ACUTE ISCHEMIC STROKE
There are 20 studies which deals with application of Artificial Intelligence and machine learning models in modalities like detection, outcome prediction and risk prediction associated with Acute Ischemic Stroke [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], Table 3.
Outcome prediction
Yu Bai et al in their study compared the long-term clinical outcome in VR-based limb rehabilitation versus traditional drug therapy in stroke patients, the study found a beneficial effect on AI-based technology [9]. Jacob R Morey et al. in another study studied the effects of Viz application in decreasing the time to treatment in LVO AIS patients, they found that a significant reduction in time was for response initiation accompanied by fewer variations[10]. The mean door-to-skin puncture time was also reduced following post-viz implementation, although the results were not statistically significant. Dougho Park et al. in their study used different machine learning models for screening the risk of aspiration in patients hospitalized with acute stroke which yielded beneficial and practical results [11]. Using similar models Kai Wang et al developed a similar model for the prediction of stroke recurrence within one year in AIS patients, the study implied that the Random forest (RF) model is the most accurate one to predict recurrence [14]. Takeshi Imura et al. in their study assessed the likelihood of home discharge following inpatient rehabilitation by taking into account numerous functional and environmental factors using CART models, observed that for identifying home discharge, the CART model that included fundamental data, functional parameters, and environmental factors had the highest accuracy [22]. The analysis found the first single discriminator for home discharge as FIM dressing of the upper body. Martin Bretzner et al. used the ElasticNet model to extract information regarding relative brain age and comparing with chronological age to predict the functional outcomes of stroke [23]. The study observed greater relative brain age (RBA), a marker of older-appearing brains, was linked to an enhancement of cardiovascular risk factors and less favourable functional outcomes following stroke. Jinhao Lyu et al. studied collateral-core ratio (CCR) to predict clinical outcomes (XGBoost) using patient features, assessing the significance of variables, and interpreting model predictions (SHAP), found that compared to the model without CCR, CCR had a greater discriminatory ability in predicting unfavorable outcomes [26]. Lohit Velagapudi et al. (6) utilized the scikit-learn package in Python to investigate the efficacy of supervised machine-learning algorithms in predicting first-pass reperfusion and conducting feature analysis in patients undergoing mechanical thrombectomy [12]. The study revealed that the Random Forest and Support Vector Machine (SVM) models achieved accuracies of 67.1%, outperforming the logistic regression model, which attained an accuracy of 65.8%. According to the Random Forest model, the top five predictors of first-pass reperfusion were aspiration, hyperlipidemia, hypertension, utilization of a stent retriever, and the duration between symptom onset and catheterization.
Detection
Yahav-Dovrat in their study implemented the Viz LVO algorithm to detect occlusions from the ICA terminus to Sylvian fissure but the system showed suboptimal sensitivity, which prevents it from being used as a diagnostic tool [8].
Tatsat R Patel et al. in their study used multivariate machine learning models to predict successful outcomes for ADAPT in middle cerebral artery (MCA) stroke using pre-treatment imaging metrics and found the logistic regression model achieved the highest accuracy (74.2%) in the testing cohort [15]. Michelle Livne et al. studied high-performance Vessel Segmentation Using Deep Learning Model U-Net in Patients With Cerebrovascular Disease [16]. The study found that both the complete and the reduced architecture produced good performance from the U-net versions also, the visual study showed that large vessels performed exceptionally well and tiny vessels adequately. In a small number of cases, pathologies such as cortical laminar necrosis and a rete mirabile caused poor segmentation performance. Jia You et al. studied the ability of the suggested Dissimilar-Siamese-U-Net (DSU-Net) model to autonomously segment the hyperdense middle cerebral artery sign (HMCAS) from non-contrast computed tomography (NCCT) scans of the head [19]. Results show that the proposed DSU-Net outperforms the baseline U-Net and numerous state-of-the-art models for clinical practice and offers a fresh strategy for HMCAS automatic segmentation. JunHua Liao et al. compared the performance in aneurysm detection of the developed ML model with that of 3 existing frameworks, findings suggest the performance of the frameworks can be enhanced by adding more geographical and temporal information [21]. As a result, when compared to the other frameworks, the bi-input+RetinaNet+C-LSTM framework performed the best. Our research shows how our method can help doctors identify cerebral aneurysms on 2D DSA pictures. Stavros Matsoukas et al assessed the precision of AI software in a three-tiered multihospital stroke network in real life [12]. The study found that accuracy metrics support Viz LVO as a useful adjunct tool in stroke diagnostics.
