CT Angiography Source Images Research Articles

The relationship between bone health and type of intracranial internal carotid calcifications in patients with ischemic stroke

IntroductionVascular calcifications, primarily in the aorta and its proximal branches, are commonly observed among subjects with impaired bone health. In this study, we sought to determine if a comparable association holds true for the calcifications in the intracranial internal carotid arteries (IICA), in general and also for particular calcification patterns. MethodsA consecutive series of ischemic stroke patients were prospectively enrolled into the study, where computed tomography angiography source images were used to determine the presence and type of IICA calcifications, and dual-energy X-ray absorptiometry was used to determine the bone mineral density in the left femoral neck region. IICA calcifications were categorized as none, intimal, medial, and mixed types based on previously validated classification schemes. Their relationships with femoral bone T-scores were evaluated by bivariate and multivariate analyses. ResultsFemoral neck T-score was highest among patients without any vascular calcifications (n=65), when compared to the bone density measures among patients with any type of calcification (n=185) (p<0.001). After adjustment for age, gender, vascular risk factors, and serum biomarkers related to bone health, the T-score remained significantly associated only with the pattern of intimal calcification [OR 0.63 (0.42 – 0.95), p=0.028]. ConclusionsOur findings suggest that the intracranial vasculature, in particular the internal carotid arteries, is not immune to the interplay between suboptimal bone health and vascular calcifications. This association was most robust for an intimal type of IICA calcification pattern, while no such relationship could be demonstrated for other types of vascular calcifications.

Automated detection of early signs of irreversible ischemic change on CTA source images in patients with large vessel occlusion.

To create and validate an automated pipeline for detection of early signs of irreversible ischemic change from admission CTA in patients with large vessel occlusion (LVO) stroke. We retrospectively included 368 patients for training and 143 for external validation. All patients had anterior circulation LVO stroke, endovascular therapy with successful reperfusion, and follow-up diffusion-weighted imaging (DWI). We devised a pipeline to automatically segment Alberta Stroke Program Early CT Score (ASPECTS) regions and extracted their relative Hounsfield unit (rHU) values. We determined the optimal rHU cut points for prediction of final infarction in each ASPECT region, performed 10-fold cross-validation in the training set, and measured the performance via external validation in patients from another institute. We compared the model with an expert neuroradiologist for prediction of final infarct volume and poor functional outcome. We achieved a mean area under the receiver operating characteristic curve (AUC), accuracy, sensitivity, and specificity of 0.69±0.13, 0.69±0.09, 0.61±0.23, and 0.72±0.11 across all regions and folds in cross-validation. In the external validation cohort, we achieved a median [interquartile] AUC, accuracy, sensitivity, and specificity of 0.71 [0.68-0.72], 0.70 [0.68-0.73], 0.55 [0.50-0.63], and 0.74 [0.73-0.77], respectively. The rHU-based ASPECTS showed significant correlation with DWI-based ASPECTS (rS = 0.39, p<0.001) and final infarct volume (rS = -0.36, p<0.001). The AUC for predicting poor functional outcome was 0.66 (95%CI: 0.57-0.75). The predictive capabilities of rHU-based ASPECTS were not significantly different from the neuroradiologist's visual ASPECTS for either final infarct volume or functional outcome. Our study demonstrates the feasibility of an automated pipeline and predictive model based on relative HU attenuation of ASPECTS regions on baseline CTA and its non-inferior performance in predicting final infarction on post-stroke DWI compared to an expert human reader.

Association of Dual-Phase Computed Tomography Angiography and CT-Perfusion in Patients with Acute Ischemic Stroke Beyond the 6-Hour Window

Background: There is controversy regarding the need to use advanced imaging to select candidates for thrombectomy in late window acute ischemic stroke (AIS). Hypoattenuation on CT angiography source images (CTA-SI) in arterial phase has been shown to be more sensitive than Alberta Stroke Program Early CT score (ASPECTS) of brain parenchyma to determine tissue at risk of ischemia. Our hypothesis is that the addition of a second acquisition at 35-50 seconds could complement the assessment of hypoperfused tissue that fails to receive flow through pial vessels. Methods: Patients with large vessel occlusion and 6-16 hours from symptom onset, admitted between August 2019 and July 2022 were evaluated with dual-phase CT angiography (CTA) and CT-perfusion. The association between automated CT-perfusion values and dual-phase CTA was assessed through a correlation coefficient. Results: Pearson's coefficient demonstrated a high correlation between ischemic core volume and delayed CTA-SI with an inverse association of -0.91 and between Tmax≥6 sec volume and arterial CTA-SI with a value of -0.83. Conclusion: CTA-derived source images (CTA-SI) in two phases may be useful in the selection of patients with AIS presenting beyond the 6-hour window.

