Feasibility of deconvolution-based multiphase CT angiography perfusion maps in acute ischemic stroke: Simulation and concordance with CT perfusion

ObjectivesIntegration of CT perfusion (CTP) with requisite non-contrast CT and CT angiography (CTA) stroke imaging may allow efficient stroke lesion volume measurement. Using surrogate images from CTP, we simulated the feasibility of using multiphase CTA (mCTA) to generate perfusion maps and assess target mismatch profiles.Materials and methodsPatients with acute ischemic stroke who received admission CTP were included in this study. Four CTP images (surrogate mCTA, one pre-contrast and three post-contrast, starting at the arterial peak then at 8 s intervals) were selected according to the CTP arterial time-density curve to simulate non-contrast CT and mCTA images. Cerebral blood flow (CBF) and Tmax maps were calculated using the same model-based deconvolution algorithm for the standard CTP and surrogate mCTA studies. Infarct and penumbra were delineated with CBF < 20% and Tmax > 6 s threshold, respectively. Classification accuracy of surrogate mCTA target mismatch (infarct <70 ml; penumbra ≥15 ml; mismatch ratio ≥1.8) with respect to standard CTP was assessed. Agreement between infarct and penumbra volumes from standard CTP and surrogate mCTA maps were evaluated by Bland-Altman analysis.ResultsOf 34 included patients, 28 had target mismatch and 6 did not by standard CTP. Accuracy of classifying target mismatch profiles with surrogate mCTA was 79% with respect to that from standard CTP. Mean  ±  standard deviation of differences (standard CTP minus surrogate mCTA) of infarct and penumbra volumes were 9.8 ± 14.8 ml and 20.1 ± 45.4 ml, respectively.ConclusionsSurrogate mCTA ischemic lesion volumes agreed with those from standard CTP and may be an efficient alternative when CTP is not practical.     

Large Vessel Occlusion Sites Affect Agreement Between Outputs of Three Computed Tomography Perfusion Software Packages

ObjectivesComputed tomography perfusion (CTP) data are important for hyperacute stroke decision making. Available comparisons between outputs of different CTP software packages show variable outcomes. Evaluation for factors associated with agreement between the volume estimates is limited. We assessed for differences in core and penumbra volume estimates of three CTP software packages – AutoMIStar, RAPID, and Vitrea – and analyzed factors associated with agreement between the volume estimates.Materials and MethodsDifferences between software estimates of penumbra and core volumes were calculated for each patient with suspected acute ischemic stroke who underwent CTP. Exploratory hierarchical clustering and principal component analysis were performed to identify factors of decreased volume estimate agreement. Two-sample t-tests were performed, stratified by large vessel occlusion (LVO) location.Results579 CTP studies were performed; 267 were normal, 139 artifacts, with 172 included in the final analysis. 79/172 had LVO of internal carotid artery (ICA, n = 20), M1 (n = 38) and proximal M2 (n = 21). LVO was the only factor associated with decreased software package agreement, and proximal LVO location was associated with general trend of increasing mean differences and standard deviations between software packages (range of mean differences [SD]: non-LVO, -17–6 [4–33] ml; M2, -40–13 [5–39] ml; M1, -43–26 [16–58] ml; ICA, -76–39 [22–97] ml).ConclusionsCore and penumbra volume estimates can be affected by LVO location significantly between CTP software packages.     

CT Perfusion Maps Improve Detection of M2-MCA Occlusions in Acute Ischemic Stroke

ObjectivesMiddle cerebral artery occlusions, particularly M2 branch occlusions are challenging to identify on CTA. We hypothesized that additional review of the CTP maps will increase large vessel occlusion (LVO) detection accuracy on CTA and reduce interpretation time.Materials and MethodsTwo readers (R1 and R2) retrospectively reviewed the CT studies in 99 patients (27 normal, 26 M1-MCA, 46 M2-MCA occlusions) who presented with suspected acute ischemic stroke (AIS). The time of interpretation and final diagnosis were recorded for the CTA images (derived from CTP data), both without and with the CTP maps. The time for analysis for all vascular occlusions was compared using McNemar tests. ROC curve analysis and McNemar tests were performed to assess changes in diagnostic performance with the addition of CTP maps.ResultsWith the addition of the CTP maps, both readers showed increased sensitivity (p = 0.01 for R1 and p = 0.04 for R2), and accuracy (p = 0.02 for R1 and p = 0.004 for R2) for M2-MCA occlusions. There was a significant improvement in diagnostic performance for both readers for detection of M2-MCA occlusions (AUC R1 = 0.86 to 0.95, R2 = 0.84 to 0.95; p < 0.05). Both readers showed reduced interpretation time for all cases combined, as well as for normal studies (p < 0.001) when CTP images were reviewed along with CTA. Both readers also showed reduced interpretation time for M2-MCA occlusions, which was significant for one of the readers (p < 0.02).ConclusionThe addition of CTP maps improves accuracy and reduces interpretation time for detecting LVO and M2-MCA occlusions in AIS. Incorporation of CTP in acute stroke imaging protocols may improve detection of more distal occlusions.     

