Comparison of bone subtraction CT angiography with standard CT angiography for evaluating circle of Willis in normal dogs

BACKGROUND

Bone subtraction computed tomography angiography (BSCTA) is a useful alternative technique for improving visualization of vessels surrounded by skull bone. However, no studies have compared computed tomography angiography (CTA) and BSCTA for improving the visibility of canine cerebral blood vessels.

OBJECTIVES

To evaluate the potential benefit of BSCTA for better delineation of brain arteries of the circle of Willis (CoW) in dogs by comparing BSCTA with non-subtraction computed tomography angiography (NSCTA).

METHODS

Brain CTA was performed for nine healthy beagle dogs using a bolus tracking method with saline flushing. A total dose of 600 mgI/kg of contrast agent with an iodine content of 370 mgI/mL was injected at a rate of 4 ml/s. Bone removal was achieved automatically by subtracting non-enhanced computed tomography (CT) data from contrast CT data. Five main intracranial arteries of the CoW were analyzed and graded on a scale of five for qualitative evaluation.

RESULTS

Scores of basilar artery, middle cerebral artery, and rostral cerebral artery in the BSCTA group were significantly higher than those in the NSCTA group (p = 0.001, p = 0.020, and p < 0.0001, respectively). Scores of rostral cerebellar artery (RcA) and caudal cerebral artery (CCA) did not differ significantly between the two groups. However, scores of RcA and CCA in the BSCTA group were higher than those in the NSCTA group.

CONCLUSIONS

BSCTA improved visualization of intracranial arteries of the CoW with close contact to bone. Thus, it should be recommended as a routine scan method in dogs suspected of having brain vessel disease.

Transcranial Doppler Ultrasonography detection on cerebrovascular flow for evaluating neonatal hypoxic-ischemic encephalopathy modeling

Objective

This study aimed to investigate the feasibility of Transcranial Doppler Ultrasonography (TCD) in evaluating neonatal hypoxic-ischemic encephalopathy (NHIE) modeling through monitoring the alteration of cerebrovascular flow in neonatal hypoxic-ischemic (HI) rats.

Methods

Postnatal 7-day-old Sprague Dawley (SD) rats were divided into the control group, HI group, and hypoxia (H) group. TCD was applied to assess the changes of cerebral blood vessels, cerebrovascular flow velocity, and heart rate (HR) in sagittal and coronal sections at 1, 2, 3, and 7 days after the operation. For accuracy, cerebral infarct of rats was examined by 2,3,5-Triphenyl tetrazolium chloride (TTC) staining and Nissl staining to simultaneously verify the establishment of NHIE modeling.

Results

Coronal and sagittal TCD scans revealed obvious alteration of cerebrovascular flow in main cerebral vessels. Obvious cerebrovascular back-flow was observed in anterior cerebral artery (ACA), basilar artery (BA), middle cerebral artery (MCA) of HI rats, along with accelerated cerebrovascular flows in the left internal carotid artery (ICA-L) and BA, decreased flows in right internal carotid artery (ICA-R) relative to those in the H and control groups. The alterations of cerebral blood flows in neonatal HI rats indicated successful ligation of right common carotid artery. Besides, TTC staining further validated the cerebral infarct was indeed caused due to ligation-induced insufficient blood supply. Damage to nervous tissues was also revealed by Nissl staining.

Conclusion

Cerebral blood flow assessment by TCD in neonatal HI rats contributed to cerebrovascular abnormalities observed in a real-time and non-invasive way. The present study elicits the potentials to utilize TCD as an effective means for monitoring the progression of injury as well as NHIE modeling. The abnormal appearance of cerebral blood flow is also beneficial to the early warning and effective detection in clinical practice.

All answers are in the images: A review of deep learning for cerebrovascular segmentation

Cerebrovascular imaging is a common examination. Its accurate cerebrovascular segmentation become an important auxiliary method for the diagnosis and treatment of cerebrovascular diseases, which has received extensive attention from researchers. Deep learning is a heuristic method that encourages researchers to derive answers from the images by driving datasets. With the continuous development of datasets and deep learning theory, it has achieved important success for cerebrovascular segmentation. Detailed survey is an important reference for researchers. To comprehensively analyze the newest cerebrovascular segmentation, we have organized and discussed researches centered on deep learning. This survey comprehensively reviews deep learning for cerebrovascular segmentation since 2015, it mainly includes sliding window based models, U-Net based models, other CNNs based models, small-sample based models, semi-supervised or unsupervised models, fusion based models, Transformer based models, and graphics based models. We organize the structures, improvement, and important parameters of these models, as well as analyze development trends and quantitative assessment. Finally, we have discussed the challenges and opportunities of possible research directions, hoping that our survey can provide researchers with convenient reference.

