Estimation of regional cerebral blood flow levels in ischemia using [O-15]water or [C-11]flumazenil PET without arterial input function

Determination of residual flow within the ischemic brain may be important i n patients eligible for thrombolytic therapy. Conventional cerebral blood f low (CBF) quantification often cannot be achieved in these cases because ar terial blood sampling required for the input function is prohibited. Quanti tative CBF was measured in 20 patients with ischemic stroke using [O-15]wat er and [C-11]flumazenil PET with arterial blood sampling and compared with normalized nonquantified data of the same patients. For both comparisons, p ercentiles were derived, allowing the determination of a normalized blood f low level corresponding to an absolute CBF value below which 95% of all pix els are located. These normograms can be used to derive absolute CBF levels in milliliters per 100 g per minute from normalized data without the need for measuring an arterial input function.