Answer to Question #7272 Submitted to "Ask the Experts"

I recently had a nuclear stress test done using Myoview. I was told that for the resting part I received 12 millicuries of Myoview technetium-99m and for the stress part I received another 24.5 millicuries of Myoview technetium-99m.

I am concerned about my radiation exposure and how this radiation exposure might affect me in the future. I've read that radiation exposure does not show negative effects for about 20 years. I also read that Myoview radiation exposure for this test is about 500 mrem.

My questions are:

1. How much radiation did I receive and how dangerous is it?
2. Can I expect this to negatively affect me in 10 or 20 or 30 years?
3. Will some internal organs be more sensitive to this radiation than others?
4. An x ray takes just a second to do, so your exposure is for a short period. With this Myoview test, even after 24 hours there is still more than 5 percent left (with a half-life of six hours), so how does your body like the constant exposure to radiation for several days (although reducing rapidly)?
   
   

How much radiation did I receive and how dangerous is it?

As you know, your cardiac stress/rest test was performed using a radiopharmaceutical called technetium-99m Myoview. For this study, your exposure was approximately 960 millirem (or mrem—a unit for effective dose). This is not a dangerous exposure.

Even with all the information that we have accumulated from the use of radioactive materials in medicine for many years and the known radiation effects that were seen after the bombs were dropped in Hiroshima and Nagasaki during World War II, there have been no demonstrated health effects for radiation doses less than 5,000 mrem received in one year.¹

For warranted medical procedures with either x rays or radiopharmaceuticals, the benefit of the information obtained from the procedure significantly outweighs the risk from the radiation dose. If I had this study and even additional x rays, I would not be concerned about the radiation exposure from these exams. Your doctor now has valuable information on your medical status.

Can I expect this to negatively affect me in 10 or 20 or 30 years?

The effects that you have read about are for people who have received much higher doses than those from diagnostic exams.

Will some internal organs be more sensitive to this radiation than others?

Some organs are more sensitive to radiation than others but, as I said, there are no known health effects for this low exposure.

An x ray takes just a second to do, so your exposure is for a short period. With this Myoview test, even after 24 hours there is still more than 5 percent left (with a half-life of six hours), so how does your body like the constant exposure to radiation for several days (although reducing rapidly)?

You have done a lot of reading about radiopharmaceuticals! Besides the fact that the material is decaying rapidly, your body is also eliminating it in your urine, so it is leaving your body faster than just radioactive decay. Additionally, all humans have been exposed to radiation every day since conception from the naturally occurring radioactive material in the earth, in our food and water, and from cosmic radiation. 

Radiation causes the same kinds of effects to our cells that other natural processes in our body cause. Our cells have great repair mechanisms when the DNA is damaged. To the cells in your body, the radiation from this study is no different from the background radiation. 

To put this exposure in perspective, we all receive an "effective dose equivalent" of about 300 mrem each year from what is called "background" radiation. This background radiation includes radon, cosmic rays, radiation from natural radioactivity in the earth, etc. If one lives at higher elevations (e.g., Denver, Colorado), the annual background radiation level is estimated to be around 400 mrem. While there are some technical differences between the terms "effective dose" and "effective dose equivalent," they can be considered about the same for comparison purposes.

Thus, the effective dose, 960 mrem, from the stress/rest test example above would be equivalent to what one would receive from about 3.2 years worth of background radiation for the average member of the U.S. population or about 2.4 years of background radiation living in the Denver area.  

I hope that this answers your questions and that you will not be overly concerned about having radiological exams. They really have improved and saved many lives. If you trust your doctor, you should have no qualms about having diagnostic exams. 

Marcia Hartman, MS


¹ As noted in the Health Physics Society Position Statement on "Radiation Risks in Perspective,"
there are no demonstrated health effects for radiation exposures below 5,000-10,000 mrem (50-100 millisievert).