Early prediction of irreversible brain damage after ischemic stroke at CT

Recanalization status and temporal evolution of early ischemic changes following stroke thrombectomy

INTRODUCTION

Present-day computer tomography (CT) scanners have excellent spatial resolution and signal-to-noise ratio and are instrumental detecting early ischemic changes (EIC) in brain. We assessed the temporal changes of EIC based on the recanalization status after thrombectomy.

PATIENTS AND METHODS

The cohort comprises consecutive patients with acute ischemic stroke in anterior circulation treated with thrombectomy in tertiary referral hospital. All baseline and follow-up scans were screened for any ischemic changes and further classified using Alberta Stroke Program Early CT Score (ASPECTS). Generalized linear mixed models were used to analyze the impact of recanalization status using modified Thrombolysis in Cerebral Infarction (mTICI) on temporal evolution of ischemic changes.

RESULTS

We included 614 patients with ICA, M1, or M2 occlusions. Median ASPECTS score was 9 (IQR 7-10) at baseline and 7 (5-8) at approximately 24 h. mTICI 3 was achieved in 207 (33.8%), 2B 241 (39.3%), 2A in 77 (12.6%), and 0-1 in 88 (14.3%) patients. Compared to patients with mTICI 3, those with mTICI 0-1 and 2A had less favorable temporal changes of ASPECTS (p < 0.001). Effect of recanalization was noted in the cortical regions of ICA/M1 patients, but not in their deep structures or patients with M2 occlusions. All ischemic changes detected at baseline were also present at all follow-up images, regardless of the recanalization status.

CONCLUSIONS

Temporal evolution of the ischemic changes and ASPECTS are related to the success of the recanalization therapy in cortical regions of ICA/M1 patients, but not in their deep brain structures or M2 patients. In none of the patients did EIC revert in any brain region after successful recanalization.

Brazilian Angiology and Vascular Surgery Society Guidelines for the treatment of extracranial cerebrovascular disease

Extracranial cerebrovascular disease has been the subject of intense research throughout the world, and is of paramount importance for vascular surgeons. This guideline, written by the Brazilian Society of Angiology and Vascular Surgery (SBACV), supersedes the 2015 guideline. Non-atherosclerotic carotid artery diseases were not included in this document. The purpose of this guideline is to bring together the most robust evidence in this area in order to help specialists in the treatment decision-making process. The AGREE II methodology and the European Society of Cardiology system were used for recommendations and levels of evidence. The recommendations were graded from I to III, and levels of evidence were classified as A, B, or C. This guideline is divided into 11 chapters dealing with the various aspects of extracranial cerebrovascular disease: diagnosis, treatments and complications, based on up-to-date knowledge and the recommendations proposed by SBACV.

Non-contrast dual-energy CT using X-map for acute ischemic stroke: region-specific comparison with simulated 120-kVp CT and diffusion-weighted MR images

PURPOSE

X-map is a non-contrast dual-energy CT (DECT) application to identify acute ischemic stroke (AIS). Our aim was to verify region-specific characteristics of early ischemic changes (EIC) on X-map compared with simulated 120-kVp mixed-CT image and DWI.

METHODS

Fifty AIS patients who underwent DECT and DWI were enrolled (mean age, 76 years; 34 men, 16 women). All datasets including mixed-CT image, X-map, and DWI were transformed into a standard brain atlas with 11 × 2 ROIs based on the ASPECTS + W system. ROIs with EIC on DWI, mixed-CT image, and X-map were defined as DWI-positive, mixed-CT-positive, and X-map-positive, and those with normal finding were DWI-negative, mixed-CT-negative, and X-map-negative respectively, in visual assessment by two neuroradiologists in consensus.

RESULTS

EIC on X-maps were visually relevant to those on the other images: of 221 ROIs with mixed-CT-positive and X-map-positive, 198 (89.6%) were DWI-positive. X-map revealed moderate diagnostic accuracy for AIS compared with DWI in ROC curve analysis (AUC = 0.732). X-map identified EIC in deep white matter more sensitively than mixed-CT image: of 15 ROIs with mixed-CT-negative and X-map-positive in W segments, 14 (93.3%) were DWI-positive. X-map often showed EIC in cortical regions that were not detected on the other images: of 67 ROIs with mixed-CT-negative and X-map-positive in I and M1-M6 segments, 47 (70.1%) were DWI-negative.

CONCLUSIONS

X-map is useful to detect EIC, especially in deep white matter, and may also provide additional information in acute ischemic lesions where DWI cannot be detected.

A novel fully automated method for measuring ASPECTS to improve stroke diagnosis: Comparison to traditional ASPECTS

BACKGROUND AND PURPOSE

To compare the accuracy of subjective Alberta Stroke Program Early CT Score (sASPECTS) evaluation and that of an automated prototype software (aASPECTS) on nonenhanced CT (NECT) in patients with early anterior territory stroke and controls using side-to-side quantification of hypoattenuated brain areas.

METHODS

We retrospectively analyzed the NECT scans of 42 consecutive patients with ischemic stroke before reperfusion and 42 controls using first sASPECTS and subsequently aASPECTS. We assessed the differences in Alberta Stroke Program Early CT Score (ASPECTS) and calculated the sensitivity and specificity of NECT with CT perfusion, whereas cerebral blood volume (CBV) served as the reference standard for brain infarction.

RESULTS

The clot was located in the middle cerebral artery (MCA) in 47.6% of cases and the internal carotid artery (ICA) in 28.6% of cases. Ten cases presented combined ICA and MCA occlusions. The stroke was right sided in 52.4% of cases and left sided in 47.6%. Reader-based NECT analysis yielded a median sASPECTS of 10. The median CBV-based ASPECTS was 7. Compared to the area of decreased CBV, sASPECTS yielded a sensitivity of 12.5% and specificity of 86.8%. The software prototype (aASPECTS) yielded an overall sensitivity of 65.5% and a specificity of 92.2%. The interreader agreement for ASPECTS evaluation of admission NECT and follow-up CT was almost perfect (κ = .93). The interreader agreement of the CBV color map evaluation was substantial (κ = .77).

CONCLUSIONS

aASPECTS of NECT can outperform sASPECTS for stroke detection.

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

OBJECTIVE

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).

MATERIAL AND METHODS

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 3 months >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.

RESULTS

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.

CONCLUSIONS

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.

DGA3-Net: A parameter-efficient deep learning model for ASPECTS assessment for acute ischemic stroke using non-contrast computed tomography

Detecting the early signs of stroke using non-contrast computerized tomography (NCCT) is essential for the diagnosis of acute ischemic stroke (AIS). However, the hypoattenuation in NCCT is difficult to precisely identify, and accurate assessments of the Alberta Stroke Program Early CT Score (ASPECTS) are usually time-consuming and require experienced neuroradiologists. To this end, this study proposes DGA3-Net, a convolutional neural network (CNN)-based model for ASPECTS assessment via detecting early ischemic changes in ASPECTS regions. DGA3-Net is based on a novel parameter-efficient dihedral group CNN encoder to exploit the rotation and reflection symmetry of convolution kernels. The bounding volume of each ASPECTS region is extracted from the encoded feature, and an attention-guided slice aggregation module is used to aggregate features from all slices. An asymmetry-aware classifier is then used to predict stroke presence via comparison between ASPECTS regions from the left and right hemispheres. Pre-treatment NCCTs of suspected AIS patients were collected retrospectively, which consists of a primary dataset (n = 170) and an external validation dataset (n = 90), with expert consensus ASPECTS readings as ground truth. DGA3-Net outperformed two expert neuroradiologists in regional stroke identification (F1 = 0.69) and ASPECTS evaluation (Cohen's weighted Kappa = 0.70). Our ablation study also validated the efficacy of the proposed model design. In addition, class-relevant areas highlighted by visualization techniques corresponded highly with various well-established qualitative imaging signs, further validating the learned representation. This study demonstrates the potential of deep learning techniques for timely and accurate AIS diagnosis from NCCT, which could substantially improve the quality of treatment for AIS patients.

