Children continue to undergo many more computed tomography (CT) scans than in the past, and the doses of radiation they are receiving may increase the risk of certain types of cancer, according to a study published in JAMA Pediatrics today.
To better understand the trends in pediatric CT and the risks posed to children by such scans, Diana L. Miglioretti, PhD, a senior investigator at the Group Health Research Institute and professor of biostatistics at the University of California–Davis School of Medicine, and her colleagues evaluated the use of CT scans between 1996 and 2010 in children younger than 15 years in 7 US health systems. They found that the use of CT doubled among children younger than 5 years (from 11 to 20 scans per 1000 children) and almost tripled for older children (from 10.5 to 27 per 1000 children) between 1996 and 2005. But by 2010, CT use had decreased to 15.8 scans per 1000 children younger than 5 years and 23.9 per 1000 children children aged 5 years and older.
The team found that the radiation doses that children were exposed to varied considerably and that the cancer risks associated with exposure were estimated. For example, exposure to abdominal CT scans posed the greatest cancer risk, with an estimated 1 case of abdominal cancer among every 300 to 390 girls scanned or among every 670 to 760 boys scanned.
But the team suggested that reducing the highest 25% of radiation doses might reduce 43% of CT-related cancers.
Dr Miglioretti discussed her team’s findings with news@JAMA:
news@JAMA: Why do you think the use of CT scans in children has increased?
Dr Miglioretti: One thing is that CT is a very sensitive and accurate diagnostic tool. It is very useful in children, especially because other diagnostic technology like magnetic resonance imaging [MRI] requires children to be still for a long time. CT is very fast.
news@JAMA: You found that CT use remains elevated compared to the 90s, but has dipped somewhat since 2005. Why?
Dr Miglioretti: I personally believe the decrease is due to campaigns to reduce radiation exposure in children, such as the Image Gently campaign.
news@JAMA: Despite some improvements in CT use, you still found that current rates of CT use in children may raise cancer risk. How did you estimate cancer risk associated with CT use in children?
Dr Miglioretti: First, we calculated actual radiation exposure for a random sample of hundreds of CT scans of each of the 4 most frequent types (head, chest, abdomen, and spine) by extracting the technical parameters used for each scan associated with exposure. We used a new modeling approach from the National Cancer Institute to estimate organ doses from these exams, and used models from the BEIR-VII report to project the cancer risks due to radiation exposures of those levels.
news@JAMA: Were the exposure levels you found consistent with what other studies have found?
Dr. Miglioretti: We found exposure levels were highly variable for exams of the same type. In terms of risk, we found the cancer risks associated with CT exposure in our study were higher, which was due to the variation in radiation exposure we found. Prior studies used mean doses reported in the literature, rather than actual exposure levels.
news@JAMA: Why do you think the doses varied so much?
Dr Miglioretti: We suspect it is due to differences in radiologists’ preferences and differences in technologists’ knowledge of the importance of reducing radiation exposure in children. Differences in the type of scanner and differences in patients’ sizes might also contribute.
news@JAMA: What do you think physicians should learn from your study?
Dr Miglioretti: We can drastically reduce the number of cancers caused by CT if we only use CT scans on children when they are medically necessary. We need to be judicious in our use to make sure they are medically necessary and that there is not another diagnostic modality we can use, such as ultrasound. If CT is used, we need to optimize the dose for children. The Image Gently website is a great resource for both physicians and parents.
news@JAMA: What should parents know about your results and their implications for CT use on their child?
Dr Miglioretti: It is important to know that if the CT is medically necessary, the benefits likely outweigh any individual cancer risks. The increased risks become a concern when we look at the whole population, but the risk to the individual child is very low. Parents should also feel empowered to discuss their concerns with their physician. They should ask the physician whether CT is medically necessary and how it will change the clinical care for their child. They should ask whether there are alternatives; could MRI or ultrasound be used—or other approaches, such as waiting? If CT is medically necessary, they should ask whether the radiation dose will be optimized for their child to keep the dose as low as possible.