Mechanical Thrombectomy Improves Outcome for Large Vessel Occlusion Stroke after Cardiac Surgery

BackgroundStroke is a feared complication of cardiac surgery. Modern clot-retrieval techniques provide effective treatment for large vessel occlusion (LVO) strokes. The purpose of this study was to 1) report the incidence of LVO stroke after cardiac surgery at a large academic center, and 2) describe outcomes of postoperative LVO strokes.MethodsAll patients experiencing stroke within 30 days after undergoing cardiac surgery at a single center in 2014-2018 were reviewed. LVOs were identified through review of imaging and medical records, and their characteristics and clinical courses were examined.ResultsOver the study period, 7,112 cardiac surgeries, including endovascular procedures, were performed. Acute ischemic stroke within 30 days after surgery was noted in 163 patients (2.3%). Among those with a stroke, 51/163 (31.3%) had a CTA or MRA, and 15/163 (9.2%) presented with LVO stroke. For all stroke patients, the median time from surgery to stroke was 2 days (interquartile range, IQR, 0–6 days), and for patients with LVO, the median time from surgery to stroke was 4 days (IQR 0–6 days). The overall rate of postoperative LVO was 0.2% (95% CI 0.1–0.4%), though only 6/15 received thrombectomy. LVO patients receiving thrombectomy were significantly more likely to return to independent living compared to those managed medically (n = 4/6, 66.6% for mechanical thrombectomy vs. n = 0/9, 0% for medical management, P = .01). Of the 9 patients who did not get thrombectomy, 6 may currently be candidates for thrombectomy given new expanded treatment windows.ConclusionsThe rate of LVO after cardiac surgery is low, though substantially elevated above the general population, and the majority do not receive thrombectomy currently. Patients receiving thrombectomy had improved neurologic outcomes compared to patients managed medically. Optimized postoperative care may increase the rate of LVO recognition, and cardiac surgery patients and their caregivers should be aware of this effective therapy.     

Yield of ASPECTS and Collateral CTA Selection for Mechanical Thrombectomy within 6–24 hours from Symptom Onset in a Hub and Spoke System

BackgroundRecent extended window trials support the benefit of mechanical thrombectomy in anterior circulation large vessel occlusions with clinical-radiographic dissociation. Using trial imaging criteria, 6% were found eligible for MT in the EW in a hub-and-spoke system. We examined the eligibility and outcomes in consecutive extended window-mechanical thrombectomy patients using more pragmatic selection criteria.MethodsWe retrospectively analyzed single-institution data of anterior circulation large vessel occlusions patients presenting between 6–24 h who underwent mechanical thrombectomy based on a priori determined criteria including non-contrast CT head ASPECTS ≥ 6 and/or CTA collateral scores ASITN/SIR 2-4. Primary outcomes consisted of post-mechanical thrombectomy TICI 2b-3 and 3-month modified Rankin scores; safety outcomes consisted of in-hospital mortality and symptomatic intracerebral hemorrhage.Results767 consecutive acute ischemic strokes patients presented within the 6-24 hour window, and of these 48 (6%) anterior circulation large vessel occlusions patients underwent mechanical thrombectomy. In this cohort the mean age was 63±17 years, 56% were male, the median NIHSS was 16 [IQR 10–19], the median ASPECTS was 9 (IQR 8-10), and 79% (n=38) had good CTA collaterals. Occlusions were primarily M1 MCA (46%), with 29% tandem occlusions. Successful recanalization (mTICI 2b or 3) was achieved in 73% (n=35), while 6% (n=3) of patients developed symptomatic intracerebral hemorrhage. In-hospital mortality was 25% (n=12) while 40% (n=19) achieved 3-month modified Rankin Scores 0–2.ConclusionsOur data suggest the use of pragmatic imaging approach of ASPECTS ≥6 with CTA collateral grade in extended time window which is already established in most hospitals.     

