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Radioactive Iodine Preparation and Precautions
Since radioactive iodine (RAI) targets thyroid cells only, it is a safe and effective way to treat Graves disease and thyroid cancer and to test thyroid function and monitor recurrence of thyroid cancer. However, it requires strict compliance with instructions in order to insure its accuracy and efficacy. In order to have the best test/treatment possible, there are preparatory measures you must take in order to maximize the uptake of the radioactive iodine by remaining normal thyroid tissue or metastatic thyroid cancer. In addition, since the radioactive substance can effect others around you with normal thyroid tissue, you will be instructed to take certain precautions to protect those around you. Below are important general instructions and information on what to expect. Your doctor will discuss your individual needs at the time of your consultation.
<!-- Before RAI Scanning or Treatment -->
When you receive a scan, an RAI pill is given in order to see if any thyroid tissue remains in your body. If you are receiving treatment, more RAI is given after the scan in order to destroy any remaining thyroid cells that may be cancerous. Depending on the amount needed to destroy the cells, you may need to be hospitalized for your treatment. All patients receiving 30mci or more of RAI must be admitted to the hospital.
Before receiving RAI, tell your doctor if you are pregnant or breast feeding. If your doctor orders a pregnancy test before your treatment or scan, do not have sexual intercourse until after the treatment/scan. Tell your doctor if you have received any x-rays using iodine contrast within the last 6 weeks.
STEP 1: 6 weeks before scan/treatment: Discontinue Synthroid and begin Cytomel
6 weeks prior to the RAI scan or treatment, you will be instructed to stop taking your thyroid hormone medication . In this way, your body is made to be hypothyroid with a deficiency of thyroid hormone. Once hypothyroid, the brain produces more of its thyroid stimulating hormone in an attempt to increase thyroid hormone levels in the bloodstream. This increase in thyroid stimulating hormone causes the most efficient concentrating of iodine by thyroid tissue because it needs the iodine to make more thyroid hormone.
In an effort to decrease the amount of time that you must be hypothyroid, a short-acting form of thyroid hormone called T3 (the most common brand name is called Cytomel) is given after you stop taking your regular, long-acting form of the medication (T4). The T4 or levothryoxine is stopped 6 weeks prior to the scan so that it may be eliminated from the bloodstream. At that time, T3 is started and is continued until 2 weeks prior to the scan.
<!-- Step 2 -->
STEP 2: 2 weeks before scan/treatment: Discontinue Cytomel.
It takes two weeks for the short-acting form of thyroid hormone to be eliminated from your bloodstream. Thus, you will be most hypothyroid for two weeks prior to your scan/treatment. During these two weeks, you should not take any thyroid hormone until after the treatment.
Unfortunately, becoming hypothyroid produces unpleasant symptoms: fatigue, difficulty concentrating, weight gain, and sometimes depression. The elderly are often most bothered by these symptoms which can be quite disabling.
STEP 3: 1 week before scan/treatment: Begin low iodine diet, and continue until treatment is completed.
Preparing for the total body scan also requires that you avoid iodine in your diet at least one week prior to the test. If you consume a high iodine diet prior to this test, the radioactive iodine is not taken up as efficiently by the thyroid because it has already absorbed the iodine it needs from what was present in your food. The two most common sources of high iodine include vitamins, which contain iodine, and seafood. Always check medication labels thoroughly to avoid taking iodine that may be included in standard multivitamin preparations. Since salt has been fortified with iodine in the United States, salty foods should also be eliminated. Always check the label to see if a particular food contains large amounts of salt or iodine.
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STEP 4: 2 days before scan/treatment: Blood tests.
Two days before an RAI scan or treatment, blood tests are taken to ensure that you are hypothyroid (so that the scan/treatment is as effective as possible). A pregnancy test may also be ordered if there is a possibility that you might be pregnant. A light breakfast, low-iodine is allowed before the tests. If you are having a total body scan or outpatient RAI treatment, the RAI pill is taken after the blood tests. You will be allowed to eat one hour after you take the pills.
<!-- The Day of the Scan/Treatment -->
On the day of your scan, around the same time you had the pills, you will have additional blood tests and the total body scan. The procedure will take about 4 to 6 hours. The scan is usually read by the radiologist that evening. You should call your surgeon's office the following morning for results and directions for resuming your thyroid medication.
Outpatient RAI Treatment
Outpatient treatment is similar to the scanning procedure, except that the RAI dose is greater. Before taking the pills, you will be able to discuss the treatment with a physician and will be asked to sign a permission form. You may eat 1 hour after taking the pills. Precautions, including the low iodine diet, start after you receive the pills.
Three days after you have taken the pills, additional blood tests are performed as well as a total body RAI scan. You may have a full breakfast.
Six days after the treatment dose, final blood tests are performed as well as a second total body scan.
Inpatient RAI Treatment
If you are treated with large doses of radioiodine to destroy thyroid cancer metastases, you will need to be hospitalized and placed in isolation for about 3 days after taking this medication in order to minimize the risk of radiation exposure to others. Since the RAI is passed out of the body through all bodily fluids such as stool, urine, saliva and sweat are potential forms of contamination. You must be hospitalized in a special isolation room so that all of your bodily fluids may be disposed of properly. You will be served your meals on paper plates with disposable utensils. Your urine and stool will be collected and disposed of in proper radioactive waste containers. Your bed sheets will be specially laundered. Personal items such as pillows, stuffed animals, or needlepoint should not be brought into the isolation room since these items will become contaminated with radioactivity. Newspapers, magazines and paperback books are allowed because these can be thrown away. In addition, all nurses, doctors and housekeeping personnel who enter your hospital room must wear a special badge to monitor the amount of radiation that they are exposed to. Only brief visits are permitted.
On the third day you will be scanned for residual disease and then discharged, after the hospital's radiation safety officers have determined that the level of radiation is low enough for discharge (using a portable machine which measures radioactivity). You will still have to closely follow the precautions outlined below for approximately one month.
<!-- Precautions After RAI Scanning or Treatment -->
In addition to all the special preparations prior to an RAI scan or treatment, there are also precautions to follow afterwards. Although only a small amount of radioactivity is involved with this scan, it is still important to follow these simple precautions in order to minimize radiation exposure to your family members and friends. Since the radioactivity is excreted through all bodily fluids, mainly urine, as well as feces, sweat and saliva, it is essential to isolate these fluids. After you've had your I131 scan/treatment, you should:
These precautions should be followed for three days after the I131 test. After this period of time, the radiation exposure to other people is negligible and you do not need to follow any additional precautions.