CTA Images Research Articles

Image fusion guidance for left subclavian artery in situ fenestration during thoracic endovascular repair.

To evaluate the feasibility and clinical benefit of utilizing image fusion for thoracic endovascular repair (TEVAR) with in situ fenestration (ISF-TEVAR). Between January 2020 and December 2020, we prospectively collected 18 consecutive cases with complex thoracic aortic lesions who underwent image fusion guided ISF-TEVAR. As a control group, 18 patients were collected from historical medical records from June 2019 to December 2019. The fusion group involved the use of 3D fusion of CTA and fluoroscopic images for real-time 3D guidance, and the control group involved the use of only regular fluoroscopic images for guidance. The total contrast medium volume, hand-injected contrast medium volume, overall operative time, radiation dose and fluoroscopy time were compared between the two groups. Accuracy was measured based on preoperative CTA and intraoperative digital subtraction angiography. 3D fusion imaging guidance was successfully implemented in all patients in the fusion group. Hand-injected contrast medium volume and overall operative time were significantly lower in the fusion group than in the control group (p = .028 and p = .011). Compared with the control group, the fusion group showed a significant reduction in time and radiation dose-area product (DAP) for fluoroscopy (p = .004 and p = .010). No significant differences in total radiation dose (DAP) or total contrast medium volume were observed (p = .079 and p = .443). Full accuracy was achieved in 8 cases (44%), with a mean deviation of 2.61mm ± 3.1 (range 0.0-8.4mm). 3D image fusion for ISF-TEVAR was associated with a significant reduction in hand-injected contrast medium, time and radiation exposure for fluoroscopy and overall operative time. The image fusion guidance showed potential clinical benefits towards improved treatment safety and accuracy for complex thoracic endovascular interventions.

Danger Zones of the Gluteal Anatomy: Improving the Safety Profile of the Gluteal Fat Grafting

IntroductionKnowledge of the vascular anatomy is critical to performing safe gluteal surgery. To date, only the course of the main blood vessels within the muscles has been outlined. These findings are based on MRI and CTA images that do not conform to a topographically standardized and normalized probability distribution.ObjectivesThe aim of this study was to develop a three-dimensional mapping of the gluteal zones of high vascular density in relation to anatomical landmarks.Materials and MethodsThis single-center retrospective cohort analysis comprised all consecutive patients who underwent cone-beam computed tomography (CBCT) scans between January 2016 and October 2021. The location of blood vessels in the gluteal region was allometrically normalized in relation to anatomical landmarks. Moreover, the caliber and area of the blood vessels were assessed.ResultsCBCT scans of 32 patients with an average age of 64 ± 12 years (range 34–87 years) were included. Fifty-three percent were female. The median [IQR] caliber of the intramuscular gluteal vessels was 1.47 [1.15–1.88] mm, significantly greater than that of the subcutaneous vessels 1.09 [0.72–1.44] mm (p < 0.001). Vascular density was higher intramuscularly, as 4.5% of the area of the muscle was occupied by blood vessels, as opposed to 0.3% in the adipose tissue.ConclusionThe analysis of the CBCT scans showed a higher vascular density and larger vessels intramuscularly. We, therefore, recommend the injection of autologous fat merely to the subcutaneous plane.Level of Evidence II This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266.

CTA and 4D flow MRI dynamic images of a patient with right PT. The CT angiography reveals that the patient has only SSWD without JBWD. The 4D flow MRI demonstrates the vortex flow at the upper curve of the SS and JB.

CTA and 4D flow MRI dynamic images of a patient with right PT. The CT angiography reveals that the patient has only SSWD without JBWD. The 4D flow MRI demonstrates the vortex flow at the upper curve of the SS and JB.

CTA and 4D flow MRI dynamic images of a patient with right PT. The CTA reveals that the patient has only JBWD without SSWD. The 4D flow MRI demonstrates the vortex flow at the JB.

