Quantitative agreement between [(15)O]H2O PET and model free QUASAR MRI-derived cerebral blood flow and arterial blood volume.

The purpose of this study was to assess whether there was an agreement between quantitative cerebral blood flow (CBF) and arterial cerebral blood volume (CBVA) measurements by [(15)O]H2O positron emission tomography (PET) and model-free QUASAR MRI. Twelve healthy subjects were scanned within a week in separate MRI and PET imaging sessions, after which quantitative and qualitative agreement between both modalities was assessed for gray matter, white matter and whole brain region of interests (ROI). The correlation between CBF measurements obtained with both modalities was moderate to high (r(2): 0.28-0.60, P < 0.05), although QUASAR significantly underestimated CBF by 30% (P < 0.001). CBVA was moderately correlated (r(2): 0.28-0.43, P < 0.05), with QUASAR yielding values that were only 27% of the [(15)O]H2O-derived values (P < 0.001). Group-wise voxel statistics identified minor areas with significant contrast differences between [(15)O]H2O PET and QUASAR MRI, indicating similar qualitative CBVA and CBF information by both modalities. In conclusion, the results of this study demonstrate that QUASAR MRI and [(15)O]H2O PET provide similar CBF and CBVA information, but with systematic quantitative discrepancies.

Accuracy and precision of pseudo-continuous arterial spin labeling perfusion during baseline and hypercapnia: a head-to-head comparison with ¹5O H2O positron emission tomography.

Measurements of the cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) provide useful information about cerebrovascular condition and regional metabolism. Pseudo-continuous arterial spin labeling (pCASL) is a promising non-invasive MRI technique to quantitatively measure the CBF, whereas additional hypercapnic pCASL measurements are currently showing great promise to quantitatively assess the CVR. However, the introduction of pCASL at a larger scale awaits further evaluation of the exact accuracy and precision compared to the gold standard. (15)O H2O positron emission tomography (PET) is currently regarded as the most accurate and precise method to quantitatively measure both CBF and CVR, though it is one of the more invasive methods as well. In this study we therefore assessed the accuracy and precision of quantitative pCASL-based CBF and CVR measurements by performing a head-to-head comparison with (15)O H2O PET, based on quantitative CBF measurements during baseline and hypercapnia. We demonstrate that pCASL CBF imaging is accurate during both baseline and hypercapnia with respect to (15)O H2O PET with a comparable precision. These results pave the way for quantitative usage of pCASL MRI in both clinical and research settings.

Age determination of subdural hematomas: survey among radiologists.

Abusive head trauma is a severe form of child abuse. One important diagnostic finding is the presence of a subdural hematoma. Age determination of subdural hematomas is important to relate radiological findings to the clinical history presented by the caregivers. In court this topic is relevant as dating subdural hematomas can lead to identification of a suspect. The aim of our study is to describe the current practice among radiologists in the Netherlands regarding the age determination of subdural hematomas in children. This is a cross-sectional study, describing the results of an online questionnaire regarding dating subdural hematomas among pediatric and neuro-radiologists in the Netherlands. The questionnaire consisted of sociodemographic questions, theoretical questions and eight pediatric cases in which the participants were asked to date subdural hematomas based on imaging findings. Fifty-one out of 172 radiologists (30 %) filled out the questionnaire. The percentage of participants that reported it was possible to date the subdural hematoma varied between 58 and 90 % for the eight different cases. In four of eight cases (50 %), the age of the subdural hematoma as known from clinical history fell within the range reported by the participants. None of the participants was "very certain" of their age determination. The results demonstrate that there is a considerable practice variation among Dutch radiologists regarding the age determination of subdural hematomas. This implicates that dating of subdural hematomas is not suitable to use in court, as no uniformity among experts exists.

Mapping the hemodynamic response in human subjects to a dopaminergic challenge with dextroamphetamine using ASL-based pharmacological MRI.

