Therapy - Nuclear Medicine

What precautions need to be taken when a family member or I go home after having radioiodine therapy that uses ¹³¹I?

You will be measurably radioactive after your treatment, even when you are allowed to go home. However, the radiation dose rate from you will be very low, so exposure of others will be very low. Further, the dose rate falls off rapidly with distance; those farther from you receive less radiation exposure. The dose rate also falls off rapidly with time because ¹³¹I doesn't remain in the body very long. The total radiation dose to anyone else, even with close, continuous contact, will not cause harmful effects. There is no need for concern about effects on your family, pets, etc., but it is still prudent to avoid close, prolonged contact for the first week.

The advice to patients who are going home depends on whether they were treated for hyperthyroidism or thyroid cancer and on how much radioactive iodine was administered. These variables determine how much the patient needs to avoid close contact and for how long. Concerns are heightened if very young children will be present because (1) taking care of a toddler requires longer and closer proximity than for older children, (2) one tends to kiss toddlers and saliva contains radioactive iodine, and (3) toddlers get their hands on everything and their hands go right to their mouths, so internal contamination can be an issue.

General guidelines given to patients who are going home may include the following items:

• Arrange to have sole use of a bathroom for two days following treatment.
• Avoid public transportation for the first day following treatment.
• Limit personal automobile travel with others to only a few hours per day for the first two days following treatment. Keep as much distance as possible between you and other passengers.
• Sleep in a separate room for the first two nights following treatment.
• Arrange for any pregnant individuals or children younger than two years old currently living at your residence to stay at a separate residence for three days following treatment.
• Avoid close contact with others by maintaining a distance of 1 meter (approximately 3 feet) for up to three days following treatment.
• Avoid going shopping, to the movies, to restaurants, etc., for the first two days following treatment.

A patient just discharged from a nuclear medicine ward five days after ¹³¹I treatment for thyroid cancer (about 5,550 MBq) has been admitted to my hospital for another, unrelated medical problem. What is your advice for other patients' and nurses' protection?

The administration of radioactive iodine to a patient is a very common procedure in the treatment of thyroid cancer. Following the surgical removal of the thyroid, the patient is evaluated for any remaining thyroid tissue. Surgery generally does not remove all the thyroid tissue, so radioactive iodine (¹³¹I) is usually given to destroy any remnant tissue. Because the vast majority of the thyroid was removed, the patient will excrete most of the radioactive iodine in the first day or two after it is administered.

In the United States, patients are released from confinement without restriction on interacting with the public when it is determined that doses received by individuals are at a safe level. There are a number of assumptions about the patient's interactions with the public, but the belief is that the patient really does not present a significant radiation source. In your situation, the patient does not represent a significant risk to your patients or staff. Otherwise, the patient would not have been released from the other hospital.

I was visiting a friend who was in the hospital after getting ¹³¹I therapy for thyroid cancer. It wasn't until I was leaving that I noticed the sign on the door saying there should be no visitors. I was there about 30 minutes. I asked one of the nurses about it and was told there wasn't an issue because I wasn't there long. Is that true?

Usually, the radiation level at bedside is such that a short time spent there would only expose you to a small amount of radiation, an amount similar to or less than what you might receive from a chest x ray or a month's worth of natural background radiation. If you weren't at the bedside but were farther away, your radiation exposure would be even less.

If you have further questions, the radiation safety officer (RSO) of the hospital might better be able to help you. This would be the person most likely responsible for the radiation protection of anyone who might enter the room. The RSO would be in the best position to tell you what radiation exposure (if any) you might have received.

Is there an amount of time after a radioiodine therapy treatment that I shouldn't go to the dentist?

The use of universal precautions, that is, use of gloves and other precautions normally used to protect against contamination from patient body fluids, should provide adequate protection for dental personnel, even when emergency dental care is required prior to six days post treatment.

Can radiation be used in a pill? Can people take it that way?

Radiation can come in the form of a pill. Iodine (¹³¹I) used in thyroid treatment might be given in pill form or as a liquid. The choice is an institutional decision based on many factors, including the amount to be given to a patient. Most other radiopharmaceuticals are either injected or inhaled.

My husband was given a therapeutic dose of ¹³¹I. The dose was large enough that it required isolation in the hospital overnight. Even though my thyroid was removed four years ago, the technician who administered my husband's therapy informed me that I could still receive exposure from my husband's therapy. As I have no thyroid tissue, how can that be?

The exposure is associated with the gamma rays and x rays emitted by ¹³¹I. A person who received therapeutic ¹³¹I still contains some radioactivity when released from the hospital, so is a "source" of exposure for anyone nearby. The amount of exposure is pretty small or the patient would not be able to leave the hospital.

Do you have any information about the radioisotope ¹³¹I, its involvement in cancer treatment, how it works, its history, and its economic importance?

Radioactive iodine, primarily ¹³¹I, has been in use in nuclear medicine for both diagnosis and therapy procedures for half a century. Its use for diagnostic procedures has diminished considerably since about 1970 when other radionuclides, primarily ^99mTc, replaced it. However, ¹³¹I continues to play a significant role in the treatment of thyroid disorders and diseases such as hyperthyroidism and thyroid cancer. The National Council on Radiation Protection and Measurements (1996) estimates that 180,000 patients per year receive ¹³¹I treatments for hyperthyroidism and 20,000 patients per year receive ¹³¹I treatments for thyroid cancer. Both treatments are highly successful, with cure rates in excess of 90 percent. The estimation of the economic importance is hard to determine. How does one put a dollar figure on a painless medical procedure that is highly effective? How do we figure a price for longevity? We have no estimated numbers to go with these questions.

Reference: National Council on Radiation Protection and Measurements. Sources and magnitude of occupational and public exposures from nuclear medicine procedures. Bethesda, Maryland: National Council on Radiation Protection and Measurements; NCRP Report No. 124; 1996.

How safe is radioactive iodine? What are the side effects?

To our knowledge, there have been no side effects from the diagnostic uses of injected radioactive iodine compounds. The effect of radioiodine therapy is the killing of thyroid tissue.

I had radiation therapy for thyroid disease over 10 years ago. I am concerned about developing cancer from this treatment. Are the risks of adverse health effects higher since I had this treatment?

[Note: This response presumes the treatment was radioactive iodine]. Radioactive iodine has been and still is used for treatment of hyperthyroidism. It is safe, effective, simple, and inexpensive. The radiation is confined to the thyroid gland and its immediate surroundings. Dose falls off rapidly with distance from the gland, even inches. There is a chance of inducing a cancer, but this is a rare event, rather like the fatal allergic reactions to medicines. The benefit to your health far outweighed this very small risk. As you know, untreated thyroid disease can lead to serious, even fatal, complications.

I am a 24-year-old male. I have a hyperthyroid problem for which I have been taking a prescription medication. Since it was still not cured, I went through radiation treatment with radioiodine. Please tell me the side effects of that radiation to my body and whether my ability to reproduce is affected.

Fortunately, the only effects of the radioiodine (¹³¹I) are on your thyroid gland. The gland should shrink, and if you were given enough of a dose, it should disappear completely. This means that you will have to take thyroid hormone replacement pills for the rest of your life. However, all other parts of your body should be fine. It will not affect sexual intercourse desire, performance, or fertility. Much larger doses of radioiodine, such as are used for certain cases of thyroid cancer, have on occasion been associated with a decrease in sperm count, which is probably transient, but that is not the case with the much lower doses of radioiodine used to treat hyperthyroidism.