CTA and 4D flow MRI dynamic images of a patient with right PT. The CTA reveals that the patient has only JBWD without SSWD. The 4D flow MRI demonstrates the vortex flow at the JB.

Deep learning and machine learning predictive models for neurological function after interventional embolization of intracranial aneurysms.

The objective of this study is to develop a model to predicts the postoperative Hunt-Hess grade in patients with intracranial aneurysms by integrating radiomics and deep learning technologies, using preoperative CTA imaging data. Thereby assisting clinical decision-making and improving the assessment and prognosis of postoperative neurological function. This retrospective study encompassed 101 patients who underwent aneurysm embolization surgery. 851 radiomic features were extracted from CTA images. 512 deep learning features are extracted from last layer of ResNet50 deep convolutional neural network model. The feature screening process pipeline encompassed intraclass correlation coefficient analysis, principal component analysis, U test, spearman correlation analysis, minimum redundancy maximum relevance algorithm and Lasso regression, to identify features most correlated with postoperative Hunt-Hess grading. In the model construction phase, three distinct models were constructed: radiomics feature-based model (RSM), deep learning feature-based model (DLM), and deep learning-radiomics feature fusion model (DLRSCM). The study also calculated the radiomics score and combined it with clinical data to construct a Nomogram for predictive modeling. DLM, RSM and DLRSCM model was constructed by 9 base algorithms and 1 ensemble learning algorithm - Stacking ensemble model. Model performance was evaluated based on the area under the Receiver Operating Characteristic (ROC) curve (AUC), Matthews Correlation Coefficient (MCC), calibration curves, and decision curves analysis. 5 significant radiomic feature and 4 significant deep learning features were obtained through the feature selection process. These features were utilized for model construction. Bootstrap resampling method was used for internal validation of the models. In terms of model evaluation, the DLM model, the stacking ensemble algorithm results achieved an AUC of 0.959 and MCC of 0.815. In the RSM model, the stacking ensemble model AUC was 0.935 and MCC was 0.793. The stacking ensemble model in DLRSCM outperformed others, with an AUC of 0.968 and MCC of 0.820. Results indicated that the ANN performed optimally among all base models, while the stacked ensemble learning model exhibited the highest predictive performance. This study demonstrates that the combination of radiomics and deep learning is an effective approach to predict the postoperative Hunt-Hess grade in patients with intracranial aneurysms. This holds significant value in the early identification of postoperative neurological complications and in enhancing clinical decision-making.

CTA Supplemented by CTP Increases Interrater Reliability and Endovascular Treatment Use in Patients with Aneurysmal SAH.

Cerebral vasospasm is a common complication of aneurysmal SAH and remains a risk factor for delayed cerebral ischemia and poor outcome. The interrater reliability of CTA in combination with CTP has not been sufficiently studied. We aimed to investigate the reliability of CTA alone and in combination with CTP in the detection of cerebral vasospasm and the decision to initiate endovascular treatment. This is a retrospective single-center study including patients treated for aneurysmal SAH. Inclusion criteria were a baseline CTA and follow-up imaging including CTP due to suspected vasospasm. Three neuroradiologists were asked to grade 15 intracranial arterial segments in 71 cases using a tripartite scale (no, mild <50%, or severe >50% vasospasm). Raters further evaluated whether endovascular treatment should be indicated. The ratings were performed in 2 stages with a minimum interval of 6 weeks. The first rating included only CTA images, whereas the second rating additionally encompassed CTP images. All raters were blinded to any clinical information of the patients. Interrater reliability for per-segment analysis of vessels was highly variable (κ = 0.16-0.61). We observed a tendency toward higher interrater reliability in proximal vessel segments, except for the ICA. CTP did not improve the reliability for the per-segment analysis. When focusing on senior raters, the addition of CTP images resulted in higher interrater reliability for severe vasospasm (κ = 0.28; 95% CI, 0.10-0.46 versus κ = 0.46; 95% CI, 0.26-0.66) and subsequently higher concordance (κ = 0.23; 95% CI, -0.01-0.46 versus κ = 0.73; 95% CI, 0.55-0.91) for the decision of whether endovascular treatment was indicated. CTA alone offers only low interrater reliability in the graduation of cerebral vasospasm. However, using CTA in combination with CTP might help, especially senior neuroradiologists, to increase the interrater reliability to identify severe vasospasm following aneurysmal SAH and to increase the reliability regarding endovascular treatment decisions.

