Recently, my child underwent a computed tomography (CT) scan of his appendix. We were concerned that he had appendicitis, so we took him to the hospital ER. Last year, I had read that CT scans in children may deliver too much radiation. Are CT scans safe? Should I be concerned about other X-rays or radiological investigations?
An article published (February, 2001) in the American Journal of Radiology (AJR) drew attention to the fact that pediatric CT scans may have provided excessive amounts of radiation. The authors called for careful monitoring of patients because of an increased, calculated risk for developing cancer due to CT scan radiation. As well, it was pointed out there was a pressing need for further research into methods for reducing the amount of radiation.
Based on the recent number of publications in the academic field, regarding the safety of CT scans in the pediatric population, there is some good news: children are far safer now than they were in the past. In fact, there has been enough concern to have led to a major reduction in the amount of CT radiation over the past 5 years or so. But there is still some room for improvement.
Some pediatric radiologists have likened the continued efforts to reduce radiation from CT scans to similar efforts in the 1970s, when the radiation received during mammography was considered too high. Since 1974, reductions in radiation doses from mammography have been reduced by almost 90%. This was mainly the result of research combined with strong public advocacy, and ultimately legislation.
According to the web site of the Canadian Association of Radiologists (www.car.ca), the scientific unit of measurement for a dose of radiation – known as the effective dose - is the millisievert (mSv). The average person in North America receives an annual effective dose of 3 mSv from natural occurring radioactive materials and cosmic radiation. These natural background doses vary from one geographic area to another. For example, people living at higher elevations receive about 1.5 mSv more per year than those living at sea level.
The added dose from cosmic radiation during a coast-to-coast round trip flight in a commercial airplane in North America is about 0.03 mSv. The largest source of background radiation originates from radon gas found in our homes, amounting to about 2 mSv per year.
The average exposure from a straight chest x-ray is equivalent to the amount of radiation one experiences from natural surroundings in ten days. It may be lower in some pediatric hospitals, which are on the cutting edge in reducing radiation exposure. Even in the mid-1980s, the Alberta Children's Hospital pioneered in its efforts to reduce pediatric radiation.
Abdominal CT scans deliver more radiation than a cranial CT scan, 10 mSv and 2 mSv respectively (see www.radiologyinfo.ca). Given the previously mentioned AJR article from 2001 created a major stir, both in the professional and lay communities, a number of research efforts have attempted to further reduce CT radiation by determining the age, weight, and body composition of the child.
In a press release from December 19, 2005, Australian researchers from the Children's Hospital at Westmead and Sydney Universities announced that trials had been launched to create a new atlas of child body types. This would allow radiation doses in CT scans to be estimated more accurately for children. Thus, the use of an accurate dose calculator would allow radiographers a better shot at reducing unnecessary radiation exposure. The researchers also pointed out that CT doses in children vary by as much as 3600% between different clinical centers.
Dr. S.M. Sane, writing a commentary for the American Academy of Pediatrics on this topic, remains highly critical of the mainstream media. In particular, he criticized the influential newspaper USA TODAY which splashed the title "CT scans in children linked to cancer later" on a full page article (January 22, 2001). Needless to say, this information created much anxiety and debate at the time.
Even the authors (based out of Columbia University) of the 2001 AJR article, which also questioned the safety of CT scans, admitted that their research was based on estimates, not on any proven or statistical data from CT scans in children.Where do all of these various concerns leave parents, especially those with very small children? Here are some suggestions based on a published commentary in Pediatrics, the official journal of the American Academy of Pediatrics:
- Although CT scans provide detailed images of many regions of the body (enabling clinicians to study bone, soft tissues and blood vessels all at the same time), one should always ask if it is truly necessary. Approximately 30% of all pediatric CT examinations a few years ago, according to a commentary in Pediatrics, were unwarranted.
- Consideration should be given to other imaging methods, such as MRI or ultrasound, if clinically indicated.
- Abdominal CT scans should be done in a focused fashion. Sometimes an automatic inclusion of the pelvis is not required, and only the abdominal organ in question can be imaged.
- A 50% reduction in radiation can be achieved when CT scans are done under contrast (where Intravenous material is injected into the patient and then studied in various phases) and only post contrast exposure is allowed, as opposed to both pre- and post-contrast radiation.
- Enquire if the center doing CT scans on your child adhere to the latest recommendations, which are routinely updated based on current research. The Society for Pediatric Radiology (www.pedrad.org) serves as an academic forum to improve efforts toward safer radiation doses.
It may also be of interest to get more information about different doses of radiation associated with various other studies. For a detailed list of common imaging procedures, such as voiding cystourethrograms, bone densometry and many other studies including mammography, see www.radiologyinfo.org and click on "Safety". It may surprise you how much naturally-occurring background radiation exposures we all get annually, and also how X-ray safety continues to evolve over time.
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