Jan. 15, 2008 -- In the last 30 years, the computerized tomography scan — more commonly known as the CT scan — has become a valuable study to aid in the diagnosis of illness or trauma. It is estimated that 62 million CT scans per year are performed in the United States, including 4 million on children.
Without a doubt, it's an important — and sometimes lifesaving — tool. But like most medical technologies, it has the potential to be a double-edged sword. Many parents and some physicians may not be aware of the amount of radiation delivered to a child undergoing a CT scan.
For example, a scan of the head delivers 100 times more radiation than a chest X-ray, and an abdominal scan is equivalent to about 500 chest X-rays!
Compare this to some other well-known procedures that deliver radiation into the body, and you'll see that CT scans come out near the top in terms of radiation exposure. An X-ray of the skull, for example, involves only about 1/25 of the radiation delivered during a typical CT scan.
And a barium swallow — a procedure used to screen the upper gastrointestinal tract — delivers the radiation equivalent of 150 chest X-rays, which is only a fraction of the amount of radiation delivered during a typical abdominal CT scan.
Cancer Risk May Be Higher for Children
This high dose of radiation is a potential cause of cancer, especially in children. Young children have many developing cells and growing organs, which makes them more susceptible to radiation injury. Children also have more years of life ahead of them, during which the injury from radiation may later be revealed.
While the benefit of diagnosis is an asset to the physician managing the patient, the potential risks from radiation are a serious concern. History is replete with cancers caused by unnecessary radiation in children. Rates of cancer have been studied on atomic bomb survivors. Based on these studies of radiation exposure, scientists have estimated the risk of cancer to be 1 in 1,200 for brain scans and 1 in 500 for abdominal scans.
Until statistics evaluate the long-term risks with the immediate benefits of CT scans done in the last 30 years, we need to have respect for the risks of CT scans and limit the radiation exposure to young children.
Dealing With the Problem
How can this be accomplished? First by modifying the output of radiation from CT scanners, since reducing the dosage for children is helpful. ALARA (As Low As Reasonably Achievable) is a concept proposed to physicians and radiologists doing CT scans. This automatic "scale down" is already present on scanners in most medical centers.
Second, consideration should be given to alternative nonradiation diagnostic studies such as magnetic resonance imaging (MRI) or ultrasonography. Unfortunately, MRI exams are more expensive and are not always available as an immediate test.
Third, and most effective, would be a reduction of the number of CT scans done. When a medical situation justifies the use of a CT scan, then it is an excellent test for diagnosis. In these cases, the benefits of a scan then outweigh the risk of the radiation and the risk of a missed diagnosis.
However an analysis of patients who have had CT scans done estimates that one-third of the scans appear not to be justified by medical need. Therefore, approximately 20 million adults and more than 1 million children in the United States may be irradiated unnecessarily every year.
Finally, it is important for parents to understand the purpose, benefits, as well as the risks of the procedure. In this age of medical technology, people have become familiar with CT scans — whether they have had one themselves or just heard the term on their favorite television show. They may see it as just another type of X-ray. But they must realize the specific risks associated with this screening tool.
Physicians, as well, must rise to the challenge. They must also know the number of past CT scans the child has undergone, as the radiation is cumulative over a lifetime. Many parents and physicians may find comfort in knowing that a CT scan was normal, at the time of injury or illness, when in fact it may not have been a medically necessary test.
Parents should have a clear understanding of the test their child is undergoing in an emergency. Appropriate use of this procedure is necessary to identify serious disease or injury, as well as protect the future health of the child.
However in many cases, a thorough review of the history of the patient and the symptoms, as well as a comprehensive examination and review of some basic studies — along with good communication with the family — can often be adequate to be assured that a CT scan is not needed at that time.
Alvin Miller is on the clinical faculty of the USC School of Medicine and the UCLA School of Medicine. Donald Miller is on the clinical faculty of the UCSD School of Medicine.