Baseline brain imaging signs in patients with ischaemic stroke by the presence of atrial fibrillation: the ENCHANTED trial

BACKGROUND

We aimed to assess the association of atrial fibrillation (AF) on outcomes in a post hoc analysis of the ENCHANTED (Enhanced Control of Hypertension and Thrombolysis Stroke Study) and how this association is modified by baseline imaging features.

METHODS

Inverse probability of treatment weight was used to remove baseline imbalances between those with and without AF. The primary outcome was the modified Rankin Scale (mRS) scores at 90 days. Secondary outcomes were symptomatic intracerebral haemorrhage (sICH), early neurological deterioration or death within 24 h, and death at 90 days. The logistic regression model was used to determine the associations.

RESULTS

Of the 3285 patients included in this analysis, 636 (19%) had AF at baseline. Compared with non-AF, AF was not significantly associated with an unfavourable shift of mRS (odds ratio 1.09; 95% confidence interval, 0.96-1.24), but with sICH (2.82; 1.78-4.48; IST-3 criteria), early neurological deterioration or death within 24 h (1.31; 1.01-1.70), and death (1.42; 1.12-1.79). Among patients with acute ischaemic signs (presence, extent, swelling and attenuation of acute lesions), AF was associated with the increased risk of all the poor outcomes (all P < 0.04 for interaction).

CONCLUSIONS

We found AF increased risk of sICH, early neurological deterioration or death and death, but not unfavourable functional recovery at day 90 after thrombolysis in patients with AIS. The presence of acute ischaemic brain imaging signs at stroke presentation could be used to improve risk stratification in the presence of AF.

TRIAL REGISTRATION

The trial is registered at ClinicalTrials.gov (NCT01422616).

Assessing Brain Tissue Viability on Nonenhanced Computed Tomography After Ischemic Stroke

BACKGROUND

Treatment for ischemic stroke can be offered beyond conventional time limits for patients with favorable computed tomography perfusion (CTP), but this is not universally available. We sought a threshold for brain attenuation on nonenhanced computed tomography (NECT) to differentiate CTP-defined penumbra vs core, and correlated NECT features with CTP.

METHODS

We retrospectively assessed consecutive patients presenting to King Abdulaziz University Hospital with ischemic stroke (2017-2020), baseline NECT, and a visible defect on concurrent CTP. Using CTP as the reference standard, we measured the attenuation of ischemic and healthy contralateral brain on NECT to produce attenuation ratios (ischemic/normal) for penumbra and core. We used area under the receiver operating characteristic curve to estimate the optimal computed tomography (CT) attenuation ratio for penumbra. Per patient, we qualitatively assessed 8 regions within the affected cerebral hemisphere: on NECT as normal, hypoattenuating (with/out swelling), or isolated swelling and on CTP as normal, penumbra, or core. We sought associations between isolated swelling and penumbra, and between hypoattenuation and core.

RESULTS

We include 142 patients (86 male), mean age 61±14 years. Median 261 minutes (interquartile range, 173-382) to NECT. We measured 206 ischemic lesions (124 penumbra, 82 core). Optimal CT attenuation ratio for identifying penumbra was >0.87, with 86% sensitivity 91% specificity (area under the receiver operating characteristic curve, 0.95 [95% CI, 0.92-0.98]; P<0.0001). We qualitatively assessed 976 cerebral regions (72 isolated swelling, 254 hypoattenuation). On NECT, isolated swelling usually corresponded to CTP penumbra (70/72, 97%), whereas visible NECT hypoattenuation was found with core (141/254, 56%) and penumbra (109/254, 43%). CTP core lesions were rarely normal on NECT (13/155, 8%).

CONCLUSIONS

After ischemic stroke, brain tissue viability can be assessed using NECT. Isolated swelling is highly specific to penumbra. Visible hypoattenuation does not always represent core, nearly half of such lesions were penumbral on concurrent CTP and can be differentiated by measuring lesion attenuation.

Thrombosis and thromboembolism: Brighton collaboration case definition and guidelines for data collection, analysis, and presentation of immunization safety data

This is a Brighton Collaboration case definition of thrombosis and thromboembolism to be used in the evaluation of adverse events following immunization, and for epidemiologic studies for the assessment of background incidence or hypothesis testing. The case definition was developed by a group of experts convened by the Coalition for Epidemic Preparedness Innovations (CEPI) in the context of active development of SARS-CoV-2 vaccines. The case definition format of the Brighton Collaboration was followed to develop a consensus definition and defined levels of certainty, after an exhaustive review of the literature and expert consultation. The document underwent peer review by the Brighton Collaboration Network and by selected expert reviewers prior to submission.

The robust UCATR algorithm enhances the specificity and sensitivity to detect the infarct of acute ischaemic stroke within 6 hours of onset via non-contrast computed tomography images

PROBLEM BACKGROUND

Early detection of acute ischemic stroke (AIS) may provide patients with benefits against harmful health and financial impacts. The use of non-contrast computed tomography images for early detect of the infarct remains controversial.

MATERIALS & METHODS

Here, we used the UCATR algorithm to extract the pixel values of the infarct and the corresponding contralateral healthy area as the control surface in each NCCT slice for the whole brain. Magnetic resonance imaging results were used to verify both areas. We found significant pathological changes in the infarct compared with the corresponding contralateral healthy area in each NCCT slice.

ATTAINED RESULTS

Our approach validated that NCCT can be used to detect the lesion area in the early stage of AIS.

CONCLUSIONS

With obvious advantages such as saving time and the ability to quantify the infarct volume, this approach could help more patients survive the fatal and irreversible pathological process of AIS and improve their quality of life after AIS treatment.

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

Purpose

Reperfusion 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.

Methods

A 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.

Results

Attenuation 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).

Conclusion

Attenuation 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.

Toward automated segmentation for acute ischemic stroke using non-contrast computed tomography

PURPOSE

Non-contrast computed tomography (NCCT) is a first-line imaging technique for determining treatment options for acute ischemic stroke (AIS). However, its poor contrast and signal-to-noise ratio limit the diagnosis accuracy for radiologists, and automated AIS lesion segmentation using NCCT also remains a challenge. In this paper, we propose R2U-RNet, a novel model for AIS lesion segmentation using NCCT.

METHODS

We used an in-house retrospective NCCT dataset with 261 AIS patients with manual lesion segmentation using follow-up diffusion-weighted images. R2U-RNet is based on an R2U-Net backbone with a novel residual refinement unit. Each input image contains two image channels from separate preprocessing procedures. The proposed model incorporates multiscale focal loss to mitigate the class imbalance problem and to leverage the importance of different levels of details. A proposed noisy-label training scheme is utilized to account for uncertainties in the manual annotations.

