CT Angiography Source Images Research Articles

Abstract TP74: Aspects Scoring Applied to CTA Source Images is Predictive of Final Infarct Volume and Good Functional Outcome

Introduction: CTP and MRI are increasingly used to assess endovascular thrombectomy (EVT) candidacy in large vessel occlusion stroke. Unfortunately, availability of these advanced neuroimaging techniques is not widespread and this can lead to over-triage to EVT-capable centers. Hypothesis: ASPECTS scoring applied to computed tomography angiography source images (CTA-SI) will be predictive of final infarct volume (FIV) and functional outcome. Methods: We reviewed data from consecutive patients undergoing EVT at our institution for anterior circulation occlusion between 01/14 - 01/19. We recorded demographics, comorbidities, NIHSS, treatment time parameters, and outcomes as defined by mRS (0-2 = good outcome). Cerebrovascular images were assessed by outcome-blinded raters and collateral score, TICI score, FIV, and both CT and CTA-SI ASPECTS scores were noted. Patients were grouped by ASPECTS score into low (0-4), intermediate (5-7), and high (8-10) for some analyses. FIV was predicted using a linear regression with NIHSS, good reperfusion (TICI 2b/3), collateral score, CT to groin puncture, CT and CTA-SI ASPECTS as independent variables. After excluding those with baseline mRS≥2, a binary logistic regression was performed including covariates of age, NIHSS, good reperfusion, and diabetes (factors significant at p<0.05 on univariate analysis) to assess the impact of CTA-SI ASPECTS group on outcome. Results: Analysis included 137 patients for FIV and 102 for outcome analysis (35 excluded for baseline mRS≥ 2). Linear regression found CTA-SI ASPECTS (Beta -10.8, p=0.002), collateral score (Beta -42.9, p=0.001) and good reperfusion (Beta 72.605, p=0.000) were independent predictors of FIV. Relative to the low CTA-SI ASPECTS group, the high CTA-SI ASPECTS group was more likely to have good outcome (OR 3.75 [95% CI 1.05-13.3]; p=0.41). CT ASPECTS was not predictive of FIV or good outcome. Outcomes: In those undergoing EVT for anterior circulation occlusion, CTA-SI ASPECTS is predictive of both FIV and functional outcome, while CT ASPECTS predicts neither. CTA-SI ASPECTS holds promise as a lower-cost, more widely available option for triage of patients with large vessel occlusion. Further study is needed comparing CTA-SI ASPECTS to CTP parameters.

Abstract WP76: Artificial Intelligence CTA Vessel Density Mapping to Enhance Identification of Large Vessel Occlusions in Mobile Stroke Unit

Background: Equipped with CT scanners capable of imaging the brain parenchyma and vasculature, Mobile Stroke Units (MSU) have the ability to image, diagnose and treat stroke patients in the prehospital setting. Automated CTA vessel density mapping could enhance frontline neurologist scan review in identifying large vessel occlusion (LVO), ensuring appropriate patient diagnosis and routing. Methods: We analyzed consecutive acute ischemic stroke patients undergoing CTA imaging in a regional Mobile Stroke Unit. Automated CTA vessel density mapping was performed in the field immediately after scan completion. CTA source images were wirelessly transferred to an off-site processing server (RAPID.Ai, IschemiaView) for artery reconstruction and color-coded density mapping, with blue, green, yellow, and red color shading indicating vessel density decreases of 70%-85%, 60%-75%, 45%-60%, and <45%. Results: Among all 16 patients, median processing time was 186 secs, and all images were available in time to aid clinical decision-making. Overall, automated processing yielded evaluable images in 94% (suboptimal contrast opacification precluded analysis of 1). Of the 15 diagnostically adequate exams, 100% (15/15) showed concordance for identification of anterior circulation occluded/abnormal vessel territories between automated CTA vessel density mapping and expert physician final CTA interpretation. Cases included true positives in 7, and true negatives in 8. Among true positives, CTA vessel density mapping identified the symptomatic occlusion in 6/6 and also correctly identified a severe cervical ICA stenosis unrelated to the clinical presentation in 1/1. Correctly detected intracranial occlusions included: ICA-17%. M1-17%, M1-M2 junction-17%, and M2-50%. Degree of vessel density diminution correlated with proximal-distal occlusion location. Conclusion: CTA vessel density mapping can feasibly and efficiently be conducted in Mobile Stroke Units and shows high accuracy in detection of large and medium intracranial vessel occlusions. Extension of mapping to the intracranial posterior circulation and algorithmic adjustment for proximal cervical stenoses/occlusions would further improve utility in aiding prehospital routing.