Risk of intracranial aneurysm recurrence after microsurgical clipping based on 3D digital subtraction angiography

OBJECTIVE

Current knowledge of recurrence rates after intracranial aneurysm (IA) surgery relies on 2D digital subtraction angiography (DSA), which fails to detect more than 75% of small aneurysm remnants. Accordingly, the discrimination between recurrence and growth of a remnant remains challenging, and actual assessment of recurrence risk of clipped IAs could be inaccurate. The authors report, for the first time, 3D-DSA-based long-term durability and risk factor data of IA recurrence and remnant growth after microsurgical clipping.

METHODS

Prospectively collected data for 305 patients, with a total of 329 clipped IAs that underwent baseline 3D-DSA, were evaluated. The incidence of recurrent IA was described by Kaplan-Meier curves. Risk factors for IA recurrence were analyzed by multivariable Cox proportional hazards and logistic regression models.

RESULTS

The overall observed proportion of IA recurrence after clipping was 2.7% (9 of 329 IAs) at a mean follow-up of 46 months (0.7% per year). While completely obliterated IAs did not recur during follow-up, incompletely clipped aneurysms (76 of 329) demonstrated remnant growth in 11.8% (3.4% per year). Young age and large initial IA size significantly increased the risk of IA recurrence.

CONCLUSIONS

The findings support those in previous studies that hypothesized that completely clipped IAs have an extremely low risk of recurrence. Conversely, the results highlight the significant risk posed by incompletely clipped IAs. Young patients with initial large IAs and incomplete obliteration have an especially high risk for IA recurrence and therefore should be monitored more closely.

Asymmetry in cerebral perfusion from circle of Willis arterial variations in normal population

BACKGROUND

Angiographic and cadaveric studies have evidenced variations in the circle of Willis (CoW). Age-related changes in cerebral hemodynamics may be attributable to vascular variations.

OBJECTIVES

The objective is to assess interdependence of completeness of CoW with age using non-invasive MRA and cerebral perfusion using arterial spin labeling (ASL).

METHODS

This single-center, prospective study segregated 189 subjects into three groups: ≤5, 5 to 18, and >18 years. Angiographic (complete CoW and vascular asymmetry index) using TOF and contrast-enhanced- (CE-) MRA, and perfusion (perfusion asymmetry index) data using ASL were obtained.

RESULTS

One hundred and six (56.08%) subjects showed complete CoW on TOF and 100 (52.91%) on CE-MRA. Anterior and posterior collateral pathways were more prevalent in the younger population. Completeness of CoW decreased with increasing age, group 1 (54/60, 90% TOF; 51/60, 85% CE), group 2 (39/64, 60% TOF; 37/64, 56.92% CE), and group 3 (13/65, 20.31% TOF; 12/65, 18.75% CE); p-value < .0001. A statistically significant decrease in cerebral and cerebellar perfusion with increasing age was seen. Cerebellar to frontal perfusion change was higher in group 1. Fetal posterior cerebral artery (PCA) led to ipsilateral low and contralateral hyperperfusion flow asymmetries between occipital lobes.

CONCLUSIONS

This study shows that a complete CoW is commoner in pediatrics than adults and with increasing age, the completeness of CoW decreases paralleled by decrease in cerebral and cerebellar perfusion. There is age-related shift of perfusion from hindbrain to forebrain and the regression of PCoA occurs with increasing age leading to alterations in cerebral perfusion and hemodynamics.

Digital subtraction angiography in cerebrovascular disease: current practice and perspectives on diagnosis, acute treatment and prognosis

Digital Subtraction Angiography (DSA) is the gold-standard imaging modality in acute cerebrovascular diagnosis. The role of DSA has become increasingly prominent since the incorporation of endovascular therapy in standards of care for acute ischemic stroke. It is used in the assessment of cerebral vessel patency; however, the therapeutic role of DSA from a prognostic standpoint merits further investigation. The current paper provides an update on current practice on diagnostic, therapeutic and prognostic use of DSA in acute cerebrovascular diseases and various indications and perspectives that may apply, or limit its use, in ongoing surveillance or prognosis. Pre-clinical and clinical studies on the aspects, including but not limited to the morphology of cerebrovasculature in acute ischaemic stroke, are required to delineate and inform its prognostic role.

