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  • 1
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    4D-CT angiography versus 3D-rotational angiography as the imaging modality for computational fluid dynamics of cerebral aneurysms
    BMJ ; 2020
    In:  Journal of NeuroInterventional Surgery Vol. 12, No. 6 ( 2020-06), p. 626-630
    Details
    In: Journal of NeuroInterventional Surgery, BMJ, Vol. 12, No. 6 ( 2020-06), p. 626-630
    Abstract: Computational fluid dynamics (CFD) can provide valuable information regarding intracranial hemodynamics. Patient-specific models can be segmented from various imaging modalities, which may influence the geometric output and thus hemodynamic results. This study aims to compare CFD results from aneurysm models segmented from three-dimensional rotational angiography (3D-RA) versus novel four-dimensional CT angiography (4D-CTA). Methods Fourteen patients with 16 cerebral aneurysms underwent novel 4D-CTA followed by 3D-RA. Endoluminal geometries were segmented from each modality using an identical workflow, blinded to the other modality, to produce 28 'original' models. Each was then minimally edited a second time to match length of branches, producing 28 additional 'matched' models. CFD simulations were performed using estimated flow rates for 'original' models (representing real-world experience) and patient-specific flow rates from 4D-CTA for 'matched' models (to control for influence of modality alone). Results Overall, geometric and hemodynamic results were consistent between models segmented from 3D-RA and 4D-CTA, with correlations improving after matching to control for operator-introduced variability. Despite smaller 4D-CTA parent artery diameters (3.49±0.97 mm vs 3.78±0.92 mm for 3D-RA; p=0.005) and sac volumes (157 (37–750 mm 3 ) vs 173 (53–770 mm 3 ) for 3D-RA; p=0.0002), sac averages of time-averaged wall shear stress (TAWSS), oscillatory shear (OSI), and high frequency fluctuations (measured by spectral power index, SPI) were well correlated between 3D-RA and 4D-CTA 'matched' control models (TAWSS, R 2 =0.91; OSI, R 2 =0.79; SPI, R 2 =0.90). Conclusions Our study shows that CFD performed using 4D-CTA models produces reliable geometric and hemodynamic information in the intracranial circulation. 4D-CTA may be considered as a follow-up imaging tool for hemodynamic assessment of cerebral aneurysms.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    URL: Article
    DOI: 10.1136/neurintsurg-2019-015389
    Language: English
    Publisher: BMJ
    Publication Date: 2020
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  • 2
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    Improving visualization of three-dimensional aneurysm features via segmentation with upsampled resolution and gradient enhancement (SURGE)
    BMJ ; 2023
    In:  Journal of NeuroInterventional Surgery Vol. 15, No. 8 ( 2023-08), p. 760-765
    Details
    In: Journal of NeuroInterventional Surgery, BMJ, Vol. 15, No. 8 ( 2023-08), p. 760-765
    Abstract: Intracranial aneurysm neck width tends to be overestimated when measured with three-dimensional rotational angiography (3DRA) compared with two-dimensional digital subtraction angiography (2D-DSA), owing to high curvature at the neck. This may affect morphological and hemodynamic analysis in support of treatment planning. We present and validate a method for extracting high curvature features, such as aneurysm ostia, during segmentation of 3DRA images. Methods In our novel SURGE (segmentation with upsampled resolution and gradient enhancement) approach, the gradient of an upsampled image is sharpened before gradient-based watershed segmentation. Neck measurements were performed for both standard and SURGE segmentations of 3DRA for 60 consecutive patients and compared with those from 2D-DSA. Those segmentations were also qualitatively compared for surface topology and morphology. Results Compared with the standard watershed method, SURGE reduced neck measurement error relative to 2D-DSA by 〉 60%: median error was 0.49 mm versus 0.17 mm for SURGE, which is less than the average pixel resolution (~0.33 mm) of the 3DRA dataset. SURGE reduced neck width overestimations 〉 1 mm from 13/60 to 5/60 cases. Relative to 2D-DSA, standard segmentations were overestimated by 16% and 93% at median and 95th percentiles, respectively, compared with only 6% and 37%, respectively, for SURGE. Conclusion SURGE provides operators with high-level control of the image gradient, allowing recovery of high-curvature features such as aneurysm ostia from 3DRA where conventional algorithms may fail. Compared with standard segmentation and tedious manual editing, SURGE provides a faster, easier, and more objective method for assessing aneurysm ostia and morphology.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    URL: Article
    DOI: 10.1136/neurintsurg-2022-018912
    Language: English
    Publisher: BMJ
