Published online February 1, 2008
PEDIATRICS Vol. 121 No. 2 February 2008, pp. 449-450 (doi:10.1542/peds.2007-3394)

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LETTER TO THE EDITOR

Radiation Risk to Children From Computed Tomography

Haresh Kirpalani, BM, MSc
Department of Neonatology
Children's Hospital of Philadelphia
Philadelphia, PA 19104

Claude Nahmias, PhD
Molecular Imaging and Translational Research Program
Graduate School of Medicine
University of Tennessee
Knoxville, TN 37920

To the Editor.—

We read the recent article by Brody et al¹ with interest. We fully agree that it is important to "provide pediatricians with information that will be helpful in discussions with patients and families/caregivers regarding the radiation risks of CT [computed tomography] examinations." Although the focus of the article was on CT examinations, confusion was introduced regarding radioisotope and other examinations. Representative doses were provided in their Table 1, which showed estimates of medical radiation doses for a 5-year-old child. However, the table did not account for confounders, which as the authors pointed out included "patient factors (such as age and size), technical factors (equipment settings and procedure length), and equipment model," none of which were provided for any of the procedures listed. Furthermore, the gender of the child is also relevant, at least for nuclear medicine procedures.

It helps to work through a concrete example: the effective dose for an ¹⁸F-fluorodeoxyglucose positron emission tomography scan is listed as 15.3 mSv for a 5-year-old child. The International Commission on Radiologic Protection gives an effective dose of 0.019 mSv/MBq for males and 0.025 mSv/MBq for females.² The amount of radioactivity administered to a 70-kg adult is typically 370 MBq, which results in an effective dose of 7 mSv, less than half the dose listed. It is correct that effective doses are greater in children than in adults. For very low birth weight infants, the effective dose has been empirically measured to be 0.21 mSv/MBq³; the typical amount of radioactivity administered to infants and children is of the order of 1.85 MBq/kg,^4,5 which results in an effective dose of 0.4 mSv for a 1-kg infant. For a 5-year-old child, the effective dose has been calculated to be 0.048 mSv/MBq. For a 5-year-old to be exposed to 15.3 mSv, the child would have had to be administered 320 MBq, the equivalent of an adult dose, unless the child weighed in at 173 kg. Applying rules of ALARA (as low as reasonably achievable), it is difficult to imagine how this amount of radioactivity could be administered to a 5-year-old child.

In the same table, the effective dose was equated to a number of chest radiographs. However, this comparison likely should not be made. The National Institutes of Health recommend that the total effective dose from a procedure be compared with the radiation exposure from natural background sources such as the sun, outer space, and radioactive materials found in the earth's air and soil, which is 3 mSv per year.⁶ We agree that the comparison with chest radiographs is inappropriate, because organs with different radiosensitivities will be exposed depending on the procedure. This comparison is even less appropriate with nuclear medicine procedures during which the administered radioactivity is distributed in the whole body but may accumulate in specific organs. For example, the dose to the bladder during an ¹⁸F-fluorodeoxyglucose positron emission tomography examination can be orders of magnitude greater than the effective (whole-body) dose.

For a report to provide guidance, it should be factual and present information that can be put in context, such as citing the technique used for the different procedures, or at the very least give the range of exposures that could be expected from these procedures. It should also provide the clinician with an appropriate comparison standard with which to discuss the risks with patients and their families or caregivers.⁶

REFERENCES

1. Brody AS, Frush DP, Huda W, Brent RL; American Academy of Pediatrics, Section on Radiology. Radiation risk to children from computed tomography. Pediatrics. 2007;120 (3):677 –682[Abstract/Free Full Text]
2. International Commission on Radiological Protection. Radiation dose to patients from radiopharmaceuticals (addendum 2 to ICRP publication 53). Ann ICRP. 1998;28 (3):1 –126[Medline]
3. Niven E, Nahmias C. Absorbed dose to very low birth weight infants from ¹⁸F-flurodeoxyglucose. Health Phys. 2003;84 (3):307 –316[CrossRef][Web of Science][Medline]
4. Skehan SJ, Issenman R, Mernagh J, Nahmias C, Jacobson K. FDG PET in the diagnosis of paediatric inflammatory bowel disease. Lancet. 1999;354 (9181):836 –837[Web of Science][Medline]
5. Andersen C, Kent A, Schmidt B, et al. Pulmonary ¹⁸fluorodeoxyglucose uptake in infants of very low birth weight with and without intrauterine inflammation. J Pediatr. 2003;143 (4):470 –476[CrossRef][Web of Science][Medline]
6. Radiation and your patient: a guide for medical practitioners—a Web module produced by Committee 3 of the International Commission on Radiological Protection (ICRP). Available at: www.icrp.org/docs/Rad_for_GP_for_web.pdf. Accessed December 12, 2007

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PEDIATRICS (ISSN 1098-4275). ©2008 by the American Academy of Pediatrics

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This Article Extract Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services E-mail this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Request Permissions Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Kirpalani, H. Articles by Nahmias, C. Search for Related Content PubMed PubMed Citation Articles by Kirpalani, H. Articles by Nahmias, C. Related Collections Office Practice Social Bookmarking                         What's this?