BB&T

The value of computed tomography (CT) scanning to diagnose illness or injury is difficult to dispute. Just as difficult to dispute are the risks associated with this technology. CT scans expose patients to higher doses of radiation compared to plain-film X-ray, and CT scanning has been associated with producing cancer, later downstream, in a small percentage of those scanned. Thus, imaging companies continue to introduce new technology that reduces patients’ radiation exposure.

The most recent charge concerning the instances of cancer as the result of CT scanning radiation came in December, with research published in the New England Journal of Medicine that once again sparked the debate between researchers and experts from the imaging community over the benefits of CT vs. the associated cancer risks, and actual cancers, experienced downstream.

According to two researchers from the Center for Radiological Research at Columbia University Medical Center (New York), an estimated 62 million CT scans are given each year in the U.S. compared to 3 million in 1980. And for children, an estimated 4 million to 5 million CT scans are ordered each year. As a result of this marked increase in CT use, David Brenner, PhD, and Eric Hall, PhD, predict that in the coming decades as many as 2% of all cancers in the U.S. may be caused by radiation from CT scans being performed today. Children face the most danger, they say.

Brenner told Biomedical Business and Technology that this study is a continuation of his previous research, published in 2004 in the journal Radiology, that study resulting in issuing a warning concerning the link between CT scans and cancer. Brenner’s 2004 study estimated that a 45-year-old who gets one full-body CT scan would have a lifetime cancer death risk of about 0.08%, thus producing a cancer-related death in 1 in 1,200 people. But another 45-year-old who has annual full-body CT scans for 30 years would accrue a lifetime cancer mortality risk of about 1.9%, or about a 1-in-50 chance of dying of cancer, according to Brenner’s findings in the earlier study

A U.S. Government study, to be published this year, determined that the per-capita radiation dose from clinical imaging exams has risen by 600% between 1980 and 2006, with a major contributor being CT exams, those numbers increasing over 20 times during this period.

And the numbers have risen rapidly especially in the past three years, Brenner told BB&T. “The numbers of CT scans in this country have gone up as our understanding about the carcinogenic potential of radiation doses has improved,” Brenner said. In other words – the risks are better understood now, with renewed debate especially centering on scanning children and doing an increased amount of unnecessary scanning.

Lowering the dose

In response, the industry is bannering its efforts to develop new systems intended to expose patients to lower doses of CT radiation.

Imaging3 (Burbank, California), for example, said its newest product, the Dominion Volumetric Imaging Scanner, uses radiation doses between 100 to 1,000 times less than a standard CT scan. Yet, according to the company, the image is more accurate than standard CT scanners because the reading is three dimensional and constructed in real time. The Dominion production prototype, introduced in November at the Radiological Society of North America’s (RSNA; Oakbrook, Illinois) annual meeting in Chicago, is not yet FDA approved.

The system uses photo-fluoroscopy technology, one of the imaging industry’s responses to the growing concern about the amount of radiation exposure from CT, Dean Janes, CEO and chairman of Imaging3, told BB&T.

The Dominion uses an X-ray source and a flat panel CCD detector, which are perpendicular to each other. They scan at 360-degrees every two-10ths of a second to eight-10ths of a second. Using high-speed photo-fluoroscopy, images are taken throughout this scan in several angles inside an O-shaped device that works similar to a “C” arm. These images are then instantaneously placed into a 3D construct and updated every two-10ths of a second to eight-10ths of a second thereafter. The scanner is mobile, Janes said, and can be used throughout a hospital for CT diagnosis or guidance during a minimally invasive procedure.

Because imagery is so important in the medical field for guidance and diagnosis, Janes said he thinks a lot of radiologists simply don’t want to know about the radiation dosage. Radiation dosages are a trade-off, he said, for the valuable diagnostic information provided by a CT image.

Still, he said the industry is beginning to look at imaging from the perspective of the total accumulation of radiation, the amount of exposure a patient gets as a result of undergoing several imaging procedures.

Referring to devices such as the Dominion, he termed these “the new ‘green’ technology” – lower dosages but still producing highly accurate 3D images.

“That’s where the future is going to be,” Janes said. “The higher-power CT will still exist, but I think it will decline in usage — it has to.”

Last July another company, biospace med (Paris, France/Marietta, Georgia), reported filing a 510(k) application with the FDA seeking clearance to market its EOS ultra-low-dose 2D/3D orthopedic X-ray imager. The filing came on the heels of the company’s obtaining the CE mark for the system, as well as approval by the Health Canada Medical Device Bureau.

The EOS ultra-low dose 2D/3D is based upon a particle detector technology for which French physicist Georges Charpak received the Nobel Prize in Physics in 1992, biospace med said. This detector, which is designed to allow images to be obtained with a lower dose of radiation, is part of a system that is capable of very long-length digital imaging, permitting full-body, uninterrupted digital imaging with a single scan, according to the company.

With EOS, the patient stands in the imager and a vertical drive mechanism moves a “C” arm down the height of the patient, or any desired length. The “C” arm contains two separate imaging systems capable of simultaneously capturing both a frontal and side image.

The highly sensitive X-ray detector enables low-dose image capture, creating a “head to toe” image within roughly 20 seconds for an adult and about half as long for shorter pediatric patients. The fully digital system produces a front and side view of the patient, instantly available for viewing.

Unlike standard X-rays, there is no film, no need to adjust for distortion and no need to digitally stitch together multiple images, the company said.

