Nuclear Medicine Thyroid Scan

Authors: Ms Merrin Angwin*
                            Dr Dee Nandurkar *

What are the prerequisites for having a thyroid scan done?

  • Thyroid serum measurements of TSH, T4, T3, thyroglobulin, TSI, TPOAb as required
  • Ultrasound study of thyroid gland if nodules are suspected
  • Patient should not have any radiological procedure that requires the infusion of iodine contrast medium at least 8 weeks prior to scanning (CT most common)
  • Certain foods, vitamin supplements and medicines containing Iodine should be stopped prior to scan
  • Patient should also cease thyroid hormone replacement medication
  • Drugs to be ceased prior to the scan are as follows:
    • Oroxine
    • Tertroxin – needs to be ceased for 5 days
    • Neo-mercazole (carbimazole)
    • Propylthiouracil
    • Amiodarone – antiarrhythmic contains high dose iodine and needs to be replaced for 3 months prior to scan
    • Lithium – affects uptake, discuss with patient

What are the absolute contraindications for a thyroid scan?

This study may not be suitable for pregnant women. The benefit versus risk should be discussed with the nuclear medicine specialist.

Women who are breastfeeding and people who are the primary or sole carer for small children may need to make special preparations after the test to stop breastfeeding for a short time and to avoid close contact with young children due to the small amount of radioactivity released for a while after the test. Patients should discuss this with their referring doctor or the nuclear medicine practice where they will have the test for details. See nuclear medicine for further information about the precautions to take with nuclear medicine studies for breastfeeding patients and those in close contact with children.

What are the relative contraindications for a thyroid scan?

  • Patient has not discontinued thyroid medication.
  • Patient has received iodine based contrast media for CT scan within 8 weeks.

Please contact the nuclear medicine department for scanning bed weight limits.

What are the adverse effects of a thyroid scan?

There are no known associated risks, but the patient will be receiving a dose of ionising radiation (see radiation risk of medical imaging for adults and children). If the patient is pregnant or breast feeding, please contact the nuclear medicine department with regards to proceeding with the scan.

Are there alternative imaging tests, interventions or surgical procedures to a thyroid scan?

Ultrasound is routinely used in assessment of the thyroid gland, in particular for characterisation of thyroid nodules. Non contrast CT scan may also be used to assess retro-sternal extent or compressive effects of an enlarged thyroid gland.

Radiopharmaceuticals 123I and 131I capsules, given orally, may be used instead of Sodium Pertechnetate 99mTc however the indications for their use are different to the routine indications for use of a Sodium Pertechnetate scan.

Contact your nuclear medicine physician to discuss relative merits.

*The author has no conflict of interest with this topic.

Page last modified on 26/7/2017.

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