Radiation Imaging: Slideshow

In February 2010, an initiative to reduce unnecessary radiation exposure from medical imaging was announced by the US Food and Drug Administration (FDA) in response to the increased use of computed tomography (CT) scans and other imaging studies, as well as concerns over radiation exposure. The announcement follows the publication of 2 studies projecting cancer risk associated with radiation exposure from current CT use, as well as an FDA report that more than 250 patients in 1 region of the United States had received up to 8 times the expected dose of radiation during CT perfusion scans.^[1]

As a comparison, radiation therapy for cancer typically requires doses of 20-60 Gy (20-60 Sv for x-ray equivalent, or 1-3 million chest x-ray equivalents). The US population's total exposure to ionizing radiation has nearly doubled over the past 2 decades, a rise largely attributable to increased exposure from CT, nuclear medicine, and interventional fluoroscopy.^[2] Although these studies comprise only approximately 26% of the imaging procedures using radiation that are conducted annually in the United States, they contribute 89% of the total yearly exposure to radiation from medical imaging.

As of 2009, it was estimated that approximately 70 million CT scans are conducted annually in the United States, a threefold increase from 1993. The increase in use is among the areas the FDA initiative seeks to address.^[3]

These estimates highlight several areas of CT scanning that make significant contributions to the total cancer risk, including several scan types and age groups with a high frequency of use or scans involving relatively high doses, in which risk-reduction efforts may be warranted.^[4]

Radiation doses from commonly performed diagnostic CT examinations are higher and more variable than generally quoted. Median effective doses have been found to range from 2 mSv for a routine head CT scan to 31 mSv for a multiphase abdomen and pelvis CT scan, with a mean 13-fold variation between the highest and lowest dose for each CT study type.^[5] These findings highlight the need for standardization in radiation dose and better quality assurance.

CT is extremely valuable and can be a life-saving tool for diagnosing illness and injury in children. For an individual child, the risks of CT are small and the individual risk-benefit balance favors the benefit when used appropriately. However, there are 3 unique considerations in children: (1) children are considerably more sensitive to the effects of radiation; (2) they have a longer life expectancy than adults; and (3) they receive a higher dose than necessary when adult CT settings are used, placing them at increased risk for cancer compared with adults exposed to identical CT settings.

CT settings for children can be reduced significantly while maintaining diagnostic image quality. When appropriate, other modalities that do not use ionizing radiation should be considered, such as ultrasound or magnetic resonance imaging.^[6]

Reduction of unnecessary radiation exposure from medical imaging will involve efforts in multiple areas. Through this initiative, the FDA seeks to collaborate with professional organizations and accreditation and quality assurance organizations to monitor and assess the impact of these efforts.

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For more information, see the following resources:

• eMedicine, Clinical Procedures: Ionizing Radiation Exposure, Medical Imaging
• FDA White Paper: Initiative to Reduce Unnecessary Radiation Exposure from Medical Imaging
• FDA Public Health Notification: Reducing Radiation Risk from Computed Tomography for Pediatric and Small Adult Patients
• National Cancer Institute, Radiation Risks and Pediatric Computed Tomography (CT): A Guide for Health Care Providers

Contributor Information

Author
Judy Lin, MD
Medical Writer
eMedicine from WebMD
Bellaire, Texas

Disclosure: Judy Lin, MD, has disclosed no relevant financial relationships.

Editor
Felix Chew, MD
Professor, Department of Radiology, Vice Chairman for Radiology Informatics,
Section Head of Musculoskeletal Radiology
University of Washington
Seattle, Washington

Disclosure: Felix Chew, MD, has disclosed no relevant financial relationships.