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A nuclear thyroid scan is a simple, painless diagnostic procedure to check for various thyroid problems. A doctor may suggest getting a scan if a patient has a noticeable lump in the neck, chronic pain, or symptoms of an over- or under-active thyroid gland. The procedure involves taking a very small dose of radioactive iodine, specifically the isotope iodine-123, and allowing the material time to reach the thyroid. Gamma ray pictures are then taken to trace the dispersion of iodine in the thyroid, which can reveal important clues to what type of thyroid problem a patient may have. In most cases, a nuclear thyroid scan can be performed in an outpatient diagnostic center in less than one hour.
A person who is scheduled for a nuclear thyroid scan may be given special instructions about how to prepare. Certain medications may interfere with the iodine, so it is important to ask the doctor whether or not medication use should be stopped or adjusted in the days leading up to the exam. Most clinics recommend that patients avoid eating or drinking one to two hours before the exam. Metal jewelry may interfere with the gamma ray machine, so people should take off earrings and necklaces before entering the facility.
Iodine radiation can be administered in a few different ways, but it is usually given in a tasteless oral capsule. A patient generally needs to take a capsule about six hours before the nuclear thyroid scan to give it ample time to be absorbed. When it is time for the actual scan, a doctor, nurse, or nuclear medicine technician will lead the patient into an exam room and prepare a comfortable bed or chair. The scan can take up to one hour, and patients are required to remain very still and avoid speaking until the procedure is completed.
During the nuclear thyroid scan, a gamma ray machine generates several pictures of the thyroid. The machine detects radiation emitted from the absorbed iodine to create a basic outline of the gland and highlight spots where concentrations are especially high. Some gamma ray machines allow the images to be viewed instantly on a computer monitor in the exam room. Once the test is complete, a patient is allowed to leave the diagnostic center with no special restrictions or instructions. Test results are generally available within a couple days of the procedure.
Doctors can gain valuable information from nuclear thyroid scan results. The test may reveal that the thyroid is unusually large or swollen, or that a protruding nodule is present. Based on the concentrations of iodine in specific areas, the doctor can pinpoint suspicious masses that may be cancerous. If more or less iodine is absorbed than expected, the patient may be suffering from hypo- or hyperthyroidism. The physician usually meets with the patient to explain test results. Based on the outcome, arrangements can be made for additional diagnostic tests or treatment plans.