Collateral score on CT angiography in patients with acute ischemic stroke - A retrospective study

Objective: Clinically assessing the status of cerebral collaterals is thought to provide invaluable diagnostic and prognostic data in managing acute ischemic stroke (AIS) patients. In this study we present a report, based on commonly used collateral grading system, assessing the correlation between the collateral status seen on CT angiography and patients’ functional outcome at Day 90 in our institution. Method: Patients presenting to the Emergency Department within 6 hours of onset of stroke from January 2010 until December 2014 were chosen for the study. CT angiography source images were retrospectively reviewed and given a “collateral score” (CS) by a radiologist who was blinded to the patient’s clinical information on presentation, as well as the clinical outcomes at 90 days. Patients’ mRS score at 90 days was obtained retrospectively and compared against the “collateral score”. Results: 87 patients were enrolled into this study, of which 60 (69%) were male and 27 (31%) were female with a mean age of 60.3 years. In this study, 56 (64.4%) patients had a collateral score (CS) > 2 and 31 (35.6%) patients had a CS < 2. Out of 56 patients who had a CS > 2, 51 of them (91%) had good clinical outcome with a mRS < 2. All the patients who had CS < 2 showed poor clinical outcome with a mRS > 2. The collateral score predicts accurately the clinical outcome with an area under the curve (ROC) of 0.75 (95% CI, 0.675-0.871, P=0.001). There is significant Spearman correlation between CS and the clinical outcome at Day 90, in patients with AIS during CTA analysis. Conclusion: Our data supports the potential use of CS analysis in predicting clinical outcome of patients with AIS. Nevertheless, further study on a larger scale is strongly suggested to verify the reliability and reproducibility of CS assessment in CTA analysis prior to reperfusion in AIS patients.

Collateral score on CT angiography in patients with acute ischemic stroke - A retrospective study.

Objective: Clinically assessing the status of cerebral collaterals is thought to provide invaluable diagnostic and prognostic data in managing acute ischemic stroke (AIS) patients. In this study we present a report, based on commonly used collateral grading system, assessing the correlation between the collateral status seen on CT angiography and patients’ functional outcome at Day 90 in our institution. Method: Patients presenting to the Emergency Department within 6 hours of onset of stroke from January 2010 until December 2014 were chosen for the study. CT angiography source images were retrospectively reviewed and given a “collateral score” (CS) by a radiologist who was blinded to the patient’s clinical information on presentation, as well as the clinical outcomes at 90 days. Patients’ mRS score at 90 days was obtained retrospectively and compared against the “collateral score”. Results: 87 patients were enrolled into this study, of which 60 (69%) were male and 27 (31%) were female with a mean age of 60.3 years. In this study, 56 (64.4%) patients had a collateral score (CS) ? 2 and 31 (35.6%) patients had a CS < 2. Out of 56 patients who had a CS ? 2, 51 of them (91%) had good clinical outcome with a mRS ? 2. All the patients who had CS < 2 showed poor clinical outcome with a mRS > 2. The collateral score predicts accurately the clinical outcome with an area under the curve (ROC) of 0.75 (95% CI, 0.675-0.871, P=0.001). There is significant Spearman correlation between CS and the clinical outcome at Day 90, in patients with AIS during CTA analysis. Conclusion: Our data supports the potential use of CS analysis in predicting clinical outcome of patients with AIS. Nevertheless, further study on a larger scale is strongly suggested to verify the reliability and reproducibility of CS assessment in CTA analysis prior to reperfusion in AIS patients.

Eliminating vascular interference from the Spot Sign contributes to predicting hematoma expansion in individuals with spontaneous cerebral hemorrhages.

The computed tomography angiography (CTA) Spot Sign is an effective means of predicting hematoma expansion (HE) in the context of spontaneous intracerebral hemorrhage (ICH). We investigated whether continuous CTA source images could differentiate the Spot Sign and blood vessels in the hematoma, and whether it would improve Spot Sign accuracy as an HE predictor. We screened for the presence of CTA Spot Sign in individuals affected by spontaneous ICH within 24h of symptom development. Based on our findings, we determined the sensitivity, specificity, and positive/negative predictive values of this sign as a predictor of HE both on its own and following the exclusion of blood vessels. In addition, a receiver-operating characteristic approach was used to assess the accuracy of Spot Sign with and without elimination of vascular interference. A total of 265 patients were included in this study. The Spot Sign was observed in 100 patients, including in 29 patients wherein it was confirmed to be blood vessels as determined based upon continuous CTA source images. With respect to predicting HE, Spot Sign sensitivity, specificity, positive predictive values, and negative predictive values were 57%, 71%, 48% and 78%, respectively. Following the exclusion of blood vessels, these values were 57%, 87%, 68% and 81%, respectively. Spot Sign area under the curve after excluding blood vessels was 0.718, which was higher than that of the Spot Sign (0.638). After continuous CTA, source images are used to exclude blood vessels in the hematoma, the Spot Sign is thus more accurate in predicting HE.

