Tectonic infarct analysis: A computational tool for automated whole-brain infarct analysis from TTC-stained tissue

Background

Infarct volume measured from 2,3,5-triphenyltetrazolium chloride (TTC)-stained brain slices is critical to in vivo stroke models. In this study, we developed an interactive, tunable, software that automatically computes whole-brain infarct metrics from serial TTC-stained brain sections.

Methods

Three rat ischemic stroke cohorts were used in this study (Total n = 91 rats; Cohort 1 n = 21, Cohort 2 n = 40, Cohort 3 n = 30). For each, brains were serially-sliced, stained with TTC and scanned on both anterior and posterior sides. Ground truth annotation and infarct morphometric analysis (e.g., brain-V_brain, infarct-V_infarct, and non-infarct-V_non-infarct volumes) were completed by domain experts. We used Cohort 1 for brain and infarct segmentation model development (n = 3 training cases with 36 slices [18 anterior and posterior faces], n = 18 testing cases with 218 slices [109 anterior and posterior faces]), as well as infarct morphometrics automation. The infarct quantification pipeline and pre-trained model were packaged as a standalone software and applied to Cohort 2, an internal validation dataset. Finally, software and model trainability were tested as a use-case with Cohort 3, a dataset from a separate institute.

Results

Both high segmentation and statistically significant quantification performance (correlation between manual and software) were observed across all datasets. Segmentation performance: Cohort 1 brain accuracy = 0.95/f1-score = 0.90, infarct accuracy = 0.96/f1-score = 0.89; Cohort 2 brain accuracy = 0.97/f1-score = 0.90, infarct accuracy = 0.97/f1-score = 0.80; Cohort 3 brain accuracy = 0.96/f1-score = 0.92, infarct accuracy = 0.95/f1-score = 0.82. Infarct quantification (cohort average): V_brain (ρ = 0.87, p < 0.001), V_infarct (0.92, p < 0.001), V_non-infarct (0.80, p < 0.001), %infarct (0.87, p = 0.001), and infarct:non-infact ratio (ρ = 0.92, p < 0.001).

Conclusion

Tectonic Infarct Analysis software offers a robust and adaptable approach for rapid TTC-based stroke assessment.

AAV gene therapy for Tay-Sachs disease

Tay-Sachs disease (TSD) is an inherited neurological disorder caused by deficiency of hexosaminidase A (HexA). Here, we describe an adeno-associated virus (AAV) gene therapy expanded-access trial in two patients with infantile TSD (IND 18225) with safety as the primary endpoint and no secondary endpoints. Patient TSD-001 was treated at 30 months with an equimolar mix of AAVrh8-HEXA and AAVrh8-HEXB administered intrathecally (i.t.), with 75% of the total dose (1 × 1014 vector genomes (vg)) in the cisterna magna and 25% at the thoracolumbar junction. Patient TSD-002 was treated at 7 months by combined bilateral thalamic (1.5 × 1012 vg per thalamus) and i.t. infusion (3.9 × 1013 vg). Both patients were immunosuppressed. Injection procedures were well tolerated, with no vector-related adverse events (AEs) to date. Cerebrospinal fluid (CSF) HexA activity increased from baseline and remained stable in both patients. TSD-002 showed disease stabilization by 3 months after injection with ongoing myelination, a temporary deviation from the natural history of infantile TSD, but disease progression was evident at 6 months after treatment. TSD-001 remains seizure-free at 5 years of age on the same anticonvulsant therapy as before therapy. TSD-002 developed anticonvulsant-responsive seizures at 2 years of age. This study provides early safety and proof-of-concept data in humans for treatment of patients with TSD by AAV gene therapy.

