COMMENTARY |
Children, Computed Tomography Radiation Dose, and the As Low As Reasonably Achievable (ALARA) Concept
Department of Pediatric Imaging, Children’s Hospital of Michigan, Detroit, MI 48201-2196
Abbreviations: CT, computed tomography • ALARA, As Low As Reasonably Achievable
It is apparent that without extrapolation or animal experimentation, low-dose radiation has a small but statistically significant individual risk of excessive cancer over a child’s lifetime.1–3 This data was recently published as part of the ongoing, >50-year study of the survivors of the atomic bomb that cost $500 million. The kind of radiation and doses these individuals were exposed to is similar to that from computed tomography (CT) (Fig 1). The total body effect of the A-bomb versus the more localized effect of medical radiation makes little difference on the outcome. Figure 2 is an explanation of terminology of the radiation doses used. There is clearly an overlap between the CT doses currently used and the low doses that the atomic bomb survivors received.
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This information should not be a cause for panic but rather a heads-up on how we can increase the benefits of CT’s diagnostic value while decreasing the individual and public health risks of carcinogenesis.4–6
First, we must be more appropriate in what tests we order. It is generally felt that up to one third of CTs performed on children are not pertinent to either the diagnosis or management nor is it necessarily the best test. These numbers are estimates as there is little outcome data studying morbidities before and after CT for common conditions. An example of this is the child who is imaged because of headaches. The yield is quite low no matter what modality is used, but if one uses magnetic resonance imaging (MRI), the risks of radiation are nonexistent (although there may be other risks of MRI we do not know about).
Another example as to whether we are doing appropriate imaging is in our cancer protocols. The oncologic protocols for follow-up of patients with abdominal cancers or lymphoma have never been looked at for the outcomes. What would happen if we would decrease the number of CTs?
We desperately need outcome studies if we are to improve the benefit/risk balance. However, in medicine we often must proceed with incomplete information. It is prudent to utilize the As Low As Reasonably Achievable (ALARA) concept and have an ALARA radiation dose—this means decreasing the number of radiation-producing tests when clinically feasible.4 We must thoroughly understand the advantages and disadvantages of all of the modalities, particularly those such as ultrasound and MRI.
In many instances the radiologist has made CT the easiest test to get. In today’s milieu of bureaucratic chaos, the physician naturally grasps the easiest test. We are the children’s advocate and must push the system to make it more user-friendly for obtaining the best test with the least risk in each patient. As CT use is being popularized in the diagnosis and work-up of more common diseases such as appendicitis, renal colic, orthopedic abnormalities, and craniosynostosis, we must understand the risks we are exposing the child to.
To obtain the best test, there should be a continuing dialogue between the ordering physician and the pediatric imager. Our 2 disciplines working together should be able to eliminate most unnecessary tests without any untoward effects on a child or missed or delayed diagnoses. The radiologist can play a major role in reducing the radiation dose. In this issue, Drs Frush, Donnelly, and Rosen7 discuss these issues. They superbly demonstrate the increased radiosensitivity of children (10 times that of middle-aged adults), and note that the technical parameters used by nonpediatric radiologists far exceed those necessary for a diagnostic study.8–10
It is crucial that the pediatrician (or other ordering physician) understand that the hospital or imaging center is using a pediatric protocol, ie, special modification of techniques taking into consideration the size (weight) of the child. When pediatric protocols are not used, the child may be receiving an excessive dose of radiation. As Donnelly et al11 point out, there are now parameters available for children. These are a starting point but much more research has to be done into various ways to reduce CT dose.
By involving the ordering physician, getting the manufacturers to make it easy to use the right technical parameters and hard to overdose the child, and having the radiologist as an educator to both the clinician and technologist, we will succeed in lowering the radiation dose in CT. By working together, we will succeed in tipping the benefit/risk scale even further in favor of the child.
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FOOTNOTES |
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Received for publication Aug 21, 2002; Accepted Mar 25, 2003.
Address correspondence to Thomas L. Slovis MD, Department of Pediatric Imaging, Children’s Hospital of Michigan, 3901 Beaubien Blvd, Detroit, MI 48201-2196. E-mail: tslovis{at}med.wayne.edu
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REFERENCES |
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- Slovis TL, ed. The ALARA concept in pediatric CT intelligent dose reduction. Multidisciplinary conference organized by the Society of Pediatric Radiology, August 18–19, 2001. Pediatr Radiol2002; 32 :217 –313. E publication, March 6, 2002[CrossRef][Web of Science][Medline]
- Food and Drug Administration. Reducing Radiation Risk From Computed Tomography for Pediatric and Small Adult Patents [public health notification]. Rockville, MD: Food and Drug Administration; November 2, 2001
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[Free Full Text]
PEDIATRICS (ISSN 1098-4275). ©2003 by the American Academy of Pediatrics
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