The Alberta Stroke Program Early CT Score in Clinical Practice: What have We Learned?

Improving prediction of recanalization in acute large-vessel occlusive stroke

BACKGROUND

Recanalization in acute ischemic stroke with large-vessel occlusion is a potent indicator of good clinical outcome.

OBJECTIVE

To identify easily available clinical and radiologic variables predicting recanalization at various occlusion sites.

METHODS

All consecutive, acute stroke patients from the Acute STroke Registry and Analysis of Lausanne (2003-2011) who had a large-vessel occlusion on computed tomographic angiography (CTA) (< 12 h) were included. Recanalization status was assessed at 24 h (range: 12-48 h) with CTA, magnetic resonance angiography, or ultrasonography. Complete and partial recanalization (corresponding to the modified Treatment in Cerebral Ischemia scale 2-3) were grouped together. Patients were categorized according to occlusion site and treatment modality.

RESULTS

Among 439 patients, 51% (224) showed complete or partial recanalization. In multivariate analysis, recanalization of any occlusion site was most strongly associated with endovascular treatment, including bridging therapy (odds ratio [OR] 7.1, 95% confidence interval [CI] 2.2-23.2), and less so with intravenous thrombolysis (OR 1.6, 95% CI 1.0-2.6) and recanalization treatments performed beyond guidelines (OR 2.6, 95% CI 1.2-5.7). Clot location (large vs. intermediate) and tandem pathology (the combination of intracranial occlusion and symptomatic extracranial stenosis) were other variables discriminating between recanalizers and non-recanalizers. For patients with intracranial occlusions, the variables significantly associated with recanalization after 24 h were: baseline National Institutes of Health Stroke Scale (NIHSS) (OR 1.04, 95% CI 1.02-1.1), Alberta Stroke Program Early CT Score (ASPECTS) on initial computed tomography (OR 1.2, 95% CI 1.1-1.3), and an altered level of consciousness (OR 0.2, 95% CI 0.1-0.5).

CONCLUSIONS

Acute endovascular treatment is the single most important factor promoting recanalization in acute ischemic stroke. The presence of extracranial vessel stenosis or occlusion decreases recanalization rates. In patients with intracranial occlusions, higher NIHSS score and ASPECTS and normal vigilance facilitate recanalization. Clinical use of these predictors could influence recanalization strategies in individual patients.

Prediction of outcome in patients with suspected acute ischaemic stroke with CT perfusion and CT angiography: the Dutch acute stroke trial (DUST) study protocol

Background

Prediction of clinical outcome in the acute stage of ischaemic stroke can be difficult when based on patient characteristics, clinical findings and on non-contrast CT. CT perfusion and CT angiography may provide additional prognostic information and guide treatment in the early stage. We present the study protocol of the Dutch acute Stroke Trial (DUST). The DUST aims to assess the prognostic value of CT perfusion and CT angiography in predicting stroke outcome, in addition to patient characteristics and non-contrast CT. For this purpose, individualised prediction models for clinical outcome after stroke based on the best predictors from patient characteristics and CT imaging will be developed and validated.

Methods/design

The DUST is a prospective multi-centre cohort study in 1500 patients with suspected acute ischaemic stroke. All patients undergo non-contrast CT, CT perfusion and CT angiography within 9 hours after onset of the neurological deficits, and, if possible, follow-up imaging after 3 days. The primary outcome is a dichotomised score on the modified Rankin Scale, assessed at 90 days. A score of 0–2 represents good outcome, and a score of 3–6 represents poor outcome. Three logistic regression models will be developed, including patient characteristics and non-contrast CT (model A), with addition of CT angiography (model B), and CT perfusion parameters (model C). Model derivation will be performed in 60% of the study population, and model validation in the remaining 40% of the patients. Additional prognostic value of the models will be determined with the area under the curve (AUC) from the receiver operating characteristic (ROC) curve, calibration plots, assessment of goodness-of-fit, and likelihood ratio tests.

