Imaging

Graves' Disease

Preliminary Diagnosis: Graves' Disease

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

  • Thyroid scan (thyroid scintigraphy)

II. Describe the advantages and disadvantages of this technique for diagnosis of Graves' disease.

Advantages

  • Can help differentiate other causes of thyrotoxicosis, such as functional thyroid nodules

  • Can support the diagnosis of Graves' disease

  • After the thyroid scan is performed, further treatment with radioactive iodine may proceed

Disadvantages

  • Uses radioactive pharmaceuticals

  • Relatively lengthy procedure

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

  • Pregnancy

  • Breast-feeding women

  • Recent (8 weeks) intravenous administration of iodine-based contrast (relative)

  • Failure to discontinue thyroid medication

IV. What alternative imaging techniques are available?

  • Ultrasound

  • Contrast enhanced CT of the orbits.

  • Contrast enhanced MRI of the orbits.

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of Graves' disease.

Ultrasound

Advantages

  • Characteristic findings of Graves' disease can support the diagnosis. However, specificity is diminished.

  • Characterization of thyroid nodules is identified on a thyroid scan.

  • Ultrasound guided fine needle aspiration of suspicious thyroid nodules can be performed.

Disadvantages

  • Imaging findings are not specific for Graves' disease.

Contrast enhanced CT of the orbits

Advantages

  • Indicated in cases of suspected thyroid ophthalmopathy

Disadvantages

  • Uses ionizing radiation

  • Cost.

Contrast Enhanced MRI of the orbits

Advantages

  • Indicated in cases of suspected thyroid ophthalmopathy

Disadvantages

  • Cost

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

Ultrasound

  • None

Contrast enhanced CT of the orbits

  • Pregnancy (relative)

  • Anaphylactoid reaction to iodinated contrast; steroid preparation may be used in patients with mild or moderate allergic reactions.

Contrast enhanced MRI of the orbits

  • Non-MRI compatible implanted devices

  • Relative contraindications include claustrophobia, obesity (due to MRI weight limits), and metallic implants in region of interest that are not MRI compatible

  • Renal dysfunction; use of gadolinium contraindicated when glomerular filtration rate is less than 30

  • Allergy to gadolinium contrast agents

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