Impact of temporal resolution on perfusion metrics, therapy decision, and radiation dose reduction in brain CT perfusion in patients with suspected stroke.

PURPOSE: CT perfusion of the brain is a powerful tool in stroke imaging, though the radiation dose is rather high. Several strategies for dose reduction have been proposed, including increasing the intervals between the dynamic scans. We determined the impact of temporal resolution on perfusion metrics, therapy decision, and radiation dose reduction in brain CT perfusion from a large dataset of patients with suspected stroke. METHODS: We retrospectively included 3555 perfusion scans from our clinical routine dataset. All cases were processed using the perfusion software VEOcore with a standard sampling of 1.5 s, as well as simulated reduced temporal resolution of 3.0, 4.5, and 6.0 s by leaving out respective time points. The resulting perfusion maps and calculated volumes of infarct core and mismatch were compared quantitatively. Finally, hypothetical decisions for mechanical thrombectomy following the DEFUSE-3 criteria were compared. RESULTS: The agreement between calculated volumes for core (ICC = 0.99, 0.99, and 0.98) and hypoperfusion (ICC = 0.99, 0.99, and 0.97) was excellent for all temporal sampling schemes. Of the 1226 cases with vascular occlusion, 14 (1%) for 3.0 s sampling, 23 (2%) for 4.5 s sampling, and 63 (5%) for 6.0 s sampling would have been treated differently if the DEFUSE-3 criteria had been applied. Reduction of temporal resolution to 3.0 s, 4.5 s, and 6.0 s reduced the radiation dose by a factor of 2, 3, or 4. CONCLUSION: Reducing the temporal sampling of brain perfusion CT has only a minor impact on image quality and treatment decision, but significantly reduces the radiation dose to that of standard non-contrast CT.

Annotation-free prediction of treatment-specific tissue outcome from 4D CT perfusion imaging in acute ischemic stroke.

Acute ischemic stroke is a critical health condition that requires timely intervention. Following admission, clinicians typically use perfusion imaging to facilitate treatment decision-making. While deep learning models leveraging perfusion data have demonstrated the ability to predict post-treatment tissue infarction for individual patients, predictions are often represented as binary or probabilistic masks that are not straightforward to interpret or easy to obtain. Moreover, these models typically rely on large amounts of subjectively segmented data and non-standard perfusion analysis techniques. To address these challenges, we propose a novel deep learning approach that directly predicts follow-up computed tomography images from full spatio-temporal 4D perfusion scans through a temporal compression. The results show that this method leads to realistic follow-up image predictions containing the infarcted tissue outcomes. The proposed compression method achieves comparable prediction results to using perfusion maps as inputs but without the need for perfusion analysis or arterial input function selection. Additionally, separate models trained on 45 patients treated with thrombolysis and 102 treated with thrombectomy showed that each model correctly captured the different patient-specific treatment effects as shown by image difference maps. The findings of this work clearly highlight the potential of our method to provide interpretable stroke treatment decision support without requiring manual annotations.

Reducing False-Positives in CT Perfusion Infarct Core Segmentation Using Contralateral Local Normalization.

BACKGROUND AND PURPOSE: The established global threshold of rCBF <30% for infarct core segmentation can lead to false-positives, as it does not account for the differences in blood flow between GM and WM and patient-individual factors, such as microangiopathy. To mitigate this problem, we suggest normalizing each voxel not only with a global reference value (ie, the median value of normally perfused tissue) but also with its local contralateral counterpart. MATERIALS AND METHODS: We retrospectively enrolled 2830 CTP scans with suspected ischemic stroke, of which 335 showed obvious signs of microangiopathy. In addition to the conventional, global normalization, a local normalization was performed by dividing the rCBF maps with their mirrored and smoothed counterpart, which sets each voxel value in relation to the contralateral counterpart, intrinsically accounting for GM and WM differences and symmetric patient individual microangiopathy. Maps were visually assessed and core volumes were calculated for both methods. RESULTS: Cases with obvious microangiopathy showed a strong reduction in false-positives by using local normalization (mean 14.7 mL versus mean 3.7 mL in cases with and without microangiopathy). On average, core volumes were slightly smaller, indicating an improved segmentation that was more robust against naturally low blood flow values in the deep WM. CONCLUSIONS: The proposed method of local normalization can reduce overestimation of the infarct core, especially in the deep WM and in cases with obvious microangiopathy. False-positives in CTP infarct core segmentation might lead to less-than-optimal therapy decisions when not correctly interpreted. The proposed method might help mitigate this problem.

