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

Category: Nuclear Medicine Patient Issues — Diagnostic Nuclear Medicine

The following question was answered by an expert in the appropriate field:

Q

I recently had a nuclear stress test done using Myoview. I was told that for the resting part I received 444 MBq of Myoview technetium-99m and for the stress part I received another 907 MBq 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 5 millisieverts.

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)?
     
A

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 99mTc (technetium-99m) Myoview. For this study, your exposure was approximately 9.6 millisievert (mSv). 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 50 mSv 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 3 mSv 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 4 mSv. 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, 9.6 mSv, 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 50-100 mSv.

Ask the Experts is posting answers using only SI (the International System of Units) in accordance with international practice. To convert these to traditional units we have prepared a conversion table. You can also view a diagram to help put the radiation information presented in this question and answer in perspective. Explanations of radiation terms can be found here.
Answer posted on 19 February 2008. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.
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