A new study just presented during the annual meeting of the Radiological Society of North America (RSNA) indicates a significant portion of patients undergoing abdominal/pelvic computed tomography (CT) receive unindicated additional image acquisition that results in excess and avoidable radiation exposure.

The study is entitled "Excess Radiation Exposure in Abdominal Computed Tomography: An Audit of Unindicated Additional Series." According to the abstract of the study, the research was undertaken in light of current media concern about excess medical radiation, particularly with CT usage. The study focused on a particular area not examined previously: excess radiation related to additional series (such as routine non-contrast or delayed scans). The study set out to determine the frequency of unindicated additional scanning and the resultant excess radiation exposure.

CT exams image a patient using a CT scanner and may involve injection of an intravenous contrast agent. Each image taken is known as a series. Generally multiple series are not necessary except for certain conditions.

The study involved 978 series for 500 patients, in age range from nine months to 91 years, with most between 30 and 50 years old. The results found unindicated series in 52.2% of exams, or 35.3% of all series. The most common series was delayed phase imaging in 77.7% of the unnecessary series. The mean total radiation dose per patient from unnecessary scans was 11.3 millisieverts. Extrapolation of the mean dose over the total number of abdomen/pelvis CT scans performed in the U.S. yearly would result in an excess lifetime attributable risk of 0.1% for those patients undergoing an abdomen/pelvis CT exams. The practice of adding such series is common, but the study concludes a potential public health danger exists without any balance of associated clinical benefit.

"It is the responsibility of all physicians who work with ionizing radiation to ensure that the dosage is as low as reasonably achievable without compromising the patient's well being," said presenter Kristie Guite, M.D., radiology resident at the University of Wisconsin (UW) in Madison, in an RSNA press release. "Our study found that this principle is not being followed in many practices."

"We suspect that at many institutions there is a lack of focus on selecting CT protocols tailored specifically to answer the clinical question," said coauthor J. Louis Hinshaw, M.D., assistant professor of radiology at UW - Madison. "It is certainly easier to select an 'every size fits all' approach."

The RSNA notes that major efforts continue to protect patients from excess radiation exposure due to medical imaging procedures, including the Image Gently initiative (for pediatric radiology) and an ACR-RSNA task force for adult radiation protection.

However, Dr. Guite also advised patients not to be alarmed if their physician orders a CT exam. "The use of CT has been a huge benefit to human health," she said. "When used appropriately, the benefits of the diagnostic information obtained with CT far outweigh the potential risks."

Dr. Hinshaw then suggested that patients ask their physicians about the risks and benefits of the proposed imaging, and also ask the CT facility about the number of series to be taken, and if a smaller number would be sufficient.

Coauthors of this study are Frank N. Ranallo, Ph.D., and Fred T. Lee, M.D.

Watch for an additional report on this topic forthcoming in DOTmed News.

Read more:

RSNA Release: http://www.rsna.org/media/pressreleases/pr_target.cfm?ID=443

Abstract: http://rsna2009.rsna.org/search/event_display.cfm?em_id=8001700&printmode=y&autoprint=n

Read DOTmed's update to this story:
Many CT Series Unnecessary, Study Finds
https://www.dotmed.com/news/story/10893/