eRadiograph Volume 7: Imaging of Oral Cavity | Page 323

Submandibular duct obstruction:
Due to the high mucous content and viscous nature of secretions of submandibular
gland it is prone to develop calculi. 85% of all salivary gland calculi occur in the
submandibular duct. Most of these calculi are radio opaque (80–90%) thus easily
demonstrated on radiographs/CT. Sonography may also demonstrate calculi as small
as 3 mm. The calculi are visualized in the submandibular duct as it courses through the
sublingual space. The submandibular duct may be dilated due to a stricture also. This
may occur due to a calculus, recurrent infection, autoimmune disease or trauma.
Sialography is a useful technique to demonstrate strictures and dilated ducts. MRI
using steady state, half fourier single shot echo turbo spin echo sequences is very
useful in demonstrating ducts and associated pathology. Its performance is
comparable to sialography.
Neoplasms
It is difficult to diffrentiate benign from malignant salivary gland neoplasms.
Features suggestive of benign are T2 hyperintensity, however mucoepidermoid,
adenocystic CA are hyperintense. Most high grade neoplasms are hypointense,
however, Warthins, the second most common benign tumor is hypointense so there is
an overlap in signal intensities. Most salivary glands require a preoperative FNAC to
determine their histology as there is a significant overlap in signal intensities unless
there are frank signs of malignancy such as bone invasion, perineural spread, deep
extension into parapharyngeal space or muscles, infiltrative margins.
Minor salivary glands are distributed within the mucosa of the oral cavity, palate,
paranasal sinuses, pharynx, larynx, trachea and bronchi.

Lipomas: Usually occur along the posterior aspect of the neck, rarely along the
anterior aspect or deep in the facial region such as the infratemporal fossa, oral cavity,
larynx or tonsil. These are well defined encapsulated ma 72