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BDS4 Radiology > Other Imaging Modalities 1 > Flashcards

Other Imaging Modalities 1 Flashcards

1
Q

Why do we image salivary glands?

A

Obstruction
-> neoplasia
-> mucous plugs- usually in parotid n
-> Salivary stones (sialoliths)

Dry mouth- sjogrens

Swelling- mumps, infection

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2
Q

Where are the major salivary glands located?

A

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

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3
Q

Why is ultrasound good for looking at salivary glands?

A

 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

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4
Q

What is ultrasound?

A

 No ionising radiation

 High frequency short wavelength sound waves
–> Frequency that cannot be heard audibly

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5
Q

In simple terms how does ultrasound work?

A

Transducer directs waves into body- echoes return back and are converted into electric signals giving an image

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6
Q

Why does ultrasound require a coupling agent?

A

 Not transmittable through air
–> Require coupling agent (gel) to help sound waves get into tissues

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7
Q

How are ultrasound images orientated?

A

Skin surface is at the top
-> as you go deeper into the body you move down the screen

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8
Q

How do glands appear on ultrasounds?

A

As a lighter shade of grey

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9
Q

Why does bone appear black on ultrasound?

A

Soundwaves cannot be transmitted through dense cortical bone and are stopped dead

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10
Q

What are the steps in the imaging protocol for salivary gland obstruction?

A
  1. Ultrasound
  2. Plain radiographs- mandibular true occlusal
  3. Sialography
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11
Q

What are the classical signs and symptoms of salivary gland obstruction?

A

 “Meal time symptoms”
 Prandial swelling and pain
 “rush of saliva into the mouth”
 Bad taste
 Thick saliva
 Dry mouth

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12
Q

What are the most common causes of salivary gland obstruction? Which imaging modalities are required?

A

Sialoliths- mostly in submandibular gland
-> 80% are calcified and therefore radiopaque- show up on plain radiographs

Mucous plugs- not calcified so need ultrasound

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13
Q

What is the term used in ultrasound for areas appearing darker?

A

Hypoechoic

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14
Q

How does ductal dilatation appear, what does it suggest?

A

As dark areas around gland- cause by obstruction

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15
Q

Why is it important to check the full duct structure when imaging salivary gland obstruction?

A

As there are often more than one stone

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16
Q

How do muscles appear on ultrasound?

A

Dark grey with white lines running across horizontally

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17
Q

How do stones appear on ultrasound?

A

Appear hyperechoic (White)

Lobulated appearance

Posterior shadowing present- tells us there are calcified structures within the gland itself

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18
Q

What is sialography?

A

 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)

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19
Q

How much contrast is injected?

A

1-1.5ml

20
Q

What are the indications for sialography?

A

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)

21
Q

What are the contraindications for sialography?

A

 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

22
Q

Where do you inject the contrast into for each gland (Duct opening)?

A

Parotid duct- Buccal mucosa adjacent to upper 6

Submandibular/sublingual- either side lingual frenum in floor of the mouth

23
Q

What is done by the patient between images in sialography?

A

They can rinse out

24
Q

How do glands appear when injected with contrast normally?

A

 Parotid gland- “tree in winter”

 Submandibular gland- “ bush in winter”

 If acinar changes– “snow storm appearance”

25
Q

How can sialography be used to check function of gland?

A

Take 2 images:
Contrast phase with cannula in place

Emptying phase with time delay
-> Allows gland to work and produce saliva to excrete contrast.

26
Q

How does obstruction appear in sialography?

A

Contrast doesn’t reach gland
-> appears as dark circle and ducts appear more dilated

27
Q

How does stricture of gland ducts appear in sialography?

A

Sausage linking:
 Areas of ductal dilation followed by very narrow parts
 After emptying phase there will be a lot of contrast remaining

28
Q

How is stricture of salivary gland ducts treated?

A

Gland removal

*Rarely- balloon dilation and stenting (likely to relapse due to scar tissue formation)

29
Q

What sign indicates extravasated contrast in sialography?

A

Strange taste (occurs if canula too narrow or becomes dislodged)

30
Q

Why is important that there is no air in syringe when injecting contrast in sialography?

A

As it can create air bubbles which appear like stones
-> potential misdiagnosis

31
Q

What are the aspects of the selection criteria for stone removal surgery?

A
  1. Stone must be mobile
  2. Stone should be located within lumen on main duct distal to posterior border of mylohyoid (SMG)
  3. Stone should be distal to hilum or at anterior border of the gland (parotid)
  4. Duct should be patent and wide to allow passage of the stone
32
Q

What is used as screening tool for sjogrens?

A

Ultrasound

33
Q

What are the features of a gland affected by sjogrens on an ultrasound?

A

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

34
Q

Which other investigations are used in diagnosis of Sjogrens?

A

Clinical findings

Blood tests (auto-antibodies)

Schirmer test – Sialometry

Labial gland biopsy

35
Q

What is scintiscan and its function?

A

 Injection of radioactive Technetium 99m
-> Assesses uptake to show how well the glands are working (no uptake suggests glands aren’t working)

36
Q

What is the main issue with scintiscan ?

A

High radiation dose- other methods are preferred

37
Q

What happens if a neoplastic swelling is found on ultrasound?

A

 Fine needle aspiration for cytopathological diagnosis

 Core biopsy for tissue histopathological diagnosis (used for lymphoma)

38
Q

What are examples of benign salivary gland tumours?

A

Pleomorphic Adenoma

Warthins Tumour

39
Q

What are the features of benign salivary gland tumours?

A

 Well defined
 Encapsulated- can draw around edge
 Peripheral vascularity
 No lymphadenopathy

40
Q

What are examples of malignant salivary gland tumours?

A

Mucoepidermoid carcinoma

Acinic Cell Carcinoma

Adenoid Cystic Carcinoma

41
Q

What are the features of malignant salivary gland tumours?

A

 Irregular margins
 Poorly defined
 Increased/tortuous internal vascularity
 Lymphadenopathy

42
Q

What is the issue with low grade malignancy?

A

It mimics benign disease
-> this is why biopsy is always required

43
Q

What is SUMP? (Provisional diagnosis)

A

Salivary gland neoplasm of unknown malignant potential

44
Q

What is a ranula?

A

Cystic mass arising from submental gland

45
Q

What is a lipoma? What are its features on ultrasound?

A

Benign fatty lump
-> Ovoid shape, fat striations (parallel to skin surface), no blood supply, dark

*If blood supply- liposarcoma (malignant)

46
Q

When should MRI be considered for soft tissue imaging?

A

BDS4 Radiology (8 decks)

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