Alberta Stroke Program Early CT Scoring of CT Perfusion in Early Stroke Visualization and Assessment

Abstract

BACKGROUND AND PURPOSE:Qualitative CT perfusion (CTP) assessment by using the Alberta Stroke Program Early CT Score (ASPECTS) allows rapid calculation of infarct extent for middle cerebral artery infarcts. Published thresholds exist for noncontrast CT (NCCT) ASPECTS, which may distinguish outcome/complication risk, but early ischemic signs are difficult to detect. We hypothesized that different ASPECTS thresholds exist for CTP parameters versus NCCT and that these may be superior at predicting clinical and radiologic outcome in the acute setting.

Accuracy of the Alberta Stroke Program Early CT Score during the First 3 Hours of Middle Cerebral Artery Stroke: Comparison of Noncontrast CT, CT Angiography Source Images, and CT Perfusion

“…Parsons et al 10 reported similar findings in a prospective subcohort of 20 patients with MCA stroke, imaged within 6 hours of symptom onset, who achieved major reperfusion. We were particularly interested in the comparison of ASPECTS between CT perfusion CBV maps and CTA source images because both techniques have been shown to provide benefit over noncontrast CT. [7][8][9][10][11] We believe that CT perfusion CBV maps outperformed CTA source images in this study because of the inherent technical difference in determining blood volume between the 2 techniques. CTA source images provide an estimate of CBV by revealing regions of decreased enhancement but do so in a single "snapshot" during peak contrast enhancement.…”

“…We cautiously used the traditional cut-point of Յ7 in a brief subanalysis of our main results, but this may not be optimal for CT perfusion CBV maps. Parsons et al 10 and, more recently, Kloska et al 12 demonstrated better predictability of 90-day mRS with a cut-point of Յ6, whereas Aviv et al 11 recently reported an optimal cut-point of Յ8. The latter study had a lack of direct recanalization data and a small sam-ple size (only 7 patients had evidence of reperfusion).…”

“…Despite the lack of clinical outcome data, we believe our results are clinically relevant because previous studies have repeatedly shown that improving the accuracy of the acute ASPECTS allows it to be a better predictor of functional outcome. 7,8,10,11 The lack of follow-up data on functional independence prevented us from deriving the optimal ASPECTS cut-point for each technique that best predicts favorable outcome. We cautiously used the traditional cut-point of Յ7 in a brief subanalysis of our main results, but this may not be optimal for CT perfusion CBV maps.…”

“…[3][4][5][6] ASPECTS was designed for conventional noncontrast CT, the ubiquitously performed imaging technique for triaging acute stroke. However, several recent studies have reported application of ASPECTS to CT angiography (CTA) source images [7][8][9] and CT perfusion parametric color maps, [10][11][12] with data to suggest that the acute ASPECTS is more accurately determined on these advanced CT techniques. Our aim was to retrospectively compare the accuracy and strength of the correlation of the acute ASPECTSs obtained on noncontrast CT, CTA source images, and CT perfusion mapping of cerebral blood volume (CBV) for nonlacunar MCA territory strokes imaged during the initial 3 hours of symptom onset.…”

Computer-Aided Diagnosis of Hyperacute Stroke with Thrombolysis Decision Support Using a Contralateral Comparative Method of CT Image Analysis

“…Both CT angiography and MR angiography can be used to characterize intravascular thrombi. CT perfusion is a functional imaging technique that can be used to identify salvageable brain tissue [1,2]. Diffusion-weighted MR imaging can be used for identifying infarcted brain tissue that is irreversibly damaged, whereas perfusion-weighted MR imaging can be used for identifying reversibly injured ischemic brain tissue [3].…”