Valkyrie Computer Program Tracks Cumulative CT-Related Radiation Exposure

Norra MacReady

May 06, 2010

May 6, 2010 (San Diego, California) — A new method of tracking radiation doses delivered by computed tomography (CT) scans can help physicians monitor how much radiation their patients receive, according to findings presented here at the American Roentgen Ray Society 2010 Annual Meeting.

CT exposes patients to significantly more radiation than traditional x-rays, George Shih, MD, assistant professor of radiology at Weill Cornell Medical College in New York City, and lead author of the study, told Medscape Radiology. Currently, CT scans account for more than 50% of the radiation patients receive in the healthcare setting.

Dr. Shih cited a controversial 2007 paper in which the authors, extrapolating on data from people exposed to radiation from the atomic bombs dropped on Hiroshima and Nagasaki during World War II, stated that CT scans might be responsible for many cases of cancer in the United States (N Engl J Med. 2007;357:2277-2284).

More research is needed to confirm that claim, Dr. Shih cautioned. Still, there are "smarter ways of tracking how much radiation patients receive, but healthcare moves slowly. We decided that patient safety shouldn't wait that long."

The new system extracts radiation dose information from conventional CT scans and puts it into a more user-friendly format, which allows clinicians to determine the cumulative amount of radiation administered to their patients over time, said Dr. Shih. The purpose of the system, called Valkyrie, is to put the information into digital form and "to eventually perform automated quality control, promote radiation safety awareness, and provide a longitudinal record of patient healthcare-related radiation exposure," he explained.

Currently, dose information is automatically "burned" into the image, "like taking a picture of a sign," said Dr. Shih. Valkyrie, which he and his colleagues developed in collaboration with radiation physicists at Columbia University, extracts dose information embedded in the images using distinct characteristics that can be reliably detected by established algorithms, such as horizontal projection. It is a modular and "manufacturer-independent" system, so "it works pretty much in any healthcare infrastructure. We did not use proprietary software from any manufacturer," Dr. Shih explained.

To test the system, Dr. Shih and his coauthors had it analyze radiation dose information from 518 randomly selected dose reports. Valkyrie processed them all accurately. Although the system is still in the developmental stage, it is now used around the clock at Cornell. It is still 100% accurate in ongoing random tests of several thousand images.

Dr. Shih and his colleagues now are trying to make Valkyrie more precise by correcting for patient size. Usually, CT radiation dose is calculated in a one-size-fits-all fashion, using acrylic 32-cm "phantoms" to measure how much radiation the patient actually gets. But these phantoms are used for all adults, whether they weigh 100 pounds or 400 pounds, and "the actual amount of radiation those patients receive is very different," Dr. Shih noted.

Valkyrie has been programmed with a range of correction factors gathered from studies using phantoms varying in size from 6 to 32 cm, and it is now being improved so that ultimately, it will be able to calculate an individualized dose of radiation based on the patient's age, sex, and size.

"I think this work is extremely commendable. The one thing I would emphasize is that this is truly an estimated dose; it's not a real dose. No one has measured how much radiation the patients' liver or pancreas or kidneys actually get," said E. Stephen Amis, MD, chair of the Department of Radiology at Albert Einstein College of Medicine of Yeshiva University in New York City.

Dr. Amis, who was not involved in this research, also warned that it might be unrealistic to expect patients to carry a card with their cumulative radiation information on them at all times, or to think that every institution would have a system like Valkyrie available. "But I think this is really a great start, and I commend them for it."

Dr. Shih told Medscape Radiology that he plans to share the system with other institutions in the hopes of eventually building a national database that contains every patient's radiation history, as has been recommended by the American College of Radiology. "We hope other people will want to use it. Our first priority is patient safety."

Dr. Shih and Dr. Amis have disclosed no relevant financial relationships.

American Roentgen Ray Society (ARRS) 2010 Annual Meeting: Abstract 002. Presented May 3, 2010.

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