Pharmacological magnetic resonance imaging (phMRI) maps the neurovascular response to a pharmacological challenge and is increasingly used to assess neurotransmitter systems. Here we investigated the hemodynamic response to a dopaminergic (DAergic) challenge with dextroamphetamine (dAMPH) in humans using arterial spin labeling (ASL) based phMRI. Twelve healthy male subjects aged 21.0years (±1.5) were included. We used a pseudo-continuous ASL sequence (40min) to quantify cerebral blood flow (CBF) and started dAMPH infusion (0.3mg/kg) after 10min. On another day, we measured baseline dopamine D2/3 receptor availability with [(123)I]IBZM single photon emission computed tomography (SPECT). Baseline measures on mood and impulsivity and subjective behavioral responses to dAMPH were obtained. CBF response was corrected for cardiovascular effects using an occipital cortex mask for internal reference. Corrected CBF (sCBF) was analyzed using ROI-based and voxel-based analysis, in addition to independent component analysis (ICA). CBF data was correlated to D2/3 receptor availability and behavioral measures. Subjects reported experiencing euphoria following dAMPH administration. In the striatum sCBF significantly increased, as demonstrated by all three analysis methods. Voxel-based analysis and ICA also showed increased sCBF in the thalamus, anterior cingulate and cerebellum. Decreased sCBF was observed in several cortical areas, the posterior cingulated and paracingulate cortex. Apart from one ICA component, no correlations were found with sCBF changes and D2/3 receptor availability and behavioral measures. Our observations are in line with literature and provide further evidence that ASL-based phMRI with dAMPH is a promising technique to assess DAergic function in human subjects.

Correlation between EEG spectral power and cerebral perfusion in patients with acute ischemic stroke.

Dry electrode electroencephalography (EEG) has the potential to diagnose ischemic stroke in the acute phase. In the current study we determined the correlation between EEG spectral power and ischemic stroke size and location as determined by computed tomography perfusion (CTP). Dry electrode EEG recordings were performed in patients with acute ischemic stroke in the emergency room. CTP preceded the EEG recordings as part of standard imaging protocol. Infarct core volume, total hypoperfused volume and local cerebral blood flow (CBF) were estimated with CTP. Additionally, global and local EEG spectral power were determined. We used Spearman's correlation coefficients to evaluate the correlation between variables. We included 27 patients (median age 72 [IQR:69-80] years, 15/27 [56%] men). Median CTP-to-EEG time was 32 (range:8-138) minutes. Hypoperfused volumes were estimated for 12/27 (44%) patients. Infarct core volume correlated best with global delta power (ρ = 0.76, p < 0.01), total hypoperfused volume with global alpha power (ρ = -0.58, p = 0.05), and local CBF with local alpha power (ρ = 0.43, p < 0.01). We conclude that dry electrode EEG signals slow down with increasing hypoperfused volume, which could potentially be used to discriminate between small and large ischemic strokes.

Detection of patent foramen ovale in patients with ischemic stroke on prospective ECG-gated cardiac CT compared to transthoracic echocardiography.

BACKGROUND: Cardiac CT acquired during the acute stroke imaging protocol is an emerging alternative to transthoracic echocardiography (TTE) to screen for sources of cardioembolism. Currently, its diagnostic accuracy to detect patent foramen ovale (PFO) is unclear. METHODS: This was a substudy of Mind the Heart, a prospective cohort in which consecutive adult patients with acute ischemic stroke underwent prospective ECG-gated cardiac CT during the initial stroke imaging protocol. Patients also underwent TTE. We included patients < 60 years who underwent TTE with agitated saline contrast (cTTE) and assessed sensitivity, specificity, negative and positive predictive value of cardiac CT for the detection of PFO using cTTE as the reference standard. RESULTS: Of 452 patients in Mind the Heart, 92 were younger than 60 years. Of these, 59 (64%) patients underwent both cardiac CT and cTTE and were included. Median age was 54 (IQR 49-57) years and 41/59 (70%) were male. Cardiac CT detected a PFO in 5/59 (8%) patients, 3 of which were confirmed on cTTE. cTTE detected a PFO in 12/59 (20%) patients. Sensitivity and specificity of cardiac CT were 25% (95% CI 5-57%) and 96% (95% CI 85-99%), respectively. Positive and negative predictive values were 59% (95% CI 14-95) and 84% (95% CI 71-92). CONCLUSION: Prospective ECG-gated cardiac CT acquired during the acute stroke imaging protocol does not appear to be a suitable screening method for PFO due to its low sensitivity. Our data suggest that if cardiac CT is used as a first-line screening method for cardioembolism, additional echocardiography remains indicated in young patients with cryptogenic stroke, in whom PFO detection would have therapeutic consequences. These results need to be confirmed in larger cohorts.

