Thyroid scan (Tc-99m)

Dr Ian Bickle and Radswiki et al.

Tc-99m [pertechnetate] thyroid scan is one of the functional nuclear medicine studies that can be used to assess the thyroid gland.

  • patient preparation
    • NPO for 4 hours prior to exam
  • radiopharmaceutical
  • dose and route of administration
    • 3-5 mCi IV
  • time of imaging
    • 20 minutes after Tc-99m pertechnetate administration
  • equipment
    • camera: gamma camera
    • collimator: pinhole
    • window: 20% energy window centered at 140 KeV
  • procedure
    • obtain anterior, LAO, and RAO views
    • mark chin, suprasternal notch, palpable nodules, and surgical scars

 

Interpretation:

Radiotracer uptake on the thyroid scan needs to be interpreted with biochemical thyroid function tests and thyroid antibodies (eg antithyroglobulin, antimicrosomal, thyrotropin receptor). The combination of these results can usually distinguish between the causes of thyroid dysfunction.

Increased uptake:

  • Graves Disease
  • Hashitoxicosis
  • Subacute thyroiditis (thyrotoxic phase)

Normal uptake:

  • Hashimoto disease
  • After I131 therapy
  • Subacute thyroiditis (recovery phase).

Decreased  uptake: 

  • Extraneous iodine uptake (eg amiodarone, high iodine diet, recent CT iodinated contrast).
  • Subacute thyroiditis.
  • Struma ovarii.
  • Hashimoto disease

 

 

 

 

 

See also

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Article information

rID: 15560
Section: Physics
Synonyms or Alternate Spellings:
  • Tc-99m thyroid scan
  • Tc-99m pertechnetate thyroid scan

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