"In other words, orthopedic surgeons were able to mitigate the drop in patients by increasing the volume," Rao said.

Of course, some perspective is necessary. In absolute numbers radiologists see many more people than orthopedists, even though orthopedists have been seeing more people relatively speaking. In 2010, Medicare office-based MRI services by radiologists stood at 1.4 million, down from a high of 1.6 million in 2006 (pre-DRA), but still almost double the 2000 rates of 800,000. Orthopedic surgeons, however, had 200,000 exams in 2010, up from the 2000 rates of 50,000.

Not only the DRA

But it's not only the DRA that's giving imaging the squeeze. Rao and her colleagues found hospital inpatient imaging rates, not affected by the act, also shrank somewhat after 2008.

Using the same database, Rao and her colleagues looked to see what happened in hospitals. To do this, they calculated the Medicare inpatient imaging RVUs per 1,000 beneficiaries, which the authors said was a good proxy for work intensity and cost.

Once again, a familiar picture emerged. Medicare inpatient RVU rates grew quickly from 2000 onwards, peaking in 2008, before falling between 2009 and 2010. The compound annual growth rate for the 2000-2008 period was 2.9 percent, but from 2008 to 2010 RVU inpatient Medicare imaging rates slipped 5.9 percent. The percentage of overall Medicare imaging recipients who were inpatients also declined through this period, she said.

Advanced imaging pulls the brakes

Advanced imaging, that is CT and MRI, also fits the larger pattern. Once the poster boy for out-of-control imaging costs, it's one of the slowest-growing categories in the Medicare fee-for-service world, according, David Lee, a GE Healthcare economist.

In a report shared at RSNA, and co-written with analysts from the American College of Radiology's think tank, the Harvey L. Neiman Health Policy Institute, Lee and his colleagues compared advanced imaging to other series using the three-digit Berenson-Eggers service categories, which are used by researchers to measure Medicare spending.

This is what they found. From 2000 to 2006, growth in advanced imaging spending outstripped other health care services, Lee said. But after 2006, in the shadow of the DRA and other cuts, imaging growth tripped up. He said in the pre-DRA era it was at the 91st percentile for growth, but in the years following it had slipped to the 14th percentile, outpaced by such fast-rising categories as specialty care, nursing home care, anesthesia and ambulatory services.

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