Infarct Evolution in Patients with Anterior Circulation Large-Vessel Occlusion Randomized to IV Alteplase and Endovascular Treatment versus Endovascular Treatment Alone.

BACKGROUND AND PURPOSE: Infarct evolution after endovascular treatment varies widely among patients with stroke and may be affected by baseline characteristics and procedural outcomes. Moreover, IV alteplase and endovascular treatment may influence the relationship of these factors to infarct evolution. We aimed to assess whether the infarct evolution between baseline and follow-up imaging was different for patients who received IVT and EVT versus EVT alone. MATERIALS AND METHODS: We included patients from the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands (MR CLEAN)-NO IV trial with baseline CTP and follow-up imaging. Follow-up infarct volume was segmented on 24-hour or 1-week follow-up DWI or NCCT. Infarct evolution was defined as the follow-up lesion volume: CTP core volume. Substantial infarct growth was defined as an increase in follow-up infarct volume of >10 mL. We assessed whether infarct evolution was different for patients with IV alteplase and endovascular treatment versus endovascular treatment alone and evaluated the association of baseline characteristics and procedural outcomes with infarct evolution using multivariable regression. RESULTS: From 228 patients with CTP results available, 145 patients had follow-up imaging and were included in our analysis. For patients with IV alteplase and endovascular treatment versus endovascular treatment alone, the baseline median CTP core volume was 17 (interquartile range = 4-35) mL versus 11 (interquartile range = 6-24) mL. The median follow-up infarct volume was 13 (interquartile range, 4-48) mL versus 17 (interquartile range = 4-50) mL. Collateral status and occlusion location were negatively associated with substantial infarct growth in patients with and without IV alteplase before endovascular treatment. CONCLUSIONS: No statistically significant difference in infarct evolution was found in directly admitted patients who received IV alteplase and endovascular treatment within 4.5 hours of symptom onset versus patients who underwent endovascular treatment alone. Collateral status and occlusion location may be useful predictors of infarct evolution prognosis in patients eligible for IV alteplase who underwent endovascular treatment.

Cardiac thrombus dissolution in acute ischemic stroke: A substudy of Mind the Heart.

Background: Cardiac thrombi are an important cause of ischemic stroke but are infrequently detected on cardiac imaging. We hypothesized that this might be explained by early dissolution of these cardiac thrombi after stroke occurrence. Methods: We performed a single-center observational pilot study between November 2019 and November 2020, embedded in the larger "Mind-the-Heart" study. We included patients with AIS and a cardiac thrombus in the left atrium or ventricle (filling defect <100 Hounsfield Units) diagnosed on cardiac CT that was acquired during the initial stroke imaging protocol. We repeated cardiac CT within one week to determine if the thrombus had dissolved. Results: Five patients (four men, median age 52 years, three with atrial fibrillation and one with anticoagulation therapy at baseline) were included. Median time from symptom onset to first cardiac CT was 383 (range 42-852) minutes and median time from first to second cardiac CT was three days (range 1-7). Two patients received intravenous thrombolysis (IVT). In total, six thrombi were seen on initial CT imaging (one in the left ventricle, four in the left atrial appendage, one in the left atrium). The left atrium thrombus and one left atrial appendage thrombus had dissolved on follow-up cardiac CT, one of which was in a patient with IVT treatment. Conclusion: This pilot study illustrates that cardiac thrombi can dissolve within days of stroke occurrence both with and without IVT treatment.

Tranexamic acid to prevent operation in chronic subdural haematoma (TORCH): study protocol for a randomised placebo-controlled clinical trial.

