Development of a comprehensive and clinically applicable novel projection classification system for anterior communicating artery aneurysms.

Various surgical and anatomical classifications have been proposed to date related to ACoA aneurysm projection. Nonetheless, a universally accepted classification system is yet to be established. This study is aimed at establishing a standardized classification system for ACoA aneurysms with utilization 3D technology and defining reference lines for their projections. The goal is to create a simple, understandable, surgically beneficial, and reliable classification system based on neurovascular structures in the region, including safe and hazardous zones. The radiologic data of 96 patients with ACoA aneurysm who were treated in our university hospital between 2012 and 2020 were retrospectively analyzed, and a planned classification scale was developed with the data obtained. The classification aimed to create 9 main projection groups in the sagittal plane: superior, inferior, anterior, and posterior in linear orientation, and anterosuperior, posterosuperior, anteroinferior, posteroinferior, and complex in quadrant orientation. The coronal and axial planes included medial, lateral, and midline classifications, resulting in a 3-dimensional classification system with 25 projections. Among the 96 patients, 32 had linear and 64 had quadrant projections. In the sagittal plane, the linear projection breakdown was as follows: superior (28%), inferior (6.25%), anterior (53%), and posterior (12.5%). For the quadrant projection, the distribution was as follows: anterosuperior (53%), posterosuperior (12.5%), anteroinferior (21.87%), posteroinferior (3.12%), and complex (9.37%). Overall, 35.4% aneurysms were anterosuperior, 17.7% anterior, 14.58% anteroinferior, 9.37% superior, 8.3% posterosuperior, 6.25% complex, 4.16% posterior, 2.08% posteroinferior, and 2.08% inferior projection. Our study proposes a projection classification that utilizes 3D technology for safe surgery based on neurovascular structures in the region and thus better reveals safe and hazardous zones, including three plans, three dimensions, and two orientations. The use of this classification system offers valuable guidance for daily practice in the treatment of ACoA aneurysms.

Endoscopic clipping of an anterior communicating artery aneurysm.

BACKGROUND: Anterior communicating artery aneurysms are most prone to rupture. Surgically, they are conventionally being managed by a pterional approach. Some neurosurgeons prefer a supraorbital keyhole approach in select cases. Fully endoscopic clipping of such aneurysms is seldom described. METHOD: We clipped an antero-inferiorly directed anterior communicating artery aneurysm endoscopically via a supraorbital keyhole approach. The intraoperative aneurysmal rupture was also managed endoscopically. The patient made an excellent postoperative recovery without any neurological deficits. CONCLUSION: Select cases of anterior communicating artery aneurysms can be clipped endoscopically using standard instruments and adhering to the basic principles of aneurysm clipping.

Automated Crystal Orientation Mapping in py4DSTEM using Sparse Correlation Matching.

Crystalline materials used in technological applications are often complex assemblies composed of multiple phases and differently oriented grains. Robust identification of the phases and orientation relationships from these samples is crucial, but the information extracted from the diffraction condition probed by an electron beam is often incomplete. We have developed an automated crystal orientation mapping (ACOM) procedure which uses a converged electron probe to collect diffraction patterns from multiple locations across a complex sample. We provide an algorithm to determine the orientation of each diffraction pattern based on a fast sparse correlation method. We demonstrate the speed and accuracy of our method by indexing diffraction patterns generated using both kinematical and dynamical simulations. We have also measured orientation maps from an experimental dataset consisting of a complex polycrystalline twisted helical AuAgPd nanowire. From these maps we identify twin planes between adjacent grains, which may be responsible for the twisted helical structure. All of our methods are made freely available as open source code, including tutorials which can be easily adapted to perform ACOM measurements on diffraction pattern datasets.

Comparison between outcomes of endovascular and surgical treatments of ruptured anterior communicating artery aneurysms.