Normal cerebral blood vessels under ultrasound in SD rats of different ages

The objective of this study was to examine whether ultrasound can examine the development of cerebral vascular structure and cerebral blood flow in Sprague-Dawley (SD) rats by ultrasound in a noninvasive manner, which provides a reference for ultrasound research of SD rats. Thirty-nine SD rats (7-16 days old) were divided into seven groups according to age, and the number of SD rats in each group was, respectively, 7, 17, 1, 3, 2, 8, and 1. Ultrasound was used to detect cerebral blood vessels, cerebrovascular flow velocity, and heart rate in SD rats in the sagittal and coronal positions, and images were obtained in B-mode ultrasound. The cerebral vascular structure of 39 SD rats (7-16 days) was dynamically observed under B-ultrasound. We found that the cerebral vascular structure of the rats aged 7-10 days was clear and detectable. Rats aged 11-16 days of cerebral vascular structures became thinner and undetectable. Quantitative analysis of cerebrovascular flow rate and heart rate in rats found that there was no significant difference in cerebrovascular blood flow rate and heart rate between 7 and 8 days. Ultrasound can also be used in rat animal studies, that is, the cerebral blood flow in rats of different ages can be monitored in real-time by ultrasound in a noninvasive way.

Moyamoya Vasculopathy: Cause, Clinical Manifestations, Neuroradiologic Features, and Surgical Management

In moyamoya disease, the progressive occlusion of the distal portion of the internal carotid artery and its major branches is typically responsible for the formation of an extensive network of collateral vessels at the base of the brain. When moyamoya collateral network develops in association with various systemic or acquired diseases, the term moyamoya syndrome is used to denote this phenomenon. Sudden changes in the supraclinoid internal carotid artery and middle cerebral artery can be recognized with noninvasive neurovascular imaging techniques, which also allow a differential diagnosis with similar diseases such as degenerative steno-occlusive disease, cerebral vasculitis, and twig-like middle cerebral artery. Once the diagnosis is established, the definitive treatment for moyamoya disease is surgical revascularization, with the goal of increasing cerebral blood flow and preventing recurrent stroke. We provide a comprehensive review of the clinical and radiologic features in moyamoya vasculopathy along with its surgical management.

Atypical intracranial aneurysms: spectrum of imaging findings in computed tomography and magnetic resonance imaging

We aim to describe demographics, clinical presentation, and spectrum of CT and MRI features suggestive of atypical intracranial aneurysms. The imaging protocols used for the diagnosis of intracranial aneurysms were thoroughly reviewed, including different CT and MRI protocols. We classified atypical aneurysms according to their location, size, clinical presentation, and specific imaging features. Dissecting aneurysms are one of the causes of stroke in young adults that may show intimal flap and double lumen. Traumatic intracranial aneurysms are a rare but serious complication of head injuries. Mycotic aneurysms are small and multiple at distal branch points with a high risk of rupture. Aneurysms with vasculitis are fusiform with a wide neck at a non-branch point that may be associated with vessel wall enhancement. Atherosclerotic aneurysms are usually large fusiform that affect large arteries. Oncotic aneurysms are relatively rare. They were reported to occur in patients with left atrial myxoma. Our study represented a wide spectrum of atypical intracranial aneurysms with their detailed diagnostic imaging findings on MRI and CT including newly introduced MRI sequences, which greatly influenced early diagnosis and timely management.

Value of 3-Dimensional Digital Subtraction Angiography for Detection and Classification of Intracranial Aneurysm Remnants After Clipping

BACKGROUND

The current gold standard for evaluation of the surgical result after intracranial aneurysm (IA) clipping is two-dimensional (2D) digital subtraction angiography (DSA). While there is growing evidence that postoperative 3D-DSA is superior to 2D-DSA, there is a lack of data on intraoperative comparison.

OBJECTIVE

To compare the diagnostic yield of detection of IA remnants in intra- and postoperative 3D-DSA, categorize the remnants based on 3D-DSA findings, and examine associations between missed 2D-DSA remnants and IA characteristics.

METHODS

We evaluated 232 clipped IAs that were examined with intraoperative or postoperative 3D-DSA. Variables analyzed included patient demographics, IA and remnant distinguishing characteristics, and 2D- and 3D-DSA findings. Maximal IA remnant size detected by 3D-DSA was measured using a 3-point scale of 2-mm increments.

RESULTS

Although 3D-DSA detected all clipped IA remnants, 2D-DSA missed 30.4% (7 of 23) and 38.9% (14 of 36) clipped IA remnants in intraoperative and postoperative imaging, respectively (95% CI: 30 [ 12, 49] %; P-value .023 and 39 [23, 55] %; P-value = <.001), and more often missed grade 1 (< 2 mm) clipped remnants (odds ratio [95% CI]: 4.3 [1.6, 12.7], P-value .005).

