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
