Answer to Question #11384 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

My questions are based on the assumption that during renal scintigraphy for children, there is a certain amount of radiation passing through the kidneys, ureters, and bladder, and thus radiation comes really close to the gonads (doses up to 1.0–1.8 millisieverts [mSv]). Specifically, my questions are:

  1. What are the risks of genetic damage (mutations) to oocytes in gonads in repeated dimercaptosuccinic acid (DMSA) kidney scans in children less than five years old?
  2. What scientific research renders this investigation safe (animal studies, longitudinal studies)?
  3. How many times a year is it considered safe to have these scans?
  4. Do today's recommendations have a good safety margin?
A

Thank you for your thoughtful questions to "Ask the Experts." There are no known risks at the low radiation-absorbed doses from renal scintigraphy.

According to Treves (page 65), the administered activity to a five-year-old child for a DMSA scan would be 37 megabecquerels (MBq), the radiation dose to the ovaries would be 0.5 milligray (mGy), and the radiation dose to the testes would be 0.3 mGy. From the tables of the International Commission on Radiation Protection (ICRP) Report 53, page 186, for an administration of 37 MBq the dose to the ovaries would be 0.41 mGy, and the dose to the testes would be 0.23 mGy.

Natural background radiation averages 3 mSv annually in the United States, so you can see that the low gonadal doses from DMSA kidney scans are insignificant. Furthermore, low doses of radiation stimulate numerous repair mechanisms (over 150 enzymes have been found to be associated with radiation repair), and any damage that might occur would be repaired. Ten DMSA scans a year would also be insignificant from a radiation safety point of view.

There is no need to worry about these low radiation-absorbed doses.

Carol S. Marcus, PhD, MD
Professor of Molecular and Medical Pharmacology (Nuclear Medicine), of Radiation Oncology, and of Radiological Sciences, David Geffen School of Medicine at University of California, Los Angeles

References
International Commission on Radiation Protection. Radiation dose to patients from radiopharmaceuticals. Oxford: Pergamon Press; ICRP Publication 53; 1988.

Treves ST. Pediatric nuclear medicine. 1st ed. New York: Springer-Verlag; 1985.

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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