Preparation required before thyroid scintigraphy
What patient preparation is required before thyroid scintigraphy?
Patients should fast after midnight or, at a minimum, for 4 hours before receiving the radioactive iodine-123 ( 123 I) pill to maximize absorption through the gut. Patients should also avoid ingesting foods containing high amounts of iodine because they would saturate the iodine stores in the body and thyroid gland and diminish the uptake of the radioactive iodine. Foods such as shellfish and seaweed and supplements containing large amounts of iodine should be avoided. Patients should also discontinue taking any medication that would affect thyroid function, particularly thyroid replacement medication (for at least 2 weeks); thyroid blocking medication (propylthiouracil or methimazole for at least 5 days); and other medications, such as amiodarone, that contain substantial amounts of iodine. Finally, patients should not undergo scanning if they have received iodinated contrast agents as recently as 1 month before the scan (although sometimes the effects of such contrast agents on the thyroid can be seen up to 3 months later).