Americans are now exposed to seven times more radiation each year from medical imaging exams than in 1980, according to a recent National Council on Radiation Protection and Measurement (NCRP; Bethesda, Maryland) report. In 2006, medical exposure constituted nearly half of the total radiation exposure of the U.S. population from all sources, according to the report.

Kenneth Kase, MD, senior VP of NCRP and chairman of the scientific committee that produced the report said the increase was due mostly to the higher use of CT and nuclear medicine. "These two imaging modalities alone contributed 36% of the total radiation exposure and 75% of the medical radiation exposure of the U.S. population," Kase said. The number of CT scans and nuclear medicine procedures performed in the U.S. during 2006 was estimated to be 67 million and 18 million, respectively.

John Patti, MD, vice-chair of the board of chancellors of the American College of Radiology (ACR; Reston, Virginia), said one should be careful interpreting the study results. He told Medical Device Daily that although the NCRP report estimates the total radiation dose to the total population, the individual dose to individual patients has actually gone down.

"The physicians who monitor these imaging machines have taken great care to control the individual patient's radiation dose," Patti said.

The NCRP Report No. 160, Ionizing Radiation Exposure of the Population of the United States, provides a complete review of all radiation exposures for 2006, according to the NCRP.

Background radiation, which in 2006 contributed fully half of the total exposure, comes from natural radiation in soil and rocks, radon gas which seeps into homes and other buildings, plus radiation from space and radiation sources that are found naturally within the human body.

Other small contributors of exposure to the U.S. population included consumer products and activities, industrial and research uses and occupational tasks.

The NCRP said it is working with some of its partners such as the ACR, the World Health Organization (Geneva, Switzerland) and others to address radiation exposure resulting from the significant growth in medical imaging and to ensure that referrals for procedures like CT and nuclear medicine are based on objective, medically relevant criteria.

In a joint statement from the ACR, the Society for Pediatric Radiology (SPR), the Society of Breast Imaging (SBI), and the Society of Computed Body Tomography and Magnetic Resonance (SCBT-MR; all Reston, Virginia), urged Americans to understand why the increase occurred, consider the report's information in its "proper context," and "support appropriate actions to help lower the radiation dose experienced each year from these exams."

"It is essential that this report not be interpreted solely as an increase in risk to the U.S. population without also carefully considering the tremendous and undeniable benefits of medical imaging," said James Thrall, MD, chair of the ACR board of chancellors. "Patients must make these risk/benefit decisions regarding their imaging care based on all the facts available and in consultation with their doctors."

SCBT-MR President Sanjay Saini, MD, said, "Medical imaging has revolutionized medicine and is undoubtedly saving and extending lives everyday. It is vitally important that patients do not put off needed imaging care based on this report which neither quantifies the associated health risks nor specifies the radiation protection actions that should be taken."

But experts do have concerns about overutilization of these exams.

At a recent international conference David Schauer, executive director of the NCRP, cited self-referral, the process by which nonradiologist providers buy imaging equipment and refer patients to these in-office scanners as a primary, preventable driver of this dramatic increase in radiation exposure. Non-radiologist providers often lack even basic radiation safety training and may not be aware of potential repercussions to patients of ordering and often administering high volumes of scans, according to the ACR, SBI, and SCBT-MR statement.

Government Accountability Office reports as well as peer-reviewed studies published in the Journal of the American Medical Association and elsewhere have shown that when physicians refer patients to facilities in which they have a financial interest, imaging utilization is significantly increased, these organizations note.

From 1998-2005, in the Medicare system, the number of self-referred, in-office CT, MRI, and nuclear medicine scans performed grew at triple the rate of the same exams performed in all settings. Private insurance studies indicate that as much as half of this self-referred imaging is unnecessary; in many instances needlessly exposing patients to radiation. Provider fear of litigation, advancing technology, and patient demand may have also contributed to this increase in exposure, the groups speculate.

"It's a large issue and it's an issue that's growing in magnitude," Patti told MDD.

He added that, "We don't know to what extent it is [financially motivated]," but said it is safe to assume it is to some extent because "why else would the rate be so high" compared to the volume of scans in other settings.

While that is a factor of increased use of medical imaging exams, Patti says it is certainly not the only factor.

"Clearly medicine and healthcare is advancing to the point where we're able to diagnose more quickly, more accurately, at more cost effectiveness," Patti said. For example, he said, prior to the use of advanced medical imaging systems, a patient who shows up to the emergency room suspected of appendicitis might be admitted to the hospital for surgery, have the surgery turn out negative for appendicitis, then have to recoup from surgery and the healthcare system incurs tremendous cost. Today, however, that patient would receive a CT scan in the ER and about an hour to an hour and a half later have the diagnoses.

"There are some good, very valid reasons for this increase [in the use of medical imaging]."

And then there are some not-so-valid reasons, he acknowledged, such as those physicians who refer patients to receive imaging scans based more out of a financial interest than on medically relevant criteria.

Patti said the ACR is engaged in a process of widespread education about the issue, addressing the principals of radiation safety and appropriate use of imaging, which, when used properly can improve patient care and help cut medical costs.

The ACR said it recently published the ACR White Paper on Radiation Dose in Medicine, a "far-reaching and extensive set of 33 recommendations designed to counteract medical and societal trends which have contributed to any increased radiation dose that Americans may experience as this beneficial technology advances." To date, the organization said 27 of the 33 recommendations have been completed or are in progress.

"I think that the most important thing that a patient or person in the general population can take from this report is that they should not be afraid, they should not delay having an appropriate imaging exam performed if that's what is necessary for their healthcare," Patti said. "When a report like this comes out, particularly one that's as complex as this in the way the statistics were generated, [it tends to generate fear] that there may be some danger here, well there really isn't."

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