When the New England Journal of Medicine reported last week on the dangers of increased use of computed tomography (CT), the news garnered front page coverage across the country.

However, in Chicago, at the annual Radiology Society of North America conference, held at the same time, the issue of growing CT scan use possibly leading to significant health problems was already well known. Original equipment manufacturers including GE, Toshiba, and Philips used the RSNA to debut possible solutions: Toshiba's Aquilion ONE; GE's futuristic Gemstone High-Definition CT Scanner along with existing systems, and Philips' Brilliance iCT scanner, technologies that limit radiation exposure.

The NEJM study by Columbia University Medical Center found that radiation doses to organs from a common CT study probably result in an increased risk of cancer particularly for children. CT scans may be to blame for up to 2% of cancers in the U.S. over the next few decades. The understanding is partly based on long-term observations of lifetime risk of radiation exposure among atom bomb survivors. While individual risk is low, an increased use of CT would impart a greater overall health risk to the population. The study contributes to the case being made that we use CT scanning too often.

While large-scale studies are needed, ECRI Institute had reported earlier this year in DOTmed News that CT scans may account for up to 6,000 U.S. cancers per year and CT use is on the rise. Alarmingly, clinicians and patients seem to lack a clear understanding of the risk.

CT scans are an X-ray-based tool providing three-dimensional views of a particular organ or tissue. Its ability to successfully diagnose injury, cancer and other health problems is undisputed.

David Brenner, PhD and Eric Hall, PhD, from the Center of Radiological Research at Columbia University, underscore in their NEJM presentation much of what the ECRI research also argued: potential carcinogenic efforts from CT scan use "may be underestimated or overlooked." Adding to everyone's concern are data noting a marked increase in the average personal radiation exposure in the United States, growing from an estimated three million CT scans a year in 1980 to more than 62 million currently.

CT scans result in far larger doses than conventional plain-film X-ray exposure. Early belief held that all radiological examinations were essentially harmless because of the small amounts of radiation involved. But Drs. Brenner and Hall note that sixty years of CT scans study, specifically of Japanese atomic bomb survivors two miles away from the explosions, reveal that radiation doses for them were quite similar to those from a CT scan, representing a potential public health problem. "In a few decades," the authors say, "about 1.5 to 2 percent of all cancers in the United States may be due to radiation from CT scans being done now."

Worst still, a majority of radiologists and emergency-room physicians may not appreciate that CT scans are likely to increase the lifetime risk of cancer.

The researchers suggest three strategies for proactively addressing the potential increased radiation risk associated with CT scans:

1. Reduce the CT-related radiation dose in individual patients.
2. Replace CT use, when appropriate with other options that have no radiation risk, such as ultra sound or magnetic resonance imaging (MRI)
3. Decrease the total number of CT scans prescribed.

Technology to the Rescue?

The significant strength in the Toshiba American Medical Systems 320-Detector CT, Aquilion ONE, as the name implies, is its one-dose feature, reducing diagnosis time for life-threatening diseases such as stroke and heart disease from days and hours to mere minutes.

Called the world's first dynamic volume computed system, the Aquilion ONE allows physicians to see not only a three-dimensional depiction of an organ, but also the organ's dynamic blood flow and function-such as a heart or brain---in one ultra high single rotation.

The two-metric ton (4,400 pound) device can measure subtle changes in blood flow or minute blockages forming in blood vessels no bigger than a toothpick. Ten years in development, and priced between $2 and $3 million, the scanner has been installed and is in operation at The Johns Hopkins Hospital and Brigham and Women's Hospital.

GE Technologies

Also at the RSNA, GE's new Gemstone Detector showcased its advanced High-Definition CT technology. Believing that merely adding more slices or X-ray sources does nothing to improve image clarity, GE engineers and scientists are working to completely revamp the entire CT imaging chain--from X-ray tube through the detector and data acquisition."

GE's new scintillator material is 98 percent garnet and 2 percent rare-earths. GE based its new technology on the brilliant garnet gemstone because of its unique optical properties. When modified and enhanced, the "GE Gemstone CT" detector provides significant improvement in X-ray conversion speed and other properties required to support step-function improvements in special resolution.

Still under development, GE has not announced its cost or market availability.

In the here and now, GE offers many technologies to reduce patient dose with equal or improved image quality. GE's VCT-XT is the first-ever computed tomography (CT) scanner to quickly capture high quality, accurate images while reducing a patient's exposure to radiation by 83 percent. This new technology is capable of capturing images of the heart and coronary arteries in as few as five
heartbeats, and X-rays are turned on only during the required cardiac phase - they're turned off completely at all other times. Additionally, the VCT-XT is able to take both brain and cardiac images in one exam, and can scan the entire body in less than 10 seconds, or an organ in a second.

GE's LightSpeed VCT XT features VolumeShuttle and SnapShot Pulse--two diagnostic cardiac and neuro perfusion exams. SnapShot Pulse technology (prospectively gated diagnostic cardiac CT exam) has been proven by clinicians performing thousands of exams at sites around the world to reduce a patient's radiation exposure. GE's innovative VolumeShuttle technology delivers twice the anatomical coverage (80mm) with up to 24% less radiation exposure compared to a conventional 40mm cine perfusion protocol.

Philips Technology

Philips' Brilliance iCT scanner, a 256-slice CT, is also designed to reduce patients' exposure to X-rays. The scan is much quicker, as the machine's X-ray emitting gantry -- the giant ring-shaped part that surrounds the patient -- can rotate four times in a single second, which is 22 percent faster than current systems.

Ultimately, patients and providers will need to determine whether the benefits of early disease detection supported by medical imaging are worth the risk of radiation exposure. As OEMs come up with newer, better, and safer technologies, that equation may swing in favor of widespread medical imaging.

For More Information

Read the NEJM findings here:
http://content.nejm.org/cgi/content/full/357/22/2277

Read the RSNA statement here:
http://www.rsna.org/media/pressreleases/pr_target.cfm?ID=348

Read a statement from the Medical Imaging & Technology Alliance (MITA) at www.dotmed.com/news/story/5165.

Read about ECRI Institute at www.dotmed.com/news/story/3566.