BACKGROUND: Chronic subdural haematoma (cSDH) occurs mainly in the elderly. Surgical evacuation is effective, but in these old, often frail, patients with multi-comorbidity, surgery carries significant risks for future cognitive functioning and loss of independency. Therefore, a growing interest is noted for a non-surgical treatment with medication such as tranexamic acid (TXA). In five small retrospective series, this antifibrinolytic drug showed a beneficial effect on the spontaneous resolution of the haematoma, and with that, the necessity for surgery. METHODS: For this randomised, placebo-controlled clinical multicentre trial, all cSDH patients, over 50 years old with mild symptoms (Glasgow Coma Score (GCS) ≥ 14, modified National Institutes of Health Stroke Scale (mNIHSS) ≤ 4), a midline shift of ≤ 10 mm and in whom a primary conservative treatment is chosen, are eligible for study participation. After informed consent, 140 patients will be randomised to receive either TXA 500 mg or placebo two times daily for 28 days. The primary outcome is the necessity for surgery within 12 weeks; secondary outcomes are cSDH volume, neurological impairment (mNIHSS), falling incidents, cognitive functioning (Montreal Cognitive Assessment (MOCA)), performance in activities of daily living (Barthel and Lawton score), functional outcome (modified Rankin Scale (mRS)), quality of life (Short Form Health Survey (SF-36) and EuroQol 5-Dimension Health Survey (EQ-5D)), mortality and the use of care and health-related costs (Medical Consumption Questionnaire (iMCQ) and Productivity Cost Questionnaire (iPCQ)) at 12 weeks and 6 months. DISCUSSION: This phase III trial investigating the efficacy of TXA to prevent surgery for cSDH is the first in including patients using anticoagulants and mentally incompetent patients, since these comprise a significant part of the target population. Also, this study is one of the first to prospectively measure functional outcome and quality of life in cSDH patients. Final results of this study are expected in 2024. TRIAL REGISTRATION: Dutch Trial Registry (Nederlands Trial Register) NL6584 . Registered on 11 November 2017 ClinicalTrials.gov NCT03582293 . Registered on 11 July 2018 EU Clinical Trials Register 2017-004311-40 . Registered on 29 March 2018.

Unsupervised Deep Learning for Stroke Lesion Segmentation on Follow-up CT Based on Generative Adversarial Networks.

BACKGROUND AND PURPOSE: Supervised deep learning is the state-of-the-art method for stroke lesion segmentation on NCCT. Supervised methods require manual lesion annotations for model development, while unsupervised deep learning methods such as generative adversarial networks do not. The aim of this study was to develop and evaluate a generative adversarial network to segment infarct and hemorrhagic stroke lesions on follow-up NCCT scans. MATERIALS AND METHODS: Training data consisted of 820 patients with baseline and follow-up NCCT from 3 Dutch acute ischemic stroke trials. A generative adversarial network was optimized to transform a follow-up scan with a lesion to a generated baseline scan without a lesion by generating a difference map that was subtracted from the follow-up scan. The generated difference map was used to automatically extract lesion segmentations. Segmentation of primary hemorrhagic lesions, hemorrhagic transformation of ischemic stroke, and 24-hour and 1-week follow-up infarct lesions were evaluated relative to expert annotations with the Dice similarity coefficient, Bland-Altman analysis, and intraclass correlation coefficient. RESULTS: The median Dice similarity coefficient was 0.31 (interquartile range, 0.08-0.59) and 0.59 (interquartile range, 0.29-0.74) for the 24-hour and 1-week infarct lesions, respectively. A much lower Dice similarity coefficient was measured for hemorrhagic transformation (median, 0.02; interquartile range, 0-0.14) and primary hemorrhage lesions (median, 0.08; interquartile range, 0.01-0.35). Predicted lesion volume and the intraclass correlation coefficient were good for the 24-hour (bias, 3 mL; limits of agreement, -64-59 mL; intraclass correlation coefficient, 0.83; 95% CI, 0.78-0.88) and excellent for the 1-week (bias, -4 m; limits of agreement,-66-58 mL; intraclass correlation coefficient, 0.90; 95% CI, 0.83-0.93) follow-up infarct lesions. CONCLUSIONS: An unsupervised generative adversarial network can be used to obtain automated infarct lesion segmentations with a moderate Dice similarity coefficient and good volumetric correspondence.