The role of ASPECTs in patient selection for endovascular therapy – CTA source images versus noncontrast CT

The Alberta Stroke Program Early Computed Tomography Score (ASPECTs) on noncontrast CT (NCCT) is widely used for the decision of endovascular therapy (ET) in randomized controlled trials. CT angiography source images (CTA-SI) is another method to evaluate ischemic brain damage. We aimed to evaluate the association between pretreatment ASPECTs on CTA-SI and post-treatment clinical and radiological outcomes in acute stroke patients treated with ET. The association between both scores along with final infarct and outcome were analyzed. A total of 90 patients with successful recanalization were included in the study. The mean age was 59 ± 11.8. According to the results, CTA-SI ASPECTs was better correlated with final infarct than NCCT ASPECTs (p < 0.001). In univariate analyzes, factors associated with good outcome were age, baseline NIHSS score, and presence of diabetes mellitus (p = 0.001, p = 0.002, p = 0.034, respectively). On the other hand, when an analysis differentiating patients by age was performed, 40 patients below 60 years of age had significantly better outcomes despite having higher baseline NIHSS scores (p = 0.002). Finally, in multivariate analyzes, only age and baseline NIHSS score were found to be independent predictors of good outcome (p = 0.003 for both). In conclusion, CTA-SI ASPECTs in patient selection for ET seems to be more useful than NCCT ASPECTs. However, both scoring modalities were not found to be independent predictors of good outcome. Outcomes are changeable for the younger population who could continue their lives with mild or no deficits despite having a relatively low initial ASPECTs.

Incremental Value of Computed Tomography Perfusion for Final Infarct Prediction in Acute Ischemic Cerebellar Stroke.

BackgroundThe diagnosis of ischemic cerebellar stroke is challenging because of nonspecific symptoms and very limited accuracy of commonly applied computed tomography (CT) imaging. Advances in CT perfusion imaging provide increasing value in the detection of posterior circulation stroke, but the prognostic value remains unclear. We aimed to identify imaging parameters that predict morphologic outcome in cerebellar stroke patients using advanced CT including whole‐brain CT perfusion (WB‐CTP).Methods and ResultsWe selected all subjects with cerebellar WB‐CTP perfusion deficits and follow‐up‐confirmed cerebellar infarction from a consecutive cohort with suspected stroke who underwent WB‐CTP. Posterior‐circulation‐Acute‐Stroke‐Prognosis‐Early‐CT‐Score (pc‐ASPECTS) was determined on noncontrast CT, CT angiography source images, and on parametric WB‐CTP maps. Cerebellar perfusion deficit volumes on all maps and the final infarction volume on follow‐up imaging were quantified. Uni‐ and multivariate regression analyses were performed. Sixty patients fulfilled the inclusion criteria. pc‐ASPECTS on CT angiography source images (ß, −9.239; 95% CI, −14.220 to −4.259; P<0.001) and cerebral blood flow deficit volume (ß, 0.886; 95% CI, 0.684 to 1.089; P<0.001) were significantly associated with final infarction volume in univariate linear regression analysis. The association of cerebral blood flow deficit volume (ß, 0.830; 95% CI, 0.605–1.055; P<0.001) was confirmed in a multivariate linear regression model adjusted for age, sex, pc‐ASPECTS on noncontrast CT, and CT angiography source images and the National Institutes of Health Stroke Scale score on admission. No other clinical or imaging parameters were associated with cerebellar stroke final infarction volume (P>0.05).ConclusionsIn contrast to noncontrast CT and CT angiography, WB‐CTP imaging contains prognostic information for morphologic outcome in patients with acute cerebellar stroke.

Computational fluid dynamics methods applied to intracranial stenosis imaging

Stenosis of the major intracranial arteries is an important cause of stroke, accounting for 8-10% of ischemic strokes in US. It was demonstrated that Computational Fluid Dynamics modelling may be a promising technique in evaluating and understanding the hemodynamic characteristics of ICAS lesions. It has not ever been evaluated if the results from CFD analysis of CTA and DSA source images correlate. This retrospective study evaluated 80 patients with symptomatic ICAS lesions treated at Tiantan Hospital in Beijing. The Vascular Modelling Toolkit software was used to generate 3D models from CTA source images. 3D reconstructions were generated from DSA images using Coronary3D software. Blood flow simulation was performed on both DSA and CTA generated meshes using ANSYS FLUENT SOLVER (ANSYS Inc.). A two-sample t test for paired data was used to compare the pressure and velocity measurements. CTA and DSA imaging were evaluated for 20 patients with symptomatic ICAS. Although faint signals and convoluted vasculature in 60 DSA scans prevented 3D reconstruction and excluded these cases from the study. When it was plotted the change in pressures of CTA versus the change in pressures of DSA R2 was 0.001; meaning that the linear model explains almost none of the variability in between the data in terms of changes in velocity and pressure. It was found no noticeable correlation between the information regarding pressure and velocity as given by DSA and by CTA. Therefore, we could not say that the information from DSA is on par with that of CTA.

Multimodal CT in Acute Stroke.

