Optical Coherence Tomography for Neurovascular Disorders

The DERIVO 2 Heal Embolization Device in the Treatment of Ruptured and Unruptured Intracranial Aneurysms: a Retrospective Multicenter Study

BACKROUND

The use of flow diverting stents in the treatment of intracranial aneurysms is associated with a risk of neurological morbidity due to their thrombogenicity. To reduce this risk different surface modifications have been developed. The Derivo 2 Embolization Device (Acandis, Pforzheim, Germany) has proven to be a safe and effective flow diverter. To overcome the risk of thrombo-embolism, the device was modified by adding an anti-thrombogenic fibrin-heparin coating. We aimed to assess the safety and effectiveness of the Derivo 2 heal Embolization Device.

METHODS

Retrospective multicenter data from nine German neurovascular centers between February 2022 until December 2023 were used. Patients treated with the Derivo 2 heal Embolization Device for unruptured or ruptured intracranial aneurysms were included. Peri- and postprocedural adverse events, clinical outcomes, and angiographic follow-up results were evaluated.

RESULTS

84 patients (73.8% female; mean age 58.7 years) with 89 aneurysms (mean size 9.8 mm) were included. 87.6% were located in the anterior circulation. Most of them were sidewall aneurysms (88.8%). 96 flow diverters were used. 99.0% were successfully implanted. An in-stent balloon angioplasty was performed in 6.0% of the cases. An additional coiling was performed in 28.6%. Technical difficulties were present in 12.0% of the cases. Thrombotic events occurred in 4.8% with no neurological sequelae. Mortality and morbidity were 0 and 1.2% respectively. Adequate aneurysm occlusion was achieved in 80.7% with a mean follow-up time of 6.6 months.

CONCLUSION

The Derivo 2 heal Embolization Device showed a satisfying aneurysm occlusion and safety with a low rate of neurological morbidity.

Perspectives on endoscopic functional photoacoustic microscopy

Endoscopy, enabling high-resolution imaging of deep tissues and internal organs, plays an important role in basic research and clinical practice. Recent advances in photoacoustic microscopy (PAM), demonstrating excellent capabilities in high-resolution functional imaging, have sparked significant interest in its integration into the field of endoscopy. However, there are challenges in achieving functional PAM in the endoscopic setting. This Perspective article discusses current progress in the development of endoscopic PAM and the challenges related to functional measurements. Then, it points out potential directions to advance endoscopic PAM for functional imaging by leveraging fiber optics, microfabrication, optical engineering, and computational approaches. Finally, it highlights emerging opportunities for functional endoscopic PAM in basic and translational biomedicine.

ARISE I Consensus Review on the Management of Intracranial Aneurysms

BACKGROUND

Intracranial aneurysms (IAs) remain a challenging neurological diagnosis associated with significant morbidity and mortality. There is a plethora of microsurgical and endovascular techniques for the treatment of both ruptured and unruptured aneurysms. There is no definitive consensus as to the best treatment option for this cerebrovascular pathology. The Aneurysm, Arteriovenous Malformation, and Chronic Subdural Hematoma Roundtable Discussion With Industry and Stroke Experts discussed best practices and the most promising approaches to improve the management of brain aneurysms.

METHODS

A group of experts from academia, industry, and federal regulators convened to discuss updated clinical trials, scientific research on preclinical system models, management options, screening and monitoring, and promising novel device technologies, aiming to improve the outcomes of patients with IA.

RESULTS

Aneurysm, Arteriovenous Malformation, and Chronic Subdural Hematoma Roundtable Discussion With Industry and Stroke Experts suggested the incorporation of artificial intelligence to capture sequential aneurysm growth, identify predictors of rupture, and predict the risk of rupture to guide treatment options. The consensus strongly recommended nationwide systemic data collection of unruptured IA radiographic images for the analysis and development of machine learning algorithms for rupture risk. The consensus supported centers of excellence for preclinical multicenter trials in areas such as genetics, cellular composition, and radiogenomics. Optical coherence tomography and magnetic resonance imaging contrast-enhanced 3T vessel wall imaging are promising technologies; however, more data are needed to define their role in IA management. Ruptured aneurysms are best managed at large volume centers, which should include comprehensive patient management with expertise in microsurgery, endovascular surgery, neurology, and neurocritical care.

