Perfusion computed tomography: Prediction of final infarct extent and stroke outcome

Abstract

The Alberta Stroke Program Early Computed Tomography Score (ASPECTS) has not been previously applied to perfusion CT (CTP). Five raters assigned ASPECTS to baseline noncontrast CT (NCCT), CT angiography source images (CTA-SI), CTP source images (CTP-SI), and CTP maps of cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) from 37 consecutive patients with less than 6-hour anterior circulation ischemic stroke. Major reperfusion was identified on follow-up imaging. Mean baseline ASPECTS was compared with follow-up imaging ASPECTS. Rates of favorable outcome were compared for dichotomized baseline ASPECTS. In patients with major reperfusion, mean CBV and CTP-SI ASPECTS closely predicted final infarct ASPECTS. In patients without major reperfusion, mean CBF and MTT ASPECTS best predicted final infarct ASPECTS. There were significant increases in rates of favorable outcome for CTP-SI and CBV ASPECTS of greater than 6, versus less than or equal to 6, but not for other baseline CT modalities. ASPECTS applied to CTP is more accurate at identifying the extent of reversible and irreversible ischemia and at predicting final clinical outcome than NCCTor CTA-SI.

Extent of Hypoattenuation on CT Angiography Source Images Predicts Functional Outcome in Patients With Basilar Artery Occlusion

“…7 Compared to CTASI, perfusion CT (CTP) better delineates the ischemic core and can identify areas of salvageable brain tissue in anterior circulation stroke. 24,25 Similar findings in the posterior circulation are conceivable. Comparison of CTA, CTP and multimodal MRI to predict outcome and treatment response in patients with BAO could be subject of future studies.…”

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.…”