Evolutionary algorithms and decision trees for predicting poor outcome after endovascular treatment for acute ischemic stroke.

Despite the large overall beneficial effects of endovascular treatment in patients with acute ischemic stroke, severe disability or death still occurs in almost one-third of patients. These patients, who might not benefit from treatment, have been previously identified with traditional logistic regression models, which may oversimplify relations between characteristics and outcome, or machine learning techniques, which may be difficult to interpret. We developed and evaluated a novel evolutionary algorithm for fuzzy decision trees to accurately identify patients with poor outcome after endovascular treatment, which was defined as having a modified Rankin Scale score (mRS) higher or equal to 5. The created decision trees have the benefit of being comprehensible, easily interpretable models, making its predictions easy to explain to patients and practitioners. Insights in the reason for the predicted outcome can encourage acceptance and adaptation in practice and help manage expectations after treatment. We compared our proposed method to CART, the benchmark decision tree algorithm, on classification accuracy and interpretability. The fuzzy decision tree significantly outperformed CART: using 5-fold cross-validation with on average 1090 patients in the training set and 273 patients in the test set, the fuzzy decision tree misclassified on average 77 (standard deviation of 7) patients compared to 83 (±7) using CART. The mean number of nodes (decision and leaf nodes) in the fuzzy decision tree was 11 (±2) compared to 26 (±1) for CART decision trees. With an average accuracy of 72% and much fewer nodes than CART, the developed evolutionary algorithm for fuzzy decision trees might be used to gain insights into the predictive value of patient characteristics and can contribute to the development of more accurate medical outcome prediction methods with improved clarity for practitioners and patients.

Impact of the COVID-19 outbreak on acute stroke care.

BACKGROUND AND PURPOSE: There are concerns that the coronavirus disease 2019 (COVID-19) outbreak negatively affects the quality of care for acute cardiovascular conditions. We assessed the impact of the COVID-19 outbreak on trends in hospital admissions and workflow parameters of acute stroke care in Amsterdam, The Netherlands. METHODS: We used data from the three hospitals that provide acute stroke care for the Amsterdam region. We compared two 7-week periods: one during the peak of the COVID-19 outbreak (March 16th-May 3th 2020) and one prior to the outbreak (October 21st-December 8th 2019). We included consecutive patients who presented to the emergency departments with a suspected stroke and assessed the change in number of patients as an incidence-rate ratio (IRR) using a Poisson regression analysis. Other outcomes were the IRR for stroke subtypes, change in use of reperfusion therapy, treatment times, and in-hospital complications. RESULTS: During the COVID-19 period, 309 patients presented with a suspected stroke compared to 407 patients in the pre-COVID-19 period (IRR 0.76 95%CI 0.65-0.88). The proportion of men was higher during the COVID-19 period (59% vs. 47%, p < 0.001). There was no change in the proportion of stroke patients treated with intravenous thrombolysis (28% vs. 30%, p = 0.58) or endovascular thrombectomy (11% vs 12%, p = 0.82) or associated treatment times. Seven patients (all ischemic strokes) were diagnosed with COVID-19. CONCLUSION: We observed a 24% decrease in suspected stroke presentations during the COVID-19 outbreak, but no evidence for a decrease in quality of acute stroke care.

Presentation outside office hours does not negatively influence treatment times for reperfusion therapy for acute ischemic stroke.