    Publication Date: 2023
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  • 3
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    Robotic-assisted intracranial aneurysm treatment: 1 year follow-up imaging and clinical outcomes
    BMJ ; 2022
    In:  Journal of NeuroInterventional Surgery Vol. 14, No. 12 ( 2022-12), p. 1229-1233
    Details
    In: Journal of NeuroInterventional Surgery, BMJ, Vol. 14, No. 12 ( 2022-12), p. 1229-1233
    Abstract: The use of robotics in medicine may enable increased technical accuracy, reduced procedural time and radiation exposure, and remote completion of procedures. We have previously described the first-in-human, robotic-assisted cerebral aneurysm treatment using the CorPath GRX Robotic System. In this report we discuss our early experiences and outcomes using this robotic device for endovascular treatment of intracranial aneurysms using stent-assisted coil embolization and flow diversion. Methods The patient and disease characteristics, procedural details, and follow-up imaging and clinical outcomes of consecutive patients undergoing robotically-assisted intracranial aneurysm embolization between November 2019 and February 2020 are presented. Results Six patients underwent robotically-assisted embolization of intracranial aneurysms. Four of the patients were treated with a neck-bridging stent (with or without coiling) and two patients were treated with a flow-diverting stent. Two patients were treated in the subacute period of subarachnoid hemorrhage and four patients were treated electively. All of the procedures could be completed robotically and there was no need for unplanned manual intervention. The technical success rate of the procedures was 100%. There was no morbidity or mortality associated with the procedures. One year follow-up imaging showed that four aneurysms were completely obliterated (Raymond-Roy Occlusion Classification (RROC) class I) and the remaining two were occluded with a residual neck (RROC class II). Conclusions The Corpath GRX Robotic System demonstrated a precise control over the microcatheter, wire and stent during aneurysm treatment. Robotic neuro-procedures seem to be safe and effective and demonstrate stable occlusion results in the midterm follow-up.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    URL: Article
    DOI: 10.1136/neurintsurg-2021-017865
    Language: English
    Publisher: BMJ
    Publication Date: 2022
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  • 4
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    How patient-specific do internal carotid artery inflow rates need to be for computational fluid dynamics of cerebral aneurysms?
    BMJ ; 2021
    In:  Journal of NeuroInterventional Surgery Vol. 13, No. 5 ( 2021-05), p. 459-464
    Details
    In: Journal of NeuroInterventional Surgery, BMJ, Vol. 13, No. 5 ( 2021-05), p. 459-464
    Abstract: Computational fluid dynamics (CFD) has become a popular tool for studying ‘patient-specific’ blood flow dynamics in cerebral aneurysms; however, rarely are the inflow boundary conditions patient-specific. We aimed to test the impact of widespread reliance on generalized inflow rates. Methods Internal carotid artery (ICA) flow rates were measured via 2D cine phase-contrast MRI for 24 patients scheduled for endovascular therapy of an ICA aneurysm. CFD models were constructed from 3D rotational angiography, and pulsatile inflow rates imposed as measured by MRI or estimated using an average older-adult ICA flow waveform shape scaled by a cycle-average flow rate (Q avg ) derived from the patient’s ICA cross-sectional area via an assumed inlet velocity. Results There was good overall qualitative agreement in the magnitudes and spatial distributions of time-averaged wall shear stress (TAWSS), oscillatory shear index (OSI), and spectral power index (SPI) using generalized versus patient-specific inflows. Sac-averaged quantities showed moderate to good correlations: R 2 =0.54 (TAWSS), 0.80 (OSI), and 0.68 (SPI). Using patient-specific Q avg to scale the generalized waveform shape resulted in near-perfect agreement for TAWSS, and reduced bias, but not scatter, for SPI. Patient-specific waveform had an impact only on OSI correlations, which improved to R 2 =0.93. Conclusions Aneurysm CFD demonstrates the ability to stratify cases by nominal hemodynamic ‘risk’ factors when employing an age- and vascular-territory-specific recipe for generalized inflow rates. Q avg has a greater influence than waveform shape, suggesting some improvement could be achieved by including measurement of patient-specific Q avg into aneurysm imaging protocols.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    URL: Article
    DOI: 10.1136/neurintsurg-2020-015993
    Language: English
    Publisher: BMJ
    Publication Date: 2021
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  • 5