RESULTS

The proposed model outperformed several iconic segmentation models in AIS lesion segmentation using NCCT, and our ablation study demonstrated the efficacy of the proposed model. Statistical analysis of segmentation performance revealed significant effects of regional stroke occurrence and side of the stroke, suggesting the importance of region-specific information for automated segmentation, and the potential influence of the hemispheric difference in clinical data.

CONCLUSION

This study demonstrated the potentials of R2U-RNet model for automated NCCT AIS lesion segmentation. The proposed model can serve as a tool for accelerating AIS diagnoses and improving the treatment quality of AIS patients.

Importance of computed tomography angiography in acute/hyperacute ischemic stroke

Objective

To evaluate the importance of computed tomography and computed tomography angiography (CTA) in stroke protocols, as well as their impact on endovascular treatment and on the determination of the etiology.

Materials and Methods

Were evaluated 28 patients with acute/hyperacute stroke in the anterior circulation who underwent intracranial and cervical CTA between April 2018 and August 2019. The parameters evaluated were the degree of stenosis, plaque characteristics, type of infarct, treatment, etiology, and the Alberta Stroke Program Early CT Score (ASPECTS).

Results

Of the 28 patients evaluated, 16 (57.1%) had an ASPECTS of 10 (the maximum score, indicative of normality). Four patients (14.3%) underwent thrombolytic treatment, and seven (25.0%) underwent mechanical thrombectomy. The etiology was atherosclerosis in 32.1% of the patients, cerebral small-vessel disease in 7.1%, cardioembolic in 7.1%, and undetermined in 53.6%. Regarding plaque, 17.9% of the patients presented stenosis ≥ 50%, 21.4% presented stable plaques, and 42.9% presented vulnerable plaques. Patients with a lower ASPECTS were more likely to have relevant stenosis and were more likely to have a total infarct.

Conclusion

In the evaluation of patients with acute/hyperacute strokes, CTA provides important information, identifying occlusion, as well as helping define the etiology and inform decisions regarding treatment.

SWI as a promising tool comparable to CT perfusion in evaluation of acute cerebral infarction

Background

The recent advances in magnetic resonance imaging techniques have improved the assessment of acute stroke. Susceptibility weighted imaging (SWI) has a crucial role in the management plan of cerebral ischemia. This study was aimed to assess the role of susceptibility-weighted imaging in assessment of area at risk (pneumbra) compared to CT perfusion in patients with acute ischemic infraction.

Results

We found the mean aspect score for SWI 4 ± 1.4 and mean aspect for DWI 7.6 ± 1.2; in addition, mean aspect for CTP was 4.6 ± 1.3. Significant difference is noted between the SWI and DWI with significant p value. But there is no significant difference between the SWI and CTP ASPECT scores.

Conclusion

SWI is a promising technique and comparable to CT perfusion is evaluation of penumbra in the settings of acute infarction.

Overview of Imaging Modalities in Stroke

PURPOSE OF THE REVIEW

This article reviews common imaging modalities used in diagnosis and management of acute stroke. Each modality is discussed individually and clinical scenarios are presented to demonstrate how to apply these modalities in decision-making.

RECENT FINDINGS

Advances in neuroimaging provide unprecedented accuracy in determining tissue viability as well as tissue fate in acute stroke. In addition, advances in machine learning have led to the creation of decision support tools to improve the interpretability of these studies.

SUMMARY

Noncontrast head computed tomography (CT) remains the most commonly used initial imaging tool to evaluate stroke. Its exquisite sensitivity for hemorrhage, rapid acquisition, and widespread availability make it the ideal first study. CT angiography (CTA), the most common follow-up study after noncontrast head CT, is used primarily to identify intracranial large vessel occlusions and cervical carotid or vertebral artery disease. CTA is highly sensitive and can improve accuracy of patient selection for endovascular therapy through delineations of ischemic core. CT perfusion is widely used in endovascular therapy trials and benefits from multiple commercially available machine-learning packages that perform automated postprocessing and interpretation. Magnetic resonance imaging (MRI) and magnetic resonance angiography (MRA) can provide valuable insights for outcomes prognostication as well as stroke etiology. Optical coherence tomography (OCT), positron emission tomography (PET), single-photon emission computerized tomography (SPECT) offer similar insights. In the clinical scenarios presented, we demonstrate how multimodal imaging approaches can be tailored to gain mechanistic insights for a range of cerebrovascular pathologies.

Psychometric Evaluation of the Krogh-Poulsen Test for the Diagnosis of the Temporomandibular Disorders

The Krogh-Poulsen Test is a classic instrument to measure dysfunction of the stomatognathic system whose psychometric properties are unknown. This study aimed to evaluate the psychometric properties of the Krogh-Poulsen Test for the diagnosis of temporomandibular disorders (TMDs). A cross-sectional study was designed, including 119 patients (63 patients with TMD and 56 healthy controls). Factorial validity, inter-rater reliability, error of measurement, diagnostic validity of the Krogh-Poulsen Test, and concurrent validity were analyzed. The Krogh-Poulsen Test showed a three-factor structure. The inter-rater agreement could be considered very good with a kappa index of 0.87 (95% CI 0.83-0.90) and Standard Error of Measurement of 0.79. Correlations were strong with other orofacial instruments, moderate with instruments measuring TMD-related disorders such as neck pain, headache, or dizziness, and poor with generic quality of life instruments. The Area Under the Curve ROC was 0.928 showing, for a cut-off point >1, a sensitivity of 90.48 (95% CI 80.4-96.4) and a specificity of 85.71 (95% CI 73.8-93.6) for the diagnosis of TMD disorders. The Krogh-Poulsen Test showed a three-factor structure, very good inter-rater reliability, a strong correlation with other orofacial instruments, and an excellent capacity to discriminate between patients with or without TMD.

Reversible Ischemic Lesion Hypodensity in Acute Stroke CT Following Endovascular Reperfusion

BACKGROUND AND OBJECTIVES

In acute stroke, early ischemic lesion hypodensity in computed tomography (CT) is considered the imaging hallmark of brain infarction, representing a state of irreversible tissue damage with a continual increase of net water uptake. This dogma is however challenged by rare cases of apparently reversed early lesion hypodensity following complete reperfusion. The purpose of this study was to investigate the occurrence of reversible ischemic edema after endovascular treatment.

METHODS

184 acute ischemic anterior circulation stroke patients were included after consecutive screening. Ischemic brain edema was determined using quantitative lesion net water uptake (NWU) in admission-CT and follow-up CT based on CT-densitometry and ΔNWU was calculated as the difference. The association of edema progression to imaging and clinical parameters was investigated. Clinical outcome was assessed using modified Ranking Scale (mRS) scores at day 90.

RESULTS

27/184 patients (14.7%) showed edema arrest and 3 patients (1.6%) exhibited significant edema reversibility. Higher degree of recanalization (odds ratio (OR): 2.96, 95%CI: 1.46-6.01, p<0.01) and shorter time from imaging to recanalization (OR/hour: 0.32, 95%CI: 0.18-0.54, p<0.0001) were significantly associated with edema arrest or reversibility. Clinical outcome was significantly better in patients without edema progression (median mRS 2 versus mRS 5, p=0.004).