BACKGROUND: Treatment outside office hours has been associated with increased workflow times for intravenous thrombolysis (IVT) in acute ischemic stroke (AIS). Limited data suggest that this "off-hours effect" also exists for endovascular treatment (EVT). We investigated this phenomenon in a well-organized acute stroke care region in the Netherlands. METHODS: Retrospective, observational cohort study of consecutive patients with AIS who received reperfusion therapy in the Greater Amsterdam Area, consisting of 14 primary stroke centers and 1 comprehensive stroke center (IVT: 2009-2015, EVT: 2014-2017). Office hours were defined as presentation during weekdays between 8 AM and 5 PM, excluding National Festive days. Primary outcome was door-to-treatment time (door-to-needle [DNT] for IVT, door-to-groin [DGT] for EVT). For DGT, we used the door time of the first hospital. Other outcomes were in-hospital mortality, modified Rankin Scale (mRS) score at 90 days and symptomatic intracranial hemorrhage (sICH). We performed multivariable linear and logistic regression analyses and used multiple imputation to account for missing values. RESULTS: In total, 59% (2450/4161) and 61% (239/395) of patients treated with IVT and EVT, respectively, presented outside office hours. Median DNT was minimally longer outside office hours (32 vs. 30 min, p = 0.024, adjusted difference 2.5 min, 95% CI 0.7-4.2). Presentation outside office hours was not associated with a longer DGT (median 130 min for both groups, adjusted difference 7.0 min, 95% CI - 4.2 to 18.1). Clinical outcome and sICH rate also did not differ. CONCLUSION: Presentation outside office hours did not lead to clinically relevant treatment delays for reperfusion therapy in patients with AIS.

Bevacizumab and dose-intense temozolomide in recurrent high-grade glioma.

BACKGROUND: Angiogenesis inhibition is a rational treatment strategy for high-grade glioma (HGG). Combined antiangiogenic therapy and chemotherapy could be beneficial, taking advantage of different mechanisms of antitumour activity of both therapies. We carried out a phase I-II clinical trial with the combination of bevacizumab and continuous dose-intense temozolomide (TMZ) for patients with a recurrent HGG after first- or second-line treatment. PATIENTS AND METHODS: Twenty-three HGG patients were treated with bevacizumab (10 mg/kg i.v. every 3 weeks) and TMZ (daily 50 mg/m(2)), until clinical or radiological progression. Conventional and dynamic magnetic resonance imaging (MRI) were carried out on days -4, 3 and 21 and until clinical or radiological progression. RESULTS: Overall response rate (20%), 6-month progression-free survival (PFS6) (17.4%), median progression-free survival (13.9 weeks) and median overall survival (OS) (17.1 weeks) were considerably lower compared with most other studies with bevacizumab-containing regimens. The dynamic MRI parameters contrast transfer coefficient and relative cerebral blood volume decreased rapidly during the early phases of treatment, reflecting changes in vascularisation and vessel permeability but not in tumour activity. In addition, >50% of patients showed oedema reduction and a reduced shift on T1 images. CONCLUSION: Treatment with bevacizumab and TMZ is feasible and well tolerated but did not improve PFS6 and median OS.

Prediction of Outcome Using Quantified Blood Volume in Aneurysmal SAH.

BACKGROUND AND PURPOSE: In patients with SAH, the amount of blood is strongly associated with clinical outcome. However, it is commonly estimated with a coarse grading scale, potentially limiting its predictive value. Therefore, we aimed to develop and externally validate prediction models for clinical outcome, including quantified blood volumes, as candidate predictors. MATERIALS AND METHODS: Clinical and radiologic candidate predictors were included in a logistic regression model. Unfavorable outcome was defined as a modified Rankin Scale score of 4-6. An automatic hemorrhage-quantification algorithm calculated the total blood volume. Blood was manually classified as cisternal, intraventricular, or intraparenchymal. The model was selected with bootstrapped backward selection and validated with the R 2, C-statistic, and calibration plots. If total blood volume remained in the final model, its performance was compared with models including location-specific blood volumes or the modified Fisher scale. RESULTS: The total blood volume, neurologic condition, age, aneurysm size, and history of cardiovascular disease remained in the final models after selection. The externally validated predictive accuracy and discriminative power were high (R 2 = 56% ± 1.8%; mean C-statistic = 0.89 ± 0.01). The location-specific volume models showed a similar performance (R 2 = 56% ± 1%, P = .8; mean C-statistic = 0.89 ± 0.00, P = .4). The modified Fisher models were significantly less accurate (R 2 = 45% ± 3%, P < .001; mean C-statistic = 0.85 ± 0.01, P = .03). CONCLUSIONS: The total blood volume-based prediction model for clinical outcome in patients with SAH showed a high predictive accuracy, higher than a prediction model including the commonly used modified Fisher scale.

