Improved technology! Increased usage!
Is there any concern for long-term radiation effects?
By- Dr. Jonathan Wood

CT scan usage has increased dramatically in the last 20 years. CT scans are a great diagnostic tool, but what is the risk associated with increased usage? Is there a significant increased risk of cancer in people receiving all these CT scans? Experts are working on the answer to this difficult question and the answer is not as conclusive as we would hope.

Medical diagnosis has benefitted greatly in recent years from marked improvements in CT scan technology and the subsequent increased availability of scans. “Helical CT scanning” and “multidetector” scanners have resulted in improved image resolution and a dramatic decrease in the time needed to obtain these images.

These changes are cited as the main reason for the impressive increases in CT utilization. In the past 10 years alone, CT use has increased 700%. An estimated 62 million CT scans are done annually in the US today, compared with 3 million done in 1980. And why the focus on CT scans rather than other radiology tests? The answer: CT scans involve much more radiation than simple x-rays or other radiology tests. The numbers illustrate this - - although CT scans account for only 15% of the exams involving ionizing radiation, they collectively account for approximately 70% of the total radiation delivered!

An example - - one abdominal CT scan involves a radiation dose equivalent to 250 chest x-rays!

Children account for 10-15% of CT scans in the US and the annual number continues to increase. This is important because children are likely more susceptible to the harmful effects of ionizing radiation. The main issues:
1. Growing children have more rapidly dividing cells, exactly the cells most affected by radiation. Some estimate that a radiation dose administered to a child has a 10-fold increase in the cancer-causing potential as the same dose given an adult.
2. Children have a longer lifetime over which radiation-related cancers could evolve.
3. Depending on the location of the scan, CT scanning is not always tailored to the size of the patient, as it should be.

So is there a true risk? The answer is a qualified “yes”.

The baseline risk of cancer in the US population is already about 20%. A single abdominal CT in a child is thought to increase that risk over a lifetime by 0.1% to 0.3%. Given that 30% of people who have one CT have additional ones later, this may be a conservative overall risk. The data is difficult to interpret, given all the other factors that contribute to the risk of cancer, but it nonetheless seems quite clear that minimizing the number of CT scans is a good idea.

Importantly, any reduction in CT use has to be balanced against the fantastic diagnostic value offered by CT scan technology used in the right situation. The immediate risk of not getting the information is often much higher than the long-term risk of developing a cancer.

So what can we do?
• As patients and parents, we need to ask questions and make sure that there aren’t other ways to get the same information. We need to realize that “just checking” involves real risk and we shouldn’t ask for CT scans that are not going to help with the problem at hand. Many CT scans are ordered because people ask for them!
• As physicians, we need to order these tests judiciously and work with our institutions to perform them in the safest possible manner in children. We also need to continually ask if there are other tests that can offer the same information with less risk - - tests like ultrasound, which don’t involve ionizing radiation.

Online Resources:

An FDA handout for consumers: http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm048578.htm

An NCI/NIH webpage for docs: http://www.cancer.gov/cancertopics/causes/radiation/radiation-risks-pediatric-CT

“Image Gently” - a program sponsored by the Society for Pediatric Radiology: http://www.imagegently.org

CNN article on increased CT usage: http://thechart.blogs.cnn.com/2011/04/05/kids-ct-scans-increase-fivefold/

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