Advances in Imaging

Abstract

Imaging is still playing a major role in acute stroke management, stroke recovery, and stroke prevention. Each of these areas continued to see marked activity in the imaging field over the past year; this review will focus just on the first of these because of space constraints. With the need of more effective therapies for acute ischemic stroke, the search for a clinically applicable and reliable method to detect functionally impaired but still viable and potentially salvageable tissue—aka the penumbra—continues. Positron emission tomography using 15O-tracers still represents the best available method for the identification of brain regions with reduced cerebral metabolic rate of oxygen use (CMRO2) that are thought to distinguish them from the ischemic core where oxygen extraction and use is greatly diminished. The mismatch between perfusion-weighted and diffusion-weighted imaging (PW–DWI) signals provides an estimate of the extent of the penumbra, but as shown in a comparative study, the volume of mismatch often is not in agreement with the volume of increased oxygen extraction fraction.1 This resulting overestimation of the volume of the penumbra, as identified by PET, is partly due to reversibility of diffusion-weighted changes but more importantly to inaccuracies …