Discussion

This study will provide insight in the added prognostic value of CTP and CTA parameters in outcome prediction of acute stroke patients. The prediction models that will be developed in this study may help guide future treatment decisions in the acute stage of ischaemic stroke.

Recanalisation success is independent of ASPECTS in predicting outcomes after intra-arterial therapy for acute ischaemic stroke

Intra-arterial (IA) therapy for stroke is an increasingly utilised management approach for acute ischaemic stroke. We aimed to correlate radiological characteristics and recanalisation success with radiological and functional outcomes at 90 days in patients treated with IA therapy. This was a single centre, retrospective study investigating the correlation between pre-procedural Computed Tomography-Angiogram Source Image (CTA-SI) Alberta Stroke Program Early Computed Tomography Score (ASPECTS), recanalisation success, and functional outcome at 90 days in patients with an acute ischaemic stroke from 2007-2012. Outcome measures were pre-procedural non-contrast computed tomography (NCCT), CTA-SI, and post-procedural NCCT ASPECTS that were obtained and analysed by three blinded reviewers, recanalisation success (Thrombolysis in Cerebral Infarction [TICI] 2b-3) and favourable clinical outcome (90 day modified Rankin scale [mRS] score ≤ 2). Forty-four patients satisfied the inclusion criteria. The mean age was 64.2 years (standard deviation: 14.9; median: 66.5; interquartile range [IQR]: 54.5-76.5). The median National Institutes of Health Stroke Scale score was 17 (IQR: 13.5-20). Twenty-one (47.7%) patients achieved a mRS score ≤ 2. The 90 day mortality rate was 25.0% (n=11). Of the patients who achieved TICI ≥ 2b-3, 65.5% (19/29) achieved mRS 2. There was a statistically significant association between recanalisation success (TICI 2b) and favourable neurological outcome at 90 days (odds ratio [OR] 25.22, 95% confidence interval [CI]: 2.86-222.37, p<0.005). Patients with high pre-procedural CTA-SI ASPECTS are significantly more likely to have high post-procedural NCCT score (OR 23.36, 95% CI: 3.26-166.92, p=0.002). Recanalisation success was strongly associated with good clinical outcome, unaffected by known predictive factors, which included age and stroke severity. This association was unattenuated by CTA-SI ASPECTS.

Alberta Stroke Program early computed tomography score to select patients for endovascular treatment: Interventional Management of Stroke (IMS)-III Trial

BACKGROUND AND PURPOSE

The Interventional Management of Stroke (IMS)-III trial randomized patients with acute ischemic stroke to intravenous tissue-type plasminogen activator (tPA) plus endovascular therapy versus intravenous tPA therapy alone within 3 hours from symptom onset. A predefined secondary hypothesis was that subjects with significant early ischemic change on the baseline scan would not respond to endovascular therapy.

METHODS

The primary outcome was 90-day modified Rankin Scale score 0 to 2. The baseline and follow-up computed tomographic (CT) scan images were reviewed centrally and blinded to any clinical information. We assessed whether the baseline Alberta Stroke Program Early CT Score (ASPECTS) predicted outcome and interacted with study treatment. We analyzed subgroups defined by time from onset to intravenous tPA initiation and baseline occlusion status at a prespecified α=0.01.

RESULTS

Baseline demographic and clinical characteristics of 656 randomized patients were similar between subjects with a baseline ASPECTS 8 to 10 (58% of the study sample) versus 0 to 7. Subjects with ASPECTS 8 to 10 were almost twice as likely (relative risk, 1.8; 99% confidence interval, 1.4-2.4) to achieve a favorable outcome. There was insufficient evidence of a treatment-by-ASPECTS interaction. In those treated with onset to intravenous tPA <120 minutes, in CT angiography-proven internal carotid artery or middle cerebral artery occlusion, and in both, results were similar. The probability of achieving recanalization (arterial occlusion lesion, 2-3) of the primary arterial occlusive lesion (relative risk, 1.3; 99% confidence interval, 1.0-1.8) or achieving thrombolysis in cerebral ischemia score 2b/3 reperfusion (relative risk 2.0; 99% confidence interval, 1.2-3.2) was higher among subjects with higher ASPECTS.