CONCLUSIONS

Clinical and preclinical studies and scientific research on IA should engage high-volume centers and be conducted in multicenter collaborative efforts. The future of IA diagnosis and monitoring could be enhanced by the incorporation of artificial intelligence and national radiographic and biologic registries. A collaborative effort between academic centers, government regulators, and the device industry is paramount for the adequate management of IA and the advancement of the field.

Optical Coherence Tomography in the Evaluation of Suspected Carotid Webs

BACKGROUND

Carotid web (CaW) is a subtype of fibromuscular dysplasia that predominantly involves the intimal layer of the arterial wall and is commonly overlooked as a separate causative entity for recurrent strokes. CaW is defined as a shelf-like lesion at the carotid bulb, although different morphological features have been reported. Optical coherence tomography (OCT) has been described in the literature as a useful microscopic and cross-sectional tomographic imaging tool. This study aimed to evaluate the potential utility of OCT in characterizing the wall structure features of patients with suspected CaW.

METHODS

Retrospective analysis of patients with suspected CaW who underwent digital subtraction angiography (DSA) coupled with OCT of the carotid bulb from 2018 to 2021 in a single comprehensive stroke center.

RESULTS

Sixteen patients were included. The median age was 56 years (IQR 46-61) and 50% were women. OCT corroborated the diagnosis of CaW in 12/16 (75%) cases and ruled it out in 4/16 (25%) patients in whom atherosclerotic disease was demonstrated. Five of the 12 lesions demonstrated a thick fibrotic ridge consistent with CaW but also showed atherosclerotic changes in the vicinity of the carotid bulb (labeled as "CaW+"). In 4/16 (25%) patients, microthrombi adhered to the vessel wall were noted on OCT (inside the CaW pocket or just distal to the web), none of which were observed on CT angiography or DSA.

CONCLUSIONS

OCT may have value as a complementary imaging tool in the investigation of patients with suspected CaW and atypical morphological features. Further studies are warranted.

Magnetically assisted soft milli-tools for occluded lumen morphology detection

Methodologies based on intravascular imaging have revolutionized the diagnosis and treatment of endovascular diseases. However, current methods are limited in detecting, i.e., visualizing and crossing, complicated occluded vessels. Therefore, we propose a miniature soft tool comprising a magnet-assisted active deformation segment (ADS) and a fluid drag-driven segment (FDS) to visualize and cross the occlusions with various morphologies. First, via soft-bodied deformation and interaction, the ADS could visualize the structure details of partial occlusions with features as small as 0.5 millimeters. Then, by leveraging the fluidic drag from the pulsatile flow, the FDS could automatically detect an entry point selectively from severe occlusions with complicated microchannels whose diameters are down to 0.2 millimeters. The functions have been validated in both biologically relevant phantoms and organs ex vivo. This soft tool could help enhance the efficacy of minimally invasive medicine for the diagnosis and treatment of occlusions in various circulatory systems.

Correction of refractive distortion in whole-eye optical coherence tomography imaging of the mouse eye

Optical coherence tomography (OCT) is an imaging modality that acquires high-resolution cross-sectional images of living tissues and it has become the standard in ophthalmological diagnoses. However, most quantitative morphological measurements are based on the raw OCT images which are distorted by several mechanisms such as the refraction of probe light in the sample and the scan geometries and thus the analysis of the raw OCT images inevitably induced calculation errors. In this paper, based on Fermat's principle and the concept of inverse light tracing, image distortions due to refraction occurred at tissue boundaries in the whole-eye OCT imaging of mouse by telecentric scanning were corrected. Specially, the mathematical correction models were deducted for each interface, and the high-precision whole-eye image was recovered segment by segment. We conducted phantom and in vivo experiments on mouse and human eyes to verify the distortion correction algorithm, and several parameters of the radius of curvature, thickness of tissues and error, were calculated to quantitatively evaluate the images. Experimental results demonstrated that the method can provide accurate and reliable measurements of whole-eye parameters and thus be a valuable tool for the research and clinical diagnosis.