CONCLUSION

Compared with 2D-DSA, 3D-DSA achieves a better diagnostic yield in the evaluation of clipped IA. Our proposed method to grade 3D-DSA remnants proved to be simple and practical. Especially small IA remnants have a high risk to be missed in 2D-DSA. We advocate routine use of either intraoperative or postoperative 3D-DSA as a baseline for lifelong follow-up of clipped IA.

Inner diameters of the normal carotid arteries measured using three-dimensional digital subtraction catheter angiography: a retrospective analysis

Purpose

To obtain normal ranges for the inner diameters of the carotid arteries.

Methods

This retrospective analysis included consecutive patients with disease-free carotid arteries who had undergone 3D-DSA at two hospitals in Nanning, Guangxi, between March 2013 and March 2018. Demographic and clinical characteristics, including Essen Stroke Risk Score (ESRS), were extracted from the medical records. The 3D-DSA data were used to calculate the inner diameters of the carotid arteries.

Results

The analysis included 1182 patients (837 males) aged 58.81 ± 11.02 years. The inner diameters of the proximal carotid sinus (CS), CS bulge, distal CS, and common carotid artery (CCA) were larger on the right than on the left (P < 0.05). The inner diameters of the proximal CS, CS bulge, distal CS, and CCA on both sides were larger for males than females (P < 0.05). The inner diameters of the proximal CS, CS bulge, and distal CS on both sides were smaller for patients aged > 65 years than for patients aged ≤ 55 years (P < 0.05). Right CCA inner diameter did not vary with age, whereas left CCA inner diameter was larger for patients aged > 55 years than for patients aged ≤ 45 years (P < 0.05). The inner diameters of the proximal CS, CS bulge, and distal CS on both sides were smaller for patients with ESRS ≥ 3 than those with ESRS < 3 (P < 0.05).

Conclusion

This study provides reference values for the internal diameters of normal carotid arteries. Carotid artery diameters varied with side, sex, and age.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-021-02328-z.

Optimal placement of the region of interest for bolus tracking on brain computed tomography angiography in Beagle dogs

This study aimed to determine the optimal placement of the region of interest (ROI) among four anatomical sites-pulmonary artery (PA), pulmonary vein (PV), aortic arch (AA), and carotid artery (CA)-in computed tomography (CT) brain angiography with automatic bolus tracking in healthy beagle dogs. Six beagles were included, and CT brain angiography was performed four times for each dog, to cover each ROI. The scan parameters, amount, and injection rate of the contrast medium were the same. The major intracranial arteries were selected for quantitative and qualitative evaluation: caudal cerebellar artery (CcA), basilar artery (BA), rostral cerebellar artery (RcA), caudal cerebral artery (CCA), middle cerebral artery (MCA), and rostral cerebral artery (RCA). Quantitative evaluation showed significantly higher CT attenuation values for the RcA, CCA, and MCA in the PA group and RcA and MCA in the PV group than in the CA group. Qualitative analysis revealed significantly higher scores for the BA, CCA, and MCA in the PA and PV groups than in the CA group. Venous contamination did not differ significantly among the ROIs, but the mean scores of the AA and CA groups were higher than those of the PA and PV groups. CT brain angiography using bolus tracking in the beagle dogs showed that the ROI should be placed at the PA or PV rather than at the CA for optimal images with strong contrast enhancement of the BA, RcA, CCA, and MCA and minimal venous contamination.

Temporal-Spatial Feature Extraction of DSA Video and Its Application in AVM Diagnosis

