Ischemic penumbra: evidence from functional imaging in man.

摘要: The ischemic penumbra is defined as tissue with flow within the thresholds for maintenance of function and morphologic integrity. Penumbra has potential recovery therefore target interventional therapy in acute stroke. identification necessitates measuring reduced less than functional threshold differentiating between integrity damage. This can be achieved by multitracer positron emission tomography (PET) perfusion-weighted (PW) diffusion-weighted magnetic resonance imaging (DW-MRI) experimental models, which critically perfused or its conversion to infarction was documented repeat studies. Neuroimaging modalities applied patients stroke--multitracer PET, PW- DW-MRI, single photon computed (SPECT), perfusion, Xe-enhanced (CT)-- often cannot reliably identify tissue: studies assessment irreversible metabolic damage usually performed clinical setting; CT MRI do not detect first hours after stroke, even DW-MRI may misleading some cases: determinations perfusion alone yield a poor estimate state long time course changes known individual cases. Therefore, range values found later, either outside infarct, rather broad. New tracers--for example, receptor ligands hypoxia markers--might improve future. Despite these methodologic limitations, validity concept proven several therapeutic thrombolytic treatment reversed critical ischemia decreased volume final infarcts. Such neuroimaging findings might serve surrogate targets selection other strategies large trials.