Combining generative modelling and semi-supervised domain adaptation for whole heart cardiovascular magnetic resonance angiography segmentation

BackgroundQuantification of three-dimensional (3D) cardiac anatomy is important for the evaluation of cardiovascular diseases. Changes in anatomy are indicative of remodeling processes as the heart tissue adapts to disease. Although robust segmentation methods exist for computed tomography angiography (CTA), few methods exist for whole-heart cardiovascular magnetic resonance angiograms (CMRA) which are more challenging due to variable contrast, lower signal to noise ratio and a limited amount of labeled data. MethodsTwo state-of-the-art unsupervised generative deep learning domain adaptation architectures, generative adversarial networks and variational auto-encoders, were applied to 3D whole heart segmentation of both conventional (n = 20) and high-resolution (n = 45) CMRA (target) images, given segmented CTA (source) images for training. An additional supervised loss function was implemented to improve performance given 10%, 20% and 30% segmented CMRA cases. A fully supervised nn-UNet trained on the given CMRA segmentations was used as the benchmark. ResultsThe addition of a small number of segmented CMRA training cases substantially improved performance in both generative architectures in both standard and high-resolution datasets. Compared with the nn-UNet benchmark, the generative methods showed substantially better performance in the case of limited labelled cases. On the standard CMRA dataset, an average 12% (adversarial method) and 10% (variational method) improvement in Dice score was obtained. ConclusionsUnsupervised domain-adaptation methods for CMRA segmentation can be boosted by the addition of a small number of supervised target training cases. When only few labelled cases are available, semi-supervised generative modelling is superior to supervised methods.

Abstract 5: Malignant Venous Outflow Profile Predicts Futile Recanalization After Endovascular Thrombectomy.

Objective: To explore the association of baseline venous outflow from the occluded cerebral territory and futile recanalization (FR) in patients with acute ischemic stroke due to large vessel occlusion (LVO) in the anterior circulation. Methods: Consecutive patients from a prospectively maintained stroke database were included in this study if they presented with a multimodal CT-confirmed LVO in the anterior circulation and underwent thrombectomy within 24 hours after stroke onset. Excellent recanalization of the occluded artery, defined as final mTICI 2c-3 on digital subtraction angiography, was considered to be futile if patients fail to achieve functional independence (modified Rankin Scale of 0-2) at 90 days. Baseline venous outflow profile was determined by a 7-point semi-quantitative scoring system which assessed ipsilateral venous opacification of the vein of Labbe, Trolard and superficial middle cerebral vein on single-phase CTA source images. Hypoperfusion intensity ratio (HIR, defined as delay time &gt;6 seconds/delay time &gt;3 seconds) was applied to evaluate tissue-level collateral status. Results: 145 patients met the inclusion criteria. Multivariable logistic regression analysis showed that malignant venous outflow (OR 4.30 [95% CI 1.41-14.57]; p =0.013) was independently associated with functional dependence regardless of age, glucose, HIR, early neurologic deterioration, hemorrhagic transformation and final infarct volume. FR was observed in 24/52 (46%) recanalized patients. Stepwise logistic regression revealed a poor venous outflow profile at presentation as an independent predictor of FR (OR 7.04 [95% CI 1.29-50.16]; p =0.03) adjusted for baseline NIH Stroke Scale score, HIR and presence of hemorrhagic transformation. Conclusion: A malignant venous outflow profile at baseline is associated with FR in patients with LVO. The mechanism by which poor venous outflow from the occluded territory hinders clinical recovery despite prompt successful thrombectomy remains to be determined.

Efficacy of 3D evaluation of unruptured paraclinoid aneurysms within Leksell GammaPlan® for determination of their intradural localization

