Perfusion imaging INSPIREs precision medicine in stroke

Stroke is a clinical syndrome with diverse causes and mechanisms. Historically, reliance on clinical diagnosis and exclusion of intracerebral hemorrhage and other nonstroke structural pathologies by CT alone has produced highly heterogeneous trial populations; as a result, any treatment effect has likely been obscured by the random noise of the many patients in whom no relevant biological target exists, a strategy that greatly inflates sample sizes.¹ Advances in brain and vascular imaging have driven the recent wave of positive clinical trials investigating reperfusion therapies in acute ischemic stroke, allowing the identification of patients with relevant therapeutic targets, such as intracranial large artery occlusion, clinically meaningful volumes of potentially reversible tissue hypoperfusion (the ischemic penumbra), and small volumes of irreversible tissue damage (the ischemic core). Combinations of angiographic and perfusion imaging, primarily using CT, allow pathophysiologic characterization of patients. The adoption of rigorous imaging selection in clinical trials based on the concept of treatment-related acute imaging targets² has allowed treatment effects to be demonstrated with achievable sample sizes, and validates the precision medicine concept in acute stroke.³