Comparing Morphology and Hemodynamics of Stable-versus-Growing and Grown Intracranial Aneurysms.

BACKGROUND AND PURPOSE: Aneurysm growth has been related to higher rupture risk. A better understanding of the characteristics related to growth may assist in the treatment decisions of unruptured intracranial aneurysms. This study aimed to identify morphologic and hemodynamic characteristics associated with aneurysm growth and to determine whether these characteristics deviate further from those of stable aneurysms after growth. MATERIALS AND METHODS: We included 81 stable and 56 growing aneurysms. 3D vascular models were segmented on CTA, MRA, or 3D rotational angiographic images. With these models, we performed computational fluid dynamics simulations. Morphologic (size, size ratios, and shape) and hemodynamic (inflow, vorticity, shear stress, oscillatory shear index, flow instability) characteristics were automatically calculated. We compared the characteristics between aneurysms that were stable and those that had grown at baseline and final imaging. The significance level after Bonferroni correction was P < .002. RESULTS: At baseline, no significant differences between aneurysms that were stable and those that had grown were detected (P > .002). Significant differences between aneurysms that were stable and those that had grown were seen at the final imaging for shear rate, aneurysm velocity, vorticity, and mean wall shear stress (P < .002). The latter was 11.5 (interquartile range, 5.4-18.8 dyne/cm2) compared with 17.5 (interquartile range, 11.2-29.9 dyne/cm2) in stable aneurysms (P = .001). Additionally, a trend toward lower area weighted average Gaussian curvature in aneurysms that had grown was observed with a median of 6.0 (interquartile range, 3.2-10.7 cm-2) compared with 10.4 (interquartile range, 5.0-21.2 cm-2) in stable aneurysms (P = .004). CONCLUSIONS: Morphologic and hemodynamic characteristics at baseline were not associated with aneurysm growth in our population. After growth, almost all indices increase toward values associated with higher rupture risks. Therefore, we stress the importance of longitudinal imaging and repeat risk assessment in unruptured aneurysms.

Impact of Intracranial Aneurysm Morphology and Rupture Status on the Particle Residence Time.

BACKGROUND AND PURPOSE: Aneurysm hemodynamics play an important role in aneurysm growth and subsequent rupture. Within the available hemodynamic characteristics, particle residence time (PRT) is relatively unexplored. However, some studies have shown that PRT is related to thrombus formation and inflammation. The goal of this study is to evaluate the association between PRT and aneurysm rupture and morphology. METHODS: We determined the PRT for 113 aneurysms (61 unruptured, 53 ruptured) based on computational fluid dynamic models. Virtual particles were injected into the parent vessel and followed during multiple cardiac cycles. PRT was defined as the time needed for 99% of the particles that entered an aneurysm to leave the aneurysm. Subsequently, we evaluated the association between PRT, rupture, and morphology (aneurysm type, presence of blebs, or multiple lobulations). RESULTS: PRT showed no significant difference between unruptured (1.1 seconds interquartile range [IQR .39-2.0 seconds]) and ruptured aneurysms (1.2 seconds [IQR .47-2.3 seconds]). PRT was influenced by aneurysm morphology. Longer PRTs were seen in bifurcation aneurysms (1.3 seconds [IQR .54-2.4 seconds], P = .01) and aneurysms with blebs or multiple lobulations (1.92 seconds [IQR .94-2.8 seconds], P < .001). Four of five partially thrombosed aneurysms had a long residence time (>1.9 seconds). CONCLUSIONS: Our study shows an influence of aneurysm morphology on PRT. Nevertheless, it suggests that PRT cannot be used to differentiate unruptured and ruptured aneurysms.

Flow Patterns in Carotid Webs: A Patient-Based Computational Fluid Dynamics Study.

