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