Tenecteplase for Stroke at 4.5 to 24 Hours with Perfusion-Imaging Selection.

BACKGROUND: Thrombolytic agents, including tenecteplase, are generally used within 4.5 hours after the onset of stroke symptoms. Information on whether tenecteplase confers benefit beyond 4.5 hours is limited. METHODS: We conducted a multicenter, double-blind, randomized, placebo-controlled trial involving patients with ischemic stroke to compare tenecteplase (0.25 mg per kilogram of body weight, up to 25 mg) with placebo administered 4.5 to 24 hours after the time that the patient was last known to be well. Patients had to have evidence of occlusion of the middle cerebral artery or internal carotid artery and salvageable tissue as determined on perfusion imaging. The primary outcome was the ordinal score on the modified Rankin scale (range, 0 to 6, with higher scores indicating greater disability and a score of 6 indicating death) at day 90. Safety outcomes included death and symptomatic intracranial hemorrhage. RESULTS: The trial enrolled 458 patients, 77.3% of whom subsequently underwent thrombectomy; 228 patients were assigned to receive tenecteplase, and 230 to receive placebo. The median time between the time the patient was last known to be well and randomization was approximately 12 hours in the tenecteplase group and approximately 13 hours in the placebo group. The median score on the modified Rankin scale at 90 days was 3 in each group. The adjusted common odds ratio for the distribution of scores on the modified Rankin scale at 90 days for tenecteplase as compared with placebo was 1.13 (95% confidence interval, 0.82 to 1.57; P = 0.45). In the safety population, mortality at 90 days was 19.7% in the tenecteplase group and 18.2% in the placebo group, and the incidence of symptomatic intracranial hemorrhage was 3.2% and 2.3%, respectively. CONCLUSIONS: Tenecteplase therapy that was initiated 4.5 to 24 hours after stroke onset in patients with occlusions of the middle cerebral artery or internal carotid artery, most of whom had undergone endovascular thrombectomy, did not result in better clinical outcomes than those with placebo. The incidence of symptomatic intracerebral hemorrhage was similar in the two groups. (Funded by Genentech; TIMELESS ClinicalTrials.gov number, NCT03785678.).

Computer tomography perfusion patterns in iatrogenic cerebral arterial gas embolism: A retrospective cohort study.

PURPOSE: Cerebral arterial gas embolism (CAGE) occurs when air or medical gas enters the systemic circulation during invasive procedures and lodges in the cerebral vasculature. Non-contrast computer tomography (CT) may not always show intracerebral gas. CT perfusion (CTP) might be a useful adjunct for diagnosing CAGE in these patients. METHODS: This is a retrospective single-center cohort study. We included patients who were diagnosed with iatrogenic CAGE and underwent CTP within 24 h after onset of symptoms between January 2016 and October 2022. All imaging studies were evaluated by two independent radiologists. CTP studies were scored semi-quantitatively for perfusion abnormalities (normal, minimal, moderate, severe) in the following parameters: cerebral blood flow, cerebral blood volume, time-to-drain and time-to-maximum. RESULTS: Among 27 patient admitted with iatrogenic CAGE, 15 patients underwent CTP within the designated timeframe and were included for imaging analysis. CTP showed perfusion deficits in all patients except one. The affected areas on CTP scans were in general located bilaterally and frontoparietally. The typical pattern of CTP abnormalities in these areas was hypoperfusion with an increased time-to-drain and time-to-maximum, and a corresponding minimal decrease in cerebral blood flow. Cerebral blood volume was mostly unaffected. CONCLUSION: CTP may show specific perfusion defects in patients with a clinical diagnosis of CAGE. This suggests that CTP may be supportive in diagnosing CAGE in cases where no intracerebral gas is seen on non-contrast CT.