CONCLUSIONS

ASPECTS is a strong predictor of outcome and a predictor of reperfusion. ASPECTS did not identify a subpopulation of subjects that particularly benefitted from endovascular therapy immediately after routine intravenous tPA.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT00359424.

Reliability of visual assessment of non-contrast CT, CT angiography source images and CT perfusion in patients with suspected ischemic stroke

Background and Purpose

Good reliability of methods to assess the extent of ischemia in acute stroke is important for implementation in clinical practice, especially between observers with varying experience. Our aim was to determine inter- and intra-observer reliability of the 1/3 middle cerebral artery (MCA) rule and the Alberta Stroke Program Early CT Score (ASPECTS) for different CT modalities in patients suspected of acute ischemic stroke.

Methods

We prospectively included 105 patients with acute neurological deficit due to suspected acute ischemic stroke within 9 hours after symptom onset. All patients underwent non-contrast CT, CT perfusion and CT angiography on admission. All images were evaluated twice for presence of ischemia, ischemia with >1/3 MCA involvement, and ASPECTS. Four observers evaluated twenty scans twice for intra-observer agreement. We used kappa statistics and intraclass correlation coefficient to calculate agreement.

Results

Inter-observer agreement for the 1/3 MCA rule and ASPECTS was fair to good for non-contrast CT, poor to good for CT angiography source images, but excellent for all CT perfusion maps (cerebral blood volume, mean transit time, and predicted penumbra and infarct maps). Intra-observer agreement for the 1/3 MCA rule and ASPECTS was poor to good for non-contrast CT, fair to moderate for CT angiography source images, and good to excellent for all CT perfusion maps.

Conclusion

Between observers with a different level of experience, agreement on the radiological diagnosis of cerebral ischemia is much better for CT perfusion than for non-contrast CT and CT angiography source images, and therefore CT perfusion is a very reliable addition to standard stroke imaging.

Clinical relevance and practical implications of trials of perfusion and angiographic imaging in patients with acute ischaemic stroke: a multicentre cohort imaging study

BACKGROUND

In randomised trials testing treatments for acute ischaemic stroke, imaging markers of tissue reperfusion and arterial recanalisation may provide early response indicators.

OBJECTIVE

To determine the predictive value of structural, perfusion and angiographic imaging for early and late clinical outcomes and assess practicalities in three comprehensive stroke centres.

METHODS

We recruited patients with potentially disabling stroke in three stroke centres, performed magnetic resonance (MR) or CT, including perfusion and angiography imaging, within 6 h, at 72 h and 1 month after stroke. We assessed the National Institutes of Health Stroke Scale (NIHSS) score serially and functional outcome at 3 months, tested associations between clinical variables and structural imaging, several perfusion parameters and angiography.

RESULTS

Among 83 patients, median age 71 (maximum 89), median NIHSS 7 (range 1-30), 38 (46%) received alteplase, 41 (49%) had died or were dependent at 3 months. Most baseline imaging was CT (76%); follow-up was MR (79%) despite both being available acutely. At presentation, perfusion lesion size varied considerably between parameters (p<0.0001); 40 (48%) had arterial occlusion. Arterial occlusion and baseline perfusion lesion extent were both associated with baseline NIHSS (p<0.0001). Recanalisation by 72 h was associated with 1 month NIHSS (p=0.0007) and 3 month functional outcome (p=0.048), whereas tissue reperfusion, using even the best perfusion parameter, was not (p=0.11, p=0.08, respectively).

CONCLUSION

Early recanalisation on angiography appeared to predict clinical outcome more directly than did tissue reperfusion. Acute assessment with CT and follow-up with MR was practical and feasible, did not preclude image analysis, and would enhance trial recruitment and generalisability of results.