INTRODUCTION: The natural history and optimal treatment of previously ruptured anterior communicating artery (ACOM) aneurysms that recur is unknown. This study looks at rates of complications and recurrences of ruptured ACOM aneurysms treated endovascularly and surgically. MATERIALS AND METHODS: A retrospective observational study of all patients presenting to a single tertiary neurosurgical centre with the first presentation of subarachnoid haemorrhage (SAH) secondary to a ruptured ACOM aneurysm. Data was collected from November 2012 to September 2018 and included baseline demographics, aneurysm characteristics, management, complications, follow-up imaging, and clinical outcomes. RESULTS: 137 patients were included in the study. 113 aneurysms were coiled and 19 were clipped. Management decisions were taken by the multidisciplinary team based on aneurysm morphology or the presence of a haematoma exerting mass effect. There were 187.5 patient-years of follow-up, with a median of 3 years (range 0-73 months). Rates of vasospasm, infarction, CSF diversion, rebleed, length of stay, and functional outcome were not significantly different in the two cohorts. There was a statistically significant increase in the risk of ACOM recurrence in the coiled group when compared to the clipped group at one year (p = .0433). 15 patients required further treatment at a median time of 16 months. In a subgroup group analysis of coiled aneurysms, there was no statistical differences in rates of rebleeding or the functional outcome in those that had aneurysm recurrence and those that did not. CONCLUSIONS: This study suggests patients with aneurysms treated by endovascular coiling have an increased risk of recurrence versus those treated with clipping. However, the risk of rebleed was not statistically significant. The prevention and impact of recurrence and residual aneurysms remains incompletely understood. Hence, treatment decisions should be taken by patients after they have been given carefully considered recommendations from the multi-disciplinary team.

Retrieving overlapping crystals information from TEM nano-beam electron diffraction patterns.

The diffraction patterns acquired with a transmission electron microscope (TEM) contain Bragg reflections related to all the crystals superimposed in the thin foil and crossed by the electron beam. Regarding TEM-based orientation and phase characterisation techniques, the nondissociation of these signals is usually considered as the main limitation for the indexation of diffraction patterns. A new method to identify the information related to the distinct but overlapped grains is presented. It consists in subtracting the signature of the dominant crystal before reindexing the diffraction pattern. The method is coupled to the template matching algorithm used in a standard automated crystal orientation mapping tool (ACOM-TEM). The capabilities of the approach are illustrated with the characterisation of a NiSi thin film stacked on a monocrystalline Si layer. Then, a subtracting-indexing cycle applied to a 70 nm thick thin foil containing polycrystalline tungsten electrical contacts shows the capability of the technique to recognise small nondominant grains.

Anterior communicating artery aneurysm clipping using standard small fronto-pterional approach, clipping with 3 Lazic clips.

An 80-year-old female presented 5 months previous for nonspecific gait disturbance, during which an MRI was performed. A large based anterior communicating artery aneurym was found independent of neurology. An interdisciplinary discussion favored surgical treatment, on which the patient insisted. Surgery was performed using standard anesthesia techniques with intraoperative burst supression during surgery, neuromonitoring with MEP and SEP, as well as ICG angiography, microdoppler and neuronavigation. Successful clipping was performed with 2 fenestrated straight and one bayoneted straight Lazic clip. Temporary clipping was 6.1 minutes. Postoperative angiography showed exclusion of the aneurysm, and there was no neurological deficit. The video can be found here: http://youtu.be/WKjOHG8irFo .

Flow artifact in the anterior communicating artery resembling aneurysm on the time of flight MR angiogram.