Single-phase CT angiography predicts ASPECTS decay and may help determine when to repeat CT before thrombectomy

ObjetivesTime is relative in large-vessel occlusion acute ischemic stroke (LVO-AIS). We aimed to evaluate the rate of inter-hospital ASPECTS decay in patients transferred from a primary (PSC) to a comprehensive stroke center (CSC); and to identify patients that should repeat computed tomography (CT) before thrombectomy.Materials and methodsThis was a retrospective cohort study of consecutive anterior circulation LVO-AIS transferred patients. The rate of ASPECTS decay was defined as (PSC-ASPECTS – CSC-ASPECTS)/hours elapsed between scans. Single-phase CT angiography (CTA) at the PSC was used to classify the collateral score. We compared patients with futile versus useful CT scan re-evaluation.ResultsWe included 663 patients, of whom 245 (37.0%) repeated CT at a CSC. The median rate of ASPECTS decay was 0.4/h (0.0-0.9). Patients excluded from thrombectomy after a CT scan repeat (n=64) had a median ASPECTS decay rate of 1.18/h (0.83-1.61). Patients with absent collateral circulation had a median rate of 1.51(0.65-2.19). The collateral score was an independent predictor of the ASPECTS decay rate (aβ = -0.35; 95%CI -0.45 - -0.19, p<0.001). Age (aOR: 1.04 95% CI 1.02-1.07, p<0.001), NIHSS (aOR: 1.11 95% CI 1.06-1.15, p<0.001), PSC ASPECTS (aOR: 0.74 95% CI 0.60-0.91, p=0.006) and the CTA collateral score (aOR: 0.14 95% CI 0.08-0.22, p<0.001) were independent predictors of the usefulness of a CT scan repeat.ConclusionsThe rate of ASPECTS decay can be predicted by the CTA collateral score, helping in the selection of patients that would benefit from repeating a CT assessment on arrival at the CSC.     

Elevated Hypoperfusion Intensity Ratio (HIR) observed in patients with a large vessel occlusion (LVO) presenting in the evening

BackgroundCircadian variability has been implicated in timing of stroke onset, yet the full impact of underlying biological rhythms on acute stroke perfusion patterns is not known. We aimed to describe the relationship between time of stroke onset and perfusion profiles in patients with large vessel occlusion (LVO).MethodsA retrospective observational study was conducted using prospective registries of four stroke centers across North America and Europe with systematic use of perfusion imaging in clinical care. Included patients had stroke due to ICA, M1 or M2 occlusion and baseline perfusion imaging performed within 24h from last-seen-well (LSW). Stroke onset was divided into eight hour intervals: (1) Night: 23:00-6:59, (2) Day: 7:00-14:59, (3) Evening: 15:00-22:59. Core volume was estimated on CT perfusion (rCBF <30%) or DWI-MRI (ADC <620) and the collateral circulation was estimated with the Hypoperfusion Intensity Ratio (HIR = [Tmax>10s]/[Tmax>6s]). Non-parametric testing was conducted using SPSS to account for the non-normalized dependent variables.ResultsA total of 1506 cases were included (median age 74.9 years, IQR 63.0-84.0). Median NIHSS, core volumes, and HIR were 14.0 (IQR 8.0-20.0), 13.0mL (IQR 0.0-42.0), and 0.4 (IQR 0.2-0.6) respectively. Most strokes occurred during the Day (n = 666, 44.2%), compared to Night (n = 360, 23.9%), and Evening (n = 480, 31.9%). HIR was highest, indicating worse collaterals, in the Evening compared to the other timepoints (p = 0.006). Controlling for age and time to imaging, Evening strokes had significantly higher HIR compared to Day (p = 0.013).ConclusionOur retrospective analysis suggests that HIR is significantly higher in the evening, indicating poorer collateral activation which may lead to larger core volumes in these patients.     

