Nuclear Medicine Technology

Until this section is complete, please refer to your methodology text:
Wilson MA (ed). Textbook of Nuclear Medicine. pages 86, 167 & 533

Also see Early PJ & Sodee DB (eds). Principles and Practice of Nuclear Medicine (2^nd ed). pages 100 to 101 and 805 to 809 (especially good).

Thank you for your patience and understanding.

Lyle

Review of Pathology

The salivary glands are fleshly exocrine glands that surround the oral cavity and secrete saliva to aid the digestion process. There are three major pairs and numerous minor salivary glands. The major pairs are the:

• parotid glands
  • located anterior and inferior to the ears in the subcutaneous regions of the cheek
  • serous secretions enter mouth via parotid (Stensen's) duct opposite second upper molar
• submandibular / submaxillary glands
  • located on floor of mouth close to angle of jaw
  • mixed serous and mucous secretions enter mouth via submandibular (Wharton's) duct lateral to point where frenulum attaches to tongue
• sublingual glands
  • located under mucous membranes of floor of mouth just lateral to tongue
  • mainly mucous secretions enter mouth via several sublingual ducts opening either near tongue or into Wharton's duct.

The acinus is the secretory unit of salivary glands. Each acinus is composed of secretory cells which produce saliva. interspersed with myoepithelial cells.

Several disorders can affect the salivary glands:

• Sjögren's Syndrome: autoimmune disorder characterized by presence of at least two of the three features of classic triad of:
  • xerostomia
  • keratoconjunctivitis sicca
  • connective tissue disorder
    • usually rheumatoid arthritis
    • may also be systemic lupus erythematosis (SLE) or
    • other collagen vascular disease
• salivary gland tumors
  • benign tumors
    • benign mixed tumors (pleomorphic adenoma)
    • Warthin's tumor
      • benign tumor of obscure histogenesis
      • unique characteristic is retention of function and failure to washout following stimulant
      • classically located in posterior, inferior portion of parotid gland.
    • oncocytoma (oxyphilic adenoma)
  • malignant tumors
    • adenocarcinomas
    • squamous cell carcinomas
    • undifferentiated and mixed carcinomas
• inflammatory lesions
  • acute sialadenitis
  • chronic sialadenitis
• obstruction
• abscess / cyst

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Principle

The ability of the salivary glands' intercalated duct epithelial cells to transport large monovalent anions, including iodide and pertechnetate, from the surrounding capillaries and secrete them into the saliva provides the principle for imaging the salivary glands with Tc-99m pertechnetate. The functional capabilities, structural integrity and location of the glands can be assessed.

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Indications

Indications for salivary gland imaging include:

• evaluation of functional status of salivary glands
  • presentation of xerostomia
  • presentation of pain
• detection and evaluation of duct patency
  • pain upon salivation
  • presentation of xerostomia
• detection and evaluation of mass lesions
• preoperative localization of tumors

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Procedure

Patient Preparation

No specific patient preparation:

• rinsing mouth prior to study may reduce excretion of pertechnetate into mouth
• no thyroid-blocking agents within 48 hours of study.

Pharmacologic Interventions

No specific pharmacologic interventions.

Radiopharmaceutical

Tc-99m pertechnetate

• ~300 MBq (150 to 450 MBq)

Equipment

Gamma camera:

• LEAP or LEHR collimator
• 140 keV with 15% to 20% window

Computer system:

• 128 x 128 matrix
• dynamic images at 1 to 3 seconds per frame for 30 to 60 seconds
• static images
  • first image for 400k to 500k counts
  • remaining images for time

Data/Image Acquisition Parameters

Anterior Flow

Position patient in "Water's" position:

• nose and chin touching collimator
• include thyroid gland in images for reference/comparison.

Inject Tc-99m pertechnetate into vein in antecubital fossa.

Dynamic images at 1 to 3 seconds per frame for 30 to 60 seconds.

Static Images

Position patient in "Water's" position:

• include thyroid gland for reference/comparison.

Obtain first image immediately following flow:

• collect 400k to 500k counts.

Repeat anterior images every 3 to 5 minutes for total of 15 to 20 minutes:

• images acquired for same time required to collect first image.

After last anterior image at 15 to 20 minutes, obtain left and right laterals or anterior obliques:

• include thyroid
• acquire for same time as first image.

Washout

Administer salivary gland stimulant (sialogogue) following completion of static images:

• lemon juice
  • swish in mouth for 5 to 10 seconds and expectorate
• lemon slice
  • swish in mouth for 5 to 10 seconds and expectorate.

Obtain "washout" images ~5 to 10 minutes after stimulant.

Position patient in "Water's" position:

• include thyroid gland for reference/comparison.

Obtain anterior and left and right lateral/oblique images for same time required to obtain first static image.

Repeat washout images as required.

Data/Image Processing and Display

No additional data/imaging processing generally required.

Ensure all images labelled appropriately.

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Interpretation of Results

Normal Study

Anterior flow demonstrates vascularity.

Observe:

• carotids up to Circle of Willis
• anterior and middle cerebral arteries
• may be mid-facial (nasopharangeal) blush
• parotid glands may show slight bilateral blush
• submandibular glands not usually seen
  • sublinguals never seen
• venous return demonstrates:
  • internal jugulars
  • diffuse blood pool of face
• later images may demonstrate early activity concentration in parotid glands and thyroid.

Static images demonstrate salivary gland function.

Observe:

• by 1 minute have distinct, symmetrical concentration of activity in parotid and submandibular glands and in thyroid
• over 5 to 10 minutes observe increasing levels of activity in parotid and submandibular glands
• by 15 minutes may be perceptable decrease in activity in glands due to spontaneous excretion into mouth

Washout demonstrates salivary gland excretion.

Observe:

• stimulant causes prompt clearance of activity from glands into mouth
• essentially complete within 5 to 10 minutes.

Pathologies

Sjögren's Syndrome

Generalized gland dysfunction:

• as involvement becomes more severe, generalized gland dysfunction increases.

Parotids are generally affected before submandibulars.

Decreased function qualitively compared to thyroid as reference:

• assumes normal thyroid function.

Warthin's Tumor

Flow and blood pools may demonstrate variable hyperemia.

Often, but not always, concentrate activity to greater level than surrounding normal tissue.

secretory elements do not communicate with a patent duct system:

• secretions localize within cystic spaces of tumor
• tumor remains "hot" after washout phase.

Inflammatory Lesions

Obstruction

Benign Mixed Tumors

Malignant Lesions

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Common Technical Difficulties and Artifacts

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Other Modalities for Determining the Same or Similar Information

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Case Studies

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Specific References

Pathology

Texts

Internet URL's

Salivary Gland and Thyroid by Karen H. Calhoun, M.D.

A focus on Diseases of the Salivary Glands by Meirion Thomas

Salivary Glands: What's Normal, What's Abnormal by Dr. Peter Casano

Procedure

Texts

Journals

Internet URL's

Videos

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Quiz

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