AJR: Imaging algorithm cuts number of CT exams, rad dose

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Kathleen Fink, MD, a neurologist at the University of Washington Medical Center in Seattle.

A structured imaging algorithm can decrease the cumulative radiation exposure and number of CT exams of the head among patients with aneurysmal subarachnoid hemorrhage, and the application of this method to patient populations with high CT usage may reduce cumulative radiation exposure while maintaining the clinical benefits of CT, according a study published online June 21 in the American Journal of Roentgenology.

Seeking to reduce the cumulative radiation exposure from CT of patients with aneurysmal subarachnoid hemorrhage, Michael L. Loftus, MD, of the department of radiology at New York-Presbyterian Hospital, Weill Cornell Medical College in New York City, and colleagues implemented the algorithm to serve as a guide to physicians in determining the most appropriate time points for detection of vasospasm with CT angiography (CTA) and CT perfusion imaging.

The single-site study included 60 patients admitted to New York-Presbyterian Hospital from October 2007 to June 2008 with aneurysmal subarachnoid hemorrhages; 30 patients were in the baseline group (before implementation of the imaging algorithm) and 30 patients were in the post-algorithm group. Researchers collected retrospective data for all CT exams of the head for the 30 baseline patients.

The authors recorded dose-length products for each CT exam and estimated resulting radiation exposure for each of the initial 30 patients. A subsequent imaging protocol included utilization guidelines to reduce radiation exposure in CTA and CT perfusion examinations performed to detect vasospasm in patients with aneurysmal subarachnoid hemorrhage as part of a departmental practice quality improvement project, and data on the 30 remaining patients in the post-algorithm group were analyzed 10 months after the implementation, explained the researchers.

Loftus and colleagues compared the means, medians and standard deviation estimates for both patient groups’ cumulative radiation exposure and absolute numbers of each CT exam.

Altogether, the researchers found that during the course of the study, 435 CT exams were administered, with 248 exams given at baseline and 187 exams given after implementation of the new protocol.

“With the new algorithm, the mean number of CT exams per patient was 5.8 compared with 7.8 at baseline, representing a decrease of 25.6 percent,” wrote the authors. “The number of CT perfusion exams per patient decreased 32.1percent, and overall, there was a 12.1 percent decrease in cumulative radiation exposure.”

Despite the fact that the authors focused their initial study on patients with aneurysmal subarachnoid hemorrhage, they noted that the results could be applied to revised CT guidelines to reduce radiation exposure among individual patients and the population.

“Our overall goal is to apply to other patient populations this concept of imaging algorithms as utilization guidelines for CT,” said Loftus.

The study concluded that further work is needed to build a framework for evaluating and implementing best clinical practices that support both quality patient care and radiation safety.