Evaluation the sensitivity of diffusion and perfusion weighted imaging in therapeutic timing of stroke

The concept of ischemic penumbra was defined as an area of reduced in cerebral blood flow [CBF] with electrical failure but preserved ion homeostasis and trans-membrane electrical potentials. Then, some other definitions for the ischemic penumbra have been proposed based on energy metabolism, CBF thresholds and protein synthesis. Hypothermia reduced ischemic lesion volume on diffusion weighted imaging [DWI] and may improve functional outcome. Since, the DWI show initial reduction with no abnormal change on T2W or fluid attenuated inversion-recovery [FLAIR] images in hyper acute stroke, a DWI-T2W mismatch was proposed to represent the ischemic penumbra. The DWI-T2W mismatch was defined as a hyper intense lesion on DWI [lowed] with no hyper intense lesion on T2WI or FLAIR, and no hypo intense lesion on T1WI. Perfusion weighted imaging [PWI] of the entire brain is one of the main advantages of PWI, in which MMT or TTP perfusion maps are generated for the entire brain. Like CT perfusion, it can identify the ischemic penumbra. The ischemic penumbra is the difference between the DWI defect [cytotoxic edema-irreversible ischemia- the ischemic core] and the perfusion defect-analogous to MTT or TTP]. The penumbra is the DWI-PWI mismatch. The accurate identification of this ischemic penumbra will help ischemic stroke therapy and potentially aide in extending the time window for treatment in the future.