Cardiac computed tomography angiography for assessment of endothelial insufficiency of left atrial appendage disc-like occluder.

This study was performed to explore the diagnostic value of cardiac computed tomography angiography (CCTA) for endothelial insufficiency (EIS) of a left atrial appendage (LAA) disc-like occluder. Fifty-nine patients with nonvalvular atrial fibrillation who underwent placement of an LAA disc-like occluder (LAmbre; Lifetech Scientific) in our hospital were retrospectively analyzed. Patients who were found to have contrast agent entering the LAA at the 3-month postoperative CCTA examination underwent Hounsfield unit (HU) measurement of the LAA and construction of a three-dimensional(3D) model of the device for preliminary discernment between peri-device leakage (PDL) and EIS. These patients were then further examined by transesophageal echocardiography (TEE) to check for concordance with the computed tomography (CT) findings. According to the CT and TEE results, all patients were divided into the PDL group, total endothelialization group, and EIS group. The endothelial conditions and other implantation-related results were also tracked at the 6-month follow-up. All 59 patients underwent successful implantation of the LAmbre LAA closure device with no severe adverse events during the procedure. Thirty-five patients were found to have contrast agent entering the LAA at the 3-month postoperative CCTA follow-up. Based on the CT HU measurement and the 3D construction analysis results, these 35 patients were divided into the PDL group (19 patients) and the EIS group (16 patients). In the PDL group, the contrast agent infiltrated from the shoulder along the periphery of the occluder on two-dimensional (2D)CT images, and the 3D model showed a gap between the LAA and the device cover. However, the CCTA images of the other 16 patients in the EIS group showed that the contrast agent in the occluder on the 2D CTA images and 3D construction model confirmed the absence of a gap between the LAA and the device cover. TEE confirmed all of the CT results. The 6-month follow-up results showed that 14 of 19 patients in the EIS group achieved total endothelialization, whereas this number in the PDL group was only five of 19 patients. CCTA can replace TEE for examination of the endothelialization status, and patients with EIS have a higher chance of endothelialization than patients with PDL.

Evaluation of the Correlation Between Distribution Location and Vulnerability of Carotid Plaque in Patients with Transient Ischemic Attack.

To analyze the relationship among distribution location, characteristics, and vulnerability of carotid plaque using CTA and provide more information on the risk factors of carotid atherosclerotic plaque. We retrospectively analyzed the CTA images of the head and neck of 93 patients with carotid atherosclerosis. Atherosclerosis was developed in 148 carotid arteries. The plaques were divided into a high-risk plaque group and a low-risk plaque group according to whether the plaques had high-risk characteristics. The maximum cross-sectional area of carotid artery bifurcation plaque on the axial image was selected, and the cross-sectional lumen was equally divided into four 90-degree sectors, ventral side wall, dorsal side wall, inner side wall, and outer side wall. The differences in the characteristics and distribution locations of the plaques in the two groups were analyzed. The characteristic parameters of the cross-sectional plaques at the bifurcation of the carotid artery. The logistic regression analysis was used to further analyze the risk factors associated with plaque vulnerability. Among 148 carotid arteries,80 were classified as high-risk and 68 as low-risk groups. There were significant differences between the two groups concerning the thickness, length, maximum cross-sectional area, burden, and cross-sectional distribution of the plaques (P < 0.05). The plaque distribution on the dorsal side wall of the carotid bifurcation was higher in the high-risk group than that in the low-risk group (P < 0.05), dorsal side wall plaque-independent risk factors for the development of vulnerability of plaques in transient ischemic attack (TIA) patients (95% CI:1.522~6.991, P<0.05). High-risk plaques tend to occur on the dorsal side wall of the carotid bifurcation, whereas low-risk plaques tend to occur on the outer side wall of the carotid bifurcation.