Multimodal CT imaging (non-contrast CT, NCCT; CT angiography, CTA; and CT Perfusion, CTP) is central to acute ischemic stroke diagnosis and treatment. We reviewed the purpose and interpretation of each component of multimodal CT, as well as the evidence for use in routine care. Acute stroke thrombolysis can be administered immediately following NCCT in acute ischemic stroke patients assessed within 4.5h of symptom onset. Definitive identification of a large vessel occlusion (LVO) requires vascular imaging, which is easily achieved with CTA. This is critical, as the standard of care for LVO within 6h of onset is now endovascular thrombectomy (EVT). CTA source images can also be used to estimate the efficacy of collateral flow in LVO patients. The final component (CTP) permits a more accurate assessment of the extent of the ischemic penumbra. Complete multimodal CT, including objective penumbral measurement with CTP, has been used to extend the EVT window to 24h. There is also randomized controlled trial evidence for extension of the IV thrombolysis window to 9h with multimodal CT. Although there have been attempts to assess for responders to reperfusion strategies beyond 6h ("late window") using collateral grades, the only evidence for treatment of this group of patients is based on selection using multimodal CT including CTP. The development of fully automated software providing quantitative ischemic penumbral and core volumes has facilitated the adoption of CTP and complete multimodal CT into routine clinical use. Multimodal CT is a powerful imaging algorithm that is central to current ischemic stroke patient care.

Value of Posterior circulation ASPECTS and Pons-Midbrain Index on non-contrast CT and CT Angiography Source Images in patients with basilar artery occlusion recanalized after mechanical thrombectomy

PurposeEndovascular treatment with mechanical thrombectomy devices demonstrated high recanalization rates but functional outcome did not correlate with high rates of recanalization obtained. Patient selection prior to the endovascular treatment is very important in the final outcome of the patient. The primary aim of our study was to evaluate the prognostic value of posterior circulation Alberta Stroke Program Early CT Score (pc-ASPECTS) and Pons-Midbrain Index (PMI) scores in patients with Basilar Artery Occlusion (BAO) treated with successful angiographic recanalization after mechanical thrombectomy. MethodsRetrospective single-centre study including 18 patients between 2008 and 2013 who had acute basilar artery occlusion managed with endovascular treatment within 24h from symptoms onset and with successful angiographic recanalization. The patients were initially classified into two groups according to clinical outcome and mortality at 90 days. For analysis we also divided patients into groups based on pc-ASPECTS (≥8 vs. <8) and PMI (≥3 vs. <3) on non-contrast CT (NCCT) and CT Angiography Source Images (CTASI). Imaging data were correlated to clinical outcome and mortality rate. ResultsCTASI pc-ASPECTS, dichotomized at <8 versus ≥8, was associated with a favourable outcome (RR: 2.6; 95% CI: 1.3–5.2) and a reduced risk of death (RR: 6.5: 95% CI: 7.8–23.3). All patients that survived and were functionally independent had pc-ASPECTS score ≥8. None of the 5 patients with CTASI pc-ASPECTS score less than 8 survived. ConclusionPC-ASPECTS on CTASI is helpful for predicting functional outcome after BAO recanalization with endovascular treatment. These results should be validated in a randomised controlled trial in order to decide whether or not to treat a patient with BAO.

3D convolutional neural networks applied to CT angiography in the detection of acute ischemic stroke

BackgroundThe aim of this study was to investigate the feasibility of ischemic stroke detection from computed tomography angiography source images (CTA-SI) using three-dimensional convolutional neural networks.MethodsCTA-SI of 60 patients with a suspected acute ischemic stroke of the middle cerebral artery were randomly selected for this study; 30 patients were used in the neural network training, and the subsequent testing was performed using the remaining 30 patients. The training and testing were based on manually segmented lesions. Cerebral hemispheric comparison CTA and non-contrast computed tomography (NCCT) were studied as additional input features.ResultsAll ischemic lesions in the testing data were correctly lateralized, and a high correspondence to manual segmentations was achieved. Patients with a diagnosed stroke had clinically relevant regions labeled infarcted with a 0.93 sensitivity and 0.82 specificity. The highest achieved voxel-wise area under receiver operating characteristic curve was 0.93, and the highest Dice similarity coefficient was 0.61. When cerebral hemispheric comparison was used as an input feature, the algorithm performance improved. Only a slight effect was seen when NCCT was included.ConclusionThe results support the hypothesis that an acute ischemic stroke lesion can be detected with 3D convolutional neural network-based software from CTA-SI. Utilizing information from the contralateral hemisphere appears to be beneficial for reducing false positive findings.