BackgroundDetermination of the intradural unruptured paraclinoid aneurysm localization is difficult, but critical for selection of the optimal treatment strategy. ObjectiveTo assess efficacy of the three-dimensional (3D) evaluation of unruptured paraclinoid aneurysms within Leksell GammaPlan® (LGP; Elekta AB; Stockholm, Sweden) for determination of their intradural localization. MethodsOverall, 125 incidentally diagnosed unruptured paraclinoid aneurysms in 118 patients (mean age, 55 years) underwent 3D evaluation of their localization within LGP using post-contrast thin-slice constructive interference in steady state (CISS) images, which in 41 cases were additionally co-registered and fused with the axial computed tomography angiography (CTA) source images. ResultsAccording to the evaluation within LGP, paraclinoid aneurysms were considered intradural, transitional, and extradural in 75, 25, and 25 cases respectively. Overall, 51 of 75 aneurysms deemed to be intradural, underwent microsurgical management, and intraoperative visual inspection confirmed their intradural localization in 45 cases, whereas it was transitional in 3, and extradural in 3. If during preoperative 3D evaluation within LGP only post-contrast CISS images were used, prediction of the pure intradural localization of aneurysm was correct in 88 % of cases (95 % CI: 79–97 %), and of the pure or partial (i.e., transitional) intradural localization in 94 % of cases (95 % CI: 88–100 %), whereas it was 100 % if co-registration and fusion of the contrast-enhanced CISS and CTA source images was done. ConclusionIntradural localization of the unruptured paraclinoid aneurysms may be effectively predicted based on their 3D evaluation within LGP using post-contrast thin-slice CISS and CTA source images, which may help with clinical decision-making.

Predictive value of ischemia location on multimodal CT in thrombectomy-treated patients.

Alberta Stroke Program Early CT Score (ASPECTS) applied to CT-perfusion (CTP) and CT-angiography-source-images (CTA-SI) may improve outcome prediction in large vessel occlusion (LVO) stroke if compared to non-contrast CT (NCCT) alone. Besides, ischemia location may have enhanced capabilities, compared to ischemia volume alone, in predicting stroke outcomes. We aim to evaluate the association between ischemia location as measured by ASPECTS regions in NCCT, CTP maps and CTA-SI and 3 months outcome in patients with LVO treated with mechanical thrombectomy (MT). Consecutive patients with anterior circulation stroke treated with MT were recorded in a prospectively maintained database at a single center. Modified Rankin scale (mRS) at 3months >2 was considered a poor outcome. Association of patients' characteristics, NCCT, CTP, and CTA-SI parameters with outcome was evaluated using single-variable analysis and binary logistic regression multivariate analysis for each imaging technique. 177 patients were included. 115 (65%) patients reached a favorable outcome. The involvement of lenticular, caudate, M1, or M2 in all imaging techniques, insula in NCCT and CTA-SI and M5 in CBV maps and CTA-SI was related to functional outcome in bivariate analysis. However, in the multivariate analysis, none ischemia location was independently related to outcome, no matter the imaging technique studied. This finding remained unchanged when restricted to patients with good recanalization and when analyzing subpopulations according to hemisphere involvement or territories association. Our study suggests ischemia location shouldn't be used solely for decision-making in LVO stroke patients. Its predictive value may be taken in consideration together with other clinical and radiological variables.

Estimation of ischemic core in acute ischemic stroke with CT angiography and non-contrast CT: Attenuation changes in ASPECTS regions vs. automated ASPECTS scoring.

PurposeReperfusion therapies for acute ischemic stroke due to large-vessel occlusion (AIS-LVO) are highly time-dependent, and large infarction is related to poor outcomes and risk of symptomatic hemorrhage. It is of significance to investigate and optimize the screening means and selection criteria for reperfusion therapies to identify more appropriate patients with better outcomes. This study aimed to compare the performance of attenuation changes vs. automated Alberta Stroke Program Early CT Score (ASPECTS) and using CT angiography (CTA) source images vs. non-contrast CT (NCCT) in distinguishing the infarction extent of ischemic core volumes ≥ 70 ml within different time windows.MethodsA total of 73 patients with AIS-LVO who received multimodal CT were analyzed. The automated software was used to calculate ASPECTS. Attenuation change was defined as the sum of products of relative Hounsfield unit (rHU) values times weighting factors of all 10 ASPECTS regions. rHU value of each region was the HU of the ischemic side over that of the contralateral. The corresponding weighting factors were the regression coefficients derived from a multivariable linear regression model which was used to correlate regional rHU with ischemic core volumes, because each region in the ASPECTS template is weighted disproportionally in the ASPECTS system. Automated ASPECTS and attenuation changes were both calculated using CTA and NCCT, respectively.ResultsAttenuation changes were correlated with ischemic core volumes within different time windows (Rho ranging from 0.439 to 0.637). In classification of the ischemic core ≥ 70 ml, the performances of attenuation changes were comparable with ASPECTS (area under the curve [AUC] ranging from 0.799 to 0.891), with DeLong’s test (P = 0.079, P = 0.373); using CTA (AUC = 0.842) was not different from NCCT (AUC = 0.838).ConclusionAttenuation changes in ASPECTS regions were correlated with ischemic core volumes. In the classification of infarction volumes, attenuation changes had a high diagnostic ability comparable with automated ASPECTS. Measurement of attenuation changes is not involved in complicated scoring algorithms. This measurement can be used as an available, rapid, reliable, and accurate means to evaluate infarction extent within different time windows. The usefulness of infarction volumes measured by attenuation changes to identify more appropriate patients for reperfusion therapies can be validated in future clinical trials.