Lesion Classification of Coronary Artery CTA Images Based on CBAM and Transfer Learning

Lesion Classification of Coronary Artery CTA Images Based on CBAM and Transfer Learning

AASeg: Artery-aware Global-to-Local Framework for Aneurysm Segmentation in Head and Neck CTA Images

AASeg: Artery-aware Global-to-Local Framework for Aneurysm Segmentation in Head and Neck CTA Images

Evaluation of tracheal diameter and angles in fetuses with double aortic arch using prenatal ultrasound: implications for postnatal management.

This study aims to analyze the value of prenatal ultrasound in the screening, diagnosis, and treatment of double aortic arch (DAA) malformations. A retrospective analysis was conducted on 31 fetal cases with double aortic arch anomalies over a 12-year period from June 1, 2011 to June 1, 2023. The assessment included combined measurements of fetal tracheal internal diameter Z-score and DAA pinch angle, along with ultrasonographic findings, associated anomalies, genetic abnormalities, postnatal CTA images, and long-term postnatal outcomes. Of the 31 fetal double aortic arch cases, 15 were right aortic arch dominant, 2 were left aortic arch dominant, and 14 had a balanced double arch. Genetic testing was performed on 19 cases, revealing abnormalities in 2 cases, including one Turner syndrome, and one carrier of ichthyosis gene with heterozygous deletion. Out of the total cases, 29 were delivered, and 2 cases were terminated. Prenatal diagnosis accurately identified 29 cases (29/31, 93.5%), which was confirmed by postnatal pathological anatomy, echocardiography, surgery or CTA. Fetal tracheal internal diameter Z-scores were significantly smaller in the symptomatic group than in the asymptomatic group (-1.27 ± 0.49 vs -0.68 ± 0.60, P = 0.018). The area under the curve was 0.776 (95% confidence interval, 0.593-0.960) using a tracheal internal diameter z-score cutoff of -0.73 with a sensitivity of 90% and specificity of 64.7%. The double arch pinch angle was significantly smaller in the symptomatic group than in the asymptomatic group [52.50° (38.25° to 59.00°) vs 60.00° (53.50° to 70.50°), P = 0.035]. The area under the curve was 0.744 (95% confidence interval, 0.554-0.935), and the sensitivity for determining the presence or absence of symptoms was 90% when the cutoff value was 62.5°, with a specificity of 47.1%. Fifteen cases opted for surgery with favorable surgical outcome. Prenatal echocardiography demonstrates good diagnostic efficacy for fetal double aortic arch. It is also essential to detect the presence of other underlying intra- and extracardiac malformations and genetic abnormalities. There is a significant difference in prenatal tracheal internal diameter Z-scores and double arch pinch angle between asymptomatic and symptomatic DAA infants. Symptomatic infants require early surgery, while asymptomatic infants should be monitored.

A matched-pair case control study identifying hemodynamic predictors of cerebral aneurysm growth using computational fluid dynamics.

Introduction: Initiation and progression of cerebral aneurysms is known to be driven by complex interactions between biological and hemodynamic factors, but the hemodynamic mechanism which drives aneurysm growth is unclear. We employed robust modeling and computational methods, including temporal and spatial convergence studies, to study hemodynamic characteristics of cerebral aneurysms and identify differences in these characteristics between growing and stable aneurysms. Methods: Eleven pairs of growing and non-growing cerebral aneurysms, matched in both size and location, were modeled from MRA and CTA images, then simulated using computational fluid dynamics (CFD). Key hemodynamic characteristics, including wall shear stress (WSS), oscillatory shear index (OSI), and portion of the aneurysm under low shear, were evaluated. Statistical analysis was then performed using paired Wilcoxon rank sum tests. Results: The portion of the aneurysm dome under 70% of the parent artery mean wall shear stress was higher in growing aneurysms than in stable aneurysms and had the highest significance among the tested metrics (p = 0.08). Other metrics of area under low shear had similar levels of significance. Discussion: These results align with previously observed hemodynamic trends in cerebral aneurysms, indicating a promising direction for future study of low shear area and aneurysm growth. We also found that mesh resolution significantly affected simulated WSS in cerebral aneurysms. This establishes that robust computational modeling methods are necessary for high fidelity results. Together, this work demonstrates that complex hemodynamics are at play within cerebral aneurysms, and robust modeling and simulation methods are needed to further study this topic.

