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Background: Established randomized trial-based parameters for acute ischemic stroke group patients into generic treatment groups, leading to attempts using various artificial intelligence (AI) methods to directly correlate patient characteristics to outcomes and thereby provide decision support to stroke clinicians. We review AI-based clinical decision support systems in the development stage, specifically regarding methodological robustness and constraints for clinical implementation. Methods: Our systematic review included full-text English language publications proposing a clinical decision support system using AI techniques for direct decision support in acute ischemic stroke cases in adult patients. We (1) describe data and outcomes used in those systems, (2) estimate the systems’ benefits compared with traditional stroke diagnosis and treatment, and (3) reported concordance with reporting standards for AI in healthcare. Results: One hundred twenty-one studies met our inclusion criteria. Sixty-five were included for full extraction. In our sample, utilized data sources, methods, and reporting practices were highly heterogeneous. Conclusions: Our results suggest significant validity threats, dissonance in reporting practices, and challenges to clinical translation. We outline practical recommendations for the successful implementation of AI research in acute ischemic stroke treatment and diagnosis.

Introduction Endovascular stroke treatment (EST) is commonly performed for acute basilar artery occlusion (BAO). We aimed to identify the role of the exact location of BAO in patients receiving EST regarding the stroke etiology, recanalization success and prediction of favorable clinical outcome. Methods Retrospective analysis of 191 consecutive patients treated for BAO with EST from 01/2013 until 06/2021 in a tertiary stroke center. Groups were defined according to exact location of BAO in I: proximal third, II: middle third, III: distal third and IV: tip of the basilar artery. Univariate and multivariate analyses were performed for BAO location comparing stroke etiology, recanalization result and favorable clinical outcome according to mRS 0–3 90 days after stroke onset. Results Occlusion sides types I–IV were evenly distributed (37, 36, 60 and 58 patients). Types I and II were more often associated with large artery atherosclerosis (50 vs. 10 patients, p p p p = 0.0076). The BAO site is not predicting favorable clinical outcome. Conclusion The exact basilar artery occlusion site in patients eligible for endovascular stroke treatment reflects the stroke etiology and is associated with differing recanalization success but does not predict favorable clinical outcome.

Background and AimsElderly patients, especially octogenarians, are underrepresented in recently published studies, that showed a benefit of endovascular stroke treatment (EST) for patients with acute basilar artery occlusion (BAO). We aimed to compare the clinical outcome of octogenarians with BAO and EST compared to younger patients and to identify independent outcome predictors.MethodsThis is a retrospective, single-center analysis of patients treated for BAO with EST from 01/2013 until 06/2021 in a tertiary stroke center. Octogenarians (≥ 80 years) were compared to younger patients. Study endpoint was the clinical outcome as per modified Rankin Scale (mRS) 90d after stroke onset. The study groups were compared in univariate analysis and a multivariable logistic regression analysis was performed to define independent predictors for clinical outcome.ResultsIn this study cohort, 74/191 (38.7 %) octogenarians had a higher pre-stroke mRS (Median, IQR: 2, 1 – 3 octogenarians vs. 0, 0 – 1 younger patients, p < 0.001) and a comparable NIHSS before EST (Median, IQR: 21, 8 – 34 vs. 22, 10 – 38 younger, p = 0.712). They showed a comparable mRS 90d after stroke onset (Median, IQR: 5, 2 – 6 younger vs. 5, 3 – 6 octogenarians, p = 0.194), but less often a good clinical outcome (mRS 0-2: n = 27, 23% younger vs. n = 9, 11.7% octogenarians, p = 0.004). The rate of bad clinical outcome was comparable (mRS 5-6, n = 63, 46.7% younger vs. 39, 50.6 % octogenarians, p = 0.194). Baseline NIHSS was a stable independent predictor for clinical outcome in both study groups (e.g. for bad clinical outcome: in octogenarians OR 1.04, CI 100 – 10.85, p = 0.0019, in younger OR 1.061, CI 1.027-1.098, p = 0.005)ConclusionOctogenarians with acute BAO eligible for EST are less likely to be functionally independent at 90 days after stroke onset, but the rate of death or severe handicap is comparable to younger patients. The admission NIHSS predicts clinical outcome in both age groups.