Standardizing the estimation of ischemic regions can harmonize CT perfusion stroke imaging.

OBJECTIVES: We aimed to evaluate the real-world variation in CT perfusion (CTP) imaging protocols among stroke centers and to explore the potential for standardizing vendor software to harmonize CTP images. METHODS: Stroke centers participating in a nationwide multicenter healthcare evaluation were requested to share their CTP scan and processing protocol. The impact of these protocols on CTP imaging was assessed by analyzing data from an anthropomorphic phantom with center-specific vendor software with default settings from one of three vendors (A-C): IntelliSpace Portal, syngoVIA, and Vitrea. Additionally, standardized infarct maps were obtained using a logistic model. RESULTS: Eighteen scan protocols were studied, all varying in acquisition settings. Of these protocols, seven, eight, and three were analyzed with center-specific vendor software A, B, and C respectively. The perfusion maps were visually dissimilar between the vendor software but were relatively unaffected by the acquisition settings. The median error [interquartile range] of the infarct core volumes (mL) estimated by the vendor software was - 2.5 [6.5] (A)/ - 18.2 [1.2] (B)/ - 8.0 [1.4] (C) when compared to the ground truth of the phantom (where a positive error indicates overestimation). Taken together, the median error [interquartile range] of the infarct core volumes (mL) was - 8.2 [14.6] before standardization and - 3.1 [2.5] after standardization. CONCLUSIONS: CTP imaging protocols varied substantially across different stroke centers, with the perfusion software being the primary source of differences in CTP images. Standardizing the estimation of ischemic regions harmonized these CTP images to a degree. CLINICAL RELEVANCE STATEMENT: The center that a stroke patient is admitted to can influence the patient's diagnosis extensively. Standardizing vendor software for CT perfusion imaging can improve the consistency and accuracy of results, enabling a more reliable diagnosis and treatment decision. KEY POINTS: • CT perfusion imaging is widely used for stroke evaluation, but variation in the acquisition and processing protocols between centers could cause varying patient diagnoses. • Variation in CT perfusion imaging mainly arises from differences in vendor software rather than acquisition settings, but these differences can be reconciled by standardizing the estimation of ischemic regions. • Standardizing the estimation of ischemic regions can improve CT perfusion imaging for stroke evaluation by facilitating reliable evaluations independent of the admission center.

Redefining CT perfusion-based ischemic core estimates for the ghost core in early time window stroke.

BACKGROUND AND PURPOSE: In large vessel occlusion (LVO) stroke patients, relative cerebral blood flow (rCBF)<30% volume thresholds are commonly used in treatment decisions. In the early time window, nearly infarcted but salvageable tissue volumes may lead to pretreatment overestimates of infarct volume, and thus potentially exclude patients who may otherwise benefit from intervention. Our multisite analysis aims to explore the strength of relationships between widely used pretreatment CT parameters and clinical outcomes for early window stroke patients. METHODS: Patients from two sites in a prospective registry were analyzed. Patients with LVOs, presenting within 3 hours of last known well, and who were successfully reperfused were included. Primary short-term neurological outcome was percent National Institutes of Health Stroke Scale (NIHSS) change from admission to discharge. Secondary long-term outcome was 90-day modified Rankin score. Spearman's correlations were performed. Significance was attributed to p-value ≤.05. RESULTS: Among 73 patients, median age was 66 (interquartile range 54-76) years. Among all pretreatment imaging parameters, rCBF<30%, rCBF<34%, and rCBF<38% volumes were significantly, inversely correlated with percentage NIHSS change (p<.048). No other parameters significantly correlated with outcomes. CONCLUSIONS: Our multisite analysis shows that favorable short-term neurological recovery was significantly correlated with rCBF volumes in the early time window. However, modest strength of correlations provides supportive evidence that the applicability of general ischemic core estimate thresholds in this subpopulation is limited. Our results support future larger-scale efforts to liberalize or reevaluate current rCBF parameter thresholds guiding treatment decisions for early time window stroke patients.