Risks to predict blood loss and cranial nerve injury in carotid body paraganglioma resection

Objective: To investigate clinical and imaging parameters to predict blood loss and cranial nerve injury (CNI) following carotid body paraganglioma (CBP) resection. Methods: A retrospective examination of clinical and imaging data was conducted on 63 patients who underwent CBP resection at Xiangya Hospital of Central South University from January 2016 to December 2022, including 23 males and 40 females, aged 26-87 years old. Three imaging parameters including tumor volume, the angle of contact with the internal carotid artery (ICA), and the distance to the base of skull (DTBOS) were gauged using the IMEDPACS software on CTA and MR imaging. The predictive efficacies of age, gender, Shamblin classification, and three imaging parameters for blood loss and CNI following surgery were analysed. Logistic composite parameter models were constructed and their predictive validity was assessed. Results: Multivariate logistic regression analysis underscored that only tumor volume (OR=1.381,95%CI:1.167-1.507,P=0.001) showed significant statistical correlations with blood loss following surgery. Area under curve (AUC) values of 0.910 for receiver operating characteristic (ROC) curves showed a sensitivity of 1.000 and a specificity of 0.694. Tumor volume (OR=1.126,95%CI:1.030-1.231, P=0.002) and DTBOS (OR=0.225,95%CI:0.081-0.630,P=0.005) were significantly associated with postoperative CNI. The analysis of logistic composite model showed AUC values for tumor volume, DTBOS and combination of the two parameters were 0.858, 0.788, and 0.872, respectively. The model for combination of tumor volume and DTBOS also proved superior in predicting postoperative CNI (Z=3.106, P<0.001), with a sensitivity of 0.833 and a specificity of 0.769. Conclusions: Tumor volume and DTBOS emerged as effective predictors for blood loss and/or CNI in patients with CBP resection. Moreover, the logistic composite parameter model outclassed single-parameter models in terms of their predictive clinical value.

Comparison of conventional MR arthrography and 3D volumetric MR arthrography in detection of cartilage defects accompanying glenoid labrum pathologies.

In this study, we aimed to compare conventional and T1-weighted volumetric magnetic resonance arthrography (MRA) in the diagnosis and grading of glenoid cartilage defects that accompany labral pathologies. A total of 79 patients who were prediagnosed with labrum pathologies based on shoulder magnetic resonance imaging (MRI) had MRA and CTA between December 2021 and May 2022. CTA was regarded as reference standard. CTA images were examined by a radiologist experienced in musculoskeletal radiology, and MRA images were examined by two radiologists independently to determine presence, grade, and localization of any glenoid cartilage defect, if present. Sensitivity, specificity, and accuracy were calculated separately for conventional and T1-weighted volumetric MRA. In addition, at the last stage, two observers examined all MRAs together, and the presence of a cartilage defect was decided by consensus, and the overall sensitivity, specificity, and accuracy were calculated. Cartilage defect was detected on CTAs of 48 (60.75%) cases of among 79 patients with labrum pathology. The sensitivity, specificity, and accuracy of conventional MRA for two examiners were 17-19%, 100-100%, and 49-51%, respectively, while those values were 67-65%, 92-97%, and 84-77%, respectively, for T1-weighted volumetric MRA. Inter-examiner agreement was excellent for diagnosis of cartilage defects on all MRAs. The overall sensitivity, specificity, and accuracy for detection of glenoid cartilage lesions by MRA were 69%, 97%, and 80%, respectively. T1-weighted volumetric MRA seems to demonstrate cartilage defects accompanied with labrum pathologies accurately with high sensitivity, specificity, and excellent inter-examiner agreement.