Absence of Collaterals is Associated with Larger Infarct Volume and Worse Outcome in Patients with Large Vessel Occlusion and Mild Symptoms

Background: Mechanical thrombectomy is the standard of care for patients with large vessel occlusion (LVO) presenting with severe symptoms; however, little is known about the best treatment for patients with LVO and mild symptoms. The absence of good collaterals has been associated with a worse outcome in patients with LVO. In this study, we aim to assess the use of collateral score to identify patients with LVO and mild symptoms that might benefit from mechanical thrombectomy (MT). Methods: A retrospective review of prospectively collected data on patients presenting with mild ischemic stroke (National Institute of Health Stroke Scale [NIHSS] <6) and anterior circulation LVO between September 2015 and July 2017 was performed. Collected data included baseline demographics, NIHSS on admission, Alberta Stroke Program Early CT Score (ASPECTS), location of occlusion, collateral score using Tan scoring system, final infarct volume, and 90-day modified Rankin Scale (mRS). Patients who underwent MT were excluded from this analysis. Two multivariable models were used to assess outcomes. A gamma distributed generalized linear regression model with a log link was used to examine the impact on final infarct volume. To predict the odds of a positive 90-day outcome we estimated a logistic regression. Results: Forty-one patients were identified. Mean age was 67.7-years with 56.1% males. Median NIHSS on admission was 3. The most common vessels involved were the middle cerebral artery (26), internal carotid artery (14), and anterior cerebral artery (1). Twelve patients received intravenous alteplase. Median ASPECTS score was 9, median collateral score was 2.3. Median infarct volume was 10.7 mL. A good functional outcome (mRS 0-2) at 90 days was achieved in 86.4% of patients. There was a negative relationship between collateral score and final infarct volume (−.3134, P = .046). Multivariable regression results showed that with a one-point increase in NIHSS on admission there was a 25% increase in final infarct volume. Higher infarct volume was associated with lower odds of achieving good functional outcome (mRS 0-2) (odds ratio .96, P = .049 [95% confidence interval .918-.999). Conclusions: Most patients with anterior circulation LVO and low NIHSS achieve good long-term functional outcome, however, approximately 15% had significant disability. The absence of collaterals correlates with a larger final infarct volume and a worse long-term functional outcome. Collateral score might be a useful tool in identifying patients with LVO and low NIHSS who might benefit from MT.     

Improving Prognostic Evaluation by 4D CTA for Endovascular Treatment in Acute Ischemic Stroke Patients: A Preliminary Study

Objective: We aim to use 4D CTA with a comprehensive and objective scoring system to assess collateral circulation, and explore the value of prognosis prediction in endovascular treated patients. Methods: Thirty-four patients with unilateral anterior circulation large vessels occlusion were reviewed in this study retrospectively. Single-phase CTA (sCTA) and 4D CTA acquired by CT perfusion scanning were analyzed for collateral circulation assessment. The collateral vessels were scored 0-4 according to modified collateral circulation scoring based on 4D CTA. Zero to two points indicated poor collateral circulation; 3-4 points indicated good collateral circulation. Good prognosis was defined as modified Rankin scale score of 0-2. Logistic regression was used to analyze the relationship between collateral circulation and prognosis. Results: The mean age was 71.1 ± 11.5 years old. Collateral circulation on 4D CTA was an independent factor for predicting the prognosis (odds ratio = .101; 95% confidence interval: [.101-.924]; P = .042), but sCTA could not predict prognosis (P = .214). 4D CTA collateral circulation scoring had a good predicting efficacy on clinical prognosis (Area Under Curve (AUC) = .936; 95% confidence interval: [.751-.992], P < .005). Patients with good collaterals (4D CTA scores of 3-4) could obtain benefit from endovascular treatment (P = .029) compared with patients with poor collaterals (P = 1.000). Conclusions: 4D CTA could be applied to effectively evaluate cerebral collateral status. The accurate assessment of collateral circulation based on 4D CTA would be helpful to make medical decisions, especially for those patients who would undergo endovascular interventional treatment.     

End-to-end artificial intelligence platform for the management of large vessel occlusions: A preliminary study

ObjectivesIn this study, we developed a deep learning pipeline that detects large vessel occlusion (LVO) and predicts functional outcome based on computed tomography angiography (CTA) images to improve the management of the LVO patients.MethodsA series identifier picked out 8650 LVO-protocoled studies from 2015 to 2019 at Rhode Island Hospital with an identified thin axial series that served as the data pool. Data were annotated into 2 classes: 1021 LVOs and 7629 normal. The Inception-V1 I3D architecture was applied for LVO detection. For outcome prediction, 323 patients undergoing thrombectomy were selected. A 3D convolution neural network (CNN) was used for outcome prediction (30-day mRS) with CTA volumes and embedded pre-treatment variables as inputs.ResultFor LVO-detection model, CTAs from 8,650 patients (median age 68 years, interquartile range (IQR): 58-81; 3934 females) were analyzed. The cross-validated AUC for LVO vs. not was 0.74 (95% CI: 0.72-0.75). For the mRS classification model, CTAs from 323 patients (median age 75 years, IQR: 63-84; 164 females) were analyzed. The algorithm achieved a test AUC of 0.82 (95% CI: 0.79-0.84), sensitivity of 89%, and specificity 66%. The two models were then integrated with hospital infrastructure where CTA was collected in real-time and processed by the model. If LVO was detected, interventionists were notified and provided with predicted clinical outcome information.Conclusion3D CNNs based on CTA were effective in selecting LVO and predicting LVO mechanical thrombectomy short-term prognosis. End-to-end AI platform allows users to receive immediate prognosis prediction and facilitates clinical workflow.     

