Frequently Asked Questions

"Exposure to Low-Dose Ionizing Radiation from Medical Imaging Procedures"

New England Journal of Medicine (NEJM), Volume 361:849-857, August 27, 2009

Who authored the article?

The article’s lead author is Emory cardiologist Reza Fazel, MD, MSc. Additional co-authors are: Harlan M. Krumholz, MD, SM (Yale), Yongfei Wang, MS (Yale), Joseph S. Ross, MD (Mt. Sinai), Jersey Chen, MD, MPH (Yale), Henry H. Ting, MD, MBA (Mayo Clinic), Nilay D. Shah, PhD (Mayo Clinic), Khurram Nasir, MD (Boston Medical), MPH (Johns Hopkins), Andrew J. Einstein, MD, PhD (Columbia), and Brahmajee K. Nallamothu, MD, MPH (U. of Michigan).

What is the crux of the article?

The article reports on a research study that shows that several types of medical imaging procedures - such as x-rays, fluoroscopy, computed tomography (CT) scans, and nuclear medicine scans - expose patients to ionizing radiation, which over time can accumulate to substantial doses.

What is the importance of this research?

As an academic medical center with a distinct focus on research and improving clinical care, Emory is charged with finding the best ways to deliver healthcare in the United States. This article raises awareness of the cumulative doses of radiation that patients may have received and may eventually help us to develop better ways to take care of our patients.

This is a retrospective study that looked only at possible radiation doses. It did not attempt to see if there were adverse outcomes or assess the risk/benefit ratios of these procedures. It is an appropriate initial step in examining this important issue and as such, it will help us to develop future studies to guide us in the optimal use of diagnostic and therapeutic studies that employ ionizing radiation.

Do all imaging or radiology studies expose patients to radiation?

No. Ultrasound or sonography and magnetic resonance imaging (MRI) do NOT require the use of radiation.

Were all radiation doses studied of concern?

No. The majority of individuals who received radiation-related tests in the research study were exposed to low-dose x-rays, such as a chest x-ray. The procedure that contributed most to overall radiation exposure in the population was myocardial perfusion imaging, followed by abdominal, pelvic, and chest CT scans. Even still the average effective dose of radiation from all procedures was 2.4 mSv per year, which is equivalent to approximately 80 percent of the background exposure that the average adult receives in the US from natural sources.

What levels of radiation caused concern?

More concerning doses that accumulated over time were uncommon, with doses >20 mSv per year occurring in approximately 2 percent of enrollees and doses >50 mSv per year occurring in 0.2 percent of enrollees. While the risk to the individual patient from these doses are small, when applied to large populations of patients, these small risks can add up.

Are there any caveats to the study?


• The authors caution that they could not comment on clinical indications for the imaging procedures, their appropriateness, or whether other alternative studies were available.

• Effective doses used in the study are averages derived from the literature that are not specific to an individual. Thus, the actual absorbed dose may vary by sex, body mass and body composition.

• Radiation doses may vary by institution and the protocols in current use.

Is anything being done to reduce radiation exposure?


• According to the study authors, strategies to lower medical radiation exposure to the public are being addressed by national medical physics and radiology organizations, including the American Association of Physicists in Medicine and the American College of Radiology.

• Emory cardiologist and study author Dr. Reza Fazel notes, "Raising both physician and patient awareness on these issues as well as encouraging continued technological advances to lower radiation doses of procedures are the key approaches to lowering long-term risks in patients and for the population. But in the end, these risks need to be balanced against the immediate clinical need for these procedures, which are substantial in many cases."

Are there questions I should ask my imaging center about their protocols?

Yes. You should ask if the imaging center is accredited, the imaging personnel are credentialed, and the protocols used are weight-based and indication-based to ensure that they receive high-quality imaging.

At Emory, the majority of our imaging modalities are accredited by the American College of Radiology (ACR), Intersocietal Commission for the Accreditation of Computed Tomography Laboratories (ICACTL), Intersocietal Commission for the Accreditation of Nuclear Medicine Laboratories (ICANL), Intersocietal Commission for the Accreditation of Vascular Laboratories (ICAVL), or the American Institute of Ultrasound in Medicine (AIUM). Our Positron Emission Tomography (PET) Center was one of the first in North America to earn accreditation from ICANL. The Emory Breast Imaging Center earned the Breast Imaging Center of Excellence award from the ACR’s Commission on Quality and Safety and Commission on Breast Imaging, the highest designation available through the ACR. Additionally our radiologists implemented national benchmark standards for CT efficiency.

Where can I learn more?

To learn more about what is being done to improve radiation safety in medicine by reviewing the following web sites:

Image Gently: Alliance for Radiation Safety in Pediatric Imaging

National Council on Radiation Protection & Measurements

American College of Radiology White Paper on Radiation Dose in Medicine

Patient InformationFind more patient information about radiology at

Más información para pacientes sobre radiología.