Abstract WP161: Computational Fluid Dynamics Using SAMMPRIS CT Angiography Quantifies Pro-Atherogenic Shear Stress Linked With Post-Stenotic Flow Vortices

Background: Low wall shear stress (LSS) is an established cause of pro-atherogenic endothelial pathophysiology, yet it has never been demonstrated in the cerebral circulation affected by intracranial atherosclerotic disease (ICAD). Noninvasive CT angiography (CTA) computational fluid dynamics (CFD) enables high-resolution investigation of detailed post-stenotic phenomena. We used all available CTA data in the SAMMPRIS trial of ICAD to detect and quantify post-stenotic LSS. Methods: CTA source images from SAMMPRIS were reconstructed in 3D followed by geometry refinements to generate a mesh of the diseased arterial lesion and adjacent segments. CFD was performed with Ansys (ICEM, Fluent), applying reference boundary conditions with k-omega turbulence and non-Newtonian modeling of the traversing blood viscosity. 3D CFD parameter maps illustrated velocity, velocity swirling and corresponding wall shear stress. Results: 144 subjects enrolled in SAMMPRIS had CTA at baseline, including 140 with CTA source images enabling CFD. Post-stenotic velocity profiles revealed vortices in all cases, quantified by swirling and turbulent kinetic energy. These luminal flow changes were adjacent to focal regions of LSS in the post-stenotic region (Figure). Conclusions: Low wall shear stress is associated with vortices of fluid flow in CTA CFD modeling of ICAD from SAMMPRIS. CTA source images may be used to noninvasively quantify LSS and model this pro-atherogenic factor in ICAD across a wide variety of lesions. Future studies should examine the related endothelial biology and potential link with plaque evolution.

Valor de la escala ASPECTS de circulación posterior y del índice puente-mesencéfalo en imágenes de TC sin contraste y angiografía por TC en pacientes con oclusiones de la arteria basilar recanalizados tras trombectomía mecánica

PurposeEndovascular treatment with mechanical thrombectomy devices demonstrated high recanalization rates but functional outcome did not correlate with high rates of recanalization obtained. Patient selection prior to the endovascular treatment is very important in the final outcome of the patient. The primary aim of our study was to evaluate the prognostic value of posterior circulation Alberta Stroke Program Early CT Score (pc-ASPECTS) and Pons-Midbrain Index (PMI) scores in patients with Basilar Artery Occlusion (BAO) treated with successful angiographic recanalization after mechanical thrombectomy. MethodsRetrospective single-center study including 18 patients between 2008 and 2013 who had acute basilar artery occlusion managed with endovascular treatment within 24hours from symptoms onset and with successful angiographic recanalization. The patients were initially classified into two groups according to clinical outcome and mortality at 90 days. For analysis we also divided patients into groups based on pc-ASPECTS (≥8vs.<8) and PMI (≥3vs.<3) on non-contrast CT (NCCT) and CT Angiography Source Images (CTASI). Imaging data were correlated to clinical outcome and mortality rate. ResultsCTASI pc-ASPECTS, dichotomized at <8 versus≥8, was associated with a favorable outcome (RR: 2.6; 95% CI: 1.3-5.2) and a reduced risk of death (RR: 6.5: 95% CI: 7.8-23.3). All patients that survived and were functionally independent had pc-ASPECTS score≥8. None of the 5 patients with CTASI pc-ASPECTS score less than 8 survived. ConclusionPC-ASPECTS on CTASI is helpful for predicting functional outcome after BAO recanalization with endovascular treatment. These results should be validated in a randomized controlled trial in order to decide whether or not to treat a patient with BAO.

Evaluating the Prognosis of Ischemic Stroke Using Low-Dose Multimodal Computed Tomography Parameters in Hyperacute Phase

The aim of this study was to evaluate the potential value of low-dose multimodal computed tomography (CT) in predicting prognosis of acute ischemic stroke (AIS) within 6 hours. The admission "one-stop-shop" multimodal CT examination, including noncontrast CT (NCCT), low-dose CT perfusion, and CT angiography (CTA), was performed in patients with symptoms of stroke within 6 hours. Noncontrast CT, CTA source image (CTA-SI), cerebral blood flow (CBF), cerebral blood volume (CBV), time to peak (TTP), and mean transit time (MTT) maps were studied using Alberta Stroke Program Early CT Score (ASPECTS). The regional leptomeningeal collateral (rLMC) score (0-20) was dichotomized into 2 groups: good (11-20) and poor (0-10) rLMC. Poor functional outcomes were defined by a modified Rankin scale score of 3 to 6. One hundred forty-four patients were ultimately selected; 43.8% of them showed poor functional outcomes. They had lower ASPECTSs on NCCT, CTA-SI, CBV, CBF, TTP, and MTT, and poor rLMC was more frequently associated with poor functional outcomes (all P < 0.001). In the multivariate analysis for AIS patients with conservative treatment, CTA-SI-ASPECTS 6 or less (odds ratio [OR], 5.9; 95% confidence interval [95% CI], 1.9-18.4; P = 0.002) and poor collaterals (OR, 5.0; 95% CI, 1.3-15.4; P = 0.017), CBV-ASPECTS 6 or less (OR, 8.0; 95% CI, 2.7-24.0; P < 0.001), CBF-ASPECTS 4 or less (OR, 8.0; 95% CI, 2.0-31.5; P = 0.003), MTT-ASPECTS≤3 (OR, 5.8; 95% CI, 1.8-18.1; P = 0.003), TTP-ASPECTS 4 or less (OR, 5.0; 95% CI, 1.6-15.1; P = 0.005), and NCCT-ASPECTS 8 or less (OR, 5.9; 95% CI, 1.7-20.4; P = 0.005) were significantly associated with poor functional outcome. In the multivariate analysis for AIS patients with thrombolysis, CTA-SI-ASPECTS 6 or less (OR, 27.5; 95% CI, 2.9-262.3; P = 0.004), poor collaterals (OR, 28.0; 95% CI, 2.8-283.0; P < 0.028), and CBV-ASPECTS 6 or less (OR, 18.0; 95% CI, 3.0-107.7; P = 0.002) were associated with poor functional outcomes. Furthermore, the area under the curve (AUC) of the combination of CTA-SI-ASPECTS 6 or less, poor collaterals, and CBV-ASPECTS 6 or less (AUC, 0.87) was greater than that for any single parameter alone: CTA-SI-ASPECTS 6 or less (AUC, 0.80; P < 0.001), poor collaterals (AUC, 0.76; P < 0.001), and CBV-ASPECTS 6 or less (AUC, 0.81; P = 0.002). The combination of CTA-SI-ASPECTS, collaterals, and CBV-ASPECTS may improve predictive power compared with a single parameter alone.

