Type of test Nuclear medicine
Normal findings
Normal function of the salivary gland; no tumor or duct obstruction
Test explanation and related physiology
The ability of the epithelial cells of the salivary glands to trans port large pertechnetate ions from the blood and to secrete them into the saliva provides the principle for imaging the salivary glands. The functional capabilities, structural integrity, and location of the glands can be assessed. Usually, the parotid gland alone is visualized. Occasionally, the submandibular glands can be seen.
Indications for salivary gland nuclear imaging include patients with the following:
• Xerostomia (dry mouth)
• Pain
• Tumors
• Possible parotid duct obstruction
By following the radionuclide immediately after injection, blood flow can be evaluated. In about 10 minutes after injection, gland function becomes obvious by uptake of the radionuclide into the gland. Five to 10 minutes later, one should see secretion of nuclear material into the mouth. Washout demonstrates complete salivary gland excretion. Usually the patient is asked to suck on a lemon to encourage rapid washout. This test can indicate inflammation, hypofunction, the location and character of tumors, and duct obstruction.
Contraindications
• Patients who are pregnant unless the benefits outweigh the risks Interfering factors
• Rinsing the mouth before study may reduce excretion.
Procedure and patient care
Before
* Explain the procedure to the patient. See p. xviii for radiation exposure and risks.
* Tell the patient that no specific preparation is necessary.
• Make certain that the patient does not receive any thyroid blocking agents within 48 hours of testing.
During
• Tc-99m pertechnetate is injected into the antecubital vein.
• Dynamic planar images are obtained immediately.
• Repeat images are obtained every 3 to 5 minutes for a total of 15 to 20 minutes.
• Three-dimensional images are often obtained by using single photon emission computed tomography (SPECT)/computed tomography (CT) imaging.
• Administer a salivary gland stimulant after completion of static images. Either lemon juice or a lemon slice should be swished in the mouth and then expectorated.
• Washout images are obtained 5 to 10 minutes after the salivary gland stimulant. The thyroid gland is included for reference or comparison.
After
* Assure the patient that the dose of radioactive technetium used in this test is minute and therefore harmless. No isolation or special urine precautions are needed.
Abnormal findings
- Sjögren syndrome
- Benign mixed tumors or pleomorphic adenomas
- Malignant lesions (e.g., adenocarcinomas, squamous cell carcinomas, undifferentiated and mixed carcinomas)
- Salivary duct obstruction