Prediction of intracranial atherosclerotic acute large vessel occlusion by severe hypoperfusion volume growth rate

Background and purposeWe aimed to investigate whether the time elapsed from stroke onset to imaging (OTI) combined with the parameters generated by automated computed tomography perfusion (CTP) could predict large vessel occlusion (LVO) patients with underlying intracranial atherosclerotic disease (ICAD) before endovascular treatment (EVT).MethodsWe performed a prospective cohort of LVO patients with automated CTP before EVT from two comprehensive stroke centers. Severe hypoperfusion volume growth rate was defined as the Time-to-Maximum (Tmax) > 10s divided by OTI. We performed receiver operating characteristic analyses to assess the ICAD prediction performance of all the automated CTP parameters, Delong test to compare the area under the curve (AUC) of severe hypoperfusion volume growth rate with the AUC of the other parameters, and logistic regression analysis to find the independent predictors of LVO with underlying ICAD.ResultsOf the 204 enrolled LVO patients, 95 ICAD patients and 109 non-ICAD patients were identified. The AUC of severe hypoperfusion volume growth rate was 0.86 (95% confidence interval [CI] 0.81 – 0.91, P < 0.001), the cut-off value with the highest Youden Index was ≤ 11.2 mL/h (sensitivity, 78.95%; specificity, 77.06%; accuracy 77.94%), which was larger than the other parameters except for hypoperfusion intensity ratio (HIR) (All P for Delong test < 0.05). Atrial fibrillation (odds ratio [OR]: 0.09, 95%CI: 0.03 – 0.26, P < 0.001), admission ASPECTS (1-point increased OR: 1.25, 95%CI: 1.03 – 1.53, P = 0.024), and severe hypoperfusion volume growth rate (1 mL/h increased OR: 0.94, 95%CI: 0.90 – 0.98, P = 0.003) were associated with underlying ICAD independently.ConclusionsSevere hypoperfusion volume growth rate showed the best performance for LVO with underlying ICAD prediction. Future larger studies for external validation are needed.     

Single-Centre Experience with Patients Selection for Mechanical Thrombectomy Based on Automated Computed Tomography Perfusion Analysis–A Comparison with Computed TomographyCT Perfusion Thrombectomy Trials

Background: In randomized clinical trials, mechanical thrombectomy (MT) was proved to be a highly effective treatment of acute ischemic stroke which improved clinical outcomes. Some of the trials used automated computed tomography perfusion (CTP) analysis for selection of participants. We present a single-center experience with CTP selection and comparison with CTP trials. Methods: Data of consecutive MT patients (from January 2016 to December 2017) were retrospectively reviewed. All patients with multiphase CT angiography confirmed the presence of anterior circulation large vessel occlusion/s in the intracranial internal carotid artery and/or middle cerebral artery (M1 or M2) and with admission brain CTP analyzed by RAPID software were included into the analysis. Results: Sixty-two patients fulfilled the inclusion criteria (mean age was 70.1 ± 13.6 years, females 48.5%). At baseline, National Institutes of Health Stroke Scale score was 16 (IQR?=?13-20), Alberta Stroke Program Early CT Score (ASPECTS) was 8 (IQR?=?7-9), CTP core volume was 20 mL (IQR?=?2-36), and CTP penumbra volume was 145.5 mL (IQR?=?107-184). Time from stroke onset to imaging was 1 hour 32 minutes, time from stroke onset to reperfusion was 3 hours 50 minutes, and median time from CT to reperfusion was 1 hour 56 minutes. Modified thrombolysis in cerebral infarction 2b/3 was achieved in 42 patients (67.7%). Twenty-three patients (37%) had modified Rankin scale 0-2 at 90 days. Conclusions: Our analysis of CTP-selected patients for MT supports clinical applicability of automated CTP analysis into everyday clinical practice.     