Postinterventional contrast accumulation early predicts malignant stroke in successfully recanalized patients with emergent large vessel occlusion

Background and objectiveA notable proportion of patients with emergent large vessel occlusion experience malignant middle cerebral infarct (MMI) despite successful recanalization with thrombectomy. In this study, we aim to identify early predictors of MMI in patients successfully recanalized by thrombectomy. MethodsWe retrospectively analyzed atotal of 144 anterior circulation emergent large vessel occlusion patients (90 males and 54 females; mean yr ± SD, 67.7 ± 13.2) who were successfully recanalized by thrombectomy (thrombolysis in cerebral infarction perfusion scale 2b or 3) in the cerebrovascular center of the Soonchunhyang University Bucheon Hospital in South Korea between January 2012 and September 2021. Using pretreatment CT angiography source images (CTA-SIs), collateral status was evaluated, and the Alberta stroke program early CT score (ASPECTS) was determined. Contrast accumulation (CA) was evaluated on non-contrast brain CT scans performed immediately after thrombectomy procedures. Logistic regression and receiver operating characteristic curve analyses were performed using SPSS software, version 26. ResultsNineteen patients (13.2 %, 10 males and 9 females; mean yr ± SD, 67.9 ± 11.3) experienced MMI. The collateral status was poorer (p < 0.001) and the CTA-SI ASPECTS was lower (p < 0.001) in the MMI group than in the non-MMI group. Furthermore, postinterventional CA was more frequent in the MMI group (94.7 % vs 65.6 %, p = 0.010). In particular, distribution of CA was different between the MMI and non-MMI groups. Cortical and subarachnoid CA was more frequent in the MMI group than in the non-MMI group (94.7 % vs 49.6 %, p < 0.001 and 89.5 % vs 20.8 %, p < 0.001). In addition, the ASPECTS for CA, wherein each region was scored 0 if CA existed, were lower in the MMI group (p < 0.001). Multivariate analysis showed that cortical CA, subarachnoid CA, and CA ASPECTS were associated with MMI. A CA ASPECTS ≤ 6 predicted MMI with a sensitivity of 94.7 % and a specificity of 77.6 % (area under the curve, 0.87). ConclusionsOur study shows that the MMI risk in successfully recanalized patients can be predicted by using a simple CT scan immediately after thrombectomy. A cortical or subarachnoid location of CA and lower CA ASPECTS can early predict the future occurrence of MMI.

Identifying 'fast progressors' likely to benefit from mechanical thrombectomy

ObjectivesAlthough the effect of mechanical thrombectomy in large vessel occlusions has been clearly demonstrated, there are different opinions about the treatment of patients with low ASPECT scores. We conducted this research to explore the utility of mechanical thrombectomy for the fast progressor patients. MethodsWe evaluated 394 patients with large vessel occlusion (LVO) who applied to our center between 2012 and 2020 retrospectively. Patients with posterior system stroke and who admitted 6 h after the onset of symptoms, were not included in the study. The remaining 256 patients were divided into two groups as computed tomography angiography source image Alberta stroke program early computer tomography score (CTA-SI ASPECT) ≤ 6 and > 6. Modified rankin scale (mRS) 0–2 defined as good clinical outcome. Thrombolysis in cerebral infarction (TICI) score 2c-3 was accepted as successful recanalization. ResultsThe mean age of the patients in the fast-progressive group (23.4%; n = 60) was 66.3 ± 11.6 years, whereas the mean age of the CTA-SI ASPECTS > 6 group (76.6%; n = 196) was 62.4 ± 12.8 years (p = 0.034) A statistically significant difference was found between the groups regarding 90-day mRS (p < 0.001). Whereas 61.7% of the patients with a CTA-SI ASPECTS > 6 had a 90-day mRS 0–2, this rate was 28.3% for patients with a CTA-SI ASPECTS ≤ 6. ConclusionAccording to our study, approximately 1/3 of patients with ASPECTS ≤ 6 benefit from mechanical thrombectomy. In this patient group, age emerged as a determinant of good clinical outcome.