A clinical perspective on endovascular stroke treatment biomechanics

Acute ischemic stroke (AIS) is caused by blockage of an arterial blood vessel in the brain by a thrombus, which interrupts oxygen supply to the brain parenchyma. The goal of endovascular stroke treatment (mechanical thrombectomy) is to restore blood flow as quickly and completely as possible. There are numerous factors that influence endovascular treatment success. They can be broadly grouped into a) factors related to blood vessels, b) factors related to the thrombus, c) factors related to endovascular treatment technique and tools and d) operator-related factors. While blood vessel and tgthro thrombus-related factors are mostly non-modifiable in the acute setting, operator and technique-related factors can be modified, and extensive research is currently being done to investigate the complex interplay of all these variables, and to optimize the modifiable factors to the maximum possible extent. In this review, we will describe these factors and how they interact with each other in detail, and outline some of their practical implications. We will conclude with a short summary and outlook on future directions for optimizing endovascular treatment success.

Abstract P561: Efficacy of Beveled Tip Aspiration Catheter in Mechanical Thrombectomy for Acute Ischemic Stroke

Introduction: The ADAPT technique uses large bore aspiration catheters for mechanical thrombectomy. Several aspiration catheters are now available. We report a bench-top exploration of a beveled-tip catheter, and our experience in treating large vessel occlusions using next-generation aspiration catheters.

Methods: Twenty experiments were conducted with either a Sofia Plus or a Zoom71 using a vascular phantom in which a clot model was introduced. Rate of ingestion, complete recanalization after a single attempt, and pressure at the catheter tip for both devices were recorded. A retrospective analysis from a prospectively-maintained database was performed. Patient demographics, periprocedural metrics, discharge and 90-day modified Rankin Scales were collected. Patients were divided into two groups based on which aspiration catheter was used.

Results: In our bench-top experiment, complete ingestion of the clot occurred in 90% of beveled tip and 20% of control device experiments (p=0.006). Our clinical data demonstrated no significant difference in age, gender, IV tPA administration, admission NIHSS, baseline mRS, or LVO location between the beveled tip and flat tip groups. With the beveled tip, TICI 2C or better recanalization was more frequent (93.2% vs 74.2%, p-value 0.017), stent retriever usage was lower (9.1% versus 29%, p-value 0.024), and patients had lower mRS on discharge (median 3 vs 4, p less than 0.001) and at 90 days (median 2 vs 4, p=0.008).

Conclusion: The beveled tip design leads to more frequent clot ingestion in a bench top model, which may translate into a more efficacious thrombectomy device with improved outcomes.

Abstract 147: Outcomes of the Stroke Thromboembolism Registry of Imaging and Pathology: A Multicenter International Study

Background: We performed a multicenter prospective clinical registry across 11 centers to study the association between histopathological characteristics of retrieved clots and imaging, stroke etiology and clinical outcomes.

Materials and Methods: Following IRB approval at the 11 centers, patients were enrolled in the STRIP registry. All retrieved emboli were sent for histopathological analysis with H&E and MSB staining. Demographic variables, comorbidities, stroke etiology, imaging findings and procedural details were collected for each case. We studied the association between clot histopathology and imaging findings, stroke etiology and and revascularization outcomes. Student’s t-test was used for continuous variables and chi-squared testing for categorical variables.

Results: To date, 1022 patients have been included. There was a significant correlation between platelet rich clots and the absence of hyperdensity on non-contrast CT [p=0.321, p=0.003) and a significant inverse correlation between the percentage of platelets and mean HU on NCCT (p=-0.243, p=0.025). The proportion of platelet-rich clots (55.0% versus 21.2%, p=0.005) and the percentage of platelet content (22.1% versus 13.9%, p=0.03) was significantly higher in patient with large artery atherosclerosis compared to those with a cardioembolic etiology. There was no correlation between RBC density, WBC density, fibrin density or platelet density and revascularization outcomes with stent-retrievers. However, we have found that with aspiration alone, patients with platelet rich clots are less likely to be fully revascularized (i.e. TICI 2c/3) than non-platelet rich clots (OR=0.36, 95%CI=0.12-0.81, P<.0001). Meanwhile, patients with RBC rich clots are more likely to be completely revascularized with aspiration alone than those with RBC poor clots (OR=2.71, 95%CI=1.25-3.24, P=0.02).

Conclusions: Interim analysis of the STRIP registry suggests that the platelet content of a clot may be the most revealing factor in determining a clot’s etiology, imaging features and revascularization outcome. Platelet rich clots are less dense on NCCT, are associated with a large artery atherosclerosis source and are less likely to be completely revascularized with aspiration alone.