DISCUSSION

Albeit rare, lesion hypodensity considered to be representative of early infarct in acute stroke CT may be reversible following complete recanalization. Arrest of edema progression of acute brain infarct lesions may occur after successful rapid vessel recanalization, resulting in improved functional outcome. Future research is needed to investigate conditions where early revascularization may halt or even reverse vasogenic edema of ischemic tissue.

A comprehensive assessment of physical image quality of five different scanners for head CT imaging as clinically used at a single hospital centre-A phantom study

Nowadays, given the technological advance in CT imaging and increasing heterogeneity in characteristics of CT scanners, a number of CT scanners with different manufacturers/technologies are often installed in a hospital centre and used by various departments. In this phantom study, a comprehensive assessment of image quality of 5 scanners (from 3 manufacturers and with different models) for head CT imaging, as clinically used at a single hospital centre, was hence carried out. Helical and/or sequential acquisitions of the Catphan-504 phantom were performed, using the scanning protocols (CTDI_vol range: 54.7–57.5 mGy) employed by the staff of various Radiology/Neuroradiology departments of our institution for routine head examinations. CT image quality for each scanner/acquisition protocol was assessed through noise level, noise power spectrum (NPS), contrast-to-noise ratio (CNR), modulation transfer function (MTF), low contrast detectability (LCD) and non-uniformity index analyses. Noise values ranged from 3.5 HU to 5.7 HU across scanners/acquisition protocols. NPS curves differed in terms of peak position (range: 0.21–0.30 mm^-1). A substantial variation of CNR values with scanner/acquisition protocol was observed for different contrast inserts. The coefficient of variation (standard deviation divided by mean value) of CNR values across scanners/acquisition protocols was 18.3%, 31.4%, 34.2%, 30.4% and 30% for teflon, delrin, LDPE, polystyrene and acrylic insert, respectively. An appreciable difference in MTF curves across scanners/acquisition protocols was revealed, with a coefficient of variation of f_50%/f_10% of MTF curves across scanners/acquisition protocols of 10.1%/7.4%. A relevant difference in LCD performance of different scanners/acquisition protocols was found. The range of contrast threshold for a typical object size of 3 mm was 3.7–5.8 HU. Moreover, appreciable differences in terms of NUI values (range: 4.1%-8.3%) were found. The analysis of several quality indices showed a non-negligible variability in head CT imaging capabilities across different scanners/acquisition protocols. This highlights the importance of a physical in-depth characterization of image quality for each CT scanner as clinically used, in order to optimize CT imaging procedures.

Brain Imaging Findings and Response to Intravenous Thrombolysis in Posterior Circulation Stroke

INTRODUCTION

Intravenous thrombolysis (IVT) is a standard treatment for both anterior circulation ischaemic stroke (ACIS) and posterior circulation ischaemic stroke (PCIS). Our aim was to evaluate the predictors for a good clinical outcome and intracerebral haemorrhage (ICH) in patients undergoing posterior circulation IVT based on the initially performed CT or MR imaging.

METHODS

The study cohort consisted of 1643 consecutive patients with acute ischaemic stroke (1440 ACIS, 203 PCIS cases) who underwent IVT. ICH was classified according to the European Cooperative Acute Stroke Study (ECASS) I protocol. Clinical outcome was assessed using the modified Rankin scale (mRS). Early ischaemic signs and pre-existing structural signs were assessed.

RESULTS

Good clinical outcomes (mRS 0-1) were noted in 45.3% of patients with PCIS, with a mortality rate of 14.8%. ICH was noted in 8.3%, and a large haemorrhage was found in 2.4% of patients. Some early ischaemic signs and pre-existing structural signs on initial CT/MR imaging correlated significantly with the 90-day clinical outcome.

CONCLUSIONS

Early ischaemic signs and pre-existing structural signs should be considered during the assessment of patients with PCIS eligible for IVT. Tissue hypoattenuation on initial CT scans correlates with an increased risk of death. Similarly to anterior circulation, atrophy on initial MRI may negatively predict good clinical outcome in posterior circulation.

Platelet-Reactive Antibodies in Patients after Ischaemic Stroke-An Epiphenomenon or a Natural Protective Mechanism

Ischaemic brain damage induces autoimmune responses, including the production of autoantibodies with potential neuroprotective effects. Platelets share unexplained similarities with neurons, and the formation of anti-platelet antibodies has been documented in neurological disorders. The aim of this study was to investigate the presence of anti-platelet antibodies in the peripheral blood of patients after ischaemic stroke and determine any clinical correlations. Using a flow cytometry-based platelet immunofluorescence method, we detected platelet-reactive antibodies in 15 of 48 (31%) stroke patients and two of 50 (4%) controls (p < 0.001). Western blotting revealed heterogeneous reactivities with platelet proteins, some of which overlapped with brain proteins. Stroke patients who carried anti-platelet antibodies presented with larger infarcts and more severe neurological dysfunction, which manifested as higher scores on the National Institutes of Health Stroke Scale (NIHSS; p = 0.009), but they had a greater recovery in the NIHSS by the time of hospital discharge (day 7 ± 2) compared with antibody-negative patients (p = 0.043). Antibodies from stroke sera reacted more strongly with activated platelets (p = 0.031) and inhibited platelet aggregation by up to 30.1 ± 2.8% (p < 0.001), suggesting the potential to interfere with thrombus formation. In conclusion, platelet-reactive antibodies can be found in patients soon after ischaemic stroke and correlate with better short-term outcomes, suggesting a potential novel mechanism limiting thrombosis.

Noise reduction in CT image using prior knowledge aware iterative denoising

The clinical demand for low image noise often limits the slice thickness used in many CT applications. However, a thick-slice image is more susceptible to longitudinal partial volume effects, which can blur key anatomic structures and pathologies of interest. In this work, we develop a prior-knowledge-aware iterative denoising (PKAID) framework that utilizes spatial data redundancy in the slice increment direction to generate low-noise, thin-slice images, and demonstrate its application in non-contrast head CT exams. The proposed technique takes advantage of the low-noise of thicker images and exploits the structural similarity between the thick- and thin-slice images to reduce noise in the thin-slice image. Phantom data and patient cases (n=3) of head CT were used to assess performance of this method. Images were reconstructed at clinically-utilized slice thickness (5 mm) and thinner slice thickness (2 mm). PKAID was used to reduce image noise in 2 mm images using the 5 mm images as low-noise prior. Noise amplitude, noise power spectra (NPS), modulation transfer function (MTF), and slice sensitivity profiles (SSP) of images before/after denoising were analyzed. The NPS and MTF analysis showed that PKAID preserved noise texture and resolution of the original thin-slice image, while reducing noise to the level of thick-slice image. The SSP analysis showed that the slice thickness of the original thin-slice image was retained. Patient examples demonstrated that PKAID-processed, thin-slice images better delineated brain structures and key pathologies such as subdural hematoma compared to the clinical 5 mm images, while additionally reducing image noise. To test an alternative PKAID utilization for dose reduction, a head exam with 40% dose reduction was simulated using projection-domain noise insertion. The image of 5 mm slice thickness was then denoised using PKAID. The results showed that the PKAID-processed reduced-dose images maintained similar noise and image quality compared to the full-dose images.

