Diagnostics & Imaging Week

The value of CT scanning to diagnose injury or illness is undisputed, as is the fact that there are risks associated with this technology because it exposes patients to higher doses of radiation compared with plain-film X-ray.

But researchers and experts from the imaging community are bumping heads when it comes to weighing the benefits of CT with the associated risk of cancer, experienced downstream, caused by radiation exposure. And a new study published last week in the New England Journal of Medicine further fuels that debate.

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 three million in 1980. 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, researchers David Brenner, PhD, and Eric Hall, PhD, offer the prediction that in the coming decades as many as 2% of all cancers in the U.S. may be caused by radiation from CT scans performed now. Children face the most danger, they say.

Brenner told Diagnostics & Imaging Week that this study is a continuation of his previous research published in Radiology in 2004, issuing a warning concerning the link between CT scans and cancer.

What has changed in the past three years, he said, are the numbers.

“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. “Our understanding of the risks are better.”

While CT scans save lives, the researchers acknowledge, doctors often view CT scans in the same light as other radiologic procedures – such as ultrasound or MRI – even though radiation doses are typically much higher with CT than those procedures.

A classic example is that children are most often scanned for appendicitis, even though ultrasound is a perfectly good alternative for that, Brenner said. He also noted that MRI is a good alternative to diagnosing liver disease.

But often in the emergency room – where admittedly there is tremendous pressure to move patients through quickly, Brenner said – CT scans are ordered before a physician has even examined the patient.

Children are at a greater risk, he said, not only because they are inherently more sensitive to radiation effects but also because of the long lag between radiation exposure and a potential cancer. So, for instance, a 75-year-old who is exposed to radiation will most likely die of other causes before ever being diagnosed with radiation-induced cancer. That’s not the case with a young person who, hopefully, has many years left to live, Brenner said.

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 D&IW that the industry continues to introduce new technology that reduces patients’ radiation exposure and that “we are well aware and sensitive to the fact that radiation is an issue.”

Still, there is a lot to be said for CT scanning, he noted.

“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 sentiment.

“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 MDD.

And while the ACR also acknowledges the problem of radiaiton, Moore said the organization especially is concerned about the comparisons the study makes between radiation exposure from CT and the exposure from the atomic bomb. The study equates radiation exposure and effects experienced by many atomic bomb survivors in Japan to present day patients who receive CT scans.

“These are really apples and oranges,” Moore said.

Most CT exams are performed in a controlled setting, he said, which results in limited radiation exposure to a small portion of the body. Atomic bomb survivors experienced instantaneous radiation exposure to the whole body, he said. 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.

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

One point the researchers and radiological organizations seem to 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 what alternatives exist.

Brenner also pointed out a possible way to reduce repeat CT scans from being performed on the same patient for the same problem as that patient gets moved from hospital to hospital. He told D&IW that one solution would be to have the patient keep a DVD with the CT scan to carry with them as they move through the healthcare system, to prevent the need to undergo multiple scans for the same thing.

Hospitals may not be set up for that yet, he said, but it would certainly be a “big plus” and would reduce a lot of unnecessary scans.

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