Brain Trust

stroke, NIHSS: stroke, NIHSSFigureFigurePART 3 IN A THREE-PART SERIES The National Institutes of Health Stroke Scale is the most widely used deficit rating scale in modern neurology, but it was not meant to be a bedside rating tool. This critical piece of the neurologic exam for any suspected stroke patient, originally developed as a research tool to measure baseline data in acute stroke clinical trials, has considerable problems that may arise in clinical practice, however. The NIHSS is used as a clinical assessment tool to evaluate the acuity of stroke patients, determine appropriate treatments, and predict patient outcomes. Several scale items require intact language, however, so it gives too much weight to deficits in patients with left versus right hemispheric strokes. A left hemispheric stroke can score up to four more points than a right hemispheric stroke of similar size. Posterior circulation strokes also suffer under the NIHSS because they receive few to no points. Important elements such as diplopia, dysphagia, gait instability, nystagmus, and dizziness receive no score, and a patient with a life-changing stroke could be completely missed if the NIHSS were the only tool considered. A good correlation is seen between NIHSS and the likelihood of finding an eligible large vessel occlusion, but no specific number seems optimal for use. (Stroke 2017;48[2]:513.) Don't fall into some of these traps; the NIHSS must be used with caution in clinical practice for rating stroke severity. Most importantly, a complete and thorough neurologic examination should be second nature and should always include anterior and posterior components. Most electronic medical records will have an NIHSS template built in, and it is widely available online, but consider other online tools such as MDCalc to help calculate a score. (www.mdcalc.com.) Noncontrast CT Neuroimaging of the patient with acute ischemic stroke is used to exclude hemorrhage, assess the degree of brain injury, and identify the vascular lesion responsible for the ischemic deficit. Noncontrast CT (NCCT) of the brain has the main advantage of widespread access and speed of acquisition. It is usually ordered to exclude or confirm hemorrhage and is highly sensitive for this indication, but it is not that sensitive for ischemia before 24 hours, and it has significantly poor sensitivity for the posterior fossa structures. (J Emerg Med 2012 May;42[5]:559.) CT angiography allows visualization of the extracranial and intracranial cerebral arteries, and CTA source images are more sensitive than NCCT scans for detecting early brain infarction. The value of CTA is to identify patients with occlusion of the major vessels within the circle of Willis or extracranial cerebral arteries, but it will still not be reliable for smaller to even medium areas of ischemia, especially in the posterior circulation territory. (Stroke 2009;40[11]:3646.) Recently, the Head Impulse, Nystagmus, Test of Skew (HINTS) exam gained attention as a series of three physical exam maneuvers to differentiate peripheral and central causes of acute vestibular syndrome. A positive HINTS exam can be 100% sensitive and 96% specific for the presence of a central lesion. It is also more sensitive than general neurologic signs: 100% vs 51%. Disclaimer ahead (and it is a big one!): The HINTS exam was tested in an outpatient setting by neuro-ophthalmologists, not emergency physicians, and may not be generalizable to an ED population. (Stroke 2009;40[11]:3504.) Use of brain MRI has significantly increased for evaluating patients with acute ischemic stroke. The rationale for MRI—diffusion-weighted imaging (DWI), in particular—is that this modality has substantially higher sensitivity (88-100%) than that of NCCT for detecting ischemia, with a specificity reported to be as high as 95%-100%. MRI also identifies acute intracranial hemorrhage with similar reliability to NCCT. As if our jobs were not hard enough, emerging evidence now shows that DWI fails to identify acute ischemic stroke in a substantial minority of patients, about seven percent. These DWI-negative stroke cases fall into three categories: posterior circulation ischemia, small strokes, particularly in the brainstem, and hyperacute ischemia (MRI done within six hours of onset). (Neurology 2017;89[3]:256.) Acute ischemic stroke remains one of the most challenging diagnoses in emergency medicine. We need to continue to rise to the challenge, using clinical judgment followed by a thorough and complete neurologic exam and appropriate imaging. Our patients can't afford for us to miss the diagnosis of acute ischemic stroke because early diagnosis can lead to improved outcome, and the neurologic exam and appropriate use of imaging are our best tools.