Towards subject-level cerebral infarction classification of CT scans using convolutional networks

Automatic evaluation of 3D volumes is a topic of importance in order to speed up clinical decision making. We describe a method to classify computed tomography scans on volume level for the presence of non-acute cerebral infarction. This is not a trivial task, as the lesions are often similar to other areas in the brain regarding shape and intensity. A three stage architecture is used for classification: 1) A cranial cavity segmentation network is developed, trained and applied. 2) Region proposals are generated 3) Connected regions are classified using a multi-resolution, densely connected 3D convolutional network. Mean area under curve values for subject level classification are 0.95 for the unstratified test set, 0.88 for stratification by patient age and 0.93 for stratification by CT scanner model. We use a partly segmented dataset of 555 scans of which 186 scans are used in the unstratified test set. Furthermore we examine possible dataset bias for scanner model and patient age parameters. We show a successful application of the proposed three-stage model for full volume classification. In contrast to black-box approaches, the convolutional network’s decision can be further assessed by examination of intermediate segmentation results.

Delayed functional independence after thrombectomy: temporal characteristics and predictors

Background

Variability in early neurological improvement after endovascular thrombectomy (EVT) for large vessel occlusion (LVO) stroke is well documented. Understanding the temporal progression of functional independence after EVT, especially delayed functional independence in patients who do not experience early improvement, is essential for prognostication and rehabilitation.

Objective

To determine the incidence of early and delayed functional independence and identify associated predictors after EVT.

Methods

A retrospective analysis of prospectively collected data on patients undergoing EVT in the setting of anterior circulation LVO was performed. Demographic, clinical, radiological, treatment, and procedural information were analyzed. Incidence and predictors of early functional independence (EFI, modified Rankin Scale (mRS) score 0–2 at discharge) and delayed functional independence (DFI, mRS score 0–2 at 90 days in non-EFI patients) were analyzed.

Results

Three hundred and fifty-five patients met the study criteria. 55% were women and mean age was 71±15. Mean National Institutes of Health Stroke Scale (NIHSS) score was 17±6 and median Alberta Stroke Program Early CT Score was 9 (8-10). EFI was observed in 21% (73) of patients. Among non-EFI patients (282), DFI was observed in 30% (85) of patients. Shorter time to treatment (p=0.03), lower 24 hours NIHSS score (p<0.001), and smaller follow-up infarct volume (p=0.003) were independent predictors of EFI. Younger age (p=0.011), lower 24 hours NIHSS score (p=0.001), and absence of parenchymal hemorrhage (PH2; p=0.039) were independent predictors of DFI.

Conclusion

Approximately one-fifth of patients experience EFI and one-third of non-early improvers experience DFI. Younger age, lower 24 hours NIHSS score, and absence of parenchymal hemorrhage were independent predictors of DFI among non-early improvers. Further studies are required to improve our understanding of DFI.

Imaging Ischemic and Hemorrhagic Disease of the Brain in Dogs

Strokes, both ischemic and hemorrhagic, are the most common underlying cause of acute, non-progressive encephalopathy in dogs. In effect, substantial information detailing the underlying causes and predisposing factors, affected vessels, imaging features, and outcomes based on location and extent of injury is available. The features of canine strokes on both computed tomography (CT) and magnetic resonance imaging (MRI) have been described in numerous studies. This summary article serves as a compilation of these various descriptions. Drawing from the established and emerging stroke evaluation sequences used in the investigation of strokes in humans, this summary describes all theoretically available sequences. Particular detail is given to logistics of image acquisition, description of imaging findings, and each sequence's advantages and disadvantages. As the imaging features of both forms of strokes are highly representative of the underlying pathophysiologic stages in the hours to months following stroke onset, the descriptions of strokes at various stages are also discussed. It is unlikely that canine strokes can be diagnosed within the same rapid time frame as human strokes, and therefore the opportunity for thrombolytic intervention in ischemic strokes is unattainable. However, a thorough understanding of the appearance of strokes at various stages can aid the clinician when presented with a patient that has developed a stroke in the days or weeks prior to evaluation. Additionally, investigation into new imaging techniques may increase the sensitivity and specificity of stroke diagnosis, as well as provide new ways to monitor strokes over time.

Laminarin Pretreatment Provides Neuroprotection against Forebrain Ischemia/Reperfusion Injury by Reducing Oxidative Stress and Neuroinflammation in Aged Gerbils

Laminarin is a polysaccharide isolated from brown algae that has various biological and pharmacological activities, such as antioxidant and anti-inflammatory properties. We recently reported that pretreated laminarin exerted neuroprotection against transient forebrain ischemia/reperfusion (IR) injury when we pretreated with 50 mg/kg of laminarin once a day for seven days in adult gerbils. However, there have been no studies regarding a neuroprotective effect of pretreated laminarin against IR injury in aged animals and its related mechanisms. Therefore, in this study, we intraperitoneally inject laminarin (50 mg/kg) once a day to aged gerbils for seven days before IR (5-min transient ischemia) surgery and examine the neuroprotective effect of laminarin treatment and the mechanisms in the gerbil hippocampus. IR injury in vehicle-treated gerbils causes loss (death) of pyramidal neurons in the hippocampal CA1 field at five days post-IR. Pretreatment with laminarin effectively protects the CA1 pyramidal neurons from IR injury. Regarding the laminarin-treated gerbils, production of superoxide anions, 4-hydroxy-2-nonenal expression and pro-inflammatory cytokines [interleukin(IL)-1β and tumor necrosis factor-α] expressions are significantly decreased in the CA1 pyramidal neurons after IR. Additionally, laminarin treatment significantly increases expressions of superoxide dismutase and anti-inflammatory cytokines (IL-4 and IL-13) in the CA1 pyramidal neurons before and after IR. Taken together, these findings indicate that laminarin can protect neurons from ischemic brain injury in an aged population by attenuating IR-induced oxidative stress and neuroinflammation.

Observer Agreement on Computed Tomography Perfusion Imaging in Acute Ischemic Stroke

Supplemental Digital Content is available in the text.

Computed tomography (CT) perfusion (CTP) provides potentially valuable information to guide treatment decisions in acute stroke. Assessment of interobserver reliability of CTP has, however, been limited to small, mostly single center studies. We performed a large, internet-based study to assess observer reliability of CTP interpretation in acute stroke.

Eligibility for late endovascular treatment using DAWN, DEFUSE-3, and more liberal selection criteria in a stroke center

Background and purpose

The real-life application of DAWN and DEFUSE-3 trials has been poorly investigated. We aimed to identify the proportion of patients with acute ischemic stroke (AIS) eligible for late endovascular treatment (EVT) in our stroke center based on trial and more liberal selection criteria.

Methods

All consecutive patients in our stroke registry (2003–2017) admitted within 5–23 hours of last proof of good health were selected if they had complete clinical and radiological datasets. We calculated the proportion of patients eligible for late EVT according to trial (DAWN and/or DEFUSE-3) and more liberal clinical/imaging mismatch criteria (including lower admission National Institutes of Health Stroke Scale score and Alberta Stroke Program Early CT Score for core estimation).

