Answer to Question #11523 Submitted to "Ask the Experts"

Category: Pregnancy and Radiation — Proximity to radioactive persons

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

Q

I am a physician who is 12 weeks pregnant. I inadvertently saw a patient who was injected with 881 megabecquerels (MBq) of technetium-99m (99mTc) methylene diphosphonate (MDP) for a bone scan one hour prior to his visit with me. I spent one hour with him at a distance of approximately 0.6 meters (m).

Could you please advise on any risks to my developing baby? I'm wondering what dose the baby might have received and am particularly worried about an increased risk of cancer (both childhood and lifetime). Thank you so much for your time and help, it's very much appreciated. I've been losing sleep over this and would truly value your expert opinion.

A

The calculated dose that you might have received is below the dose that could cause harmful effects for the baby.

According to the National Council on Radiation Protection and Measurements, the dose received in one hour at a distance of 0.6 m from a patient receiving the 99mTc MDP is about 0.06 millisieverts (mSv). The dose received for five minutes right beside the patient is about 0.02 mSv. The total estimated dose you may have received is about 0.08 mSv.

The dose to the baby is much less than that, probably even zero, because your abdominal tissue acts as shielding. 99mTc-99 emits low-energy gamma radiation, much of which would be absorbed in your abdominal tissue before even reaching the baby. So the dose to the baby is likely between zero and 0.06 mSv.

The minimal dose required to cause harmful effects to the baby is about 100 mSv (Wagner et al.). In this case, the radiation dose to your baby is well below any level that could cause harmful effects.

Remember, even if you are healthy and young and have no reproductive problems or family history of reproductive problems, your risk for birth defects is 3% and for miscarriage, 15%.

Kelly Classic, Certified Medical Health Physicist

References

  • National Council on Radiation Protection and Measurements. Sources and magnitude of occupational and public exposures from nuclear medicine procedures. Bethesda, MD: National Council on Radiation Protection and Measurements; NCRP Report No. 124; 1996.
  • Wagner LK, Lester RG, Saldana LR. Exposure of the pregnant patient to diagnostic radiations. Madison, WI: Medical Physics Publishing; 1997.
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.
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