BACKGROUND: Magnetic resonance angiogram (MRA) of the brain is a widely employed non-invasive test to diagnose aneurysms. However, its overall accuracy is less than digital subtraction angiography and is prone to give false-positive or false-negative results. False-negative results can be seen with hemorrhage, lipoma, dermoid, posterior lobe of the pituitary gland, and the flow artifacts. PURPOSE: To describe the findings associated with false aneurysms in the anterior communicating artery on the time of flight MRA and review the physical principles behind this artifact. MATERIAL AND METHODS: This short series comprises of four patients whose MRA showed suspicious aneurysms in the region of the anterior communicating artery (ACOM) on time of flight MRA. RESULTS: Two patients underwent catheter angiogram and the other two patients had computed tomography angiogram. None of these cases proved to have aneurysms and normal anterior communicating arteries were seen in all the patients. The findings on the MR angiograms were considered artifacts. All of the pseudoaneurysm had tapered appearance. CONCLUSION: MR angiogram can result in artifacts at ACOM which may be mistaken for aneurysm. Such pseudoaneurysms have characteristic appearance and should be followed up with non-invasive tests.

Application of a novel local and automatic PCA algorithm for diffraction pattern denoising in TEM-ASTAR analysis in microelectronics.

This paper introduces a novel denoising method for TEM-ASTAR™ Diffraction Pattern (DP) datasets, termed LAT-PCA (Local Automatic Thresholding - Principal Component Analysis). This approach enhances the established PCA algorithm by partitioning the 4D dataset (a 2D map of 2D DPs) into localized windows. Within these windows, PCA identifies a basis where the physical signal predominantly resides in the higher-order principal components. By thresholding lower-order components, the method effectively reduces noise while retaining the essential features of the DPs. The locality of the approach, focusing on small windows, enhances computational efficiency and aligns with the localized nature of the crystallographic grain signals in ASTAR. The automatic aspect of the method employs a theoretical pure noise distribution, i.e. a Marchenko-Pastur Distribution, to set a threshold, beyond which the components are mostly noise. The LAT-PCA method offers significant reductions in acquisition and post-processing times. With denoised data, selecting the correct parameters for accurate phase maps and grain orientations becomes more straightforward, facilitating robust quantitative grain analysis. Experiments performed on a silicon-germanium-carbon sample validate the method's efficacy. The sample was analyzed with varying acquisition times to produce a high signal-to-noise ratio reference dataset and a lower ratio test dataset. The LAT-PCA algorithm's denoising results on the test dataset were benchmarked against the reference, demonstrating considerable improvements and reliability. In summary, LAT-PCA is an effective, automatic solution for denoising TEM DP datasets. Its adaptability to different noise levels and local processing capability makes it a valuable tool for enhancing dataset quality and reducing the time required for data acquisition and analysis. This method can minimize acquisition time, conserve microscope usage, and reduce sample drift and deterioration, leading to more accurate characterizations with fewer deformation artifacts.

Distribution of rupture sites and blebs on intracranial aneurysm walls suggests distinct rupture patterns in ACom and MCA aneurysms.

The mechanisms behind intracranial aneurysm formation and rupture are not fully understood, with factors such as location, patient demographics, and hemodynamics playing a role. Additionally, the significance of anatomical features like blebs in ruptures is debated. This highlights the necessity for comprehensive research that combines patient-specific risk factors with a detailed analysis of local hemodynamic characteristics at bleb and rupture sites. Our study analyzed 359 intracranial aneurysms from 268 patients, reconstructing patient-specific models for hemodynamic simulations based on 3D rotational angiographic images and intraoperative videos. We identified aneurysm subregions and delineated rupture sites, characterizing blebs and their regional overlap, employing statistical comparisons across demographics, and other risk factors. This work identifies patterns in aneurysm rupture sites, predominantly at the dome, with variations across patient demographics. Hypertensive and anterior communicating artery (ACom) aneurysms showed specific rupture patterns and bleb associations, indicating two pathways: high-flow in ACom with thin blebs at impingement sites and low-flow, oscillatory conditions in middle cerebral artery (MCA) aneurysms fostering thick blebs. Bleb characteristics varied with gender, age, and smoking, linking rupture risks to hemodynamic factors and patient profiles. These insights enhance understanding of the hemodynamic mechanisms leading to rupture events. This analysis elucidates the role of localized hemodynamics in intracranial aneurysm rupture, challenging the emphasis on location by revealing how flow variations influence stability and risk. We identify two pathways to wall failure-high-flow and low-flow conditions-highlighting the complexity of aneurysm behavior. Additionally, this research advances our knowledge of how inherent patient-specific characteristics impact these processes, which need further investigation.

