医学影像产生的辐射逐渐增大

Concern about overexposure to radiation due to excessive use of medical imaging has come to the fore¹ in recent years. Now, a study led by researchers at the University of California, San Francisco (UCSF) and Group Health Research Institute, shows that medical imaging is increasing even in health maintenance organization systems (HMOs), which don't have a financial incentive² to conduct them. Published this week in the Journal of the American Medical Association (JAMA), the study is the first to look at how radiation exposure has grown within large integrated health care systems. Earlier studies have shown an increase in the public's exposure to radiation because of medical imaging at "fee-for-service" hospitals and clinics, which make more money the more scans they do.

Some experts had speculated that radiation exposures would be different in the closed, integrated health care system world, where the same financial incentives³ do not exist. All the clinical operations fall under the same umbrella as the insurance and payment operations in these systems, and if anything, more medical scans would seem to be financially discouraged.

"You would have imagined that the rate of increase would be lower," said Rebecca Smith-Bindman, MD, a professor of radiology and biomedical imaging at UCSF. "Our results showed very similar growth in imaging within these integrated settings as has been shown outside of these settings."

According to Smith-Bindman, UCSF has focused a great deal of attention to ensure its patients receive the lowest doses possible for medical diagnosis⁴, including implementing⁵ new software that reduces dose, acquiring new lower-dose equipment, and reducing the use of certain high-dose procedures. These efforts have achieved significant dose reductions in the last few years, she said. For example, CT doses have gone down 30 percent to 40 percent over the last two years.

Smith-Bindman and colleagues across the University of California medical centers are also organizing a very large meeting in February 2013 to help educate the public, referring physicians and technologists, physicists⁶ and radiologists across the country on strategies for assessing and then lowering the radiation doses to which patients are exposed.

The latest study showed a dramatic increase in imaging rates and a doubling in the proportion of patients who incurred⁷ high and very high radiation exposures from 1996 to 2010, paralleling the rise in the fee-for-service world. The number of ultrasoundexaminations doubled, the number of CTs tripled, and the number of MRIs quadrupled. The analysis also showed enormous variation from system to system, with some types of imaging being done 5 to 10 times more often in one system compared to the others.

This is significant, Smith-Bindman said, because on the national level, a lot of hope for countering the rise in imaging rates and radiation exposure has been pegged⁸ to removing financial incentives by changing the fee structure of radiological exams and capping reimbursements⁹（退还，偿还） , as Medicare has already done.

The new study suggests it may not be so simple. The same drivers of imaging are important in all health care systems.