Established randomized-trial-based parameters for acute ischemic stroke care fail to consider individualized patient data, leading to attempts to support or automate treatment and diagnosis decisions using artificial intelligence methods. We review existing research, specifically regarding methodological robustness, thereby identifying constraints for clinical AI implementation. Our systematic review of clinical decision support systems (CDSS) includes full-text English language publications proposing AI-based methods for decision support in acute ischemic stroke cases in adult patients. We (a) describe data and outcomes used in those systems, (b) estimate the systems’ benefits compared to traditional stroke diagnosis and treatment, and (c) report concordance with the MINIMAR checklist. 121 studies met our inclusion criteria. 65 were included for full extraction. In our sample, utilized data sources, methods, and reporting practices were highly heterogeneous; adherence to the MINIMAR checklist was low. Our results suggest significant validity threats, dissonance in reporting practices and challenges to clinical translation. We outline practical recommendations for successful implementation of AI in acute ischemic stroke treatment and diagnosis.Ela M. Akay and Adam Hilbert contributed equally

Stroke is a major cause for death or disability. As imaging based patient stratification improves acute stroke therapy, dynamic susceptibility contrast magnetic resonance imaging (DSC-MRI) is is of major interest to image brain perfusion. However, expert-level perfusion maps require a manual or semi-manual post-processing by a medical expert making the procedure time-consuming and less standardized. Modern machine learning methods such as generative adversarial networks (GANs) have the potential to automate the perfusion map generation on an expert-level without manual validation. We propose a modified pix2pix GAN with a temporal component (temp-pix2pix-GAN) that generates perfusion maps in an end-to-end fashion. We train our model on perfusion maps infused with expert knowledge to encode it into the GANs. The performance was trained and evaluated using the structural similarity index measure (SSIM) on two datasets including acute stroke patients and patients with steno-occlusive disease. Our temp-pix2pix architecture showed high performance on the acute stroke dataset for all perfusion maps (mean SSIM 0.92-0.99) and good performance on data including patients with steno-occlusive disease (mean SSIM 0.84-0.99). While clinical validation is still necessary in future studies, our results mark an important step towards automated expert-level perfusion maps and thus, fast patient stratification.

ObjectivesAutomated CT perfusion mismatch assessment is an established treatment decision tool in acute ischemic stroke. However, the reliability of this method in patients with head motion is unclear. We therefore sought to evaluate the influence of head movement on automated CT perfusion mismatch evaluation.MethodsUsing a realistic CT brain-perfusion-phantom, 7 perfusion mismatch scenarios were simulated within the left middle cerebral artery territory. Real CT noise and artificial head movement were added. Thereafter, ischemic core, penumbra volumes and mismatch ratios were evaluated using an automated mismatch analysis software (RAPID, iSchemaView) and compared with ground truth simulated values.ResultsWhile CT scanner noise alone had only a minor impact on mismatch evaluation, a tendency towards smaller infarct core estimates (mean difference of −5.3 (−14 to 3.5) mL for subtle head movement and −7.0 (−14.7 to 0.7) mL for strong head movement), larger penumbral estimates (+9.9 (−25 to 44) mL and +35 (−14 to 85) mL, respectively) and consequently larger mismatch ratios (+0.8 (−1.5 to 3.0) for subtle head movement and +1.9 (−1.3 to 5.1) for strong head movement) were noted in dependence of patient head movement.ConclusionsMotion during CT perfusion acquisition influences automated mismatch evaluation. Potentially treatment-relevant changes in mismatch classifications in dependence of head movement were observed and occurred in favor of mechanical thrombectomy.

Despite successful recanalization of large-vessel occlusions in acute ischemic stroke, individual patients profit to a varying degree. Dynamic susceptibility-weighted perfusion and dynamic T1-weighted contrast-enhanced blood-brain barrier permeability imaging may help to determine secondary stroke injury and predict clinical outcome. We prospectively performed perfusion and permeability imaging in 38 patients within 24 h after successful mechanical thrombectomy of an occlusion of the middle cerebral artery M1 segment. Perfusion alterations were evaluated on cerebral blood flow maps, blood-brain barrier disruption (BBBD) visually and quantitatively on ktrans maps and hemorrhagic transformation on susceptibility-weighted images. Visual BBBD within the DWI lesion corresponded to a median ktrans elevation (IQR) of 0.77 (0.41–1.4) min−1 and was found in all 7 cases of hypoperfusion (100%), in 10 of 16 cases of hyperperfusion (63%), and in only three of 13 cases with unaffected perfusion (23%). BBBD was significantly associated with hemorrhagic transformation (p

