Imaging

Thyroid Nodule

Preliminary Diagnosis: Thyroid Nodule

I. What imaging technique is first-line for this diagnosis?

  • Ultrasound of the thyroid gland.

II. Describe the advantages and disadvantages of this technique for diagnosing a thyroid nodule.

Advantages

  • Does not expose patients to ionizing radiation.

  • Highly portable and relatively inexpensive imaging modality.

  • Helps detail the vascularity and complexity of any suspected thyroid nodular abnormalities.

  • May guide percutaneous biopsy and fine needle aspiration.

Disadvantages

  • Highly operator dependent.

III. What are the contraindications for the first-line imaging technique?

No specific contraindications to ultrasound exist.

IV. What alternative imaging techniques are available?

  • CT of the thyroid bed with IV contrast.

  • MR of the thyroid bed with IV contrast.

  • Nuclear medicine thyroid scintigraphy utilizing Technetium 99 m pertechtenate and I-123.

V. Describe the advantages and disadvantages of the alternative techniques for diagnosing a thyroid nodule.

CT of the thyroid bed with IV contrast

Advantages

  • Offers better evaluation of the surrounding soft tissues and osseous structures than ultrasound.

  • Evaluates for extension of local thyroid disease/neoplasm and distant metastasis.

Disadvantages

  • Less sensitive and specific in characterizing the complexity and vascularity of thyroid nodular lesions than ultrasound.

  • Less portable and relatively more expensive compared to sonographic imaging.

  • Exposes patients to ionizing radiation.

MR of the thyroid bed with IV contrast

Advantages

  • Does not expose patients to ionizing radiation.

  • Offers exquisite evaluation of the surrounding soft tissues.

  • Highly adept in detailing any evidence of distant cervical lymphadenopathy and metastasis.

Disadvantages

  • Expensive.

  • Time consuming.

  • Less adept in detailing subtle thyroid mineralization which is characteristic in certain thyroid abnormalities, i.e., medullary carcinoma.

  • Less adept in guiding percutaneous biopsy and therapy.

  • May be subject to motion and susceptibility weighted artifact, degrading image quality.

Nuclear medicine thyroid scintigraphy utilizing Technetium 99 m pertechtenate and I-123

Advantages

  • Moderate in sensitivity and moderate in detailing hot or cold thyroid nodules.

Disadvantages

  • Limited in detailing the surrounding soft tissues, vasculature, and osseous structures.

  • Exposes patients to ionizing radiation.

  • Limited in sensitivity and specificity in detecting and detailing small thyroid nodules.

  • Unable to adequately detail the vascularity of a thyroid lesion.

VI. What are the contraindications for the alternative imaging techniques?

CT of the thyroid bed with IV contrast

  • May be contraindicated in pregnant patients.

  • IV contrast may be contraindicated in patients with renal failure or contrast allergy.

MR of the thyroid bed with IV contrast

  • Contraindicated in patients with non-MR compatible hardware.

Nuclear medicine thyroid scintigraphy utilizing Technetium 99 m pertechtenate and I-123

  • May be contraindicated in pregnant and breast feeding patients.

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