Risk prediction
Hidehisa Nishi et al. used the gradient boosting tree algorithm to predict the risk of cerebral infarction in patients with atrial fibrillation and reported that their machine learning model had a higher predictive accuracy than the CHADS2 and CHA2DS2-VASc risk scores [7]. Sunil A Sheth et al. used DeepSymNet to evaluate large vessel occlusion (LVO) and ischemic core volume in patients using a widely available modality, computed tomography angiogram (CTA) [13]. These findings show that CTA may contain the data necessary to perform neuroimaging evaluation for endovascular therapy with accuracy comparable to that of sophisticated imaging modalities, and that machine learning can automate the analysis. Hidehisa Nishi et al. compared the technique with previously created pretreatment scoring systems to predict the clinical outcome of large vessel occlusion (LVO) before endovascular therapy. They reported that the clinical outcomes of patients with anterior circulation LVO undergoing mechanical thrombectomy can be predicted more accurately by machine learning approaches leveraging numerous pretreatment clinical characteristics, as opposed to previously developed pretreatment scoring techniques [7]. Yoonjae Chung et al. studied the utilization of optical diffraction tomography (ODT) and deep learning (DL), automated the process of histologically quantifying the composition of thrombi reported that this method will make it possible to quickly and quantitatively assess the makeup of blood clots and, speeding up preclinical research and the detection of cardiovascular disorders [18]. Kai Wang et al. explored the predictors of death in acute ischemic stroke (AIS) patients within 1 year based on machine learning (ML) algorithms and found that clinicians may use the network calculator established in this study, which is based on the XGB model, to assist them make more individualized and logical treatment decisions [20]. Pum-Jun Kim et al. performed a binary logistic regression (BLR) and association rule mining (ARM) to analyze the data and investigate the relationship between obesity and stroke outcomes found that at three months, the outcomes of patients with acute ischemic stroke (AIS) are improved by obesity [25]. Obesity had a favorable effect on the result, according to the binary logistic regression (BLR) study. In addition, the association rule mining (ARM) study showed that patients with obesity who had positive outcomes also had mild stroke severity and a younger age.
INTRACRANIAL ANEURYSMS
After screening, we identified 21 studies related to the management of Intracranial Aneurysm (ICA) [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44], [45], [46]. They consisted of eleven studies on diagnosing ICA [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], one study on treatment outcomes [38], nine studies on risk assessment [39], [40], [41], [42], [43], [44], [45], [47], and one study on prediction of post procedural complications [46], Table 4.
Diagnosis of ICAs and Vessel Segmentation
Ou C et al. developed a cross-scale dual-path transformer module for diagnosing ICA in patients that achieved 100% accuracy in parent artery classification and accurate morphology measurement [27]. In another study by Ou C et al., a PyRadiomics module used in ICA patients indicated a difference in radiomic signatures between ruptured and unruptured aneurysms [28]. Wang J et al. and Liu X et al. both used a 3D convolutional neural network (CNN) model which achieved a high sensitivity in automated detection of ICAs, with the later study demonstrating a positive predictive value for detection and segmentation of medium and large sized ICAs [29], [30]. Duan H et al. proposed a 2 stage CNN architecture to detect ICA on 2D-DSA images which was faster and more accurate than existing models [31]. Jin H et al. developed a fully automated detection and segmentation deep neural network-based framework, for evaluation and contouring ICA from 2D+time digital subtraction angiography (DSA) sequences which successfully detected 89.3% ICAs with a patient level sensitivity of 97.7% [32]. Benvenuti L et al., used volume rendered helical computed tomographic (CT) angiographic data sets by use of a surgical navigation technology reported a time- and cost-effective method of performing automated 3D volume rendering useful in emergency cases. The model detected precise location and anatomic features of the ICA [33]. You W et al. developed a 3D-Unet Algorithm for aneurysm detection and segmentation. The preliminary results of this study indicate a great potential for the use of AI in treatment of ICAs [34]. Poppenberg KE et al. constructed prediction models using Least Absolute Shrinkage and Selection Operator (LASSO) selected transcripts from Neutrophil RNA sequencing. Models trained using these transcripts had maximum accuracy of 90% in predicting the presence of unruptured ICAs [35]. Su J et al. developed a machine learning model based on a metabolic biomarker panel consisting of lactate, glutamine, homoarginine, and 3-methylglutaconic acid levels which displayed satisfactory diagnostic and risk assessment availability [36]. Veeturi SS et al studied the relationship between hemodynamics and pathobiology of ICA using machine learning which indicated that elevated wall shear stress was associated with thin regions of ICA wall [37].
