Standardization of Stroke Perfusion CT for Reperfusion Therapy
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REVIEW ARTICLE
Standardization of Stroke Perfusion CT for Reperfusion Therapy Guangming Zhu & Patrik Michel & Weiwei Zhang & Max Wintermark
Received: 7 March 2012 / Accepted: 13 March 2012 / Published online: 28 March 2012 # Springer Science+Business Media, LLC 2012
Abstract With the advances in terms of perfusion imaging, the “time is brain” approach used for acute reperfusion therapy in ischemic stroke patients is slowly being replaced by a “penumbra is brain” or “imaging is brain” approach. But the concept of penumbra-guided reperfusion therapy has not been validated. The lack of standardization in penumbral imaging is one of the main contributing factors for this absence of validation. This article reviews the issues underlying the lack of standardization of perfusion-CT for penumbra imaging, and offers avenues to remedy this situation. Keywords Stroke perfusion CT . Reperfusion therapy . Standardization
Introduction Stroke is a leading cause of mortality and disability worldwide, with 15 million patients suffering a stroke annually. Treatment options exist but are limited. More specifically, G. Zhu : M. Wintermark (*) Department of Radiology, Neuroradiology Division, University of Virginia, Box 800170, Charlottesville, VA 22908, USA e-mail: [email protected] G. Zhu : W. Zhang Department of Neurology, Military General Hospital of Beijing PLA, Beijing, China P. Michel Department of Neurology, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
thrombolytic agents and mechanical thrombolytic devices have limited time windows, and moderate success in terms of recanalization and reperfusion. This has led to the concept of penumbra imaging, where patients with a favorable imaging signature would be considered as potential good responders and would be administered acute reperfusion therapy, even beyond the typically accepted time window [1]. However, this concept of penumbra-guided reperfusion therapy failed to be validated in two recent phase III trials [2, 3] and, as a result, has not become part of the clinical standard-of-care yet. One of main contributing factors for this is the lack of standardization in penumbral imaging, which can result in different treatment decisions in the same patient when different penumbral imaging methods are applied to the same perfusion imaging dataset [4]. The goal of this article is to review the key issues and challenges responsible for the current limitations of perfusion-CT penumbra imaging and to suggest potential solutions and avenues to facilitate the standardization of PCT and its use for acute stroke patient selection for reperfusion therapy.
Perfusion-CT and Penumbra Pathophysiological Penumbra Versus Operational Penumbra The ischemic penumbra can be defined in multiple ways, at multiple pathophysiological levels. Some researchers have proposed vascular definitions of the penumbra, using either cerebral blood flow thresholds to delineate the ischemic penumbra on imaging [5], or relying on the concept cerebral vascular autoregulation (preserved in
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