Results

Of 1705 patients with AIS admitted to our comprehensive stroke center in the late time window, we identified 925 patients with complete clinical and radiological data. Among them, the proportions of late EVT eligibility were 2.5% (n=23) with DAWN, 5.1% (n=47) with DEFUSE-3, and 11.1% (n=103) with more liberal criteria. Considering late-arriving patients with large vessel occlusion (n=221), the percentages of eligible patients were 10.4%, 21.3%, and 46.6%, respectively. A favorable outcome was observed at comparable rates in treated patients selected by trial or liberal criteria (67% vs 58%, p=0.49).

Conclusions

In a long-term stroke registry, the proportion of late EVT eligibility varied greatly according to selection criteria and referral pattern. Among late-arriving patients referred to our comprehensive stroke center, we found 5.6% eligible according to trial (DAWN/DEFUSE-3) and 11.1% according to liberal criteria. These data indicate that late EVT could be offered to a larger population of patients if more liberal criteria are applied.

Earlier IV thrombolysis and mechanical thrombectomy in acute ischemic stroke are associated with a better recanalization

Introduction:

Combined intravenous thrombolysis (IVT) and mechanical thrombectomy (MT) are the recommended treatment options for acute ischemic stroke (AIS). It is unclear whether earlier IVT and MT management can predict complete vessel recanalization.

Methods:

In this single-center retrospective observational study, we included 81 consecutive subjects with proximal middle cerebral artery AIS (age 70.5 ± 14.2 years, 53% female) who had both IVT and MT. We assessed recanalization after mechanical procedure according to modified thrombolysis in cerebral infarction (TICI) score as well as the National Institute of Health Stroke Scale (NIHSS) score at 24 h. Outcomes were modified Rankin Scale (mRS) at discharge, mRS at 3 months, death at 3 months, and prevalence of intracerebral hemorrhage during hospitalization.

Results:

Multinomial logistic regression ( χ 2 = 49.4, p = 0.0075, pseudo- R 2 = 0.26) showed that complete recanalization (TICI score = 3) was predicted by lower door-to-MT time ( p = 0.014, 95% confidence interval (CI) = −0.09 to −0.01) and lower symptoms-to-IVT time ( p = 0.045, 95% CI = −0.038 to −0.0004). An NIHSS score ≥10 at 24 h was predicted by higher baseline NIHSS ( p < 0.0001) and lower TICI score ( p = 0.009). Lower NIHSS at 24 h predicted a good outcome according to mRS at 3 months ( p = 0.006). Similarly, higher NIHSS at 24 h was a predictor of death at 3 months ( p = 0.013).

Conclusions:

The present study suggests that bridging therapy may improve vascular recanalization when both IVT and MT are performed earlier.

Targeting mast cell as a neuroprotective strategy

Background: Mast cells (MCs) are perivascularly located immune cells of haematopoietic origin. Emerging evidences suggest that the activation of MCs play important roles in the pathogenesis of blood brain barrier disruption, neuroinflammation, and neurodegeneration. Objectives: In this review, we aimed to discuss the detrimental effects of MCs in response to various types of brain injury, as well as the therapeutic potential and neuroprotective effects of targeting the activation and degranulation of MCs, particularly in the management of the acute phase. Methods: An extensive online literature search was conducted through Pubmed/Central on March 2018. Then, we comprehensively summarized the effects of the activation of brain MCs in acute brain injury along with current pharmacological strategies targeting at the activation of MCs. Results: The review of the current literature indicated that the activation and degranulation of brain MCs significantly contribute to the acute pathological process following different types of brain injury including focal and global cerebral ischaemia, intracerebral haemorrhage, subarachnoid haemorrhage, and traumatic brain injury. Conclusions: Brain MCs significantly contribute to the acute pathological processes following brain injury. In that regard, targeting brain MCs may provide a novel strategy for neuroprotection.

Unenhanced Dual-Energy Computed Tomography: Visualization of Brain Edema

PURPOSE

The aim of this study was to determine whether dual-energy computed tomography (DECT) imaging is superior to conventional noncontrast computed tomography (CT) imaging for the detection of acute ischemic stroke.

MATERIALS AND METHODS

This was a retrospective, single-center study of 40 patients who presented to the emergency department (ED) of a major, acute care, teaching center with signs and symptoms of acute stroke. Only those patients who presented to the ED within 4 hours of symptom onset were included in this study. All 40 patients received a noncontrast DECT of the head at the time of presentation. Each patient also received standard noncontrast CT of the head 24 hours after their initial presentation to the ED. "Brain edema" images were then reconstructed using 3-material decomposition with parameters adjusted to suppress gray/white matter contrast while preserving edema and increasing its conspicuity. The initial unenhanced, mixed images, brain edema, and 24-hour follow-up true noncontrast (TNC) images were reviewed and assigned Alberta Stroke Program Early CT scores. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated.

RESULTS

Of the 40 patients, 28 (70%) were diagnosed with an acute infarction. Brain edema reconstructions were better able to predict end infarction volume, with Alberta Stroke Program Early CT scores similar to the 24-hour follow-up TNC CT (7.75 vs 7.7; P > 0.05), whereas the mixed images routinely underestimated the extent of infarction (8.975 vs 7.7; P < 0.001). Initial TNC images had a sensitivity, specificity, PPV, and NPV of 80% (95% confidence interval [CI], 51.9%-95.7%), 72.7% (95% CI, 39%-94%), 80% (95% CI, 51.9%-95.7%), and 72.73% (95% CI, 51.91%-95.67%), respectively. The DECT brain edema images provided a sensitivity, specificity, PPV, and NPV of 93.33% (95% CI, 68.05%-99.83%), 100% (95% CI, 71.51%-100%), 100% (95% CI, 76.84%-100%), and 91.67% (95% CI, 61.52%-99.79%), respectively. There was very good interrater reliability across all 3 imaging techniques.

CONCLUSION

Brain edema reconstructions are able to more accurately detect edema and end-infarct volume as compared with initial TNC images. This provides a better assessment of the degree and extent of infarction and may serve to better guide therapy in the future.

Magnesium Protects in Episodes of Critical Perfusion after Aneurysmal SAH

BACKGROUND

To analyze whether magnesium has a neuroprotective effect during episodes that indicate a critical brain perfusion after aneurysmal subarachnoid hemorrhage (SAH).

METHODS

107 patients with aSAH were randomized to continuously receive intravenous magnesium sulfate with target serum levels of 2.0 - 2.5 mmol/l (n = 54) or isotonic saline (n = 53). Neurological examination and transcranial Doppler sonography (TCD) were performed daily, Perfusion-CT (PCT) was acquired in 3-day intervals, angiography in case of suspected vasospasm. The primary endpoint was the development of secondary infarction following episodes of delayed ischemic neurological deficit (DIND), elevated mean flow velocity (MFV) in TCD or pathological findings in PCT.

RESULTS

In the magnesium group, 9 episodes of DIND were registered, none was followed by secondary infarction. In the control group, 23 episodes of DIND were registered, 9 were followed by secondary infarction (p < 0.05). In the magnesium group, 114 TCD-measurements showed an elevated MFV(> 140 cm/s). 7 were followed by new infarction. In control patients, 135 measurements showed elevated MFV, 32 were followed by new infarction (p < 0.05). 10 of 117 abnormal PCT-findings were followed by new infarction, compared to 30 of 122 in the control-group (p < 0.05).

