Dramatic Increase Seen Nationwide in Advanced Imaging, Radiation Exposure

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In the past 15 years, the substantial increase in the use of diagnostic imaging tests in the fee-for-service setting has been paralleled by a similar trend in large integrated health care systems. According to a study in the June 13, 2012, issue of the Journal of the American Medical Association, the use of computed tomography (CT) has tripled, while magnetic resonance imaging (MRI) has nearly quadrupled. In tandem, the percentage of patients with very high annual radiation exposures from imaging appears to have increased.

Researchers led by Rebecca Smith-Bindman, MD, of the University of California, San Francisco (San Francisco, CA), examined trends in imaging utilization and radiation exposure among members of 6 large integrated health care systems from different regions of the United States. Approximately 1 to 2 million member-patients were included each year from1996 to 2010, resulting in data on 30.9 million imaging exams over the 15-year study period.

Of the 1.18 average imaging tests per person per year, 35% comprised advanced diagnostic imaging exams such as CT, MRI, nuclear medicine, or ultrasound.

Steady Increases in Most Imaging Rates Seen

Overall, use of advanced diagnostic imaging, including MRI, CT, and ultrasound increased, while nuclear medicine use decreased. Rates for positron emission tomography (PET) scans began to increase in the later years of the study (table 1).

Table 1. Imaging Trends: 1996-2010

Modalities

Change per 1,000 Enrollees

Annual Change

CT

52 to 149

7.8%

MRI

17 to 65

10%

Ultrasound

134 to 230

4%

Nuclear Medicine

32 to 31

-3%

PETa

0.24 to 3.6

57%

a From 2004 to 2010.

Among HMO enrollees 65 years and older, rates of imaging with CT and MRI increased an average of 10.2% and 14.5% annually between 1998 and 2005, and slowed to 4.2% and 6.5% annual growth, respectively, from 2005 to 2008. Although these trends were broadly similar to those observed among Medicare fee-for-service insured beneficiaries, the increases for HMO members seemed to be modestly lower.

Conversely, rates of use for radiography and angiography/fluoroscopy were relatively stable over time: Radiography increased 1.2% per year, and angiography/fluoroscopy decreased 1.3% per year.

As the number of these diagnostic imaging procedures increased, so did the average per capita radiation dose exposure for CT, rising from 1.2 mSv in 1996 to 2.3 mSv in 2010. In addition, the percentage of HMO enrollees who received high (> 20-50 mSV) or very high (> 50 mSv) radiation exposure during a given year approximately doubled over the study period. By 2010, 1.4% of participants received a very high dose—a sevenfold increase over the 0.2% of Medicare patients reported in a 2009 study (Fazel R. N Engl J Med. 2009;361:849-857).

Meanwhile, angiography/fluoroscopy, nuclear medicine, and radiographs showed a persistent decrease in exposure.

Exposure ‘Nontrivial’ but Difficult to Quantify

In an editorial accompanying the study, George T. O’Connor, MD, of the Boston University School of Medicine (Boston, MA), and Hiroto Hatabu, MD, PhD, of Brigham and Women’s Hospital (Boston, MA), say that while a “nontrivial” number of patients in the United States receive a high or very high annual exposure to ionizing radiation from imaging studies in a given year, “these data are not linked to clinical outcomes and do not reveal whether the radiation risks from these imaging studies are outweighed by the health benefits provided by the diagnostic information obtained.”

Additionally, they say the data also cannot address how much of testing is driven by defensive practice styles due to concerns about malpractice.

“[The data] do, however, suggest that clinicians need to consider—and discuss with their patients—radiation risks when ordering diagnostic tests, possibly taking into account the cumulative radiation exposure a patient has received in recent months or years,” they write.

In a telephone interview with TCTMD, Reza Fazel, MD, MSc, of Emory University (Atlanta, GA), lead author of the 2009 NEJM paper, agreed that retrospective analyses of medical records make it difficult to determine the appropriateness of any given imaging study and how much value it may have added to the care of the patient.

More Work Needed to Minimize Exposure, Optimize Tracking

“These [imaging] studies are becoming better and more useful from a diagnostic and treatment standpoint, but we do have to think about how we’re using them and make sure that we are optimizing their use,” he said.

Dr. Fazel said the methods used for estimating radiation exposure in the current study are “scientifically more accurate” than those used in his 2009 study, which he said may partly explain the sevenfold increase in the percentage of patients receiving annual doses above 50 mSv.

According to Dr. Fazel, there are 3 general strategies that can help ensure that procedures involving ionizing radiation are used wisely:

  • Educate clinicians who are ordering and performing the tests about benefits and potential risks of the study, including radiation exposure
  • Develop mechanisms to ensure that studies are used only when clinically justified and can provide information that could not be obtained in another manner
  • Make every effort to use the lowest level of radiation that will still provide an accurate study that can be interpreted confidently

In addition, he said greater efforts are being made to track radiation exposures, namely through participation in national registries such as the American College of Radiology’s Dose Index Registry, which gives individual clinicians and institutions feedback on how they fare compared with national benchmarks.

“I think in the next few years we will see more of these national registries and more emphasis on the importance of participation in them,” Dr. Fazel added.

 


Sources:
1. Smith-Bindman R, Miglioretti DL, Johnson E, et al. Use of diagnostic imaging studies and associated radiation exposure for patients enrolled in large integrated health care systems, 1996-2010. JAMA. 2012;307:2400-2409.

2. O’Connor GT, Hatabu H. Lung cancer screening, radiation, risks, benefits, and uncertainty. JAMA. 2012;307:2434-2435.

 

 

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Disclosures
  • The study was supported by the National Cancer Institute-funded Cancer Research Network Across Health Care Systems and grants from the National Institutes of Health.
  • Drs. Smith-Bindman, O’Connor, and Fazel report no relevant conflicts of interest.
  • Dr. Hatabu reports receiving research grant support from AZE, Canon, and Toshiba Medical.

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