Abstract WP1: High-Frequency Optical Coherence Tomography for Cerebrovascular Disease

Introduction: Optical coherence tomography (OCT) has played an important role in the diagnosis and treatment guidance in coronary artery disease. However, existing OCT systems are not suitable for routine neurovascular applications due to the size and tortuosity of the arteries.

Hypothesis: We seek to demonstrate a prototype high-frequency OCT (HF-OCT) capable of high-resolution imaging in simulated cerebrovascular anatomy.

Methods: A low-profile HF-OCT system was constructed with an image resolution approaching 10μm. Using an in vitro, patient-specific model of the circle of Willis with circulating porcine blood, we characterized the delivery of the device and ability to image in a tortuous path. Also, human cadaver intracranial atherosclerosis plaques were imaged with HF-OCT and assessed by an expert imager. Finally, neurovascular devices were implanted in 8 pigs (Fig 1) and HF-OCT imaging was compared with gold-standard DSA and CT.

Results: In the phantom, optimal blood clearance was achieved through an intermediate catheter (5 Fr Navien) with infusion of contrast at 5 ml/s in the internal carotid and basilar artery, and 3 ml/sec in the MCA. The in vivo study demonstrated that both malapposition of devices or thrombus formation along the device surface could be reliably diagnosed among 3 reviewers (Fleiss’s kappa of 0.87 and 0.9, respectively). This agreement was superior to DSA and CT. Imaging in tortuous swine brachial showed in all cases imaging free of artifacts, uniform illumination and ability to visualize vessel wall layers. Plaque types including ‘lipid pools’, fibrotic, and calcific tissue from cadaver specimens of ICAD could be adequately depicted by HF-OCT.

Conclusion: In vitro, in vivo and ex vivo characterization of a novel HF-OCT device has shown it is capable of imaging in the tortuous intracranial vascular anatomy. This technology has to potential to aid in the diagnosis of cerebrovascular disease and guide optimal endovascular treatment.

The Importance of Wall Apposition in Flow Diverters

BACKGROUND

It is assumed that high pore densities in flow diverters (FDs) are beneficial for intracranial aneurysm (IA) healing. However, various animal studies are not conclusive on the issue, suggesting that other factors are in play. One important factor might be wall apposition.

OBJECTIVE

To (1) determine the relationship between FD pore density and aneurysm occlusion, and (2) determine the relationship between FD wall apposition and aneurysm occlusion.

METHODS

Saccular aneurysms were microsurgically created in the aorta of 36 Wistar rats. Twelve rats received a low pore density FD (10 pores/mm2), 12 rats received a high pore density FD (23 pores/mm2), and the remaining 12 rats served as a control group. Six animals from each group were sacrificed 1 and 3 mo after surgery. We determined aneurysm occlusion, the number of struts not in contact with the aorta wall, and the average distance from malapposed struts to aorta wall through histology.

RESULTS

No significant differences were found in aneurysm occlusion between the low pore density and high pore density groups (P > .05) after 1 and 3 mo of follow-up. The average number of malapposed struts was lower for the occluded aneurysm group (4.4 ± 1.9) compared to the nonoccluded aneurysm group (7.7 ± 2.6, P < .01). The average distance between malapposed struts and parent artery wall was lower for the occluded aneurysm group (33.9 μm ± 11.5 μm) than for the nonoccluded aneurysm group (48.7 μm ± 18.8 μm, P < .05).

CONCLUSION

Wall apposition is more important than pore density for aneurysm occlusion.

Robotic Assisted MRI-Guided Interventional Interstitial MR-Guided Focused Ultrasound Ablation in a Swine Model

BACKGROUND

Ablative lesions are current treatments for epilepsy and brain tumors. Interstitial magnetic resonance (MR) guided focused ultrasound (iMRgFUS) may be an alternate ablation technique which limits thermal tissue charring as compared to laser therapy (LITT) and can produce larger ablation patterns nearer the surface than transcranial MR guided focused ultrasound (tcMRgFUS).

OBJECTIVE

To describe our experience with interstitial focused ultrasound (iFUS) ablations in swine, using MR-guided robotically assisted (MRgRA) delivery.

