Perfusion CT is a recent CT based imaging modality Used to describe &Evaluate Cerebral perfusion by estimating relative Values Of different cerebralPerfusion Parameters as Cerebral blood Floe , Cerebral blood Volume & meanTransit time.Iodinated Contrast medium is used & Spiral Or multi-sline CT System areEssential For the technique.It is Found to be useful in evaluation of different Cerebral ischemic conditionsIncluding that associated With Stroke as Well as non-strok Conditions.Perfusion CT is helpful in assement of cerebrovascular reserve in Patients WithChronic Cerebral ischemic conditions for Cerebral Vascular bypass Surgery &Patients undergoing temporary balloon Occlusion test as Well as Patients WithSymptoms Of Vasospasm after Subarachnoid hemorrhage.