EOS technology “offers a less expensive image at a much lower radiation dose, with new information being provided,” Richard diMonda, the company’s VP of strategic marketing, global, told BB&T.

The lower-dose of radiation is particularly important, diMonda said, among pediatric patients with spine deformities, such as scoliosis, who have to be imaged a few times a year.

Reducing scanning time

Toshiba America Medical Systems (TAMS; Tustin, California) also is paying attention to these concerns with its AquilionONE diagnostic imaging system. Unveiled during the RSNA meeting, TAMS says the system has the potential “to revolutionize” patient care by greatly reducing the time to diagnose life-threatening diseases such as heart disease and stroke, from days and hours to what company VP of marketing, John Zimmer, termed “mere minutes.”

Zimmer told BB&T that with the AquilionONE, physicians can see not only a 3D depiction of an organ, but also the organ’s dynamic blood flow and function. Unlike any other CT system, it can scan one organ — including the heart, brain and others — in just one rotation because it covers up to 16 cm of anatomy using 320 ultra-high resolution 0.5 mm detector elements. This reduces exam time, as well as radiation and contrast dose, dramatically increasing diagnostic confidence, Zimmer said.

A single organ or area of the body can be captured in one rotation, at one moment in time, eliminating the need to reconstruct slices from multiple points in time. Commercial release of the AquilionONE is expected this summer.

In October the Cleveland Clinic placed dual-source CT at No. 10 on its “Top Ten” medical innovations of 2008 list, noting that such scanners use two radiation sources and detectors, speeding medical imaging and exposing patients to less radiation.

Too many unnecessary scans

While CT scans save lives, researchers Brenner and Hall acknowledge, doctors often view CT scans as similar to other non-radiation imaging modalities – such as ultrasound or MRI. Thus, children are often scanned via CT technology for appendicitis, even though ultrasound is a perfectly good alternative for that, Brenner said. He also noted that MRI is a good alternative for diagnosing liver disease. And in the emergency room – where admittedly there is tremendous pressure to move patients through to treatment quickly, Brenner said that CT scans are ordered before a physician has done a thorough examination.

Children are at a greater risk, he said, because their developing bodies are more sensitive to the effects of radiation, and also because of the time between first scans and the overall life span in which cancer can develop. By contrast, someone exposed to radiation late in life is much less likely to ever be diagnosed with radiation-induced cancer, and much more likely to die of other causes.

Not unexpectedly, several radiological organizations responded to the new study with concern that it may cause patients to avoid getting life-saving medical imaging care.

Andrew Whitman, VP of the Medical Imaging & Technology Alliance (MITA; Washington), told BB&T that the industry is “well aware and sensitive to the fact that radiation is an issue.”

Bit he focused more on the benefits of this type of diagnostic scanning.

No more ‘exploratory’ surgery

“CT scans have allowed us to see things and detect diseases that we had not been able to do even five years ago,” Whitman said. “One of the reasons you don’t hear the term ‘exploratory surgery’ anymore is because of medical imaging and that is due in part to CT scans.”

Arl Van Moore, MD, chairman of the board of chancellors of the American College of Radiology (ACR; Reston, Virginia), echoed this view.

“Thirty years ago, instead of having a CT scan, you might have had abdominal surgery just to take a look-see — without any guarantee that they would find anything,” Moore told BB&T.

And while the ACR also acknowledges the problem of radiation, Moore said the organization especially is concerned that the comparisons the study makes between radiation exposure from CT and the exposure from the atomic bomb.

The recent JAMA studies and others use the radiation exposure and effects experienced by many survivors of the Atomic bomb attack on Hiroshima as the standard for measuring the effects of CT radiation. “These are really apples and oranges [comparisons],” Moore said.

Most CT exams, he said, are performed in a controlled setting, he said, which results in limited radiation exposure to a small portion of the body. In contrast, Atomic bomb survivors experienced instantaneous radiation exposure to the whole body. Also, CT exams expose patients solely to X-rays, whereas Atomic blast survivors were exposed to X-rays, particulate radiations, neutrons and other radioactive materials. The known biological effects are very different for these two scenarios, he and others have argued,

“Patients need accurate information on which to base their healthcare decisions,” Moore said. “They may be terribly confused and unduly distressed by some of the statements in this study.’

One point the researchers and radiological organizations agree on is that patients should keep a record of their X-ray history and, before undergoing a scan, should question their doctors as to the medical benefit gained from the scans and the alternatives that can be used.

Brenner also pointed out one possible way to reduce repeat CT scans from being performed on the same patient for the same problem as that patient gets moved from one hospital to another. That method would be to give patients a DVD of the CT scan to carry with them as they move through the healthcare system, avoid the need to undergo multiple scans for the same thing. This would be a “big plus” and would reduce unnecessary scans, he said, while acknowledging that many hospitals are not yet able to do this.

In another effort to reduce unnecessary scans, the Committee on Medical Aspects of Radiation in the Environment (COMARE; Didcot, UK), an organization that advises the UK government, warns against offering CT scanning on healthy individuals, a practice known as commercial CT scanning of asymptomatic people.

In a report released in December, COMARE recommends that people who display symptoms and, on their own, seek a commercial CT scan should be referred to their doctors before being scanned. Such services also should stop offering whole-body CT scans for people without symptoms, COMARE said. The committee also says commercial CT scans should not be used to assess spinal conditions body fat, and osteoporosis in healthy people.