Improved small vessel visibility in diabetic foot arteriography using dual-energy CT

To test the feasibility and performance of dual-energy computed tomography (DECT) in foot arteriography of diabetic patients, where contrast medium is largely reduced within the small vessels. A total of 50 diabetic patients were enrolled prospectively, where DECT was acquired immediately after the CT angiography (CTA, group A) of the lower extremity. Two images were derived from the DECT data, one optimal virtual monochromatic image (VMI, group B) and one fusion image (group C), both of which were compared against the CTA image for visualising the foot arteries. The contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were evaluated. The arterial course and contrast were graded each using a five-point scale. The clarity of small vessel depiction was quantified by comparing the number of plantar metatarsal arteries found in the maximum intensity projection image. The median CNRs and SNRs obtained in group B were approximately 45% and 20% higher than those in groups A and C, respectively (p<0.05). Group B also received higher subjective scores on the posterior tibial artery and the foot arteries (all >3) than groups A and C. The number of visible branches of the plantar metatarsal arteries was found to be substantially higher (p<0.05) in group B (median=6) than in groups A (median=2) and C (median=4). DECT was found to be superior to conventional CTA in foot arteriography, and beyond the lower extremity, it might be a general favourable solution for imaging regions with small vessels and reduced contrast medium.

Evaluation of cerebrovascular events via retinal angiography during transcatheter aortic valve implantation

Objectives Patients receiving transcatheter aortic valve implantation (TAVI) are elderly with multiple comorbidities and at increased risk of perioperative cerebrovascular events. Retinal vasculature represents a surrogate of central nervous system circulation and is noninvasively achievable by retinal imaging. The aim of this study was to evaluate the applicability of retinal angiography of microvascular complications and association to cerebral ischemic events during TAVI. Design One hundred patients (male 54%, age: median 82 years, range 64–95 years) undergoing TAVI were recruited for this study. Imaging of retinal vasculature was evaluated with a handheld fundus camera before, during and 1 month after. Cerebrovascular events were determined as a part of contemporary clinical evaluation with cerebral CT and CTA imaging when symptoms occurred. Results Altogether 66/100 patients (66%) were included in the analysis. In-hospital ischemic event (transient ischemic attack, cerebral infarction) was observed in 1/66 patient (1.5%). Retinal vascular abnormalities occurred in 8/66 patients (12.1%); 4/66 patients (6.1%) were detected with a cholesterol plaque in the retinal artery, 2/66 (3%) a capillary leakage, 1/66 (1.5%) and optic disk hemorrhage and 1/66 (1.5%) a macular bleeding. No significant association between retinal vasculature abnormalities and cerebrovascular events was detected mainly due to the low event rate. Conclusions Perioperative evaluation of cerebrovascular ischemia with noninvasive imaging of retinal vasculature is possible in most patients undergoing TAVI. More data is needed to evaluate the association of cerebrovascular events and retinal microvascular abnormalities during the procedure.

Risk predicting for acute coronary syndrome with conventional and unstable plaque radiomics features from serial coronary computed tomography angiography