Proof of concept study: relating infarct location to stroke disability in the NINDS rt-PA trial

BACKGROUND

The summed Alberta Stroke Program Early CT Score (ASPECTS) for noncontrast head CT scan represents the extent of early brain ischemia and has been shown to be useful for predicting stroke outcome. The ASPECTS template contains information on anatomical location which so far has not been used in analysis. This may not have been done because adjacent brain regions have related functions and share vascular territory. The task of relating neurological deficit to infarct localization requires brain imaging analysis tools which deal with this issue of relatedness or collinearity. We have previously used partial least squares with penalized logistic regression (PLR) to handle this problem of collinearity. A disadvantage of this method is that it cannot be performed at the bedside and requires processing and analysis in the imaging laboratory. PLR is a simpler analytic tool compared to partial least squares with PLR for dealing with this issue of relatedness (collinearity). It provides results in terms of β coefficients related to specific infarct locations in a manner that is intuitively understood by clinicians. In this exploratory analysis, we hypothesized that infarct location as represented by the individual ASPECTS region may be independently related to disability.

METHODS

ASPECTS from CT scans of patients in the National Institute of Neurological Disorders and Stroke (NINDS) recombinant tissue plasminogen activator (rt-PA) Study were obtained. Due to the collinearity between the ASPECTS regions, we used PLR to determine the independent associations of exposures (rt-PA), demographic variables (age and sex), and imaging (ASPECTS location) with poor outcome as defined by a modified Rankin Scale score of >2.

RESULTS

In 607/624 subjects with ASPECTS readings, variables significantly associated with poor outcome included: interactions between ASPECTS M6 region (primary motor cortex/parietal lobe) and age (p = 0.004), lentiform nucleus and age (p = 0.007), and blood sugar level and age (p = 0.01). The model suggested that older age or involvement of either M6 or lentiform nucleus slightly increased the odds of disability. However, the predominant effect was driven by rt-PA which reduced the odds of poor disability (OR 0.597, 95% CI 0.425-0.838, p = 0.003). This may potentially explain why certain patients have smaller gains from rt-PA treatments.

CONCLUSION

At an older age, specific infarct locations may be associated with a poorer outcome in this exploratory re-analysis of the NINDS rt-PA Study.

Imaging-based selection in acute ischemic stroke trials - a quest for imaging sweet spots

Ischemic stroke is a very heterogeneous disease that limits the efficacy of acute stroke treatments. Future trials will require advanced imaging to select patients for specific treatments. The most well-established imaging tools are the use of CT to exclude hemorrhage and diffusion-weighted MRI to demonstrate ischemia. While perfusion imaging is one option for patient selection, it has unresolved issues, including standardization and validation, that limit its value. As an alternative to mismatch when addressing stroke, one needs to know the size of the initial irreversible lesion (core), the presence and site/extent of occlusion (clot), and presence of leptomeningeal back filling and Willisian filling (collaterals). These can be summarized as the "3C" approach of core, clot, and collateral interpretation, which together can represent an imaging sweet spot, particularly for time-efficient endovascular treatment trial design.

Intravenous alteplase for Chinese patients with stroke and borderline eligibility

Lack of efficacy and safety data among Chinese patients with stroke have contributed to the slow development of stroke thrombolysis as standard-of-care for these patients. We examined a retrospective cohort of 57 patients who received intravenous alteplase for acute ischemic stroke to identify predictors of outcome, including age, stroke severity, onset-to-treatment time, and early ischemic changes on brain CT scan. Overall, the mean National Institute of Health Stroke Scale (NIHSS) score was 15.7 and the mean onset-to-treatment time was 142 minutes. Twenty-nine (51%) patients had a favorable outcome with modified Rankin Scale (mRS) score of ≤2 at three months. Ten (17.5%) patients were deceased at three months. Four (7%) patients developed symptomatic intracranial hemorrhage (sICH). For patients aged >80 years (n=18), five (28%) achieved favorable outcome, six (33%) were deceased at three months and three (17%) had sICH. Prognosis was worst for patients with NIHSS score >25 (n=5); one (20%) was dependent (mRS 4) and the other four (80%) were deceased. Multivariate analysis found that the Alberta Stroke Program Early CT Score (ASPECTS) was associated with favorable outcome (odds ratio [OR] 1.8, 95% confidence interval [CI] 1.1-3.0), and mortality (OR 0.5, 95% CI 0.3-0.9). Our findings showed advanced age and severe stroke were associated with less favorable outcome in Chinese patients receiving intravenous alteplase, ASPECTS can be used reliably to identify patients at risk of poor outcomes. Further studies are warranted.