BACKGROUND AND PURPOSE Arterial spin labeling (ASL) is an MRI technique to measure cerebral blood flow (CBF) without the need of exogenous contrast agents and is thus a promising alternative to the clinical standard dynamic susceptibility-weighted contrast-enhanced (DSC) perfusion imaging. Latest international guidelines encourage its application in the clinical setting. However, susceptibility-induced image distortions impair ASL with fast readout modules (eg Echo Planar Imaging, EPI; gradient and spin echo, GRASE). In the present study, we investigated the benefit of a distortion correction for ASL compared to DSC. METHODS A pulsed ASL (PASL) sequence combined with a 3D-GRASE readout at multiple inflow times (multi-TI) was used and was corrected for susceptibility distortions using a FMRIB Software Library (FSL) implemented tool TOPUP. We performed qualitative (three expert raters) and quantitative (volume of interest [VOI]-based) comparisons of ASL and DSC imaging in 13 patients with chronic steno-occlusive disease. RESULTS In the qualitative analysis, distortion correction of the images led to a strong increase in diagnostic precision of ASL compared to DSC in the anterior cerebral artery (ACA) perfusion territory, where the susceptibility artifact was most pronounced (specificity 8% vs. 75%). In the quantitative analysis, the correlation between ASL and DSC values increased for all perfusion territories with the best improvement for the ACA territory (for anterior, middle and posterior cerebral artery: ACA: rho −0.22 vs. 0.71; MCA: rho 0.58 vs. 0.76; PCA: rho 0.58 vs. 0.63). CONCLUSIONS We showed that susceptibility distortion correction strongly improves the comparability of multi-TI ASL 3D-GRASE to DSC in steno-occlusive disease. We suggest it to be implemented in ASL postprocessing routines.

Pulsed arterial spin labeling (PASL) at multiple inflow times (multi-TIs) is advantageous for the measurement of brain perfusion in patients with long arterial transit times (ATTs) as in steno-occlusive disease, because bolus-arrival-time can be measured and blood flow measurements can be corrected accordingly. Owing to its increased signal-to-noise ratio, a combination with a three-dimensional gradient and spin echo (GRASE) readout allows acquiring a sufficient number of multi-TIs within a clinically feasible acquisition time of 5 minutes. We compared this technique with the clinical standard dynamic susceptibility-weighted contrast-enhanced imaging—magnetic resonance imaging in patients with unilateral stenosis >70% of the internal carotid or middle cerebral artery (MCA) at 3 Tesla. We performed qualitative (assessment by three expert raters) and quantitative (region of interest (ROI)/volume of interest (VOI) based) comparisons. In 43 patients, multi-TI PASL-GRASE showed perfusion alterations with moderate accuracy in the qualitative analysis. Quantitatively, moderate correlation coefficients were found for the MCA territory (ROI based: r=0.52, VOI based: r=0.48). In the anterior cerebral artery (ACA) territory, a readout related right-sided susceptibility artifact impaired correlation (ROI based: r=0.29, VOI based: r=0.34). Arterial transit delay artifacts were found only in 12% of patients. In conclusion, multi-TI PASL-GRASE can correct for arterial transit delay in patients with long ATTs. These results are promising for the transfer of ASL to the clinical practice.

Introduction and hypothesis: MR-TOF angiography (magnetic resonance time of flight) offers a rapid, non-invasive assessment of the intracranial vessel status in patients with cerebrovascular diseases. As the signal of the MR-TOF is flow-dependent, we hypothesized that a quantification can predict perfusion of the respective flow territory as well as degree of proximal stenosis. Methods: Within the PEGASUS study (WHO REG-NR DRKS00003198) we performed intracranial TOF angiography and perfusion imaging with a contrast agent (DSC, dynamic susceptibility-weighted contrast-enhanced) in patients with chronic unilateral stenosis (>70%) or occlusion of the internal carotid artery. Images were acquired on a 3 Tesla MRI (TimTrio, Siemens). The TOF signal was quantified on 2D maximal intensity projections (MIPs): Regions of interest (ROIs) were placed into the M1 segment of the middle cerebral artery (MCA). A TOF ratio was calculated: relTOF[%]=ROIipsi/ROIcontra. The relative cerebral blood flow (relCBF) in the MCA territory was calculated in %. RelCBF and relTOF were correlated (Spearman). Receiver operating characteristic (ROC) analysis defined the performance of the TOF ratio to assess cortical hypoperfusion (defined as relCBF Results: In 40 patients (median 57yrs), we found a moderate correlation for relCBF and relTOF (rho: 0.52, p The ROC analysis identified a TOF ratio Conclusion: The intracranial TOF ratio is an easily accessible clinical measure to estimate distal brain perfusion and proximal vessel pathology in patients with chronic stenosis of the internal carotid artery.

