<International Circulation>:  Do you think that surrogate end points (i.e. recanalization of a cerebral vessel) would be sufficient to determine approvability of a device? Neurological outcome， which should be the most important outcome in a stroke treatment trial， was a secondary end point in the MERCI study and was determined by comparing the outcome of treated patients to the placebo arm of PROACT II.

Prof. Lutsep: I am a neurologist therefore I am most interested in neurological outcomes. There are two main reasons that it has been difficult to compare the trials. We have used PROACT as a historic control. This sets a very high bar because the patients were less severely affected in PROACT than they were in the mechanical device trials because PROACT only included patients with middle cerebral artery strokes. The fact that it appeared that outcomes tended to be better than the patients in the non-treatment arm is encouraging， but you are comparing two very different things. Also， we are comparing two very different times in history and we are much better at treating strokes today. It would be ideal to have a head to head comparison and a randomized control trial. However， it is very expensive to conduct a trial like that and the longer these devices are on the market the more reluctant people are to randomize patients to lesser therapies.