CT Angiography ASPECTS Predicts Outcome Much Better Than Noncontrast CT in Patients with Stroke Treated Endovascularly.

Noncontrast CT ASPECTS has been investigated as a predictor of outcome in patients with acute ischemic stroke. Our purpose was to investigate whether CTA source images are a better predictor of clinical and radiologic outcomes than NCCT ASPECTS in candidates for endovascular stroke therapy. CT scans of patients (n = 124) were independently evaluated by 2 readers for baseline NCCT and CTA source image ASPECTS and for follow-up ASPECTS. An mRS of ≤2 at 3 months was considered a favorable outcome. Receiver operating characteristic curve analysis was used to assess the ability of NCCT and CTA source image ASPECTS to identify patients with favorable outcomes. A stepwise multiple regression analysis was performed to find independent predictors of outcome. Baseline CTA source image ASPECTS correlated better than NCCT ASPECTS with follow-up ASPECTS (r = 0.76 versus r = 0.51; P for comparison of the 2 coefficients < .001). Receiver operating characteristic curve analysis showed that baseline CTA source image ASPECTS compared with NCCT ASPECTS can better identify patients with favorable outcome (CTA source image area under the curve = 0.83; 95% CI, 0.76-0.91; NCCT area under the curve = 0.67; 95% CI, 0.58-0.77; P < .001). Finally, the stepwise regression analysis showed that lower age, good recanalization, lower time to recanalization, and good baseline CTA source image ASPECTS, not NCCT ASPECTS, were independent predictors of favorable outcome. CTA source image ASPECTS predicts outcome better than NCCT ASPECTS; this finding suggests CTA rather than NCCT as a main step in the decision-making process for patients with acute ischemic stroke.

Hypoattenuation on CTA images with large vessel occlusion: timing affects conspicuity.

Parenchymal hypoattenuation distal to occlusions on CTA source images (CTASI) is perceived because of the differences in tissue contrast compared to normally perfused tissue. This difference in conspicuity can be measured objectively. We evaluated the effect of contrast timing on the conspicuity of ischemic areas. We collected consecutive patients, retrospectively, between 2012 and 2014 with large vessel occlusions that had dynamic multiphase CT angiography (CTA) and CT perfusion (CTP). We identified areas of low cerebral blood volume on CTP maps and drew the region of interest (ROI) on the corresponding CTASI. A second ROI was placed in an area of normally perfused tissue. We evaluated conspicuity by comparing the absolute and relative change in attenuation between ischemic and normally perfused tissue over seven time points. The median absolute and relative conspicuity was greatest at the peak arterial (8.6 HU (IQR 5.1-13.9); 1.15 (1.09-1.26)), notch (9.4 HU (5.8-14.9); 1.17 (1.10-1.27)), and peak venous phases (7.0 HU (3.1-12.7); 1.13 (1.05-1.23)) compared to other portions of the time-attenuation curve (TAC). There was a significant effect of phase on the TAC for the conspicuity of ischemic vs normally perfused areas (P<0.00001). The conspicuity of ischemic areas distal to a large artery occlusion in acute stroke is dependent on the phase of contrast arrival with dynamic CTASI and is objectively greatest in the mid-phase of the TAC.

The association between collateral status, recanalization and long term outcome in stroke patients treated with stent retrievers – Are there indications not to perform thrombectomy based on CT angiography?

Background and purposeTo investigate the association between baseline pial collateral status on computed tomography angiography (CTA) with recanalization and functional outcome in patients with acute anterior circulation stroke treated with stent retriever thrombectomy. Material and methodsRetrospective analysis of 87 patients from a prospective thrombectomy registry. Collateral status on CTA source images was categorized into good, moderate, and poor with the Tan and Miteff scores by two-blinded readers. Association between CTA collateral status and successful recanalization was investigated with univariate regression analysis. Multivariate logistic regression was used to analyse the association between collateral score and favourable clinical outcome (mRS 0-2) and death at follow-up. ResultsMean age was 72.5 years and baseline median NIHSS score was 15. Patients with poor collaterals on Tan score had a significant higher mortality compared with moderate or good collaterals during a mean follow-up period of 5.2 months (85.7% vs. 30.6% vs. 25.7%, P<0.001). Univariate logistic regression analysis did not show a significant association between Tan score (OR 1.681, 95% CI 0.683–4.140) and successful recanalization. Higher age (OR 1.067, 95% CI 1.013–1.124; P=0.015) and lower Tan score (OR 0.421, 95% CI 0.192–0.922; P=0.031) were independent predictors of death at follow-up on multivariate analysis. The Miteff collateral score could be assessed only in 65 of the 87 patients and the Tan collateral score had a higher interrater reliability. ConclusionsPoor collaterals on CTA were associated with a very high rate of fatal outcome in anterior circulation stroke patients despite a high rate of successful recanalization with stent retrievers.