CONCLUSION

DIND, elevated MFV in TCD and abnormal PCT are findings which are associated with an increased risk to develop delayed secondary infarction. The results of this analysis suggest that magnesium-treatment may reduce the risk to develop infarction in a state of critical brain perfusion.

NCCT and CTA-based imaging protocol for endovascular treatment selection in late presenting or wake-up strokes

Introduction

Recently, the benefit of selecting patients for endovascular treatment (EVT) beyond the 6-hour time window using a tissue-based approach was demonstrated in two randomized trials. The optimal imaging protocol for selecting patients is under debate, and it is still unknown if a simpler and faster protocol may adequately select patients with wake-up stroke (WUS) and late-presenting stroke (LPS) for EVT.

Objective

To compare outcomes of patients submitted to EVT presenting within 6 hours of symptom onset or 6–24 hours after last seen well, selected using non-contrast computed tomography (NCCT) and CT angiography (CTA).

Methods

An observational study was performed, which included consecutive patients with anterior circulation ischemic stroke with large vessel occlusion treated with EVT. Patients presenting within 6 hours were treated if their NIH Stroke Scale (NIHSS) score was ≥6 and Alberta Stroke Program Early CT score (ASPECTS) was ≥6, while patients presenting with WUS or 6–24 hours after last seen well (WUS/LPS) were treated if their NIHSSscore was ≥12 and ASPECTS was ≥7.

Results

249 patients were included, 63 of whom were in the WUS/LPS group. Baseline characteristics were similar between groups, except for longer symptom-recanalization time, lower admission NIHSS (16 vs 17, P=0.038), more frequent tandem occlusions (25.4% vs 11.8%, P=0.010), and large artery atherosclerosis etiology (22.2% vs 11.8%, P=0.043) in the WUS/LPS group. No differences in symptomatic intracranial hemorrhage, peri-procedural complications or mortality were found between groups. Three-month functional independence was similar in both groups (65.1% in WUS/LPS vs 57.0% in ≤6 hours, P=0.259) and no differences were found after adjustment for confounders.

Conclusions

This real-world observational study suggests that EVT may be safe and effective in patients with WUS and LPS selected using clinical-core mismatch (high NIHSS/high ASPECTS in NCCT).

Mechanical Thrombectomy in Anterior Circulation Occlusion Could Be More Effective than Medical Management Even in Low DWI-ASPECTS Patients

The purpose of this study was to investigate whether patients with low preoperative Diffusion-weighted Imaging Alberta Stroke Program Early Computed Tomography Score (DWI-ASPECTS) could benefit from mechanical thrombectomy for acute anterior circulation occlusion. This was a retrospective, non-blinded, cohort study. From September 2012 to August 2016, 83 consecutive patients of acute anterior circulation occlusion were treated with thrombectomy using second-generation devices or medical management. The DWI-ASPECTS was scored after the first MRI. Patient characteristics and clinical outcomes were compared between the treatment groups. Significant dependence was defined as a modified Rankin scale score ≥3 at 90 days. As a result, 33 patients underwent mechanical thrombectomy and 50 received medical management. In the mechanical thrombectomy group, the variable of lower DWI-ASPECTS (5, 4–6 vs. 8, 7–8, P < 0.001), especially ≤6, was significantly associated with poor prognosis. However, compared with patients of DWI-ASPECTS ≤ 6 who received medical management, there were significantly fewer patients with poor outcomes in thrombectomy (dependent in 11 of 15 vs. 23 of 23, respectively; P = 0.019). Although patients with lower pretreatment DWI-ASPECTS could benefit less from thrombectomy, their outcomes were still better than medical management. Therefore, mechanical thrombectomy could be considered in some patients with low pretreatment DWI-ASPECTS.

Thin-slice brain CT with iterative model reconstruction algorithm for small lacunar lesions detection: Image quality and diagnostic accuracy evaluation

This study was aimed to evaluate the image quality and lacunar lesion detection of thin-slice brain computed tomography (CT) images with different reconstruction algorithms, including filtered back projection (FBP), hybrid iterative reconstruction (HIR), and iterative model reconstruction (IMR) by comparison of routine slice images with FBP reconstruction. Sixty-one patients underwent noncontrast brain CT and images were reconstructed with a routine slice of 5.0 mm by FBP and thin slice of 1.0 mm by IMR, HIR, and FBP algorithms, respectively. Objective analyses included CT attenuation, noise, artifacts index of posterior cranial fossa, and contrast-to-noise ratio (CNR). Subjective analyses were performed according to overall image quality using a 5-point scale [1 (unacceptable) to 5 (excellent)]. In addition, lacunar lesion detection was compared in images with different reconstruction settings among 26 patients with lacunar lesions, with magnetic resonance imaging (MRI) as reference.Thin-slice IMR images enabled the lowest noise, artifacts index, and the best CNR. Both IMR and HIR thin-slice images enabled better scores in subjective image quality than routine slice FBP images. Moreover, both thin-slice IMR and HIR images enabled higher sensitivity and positive predictive value (PPV) in lesion detection of 35-mm lacunar lesions compared with routine slice FBP images.Thin-slice IMR images improve image quality, meanwhile yield better detection of small lacunar lesions in brain CT compared with routine slice FBP images.

A hitchhiker's guide to lesion-behaviour mapping

Lesion-behaviour mapping is an influential and popular approach to anatomically localise cognitive brain functions in the human brain. Multiple considerations, ranging from patient selection, assessment of lesion location and patient behaviour, spatial normalisation, statistical testing, to the anatomical interpretation of obtained results, are necessary to optimize a lesion-behaviour mapping study and arrive at meaningful conclusions. Here, we provide a hitchhiker's guide, giving practical guidelines and references for each step of the typical lesion-behaviour mapping study pipeline.

Reliability, Reproducibility and Prognostic Accuracy of the Alberta Stroke Program Early CT Score on CT Perfusion and Non-Contrast CT in Hyperacute Stroke

Background: Alberta Stroke Program Early CT Score (ASPECTS) assesses early ischemic change on non-contrast CT (NCCT). We hypothesised that assessing ASPECTS regions on CT Perfusion (CTP) rather than NCCT would improve inter-rater agreement and prognostic accuracy, particularly in patients presenting early after stroke onset. Methods: Ischemic stroke patients treated with intravenous alteplase from 2009 to 2014 at our institution were included in this study. Inter-rater agreement and prognostic accuracy of ASPECTS across modalities were analysed by the time between stroke onset and initial NCCT, dichotomized 1st quartile versus quartiles 2-4, referred to as epochs. ASPECTS was assessed by 2 independent raters, blinded to stroke onset time, with agreement determined by weighted kappa (κw). Prognostic accuracy for favourable outcome (modified Rankin Scale 0-2) was assessed using the receiver-operating characteristic analysis. Results: A total of 227 participants were included. There was significant time-by-CT modality interaction for ASPECTS, p < 0.0001. The inter-rater agreement of ASPECTS on NCCT significantly increased as onset to CT time increased (κw epoch 1 = 0.76 vs. κw epoch 2-4 = 0.89, p = 0.04), whereas agreement using CTP parameters was stable across epochs. Inter-rater agreement for CTP-ASPECTS was significantly higher than NCCT in early epoch: Tmax κw = 0.96, p = 0.002; cerebral blood volume (CBV) κw = 0.95, p = 0.003; cerebral blood flow (CBF) κw = 0.94, p = 0.006, with no differences in the later epochs. Prognostic accuracy of ASPECTS on NCCT in epoch 1 were (area under the ROC curves [AUC] = 0.52, 95% CI 0.48-0.56), CBV (AUC = 0.55, 95% CI 0.42-0.69, CBF (AUC = 0.58, 95% CI 0.46-0.71) and Tmax (AUC = 0.62, 95% CI 0.49-0.75), p = 0.46 between modalities. Conclusions: CTP can improve reliability when assessing the extent of ischemic changes, particularly in patients imaged early after stroke onset.

