Radiology - Other Imaging modalities Flashcards
Where is the parotid duct orifice located?
adjacent to the upper 1st/2nd permanent molar in the buccal mucosa
Where is the submandibular duct orifice located?
Adjacent to the lingual frenum
Where is the sublingual duct orifice located?
Adjacent to the lingual frenum
Why do we image salivary glands? (3)
- Obstruction;
* Mucous plugs
* Stones (sialoliths)
* Neoplastic mass – benign or malignant - Dry mouth
* Sjogrens syndrome associated changes - characteristic US appearance - Swelling
* Neoplastic
* Infection
* Mumps or other viral infection
Where are mucous plug obstructions more commonly found?
parotid gland
Why are ultrasounds used to image salivary glands? (3)
- Superficially positioned in the face (However Struggle to see the deep lobe as it wraps around the medial surface of the ramus)
- it can Assess parenchymal Pattern changes:
- Vascularity
- Ductal dilatation
- Neoplastic masses
- Can use to give a Sialogogue
- Stimulates saliva and improves imaging of dilated ducts (increased dilation)
What does ductal dilatation usually indicate?
obstruction
Briefly describe how ultrasounds work.
Uses high freq soundwaves (short waves) which are transmitted through tissues via a coupling agent (can’t transmit through air – must use gel)
What does hyperechoic mean on an US?
whiter areas
What does hypoechoic mean on an US?
darker areas
What is a bend in the salivary ducts called?
What is the implication of this?
hilum
stones can become obstructed here
What is the first line imaging method for the salivary gland?
why is this first line?
Ultrasound
- no radiation dose to px
(however in practice you may use a mandibular true occlusal for submandibular/sublingual areas as a first line since US may not be readily available)
What are the symptoms of obstructive disease of the salivary glands? (5)
- Mealtime symptoms (Thinking about or eating)
- Pressure
- Prandial Pain over salivary gland
- Prandial swelling
- Rush of saliva into the mouth once swelling gone (salty and thicker)
- Dry mouth
What are the symptoms of obstructive disease of the salivary glands? (5)
- Mealtime symptoms (Thinking about or eating)
- Pressure
- Prandial Pain over salivary gland
- Prandial swelling
- Rush of saliva into the mouth once swelling gone (salty and thicker)
- Dry mouth
What can cause obstructive disease of the salivary glands? (2)
Stones
mucous plugs
Why is the full ductal structure examined if a px is suspected/found to have salivary stones?
if a px has one salivary stone they likely have others elsewhere in the ductal system
What does posterior shadowing of the duct indicate?
There is a calcification present within the duct
What salivary stones can be assessed on an OPT? (2)
anterior parotid stones
submandibular stones
What is Sialography?
Where iodinated radiographic contrast is Injected through the ductal orifice into the salicary duct to look for obstruction
(third line investigation of the salivary glands)
What are the indications for sialography? (3)
- Find out what is causing the symptoms e.g. what is causing obstruction/narrow/stricture
- To assess gland function
- plan for intervention procedures e.g. basket retrieval or balloon dilatation
What radiographic imaging is sialography used alongside? (3)
- Panoramic = static view
- Skull views = static view
- Fluoroscopic approaches = dynamic (live) view
Describe the risks associated with sialography? (4)
- (even although No LA/Scalpel) Can feel discomfort as the contrast is being pushed in against the flow of saliva
Px will feel Pushing and pressure - Swelling
- No risk of infection however if there is infection we can’t complete the procedure it as it pushes bacteria back into the gland
If Pus present = short AB’s and reappoint for 1 weeks time - Risk of allergy to contrast (iodone based) low risk as it’s a small amount of contrast through the duct
What are the alternatives to sialography?
MRI
What are the advantages of sialogrpahy? (2)
No needles/LA
Patient can swallow contrast
Describe how a healthy parotid gland would look using sialography.
a tree in winter
Describe how a healthy submandibular gland would look using sialography.
a bush in winter
Describe what would be seen in a gland with acinar changes.
In what px’s would this be seen in?
Globular appearance of contrast
Seen in: Advanced sjogerens or chronic inflammation
When imaging sialography when do we need to take radiographs?
Take at least 2 images
1. Contrast phase (canula in place)
- emptying phase
(5 mins between each, after saliva cleared contrast)
During sialography, if the salivary stone changes position between the 2 radiographic images what does this indicate?
that intervention techniques can be used
When are intervention techniques used? (2)
- when we Can’t use intraoral methods of removal
- Px Not yet suitable for extraoral gland removal
What is the aim of intervention techniques?
dilate the duct strictures
List the criteria for stone removal via intervention techniques. (4)
- stone must be mobile
- stone should be located within the lumen in the main duct disatl to the post border of the mylohyoid
- stone should be distal to the hilum or at the ant border of the gland (parotid)
- duct should be patent and wide to allow passage
Is US used to diagnose sjogrens?
no - used alongside other tests (blood tests, labial gland biopsy, sialometry, Schirmer test)
When US a salivary gland with sjogrens what are we looking for? (4)
- Atrophy
- Heterogenous parenchymal pattern (leopard print)
- Hypoechoic (darker)
- Fatty infiltration
What are glands with sjogrens at risk of developing?