Occurrence of spot signs from hypodensity areas on precontrast CT in intracerebral hemorrhage

Objective: Both the spot signs, which is a bright spot on computed tomography angiography (CTA) source images, and hypodensity areas within a hematoma on precontrast CT scans, which presumably represent uncoagulated blood, have been reported to be predictive of hematoma enlargement in acute spontaneous intracerebral hematoma (ICH). The aim was to investigate densities on precontrast CT scans in an area within a hematoma that matched the locations of spot signs on CTA source images.Methods: In consecutive cases of spontaneous ICH admitted within 6 h after onset, early spot signs on CTA source images and delayed spot signs on delayed-phase CT scans 90 s after CTA were evaluated.Results: Of 177 patients undergoing CTA, 41 (23.2%) showed early spot signs. Among 146 patients who underwent delayed-phase CT scans, 23 (15.8%) demonstrated delayed spot signs but not early spot signs. Spot signs originated from hypodensity areas, including densities <50 HU, in 30 of 35 patients (85.7%) with early spot signs and in 8 of 23 (34.8%) with delayed spot signs. Early spot signs arose from hypodensity areas more frequently than delayed spot signs (p < 0.05). Hematoma enlargement was observed in 10 of 24 patients (41.7%) with early spot signs, but in none with delayed spot signs.Discussion: Some hypodensity areas within ICHs may indicate uncoagulated blood related to ongoing leakage, which are seen as spot signs. Minimum densities in hypodensity areas might correlate with the speed and volume of bleeding.

Abstract WP53: The prognostic value of Posterior Circulation Acute Stroke Prognosis Early Ct Score (pcaspects) on CT perfusion in patients with basilar artery occlusion

Background: CT perfusion (CTP) increases diagnostic confidence in ischaemic stroke. Despite bone-related artefacts, CTP has been shown to improve diagnostic sensitivity compared to non contrast-CT (NCCT) and Computed Tomography Angiography source images (CTA-SI) in posterior circulation strokes. The posterior circulation Acute Stroke Prognosis Early CT score (pcASPECTS) on CTA-SI predicts clinical outcome in patients with basilar artery occlusion (BAO). We assessed the prognostic value of pcASPECTS on CTP in BAO patients. Methods: A retrospective analysis of consecutive patients with BAO diagnosed on CT angiography was performed. pcASPECTS was assessed as evident hypoattenuation on CTA-SI, focally reduced cerebral blood flow (CBF) or cerebral blood volume (CBV), focally increased time to peak of the residue function (Tmax) or mean transit time (MTT). Two investigators independently reviewed the images blinded to clinical outcome. Reliability was assessed with intraclass correlation coefficient (ICC). Good outcome was defined as modified Rankin Scale≤3 at 3 months. Results: We included 43 BAO patients with whole-brain CTP images. In receiver-operating-characteristic (ROC) analysis, the area-under-curve (AUC) was 0.79 (95% CI 0.6-0.9) for pcASPECTS on CBF, 0.77 (95% CI 0.6-0.9) on Tmax, 0.73 (95% CI 0.6-0.9) on MTT, 0.72 (95% CI 0.6-0.9) on CBV, 0.67 (95% CI 0.5-0.8) on CTA-SI. In logistic regression adjusted for age and clinical severity, pcASPECTS&lt;8 was associated with poor outcome on Tmax (OR 14.6, 95% CI 2.3-115; p=0.007) and CBF (OR 15.1, 95% CI 1.3-121; p=0.02). Although CTP AUC did not show higher accuracy in comparison with CTA-SI AUC (p=0.2), in logistic regression, CTA-SI pcASPECTS was not significantly associated with clinical outcome (OR 6.9, 95% CI 0.7-70; p=0.1, adjusted for age, NHSS). Higher pcASPECTS on CBF (OR 0.5 95%CI 0.2-0.9, p=0.04) and Tmax (OR 0.5 95% 0.3-0.9; p=0.02) were associated with lower mortality. Interrater reliability was good for CTP maps (ICC between 0.74 and 0.86 95% CI 0.6-0.9 versus 0.66 for CTA-SI 95% CI 0.4-0.8). Conclusions: The CTP pcASPECTS may identify BAO patients at higher risk of disability and mortality.