Radiological Eye Deviation as a Predictor of Large Vessel Occlusion in Acute Ischaemic Stroke

Background: Detection of large vessel occlusion (LVO) is required for endovascular therapy in acute ischemic stroke (AIS) but CT angiography (CTA) is not always performed at primary stroke centers. Eye deviation on CT brain has been associated with improved stroke detection, but comparisons with angiographic status have been limited. This study sought to determine if radiological eye deviation was associated with LVO. Methods: All AIS patients given intravenous thrombolysis who had acute CTA performed in 2 stroke units were reviewed over 2013-2015 for the presence of LVO. Eye deviation was determined by 2 clinicians blinded to LVO status. Logistic regression was performed to determine which factors predicated LVO. Results: Total 195 AIS patients with acute CTA were identified; 124 (64%) had LVO. Median age was 72 (IQR 64–82) years, median National Institutes of Health Stroke Scale (NIHSS) was 12 (IQR 7-14). LVO patients had a higher NIHSS (15 versus 7, p < .01) and were more likely to have eye deviation on CT brain (71% versus 22.5%, p < .01). Logistic regression confirmed NIHSS score and eye deviation were associated with LVO, with odds ratios of 1.15 (per point) and 5.13 respectively. NIHSS less than equal to 11 gave greatest sensitivity (78.5%) and specificity (76.1%) for LVO with a positive predictive value of 84.7%. Eye deviation was similar with sensitivity 71%, specificity 77.5%, and 84.6%. Conclusions: Eye deviation on CT brain is strongly associated with LVO. Presence of eye deviation on CT should alert clinicians to probability of LVO and for formal angiographic testing if not already performed.     

CT Perfusion collateral index in assessment of collaterals in acute ischemic stroke with delayed presentation: Comparison to single phase CTA

Background & Purpose: Perfusion collateral index (PCI) has been recently defined as a promising measure of collateral status. We sought to compare collateral status assessed via CT-PCI in comparison to single-phase CTA and their relationship to outcome measures including final infarction volume, final recanalization status and functional outcome in ELVO patients.Methods: ELVO patients with anterior circulation large vessel occlusion who had baseline CTA and CT perfusion and underwent endovascular treatment were included. Collateral status was assessed on CTA. PCI from CT perfusion was calculated in each patient and an optimal threshold to separate good vs insufficient collaterals was identified using DSA as reference. The collateral status determined by CTA and PCI were assessed against 3 measured outcomes: 1) final infarction volume; 2) final recanalization status defined by TICI scores; 3) functional outcome measured by 90-day mRS.Results: A total of 53 patients met inclusion criteria. Excellent recanalization defined by TICI ≥2C was achieved in 36 (68%) patients and 23 patients (43%) had good functional outcome (mRS ≤2). While having good collaterals on both CTA and CTP-PCI was associated with significantly (p<0.05) smaller final infarction volume, only good collaterals status determined by CTP-PCI was associated with achieving excellent recanalization (p = 0.001) and good functional outcome (p = 0.003).Conclusion: CTP-based PCI outperforms CTA collateral scores in determination of excellent recanalization and good functional outcome and may be a promising imaging marker of collateral status in patients with delayed presentation of AIS.     

Endovascular Thrombectomy Reduces Risk of Poor Functional Outcomes in Patients Presenting within 0-6 Hours with Large Ischemic Core Volumes on Computed Tomography Perfusion

IntroductionPatients presenting with large ischemic core volumes (LICVs) on computed tomography perfusion (CTP) are at high risk for poor functional outcomes. We sought to identify predictors of outcome in patients with an internal carotid artery (ICA) or middle cerebral artery (MCA) occlusion and LICV.MethodsA large healthcare system's prospectively collected code stroke registry was utilized for this retrospective analysis of patients presenting within 6 hours with at least 50 ml of CTP reduced relative cerebral blood flow (CBF) < 30%. A multivariable logistic regression model was constructed to identify independent predictors (p < 0.05) of poor discharge outcome (modified Rankin scale score 4-6).ResultsOver a 38-month period, we identified 104 patients meeting inclusion criteria, with a mean age of 65.4 ± 16.2 years, median presenting National Institutes of Health Stroke Scale score 20 (IQR 16–24), median ischemic core volume (CBF < 30%) 82 ml (IQR 61-118), and median mismatch volume 80 ml (IQR 56-134). Seventy-five patients (72.1%) had a discharge modified Rankin scale score of 4-6. Sixty-six of 104 (63.5%) patients were treated with endovascular thrombectomy (EVT). In the multivariable regression model, EVT (OR 0.303; 95% CI 0.080-0.985; p = 0.049) and lower blood glucose (per 1-point increase, OR 1.014; 95% CI 1.003-1.030; p = 0.030) were independently protective against poor discharge outcome.ConclusionsEVT is independently associated with a reduced risk of poor functional outcome in patients presenting within 6 hours with ICA or MCA occlusions and LICV.     