MALT lymphoma
How can we differentiate between chronic sialodenitis and sjogrens?
Chronic sialo = only affects one gland
Sjogren = affects more than one gland and usually in pairs
What is the first line imaging technique for swelling of the salivary glands?
ultrasound
What is the ultrasound criteria for a benign mass of the salivary gland? (6)
- Well defined
- Peripheral vascularity
- encapsulated
- No lymphadenopathy
- Sometimes Globulated
- Cystic components
Posterior enhancement – cystic content
What is the ultrasound criteria for a malignant mass of the salivary gland? (4)
- Irregular margins
- Poorly defined
- Increased/tortuous internal vascularity
- Lymphadenopathy present
Why is it sometimes beneficial to biopsy swellings which appear benign on a US?
Low grade malignancy mimics benign
What is the first line imaging technique for soft tissue lesions?
Ultrasound
When is MRI imaging used instead of ultrasound imaging when assessing soft tissue lesions? (2)
- when Lesions too large and too deep to be seen in completeness on US
- Vascular lesions
What imaging techniques do we use for imagine bony structures? (3)
- CBCT
- medical intervention CT = Soft tissues and muscles
- MRI – marrow changes (Doesn’t involve radiation)
What are advantages of using CBCT? (4)
- Low dose
- multiplanar imaging
- Images made up of Isotropic voxels = No distortion of the image (cubes of data have equal measurements)
- Can View CBCT in 3 different planes
Axial, Coronally, Sagittal
What are the highest and lowest fields of CBCT views?
What can each be used for?
17cm high = highest field of view
Used for: orthognathic surgery
5cm = smallest
Used for: isolated teeth, cysts and implant planning
Compare CBCT to CT (6)
CBCT:
* Cone shaped beam
* Lower dose
* Poor soft tissue contrast
* Radiographic contrast not needed
* Patient upright
* quicker (9 secs)
CT:
* Fan shapoed beam
* Higher dose
* Good soft tissue contrast:
Window scanning:
Can change views to see different densities/structures e.g. only bone and air
* Radiographic IV contrast can be used (to image malignancy)
* Patient horizontal
* Longer = up to 3 mins
Compare the dose of a Mid face CBCT (5-10cm) to a CT of facial bones.
CBCT = 18-674 uSv
CT = 430-860 uSv
Provide examples of pathological boney anatomy which is imaged using CBCT. (3)
- Cysts
- Odontogenic tumours
- MRONJ
What imaging is used to assess myofacial pain (TMJ dysfunction)?
none
What imaging is used to assess internal derangement (TMJ dysfunction)?
- Consider MRI if there are significant issue (US as an alternative if MRI contraindicated)
What imaging is used to assess degenerative changes (crepitus, osteoarthritis or joint replacement)?
CBCT
Describe the colour of tissues on a T1W MRI. (3)
- Fat is always white
- Bone is black
- fluid is black
Describe the colour of tissues on a T2W MRI. (3)
- Fat white
- Fluid white
- Bone black
What are T1W MRI’s useful for assessing?
Anatomy
What are T2W MRI’s useful for assessing?
pathology
What does an MRI of internal derangement tell you about the articular disc? (2)
- Determines if there is reduction or not
- Determines which direction the disc moves in in relation to the condyle
Describe the shape of a healthy articular disc.
bowtie shaped
What is a SPECT scan?
What is it used to assess?
single-photon emission computerized tomography
Use: assess activity of joint
Why is a SPECT scan only used for screening of joint disease?
High sensitivity but low accuracy = can identify increased activity however could be from; tumour, infection, inflammation or hyperplasia
If malignancy is suspected clinically, what imaging do we request? (2)
- CT = SCC
- MRI
(Depends on type of tumour suspected)
What imaging do we request if the primary tumour site is unknown?
PET CT
List the contraindications & px’s to be caution with when using MRI. (5)
- pacemaker
- cochlear implant
- Claustrophobic – panic button provided
Caution with:
- Tattoos (has metallic particles which can heat up and skin feels like its burning)
- Makeup and mascara metal particles within can heat up
What is the only contraindication of using CT?
allergy to the contrast
What are CT’s better for assessing? (5)
- Perineural spread
- Metastases
- Bone invasion
- subtle marrow changes
- Better ST characteristics of the lesion
Tumours light up with contrast (subtle grey changes)
Describe how PET CT works. (3)
radioactive fluorine labelled glucose injected
- Liquid goes to metabolically active tissues i.e. tumours as they have metabolic activity and growing tumours need glucose
- Must be superimposed on to CT/MRI (and PET) as PET alone doesn’t give anatomical detail