ASPECTS as a clinical outcome marker for MCA infarction treated with thrombolytic therapy: Non-contrast CT versus CTA source images

Background &amp; Objective: Computed tomography angiography (CTA) in acute stroke has been widely used to demonstrate arterial occlusion. Alberta Stroke Program Early CT Score (ASPECTS) is used to detect early ischemic signs in non-contrast computed tomography (NCCT) in the middle cerebral artery region. We hypothesized that computed tomography angiography source image (CTA-SI) is superior to NCCT in predicting final infarct volume, 24 hour National Institutes of Health Stroke Scale (NIHSS) score and 90-day clinical outcome. Methods: Patients who had an acute ischemic stroke due to middle cerebral artery (MCA) occlusion and treated with tissue plasminogen activator (tPA) were retrospectively evaluated. ASPECTS was evaluated by two experienced stroke neurologists in acute NCCT, CTA-SI, and follow up imaging. The final ASPECTS was compared with the mean baseline ASPECTS of NCCT and CTA-SI. The relation of both scores with 24-hour NIHSS and clinical outcome was compared. The Modified Rankin Scale (mRS) was utilized to evaluate the 90-day outcomes. mRS score of 0-2 was considered a “good outcome”. Results: Fifty-three patients were evaluated. We observed a significant relation among CTA-SI ASPECTS and after treatment 24hr ASPECTS (y= -3.9 + 1.4 x; 95% CI, -7.6 to -0.2) (y= -26.04 + 3.5 x; CI, -41 to -10). The median baseline 24-hr NHISS was 6 (0 - 22). We found a better correlation between CTA-SI ASPECTS and 24-hr NHISS (y= 363.06 + -37.03 x; CI, -148 to 864) than between NCCT ASPECTS and 24h NHISS (y=529.80 + -62.55 x; CI, 180 - 829). Median 90 days mRS score was 2 (0 - 6). According to Deming regression analysis, the CTA-SI ASPECTS (y= 76.10 + -7.69 x; 95% CI, -36 to 188) was more consistent with the 90 day mRS compared to NCCT ASPECTS (y=149.86 + -17.67 x; 95% CI, 23 - 267) CTA-SI was superior in predicting 24hr NIHSS and day 90 mRS compared to NCCT ASPECTS. Conclusion: Prediction of CTA-SI ASPECTs is better than NCCT ASPECTs at 24hr NIHSS, 3-month mRS and final infarct size in acute ischemic stroke patients treated with tPA.

Posterior Circulation ASPECTS on CT Angiography Predicts Futile Recanalization of Endovascular Thrombectomy for Acute Basilar Artery Occlusion.

BackgroundAcute basilar artery occlusion (BAO) is the most potentially disastrous outcome and has a high risk of recurrence stroke in posterior circulation infarction (PCI). However, the rate of futile recanalization remains high despite successful recanalization. The objective of this study was to investigate 90 days functional outcomes among patients with BAO who underwent endovascular thrombectomy (EVT) and to identify the risk factors associated with futile recanalization.MethodsWe retrospectively analyzed 72 patients with acute BAO who received EVT from January 2018 to June 2021. CT angiography source images posterior circulation Acute Stroke Prognosis Early CT Score (CTA-SI pc-ASPECTS) evaluated the extensive hypoattenuation in patients with BAO. Futile recanalization defined an modified Rankin Scale (mRS) of 3-6 at 90 days despite a successful recanalization. Logistic regression analysis was performed to investigate the predictors of futile recanalization.ResultsOur sample included a total of 55 eligible patients. Patients with poor outcomes showed that the pc-ASPECTS score was lower in patients with poor outcomes than that in patients with good outcomes (P = 0.017). Longer time from symptoms onset-to-the puncture (P = 0.014) and elevation of leucocytes (P = 0.012) were associated with poor outcomes. The multivariable logistic analysis showed that pc-ASPECTS and onset-to-puncture time (OPT) were independent predictors of futile recanalization.ConclusionsThis study suggested that pc-ASPECTS and OPT are independent predictors of futile recanalization after EVT in patients with BAO. The lower pc-ASPECTS score and longer puncture time will have a poor clinical outcome.