Predictive value of the velocity of collateral filling in patients with acute ischemic stroke

The velocity of collateral filling can be assessed in dynamic time-resolved computed tomography (CT) angiographies and may predict initial CT perfusion (CTP) and follow-up lesion size. We included all patients with an M1± internal carotid artery (ICA) occlusion and follow-up imaging from an existing cohort of 1791 consecutive patients who underwent multimodal CT for suspected stroke. The velocity of collateral filling was quantified using the delay of time-to-peak (TTP) enhancement of the M2 segment distal to the occlusion. Cerebral blood volume (CBV) and mean transit time (MTT)-CBV mismatch were assessed in initial CTP. Follow-up lesion size was assessed by magnetic resonance imaging (MRI) or non-enhanced CT (NECT). Multivariate analyses were performed to adjust for extent of collateralization and type of treatment. Our study comprised 116 patients. Multivariate analysis showed a short collateral blood flow delay to be an independent predictor of a small CBV lesion (P<0.001) and a large relative mismatch (P<0.001) on initial CTP, of a small follow-up lesion (P<0.001), and of a small difference between initial CBV and follow-up lesion size (P=0.024). Other independent predictors of a small lesion on follow-up were a high morphologic collateral grade (P=0.001), lack of an additional ICA occlusion (P=0.009), and intravenous thrombolysis (P=0.022). Fast filling of collaterals predicts initial CTP and follow-up lesion size and is independent of extent of collateralization.     

Blood pressure variability and short-term outcomes after mechanical thrombectomy in patients with acute ischemic stroke

ObjectivesThere is limited data evaluating effects of post-mechanical thrombectomy (MT) blood pressure (BP) control on short-term clinical outcomes in acute ischemic stroke (AIS) patients with large vessel occlusion (LVO). We aim to investigate the association of BP variations, after MT, with stroke early outcomes.Materials and methodsA retrospective study was conducted on AIS patients with LVO undergoing MT at a tertiary center over 3.5 years. Hourly BP data was recorded within the first 24- and 48-hours post-MT. BP variability was expressed as the interquartile range (IQR) of BP distribution. Short-term favorable outcome was defined as modified Rankin scale (mRS) 0-3, discharge to home or inpatient rehabilitation facility (IRF).ResultsOf the 95 enrolled subjects, 37(38.9%) had favorable outcomes at discharge and 8 (8.4%) died. After adjustment for confounders, an increase in IQR of systolic blood pressure (SBP) within the first 24 hours after MT revealed a significant inverse association with favorable outcomes (OR 0.43, 95% CI [0.19, 0.96], p = 0.039). Increased median MAP within the first 24 hours after MT correlated with favorable outcomes (OR 1.75, 95% CI [1.09, 2.83], p = 0.021). Subgroup analysis redemonstrated significant inverse association between increased SBP IQR and favorable outcomes (OR 0.48, 95% CI [0.21, 0.97], p = 0.042) among patients with successful revascularization.ConclusionsPost-MT high SBP variability was associated with worse short-term outcomes in AIS patients with LVO regardless of recanalization status. MAP values may be used as indicators for functional prognosis.     

Whole brain CT perfusion combined with CT angiography in patients with subarachnoid hemorrhage and cerebral vasospasm

Objective

To assess cerebral vasospasm (CVS) and monitor cerebral microcirculatory changes in patients with acute subarachnoid hemorrhage (SAH) via CT angiography (CTA) combined with whole-brain CT perfusion (CTP) techniques.

Methods

Sixty patients with SAH (SAH group) and 10 patients without SAH (control group) were selected for a prospective study. CTP combined with CTA and digital subtraction angiography (DSA) studies were performed on patients with initial onset of SAH less than three days. CTA and DSA as well as the CTP parameters such as cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and time-to-peak (TTP) were acquired and analyzed. The relationship of CTA and CTP measurements was assessed in these acute SAH patients.

