ductal dilatation
- emptying phase with time delay - wait 5mins, drink water, allows gland to work and produce saliva to excrete contrast. if contrast left on emptying phase - shows chronic inflammation and no longer fully fct

27
Q

contrast phase

A

with cannula in place

can see any blockages/ductal dilatation

28
Q

emptying phase with time delay

A

wait 5mins, drink water
allows gland to work and produce saliva to excrete contrast
if contrast left on emptying phase - shows chronic inflammation and no longer fully fct

29
Q

interventional e.g. baskets indications

A

not routinely done in Scotland
option in some cases rather than SR of stone via incision or EO removal of salivary gland (GA and comorbidities)
can attempt to dilate structures

30
Q

disadvantages of interventional e.g. basket tx

A

can need multiple attempts and stenting to keep duct patent, may relapse
sometimes not possible due to extent of scarring from chronic infection - may have endoscopic investigation to see how much scarring

31
Q

selection criteria for stone removal

A

stone must be mobile
- if stone adherent to wall you could rip duct - ranula/post-op bleed
stone should be located within lumen on main duct distal to posterior border of mylohyjid (SMG)
stone should be distal to hilum (where gland opens into EG tissues) or at anterior border of the gland (parotid)
duct should be patent and wide to allow passage of stone - no stricture/narrowing distal to stone

32
Q

proximal

A

towards gland

33
Q

distal

A

towards duct orifice

34
Q

balloon dilatation

A 
removal of strictures
study
 - 87% technical success
 - clinical follow up
    = 56% complete resolution of symptoms
    = 36% some resolution 
    = 8% unchanged
35
Q

investigations for dry mouth (typically pts with suspected SS)

A

findings used in correlation with other investigations and clinical findings

  • blood tests (autoantibodies)
  • Schirmer test
  • sialometry (measure of saliva flow)
  • labial gland biopsy
36
Q

Scintiscan

A

nuclear medicine technique - injection of radioactive Technetium 99m
assess how well the glands are working
uptake into the glands if they are working well

37
Q

SS changes on US

A 
atrophy - shrunk and ill-defined
heterogenous parenchymal pattern (leopard print)
hypo echoic (darker)
fatty infiltration
  • chance for MALT lymphoma to develop
38
Q

swelling 1st line investigation

A

US to rule out obstruction or neoplasia
take measurements
assess for peripheral or internal vascularity
irregular ill-defined likely malignant

39
Q

if neoplasia suspected what is required ?

A

biopsy
FNA for cytopathological diagnosis
if inconclusive/suspect lymphoma - core biopsy for histopathological diagnosis
US guided biopsy - often take 2 passes to ensure adequate tissue sample

if suspect malignancy do neck scan to check cervical LNs

40
Q

pleomorphic adenoma on US

A

usually mixed tumours
- solid areas - light grey
- cystic change - black
posterior enhancement - shows mass mostly cystic

41
Q

ST imaging

A 
US 1st line
 - possible biopsy if required
MRI considered for further investigation
 - vascular lesions
 - too large/deep to be seen on US in completeness
42
Q

what is a ranula?

A

cystic cavity full of saliva

usually traumatic origin

43
Q

ranula on US

A

anechoic/v hypo echoic - v black
area of white posterior enhancement

need to work out size and relationship to mylohyoid to tell whether in sublingual or submandibular space

44
Q

imaging facial LNs

A

US good

45
Q

normal LNs on US

A

hypo echoic, well-defined
oval
8-10mm max short axis diameter

46
Q

LNs on US - be suspicious of…

A

round LNs more likely malignant

irregular/multiple in one region that appear close together or merged

47
Q

lipoma on US

A

within SC tissue
well-defined margin
internal hyper echoic striations - parallel to skin surface
a benign lipoma should have no internal vascularity

radiology (5 decks)

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