Preserved Corticospinal Tract Revealed by Acute Perfusion Imaging Relates to Better Outcome After Thrombectomy in Stroke.

BACKGROUND: The indication for mechanical thrombectomy (MT) in stroke patients with large vessel occlusion has been constantly expanded over the past years. Despite remarkable treatment effects at the group level in clinical trials, many patients remain severely disabled even after successful recanalization. A better understanding of this outcome variability will help to improve clinical decision-making on MT in the acute stage. Here, we test whether current outcome models can be refined by integrating information on the preservation of the corticospinal tract as a functionally crucial white matter tract derived from acute perfusion imaging. METHODS: We retrospectively analyzed 162 patients with stroke and large vessel occlusion of the anterior circulation who were admitted to the University Medical Center Lübeck between 2014 and 2020 and underwent MT. The ischemic core was defined as fully automatized based on the acute computed tomography perfusion with cerebral blood volume data using outlier detection and clustering algorithms. Normative whole-brain structural connectivity data were used to infer whether the corticospinal tract was affected by the ischemic core or preserved. Ordinal logistic regression models were used to correlate this information with the modified Rankin Scale after 90 days. RESULTS: The preservation of the corticospinal tract was associated with a reduced risk of a worse functional outcome in large vessel occlusion-stroke patients undergoing MT, with an odds ratio of 0.28 (95% CI, 0.15-0.53). This association was still significant after adjusting for multiple confounding covariables, such as age, lesion load, initial symptom severity, sex, stroke side, and recanalization status. CONCLUSIONS: A preinterventional computed tomography perfusion-based surrogate of corticospinal tract preservation or disconnectivity is strongly associated with functional outcomes after MT. If validated in independent samples this concept could serve as a novel tool to improve current outcome models to better understand intersubject variability after MT in large vessel occlusion stroke.

Quantitative Perfusion Imaging with Total-Body PET.

Recently, PET systems with a long axial field of view have become the current state of the art. Total-body PET scanners enable unique possibilities for scientific research and clinical diagnostics, but this new technology also raises numerous challenges. A key advantage of total-body imaging is that having all the organs in the field of view allows studying biologic interaction of all organs simultaneously. One of the new, promising imaging techniques is total-body quantitative perfusion imaging. Currently, 15O-labeled water provides a feasible option for quantitation of tissue perfusion at the total-body level. This review summarizes the status of the methodology and the analysis and provides examples of preliminary findings on applications of quantitative parametric perfusion images for research and clinical work. We also describe the opportunities and challenges arising from moving from single-organ studies to modeling of a multisystem approach with total-body PET, and we discuss future directions for total-body imaging.

The added value of lung perfusion scintigraphy semiquantitative measures in post-COVID patients with persistent dyspnea without pulmonary embolism.