Results

CTP techniques were used to achieve the perfusion maps of the whole brain in patients with acute SAH. Compared to the control group, mean CBF value was significantly lower while both MTT and TTP values were significantly higher in SAH group (all p < 0.05). Further analysis revealed that mean CBF in patients with CVS, sCVS, Fisher III–IV and Hunt–Hess III–V significantly decreased when compared to patients with nCVS, asCVS, Fisher I–II and Hunt–Hess I–II (p < 0.05). Furthermore both MTT and TTP values were also significantly reduced in patient with CVS, sCVS, Fisher III–IV and Hunt–Hess III–V (p < 0.05).

Conclusion

The study demonstrated that changes of microcirculation in patients with SAH could be assessed by whole-brain CTP. CTP combined with CTA could detect both macroscopic evident vasospasm on CTA and alterations of microcirculation on CTP. Mean CBF was significantly lower in patients with SAH.     

Hypoperfusion Intensity Ratio is Associated with Stroke Mechanism in Patients Undergoing Mechanical Thrombectomy

BackgroundHypoperfusion Intensity Ratio (HIR), defined as Tmax >10s/Tmax >6s on computed tomography perfusion (CTP), and stroke mechanisms have been independently correlated with angiographic collaterals and patient outcomes. Slowly developing atherosclerotic stenosis may foster collateral development, whereas cardioembolic occlusion may occur before collaterals mature. We hypothesized that favorable HIR is associated with large artery atherosclerosis (LAA) stroke mechanism and good clinical outcome.MethodsRetrospective study of consecutive endovascularly-treated stroke patients with intracranial ICA or MCA M1/M2 occlusions, who underwent CTP before intervention, between January 2018 and August 2021. Patients were dichotomized into LAA+ or LAA- based on presence of LAA on angiography. HIR was dichotomized into favorable (HIR+) or unfavorable (HIR-) groups based on published thresholds. Good early outcome was defined as discharge mRS of 0-2. Bivariate and multivariable logistic regression were performed.Results143 patients met inclusion. 21/143 were LAA+ (15%) and 65/143 (45%) were HIR+. HIR+ was significantly more frequent in LAA+ patients (67% vs. 42%, p= 0.035). Controlling for demographics, stroke severity, imaging findings, and medical comorbidities, LAA+ remained independently associated with HIR+ (OR 5.37 [95% CI 1.43 – 20.14]; p=0.013) as did smaller infarction core volume (<30 mL of CBF <30%: OR 7.92 [95% CI 2.27 – 27.64]; p = 0.001). HIR+ was not associated with good clinical outcome.ConclusionsLarge artery atherosclerosis was independently associated with favorable HIR in patients undergoing mechanical thrombectomy. While favorable HIR was associated with smaller pre-treatment core infarcts, reflecting more robust collaterals, it was not associated with good clinical outcome.     

Temporal averaging angiographic reconstructions from whole-brain CT perfusion for the detection of vasospasm

PurposeThe aim of this study is to evaluate the image quality and diagnostic performance of angiographic images reconstructed from whole-brain CT perfusion (CTP) using temporal averaging compared to CT angiography (CTA) for the detection of vasospasm.Materials and methods39 CT studies in 28 consecutive patients who underwent brain CTA with CTP for suspected vasospasm between September 2020 and May 2021 were retrospectively evaluated. The image quality of these two vascular imaging techniques was assessed either quantitatively (image noise, vascular enhancement, signal-to-noise (SNR) and contrast-to-noise (CNR) ratios,) and qualitatively (4 criteria assessed on a 5-point scale).Intra and interobserver agreements and a diagnostic confidence score on the diagnosis of vasospasm were measured. Radiation dose parameters (volume CT dose index (CTDI_vol) and dose-length product (DLP)) were recorded.ResultsBoth SNR and CNR were significantly higher with temporal averaging compared to CTA, increasing by 104% and 113%, respectively (p<0.001).The qualitative assessment found no significant difference in overall image quality between temporal averaging (4.33 ± 0.48) and brain CTA (4.19 ± 0.52) (p = 0.12).There was a significant improvement in intravascular noise and arterial contrast enhancement with temporal averaging.The evaluation of intra and interobserver agreements showed a robust concordance in the diagnosis of vasospasm between the two techniques.ConclusionsTemporal averaging appeared as a feasible and reliable imaging technique for the detection of vasospasm. The use of temporal averaging, replacing brain CTA, could represent a new strategy of radiation and contrast material doses reduction in these patients.