Polyamide (PA) 66 molding defect studied with optical coherence tomography (OCT) and near-infrared (NIR) spectroscopy

An optical coherence tomography (OCT) system combined with near-infrared spectroscopy (NIRS) was developed to carry out simultaneously the cross-sectional observation and spectral measurement of a specific area inside a polymer sample. This OCT-NIRS system consists of a fiber-optic-based spectrometer combined with an OCT system and enables non-invasive imaging up to a depth of several millimeters and the recording of the NIR spectrum in the observed area. A subsequent analysis of the collected data will provide key information revealing the way in which the microscopic structure of the polymer is affected by the chemical composition around it. A structural defect inside a molded polyamide (PA) 66 sample was examined with the OCT-NIRS system to demonstrate how this technique can be utilized to characterize chemical composition as well as the morphological features inside the sample. A specific void was detected by OCT when the PA sample was molded without any drying treatment. The NIR spectrum collected around the void area of the undried PA was then compared with that of vacuum-dried PA by two-trace two-dimensional (2T2D) correlation analysis to identify a subtle but pertinent difference in the spectral features. The appearance of several correlation peaks in the 2T2D asynchronous correlation spectrum revealed that the OH group represented by the NIR band at 1446 nm is found in relative abundance around the void, which clearly reveals that the development of the void in the molded PA results from inadequate sample pretreatment.

Application of optical coherence tomography in decision-making of post-thrombectomy adjunctive treatments

An adult patient with acute basilar artery occlusion underwent mechanical thrombectomy. After complete reperfusion, a 70% residual stenosis of the proximal basilar artery was observed. Intravascular optical coherence tomography (OCT) identified lipid plaques with an intact fibrous cap and thrombus in the culprit lesion, indicating plaque erosion was the mechanism of in situ thrombosis. Adjunctive antiplatelet therapy rather than rescue interventions was pursued for its beneficial effects in acute coronary syndrome caused by plaque erosion. The patient had a 90-day modified Rankin Scale score of 0. OCT enables precise evaluation of vessel characteristics following thrombectomy, so may improve outcomes through subsequent tailored treatments.

Transvascular in vivo microscopy of the subarachnoid space

BACKGROUND

The micro-architectonics of the subarachnoid space (SAS) remain partially understood and largely ignored, likely the result of the inability to image these structures in vivo. We explored transvascular imaging with high-frequency optical coherence tomography (HF-OCT) to interrogate the SAS.

METHODS

In vivo HF-OCT was performed in 10 dogs in both the posterior and anterior cerebral circulations. The conduit vessels used were the basilar, anterior spinal, and middle and anterior cerebral arteries through which the perivascular SAS was imaged. The HF-OCT imaging probe was introduced via a microcatheter and images were acquired using a contrast injection (3.5 mL/s) for blood clearance. Segmentation and three-dimensional rendering of HF-OCT images were performed to study the different configurations and porosity of the subarachnoid trabeculae (SAT) as a function of location.

RESULTS

Of 13 acquisitions, three were excluded due to suboptimal image quality. Analysis of 15 locations from seven animals was performed showing six distinct configurations of arachnoid structures in the posterior circulation and middle cerebral artery, ranging from minimal presence of SAT to dense networks and membranes. Different locations showed predilection for specific arachnoid morphologies. At the basilar bifurcation, a thick, fenestrated membrane had a unique morphology. SAT average thickness was 100 µm and did not vary significantly based on location. Similarly, the porosity of the SAT averaged 91% and showed low variability.

CONCLUSION

We have demonstrated the feasibility to image the structures of the SAS with transvascular HF-OCT. Future studies are planned to further map the SAT to increase our understanding of their function and possible impact on neurovascular pathologies.