Abstract Background Plaques with high-risk features are responsible for most acute cardiac events. However, there are still some lesions with high-risk plaque (HRP) morphology, which will not lead to cardiac events over time. It is crucial to precisely identify features of unstable plaque and to carry out individualized treatment, eventually aiming to reduce the likelihood of plaque rupture and lower the incidence of acute coronary events. Besides, the development of quantitative radiomics in recent years may further help with the diagnostic and predictive performance of coronary CTA. Purpose To establish machine learning models by combining traditional coronary CTA features of high-risk plaque and radiomics features of unstable plaque, so as to improve the efficiency of models and to predict acute cardiac events precisely. Methods A total of 133 elderly patients (407 lesions) were retrospectively enrolled in this cohort study who underwent serial CCTA with the interval ≥ 2 years between scans. The patients were divided into two groups according to the occurrence of acute coronary events within 1 year after coronary CTA scanning . We recorded anatomical characteristics, high-risk plaque characteristics, and acute coronary events of the elderly patients. Based on the coronary CTA image cohort, we applied 3D Slicer software to segment target lesions, delineate regions of interest, and extract radiomics features. After that, we used LASSO regression to reduce the dimensionality of the radiomics features, and finally screened out unstable radiomics features. Combining the HRP features with the selected radiomics features, we established a prediction model of acute cardiac events with machine learning method. The area under the receiver operating characteristic (ROC) curve (AUC) was analyzed to compare the classification ability of conventional and radiomics models in the validation set. Results 133 elderly patients were included, with an average age of 65.8 ± 5.3 years. A novel model has been established by combining HRP features and 4 selected unstable radiomics features (2 wavelet features, 1 shape feature and 1 GrayLevel feature) with SVM machine learning method. Compared with conventional HRP model, the novel model displayed a significantly improved predictive performance in the validation set (AUC 0.784 vs. 0.624, P &amp;lt; 0.001). Conclusions We have established a novel model by combining the traditional HRP features of coronary CTA and radiomics features of unstable plaque, assisting in better prediction of acute coronary events in elderly . Compared with traditional HRP feature model, the prediction efficiency of novel model was significantly improved.

Abstract 281: The RACE scale for Large Vessel Stroke Diversion to Comprehensive Center by Helicopter Air Ambulance

Introduction Acute ischemic stroke caused by large vessel occlusion (LVO) occurs frequently and benefits from endovascular therapies available at comprehensive stroke centers (CSC) {Goyal 2016} {Lakomkin, 2019}. Real world evidence shows that endovascular therapy is effective and better than tPA in cases of LVO {Noguria 2016}. Comprehensive stroke centers are also faster at administering tPA and have better tPA metrics for patients with LVO compared to transfers from non CSCs{Shumei M, 2018}{Seker 2020}. Evidence shows that direct transport to an interventional center may provide benefit even if they are not the closest hospital {Benoit J, 2018} {Venema 2020}. Prehospital stroke severity tools such as the RACE scale and others have been devised to detect LVO with reasonable sensitivity and specificity {Krebs 2018} {Dickson 2020}. Helicopter Air Ambulances (HAA) can limit the time to comprehensive stroke care for rural communities {Liera 2016}. Following the recommendations of the American Stroke Society (ASA), regional EMS protocol allow for direct transfer for potential LVO cases within 24 hours by HAA.{NWOEMS consortium protocol}{Powers WJ 2019}. For this reason HAA can enhance access to comprehensive stroke centers into rural communities. Methods A retrospective assessment of RACE scales of 5 or greater performed by prehospital providers was used in order to activate HAA. Descriptive statistics were obtained for patients transported with primary goal of determining the positive predictive values of the RACE Scale for LVO occlusions. Secondary outcomes were if patients had other conditions requiring a comprehensive stroke center. Results Data from 148 subjects were in the research dataset. Twelve of these were eliminated due to not meeting inclusion criteria, death prior to imaging, and transport to another facility where records were not available. This resulted in analyses from 136 subjects. Of the 136, 53 (39.0%) were true LVO cases as defined by CT, CTA imaging or MRI. There were 83 (61%) falsely positive (no LVO on imaging). Mechanical thrombectomy occurred in 30 cases (22.1%) with 63 (46.4%) requiring a neurologic intervention. Conclusion When the RACE scale is used in real world EMS practice to triage rural stroke cases, it has a high positive predictive for HAA activation with delivery to a comprehensive stroke center in suspected stroke cases. Even false positive activations required care at a comprehensive stroke center in most case.

