Visual evaluation of perfusion CT imaging in acute stroke accurately estimates infarct volume and tissue viability

¹ University of Glasgow, United Kingdom
² Institute of Neurological Sciences, Glasgow, United Kingdom

^* To whom correspondence should be addressed. E-mail: k.muir{at}clinmed.gla.ac.uk.

Accepted 12 October 2005

	Abstract

Background: Functional imaging by perfusion CT provides information on tissue viability and brain perfusion, but post-processing of data limits clinical utility in acute treatment decisions. We sought to establish the validity of visual interpretation of immediately processed perfusion CT maps in acute stroke for prediction of final infarction.

Methods: Prospectively acquired perfusion CT studies of patients within 6h of stroke onset were re-processed using standard CT console software and visually examined by a single observer. Four contiguous 5mm thick images were obtained and maps of time to peak (TTP) and cerebral blood volume (CBV) generated. Volumes of lesions identified only by visual inspection were measured from manually drawn regions of interest. Volumes of tissue with prolonged TTP or reduced CBV were compared to independently calculated volume of infarction on non-contrast CT (NCCT) at 24-48 hours, and with clinical severity using the National Institute of Health Stroke Scale score. Arterial patency at 24-48h was included in analyses.

Results: Studies from 17 patients a median 150 minutes from stroke onset were analysed. The volume of tissue with prolonged TTP correlated with initial NIHSS (r=0.62, p=0.009), and with NCCT final infarct volume when arterial occlusion persisted (r=0.953, p=0.012). The volume of tissue with reduced CBV correlated with final infarct volume if recanalisation occurred (r=0.835, p=0.001). Recanalisation was associated with lower 24h NIHSS (6 [interquartile range 5,9.5] versus 19 [18, 26], p=0.027), and in 10 patients given rtPA for MCA M1 occlusion, also with lower infarct volume (431 v 73 ml, p=0.002).

Conclusions: Visual evaluation of TTP and CBV maps generated by standard perfusion CT software correlated with 24-48 hour CT infarct volumes. Comparison of TTP and CBV maps yields information on tissue viability. Perfusion CT therefore represents a practical technique to aid acute clinical decision making. Recanalisation was a crucial determinant of clinical and radiological outcome.

Keywords: computed tomography, perfusion imaging, stroke, thrombolytic drug treatment

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