<International Circulation>: What is the difference between the first generation mechanical devices for clot removal， the MERCI device and the new generation device PENUMBRA system?

Prof. Lutsep: There are really two that are being asked. The MERCI device itself has been changed over time. For example， in the MERCI trial compared to the Multi MERCI trial， the design of the device was changed. Even since then there have been new iterations of the MERCI retriever device. It is still based on the corkscrew concept where it releases these loops into the clot and pulls the clot out. The PENUMBRA device works on a different basis in that it applies aspiration to the clock. Therefore， the two devices have different mechanisms.