Other Imaging Modalities Flashcards
sialolith
salivary stone
name 3 things that may cause obstruction of salivary glands
mucous plugs
sialoliths (stones)
neoplasm - either benign or malignant
why might salivary glands be imaged if a patient has dry mouth
in an attempt to exclude or confirm sjogrens disease
why does the anatomical position of salivary glands make them suitable for ultrasound imaging
they are superficial - external to the skeleton - except deep lobe of parotid which requires MRI imaging
sialogogue
substance that increases the flow rate of saliva e.g citric acid
briefly describe ultrasounds
they use no ionising radiation
They use sound waves that have a high frequency and short wavelength, a coupling agent e.g ultrasound gel is required to transmit the sound waves into tissues
Image displays skin at the top of image then down the image is deeper into the tissues
hyperechoic
white on ultrasound images
hypoechoic
dark areas on ultrasound
what radiograph is of most use is assessing for sialoliths in floor of mouth
mandibular true occlusal
symptoms of obstructive salivary gland ‘disease’
prandial swelling and pain (during/ relating to eating of food)
bad taste - salty
sudden rush of saliva into mouth
dry mouth - with no other sjogrens symptoms
thick mucous saliva
what gland is most commonly affected by sialoliths
submandibular
what is sialography
radiographic examination of the salivary glands - may involve injection of radiographic contrast into ducts/ glands
indications for sialography
looking for stricture (narrowing) or obstruction
planning for interventional procedures
risks of sialography (with contrast injection)
discomort (injection of contrast)
swelling
infection
allergy to contrast
normal radiograph risks
how many radiographs need to be taken when doing sialography with contrast medium
2
- one in contrast phase with cannula in place
- one in emptying phase - time delay, allows gland to work and produce saliva to excrete contrast (assess gland function)
what operator setup fault can result in false positives during sialography with contrast
air bubbles in tubing can mimic filling defects e.g stones
name 3 possible interventions for a patient with salivary stones (sialoliths)
- incision in FOM to remove stone
- gland removal
- dilation of strictures (possibly with stent too)
what is the characteristic pattern of sjogrens syndrome on an ultrasound
leopard print
scintiscan
historical test
injection of radioactive technetium - will be uptake into glands if functioning well
if salivary gland swelling of unknown cause what would first line investigation be
ultrasound to rule out obstruction or neoplasia
features of a benign salivary gland tumour on images
- well defined margins
- encapsulated
- peripheral vascularity
- no lymphadenopathy
features of a malignant salivary gland tumour (on an ultrasound)
- irregular margins
- poorly defined
- increased internal vascularity
- lymphadenopathy
are minor or major salivary glands at increased risk of malignant lesions
minor glands more likely to experience malignancy
what are CBCT images composed of
isotropic voxels - cubes of data with equal measurements of data in height width and depth
what tissue is CBCT not good for
soft tissues
discuss the differences between CBCT and CT
- shape of beam
- dose
- soft tissue contrast
- radiographic contrast
- patient positioning
- CBCT cone shape, CT fan shape
- CBCT lower dose
- CBCT poor soft tissue contrast, CT good
- CT radiographic contrast can be used if indicated
- CBCT patient upright or standing, CT patient horizontal
what imaging modality is gold standard for viewing articular disc of TMJ
MRI
MRI T1 weighted vs T2 weighted
T1 - good for anatomy, fat appears white, cortical bone appears black
T2 - fat and fluid white, bone black
what is internal derangement
disc displacement (With or without reduction)
SPECT
imaging modality that can be used for assessment of condyles
(single photon emission CT)
highly sensitive but low specificity therefore only a screening method
what imaging modalities are best for assessing cancer in head and neck
MRI or CT
CT vs MRI
- radiation dose
- waiting time
- contraindications
MRI has no radiation dose
MRI takes longer to acquire
More contraindications for MRI - claustrophobia, pacemakers, cochlear implants
what is PET
positive emission tomography
radioactive fluorine labelled glucose injected which goes to metabolically active tissues
Does not give anatomical detail so is overlaid on a CT or MRI
highly sensitive but low specificity
movement of tongue and vocal chords can cause false positives