Objectives: Brain arteriovenous malformation (AVM) is one of the most common causes of intracranial hemorrhage in young adults, and its expeditious diagnosis on digital subtraction angiography (DSA) is essential for clinical decision-making. This paper firstly proposed a deep learning network to extract vascular time-domain features from DSA videos. Then, the temporal features were combined with spatial radiomics features to build an AVM-assisted diagnosis model. Materials and method: Anteroposterior position (AP) DSA videos from 305 patients, 153 normal and 152 with AVM, were analyzed. A deep learning network based on Faster-RCNN was proposed to track important vascular features in DSA. Then the appearance order of important vascular structures was quantified as the temporal features. The structure distribution and morphological features of vessels were quantified as 1,750 radiomics features. Temporal features and radiomics features were fused in a classifier based on sparse representation and support vector machine. An AVM diagnosis and grading system that combined the temporal and spatial radiomics features of DSA was finally proposed. Accuracy (ACC), sensitivity (SENS), specificity (SPEC), and area under the receiver operating characteristic curve (AUC) were calculated to evaluate the performance of the radiomics model. Results: For cerebrovascular structure detection, the average precision (AP) was 0.922, 0.991, 0.769, 0.899, and 0.929 for internal carotid artery, Willis circle, vessels, large veins, and venous sinuses, respectively. The mean average precision (mAP) of five time phases was 0.902. For AVM diagnosis, the models based on temporal features, radiomics features, and combined features achieved AUC of 0.916, 0.918, and 0.942, respectively. In the AVM grading task, the proposed combined model also achieved AUC of 0.871 in the independent testing set. Conclusion: DSA videos provide rich temporal and spatial distribution characteristics of cerebral blood vessels. Clinicians often interpret these features based on subjective experience. This paper proposes a scheme based on deep learning and traditional machine learning, which effectively integrates the complex spatiotemporal features in DSA, and verifies the value of this scheme in the diagnosis of AVM.

Detection of clustered anomalies in single-voxel morphometry as a rapid automated method for identifying intracranial aneurysms

Unruptured intracranial aneurysms (UIAs) are prevalent neurovascular anomalies which, in rare circumstances, rupture to cause a catastrophic subarachnoid haemorrhage. Although surgical management can reduce rupture risk, the majority of UIAs exist undiscovered until rupture. Current clinical practice in the detection of UIAs relies heavily on manual radiological review of standard imaging modalities. Recent computer-aided UIA diagnoses can sensitively detect and measure UIAs within cranial angiograms but remain limited to low specificities whose output also requires considerable radiologist interpretation not amenable to broad screening efforts. To address these limitations, we have developed a novel automatic pipeline algorithm which inputs medical images and outputs detected UIAs by characterising single-voxel morphometry of segmented neurovasculature. Once neurovascular anatomy of a specified resolution is segmented, correlations between voxel-specific morphometries are estimated and spatially-clustered outliers are identified as UIA candidates. Our automated solution detects UIAs within magnetic resonance angiograms (MRA) at unmatched 86% specificity and 81% sensitivity using 3 min on a conventional laptop. Our approach does not rely on interpatient comparisons or training datasets which could be difficult to amass and process for rare incidentally discovered UIAs within large MRA files, and in doing so, is versatile to user-defined segmentation quality, to detection sensitivity, and across a range of imaging resolutions and modalities. We propose this method as a unique tool to aid UIA screening, characterisation of abnormal vasculature in at-risk patients, morphometry-based rupture risk prediction, and identification of other vascular abnormalities.

Comparison of Intra- and Postoperative 3-Dimensional Digital Subtraction Angiography in Evaluation of the Surgical Result After Intracranial Aneurysm Treatment

BACKGROUND

Postoperative three-dimensional digital subtraction angiography (3D-DSA) is the gold standard in evaluating intracranial aneurysm (IA) remnants after clipping. Should intraoperative 3D-DSA image quality be equally good as postoperative 3D-DSA, it could supplant the latter as standard of care for follow-up of clipped IA.

OBJECTIVE

To directly compare the quality of assessment of clipped IA by intraoperative and postoperative 3D-DSA.

METHODS

From a prospective cohort of 221 consecutive patients who underwent craniotomy for IA treatment in a hybrid operating room, we retrospectively studied 26 patients who had both intraoperative and postoperative 3D-DSA imaging of their clipped aneurysm. Comparison of intraoperative and postoperative 3D-DSA images (blinded for review) included parameters that affected image quality and differences between the 2 periods.

RESULTS

In the 26 patients with 32 clipped IAs, the mean interval was 11 ± 7 mo between intraoperative and postoperative imaging 3D-DSA examinations. Reconstruction with multiple clips was used in 14 (44%) cases. Of 15 remnants, 9 (60%) were small (<2 mm). In comparing intraoperative and postoperative 3D-DSA, no discordance or discrepancy in assessment of the surgical result was noted for any clipped IA, and overall imaging quality was excellent for both modalities. Factors affecting minor differences in image quality were not identified.

CONCLUSION

Compared with postoperative 3D-DSA, intraoperative 3D-DSA images achieved equally high quality and effective, immediate interpretation of the surgical clipping result. With comparable imaging quality and no discordant findings, intraoperative 3D-DSA could replace postoperative 3D-DSA to become the standard of care in IA surgery.