Usefulness of multimodal CT pc-aspect calculation in infratentorial stroke

Routine examinations for the diagnosis of posterior circulation stroke include clinical assessment using the National Institutes of Health Stroke Scale (NIHSS) and brain imaging, generally, non-contrast brain CT; both of them proved to be unreliable on detection of infratentorial strokes. We tested the validity and the prognostic value of posterior circulation Alberta Stroke Program Early CT Score (pc-ASPECTS) in patients with posterior circulation stroke calculated on noncontrat CT (NCCT), CT-angiography source images (CTA) and CT-perfusion (CTP) images.

Total and regional ASPECT score for non-contrast CT, CT angiography, and CT perfusion: inter-rater agreement and its association with the final infarction in acute ischemic stroke patients.

Alberta Stroke Program Early Computed Tomography Score (ASPECTS) is a grading system to assess the extent and distribution of early ischemic changes. To assess inter-rater agreement for total and regional ASPECTS on non-contrast computed tomography (NCCT) images, CT angiography source images (CTA-SI), and CT-perfusion cerebral blood volume (CTP-CBV) maps, and their association with final infarction in patients with acute ischemic stroke (AIS). A total of 96 consecutive patients with AIS who underwent pre-treatment NCCT and CTP were retrospectively enrolled. CTA-SI was reconstructed using the raw data of CTP. Total and regional ASPECTS were assessed on baseline NCCT, CTA-SI, and CTP-CBV, and on follow-up NCCT or diffusion-weighted imaging. Follow-up ASPECTS served as the reference standard for final infarction. CTP-CBV demonstrated higher concordance for total ASPECTS (interclass correlation coefficient, 0.895 vs. 0.771 vs. 0.777) and regional ASPECTS in internal capsule, lentiform, caudate nuclei, M5 and M6, compared with NCCT and CTA-SI. CTP-CBV showed a trend of stronger correlation with final ASPECTS than NCCT and CTA-SI (0.717 vs. 0.711 vs. 0.565; P > 0.05). ASPECTS in the internal capsule (ρ, 0.756 vs. 0.556; P = 0.016) and caudate nucleus (ρ, 0.717 vs. 0.476; P = 0.010) on CTP-CBV were more strongly correlated with follow-up ASPECTS than NCCT. CTP-CBV showed higher accuracy for predicting final infarction in the internal capsule (92.5% vs. 90.3% and 87.1%; P > 1.000, P = 0.125, respectively) and caudate nucleus (87.1% vs. 79.6% and 77.4%; P = 0.453, P = 0.039, respectively) than CTA-SI and NCCT. CTP-CBV ASPECTS might be more reliable for delineating early ischemic changes and predicting final infarction.

Automated prediction of final infarct volume in patients with large-vessel occlusion acute ischemic stroke.

In patients with large-vessel occlusion (LVO) acute ischemic stroke (AIS), determinations of infarct size play a key role in the identification of candidates for endovascular stroke therapy (EVT). An accurate, automated method to quantify infarct at the time of presentation using widely available imaging modalities would improve screening for EVT. Here, the authors aimed to compare the performance of three measures of infarct core at presentation, including an automated method using machine learning. Patients with LVO AIS who underwent successful EVT at four comprehensive stroke centers were identified. Patients were included if they underwent concurrent noncontrast head CT (NCHCT), CT angiography (CTA), and CT perfusion (CTP) with Rapid imaging at the time of presentation, and MRI 24 to 48 hours after reperfusion. NCHCT scans were analyzed using the Alberta Stroke Program Early CT Score (ASPECTS) graded by neuroradiology or neurology expert readers. CTA source images were analyzed using a previously described machine learning model named DeepSymNet (DSN). Final infarct volume (FIV) was determined from diffusion-weighted MRI sequences using manual segmentation. The primary outcome was the performance of the three infarct core measurements (NCHCT-ASPECTS, CTA with DSN, and CTP-Rapid) to predict FIV, which was measured using area under the receiver operating characteristic (ROC) curve (AUC) analysis. Among 76 patients with LVO AIS who underwent EVT and met inclusion criteria, the median age was 67 years (IQR 54-76 years), 45% were female, and 37% were White. The median National Institutes of Health Stroke Scale score was 16 (IQR 12-22), and the median NCHCT-ASPECTS on presentation was 8 (IQR 7-8). The median time between when the patient was last known to be well and arrival was 156 minutes (IQR 73-303 minutes), and between NCHCT/CTA/CTP to groin puncture was 73 minutes (IQR 54-81 minutes). The AUC was obtained at three different cutoff points: 10 ml, 30 ml, and 50 ml FIV. At the 50-ml FIV cutoff, the AUC of ASPECTS was 0.74; of CTP core volume, 0.72; and of DSN, 0.82. Differences in AUCs for the three predictors were not significant for the three FIV cutoffs. In a cohort of patients with LVO AIS in whom reperfusion was achieved, determinations of infarct core at presentation by NCHCT-ASPECTS and a machine learning model analyzing CTA source images were equivalent to CTP in predicting FIV. These findings have suggested that the information to accurately predict infarct core in patients with LVO AIS was present in conventional imaging modalities (NCHCT and CTA) and accessible by machine learning methods.