Improved ACOM pattern matching in 4D-STEM through adaptive sub-pixel peak detection and image reconstruction.

The technique known as 4D-STEM has recently emerged as a powerful tool for the local characterization of crystalline structures in materials, such as cathode materials for Li-ion batteries or perovskite materials for photovoltaics. However, the use of new detectors optimized for electron diffraction patterns and other advanced techniques requires constant adaptation of methodologies to address the challenges associated with crystalline materials. In this study, we present a novel image-processing method to improve pattern matching in the determination of crystalline orientations and phases. Our approach uses sub-pixel adaptive image processing to register and reconstruct electron diffraction signals in large 4D-STEM datasets. By using adaptive prominence and linear filters, we can improve the quality of the diffraction pattern registration. The resulting data compression rate of 103 is well-suited for the era of big data and provides a significant enhancement in the performance of the entire ACOM data processing method. Our approach is evaluated using dedicated metrics, which demonstrate a high improvement in phase recognition. Several features are extracted from the registered data to map properties such as the spot count, and various virtual dark fields, which are used to enhance the handling of the results maps. Our results demonstrate that this data preparation method not only enhances the quality of the resulting image but also boosts the confidence level in the analysis of the outcomes related to determining crystal orientation and phase. Additionally, it mitigates the impact of user bias that may occur during the application of the method through the manipulation of parameters.

Circulation remodeling after flow diversion of an anterior communicating artery aneurysm: A case report.

Anterior communicating artery aneurysms are the most common intracranial aneurysm and have a high risk of rupture which can lead to morbidity and mortality. Traditionally, intracranial aneurysms were treated by clipping with neurosurgical access. However, certain patients may prefer less invasive approaches or not represent open surgical candidates. Flow diverters, including flow-redirection endoluminal devices (FRED), are new-generation stents that are placed endovascularly by transfemoral or transradial access. Recent studies have demonstrated that FRED is both safe and effective, with complete occlusion of aneurysms in over 90% of patients. This case highlights an interesting phenomenon of post-flow diversion circulatory remodeling, where flow diverter treatment can alter the circle of Willis anatomy and physiology.

Giant anterior communicating artery aneurysm with intrasellar extension.

Introduction: Aneurysms extending into the sella are uncommon with only a few cases reported till date. Most of these arise from either the supraclinoidal or infraclinoidal segments of the internal carotid artery. Research question: Can Anterior communication artery aneurysm present with hypopituitarism due to compression of pituitary gland? Materials & methods: Case report and literature review. Results: We discuss this rare presentation in a middle-aged patient its surgical management and the follow-up course with a review of available literature. Discussion & conclusion: Anterior communicating artery aneurysms extending into the sella are extremely uncommon with only 4 cases reported in literature. They are usually giant aneurysms which are partially thrombosed with presenting with predominantly with mass effect in this case visual impairment and hypofunction of the pituitary.

Endovascular coiling of recurrent trapped pseudoaneurysm of petrous ICA across the distal barrier: When the other way round is the only way around!

BACKGROUND: The pseudoaneurysms of the internal carotid artery (ICA) at the skull base form a unique subset of craniofacial pseudoaneurysms with varied diagnostic and therapeutic challenges. Recurrence in a surgically treated pseudoaneurysm may become a nightmare due to very limited number of open and endovascular options. REPORT: We report a rare case of recurrent pseudoaneurysm of petrous ICA, which presented with massive epistaxis following an initial successful occlusion by surgical trapping of the parent arterial segment with surgical clip. Cerebral angiography revealed filling of the pseudoaneurysm by small arterial channels from the external carotid, contralateral internal carotid and basilar arterial branches and emptying through the "slipped" distal clip. After a meticulous analysis of the cerebral angiogram, the recurrent pseudoaneurysm was eventually embolized retrogradely through the "slipped" clip after crossing the anterior communicating artery taking a contralateral internal carotid access. CONCLUSION: Scrupulous planning and execution of ICA pseudoaneurysms is necessary to prevent recurrence. Naturally occuring collateral routes through the Circle of Willis aid in treatment of "unreachable" vascular lesions.