METHODS

In an initial 3 animals, we optimized the workflow of the robot in the MR suite and made modifications to the robotic arm to allow range of motion. Then, 6 farm pigs (4 acute, 2 survival) underwent 7 iMRgFUS ablations using MRgRA. We altered dosing to explore differences between thermal dosing in brain as compared to other tissues. Imaging was compared to gross examination.

RESULTS

Our work culminated in adjustments to the MRgRA, iMRgFUS probes, and dosing, culminating in 2 survival surgeries; swine had ablations with no neurological sequelae at 2 wk postprocedure. Immediately following iMRgFUS therapy, diffusion-weighted imaging, and T1 weighted MR were accurate reflections of the ablation volume. T2 and fluid-attenuated inversion-recovery (FLAIR) images were accurate reflections of ablation volume 1-wk postprocedure.

CONCLUSION

We successfully performed MRgRA iFUS ablation in swine and found intraoperative and postoperative imaging to correlate with histological examination. These data are useful to validate our system and to guide imaging follow-up for thermal ablation lesions in brain tissue from our therapy, tcMRgFUS, and LITT.

Wingspan experience in the treatment of symptomatic intracranial atherosclerotic disease after antithrombotic failure

BACKGROUND AND PURPOSE

Intracranial stenting with the Wingspan system has been used as a revascularization strategy in symptomatic patients with intracranial atherosclerotic disease (ICAD). The latest results of the Stenting versus Aggressive Medical Therapy for Intracranial Artery Stenosis (SAMMPRIS) trial challenge this approach. Our experience in the treatment of symptomatic ICAD with the Wingspan system is reported.

MATERIALS AND METHODS

Patients who underwent stenting for symptomatic ICAD were included in the analysis. Demographic data, periprocedural complications, long term radiological and clinical outcomes are reported.

RESULTS

46 lesions were treated in 45 patients. 13 patients (29%) presented with a transient ischemic attack and 32 (71%) with a stroke. 43 patients (95.5%) failed antithrombotic therapy at presentation. One (2%) symptomatic periprocedural (24 h) complication occurred. The 30 day incidence of stroke and vascular death was 6.6%--a fatal hemorrhagic stroke and two non-fatal hemorrhagic strokes. In-stent stenosis (≥50%) was seen in nine (42.8%) lesions, two were symptomatic.

CONCLUSIONS

This cohort of patients with symptomatic ICAD who failed antithrombotic medications benefited from angioplasty and stenting with the Wingspan system.

The Trevo device: preclinical data of a novel stroke thrombectomy device in two different animal models of arterial thrombo-occlusive disease

BACKGROUND

The currently available mechanical devices fail to achieve recanalization in as many as 20-40% of proximal arterial occlusion strokes.

OBJECTIVE

The preclinical evaluation of the safety and efficacy of a novel thrombectomy device designed to achieve immediate flow restoration by quickly removing clot is reported.

METHODS

Four confirmatory animal studies were performed with the Trevo device (Concentric Medical Inc, Mountain View, California, USA) in the swine (n=2) and canine (n=1) models of arterial thrombo-occlusive disease employing autologous thrombin generated thrombi. The angiographic response and the degree of device-clot incorporation were evaluated. High resolution flat panel three-dimensional CT was performed to further define the in vivo device-thrombus-vessel interaction. Finally, samples of three swine vessels treated with six passes of the device were explanted for histopathological analysis.

RESULTS

A total of 16 clots of variable hardness and consistency were implanted in a variety of vascular settings, including the swine internal maxillary, lingual and forelimb arteries as well as the canine external carotid and vertebral arteries. Thrombolysis in Myocardial Infarction (TIMI) 2-3 reperfusion was achieved in all cases immediately after device deployment. All 16 clots were retrieved after one (n=15) or two (n=1) passes with the device. Histopathological analysis demonstrated severe disruption of the intima but no hemorrhage of media or adventitia.

CONCLUSION

The experimental data suggest that the Trevo device is highly effective at achieving immediate reperfusion of occluded arteries without causing any clinically significant disruption of vascular integrity.