[Detection of peripheral artery disease in patients with ischemic heart disease. A quick guide for medical practitioners]

In this manual, the authors focused on the principal methods for diagnosis of peripheral artery disease in cardiological patients, from the interview and physical examination to functional tests and vascular visualization. Diagnostic and prognostic value of each method, its potentialities for reducing the risk of cardiovascular events (CVE), including myocardial infarction (MI), ischemic stroke (IS) or extremity amputation in critical ischemia, and overall mortality are discussed. The authors provided current information about a possibility of reducing the risk of CVE by intensifying the antithrombotic therapy according to results of the COMPASS study.

Fluorescent AIE-Active Materials for Two-Photon Bioimaging Applications

Fluorescence imaging has been widely used as a powerful tool for in situ and real-time visualization of important analytes and biological events in live samples with remarkably high selectivity, sensitivity, and spatial resolution. Compared with one-photon fluorescence imaging, two-photon fluorescence imaging exhibits predominant advantages of minimal photodamage to samples, deep tissue penetration, and outstanding resolution. Recently, the aggregation-induced emission (AIE) materials have become a preferred choice in two-photon fluorescence biological imaging because of its unique bright fluorescence in solid and aggregate states and strong resistance to photobleaching. In this review, we will exclusively summarize the applications of AIE-active materials in two-photon fluorescence imaging with some representative examples from four aspects: fluorescence detection, in vitro cell imaging, ex vivo tissue imaging, and in vivo vascular imaging. In addition, the current challenges and future development directions of AIE-active materials for two-photon bioimaging are briefly discussed.

On the Use of Digital Subtraction Angiography in Stereoelectroencephalography Surgical Planning to Prevent Collisions with Vessels

OBJECTIVE

Stereoelectroencephalography (SEEG) consists of the implantation of microelectrodes for the electrophysiological characterization of epileptogenic networks. To reduce a possible risk of intracranial bleeding by vessel rupture during the electrode implantation, the stereotactic trajectories must follow avascular corridors. The use of digital subtraction angiography (DSA) for vascular visualization during planning is controversial due to the additional risk related to this procedure. Here we evaluate the utility of this technique for planning when the neurosurgeon has it available together with gadolinium-enhanced T1-weighted magnetic resonance sequence (T1-Gd) and computed tomography angiography (CTA).

METHODS

Twenty-two implantation plans for SEEG were initially done using T1-Gd imaging (251 trajectories). DSA was only used later during the revision process. In 6 patients CTA was available at this point as well. We quantified the position of the closest vessel to the trajectory in each of the imaging modalities.

RESULTS

Two thirds of the trajectories that appeared vessel free in the T1-Gd or CTA presented vessels in their proximity, as shown by DSA. Those modifications only required small shifts of both the entry and target point, so the diagnostic aims were preserved.

CONCLUSIONS

T1-Gd and CTA, despite being the most commonly used techniques for SEEG planning, frequently fail to reveal vessels that are dangerously close to the trajectories. Higher-resolution vascular imaging techniques, such as DSA, can provide the neurosurgeon with crucial information about vascular anatomy, resulting in safer plans.

Blood flow simulations in patient-specific geometries of the carotid artery: A systematic review

Computational Fluid Dynamics (CFD) and Fluid-Structure Interaction (FSI) are currently widely applied in the study of blood flow parameters and their alterations under pathological conditions, which are important indicators for diagnosis of atherosclerosis. In this manuscript, a systematic review of the published literature was conducted, according to the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses, on the simulation studies of blood flow in patient-specific geometries of the carotid artery bifurcation. Scopus, PubMed and ScienceDirect databases were used in the literature search, which was completed on the 3rd of August 2020. Forty-nine articles were included after the selection process and were organized in two distinct categories: the CFD studies (36/49 articles), which comprise only the fluid analysis and the FSI studies (13/49 articles), which includes both fluid and Fluid-Structure domain in the analysis. The data of the research works was structured in different categories (Geometry, Viscosity models, Type of Flow, Boundary Conditions, Flow Parameters, Type of Solver and Validation). The aim of this systematic review is to demonstrate the methodology in the modelling, simulation and analysis of carotid blood flow and also identify potential gaps and challenges in this research field.