Reconstructing dual-phase nanometer scale grains within a pearlitic steel tip in 3D through 4D-scanning precession electron diffraction tomography and automated crystal orientation mapping.

The properties of polycrystalline materials are related to their microstructures and hence a complete description, including size, shape, and orientation of the grains, is necessary to understand the behavior of materials. Here, we use Scanning Precession Electron Diffraction (SPED) in the Transmission Electron Microscope (TEM) combined with a tilt series to reconstruct individual grains in 3D within a polycrystalline dual-phase cold wire-drawn pearlitic steel sample. Nanoscale ferrite grains and intragranular cementite particles were indexed using an Automated Crystallographic Orientation Mapping (ACOM) tool for each tilt dataset. The grain orientations were tracked through the tilt datasets and projections of the individual grains were reconstructed from the diffraction data using an orientation-specific Virtual Dark Field (VDF) approach for tomographic reconstruction. The algorithms used to process and reconstruct such datasets are presented. These algorithms represent an extension to the ACOM approach that may be straightforwardly applied to other multi-phase polycrystalline materials to enable 3D spatial and orientation reconstructions.

Surgical Clip Ligation of Anterior Communicating Artery Aneurysm in a Resource-Limited Setting.

Anterior communicating artery (ACOM) aneurysm clipping with intraoperative measures to ensure total occlusion and avoid ischemic complications is standard in countries such as the United States. However, alternatives need to be considered in resource-limited settings. The clipping of an unruptured, superiorly projecting ACOM aneurysm in a resource-limited setting is presented and special nuances that optimize safety are described. Careful surgical technique, meticulous identification of relevant anatomy, post-ligation inspection of the aneurysm and adjacent vessels, and possibly needle puncture of the aneurysm dome are critical to achieve favorable results.

In Situ TEM Observation of Cooperative Grain Rotations and the Bauschinger Effect in Nanocrystalline Palladium.

We report on cooperative grain rotation accompanied by a strong Bauschinger effect in nanocrystalline (nc) palladium thin film. A thin film of nc Pd was subjected to cyclic loading-unloading using in situ TEM nanomechanics, and the evolving microstructural characteristics were investigated with ADF-STEM imaging and quantitative ACOM-STEM analysis. ADF-STEM imaging revealed a partially reversible rotation of nanosized grains with a strong out-of-plane component during cyclic loading-unloading experiments. Sets of neighboring grains were shown to rotate cooperatively, one after the other, with increasing/decreasing strain. ACOM-STEM in conjunction with these experiments provided information on the crystallographic orientation of the rotating grains at different strain levels. Local Nye tensor analysis showed significantly different geometrically necessary dislocation (GND) density evolution within grains in close proximity, confirming a locally heterogeneous deformation response. The GND density analysis revealed the formation of dislocation pile-ups at grain boundaries (GBs), indicating the generation of back stresses during unloading. A statistical analysis of the orientation changes of individual grains showed the rotation of most grains without global texture development, which fits to both dislocation- and GB sliding-based mechanisms. Overall, our quantitative in situ experimental approach explores the roles of these different deformation mechanisms operating in nanocrystalline metals during cyclic loading.

Recurrent Giant Anterior Cerebral Artery (ACA) Aneurysm With Previous Coiling, Attempted Clipping Then Direct ACA-to-ACA Bypass: 2-Dimensional Operative Video.

