Stanford showing very nice benefit of TPA out to six hours if you can take a picture of the brain and show that the stroke has not gotten very big in that six hours so this is called penumbral imaging the penumbra means the part of the brain that is likely to die over the next few hours but is not yet dead so to be able to get to this we developed an MRI sequence called diffusion imaging it was one of the Stanford faculty members who discovered this MRI technique which allows you to see the stroke as it's occurring before