Radiation Exposure Calculated in Study of Increased Use of Diagnostic Imaging

June 13, 2012—In the Journal of the American Medical Association (JAMA), Rebecca Smith-Bindman, MD, et al published findings from a study concluding that there was a large increase in the rate of advanced diagnostic imaging and associated radiation exposure between 1996 and 2010 within large integrated health care systems (2012;307:2400–2409).

As summarized in JAMA, the background of the study is that use of diagnostic imaging has increased significantly within fee-for-service models of care but that little is known about patterns of imaging among members of integrated health care systems. The investigators conducted this study to estimate trends in imaging utilization and associated radiation exposure among members of integrated health care systems.

The study involved a retrospective analysis of electronic records of members of six large integrated health systems from different regions of the United States. A review of these medical records, which included 1 to 2 million member-patients each year from 1996 to 2010, allowed for direct estimation of radiation exposure from selected tests. The main outcome measure was advanced diagnostic imaging rates and cumulative annual radiation exposure from medical imaging.

The investigators reported in JAMA that during the 15-year study period, enrollees underwent a total of 30.9 million imaging examinations (25.8 million person-years), reflecting 1.18 tests (95% confidence interval [CI], 1.17–1.19) per person per year, of which 35% were for advanced diagnostic imaging (computed tomography [CT], magnetic resonance imaging [MRI], nuclear medicine, and ultrasound).

From 1996 to 2010, the use of advanced diagnostic imaging increased as follows: CT examinations increased from 52 per 1,000 enrollees in 1996 to 149 per 1,000 in 2010 (7.8% annually; 95% CI, 5.8%–9.8%); MRI use increased from 17 to 65 per 1,000 enrollees (10% annually; 95% CI, 3.3%–16.5%); and ultrasound use increased from 134 to 230 per 1,000 enrollees (3.9% annually; 95% CI, 3%–4.9%).

The investigators found that although nuclear medicine use decreased from 32 to 21 per 1,000 enrollees, (3% annual decline; 95% CI, 7.7% decline to 1.3% increase), PET imaging rates increased after 2004 from 0.24 to 3.6 per 1,000 enrollees, a 57% annual growth.

The study further showed that although imaging use increased within all health systems, the adoption of different modalities for anatomic area assessment varied. Increased use of CT between 1996 and 2010 resulted in increased radiation exposure for enrollees, with a doubling in the mean per capita effective dose (1.2 mSv vs 2.3 mSv) and the proportion of enrollees who received high (> 20–50 mSv) exposure (1.2% vs 2.5%) and very high (> 50 mSv) annual radiation exposure (0.6% vs 1.4%). By 2010, 6.8% of enrollees who underwent imaging received high annual radiation exposure (> 20–50 mSv), and 3.9% received very high annual exposure (> 50 mSv), reported the investigators in JAMA.

Responding to this study, the Society of Nuclear Medicine (SNM) issued a position statement on dose optimization for nuclear medicine and molecular imaging procedures. SNM asserted when nuclear medicine and molecular imaging procedures are performed correctly on appropriate patients, the benefits of the procedure very far outweigh the potential risks. To ensure the appropriate use of these procedures, all nuclear medicine facilities should have comprehensive quality control measures in place, their nuclear medicine physicians should have up-to-date training, and their technologists should be appropriately trained and certified.

In its press release, SNM advised that although the use of low levels of radiation in these procedures entails some possible risk, these procedures are highly effective, safe, and painless diagnostic tools that present physicians with a detailed view of what's going on inside an individual's body at the cellular level.

SNM stated its position that all nuclear medicine and molecular imaging procedures should be optimized so that the patient receives the smallest possible amount of radiopharmaceutical that will provide the appropriate diagnostic information, that the right test with the right dose should be given to the right patient at the right time, and that the procedure that provides the most useful clinical information is the one that should be performed. Furthermore, if an appropriate procedure—one that can provide the physician with clinical information essential to the patient's treatment—is not performed when necessary due to fear of radiation, it can be detrimental to the patient, noted SNM.