On January 3, 2011, a group of physicians led by Dr. Adam Dorfman of the University of Michigan Medical School published results of the first large study on the rates at which children are exposed to ionizing radiation through use of medical imaging procedures. Using population samples from 5 large U.S. health care markets, the doctors determined that, between 2005 and 2007, almost 43% of children under 18 were subjected to imaging procedures which involved the use of ionizing radiation.1 Of this group, almost 12 percent received computed tomographic (CT) scans, and 3.5 percent underwent 2 or more CT scans, usually of the head region.
Ionizing radiation, which is employed to take medical x-rays, is known to be carcinogenic, i.e. it can cause cancer by damaging genetic material in cells (as well as other cause other genetic defects). CT scans, which can provide three-dimensional images of organs through the use of rotational x-rays, deliver much higher doses of radiation than conventional x-rays (plain radiography). The dose of radiation from one CT scan of the abdomen, for example, is equivalent to 400 chest x-rays. There is no level of ionizing radiation exposure that is considered free of carcinogenic risk.
CT scans have become increasingly common diagnostic tools due to convenience, high quality images and widespread availability (partially due to manufacturers’ sales efforts). However, with the better diagnostic accuracy of CT scans comes greater exposure to ionizing radiation, and thus increased lifetime risk of cancer. This risk increases with each CT scan performed, as the effects of ionizing radiation are cumulative. Researchers estimate that up to 2 percent of all cancers in the U.S. are caused by exposure to radiation from CT scans (Brenner).2
Of particular concern is the dramatic rise in the use of CT scans in children under 18. As children’s tissues are still developing, they tend to absorb more radiation than adults and are thus more susceptible to related health effects; the younger the child is, the greater is his or her risk. Researchers estimate that 10 million children worldwide (Shenoy-Bangle), and 4 million in the U.S. (Brenner), receive CT scans each year. Such prevalence is due, in part, to the fact that the machine can capture an image in less than one second, which eliminates the need for sedation of children during other, longer diagnostic imaging procedures.
The choice to perform CT scans on people, especially children, should result from clinical need and benefit that outweighs the risk of cancer and other genetic damage. Unfortunately, many unnecessary CT scans are conducted as a result of convenience, malpractice avoidance (“defensive medicine”), or lack of communication between members of the medical community which results in repetitive scanning. Lack of knowledge about safer CT scan use by clinicians (for example, sufficient understanding of optimal radiation dose for both children and adults) as well as deficiency of standardized safety regulations also contribute to over-exposure of x-ray radiation.
Researchers estimate that approximately one-third of all CT scans, including those involving children, are not justified by medical need, and could be eliminated or replaced with alternate imaging modalities which do not utilize ionizing radiation:
Ultrasound (sonography) – through the use of high-frequency sound waves, clinicians can capture real-time images of soft tissues like organs and muscles. In addition to viewing fetal development, ultrasound is commonly used to see the heart and watch blood flow through valves, as well as to diagnose osteoporosis and perform biopsies. The depth of penetration of ultrasound is limited, though, which makes it more suitable for evaluation of targeted areas of the body.
Most of the CT scans performed on children are for the pre-surgical diagnosis of appendicitis, which, researchers say can also be achieved as accurately and cost-effectively using ultrasonography (Brenner). Researchers also have reported that chest CT scans have not produced any more clinically useful data than chest ultrasounds when used to detect complications arising from pneumonia (Kurian). Although there are no known risks of ultrasound, it can cause slight tissue heating and cavitation for which the long-term effects are not known (some organizations are advocating prudent use of fetal ultrasound to account for this lack of certainty).
Magnetic resonance imaging(MRI) – the MRI uses strong magnetic fields and radio waves to show cross-sectional images of organs and other internal structures in the body, and is advantageous in that it can provide more detailed images than x-rays, CT scans, or ultrasounds. Generally used to diagnose abnormalities in the brain, joints, and abdominal organs, the MRI is also used to detect tumors and cysts throughout the body, as well as some heart problems.
While the MRI does not emit ionizing radiation, it does use radio waves which can cause non-thermal health effects and slight heating of tissues (a lesser evil when compared with the carcinogenic risk associated with ionizing radiation). MRI imaging can also be costly. While MRI has historically required the sedation of children due to long scan times, recent technical advances have made possible the acquisition of quick, motion-free images.
Thermography– a form of infra-red imaging used to detect heat, thermography can indicate the presence of inflammation, which is often present in pre-cancerous and cancerous cells. In recent years, thermography has proved efficacious in the diagnosis of breast cancer in adult women, and is gaining increasing popularity as an alternative to mammography. While pediatric use of thermography is not common, this safe procedure shows promise for diagnosis of inflammation-related illness in children.
Knowledge is Power
As patients, or parents of patients, we can protect ourselves and our children by becoming more aware of radiation exposure. Keeping copies of all of our medical records, especially x-rays (including dental), mammograms and CT scans, can help us assist our physicians in assessing possible cancer risk associated with future x-rays and CT scans. It may also help to keep track of, if not altogether avoid, other exposure to x-ray radiation (e.g. that from airport security body scanners). Lastly, in order to help us protect ourselves against unnecessary, associated health risks, we can do our own research on diagnostic medical devices before agreeing to examination with them.
1. In addition to CT scans, flouroscopy and nuclear medicine are other medical imaging technologies which use higher doses of ionizing radiation than conventional x-rays. The use of mammogramsto detect breast cancer has also raised concerns about ionizing radiation.
2. Estimates of rates of cancer risk based on CT scan use are based upon radiation-related cancer rates of adult and children atomic bomb survivors who were exposed the same radiation doses as those delivered during CT scans.
References and Resources:
- The Associated Press. “Study of Children Raises Concerns over Radiation.” NYTimes.com, Jan 3, 2011.
- Dorfman AL, Fazel R, et al. Use of Medical Imaging Procedures with Ionizing Radiation in Children. Arch Pediatr Adolesc Med. Published online January 3, 2011. [Abstract.]
- The U.S. Environmental Protection Agency. Radiation Protection: Health Effects. EPA.gov.
- Brenner DJ, Hall EJ. Computed Tomography – An Increasing Source of Radiation Exposure. N Engl J Med 2007;357:2277-2284.
- Shenoy-Bangle A, Nimkin K, Gee MS. Pediatric imaging: Current and emerging techniques. J Postgrad Med 2010;56:98-102.
- The U.S. Food and Drug Administration (FDA). White Paper: Initiative to Reduce Unnecessary Radiation Exposure From Medical Imaging. FDA.gov. Feb. 2010.
- Kurian J, Levin TL, et al. Comparison of Ultrasound and CT in the evaluation of pneumonia complicated by parapneumonic effusion in children. Am J Roentgenol. 2009 Dec;193(6):1648-54. [Abstract.]
- FDA. Medical Imaging. FDA.gov.
© 2011 HeartMD Institute. All rights reserved.