Abstract P330: Optimizing Predictions of Infarct Core Using Machine Learning

Introduction: Evaluation of infarct core by advanced neuroimaging has facilitated patient selection for endovascular stroke therapy (EST), however the accuracy of machine-learning analysis compared to these modalities remains unexplored. We test the performance of computed tomography-Alberta Stroke Program Early Computed Tomography Score (CT- ASPECTS) vs. Computed Tomography Perfusion (CTP)-RAPID, vs. an extension of our novel machine-learning model, Deep Symmetry-sensitive Network (DeepSymNet [ref]), using the final infarct volume (FIV) in patients with rapid and successful endovascular reperfusion as the gold standard. Methods and Materials: We identified consecutive patients with large vessel occlusion acute ischemic stroke that underwent EST with TICI 2b/3 reperfusion. FIV was determined by volumetric measurements on 24-48h DWI MRI. The DeepSymNet algorithm combines symmetric and absolute brain representations and had been trained to predict CTP-RAPID core size from CTA source images acquired at presentation. Performance at predicting FIV was determined by Pearson’s correlation for CT- ASPECTS, CTP-RAPID, and DeepSymNet. Data are presented as median [IQR]. Results: Among the 76 patients that met inclusion criteria, 55.2% were male, the median age was 68 years [54-77], and 32.8% were White. 71% of the patients demonstrated an MCA occlusion, and 55% of all occlusions were left-sided. Median ASPECTS on presentation was 8 [7-8.5] and the median FIV was 10 mL [2-37]. ASPECTS, CTP-RAPID and DeepSymNet all correlated with FIV, with comparable performances from ASPECTS (R 2 =-0.398) and CTP-RAPID (R 2 =0.403) and superior performance by DeepSymNet (R 2 =-0.606)(Table). Conclusions: The DeepSymNet machine learning model analyzing CTA source images demonstrated superior performance to ASPECTS and CTP-RAPID in FIV prediction. These findings suggest machine learning models may provide improved predictions of infarct core and selection for EST.

Abstract P573: The Interplay Between Mineral and Skeletal Metabolism Biomarkers and Intracranial Internal Carotid Artery Calcifications in Stroke Patients

Background: Intracranial internal carotid artery calcifications (IICAC), considered a phenomenon within the spectrum of atherosclerosis and vascular aging, are frequently encountered in ischemic stroke patients. While intimal IICAC directly contributes to ischemic stroke pathophysiology, the medial counterpart is generally deemed as a risk factor for vascular end-points. Apart from aging and cardiovascular risk factors, the underlying pathophysiology that contributes to development of IICAC is not well understood; herein we studied the interplay between mineral and skeletal metabolism biomarkers, and IICAC presence and pattern. Methods: In a prospective series of 194 ischemic stroke patients (mean±SD age: 69±14 yr), blood samples were collected to determine calcium, phosphorus, magnesium, osteocalcin, parathyroid hormone, and vitamin D levels within 72 hours of symptom onset. IICAC presence and type was determined on admission CT-angiography source images; a medial or intimal type of IICAC category was assigned according to Kockelkoren criteria. Results: A total of 45 (23%) patients had no calcifications, while 95 (49%) had an intimal pattern and 54 (28%) had non-intimal (or medial) pattern. Apart from the well-known factors related with IICAC, such as age, lower glomerular filtration rate (GFR), history of hypertension, diabetes mellitus, coronary artery disease and atrial fibrillation, we identified admission magnesium levels to be associated with IICAC presence and pattern (no calcification: 1.96±0.18 mEq/L, intimal calcification 1.93±0.19 mEq/L, medial calcification: 1.81±0.28 mEq/L; p=0.006). None of the other biomarkers had any significant relationship to IICAC. In multivariate models, a lower magnesium level was significantly associated with medial calcification (each 0.1 mEq/L drop increased the odds by 1.2 (95% CI 1.0-1.4; p=0.046)), in addition to older age, history of diabetes mellitus and lower GFR. Conclusion: Hypomagnesemia is one of the factors well-known to be associated with vascular calcifications in the body. Our findings, extend this relationship to the intracranial vascular bed. No similar association was observed for other biomarkers related to mineral and skeletal metabolism. (Funding: TUBITAK grant 218S753)

Correlation of Alberta Stroke Program Early Computed Tomography Score With Computed Tomography Perfusion Core in Large Vessel Occlusion in Delayed Time Windows.

