Is it possible to define salvageable ischemic penumbra using semiquantitative rCBF levels derived from MR perfusion-weighted imaging?

Introduction: The purpose of this study was to test if magnetic resonance (MR) perfusion-weighted imaging (PWI) can reliably characterize the ischemic penumbra.
Materials and Methods: Sixteen patients with nonlacunar ischemic stroke who were scanned within 24 h after onset of symptoms were selected for the study. In previous studies, the level of regional cerebral blood flow (rCBF) in the normal white matter of the contralateral hemisphere was defined as 22 ml/100 g/min. We used this level as a standard of reference. We hypothesized that rCBF below this level would be amenable to infarct. The lesion-to-white matter ratios of rCBF were measured in the regions of ischemic core ("Core"), infarcted penumbra ("Growth"), salvaged penumbra ("Reversed"), and contralateral normal cortex ("Normal").
Results: The rCBF of "Growth" and "Reversed" areas showed substantial overlap, which hampered the delineation of areas that would become infarcted.
Conclusion: The semiquantitative rCBF derived from MR PWI may not accurately characterize the ischemic penumbra.