Treatment of ICAs
Liu C. et al. developed an AI algorithm to automatically generate 3D microcatheters using data from 3D rotational angiography and digital imaging and communications in medicine (DICOM). Thirty patients successfully completed the procedure without perioperative complications with a satisfactory stability of the microcatheter [38].
Risk Assessment
Heo J.et al. developed a model using several algorithms and compared them. The XGB model displayed best AI risk prediction in patients at risk of developing ICAs [39]. In a similar study conducted by Ou C et al., the XGB model displayed superior results compared to LR model and a PHASES score method [47]. In another study, Ou C et al. tested the feasibility of the automated machine learning (AutoML) to develop high-quality ML models for risk prediction. The AutoML derived ML model displayed better performance compared to statistical and manually trained models [40]. Li P et al. proposed an end-to-end deep learning model, a multiscale 3D CNN that resulted in 10-15% improvement in accuracy of rupture status prediction [41]. Liu J et al. used a two-layer feed-forward artificial neural network (ANN) which resulted in an overall prediction accuracy of 94.8% in anterior communicating artery (ACOM) aneurysms [42]. Shiraz Bhurwani MM et al. used Deep Neural Networks (DNNs) and Angiographic Parametric Imaging to predict ICA occlusion by resulting in an average prediction accuracy of 62.5%,70.8%, and 77.9% for the un-normalized, normalized, and relative subgroups. It demonstrated the feasibility of using this model in pre- and post-operative imaging [43]. Tong X et al. used machine learning-based cluster analysis for discriminating the risk of rupture of small multiple ICAs. The algorithm was able to identify three distinct clusters with variable subarachnoid hemorrhage risks [44]. Lu T et al. used a weighted gene co-expression network analysis (WGCNA) and machine learning integrative approach to conduct risk assessment. A four-gene machine learning-derived gene signature (MLDGS) was used. This signature identified patients with high risk of aneurysm rupture [45].
Prediction of Periprocedural Complications
Tian Z et al. developed a prediction model using machine learning to investigate periprocedural complications using artificial neural network, random forest (RF), and logistic regression (LR) algorithms [46]. ANN and RF models deliver satisfactory performance, indicating that ML is a valuable tool for prediction of perioperative complications after endovascular treatment for unruptured ICAs.
