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| |  Unindicated CT Series Results in Unnecessary Radiation Exposure for Patients CHICAGO -- December 4, 2009 -- A large proportion of patients who undergo abdominal/pelvic computed tomography (CT) receive unindicated and unnecessary additional image acquisition resulting in excess, avoidable radiation exposure, according to a study presented here on November 30 at the Radiological Society of North America (RSNA) 95th Annual Meeting. “It is the responsibility of all physicians who work with ionising radiation to ensure that the dosage is as low as reasonably achievable without compromising the patient’s well being,” said Kristie Guite, MD, University of Wisconsin, Madison, Wisconsin. “Our study found that this principle is not being followed in many practices.” To determine the frequency of unindicated additional scanning and the resultant excess radiation exposure to patients, the researchers reviewed the appropriateness and radiation dose of abdomen and pelvis CT exams for 500 patients performed at outside institutions and submitted to University of Wisconsin for interpretation. The patients ranged in age from 9 months to 91 years, with most between 30 and 50 years old. There were a total of 978 series for the 500 patients. Using the American College of Radiology (ACR) Appropriateness Criteria, 35.3% (345/978) of the CT series in 52.2% (261/500) of the patients were determined to be unindicated. The most common unnecessary exam was delayed-phase imaging, accounting for 268 (77.7%) of the 345 unnecessary series. In delayed-phase imaging, several images of the same region are obtained a short period of time after contrast injection to detect changes. Among the 500 patients, the mean excess radiation dose per patient from unnecessary scans was 11.3 mSv, equivalent to the dose received from 113 chest x-rays or 3 years of naturally occurring background radiation. “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, MD, University of Wisconsin, Madison, Wisconsin. “It is certainly easier to select an ‘every size fits all’ approach.” The researchers also noted a possible connection in some cases between additional scanning and increased payment, such as performing both non-contrast and contrast-enhanced scans when only 1 series was indicated. Efforts are ongoing to protect patients from unnecessary radiation exposure from medical imaging procedures, including the Image Gently initiative for safety in paediatric radiology and an ACR-RSNA task force for adult radiation protection. In addition to following strict appropriate imaging utilisation standards, radiologists and medical physicists stress the importance of minimising dose without sacrificing diagnostic ability. Advances in CT technology over recent years have markedly decreased dose while maintaining optimal image quality. Dr. Guite advises patients not to be unduly alarmed when 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 suggests that patients ask their physicians about the risks and benefits of the proposed exam and inquire at the CT facility as to the number of series that will be performed, and if a smaller number of series would be sufficient. SOURCE: Radiological Society of North America
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