December 15, 2009

ACR Statement on Recent Studies Regarding CT Scans and Increased Cancer Risk

Medical imaging exams have been directly linked to greater life expectancy, declines in cancer mortality rates, and are generally less expensive than the invasive procedures that they replace. However, widespread use has resulted in increased radiation exposure for Americans.

The American College of Radiology (ACR) advises that no imaging exam should be performed unless there is a clear medical benefit that outweighs any associated risk. The ACR supports the ‘as low as reasonably achievable’ (ALARA) concept which urges providers to use the minimum level of radiation needed in imaging exams to achieve the necessary results. ACR is a founding participant in the Image Gently™ campaign for dose reduction in pediatric imaging and has launched an adult radiation dose reduction effort.

While imaging growth is in line with, or below that of other physician services, appropriate use of imaging can be addressed by wider adoption of ACR Appropriateness Criteria®, which help physicians prescribe the most appropriate imaging exam for more than 200 clinical conditions (particularly when an imaging exam that does not use radiation may be more appropriate for a given condition), and point of entry physician ordering systems based on this tool, such as the 2010 Medicare pilot project mandated by the Medicare Improvements for Patients and Providers Act of 2008. Accreditation of imaging facilities, to be mandated under Medicare, effective Jan. 1, 2012, can cut down on radiation dose received from duplicative scans and help to ensure that patients receive appropriate dose per scan.

Specific to the Archives of Internal Medicine studies:

There is significant debate and uncertainly regarding the cancer risks associated with the X-rays used for diagnostic imaging. However, some studies of large populations exposed to radiation have demonstrated slight increases in cancer risk even at low levels of radiation exposure, particularly in children. To be safe, we should act as if low doses of radiation may potentially cause harm. This has governed the ACR’s efforts in dose reduction.

However, the authors do not acknowledge this uncertainty and neglect to put the significant benefits of this technology in perspective with the risks. Furthermore, the conclusions of the Archives’ studies rely largely on data which equates radiation exposure and effects experienced by atomic bomb survivors in Japan to present day patients who receive computed tomography (CT) scans. Most CT is performed in controlled settings and results in limited radiation exposure to a small portion of the body. Atomic bomb survivors experienced instantaneous exposure to the whole body. CT exams expose patients solely to X-rays. 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 and should be considered.

Also, the articles ─ after excluding patients with cancer or within five years of the end of life ─ assumed that those undergoing CT scanning have the same life expectancy as the general population. This is not accurate, so the estimates are undoubtedly high. Moreover, 25 percent of people in the United States die of cancer with a life time incidence of 40 percent, about 1.5 million new cancers per year. The 29,000 figure, if even close to accurate, is overall a very small risk versus the immediate, proven life saving benefits of CT.

The ACR urges patients and providers to visit the Radiology Safety section of the ACR website as well as the Radiation Safety section of, the patient information site co-managed by the ACR and the Radiological Society of North America (RSNA), and the Image Gently™ site for more information regarding radiation exposure from medical imaging exams.

Patients should also keep a record of their X-ray history and before undergoing a scan, should ask their physician:

  • Why do I need this exam?
  • How will having this exam improve my health care?
  • Are there alternatives that do not use radiation which are equally as good?
  • Is this facility ACR-accredited?
  • Is my child receiving a “kid-size” radiation dose (for pediatric exams)?  

ACR accreditation ensures that:

  1. The physician interpreting scans has met stringent education and training standards
  2. The technologists operating the equipment are certified by the appropriate body
  3. The imaging equipment is surveyed regularly by a medical physicist to make sure that is functioning properly and is taking optimal images.  

Imaging Growth:

The March 2009 Medicare Payment Advisory Commission (MedPAC) report to Congress [page 99 ─ lower left] states that Medicare imaging utilization growth for 2006, 2007 was only 2 percent nationally ─ at or below the growth rate of other major physician services. According to Moran Company report, MRI volume actually went down in 2008.

Helpful Resources:

ACR Accredited Facility Search

ACR Appropriateness Criteria
ACR Appropriateness Criteria help physicians prescribe the most appropriate imaging exam for more than 200 clinical conditions (particularly when an imaging exam that does not use radiation may be more appropriate for a given condition).

Radiation Exposure Estimates from Common Imaging Procedures

Radiology Safety on

ACR Statement on Whole Body CT Scans