Penumbra and re-canalization acute computed tomography in ischemic stroke evaluation: PRACTISE study protocol

Rationale Multimodal imaging, including computed tomography angiography and computed tomography perfusion imaging, yields additional information on intracranial vessels and brain perfusion and can differentiate between ischemic core and penumbra which may affect patient selection for intravenous thrombolysis. Hypothesis The use of multimodal imaging will increase the number of patients receiving intravenous thrombolysis and lead to better treatment outcomes. Sample size 400 patients. Methods and design PRACTISE is a prospective, multicenter, randomized, controlled trial in which patients presenting within 4.5 h of symptom onset are randomized to either the current evidence-based imaging (NCCT alone) or additional multimodal computed tomography imaging (NCCT + computed tomography angiography + computed tomography perfusion). Clinical decisions on intravenous recombinant tissue plasminogen activator are documented. Total imaging time in both arms and time to initiation of treatment delivery in those treated with intravenous recombinant tissue plasminogen activator, is recorded. Follow-up will include brain imaging at 24 h to document infarct size, the presence of edema and the presence of intra-cerebral hemorrhage. Clinical evaluations include NIHSS score at baseline, 24 h and day 7 ± 2, and mRS at day 90 to define functional outcomes. Study outcomes The primary outcome is the proportion of patients receiving intravenous recombinant tissue plasminogen activator. Secondary end-points evaluate times to decision-making, comparison of different image processing software and clinical outcomes at three months. Discussion Multimodal computed tomography is a widely available tool for patient selection for revascularization therapy, but it is currently unknown whether the use of additional imaging in all stroke patients is beneficial. The study opened for recruitment in March 2015 and will provide data on the value of multimodal imaging in treatment decisions for acute stroke.

Automated Critical Test Findings Identification and Online Notification System Using Artificial Intelligence in Imaging

Purpose To evaluate the performance of an artificial intelligence (AI) tool using a deep learning algorithm for detecting hemorrhage, mass effect, or hydrocephalus (HMH) at non-contrast material-enhanced head computed tomographic (CT) examinations and to determine algorithm performance for detection of suspected acute infarct (SAI). Materials and Methods This HIPAA-compliant retrospective study was completed after institutional review board approval. A training and validation dataset of noncontrast-enhanced head CT examinations that comprised 100 examinations of HMH, 22 of SAI, and 124 of noncritical findings was obtained resulting in 2583 representative images. Examinations were processed by using a convolutional neural network (deep learning) using two different window and level configurations (brain window and stroke window). AI algorithm performance was tested on a separate dataset containing 50 examinations with HMH findings, 15 with SAI findings, and 35 with noncritical findings. Results Final algorithm performance for HMH showed 90% (45 of 50) sensitivity (95% confidence interval [CI]: 78%, 97%) and 85% (68 of 80) specificity (95% CI: 76%, 92%), with area under the receiver operating characteristic curve (AUC) of 0.91 with the brain window. For SAI, the best performance was achieved with the stroke window showing 62% (13 of 21) sensitivity (95% CI: 38%, 82%) and 96% (27 of 28) specificity (95% CI: 82%, 100%), with AUC of 0.81. Conclusion AI using deep learning demonstrates promise for detecting critical findings at noncontrast-enhanced head CT. A dedicated algorithm was required to detect SAI. Detection of SAI showed lower sensitivity in comparison to detection of HMH, but showed reasonable performance. Findings support further investigation of the algorithm in a controlled and prospective clinical setting to determine whether it can independently screen noncontrast-enhanced head CT examinations and notify the interpreting radiologist of critical findings. ^© RSNA, 2017 Online supplemental material is available for this article.

Imaging of cerebral ischemic edema and neuronal death

PURPOSE

In acute cerebral ischemia, the assessment of irreversible injury is crucial for treatment decisions and the patient's prognosis. There is still uncertainty how imaging can safely differentiate reversible from irreversible ischemic brain tissue in the acute phase of stroke.

METHODS

We have searched PubMed and Google Scholar for experimental and clinical papers describing the pathology and pathophysiology of cerebral ischemia under controlled conditions.

RESULTS

Within the first 6 h of stroke onset, ischemic cell injury is subtle and hard to recognize under the microscope. Functional impairment is obvious, but can be induced by ischemic blood flow allowing recovery with flow restoration. The critical cerebral blood flow (CBF) threshold for irreversible injury is ~15 ml/100 g × min. Below this threshold, ischemic brain tissue takes up water in case of any residual capillary flow (ionic edema). Because tissue water content is linearly related to X-ray attenuation, computed tomography (CT) can detect and measure ionic edema and, thus, determine ischemic brain infarction. In contrast, diffusion-weighted magnetic resonance imaging (DWI) detects cytotoxic edema that develops at higher thresholds of ischemic CBF and is thus highly sensitive for milder levels of brain ischemia, but not specific for irreversible brain tissue injury.

CONCLUSION

CT and MRI are complimentary in the detection of ischemic stroke pathology and are valuable for treatment decisions.

Acute Ischemic Stroke Therapy Overview

The treatment of acute ischemic stroke has undergone dramatic changes recently subsequent to the demonstrated efficacy of intra-arterial (IA) device-based therapy in multiple trials. The selection of patients for both intravenous and IA therapy is based on timely imaging with either computed tomography or magnetic resonance imaging, and if IA therapy is considered noninvasive, angiography with one of these modalities is necessary to document a large-vessel occlusion amenable for intervention. More advanced computed tomography and magnetic resonance imaging studies are available that can be used to identify a small ischemic core and ischemic penumbra, and this information will contribute increasingly in treatment decisions as the therapeutic time window is lengthened. Intravenous thrombolysis with tissue-type plasminogen activator remains the mainstay of acute stroke therapy within the initial 4.5 hours after stroke onset, despite the lack of Food and Drug Administration approval in the 3- to 4.5-hour time window. In patients with proximal, large-vessel occlusions, IA device-based treatment should be initiated in patients with small/moderate-sized ischemic cores who can be treated within 6 hours of stroke onset. The organization and implementation of regional stroke care systems will be needed to treat as many eligible patients as expeditiously as possible. Novel treatment paradigms can be envisioned combining neuroprotection with IA device treatment to potentially increase the number of patients who can be treated despite long transport times and to ameliorate the consequences of reperfusion injury. Acute stroke treatment has entered a golden age, and many additional advances can be anticipated.