Evaluation of Hypoxic Tissue Dynamics with 18F-FMISO PET in a Rat Model of Permanent Cerebral Ischemia

Purpose[18F]Fluoromisonidazole (18F-FMISO) is a nitroimidazole derivative that has been proposed as a positron emission tomography (PET) radiotracer to detect hypoxic tissue in vivo. This compound accumulates in hypoxic but viable tissue and may be a good candidate for evaluating the ischemic penumbra. We evaluated the time course of 18F-FMISO uptake using PET in a rat model of permanent cerebral ischemia and the correlation with histological changes.ProceduresRats (n = 14) were subjected to permanent ischemia by intraluminal occlusion of the middle cerebral artery in order to assess by PET the uptake of 18F-FMISO at various times over 24 h following ischemia. The PET results were compared to histological changes with Nissl and 2,3,5 triphenyltetrazolium chloride staining.ResultsElevated uptake of 18F-FMISO was detected in the infarcted area up to 8 h after occlusion but was no longer detected at 24 h, a time point coincident with pan necrosis of the tissue.ConclusionsOur findings suggest that salvageable tissue persists for up to 8 h in this rat model of brain ischemia. We propose 18F-FMISO PET as a tool for evaluating the ischemic penumbra after cerebral ischemia.

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