The Journal of the American Medical Association (JAMA) has published a report in its June 13, 2012 edition titled Use of Diagnostic Imaging Studies And Associated Radiation Exposure for Patients Enrolled in Large Integrated Health Systems, 1996-2010. JAMA. 2012;307(22):2400-2409 This study was a retrospective analysis of the EHR from members of six large integrated health systems from different regions of the United States. Between 1 million and 2 million member-patients were included each year from 1996-2010. This allowed direct estimation of advanced imaging radiation exposure. What were the results of the study? During the 15 year study, a total of 30.9 million imaging exams were performed, an average of 1.18 tests per person per year, 35% of which were advanced diagnostic imaging (computed tomography [CT], magnetic resonance imaging [MRI], nuclear medicine, and ultrasound). What was cumulative and annual percentage rise in these tests between 1996 and 2010? These numbers below are the reported increase in the number of scans per 1000 enrollees from 1996 to 2010 with the annual percentage increase in parentheses.
- CT: increased from 52 to 149 (7.8% annual increase)
- MRI: increased from 17 to 65 (10% annual increase)
- Ultrasound: increased from 134 to 230 (3.9% annual increase)
- Nuclear medicine: decreased from 32 to 21 (3% annual decline)
- PET scan: after 2004 increased from 0.24 to 3.6 (57% annual increase)
The average radiation exposure for enrollees increased as well with the a doubling of the mean per capita effective dose increasing from (1.2 mSv vs 2.3 mSv). Enrollees who received high annual exposure (>20-50 mSv) doubled as well from 1.25% to 2.5% of enrollees. In addition, the percent of enrollees exposed to very high (>50 mSv) annual radiation exposure increased from 0.6% to 1.4%. The annual allowable government limitations for occupational exposure to radiation is 50 mSv. The levels of radiation exposure are only getting worse as radiation exposure in scans continue to rise with increasing sensitivity of the technology. By 2010, 6.8% of enrollees who underwent imaging received high annual radiation exposure and 3.9% received very high annual radiation exposure.
The FDA has previously reported on their concerns about CT scan radiation exposure. Why? There is concern up to 2% of cancers may be related to radiation exposure to CT scans and nuclear medicine scans with some of the greatest concern coming from younger females who undergo cardiac calcium scoring scans. In addition, some reports indicate CT contrast causes thyroid damage. Of course, when physicians weigh the short term risk and benefit of ordering or not ordering advanced imaging, the acute care needs will usually trump the long term risks and growing costs. Physicians are not very good about practicing with the future in mind. Their patient in front of them, there and now, is the concern at hand. Rarely will a physician avoid advanced imaging based on future cancer concerns.
One must simply consider the approximate 2% risk of devastating intracranial hemorrhage when administering tPA for pulmonary embolism and stroke. Many physicians fear this drug and the potential legal consequences of bad outcomes. But rarely will a physician avoid doing a CT scan to rule out a pulmonary embolism or a stroke, even though the risk of future devastating cancer is 2%. Physicians treat patients in front of them at that moment in time. Public health doctors concern themselves with future population risks.
Since we have compelling data that suggests advanced diagnostic imaging increases future cancer risks, I'm surprised at the lack of class action lawsuits against General Electric and the other big manufacturers of CT scanners to get them removed from the market. A few hundred people die from bleeding complications related to Pradaxa (just as hundreds of thousands bleed every year from warfarin) but not a word from this country's lawyers about eliminating radiation inducing imaging to save millions of Americans from future cancer.