1. A method for creating a penumbra image of the brain of an acute stroke patient comprising: obtaining measurements of the cerebral blood flow and cerebral blood volume of the brain of an acute stroke patient determining ischemic areas of the brain, said ischemic areas determined where said measurements of cerebral blood flow is a predetermined first value less than normal cerebral blood flow of an unaffected corresponding portion of the brain; creating a penumbra map comprising penumbra areas of the ischemic areas of the brain using said measurements, wherein penumbra areas correspond to ischemic areas of the brain having cerebral blood volume greater than said predetermined second value.