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    Virtual stenting of intracranial aneurysms: A pilot study for the prediction of treatment success based on hemodynamic simulations
    SAGE Publications ; 2018
    In:  The International Journal of Artificial Organs Vol. 41, No. 11 ( 2018-11), p. 698-705
    Details
    In: The International Journal of Artificial Organs, SAGE Publications, Vol. 41, No. 11 ( 2018-11), p. 698-705
    Abstract: Endovascular treatment of intracranial aneurysms using flow-diverting devices has revolutionized the treatment of large and complex lesions due to its minimally invasive nature and potential clinical outcomes. However, incomplete or delayed occlusion and persistent intracranial aneurysm growth are still an issue for up to one-third of the patients. We evaluated two patients with intracranial aneurysm located at the internal carotid artery who were treated with flow-diverting devices and had opposite outcomes. Both patients presented with similar aneurysms and were treated with the same device, but after a 1-year follow-up, one case presented with complete occlusion (Case 1) and the other required further treatment (Case 2). To reproduce the interventions, virtual stents were deployed and blood flow simulations were carried out using the respective patient-specific geometries. Afterward, hemodynamic metrics such as aneurysmal inflow reduction, wall shear stresses, oscillatory shear, and inflow concentration indices were quantified. The hemodynamic simulations reveal that for both cases, the neck inflow was clearly reduced due to the therapy (Case 1: 19%, Case 2: 35%). In addition, relevant hemodynamic parameters such as time-averaged wall shear stress (Case 1: 35.6%, Case 2: 57%) and oscillatory shear (Case 1: 33.1%, Case 2: 26.7%) were decreased considerably. However, although stronger relative reductions occurred in the unsuccessful case, the absolute flow values in the successful case were approximately halved. The findings demonstrate that a high relative effect of endovascular devices is not necessarily associated with the desired treatment outcome. Instead, it appears that a successful intracranial aneurysm therapy requires a certain patient-specific inflow threshold.
    Type of Medium: Online Resource
    ISSN: 0391-3988 , 1724-6040
    URL: Article
    DOI: 10.1177/0391398818775521
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2018
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  • 6
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    Torrents of torment: turbulence as a mechanism of pulsatile tinnitus secondary to venous stenosis revealed by high-fidelity computational fluid dynamics
    BMJ ; 2021
    In:  Journal of NeuroInterventional Surgery Vol. 13, No. 8 ( 2021-08), p. 732-737
    Details
    In: Journal of NeuroInterventional Surgery, BMJ, Vol. 13, No. 8 ( 2021-08), p. 732-737
    Abstract: Pulsatile tinnitus (PT) is a debilitating condition that can be caused by a vascular abnormality, such as an arterial or venous lesion. Although treatment of PT-related venous lesions has been shown to successfully cure patients of the associated ‘tormenting’ rhythmical sound, much controversy still exists regarding their role in the etiology of PT. Methods A patient presented with a history of worsening, unilateral PT. A partial venous sinus obstruction related to the large arachnoid granulation was detected on the right side, and subsequently stented at the right transverse sinus. High-fidelity computational fluid dynamics (CFD) was performed on a 3D model digitally segmented from the pre-stent venogram, with assumed pulsatile flow rates. A post-stent CFD model was also constructed from this. Data-driven sonification was performed on the CFD velocity data, blinded to the patient’s self-reported sounds. Results The patient reported that the PT was completely resolved after stenting, and has had no recurrence of the symptoms after more than 2 years. CFD simulation revealed highly disturbed, turbulent-like flow at the sigmoid sinus close to auditory structures, producing a sonified audio signal that reproduced the subjective sonance of the patient’s PT. No turbulence or sounds were evident at the stenosis, or anywhere in the post-stent model. Conclusions For the first time, turbulence generated distal to a venous stenosis is shown to be a cause of PT. High-fidelity CFD may be useful for identifying patients with such ‘torrents’ of flow, to help guide treatment decision-making.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    URL: Article
    DOI: 10.1136/neurintsurg-2020-016636
    Language: English
    Publisher: BMJ
    Publication Date: 2021
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  • 7
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    Biomodex patient-specific brain aneurysm models: the value of simulation for first in-human experiences using new devices and robotics
    BMJ ; 2021