BACKGROUND AND PURPOSE: Carotid webs are increasingly recognized as an important cause of (recurrent) ischemic stroke in patients without other cardiovascular risk factors. Hemodynamic flow patterns induced by these lesions might be associated with thrombus formation. The aim of our study was to evaluate flow patterns of carotid webs using computational fluid dynamics. MATERIALS AND METHODS: Patients with a carotid web in the Multicenter Randomized Clinical Trial of Endovascular Treatment of Acute Ischemic Stroke in the Netherlands (MR CLEAN) were selected for hemodynamic evaluation with computational fluid dynamics models based on lumen segmentations obtained from CT angiography scans. Hemodynamic parameters, including the area of recirculation zone, time-averaged wall shear stress, transverse wall shear stress, and the oscillatory shear index, were assessed and compared with the contralateral carotid bifurcation. RESULTS: In our study, 9 patients were evaluated. Distal to the carotid webs, recirculation zones were significantly larger compared with the contralateral bifurcation (63 versus 43 mm2, P = .02). In the recirculation zones of the carotid webs and the contralateral carotid bifurcation, time-averaged wall shear stress values were comparable (both: median, 0.27 Pa; P = .30), while transverse wall shear stress and oscillatory shear index values were significantly higher in the recirculation zone of carotid webs (median, 0.25 versus 0.21 Pa; P = .02 and 0.39 versus 0.30 Pa; P = .04). At the minimal lumen area, simulations showed a significantly higher time-averaged wall shear stress in the web compared with the contralateral bifurcation (median, 0.58 versus 0.45 Pa; P = .01). CONCLUSIONS: Carotid webs are associated with increased recirculation zones and regional increased wall shear stress metrics that are associated with disturbed flow. These findings suggest that a carotid web might stimulate thrombus formation, which increases the risk of acute ischemic stroke.

Data-efficient deep learning of radiological image data for outcome prediction after endovascular treatment of patients with acute ischemic stroke.

Treatment selection is becoming increasingly more important in acute ischemic stroke patient care. Clinical variables and radiological image biomarkers (old age, pre-stroke mRS, NIHSS, occlusion location, ASPECTS, among others) have an important role in treatment selection and prognosis. Radiological biomarkers require expert annotation and are subject to inter-observer variability. Recently, Deep Learning has been introduced to reproduce these radiological image biomarkers. Instead of reproducing these biomarkers, in this work, we investigated Deep Learning techniques for building models to directly predict good reperfusion after endovascular treatment (EVT) and good functional outcome using CT angiography images. These models do not require image annotation and are fast to compute. We compare the Deep Learning models to Machine Learning models using traditional radiological image biomarkers. We explored Residual Neural Network (ResNet) architectures, adapted them with Structured Receptive Fields (RFNN) and auto-encoders (AE) for network weight initialization. We further included model visualization techniques to provide insight into the network's decision-making process. We applied the methods on the MR CLEAN Registry dataset with 1301 patients. The Deep Learning models outperformed the models using traditional radiological image biomarkers in three out of four cross-validation folds for functional outcome (average AUC of 0.71) and for all folds for reperfusion (average AUC of 0.65). Model visualization showed that the arteries were relevant features for functional outcome prediction. The best results were obtained for the ResNet models with RFNN. Auto-encoder initialization often improved the results. We concluded that, in our dataset, automated image analysis with Deep Learning methods outperforms radiological image biomarkers for stroke outcome prediction and has the potential to improve treatment selection.

A case of neonatal dural sinus malformation: clinical symptoms, imaging and neuropathological investigations.

We report a case of neonatal dural sinus malformation already visible on antenatal ultrasound. This is a rare disease entity in infants and children. Clinical diagnosis was made by demonstrating a cranial murmur on auscultation; macrocrania and signs of progressive cardiac failure. Imaging studies as cerebral ultrasound, postnatal MRI scan and MR angiography demonstrated a large dural sinus malformation originating from the sagittal sinus with extensive arteriovenous fistulae. Due to the extent of the lesion, the existing ischemic brain damage and involvement of the torcular, no therapeutic options were available and the child died of irreversible cardiac failure. The diagnosis was confirmed with autopsy. We discuss the clinical presentation, imaging and neuropathological results and relate our findings to embryological data and the existing literature.