Pretend you're a doctor. You're used to treating patients with a particular malady one way, but then a new technology comes on the market. It's unproven, but seems promising. So what do you do for your patients ? rely on the old way, or add the new? Many physicians, eager, to marshal the latest technology to help their patients, would opt for the new way. And patients would likely be eager to try it. That dynamic, however, makes it really difficult to conduct randomized trials of these new technologies to see if they actually do work. Doctors would have little incentive to participate in the trial rather than just start using the technology as they saw fit, and patients assigned to get standard treatment in a trial could simply go elsewhere to get the new treatment. That is, unless Medicare won't pay for it. That's exactly what happened in a study ? the results of which were just published in the New England Journal of Medicine ? comparing a beefed-up drug regimen to the drugs plus stenting to prevent a recurrence of stroke. The stents were placed in the arteries of the brain in an attempt to reduce blockages. And as it turned out, the study was stopped early after patients who received the stents experienced a higher risk of stroke and death after the procedure.