The evolution of the cerebral blood volume abnormality in patients with ischemic stroke: a CT perfusion study

BACKGROUND

Accurate identification of the acute infarct core abnormality is important for guiding acute stroke treatment. Abnormality volumes from diffusion-weighted MRI (DWI) and CT perfusion (CTP)-cerebral blood volume (CBV) are highly correlated. DWI lesions have been shown to be reversible at 24 h.

PURPOSE

To examine the temporal profile of the CT perfusion (CTP)-derived CBV abnormality out to 7 days post ischemic stroke.

MATERIAL AND METHODS

Twenty-six patients were included. Group A (n = 13) underwent a non-contrast CT (NCCT), CTP/CT angiography (CTA) within 6 h of stroke onset, CTP/CTA at 24 h, and CTP/NCCT at 5-7 days post stroke. Group B (n = 13) underwent a NCCT, CTP/CTA within 6 h of stroke onset, and NCCT at 5-7 days. Recanalization status was established in all patients. For both groups, infarct volumes were traced on 5-7 day NCCT images and superimposed onto all CTP-CBV functional maps to determine CBV. Group B (n = 13) admission images were used to define CBV infarct thresholds for gray and white matter. CBV-lesion over-estimation was determined for Group A using the thresholds from Group B.

RESULTS

CBV (mL·100g(- 1); mean ± stdev) for gray/white matter, within confirmed infarcted regions (CBV(I)) at admission, 24 h, and 5-7 days were 1.82 ± 0.56, 1.56 ± 0.42, 1.75 ± 0.31, and 1.38 ± 0.65, 1.13 ± 0.31, 1.32 ± 0.44, respectively, when averaged over all patients (P > 0.05). Four patients had tissue time-density curves from ischemic lesions (TDC(i)) with an incomplete contrast medium wash-out phase (truncation) at admission and/or 24 h. Compared to admission, gray matter CBV(I) was higher at 5-7 days for patients with TDC(i) truncation (P < 0.05). There were no significant CBV(I) increases for the eight patients without truncation (P > 0.05). Over-estimation of acute CBV lesion was present in 3/4 (75%) and 1/9 (11%) of patients with/without TDC(i) truncation, respectively.

CONCLUSION

CTP-derived CBV lesion reversal is associated with TDC(i) truncation during the acute stroke phase.

ASPECTS and other neuroimaging scores in the triage and prediction of outcome in acute stroke patients

Information obtained from brain imaging is now summarized in the form of various neuroimaging scores to help physicians in making therapeutic decisions and determining prognosis. The Alberta Stroke Program Early CT Score (ASPECTS) was devised to quantify the extent of early ischemic changes in the middle cerebral artery territory on noncontrast computed tomography. With its systematic approach, the score is simple, reliable, and a strong predictor of functional outcome. This review summarizes ASPECTS and other neuroimaging scores developed for risk prognostication and risk stratification with treatment in patients with acute ischemic stroke.

Interobserver reliability of baseline noncontrast CT Alberta Stroke Program Early CT Score for intra-arterial stroke treatment selection

BACKGROUND AND PURPOSE

Early ischemic changes on pretreatment NCCT quantified using ASPECTS have been demonstrated to predict outcomes after IAT. We sought to determine the interobserver reliability of ASPECTS for patients with AIS with PAO and to determine whether pretreatment ASPECTS dichotomized at 7 would demonstrate at least substantial κ agreement.

MATERIALS AND METHODS

From our prospective IAT data base, we identified consecutive patients with anterior circulation PAO who underwent IAT over a 6-year period. Only those with an evaluable pretreatment NCCT were included. ASPECTS was graded independently by 2 experienced readers. Interrater agreement was assessed for total ASPECTS, dichotomized ASPECTS (≤ 7 versus >7), and each ASPECTS region. Statistical analysis included determination of Cohen κ coefficients and concordance correlation coefficients. PABAK coefficients were also calculated.

