Preliminary Diagnosis: Thyroid Nodule
I. What imaging technique is first-line for this diagnosis?
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Ultrasound of the thyroid gland.
II. Describe the advantages and disadvantages of this technique for diagnosing a thyroid nodule.
Advantages
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Does not expose patients to ionizing radiation.
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Highly portable and relatively inexpensive imaging modality.
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Helps detail the vascularity and complexity of any suspected thyroid nodular abnormalities.
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May guide percutaneous biopsy and fine needle aspiration.
Disadvantages
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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?
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CT of the thyroid bed with IV contrast.
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MR of the thyroid bed with IV contrast.
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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
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Offers better evaluation of the surrounding soft tissues and osseous structures than ultrasound.
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Evaluates for extension of local thyroid disease/neoplasm and distant metastasis.
Disadvantages
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Less sensitive and specific in characterizing the complexity and vascularity of thyroid nodular lesions than ultrasound.
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Less portable and relatively more expensive compared to sonographic imaging.
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Exposes patients to ionizing radiation.
MR of the thyroid bed with IV contrast
Advantages
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Does not expose patients to ionizing radiation.
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Offers exquisite evaluation of the surrounding soft tissues.
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Highly adept in detailing any evidence of distant cervical lymphadenopathy and metastasis.
Disadvantages
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Expensive.
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Time consuming.
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Less adept in detailing subtle thyroid mineralization which is characteristic in certain thyroid abnormalities, i.e., medullary carcinoma.
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Less adept in guiding percutaneous biopsy and therapy.
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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
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Moderate in sensitivity and moderate in detailing hot or cold thyroid nodules.
Disadvantages
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Limited in detailing the surrounding soft tissues, vasculature, and osseous structures.
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Exposes patients to ionizing radiation.
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Limited in sensitivity and specificity in detecting and detailing small thyroid nodules.
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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
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May be contraindicated in pregnant patients.
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IV contrast may be contraindicated in patients with renal failure or contrast allergy.
MR of the thyroid bed with IV contrast
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Contraindicated in patients with non-MR compatible hardware.
Nuclear medicine thyroid scintigraphy utilizing Technetium 99 m pertechtenate and I-123
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May be contraindicated in pregnant and breast feeding patients.
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