Hemorrhage
Nawabi et al. (1) used machine learning algorithms to examine non-enhanced CT scans of individuals with acute intracerebral haemorrhage (ICH) [48]. Comparable to multidimensional clinical grading systems, machine learning-based evaluation of quantitative high-end picture features was able to predict functional outcome. A statistically significant improvement in AUC resulted from the combination of traditional scores with picture characteristics. Tang et. al. similarly used the ML model to predict hematoma expansion in intracerebral hemorrhage (ICH) patients , the study concluded that Deep learning technology in this study can accurately classify more than 90% of hematomas with or without enlargement, which is superior to existing approaches based solely on clinical factors [49]. From non-contrast CT scan images, deep learning technologies may be able to forecast hematoma expansion favourably. Park et al. examined the potential use of near-infrared spectroscopy (NIRS) to detect delayed cerebral ischemia (DCI) in patients with subarachnoid haemorrhage (SAH) [50]. The study found that although changes in NIRS were not statistically significant, they tended to produce greater diagnostic accuracy than transcranial Doppler ultrasonography (TCD). Real-time DCI detection can be accomplished with NIRS. Duan et al. suggested a CNN-based architecture to automatically identify cerebral aneurysms from 2D-DSA images [31]. The outcomes showed that, in comparison to the previous research studies of traditional DIP approaches, our proposed two-stage CNN-based architecture was both more accurate and quicker. Overall, our study provides evidence that utilising CNN, it is possible to help medical professionals find cerebral aneurysms on DSA pictures. Rangaraj et.al. used a single pipeline of a multi-task model is proposed for the segmentation and risk assessment of haemorrhages from beginning to end [51]. Hu et. al. used LR and ML models and assess their ability to predict delayed cerebral ischemia (DCI) following aneurysmal subarachnoid haemorrhage (aSAH) [52]. This multicenter investigation discovered that a number of ML techniques, in particular RF, outperformed traditional LR. In addition, a web-based predictor tool based on the RF model was created to locate patients at high risk for DCI following SAH and enable prompt therapies.
AV malformation
Hong et al. in their study YOLOv5 and YOLOv8 algorithms for detecting brain arteriovenous malformations in U-Net and U-Net++ models and differentiating its nidus in MR Angiography [53]. The outcomes demonstrated that pretraining and augmentation significantly improved the outcomes in YOLO model.
Thrombosis
Yang et. al. used a deep learning (DL) model algorithm for detection of cerebrovascular thrombosis in the routine MRI done as per standard protocol [52]. The study was done among 392 participants which included 294 patients with CVT and 98 without CVT. These patients were divided into two groups: the test set consisting of human intervention and the development set using ML. With high sensitivity and specificity, the CVT-detected DL algorithm shown here improved diagnostic performance of standard brain magnetic resonance imaging, offering a potential method for identifying CVT. While Nishi et al.(2) analyzed the effectiveness of DL in predicting clinical outcomes for patients with major artery blockage from pretreatment diffusion-weighted image data [54].The convolutional neural network-based deep learning model used encoder-decoder architecture to segregate ischemic lesions, this model automatically extracted high-level feature maps in its middle layers and used their data to predict the clinical outcome. The deep learning model was able to extract more predictive data from pretreatment neuroimaging data than the conventional neuroimaging biomarkers.
Moyamoya Disease
Akiyama Y et al. used a deep-learning algorithm on T-2 weighted MRI images for diagnosing moyamoya disease. The algorithm was able to distinguish between moyamoya disease, atherosclerosis, and control group in basal cistern, basal ganglia, and centrum semiovale with an accuracy of 92.8%, 84.8%, and 87.8% respectively [55]. Chen Z et al. utilized six different machine learning methods to build the models and XGBoost, Logistic Regression (LR), and Support vector machine (SVM) models were used to determine risk of hemorrhage in patients with moyamoya disease. XGBoost model had the greatest area under the curve (0.874) and was determined to be a potential model for efficiently analyzing risk of hemorrhage [56].
Artery Stenosis
Machine learning models were developed and validated by Yeh CY et al. for classifying stenosis based on hemodynamic features. For Extracranial Carotid Doppler (ECCD), the random forest model performed better compared to the logistic regression model, with the predictive accuracy of the former being between 0.85 and 1. For Transcranial Doppler (TCD), the accuracy of random forest models to predict stenosis ranged from 0.67 to 0.86. The study thus indicated that machine learning-based models accurately classify artery stenosis [57].
Risk of Bias:The quality assessment of the findings of the included studies is summarised in figures 2 and 3.
Based on the ROBINS-I assessment, most studies appear to have a “low” risk of bias, with most of the domains receiving the maximum number of stars. However, as with any assessment tool, this is a rough adaptation of the ROBINS-I for non-randomised studies of interventions, and a more detailed assessment may uncover additional sources of bias.