RESULTS

One hundred fifty-five patients met our study criteria. Median pretreatment ASPECTS was 8 (interquartile range 7-9). Interrater agreement for total ASPECTS was substantial (concordance correlation coefficient = 0.77). The mean ASPECTS difference between readers was 0.2 (95% confidence interval, -2.8 to 2.4). For dichotomized ASPECTS, there was a 76.8% (119/155) observed rate of agreement, with a moderate κ = 0.53 (PABAK = 0.54). By region, agreement was worst in the internal capsule and the cortical areas, ranging from fair to moderate. After adjusting for prevalence and bias, agreement improved to substantial or near perfect in most regions.

CONCLUSIONS

Interobserver reliability is substantial for total ASPECTS but is only moderate for ASPECTS dichotomized at 7. This may limit the utility of dichotomized ASPECTS for IAT selection.

Computed Tomography Perfusion Prognostic Maps Do Not Predict Reversible and Irreversible Neurological Dysfunction following Reperfusion Therapies

Background

We aimed to evaluate the ability of commercially available computed tomography perfusion (CTP) prognostic maps software to identify reversibly and irreversibly damaged brain functions in the best case scenario: patients who achieved early and complete tissue reperfusion.

Methods

Consecutive ischemic stroke patients who received reperfusion therapies, those with early (less than two-hours from treatment initiation) and complete Thrombolysis in Myocardial Infarction grade III or equivalent reperfusion were included in the analysis. Computed tomography perfusion prognostic maps were assigned as ‘red,’ or irreversible if cerebral blood volume declined below 2 ml/100 g and ‘green,’ or recoverable if the affected/unaffected mean transit time ratio was >1·45. Only patients with middle cerebral artery territory affected were included and subcomponents of the National Institutes of Health Stroke Scale scale pre- and posttreatment were analyzed based on anatomical correlation of the affected CTP areas and corresponding neurological functions.

Results

Among 109 consecutive patients who had intra-arterial reperfusion procedures, 16 (age 60±17 years, 56% men, median National Institutes of Health Stroke Scale 13·5, interquartile range 7–18) had pretreatment CTP and had early complete reperfusion. We identified 44 affected areas on CTP (red 12 (27%), green 32 (73%)) with corresponding measurable neurological deficits including aphasia, arm, face weakness, and inattention. Red areas correctly identified 5/12 (42%) of functions that did not recover despite early reperfusion. Green areas correctly identified 18/32 (56%) of functions that recover after early reperfusion (OR 0·92, 95% CI 0·25–3·39, P=1·0).

Conclusions

In-patients achieving early and complete reperfusion, pretreatment CTP prognostic maps were not predictive for irreversibly or reversibly lost neurologic functions.

Hospital-based management of acute ischemic stroke following intravenous thrombolysis

Timely administration of proven therapies remains the primary goal in acute stroke care. Following reperfusion therapy with intravenous thrombolysis, medical and neurological complications may develop in the hospitalized patient with acute ischemic stroke. Medical complications may include deep venous thrombosis, pulmonary embolism, aspiration, systemic infections and neuropsychiatric disturbances. Neurologic complications may include symptomatic intracranial hemorrhage, cerebral edema with elevated intracranial pressure, and post-stroke seizures. Early initiation of preventative strategies and proper management of common complications may improve both short-term and long-term outcomes. Here we review evidence-based management strategies for hospitalized acute ischemic stroke patients following intravenous thrombolysis.

CT Angiographic Source Images Predict Outcome and Final Infarct Volume Better Than Noncontrast CT in Proximal Vascular Occlusions

Background and Purpose—

Alberta Stroke Programme Early CT Score (ASPECTS) is widely used for assessment of early ischemic changes in acute stroke. We hypothesized that CT angiography source image (CTA-SI) ASPECTS correlates better with baseline National Institutes of Health Stroke Scale score, final ASPECTS and neurological outcomes when compared with noncontrast CT ASPECTS.

