Originally Posted by LIND
I go for my thyroid scan tomm and have a few questions. Any side effects from the radoactive iodine that they will inject into my bloodstream? How long do the results take? They told me that the scan takes (2) days. Tomm they inject me and then I go back 5 hours later. Then I go back the day after. Why is it a 2 day test? Thanks
First of all, know that it is a painless test. A thyroid scan is an excellent tool to find out what's going on in your body. It is used to characterize the active and inactive thyroid tissue (including nodules) and can indicate how well the thyroid gland is functioning.
A low-dose radioactive substance is used as a "marker" (similar to the technology used for barium swallows in upper gastrointestinal studies), so that the body parts that absorb the substance are more easily viewed and evaluated. The test takes up to a full day from start to finish, so you may have to plan not going to work. They typically use I-123 for a scan, which has a lower frequency and is easier dissipated form of radiation than I-131 (used for ablation treatment). The technician told me it's comparable to the radiation absorbed being on the beach for two days.
You will be told to come with an empty stomach, and will not be allowed to eat or drink for the four hours before the scan is complete. If you previously had thyroid surgery, they may want to read your pathology results. Best bring along a copy of it, if possible, just in case.
A few days to a week before your scan, your doctor may have you avoid iodine-containing foods so that your body absorbs as much of the marker solution as is possible. This is not always requested, however. Ask if there are any supplements you should stop taking. In addition to iodine, they typically request that you stop anything containing iron.
When you arrive, they will ask you to drink a small quantity of radioactive iodine solution (tastes like mild sea water) or they may give you a pill. Sometimes the scan is done with technitium instead of iodine, but I believe the taste is not much different. This is taken on an empty stomach, so the process is typically started early in the morning.
The amount of radiation is relatively small (like a chest xray) and dissipates quickly. However, it is a dosage suitable for adults. You should not have this test if you are pregnant or nursing, as the radioactive iodine could affect your baby's thyroid gland. If you have small children or clinging pets, ask your doctor or the technician if there are any restrictions about hugging or being close to them for the next few days after the scan.
Bring a book, because you have to wait a several hours before the scan (so that the iodine is absorbed by the active thyroid tissue). They typically let you leave and come back.
The test itself is quite simple and somewhat like an MRI or CT-scan. You lie flat on a table with a pillow under your neck to prop it up. Ask for a leg support pillow if your back is uncomfortable. The camera (on a platform) moves down until it's about an inch from your face, but you can see from the sides and the camera will not touch you. The table slowly moves through a donut or half-dome and the scanned image appears on the technician's screen.
If you have a Total Body Scan, they first scan you from head to toe (your head is out from under the camera in about 6-7 minutes, but the scan takes 20-30 minutes). This scan is conducted about four hours after you took the tracer. After the Total Body Scan, they have you drink some water (swishing it around to rinse your mouth), they ask you to empty your bladder, and then they run a Thyroid Scan with the camera in a stationery position over your neck for ten minutes. Once they have confirmed that the images are clear, you can go.
If it's a two-day scan, they will ask you to come back 20-24 hours after you took the tracer to repeat the scans. This time, they have you empty your bladder first, then the total body scan, then drink water, urinate again, and then the neck scan. Total scanning time is the same, and the appointment lasts 1-2 hours, depending upon your wait. And that's it.
Because the Iodine will only be absorbed by thyroid tissue, you'll primarily see the excretory body parts (e.g., bladder & kidneys, plus neck area) light up on-screen for the Total Body Scan. The neck scan will highlight any hormone-producing thyroid tissue.
Results are usually reported anywhere between 2 days to 2 weeks (depending on the lab or hospital and how fast they can have a doctor interpret it). Most technicians are not allowed to comment to you directly, as they are not doctors. But they may be willing to explain what is shown on the screen and, if they bring a doctor in the room, he or she may be willing to tell you a quick impression (pending further study later). If they're willing to show you the scans, ask to see the color image, so you can see what actually lit up in your body.
There are two types of tests: a one-day test (Thyroid Uptake Scan) and a two-day test (Total Body Scan). The one-day test takes up to a full day because you have to wait four hours for your body to absorb the iodine. Because this test is typically for a neck scan only, it's less complicated and may take less of your time. But the waiting time before being brought in to take the tracer and again before the scan can make it a long day.
The two-day test is as described above (two scans each day), with a second, repeat of the two scans on Day Two to see how much of the marker iodine is still in your tissue after 24 hours. You do not take an additional dose on this second day, so the test only takes as long as your waiting time and the actual scans.
The theory behind an uptake scan is as follows: Normal thyroid tissue absorbs iodine (to help it produce thyroid hormone), so the radioactive iodine acts as a marker and will "light up" any normal, hormone-producing tissue in the scan's imaging. The test will also allow the technician and interpreting physician to measure the size of the thyroid gland and any nodules, and to determine your thyroid function through an estimate of its iodine absorption.
If you have solid nodules that do not produce hormone, they will appear as a different color (usually dark) on the scan and are known as "cold" nodules. Nodules that produce hormone are known as "warm" or "hot" tissue, depending upon how much iodine they absorb (e.g., hormone they produce). I am not sure what fluid-filled cysts look like on scan, but I would assume they appear similar to cold nodules. Their shape and density on the scan may suggest that they are cysts instead of nodules, but this can be confirmed by Ultrasound.
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