Giant aneurysms are defined as lesions with a widest diameter of 2.5 cm or greater and account for 2% to 5% of all intracranial aneurysms. These lesions are challenging entities for microsurgical management with techniques such as direct aneurysmal neck clipping, aneurysm neck reconstructions, aneurysmotomy, and aneurysmectomy. This patient had a previously coiled, unruptured, superiorly projecting giant anterior communicating artery (ACom) aneurysm, eccentric toward the left, for which surgical intervention was undertaken. A left orbitozygomatic craniotomy was performed, and a temporary clip was applied to the bilateral proximal A1 segments. Aneurysmotomy was then performed with internal debulking of the aneurysmal thrombus. Aneurysmectomy and removal of the coil mass were performed. Next, the aneurysm neck was reconstructed using multiple surgical clips. After anticipated aneurysm neck reconstruction, indocyanine green (ICG) angiography demonstrated a lack of flow in the ipsilateral A2. The ACom was then transected along the aneurysm neck, and an end-to-end anastomosis of the distal A1 and proximal A2 was performed. Repeat ICG angiography demonstrated patency of the A1-A2 anastomosis. The patient gave informed consent for surgery and video recording. Institutional review board approval was deemed unnecessary. Used with permission from Barrow Neurological Institute, Phoenix, Arizona.

Intraoperative Use of Microscope-Integrated Flow 800 - A Valuable Tool in Surgical Management of Anterior Communicating Artery Aneurysm: Our Institutional Experience.

BACKGROUND: Flow 800 is microscope-integrated analytical visualization tool which analyses the indocyanine green (ICG) video sequence and converts it into an intensity diagram. This allows an objective evaluation of the result rather than subjective assessment of ICG fluorescence. The anatomy of anterior communicating artery region is complex because of multiple vessels and perforators in small space; hence, there is a need of objective assessment tool which can give precise idea about vascular compromise. Flow 800 can serve as a valuable tool in this complex surgery. OBJECTIVE: The objective of this study was to evaluate the utility of microscope-integrated fluorescent ICG videoangiography (Flow 800) in A-com aneurysm surgery. MATERIALS AND METHODS: We used Flow 800 in ten consecutive patients of A-com aneurysm surgery from July 2019 to October 2019. We studied patient characteristics, intraoperative observation of ICG and Flow 800, and corresponding changes made in the operative decisions. RESULTS: The use of Flow 800 helped in intraoperative decision of four out of ten patients of A-com aneurysm. In two patients, incomplete clipping was confirmed with Flow 800 and the second clip was applied. In the third patient, perforator compromise was found hence needed clip readjustment, whereas in the fourth patient, ICG was inconclusive and Flow 800 confirmed complete clipping of aneurysm. CONCLUSION: Flow 800 is a conclusive reproducible and objective tool for early detection of vascular compromise of multiple vessels and perforators in A-com aneurysm surgery. It gives a better idea of vasculature, especially where ICG is ambiguous or inconclusive.

Microsurgical clipping of an unruptured superiorly projecting ACoM aneurysm in a rotated ACoM complex.

This case illustrates surgical technique for wide neck aneurysm clipping in a rotated complex and how to manage intraoperative aneurysm rupture while maintaining hemostasis (Cai et al., Anterior communicating artery aneurysm morphology and the risk of rupture. World Neurosurg. 2018;109:119 and Dehdashti et al., The implication of anterior communicating complex rotation and 3-dimensional computerized tomography angiography findings in surgical approach to anterior communicating artery aneurysms. World Neurosurg. 2016;91:34).

Methods for orientation and phase identification of nano-sized embedded secondary phase particles by 4D scanning precession electron diffraction.

The diffraction patterns acquired with transmission electron microscopes gather reflections from all crystallites that overlap in the foil thickness. The superimposition renders automated orientation or phase mapping difficult, in particular when secondary phase particles are embedded in a dominant diffracting matrix. Several numerical approaches specifically developed to overcome this issue for 4D scanning precession electron diffraction data sets are described. They consist either in emphasizing the signature of the particles or in subtracting the matrix information out of the collected set of patterns. The different strategies are applied successively to a steel sample containing precipitates that are in Burgers orientation relationship with the matrix and to an aluminium alloy with randomly oriented Mn-rich particles.