Vessel wall MR imaging for the detection of intracranial inflammatory vasculopathies

Intracranial vasculopathies are routinely investigated by lumen-based modalities such as magnetic resonance angiography (MRA), computed tomography angiography (CTA), and digital subtraction angiography (DSA). These techniques are useful to analyze the vessel lumen, allowing to detect vessel stenosis or occlusion. However, the primum movins of the disease, i.e., an abnormal thickening of the vessel wall, remains within the arterial wall. The vasculopathy can moreover be present without always narrowing the lumen or modifying its regularity. Hence, there is a need to detect directly and analyze vessel wall abnormalities. Development of 3D high-resolution black blood sequences for intracranial vessel wall MR imaging (VW-MRI) enabled routine clinical applications not only vasculitis, but also of intracranial atherosclerotic disease (ICAD), intracranial dissections, reversible intracranial dissections, reversible cerebral vasoconstriction syndrome (RCVS), Moyamoya disease, and intracranial aneurysms. This high-resolution intracranial VW- MRI approach is increasingly used on a clinical basis at many centers to solve diagnostic problems, especially in patients with ischemic stroke or intracranial hemorrhage. An expert consensus Guideline from the American Society of Neuroradiology provides recommendations for clinical implementation of intracranial vessel wall MRI. There are several technical aspects needed to be considered when implementing VW-MRI in intracranial vessels, including flow suppression, both in blood and cerebrospinal fluid (CSF), spatial resolution and signal-to-noise ratio (SNR). In this article, we review the technical aspects of VW-MRI, and recommend applications for vascular diseases including non-occlusive intracranial vasculopathies, Moyamoya disease, and identifying culprit plaques. We also give a focus on the utility of VW-MRI for determining stroke etiology in adults and in children and young adults.

Detailed Analysis of the Space between the Semicircular Canals for the Purpose of Direct Bone Conduction Stimulation of the Inner Ear

INTRODUCTION

Until recently, all locations for bone conduction (BC) stimulator described in the literature were situated outside of the real otic capsule. In recent studies 2 new sites for the BC titanium implant were proposed to directly stimulate the cochlea from the closest possible distance, which was the bone forming the ampulla of the lateral semicircular canal (SC) and the bone between the superior and lateral SC. They proved to be the most efficient in terms of transmission of vibratory energy into the inner ear and could be introduced in the field of BC hearing rehabilitation. To the best of our knowledge the anatomy of the space between SC has not been studied so far. However, screwing the BC implant into the proposed new locations directly at the otic capsule and drilling the bone near the SC cast doubt on the safety of this procedure. In this study we aimed to present a detailed analysis of the anatomy of the otic capsule, especially as regards the space between the SC that seems to be safer.

METHODS

Sixteen fresh frozen cadaveric temporal bones scanned with micro-computed tomography and analyzed using the multiplanar reconstruction option. The anatomy of the space between the SC was analyzed in detail for the purpose of direct BC stimulation of the inner ear.

RESULTS

At least 3 mm of bony tissue is available above the bony space between the crura of the superior SC above the lateral SC, where the new location for the titanium BC implant is proposed. As regards the limitations of the length of screw the BC implant to be screwed, the smallest distance is at least 4 mm of bone thickness.

CONCLUSIONS

The bone between the crura of the superior SC is the best placement to screw the BC implant directly to the otic capsule. The implant direction should be parallel to the plane of the lateral SC. This location, the direction, and the limitation of the screw length of the BC implant to a maximum of 7 mm present the lowest potential risk of damage to the inner ear.

CerebroVis: Designing an Abstract yet Spatially Contextualized Cerebral Artery Network Visualization

Blood circulation in the human brain is supplied through a network of cerebral arteries. If a clinician suspects a patient has a stroke or other cerebrovascular condition, they order imaging tests. Neuroradiologists visually search the resulting scans for abnormalities. Their visual search tasks correspond to the abstract network analysis tasks of browsing and path following. To assist neuroradiologists in identifying cerebral artery abnormalities, we designed CerebroVis, a novel abstract-yet spatially contextualized-cerebral artery network visualization. In this design study, we contribute a novel framing and definition of the cerebral artery system in terms of network theory and characterize neuroradiologist domain goals as abstract visualization and network analysis tasks. Through an iterative, user-centered design process we developed an abstract network layout technique which incorporates cerebral artery spatial context. The abstract visualization enables increased domain task performance over 3D geometry representations, while including spatial context helps preserve the user's mental map of the underlying geometry. We provide open source implementations of our network layout technique and prototype cerebral artery visualization tool. We demonstrate the robustness of our technique by successfully laying out 61 open source brain scans. We evaluate the effectiveness of our layout through a mixed methods study with three neuroradiologists. In a formative controlled experiment our study participants used CerebroVis and a conventional 3D visualization to examine real cerebral artery imaging data to identify a simulated intracranial artery stenosis. Participants were more accurate at identifying stenoses using CerebroVis (absolute risk difference 13%). A free copy of this paper, the evaluation stimuli and data, and source code are available at osf.io/e5sxt.