Abstract 228: Suboptimal Door‐to‐Puncture Times: Challenges Faced in the Stroke Alert Workflow

Introduction Advances in stroke care have led to more patients eligible for thrombectomy. With these advances, it has become imperative to create a seamless workflow for thrombectomy candidates to ensure rapid door‐to‐puncture times and, ultimately, improve patient outcomes. We sought to determine what barriers are causing delays in patients’ door‐to‐puncture time. Methods A survey was distributed to all members of the Neurology PGY2, PGY3, PGY4 classes and vascular fellows at our single‐center, Comprehensive Stroke Center. The survey allowed participants to freely respond to questions regarding obstacles they encountered that led to delays in door‐to‐puncture times. All survey responses were anonymized. Results The survey was sent to 32 participants, with 26 responses. Of the 26 responses, 11 respondents (42%) noted that obtaining IV access for CTA/CTP scans was a significant cause of delay. Other responses included lack of availability of family for collateral (23%), CT scanner availability (15%), and length of time to decide if the patient is a thrombectomy candidate (15%). Conclusion The goal of this study was to collect data from the individuals involved in the direct care of acute stroke patients who are thrombectomy candidates. We used their experience to determine which points in the stroke alert workflow led to delays in door‐to‐puncture time. Our survey showed the most consistent delay is obtaining proper IV access for CTA and CTP imaging. This information was valuable and has led to the creation of a coalition between the neurology and emergency medicine departments, nursing, and CT technologists to create a “CODE IV” protocol to be implemented into the stroke alert workflow. We aim to report the change in door‐to‐puncture time after the implementation of this new protocol.

Abstract 191: Simulating Intracranial Stenosis: A Methodological Approach In An In‐Vitro Neurovascular Model

Introduction Intracranial atherosclerotic disease (ICAD) induces the luminal narrowing of an intracranial vessel and represents one of the major causes of ischemic strokes [1, 2, 3, 4]. In vitro 3D printed models have gained popularity in the stroke research field as they are morphologically accurate and offer the possibility to simulate clinical scenarios for training purposes or device testing. Despite being a challenge for interventionalists, to date, clinically accurate ICAD in vitro models have not been developed. We aimed to develop a 3D printed ICAD model including realistic features to provide an optimal simulation phantom for research and training purposes. Methods Stereolithography 3D printing technique was used to create a resin neurovascular model based on vascular anatomies extracted from anonymized CTA images. The phantom includes the aortic arch, all supraoptic cervical arteries and a complete circle of Willis up to the M2‐MCA, A2‐ACA and P2‐PCA segments. 3% sodium alginate solution was cast into a stenosis mold and crosslinked in a 40% calcium chloride. The deformable gel constituted an 8mm long replaceable stenotic segment at the level of M1‐MCA simulating an atherosclerotic plaque with a 0.5mm internal diameter. A flow sensor (ME‐8PXL, Transonic) was used to measure the lesion flow rate before and after endovascular treatment was performed under fluoroscopy. Results The baseline angiographic run showed an irregular 80% stenosis at the level of M1‐MCA that generated a substantial delay of contrast arrival to the distal branches. After angioplasty (Gateway PTA Balloon Catheter 3.5x20mm, Boston Scientific) and stenting (Wingspan 2.5mmx15mm, Stryker) were performed the residual stenosis was &lt;10% (Figure 1). An initial stenosis flow rate was registered with a value of 8.5 ± 5.33 mL/min. Following the completion of the endovascular procedure, the flow sensor detected a post‐procedural stenosis flow rate of 160 ± 3.45 mL/min. Conclusion The developed ICAD model is anatomically accurate and offers realistic physiological and procedural features. The phantom represents an ideal tool for training purposes and a platform to test different devices for the endovascular treatment of ICAD. The methodology and materials could be applied to simulate stenotic lesions at different levels in the cervical and intracranial arteries.