BACKGROUND: Persistent dyspnea is frequent in post-COVID patients, even in the absence of pulmonary embolism (PE). In this scenario, the role of lung perfusion scintigraphy is unclear. The present study correlated scintigraphy-based semiquantitative perfusion parameters with chest high-resolution computed tomography (hrCT) volumetric indexes and clinical data in post-COVID patients with persistent dyspnea. RESEARCH DESIGN AND METHODS: Sixty patients (30 post-COVID and 30 not previously affected by COVID-19) with persistent dyspnea submitted to lung perfusion scintigraphy and hrCT were retrospectively recruited. Perfusion rates of the pulmonary fields and hrCT-based normalized inflated, emphysematous, infiltrated, collapsed, and vascular lung volumes were calculated. Inflammatory and coagulation biomarkers were collected. PE at imaging was an exclusion criterion. RESULTS: Compared to controls, reduced perfusion rates of the lower pulmonary fields and higher perfusion rates of the middle ones were observed in post-COVID patients, while hrCT findings were superimposable between the two groups. Perfusion rates of lower pulmonary fields were significantly associated only with abnormal lung volumes at hrCT. CONCLUSIONS: In post-COVID dyspnea without PE, lung perfusion scintigraphy may reveal a pulmonary involvement not detectable by hrCT. Post-COVID patients may show decreased perfusion rates of lower pulmonary fields in the presence of normal vascular density and markers of inflammation/coagulation.

Spatio-temporal physics-informed learning: A novel approach to CT perfusion analysis in acute ischemic stroke.

CT perfusion imaging is important in the imaging workup of acute ischemic stroke for evaluating affected cerebral tissue. CT perfusion analysis software produces cerebral perfusion maps from commonly noisy spatio-temporal CT perfusion data. High levels of noise can influence the results of CT perfusion analysis, necessitating software tuning. This work proposes a novel approach for CT perfusion analysis that uses physics-informed learning, an optimization framework that is robust to noise. In particular, we propose SPPINN: Spatio-temporal Perfusion Physics-Informed Neural Network and research spatio-temporal physics-informed learning. SPPINN learns implicit neural representations of contrast attenuation in CT perfusion scans using the spatio-temporal coordinates of the data and employs these representations to estimate a continuous representation of the cerebral perfusion parameters. We validate the approach on simulated data to quantify perfusion parameter estimation performance. Furthermore, we apply the method to in-house patient data and the public Ischemic Stroke Lesion Segmentation 2018 benchmark data to assess the correspondence between the perfusion maps and reference standard infarct core segmentations. Our method achieves accurate perfusion parameter estimates even with high noise levels and differentiates healthy tissue from infarcted tissue. Moreover, SPPINN perfusion maps accurately correspond with reference standard infarct core segmentations. Hence, we show that using spatio-temporal physics-informed learning for cerebral perfusion estimation is accurate, even in noisy CT perfusion data. The code for this work is available at https://github.com/lucasdevries/SPPINN.

Dye-free visualisation of intestinal perfusion using laser speckle contrast imaging in laparoscopic surgery: a prospective, observational multi-centre study.

INTRODUCTION: Intraoperative perfusion imaging may help the surgeon in creating the intestinal anastomoses in optimally perfused tissue. Laser speckle contrast imaging (LSCI) is such a perfusion visualisation technique that is characterized by dye-free, real-time and continuous imaging. Our aim is to validate the use of a novel, dye-free visualization tool to detect perfusion deficits using laparoscopic LSCI. METHODS: In this multi-centre study, a total of 64 patients were imaged using the laparoscopic laser speckle contrast imager. Post-operatively, surgeons were questioned if the additional visual feedback would have led to a change in clinical decision-making. RESULTS: This study suggests that the laparoscopic laser speckle contrast imager PerfusiX-Imaging is able to image colonic perfusion. All images were clear and easy to interpret for the surgeon. The device is non-disruptive of the surgical procedure with an average added surgical time of 2.5 min and no change in surgical equipment. The potential added clinical value is accentuated by the 17% of operating surgeons indicating a change in anastomosis location. Further assessment and analysis of both white light and PerfusiX perfusion images by non-involved, non-operating surgeons showed an overall agreement of 80%. CONCLUSION: PerfusiX-Imaging is a suitable laparoscopic perfusion imaging system for colon surgery that can visualize perfusion in real-time with no change in surgical equipment. The additional visual feedback could help guide the surgeons in placing the anastomosis at the most optimal site.