Four simultaneous anterior cerebral artery aneurysms (three initially unsuspected) with surgical treatment

Distal anterior cerebral artery aneurysms are rare, comprising approximately 6% of all intracranial aneurysms. These aneurysms tend to be smaller in size, broad-based, associated with additional aneurysms and at arterial branching sites, which can make both diagnosis and treatment difficult. Here we report a case of a 63-year-old female who presented with headache and perioral paresthesia determined to be Hunt & Hess scale grade 1. Computed tomography angiography discovered a medium-sized left A2 trunk saccular aneurysm. Intraoperatively 2 additional small blister type aneurysms not noted on initial computed tomography were discovered and treated via clipping and wrapping, respectively. Postoperatively a cerebral angiogram revealed an additional small right A2 trunk broad-based aneurysm. Preoperative evaluation of cerebral vasculature with a cerebral angiogram or high-resolution digital subtraction angiography is essential as multiple aneurysms are commonly associated with anterior cerebral artery aneurysms. The patient was successfully treated without any operative or postoperative complications and has remained symptom-free at 1 year follow up.

NIR-II-Excited Intravital Two-Photon Microscopy Distinguishes Deep Cerebral and Tumor Vasculatures with an Ultrabright NIR-I AIE Luminogen

Intravital fluorescence imaging of vasculature morphology and dynamics in the brain and in tumors with large penetration depth and high signal-to-background ratio (SBR) is highly desirable for the study and theranostics of vascular-related diseases and cancers. Herein, a highly bright fluorophore (BTPETQ) with long-wavelength absorption and aggregation-induced near-infrared (NIR) emission (maximum at ≈700 nm) is designed for intravital two-photon fluorescence (2PF) imaging of a mouse brain and tumor vasculatures under NIR-II light (1200 nm) excitation. BTPETQ dots fabricated via nanoprecipitation show uniform size of around 42 nm and a high quantum yield of 19 ± 1% in aqueous media. The 2PF imaging of the mouse brain vasculatures labeled by BTPETQ dots reveals a 3D blood vessel network with an ultradeep depth of 924 µm. In addition, BTPETQ dots show enhanced 2PF in tumor vasculatures due to their unique leaky structures, which facilitates the differentiation of normal blood vessels from tumor vessels with high SBR in deep tumor tissues. Moreover, the extravasation and accumulation of BTPETQ dots in deep tumor (more than 900 µm) is visualized under NIR-II excitation. This study highlights the importance of developing NIR-II light excitable efficient NIR fluorophores for in vivo deep tissue and high contrast tumor imaging.

Stereoelectroencephalography electrode placement: Detection of blood vessel conflicts

OBJECTIVE

Various forms of vascular imaging are performed to identify vessels that should be avoided during stereoelectroencephalography (SEEG) planning. Digital subtraction angiography (DSA) is the gold standard for intracranial vascular imaging. DSA is an invasive investigation, and a balance is necessary to identify all clinically relevant vessels and not to visualize irrelevant vessels that may unnecessarily restrict electrode placement. We sought to estimate the size of vessels that are clinically significant for SEEG planning.

METHODS

Thirty-three consecutive patients who underwent 354 SEEG electrode implantations planned with computer-assisted planning and DSA segmentation between 2016 and 2018 were identified from a prospectively maintained database. Intracranial positions of electrodes were segmented from postimplantation computed tomography scans. Each electrode was manually reviewed using "probe-eye view" with the raw preoperative DSA images for vascular conflicts. The diameter of vessels and the location of conflicts were noted. Vessel conflicts identified on raw DSA images were cross-referenced against other modalities to determine whether the conflict could have been detected.

RESULTS

One hundred sixty-six vessel conflicts were identified between electrodes and DSA-identified vessels, with 0-3 conflicts per electrode and a median of four conflicts per patient. The median diameter of conflicting vessels was 1.3 mm (interquartile range [IQR] = 1.0-1.5 mm). The median depth of conflict was 31.0 mm (IQR = 14.3-45.0 mm) from the cortical surface. The addition of sulcal models to DSA, magnetic resonance venography (MRV), and T1 + gadolinium images, as an exclusion zone during computer-assisted planning, would have prevented the majority of vessel conflicts. We were unable to determine whether vessels were displaced or transected by the electrodes.

SIGNIFICANCE

Vascular segmentation from DSA images was significantly more sensitive than T1 + gadolinium or MRV images. Electrode conflicts with vessels 1-1.5 mm in size did not result in a radiologically detectable or clinically significant hemorrhage and could potentially be excluded from consideration during SEEG planning.