Arterial spin labeling (ASL) is an MRI technique to measure cerebral blood flow (CBF) without the need of exogenous contrast agents and is thus a promising alternative to the clinical standard dynamic susceptibility-weighted contrast-enhanced (DSC) perfusion imaging. Latest international guidelines encourage its application in the clinical setting. However, susceptibility-induced image distortions impair ASL with fast readout modules (eg Echo Planar Imaging, EPI; gradient and spin echo, GRASE). In the present study, we investigated the benefit of a distortion correction for ASL compared to DSC.A pulsed ASL (PASL) sequence combined with a 3D-GRASE readout at multiple inflow times (multi-TI) was used and was corrected for susceptibility distortions using a FMRIB Software Library (FSL) implemented tool TOPUP. We performed qualitative (three expert raters) and quantitative (volume of interest [VOI]-based) comparisons of ASL and DSC imaging in 13 patients with chronic steno-occlusive disease.In the qualitative analysis, distortion correction of the images led to a strong increase in diagnostic precision of ASL compared to DSC in the anterior cerebral artery (ACA) perfusion territory, where the susceptibility artifact was most pronounced (specificity 8% vs. 75%). In the quantitative analysis, the correlation between ASL and DSC values increased for all perfusion territories with the best improvement for the ACA territory (for anterior, middle and posterior cerebral artery: ACA: rho -0.22 vs. 0.71; MCA: rho 0.58 vs. 0.76; PCA: rho 0.58 vs. 0.63).We showed that susceptibility distortion correction strongly improves the comparability of multi-TI ASL 3D-GRASE to DSC in steno-occlusive disease. We suggest it to be implemented in ASL postprocessing routines.

Introduction In brain perfusion imaging, arterial spin labeling (ASL) is a noninvasive alternative to dynamic susceptibility contrast-magnetic resonance imaging (DSC-MRI). For clinical imaging, only product sequences can be used. We therefore analyzed the performance of a product sequence (PICORE-PASL) included in an MRI software-package compared with DSC-MRI in patients with steno-occlusion of the MCA or ICA >70%. Methods Images were acquired on a 3T MRI system and qualitatively analyzed by 3 raters. For a quantitative analysis, cortical ROIs were placed in co-registered ASL and DSC images. Pooled data for ASL-cerebral blood flow (CBF) and DSC-CBF were analyzed by Spearman’s correlation and the Bland-Altman (BA)-plot. Results In 28 patients, 11 ASL studies were uninterpretable due to patient motion. Of the remaining patients, 71% showed signs of delayed tracer arrival. A weak correlation for DSC-relCBF vs ASL-relCBF (r = 0.24) and a large spread of values in the BA-plot owing to unreliable CBF-measurement was found. Conclusion The PICORE ASL product sequence is sensitive for estimation of delayed tracer arrival, but cannot be recommended to measure CBF in steno-occlusive disease. ASL-sequences that are less sensitive to patient motion and correcting for delayed blood flow should be available in the clinical setting.

Introduction Magnetic resonance imaging (MRI) using field strengths up to 3 Tesla (T) has proven to be a powerful tool for stroke diagnosis. Recently, ultrahigh-field (UHF) MRI at 7 T has shown relevant diagnostic benefits in imaging of neurological diseases, but its value for stroke imaging has not been investigated yet. We present the first evaluation of a clinically feasible stroke imaging protocol at 7 T. For comparison an established stroke imaging protocol was applied at 3 T. Methods In a prospective imaging study seven patients with subacute and chronic stroke were included. Imaging at 3 T was immediately followed by 7 T imaging. Both protocols included T1-weighted 3D Magnetization-Prepared Rapid-Acquired Gradient-Echo (3D-MPRAGE), T2-weighted 2D Fluid Attenuated Inversion Recovery (2D-FLAIR), T2-weighted 2D Fluid Attenuated Inversion Recovery (2D-T2-TSE), T2* weighted 2D Fast Low Angle Shot Gradient Echo (2D-HemoFLASH) and 3D Time-of-Flight angiography (3D-TOF). Results The diagnostic information relevant for clinical stroke imaging obtained at 3 T was equally available at 7 T. Higher spatial resolution at 7 T revealed more anatomical details precisely depicting ischemic lesions and periinfarct alterations. A clear benefit in anatomical resolution was also demonstrated for vessel imaging at 7 T. RF power deposition constraints induced scan time prolongation and reduced brain coverage for 2D-FLAIR, 2D-T2-TSE and 3D-TOF at 7 T versus 3 T. Conclusions The potential of 7 T MRI for human stroke imaging is shown. Our pilot study encourages a further evaluation of the diagnostic benefit of stroke imaging at 7 T in a larger study.

BACKGROUND AND PURPOSE: In acute stroke, the DWI-FLAIR mismatch allows for the allocation of patients to the thrombolysis window (