Computed tomography perfusion software pipelines to assess parameter maps and ischemic volumes: A comparative study.

BACKGROUND AND PURPOSE: This study was dedicated to investigating the agreement of the calculated results of two CT perfusion (CTP) postprocessing software packages, including parameter maps and ischemic volume, focusing on the infarct core volume (ICV) and penumbra volume (PV). METHODS: A retrospective collection of 235 patients with acute ischemic stroke who underwent CTP examination were enrolled. All images had been analyzed with two software pipelines, RAPID CTP and AccuCTP, and the comparative analysis was based on ICV and PV results calculated by both software packages. The agreement of parameter maps was evaluated by root mean square error and Bland-Altman analysis. The ICV and PV agreement was evaluated by intraclass correlation coefficient (ICC) and Bland-Altman analysis. The accuracy of ICV and PV based on multiple thresholds was also analyzed. RESULTS: The ICV and PV of AccuCTP and RAPID CTP show excellent agreement. The relative differences of the parameter maps were all within 10% and the Bland-Altman analysis also showed a strong agreement. From ordinary least squares fitting results, both ICV and PV had a remarkably high goodness of fit (ICV, R2 = 0.975 [p<.001]; PV, R2 = 0.964 [p<.001]). For the ICC analysis, both had high ICC scores (ICV ICC 0.984, 95% CI [confidence interval] 0.973-0.989; PV ICC 0.955, 95% CI 0.947-0.964). Furthermore, multi-threshold analysis on the basis of ICV and PV also achieved reliable analytical accuracy. CONCLUSIONS: The image analysis results of AccuCTP are in excellent agreement with RAPID CTP and can be used as an alternative analysis tool to RAPID CTP software in stroke clinical practice.

Total-Body Perfusion Imaging with [11C]-Butanol.

Tissue perfusion can be affected by physiology or disease. With the advent of total-body PET, quantitative measurement of perfusion across the entire body is possible. [11C]-butanol is a perfusion tracer with a superior extraction fraction compared with [15O]-water and [13N]-ammonia. To develop the methodology for total-body perfusion imaging, a pilot study using [11C]-butanol on the uEXPLORER total-body PET/CT scanner was conducted. Methods: Eight participants (6 healthy volunteers and 2 patients with peripheral vascular disease [PVD]) were injected with a bolus of [11C]-butanol and underwent 30-min dynamic acquisitions. Three healthy volunteers underwent repeat studies at rest (baseline) to assess test-retest reproducibility; 1 volunteer underwent paired rest and cold pressor test (CPT) studies. Changes in perfusion were measured in the paired rest-CPT study. For PVD patients, local changes in perfusion were investigated and correlated with patient medical history. Regional and parametric kinetic analysis methods were developed using a 1-tissue compartment model and leading-edge delay correction. Results: Estimated baseline perfusion values ranged from 0.02 to 1.95 mL·min-1·cm-3 across organs. Test-retest analysis showed that repeat baseline perfusion measurements were highly correlated (slope, 0.99; Pearson r = 0.96, P < 0.001). For the CPT subject, the largest regional increases were in skeletal muscle (psoas, 142%) and the myocardium (64%). One of the PVD patients showed increased collateral vessel growth in the calf because of a peripheral stenosis. Comorbidities including myocardial infarction, hypothyroidism, and renal failure were correlated with variations in organ-specific perfusion. Conclusion: This pilot study demonstrates the ability to obtain reproducible measurements of total-body perfusion using [11C]-butanol. The methods are sensitive to local perturbations in flow because of physiologic stressors and disease.

Comparison of CT Perfusion Software Packages for Thrombectomy Eligibility.

