Salivary gland scan

The Salivary Gland Scan, also known as Radionuclide Sialography, is a non-invasive nuclear medicine test that evaluates the functional activity of the major salivary glands, namely the parotid and submandibular glands. Unlike traditional anatomical imaging, this scan provides valuable insights into how well these glands produce and secrete saliva, which is essential for diagnosing a wide range of salivary gland conditions. This imaging technique uses a radiotracer, most commonly 99mTechnetium-pertechnetate (99mTc-pertechnetate), which is absorbed by the salivary glands and excreted into the oral cavity. The scan tracks the uptake and excretion pattern of the radiotracer over time, giving clinicians real-time data on glandular function, ductal obstruction, and secretory efficiency.

Why is a Salivary Gland Scan Performed?

A Salivary Gland Scan is typically recommended in cases where patients experience unexplained salivary gland dysfunction or are preparing for therapies that may affect gland function. It is a preferred choice when structural imaging like ultrasound or CT fails to reveal the underlying cause of symptoms.

Common Indications for Salivary Gland Scan:

• Unexplained obstruction or reduced saliva production (xerostomia)
• Evaluation of traumatic damage to salivary glands following surgery or radiation
• Salivary duct obstruction without an obvious stone or tumor
• Detection of aplasia or hypoplasia of salivary glands
• Monitoring function before radionuclide therapies, such as 177Lu-PSMA therapy
• Assessment of chronic inflammatory conditions like Sjogren’s syndrome
• Follow-up after sialolithiasis treatment
• Differentiation between obstructive and inflammatory pathologies

How Does the Salivary Gland Scan Work?

This nuclear scan relies on the natural ability of salivary glands to take up and secrete certain substances. After injecting a small amount of the radiotracer (99mTc-pertechnetate), images are captured over time using a gamma camera. These images display how the tracer is taken up and secreted into the mouth.

Basic Procedure Steps:

1. Patient Preparation:
   • No fasting typically required.
   • Remove any metallic jewelry or objects around the face and neck.
2. Radiotracer Injection:
   • A small dose of 99mTc-pertechnetate is injected intravenously.
3. Initial Imaging (Uptake Phase):
   • Images are taken immediately to observe how quickly the salivary glands absorb the tracer.
4. Salivary Stimulation Phase:
   • A lemon juice or citrus tablet is given to stimulate saliva secretion.
5. Excretion Imaging:
   • After stimulation, further images are taken to assess the secretion of the tracer into the mouth.
6. Completion:
   • The test usually takes about 30 to 45 minutes.

What Does the Scan Show?

The salivary gland scan provides a functional map of gland activity, helping distinguish between normal, reduced, or absent salivary function. It helps to determine:

• How well each gland takes up the tracer
• How efficiently each gland secretes saliva after stimulation
• Whether an obstruction is present in the ductal system
• Which gland is affected in cases of asymmetry or swelling
• Baseline functional capacity before radiation therapy

Clinical Value of Salivary Gland Scan

This imaging modality is especially helpful when anatomical imaging such as CT or MRI does not provide clear answers or when function needs to be evaluated. It is also a safer and quicker alternative to traditional conventional sialography, which requires cannulation of the duct.

Benefits of Salivary Gland Scan:

• Non-invasive and safe, with minimal discomfort
• Detects early functional changes even before anatomical abnormalities appear
• Provides real-time dynamic information
• Helps distinguish between inflammatory, obstructive, or neoplastic conditions
• Monitors changes in glandular function over time or post-treatment
• Plays a critical role in therapy planning (e.g., before 177Lu-PSMA for prostate cancer)
• Avoids exposure to iodinated contrast agents used in traditional imaging

Who Might Need This Scan?

A Salivary Gland Scan is commonly advised for:

• Patients with dry mouth symptoms (xerostomia)
• Recurrent swelling of parotid or submandibular glands
• Suspected ductal blockages without stones
• Children or adults with suspected congenital gland defects
• Pre-radiation therapy evaluation
• Post-surgical assessment for gland preservation or dysfunction

Limitations of the Scan

While the salivary gland scan offers excellent functional data, it may have limited value in identifying small tumors or anatomical details. For such cases, it is often used alongside ultrasound, MRI, or CT.

• Low spatial resolution compared to structural imaging
• May not pinpoint tumors or abscesses
• Not suitable for detailed ductal anatomy
• False negatives possible if both glands are equally affected

Preparation and Safety

No special preparation is usually required for this scan. It is a very safe procedure with a low dose of radiation.

• Patients can eat and drink normally before the scan
• Inform the physician if you are pregnant or breastfeeding
• Usually takes less than one hour in total
• No recovery time needed; patients can return to daily activities immediately

Conclusion

The Salivary Gland Scan or Radionuclide Sialography is a highly effective nuclear medicine imaging test used to evaluate the functionality of the salivary glands, particularly the parotid and submandibular glands. It is especially beneficial in identifying functional disorders, blockages, or glandular dysfunction in patients where structural imaging is inconclusive. This scan provides dynamic, real-time insight into how well the glands absorb and secrete saliva. Its non-invasive nature, combined with the ability to guide treatment decisions in complex cases—such as prior to Lu-177 PSMA therapy or in chronic conditions like Sjogren’s syndrome—makes it a critical tool in the diagnostic workflow of salivary gland evaluation.

Whether for obstructive symptoms, post-operative assessment, or monitoring gland function, the salivary gland scan remains a valuable and reliable diagnostic option.