Use of Advanced Diagnostic Imaging Increasing

Joe Barber Jr PhD

June 13, 2012

June 13, 2012 — A retrospective analysis revealed that the use of advanced diagnostic imaging among members of integrated healthcare systems increased substantially from 1996 to 2010. For example, the number of computed tomography (CT) examinations nearly tripled during that time, and the per capita radiation exposure from CT quadrupled.

Rebecca Smith-Bindman, MD, from the University of California San Francisco, and colleagues published their findings in the June 13 issue of JAMA.

Dr. Smith-Birdman noted that the researchers wanted to clarify the use of imaging in a controlled setting. "While we know that within 'fee for service' models of care, imaging has gone up a lot in the last two decades, little is known of the patterns of imaging over time and cumulative doses of radiation that patients receive within the context of integrated health care systems," Dr. Smith-Birdman told Medscape Medical News by email. "We wanted to study patients in HMOs [health maintenance organizations] as they provided a group of patients where we would know all of the tests they underwent would be in the same system."

The authors reviewed the electronic records of 6 large integrated healthcare systems that participate in the HMO Research Network to determine the use of imaging modalities, excluding procedures done in conjunction with cancer treatment, and assess the delivered radiation dose. The authors excluded the data for members who purchased fee-for-service plans and those for patients who were treated at healthcare plan facilities without being enrolled in the HMO.

Imaging Use Over Time

The number of CT examinations tripled from 1996 to 2010 (52/1000 enrollees vs 149/1000 enrollees), resulting in an annual increase of 7.8% (95% confidence interval [CI], 5.8% - 9.8%), although this increase appeared to flatten after 2007. Similarly, the use of magnetic resonance imaging quadrupled over the 15-year study period (17/1000 enrollees in 1996 to 65/1000 enrollees in 2010), resulting in an annual increase of 10% (95% CI, 3.3% - 16.5%).

Moreover, the use of ultrasonography increased by approximately 2-fold during the study period (134/1000 enrollees vs. 230/1000 enrollees), resulting in an annual growth of 3.9% (95% CI, 3.0% - 4.9%).

On the other hand, the use of nuclear medicine decreased by 3% annually (95% CI, 7.7% decrease to 1.3% increase) during the study period (32/1000 enrollees vs 21/1000 enrollees), although use of position emission tomography increased by 57% annually after 2004 (0.24/1000 enrollees vs 3.6/1000 enrollees).

Meanwhile, the use of radiography (1.2% annual increase) and the use of angiography/fluoroscopy (1.3% annual decrease) were both relatively stable during the study period.

For all imaging modalities, the rate of use tended to increase with increasing patient age.

Radiation Exposure Over Time

The average effective dose of radiation via medical imaging increased by 3.2% annually (95% CI, 3.1% - 3.3%) from 4.8 mSv in 1996 to 7.8 mSv in 2010. Similarly, the proportion of patients exposed to high (20 to 50 mSv) or very high (>50 mSv) doses of radiation approximately doubled during the study period to 2.5% and 1.4%, respectively.

In line with the usage findings, the annual per capita radiation dose delivered by CT increased by 4-fold from 0.38 mSv in 1996 to 1.58 mSv in 2010. The amount of radiation delivered by angiography/fluoroscopy decreased from 0.52 mSv in 1996 to 0.34 mSv in 2010.

The proportion of patients exposed to high and very high doses of radiation increased with increasing age. By 2010, 11% and 7.3% of enrollees aged 65 years or older were exposed to high and very high radiation doses, respectively, compared with 1.3% and 0.4%, respectively, for enrollees aged 0 to 14 years.

Comparative Effectiveness Research Needed

Dr. Smith-Bindman argues for a more prudent use of imaging. "We need to change the way we practice as physicians," Dr. Smith-Bindman told Medscape Medical News. "We need to fund comparative effectiveness research that helps us understand when imaging is helpful and when it may potentially lead to more harm than good."

In a related commentary, George T. O'Connor, MD, MS, from the Boston University School of Medicine in Boston, Massachusetts, and Hiroto Hatabu, MD, PhD, from Harvard Medical School in Boston, noted that advanced CT modalities have reduced the exposure of patients to ionizing radiation and suggested that further improvements can be made. "In the near future, it may be possible to further decrease radiation exposure by an order of magnitude by combining modern scintillation materials for x-ray detectors, iterative physical model-based reconstruction algorithms, and more personalized image acquisition protocols," Dr. O'Connor and Dr. Hatabu write. "Diagnostic modalities without radiation exposure, such as magnetic resonance imaging and ultrasonography, may be able to be substituted for some CT scans."

Amy Berrington de González, from the National Cancer Institute in Bethesda, Maryland, questioned whether warning systems could alter the use of imaging modalities. "In some HMOs, they started using warning messages when a physician ordered an imaging procedure that involved ionizing radiation after concerns were raised about the increasing levels of use," Dr. Berrington de González told Medscape Medical News by email. "It would be worth investigating further whether these warnings may have impacted the levels of use."

Dr. Hatabu received research grant support from Toshiba Medical, Canon, and AZE. The remaining authors and commentators have disclosed no relevant financial relationships.

JAMA. 2012;307:2400-2409. Full text

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