INTRODUCTION: Computed tomography perfusion (CTP) has played an important role in patient selection for mechanical thrombectomy (MT) in acute ischemic stroke. We aimed to investigate the agreement between perfusion parametric maps of 3 software packages - RAPID (RapidAI-IschemaView), Viz CTP(Viz.ai), and e-CTP(Brainomix) - in estimating baseline ischemic core volumes of near completely/completely reperfused patients. METHODS: We retrospectively reviewed a prospectively maintained MT database to identify patients with anterior circulation large vessel occlusion strokes (LVOS) involving the internal carotid artery or middle cerebral artery M1-segment and interpretable CTP maps treated during September 2018 to November 2019. A subset of patients with near-complete/complete reperfusion (expanded thrombolysis in cerebral infarction [eTICI] 2c-3) was used to compare the pre-procedural prediction of final infarct volumes. RESULTS: In this analysis of 242 patients with LVOS, RAPID and Viz CTP relative cerebral blood flow (rCBF) < 30% values had substantial agreement (ρ = 0.767 [95% confidence interval [CI] = 0.71-0.81]) as well as for RAPID and e-CTP (ρ = 0.668 [95% CI = 0.61-0.71]). Excellent agreement was seen for time to maximum of the residue function (Tmax ) > 6 seconds between RAPID and Viz CTP (ρ = 0.811 [95% CI = 0.76-0.84]) and substantial for RAPID and e-CTP (ρ = 0.749 [95% CI = 0.69-0.79]). Final infarct volume (FIV) prediction (n = 136) was substantial in all 3 packages (RAPID ρ = 0.744; Viz CTP ρ = 0.711; and e-CTP ρ = 0.600). CONCLUSION: Perfusion parametric maps of the RAPID, Viz CTP, and e-CTP software have substantial agreement in predicting final infarct volume in near-completely/completely reperfused patients. ANN NEUROL 2023;94:848-855.

Association of admission plasma glucose level and cerebral computed tomographic perfusion deficit volumes.

INTRODUCTION: Hyperglycemia in acute ischemic stroke (AIS) is frequent and associated with worse outcome. Yet, strict glycemic control in AIS patients has failed to yield beneficial outcome. So far, the underlying pathophysiological mechanisms of admission hyperglycemia in AIS have remained not fully understood. We aimed to evaluate the yet equivocal association of hyperglycemia with computed tomographic perfusion (CTP) deficit volumes. PATIENTS AND METHODS: We included 832 consecutive AIS and transient ischemic attack (TIA) patients who underwent CTP as a part of screening for recanalization treatment (stroke code) between 3/2018 and 10/2020, from the prospective cohort of Helsinki Stroke Quality Registry. Associations of admission glucose level (AGL) and CTP deficit volumes, namely ischemic core, defined as relative cerebral blood flow <30%, and hypoperfusion lesions Time-to-maximum (Tmax) >6 s and Tmax >10s, as determined with RAPID® software, were analyzed with a linear regression model adjusted for age, sex, C-reactive protein, and time from symptom onset to imaging. RESULTS: AGL median was 6.8 mmol/L (interquartile range 5.9-8.0 mmol/L), and 222 (27%) patients were hyperglycemic (glucose >7.8 mmol/L) on admission. In non-diabetic patients (643 [77%]), AGL was significantly associated with volume of Tmax. >6 s (regression coefficient [RC] 4.8, 95% confidence interval [CI] 0.49-9.1), of Tmax >10s (RC 4.6, 95% CI 1.2-8.1), and of ischemic core (RC 2.6, 95% CI 0.64-4.6). No significant associations were shown in diabetic patients. CONCLUSION: Admission hyperglycemia appears to be associated with both larger volume of hypoperfusion lesions and of ischemic core in non-diabetic stroke code patients with AIS and TIA.

Machine Learning Using Presentation CT Perfusion Imaging for Predicting Clinical Outcomes in Patients With Aneurysmal Subarachnoid Hemorrhage.