The Alberta Stroke Program Early Computed Tomography (CT) Score (ASPECTS) and CT perfusion (CTP) are commonly used to predict the ischemic core in acute ischemic strokes. CT angiography source images (CTA-SI) can also provide additional information to identify the extent of ischemia. Our objective was to investigate the correlation of noncontrast CT (NCCT) ASPECTS and CTA-SI ASPECTS with CTP core volumes. We utilized a single institutional, retrospective registry of consecutive patients with acute ischemic stroke with large vessel occlusion between May 2016 and May 2018. We graded ASPECTS both on baseline NCCT and CTA-SI and measured CTP core using automated RAPID software (cerebral blood flow <30%). We used Spearman's correlation coefficients to evaluate the correlation between continuous variables. A total of 52 patients fit the inclusion criteria of large vessel occlusion in 6 to 24 hours and baseline imaging work up of NCCT, CTA, and CTP. The median age was 63 (interquartile range=53.5-75) and 38.46% were female. The median NCCT ASPECTS was 7 (interquartile range=6-9), CTA-SI ASPECTS was 5 (interquartile range=4-7), and CTP core was 14.5 mL (interquartile range=0-46 mL). There was a moderate correlation between NCCT ASPECTS and CTP core (rs=-0.55, P<0.0001) and between CTA-SI ASPECTS and CTP core (rs=-0.50, P=0.0002). The optimal NCCT ASPECTS cutoff score to detect CTP core ≤70 mL was ≥6 (sensitivity, 0.84; specificity, 0.57; positive predictive value, 0.93; negative predictive value, 0.36) and the optimal CTA-SI ASPECTS was ≥5 (sensitivity, 0.76; specificity, 0.71; positive predictive value, 0.94; negative predictive value, 0.31). There was a moderate correlation between NCCT and CTA-SI ASPECTS in predicting CTP defined ischemic core in delayed time windows. Further studies are needed to determine if NCCT and CTA imaging could be used for image-based patient selection when CTP imaging is not available.

Performance of Automated Attenuation Measurements at Identifying Large Vessel Occlusion Stroke on CT Angiography

PurposeComputed tomography angiography (CTA) is routinely used to detect large-vessel occlusion (LVO) in patients with suspected acute ischemic stroke; however, visual analysis is time consuming and prone to error. To evaluate solutions to support imaging triage, we tested performance of automated analysis of CTA source images (CTASI) at identifying patients with LVO.MethodsStroke patients with LVO were selected from a prospectively acquired cohort. A control group was selected from consecutive patients with clinically suspected stroke without signs of ischemia on CT perfusion (CTP) or infarct on follow-up. Software-based automated segmentation and Hounsfield unit (HU) measurements were performed on CTASI for all regions of the Alberta Stroke Program Early CT score (ASPECTS). We derived different parameters from raw measurements and analyzed their performance to identify patients with LVO using receiver operating characteristic curve analysis.ResultsThe retrospective analysis included 145 patients, 79 patients with LVO stroke and 66 patients without stroke. The parameters hemispheric asymmetry ratio (AR), ratio between highest and lowest regional AR and M2-territory AR produced area under the curve (AUC) values from 0.95–0.97 (all p < 0.001) for detecting presence of LVO in the total population. Resulting sensitivity (sens)/specificity (spec) defined by the Youden index were 0.87/0.97–0.99. Maximum sens/spec defined by the specificity threshold ≥0.70 were 0.91–0.96/0.77–0.83. Performance in a small number of patients with isolated M2 occlusion was lower (AUC: 0.72–0.85).ConclusionAutomated attenuation measurements on CTASI identify proximal LVO stroke patients with high sensitivity and specificity. This technique can aid in accurate and timely patient selection for thrombectomy, especially in primary stroke centers without CTP capacity.

ASPECTS Scoring Applied to CTA Source Images is Predictive of Final Infarct Volume and Good Functional Recovery (4602)

ASPECTS Scoring Applied to CTA Source Images is Predictive of Final Infarct Volume and Good Functional Recovery (4602)