Methods—

We studied patients presenting with acute ischemic stroke and identified proximal arterial occlusions (internal carotid artery, middle cerebral artery M1, and proximal middle cerebral artery M2) from the Calgary CT Angiography database. CT scans were independently read by 3 observers for baseline noncontrast CT ASPECTS, CT angiography source image ASPECTS, and follow-up ASPECTS. Details of demographics and risk factors were noted. A modified Rankin Scale score ≤2 at 3 months was considered a favorable outcome.

Results—

We identified 261 patients with proximal occlusions for analysis. We found a better correlation between CT angiography source image ASPECTS and follow-up ASPECTS (Spearman correlation coefficient r =0.65; 95% CI, 0.58 to 0.72; P <0.001) than between noncontrast CT ASPECTS and follow-up CT ASPECTS ( r =0.46; 95% CI, 0.36 to 0.55; P <0.001). CT angiography source image ASPECTS correlated better with baseline National Institutes of Health Stroke Scale and 24-hour National Institutes of Health Stroke Scale when compared with noncontrast CT ASPECTS ( P <0.001). In an adjusted model including both CT angiography source image ASPECTS and noncontrast CT ASPECTS, CT angiography source image ASPECTS was associated with good outcome (OR, 2.30; 95%, CI, 1.16 to 4.53), whereas noncontrast CT ASPECTS was not (OR, 1.54; 95% CI, 0.84 to 2.82). Among imaging parameters, CT angiography source image ASPECTS was the only independent predictor of good outcome (OR, 2.29; 95% CI, 1.16 to 4.53).

Conclusions—

CT angiography source image ASPECTS correlates better with baseline stroke severity, is a better predictor of final infarct extension, and independently predicts neurological outcome than noncontrast CT ASPECTS.

CT Perfusion ASPECTS in the Evaluation of Acute Ischemic Stroke: Thrombolytic Therapy Perspective

Background and Purpose

Advances in the management of acute ischemic stroke and medical imaging are creating pressure to replace the rigid one-third middle cerebral artery (MCA) and non-contrast-enhanced CT (NCCT) Alberta Stroke Program Early CT Score (ASPECTS) thresholds used for the selection of patients eligible for intravenous thrombolytic therapy. The identification of potentially salvageable ischemic brain tissue lies at the core of this issue. In this study, the role of CT perfusion ASPECTS in the detection of reversible ischemia was analyzed.

Materials and Methods

We retrospectively reviewed the clinical and imaging data of 92 consecutive patients who received intravenous thrombolytic therapy for acute (duration <3 h) ischemic stroke. Most of the patients underwent admission multimodal CT, and all patients had follow-up NCCT at 24 h. ASPECTS was assigned to all modalities and correlated with clinical and imaging parameters. Receiver-operating characteristic curve analysis was performed to determine optimal thresholds for different parameters to predict clinical outcome.

Results

A perfusion defect could be detected in 50% of the patients. ASPECTS correlated inversely with the clinical outcome in the following order: follow-up NCCT > cerebral blood volume (CBV) > mean transit time (MTT) > admission NCCT. The follow-up NCCT and the CBV displayed a statistically significant difference from the admission NCCT, while the MTT did not reach statistical significance. The threshold that best differentiated between good and bad clinical outcome on admission was CBV ASPECTS ≥7. In patients with CT perfusion ASPECTS mismatch, MTT and CBV ASPECTS essentially provided the lower and upper limits for the follow-up NCCT ASPECTS, thus defining the spectrum of possible outcomes. Furthermore, CT perfusion ASPECTS mismatch strongly correlated (r = 0.83) with the mismatch between the tissue at risk and the final infarct, i.e. the amount of salvaged tissue. This finding suggests that the CT perfusion ASPECTS mismatch adequately identifies the amount of potentially salvageable ischemic brain tissue.

Conclusions

Parameters derived from the use of CT perfusion ASPECTS can detect reversible ischemia and are correlated with clinical outcome.