BACKGROUND. Prediction of outcomes in patients with aneurysmal subarachnoid hemorrhage (aSAH) is challenging using current clinical predictors. OBJECTIVE. The purpose of our study was to evaluate the utility of machine learning (ML) models incorporating presentation clinical and CT perfusion imaging (CTP) data in predicting delayed cerebral ischemia (DCI) and poor functional outcome in patients with aSAH. METHODS. This study entailed retrospective analysis of data from 242 patients (mean age, 60.9 ± 11.8 [SD] years; 165 women, 77 men) with aSAH who, as part of a prospective trial, underwent CTP followed by standardized evaluation for DCI during initial hospitalization and poor 3-month functional outcome (i.e., modified Rankin scale score ≥ 4). Patients were randomly divided into training (n = 194) and test (n = 48) sets. Five ML models (k-nearest neighbor [KNN], logistic regression [LR], support vector machine [SVM], random forest [RF], and category boosting [CatBoost]) were developed for predicting outcomes using presentation clinical and CTP data. The least absolute shrinkage and selection operator method was used for feature selection. Ten-fold cross-validation was performed in the training set. Traditional clinical models were developed using stepwise LR analysis of clinical, but not CTP, data. RESULTS. Qualitative CTP analysis was identified as the most impactful feature for both outcomes. In the test set, the traditional clinical model, KNN, LR, SVM, RF, and CatBoost showed AUC for predicting DCI of 0.771, 0.812, 0.824, 0.908, 0.930, and 0.949, respectively, and AUC for predicting poor 3-month functional outcome of 0.863, 0.858, 0.879, 0.908, 0.926, and 0.958. CatBoost was selected as the optimal model. In the test set, AUC was higher for CatBoost than for the traditional clinical model for predicting DCI (p = .004) and poor 3-month functional outcome (p = .04). In the test set, sensitivity and specificity for predicting DCI were 92.3% and 60.0% for the traditional clinical model versus 92.3% and 85.7% for CatBoost, and sensitivity and specificity for predicting poor 3-month functional outcome were 100.0% and 65.8% for the traditional clinical model versus 90.0% and 94.7% for CatBoost. A web-based prediction tool based on CatBoost was created. CONCLUSION. ML models incorporating presentation clinical and CTP data outperformed traditional clinical models in predicting DCI and poor 3-month functional outcome. CLINICAL IMPACT. ML models may help guide early management of patients with aSAH.

Clinical Applications of Conebeam CTP Imaging in Cerebral Disease: A Systematic Review.

BACKGROUND: Perfusion imaging with multidetector CT is integral to the evaluation of patients presenting with ischemic stroke due to large-vessel occlusion. Using conebeam CT perfusion in a direct-to-angio approach could reduce workflow times and improve functional outcome. PURPOSE: Our aim was to provide an overview of conebeam CT techniques for quantifying cerebral perfusion, their clinical applications, and validation. DATA SOURCES: A systematic search was performed for articles published between January 2000 and October 2022 in which a conebeam CT imaging technique for quantifying cerebral perfusion in human subjects was compared against a reference technique. STUDY SELECTION: Eleven articles were retrieved describing 2 techniques: dual-phase (n = 6) and multiphase (n = 5) conebeam CTP. DATA ANALYSIS: Descriptions of the conebeam CT techniques and the correlations between them and the reference techniques were retrieved. DATA SYNTHESIS: Appraisal of the quality and risk of bias of the included studies revealed little concern about bias and applicability. Good correlations were reported for dual-phase conebeam CTP; however, the comprehensiveness of its parameter is unclear. Multiphase conebeam CTP demonstrated the potential for clinical implementation due to its ability to produce conventional stroke protocols. However, it did not consistently correlate with the reference techniques. LIMITATIONS: The heterogeneity within the available literature made it impossible to apply meta-analysis to the data. CONCLUSIONS: The reviewed techniques show promise for clinical use. Beyond evaluating their diagnostic accuracy, future studies should address the practical challenges associated with implementing these techniques and the potential benefits for different ischemic diseases.