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Patient Preparation
Patients must be off iodine-containing drugs, including radiographic
contrast! (X-Ray dye) The minimum time interval between prior
iodine administration and scanning varies from one week (e.g. iodine
solution) to 4 weeks (Synthroid) to 2-10 years (oil-based Myelogram).
If the patient has had an IVP or a CT with IV contrast, a thyroid
scan should not be attempted for 4-6 weeks. Many other medications
interfere with scanning (PCN, antihistamines, Amiodarone, etc.). Make
sure that all medications that the patient is taking are listed on
the requisition.
Patient must not have any food or drink for 4 hours prior to
their exam.
Exam Procedure
The uptake and scan procedures involve three visits to the Nuclear
Medicine Department. On the first day the patient will be asked
to swallow a small amount of radioactive iodine. The drink is tasteless
and has no side effects. This visit should take approximately fifteen
minutes. Two hours later, the patient must return for a measurement
of their thyroids radioiodine uptake.
On the following day, the patient will return for another measurement
of the radioiodine uptake, as well as an injection of a second
radioactive tracer. This second tracer allows a picture to be taken
of the thyroid gland.
The uptake procedure measures the percent absorption of radioactive
iodine by the thyroid gland. For the uptake measurement, the patient
sits comfortably in a chair, and a detector will be positioned
several inches from the neck. The amount of the radioiodine in
the thyroid gland will be measured. This will take approximately
five minutes.
For the scan, the patient will lie on their back on an imaging
table with the camera positioned above them. The image takes up
to five minutes. After imaging, a nuclear medicine physician may
examine the gland. We may then take additional images to look at
a certain part of the gland in detail. The procedures on the second
day will take 60 - 90 minutes.
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