    In:  Journal of NeuroInterventional Surgery Vol. 13, No. 3 ( 2021-03), p. 272-277
    Details
    In: Journal of NeuroInterventional Surgery, BMJ, Vol. 13, No. 3 ( 2021-03), p. 272-277
    Abstract: With the recent advent of advanced technologies in the field, treatment of neurovascular diseases using endovascular techniques is rapidly evolving. Here we describe our experience with pre-surgical simulation using the Biomodex EVIAS patient-specific 3D-printed models to plan aneurysm treatment using endovascular robotics and novel flow diverter devices. Methods Pre-procedural rehearsals with 3D-printed patient-specific models of eight cases harboring brain aneurysms were performed before the first in-human experiences. To assess the reliability of the experimental model, the characteristics of the aneurysms were compared between the patient and 3D models. The rehearsals were used to define the patient treatment plan, including technique, device sizing, and operative working projections. Results The study included eight patients with their respective EVIAS 3D aneurysm models. Pre-operative simulation was performed for the first in-human robotic-assisted neurovascular interventions (n=2) and new generation flow-diverter stents (n=6). Aneurysms were located in both the anterior (n=5) and posterior (n=3) circulation and were on average 11.0±6.5 mm in size. We found reliable reproduction of the aneurysm features and similar dimensions of the parent vessel anatomy between the 3D models and patient anatomy. Information learned from pre-surgical in vitro simulation are described in detail, including an improved patient treatment plan, which contributed to successful first in-world procedures with no intraprocedural complications. Conclusions Pre-procedural rehearsal using patient-specific 3D models provides precise procedure planning, which can potentially lead to greater operator confidence, decreased radiation dose and improvements in patient safety, particularly in first in-human experiences.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    URL: Article
    DOI: 10.1136/neurintsurg-2020-015990
    Language: English
    Publisher: BMJ
    Publication Date: 2021
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  • 8
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    Motion artifact correction for cone beam CT stroke imaging: a prospective series
    BMJ ; 2022
    In:  Journal of NeuroInterventional Surgery
    Details
    In: Journal of NeuroInterventional Surgery, BMJ
    Abstract: Imaging assessment for acute ischemic stroke (AIS) patients in the angiosuite using cone beam CT (CBCT) has created increased interest since endovascular treatment became the first line therapy for proximal vessel occlusions. One of the main challenges of CBCT imaging in AIS patients is degraded image quality due to motion artifacts. This study aims to evaluate the prevalence of motion artifacts in CBCT stroke imaging and the effectiveness of a novel motion artifact correction algorithm for image quality improvement. Methods Patients presenting with acute stroke symptoms and considered for endovascular treatment were included in the study. CBCT scans were performed using the angiosuite X-ray system. All CBCT scans were post-processed using a motion artifact correction algorithm. Motion artifacts were scored before and after processing using a 4-point scale. Results We prospectively included 310 CBCT scans from acute stroke patients. 51% (n=159/310) of scans had motion artifacts, with 24% being moderate to severe. The post-processing algorithm improved motion artifacts in 91% of scans with motion (n=144/159), restoring clinical diagnostic capability in 34%. Overall, 76% of the scans were sufficient for clinical decision-making before correction, which improved to 93% (n=289/310) after post-processing with our algorithm. Conclusions Our results demonstrate that CBCT motion artifacts are significantly reduced using a novel post-processing algorithm, which improved brain CBCT image quality and diagnostic assessment for stroke. This is an important step on the road towards a direct-to-angio approach for endovascular thrombectomy (EVT) treatment.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    URL: Article
    DOI: 10.1136/jnis-2021-018201
    Language: English
    Publisher: BMJ
    Publication Date: 2022
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  • 9
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    The impact of postoperative aspirin in patients undergoing Woven EndoBridge: a multicenter, institutional, propensity score-matched analysis
    BMJ ; 2024
    In:  Journal of NeuroInterventional Surgery
    Details
    In: Journal of NeuroInterventional Surgery, BMJ
    Abstract: The Woven EndoBridge (WEB) device is frequently used for the treatment of intracranial aneurysms. Postoperative management, including the use of aspirin, varies among clinicians and institutions, but its impact on the outcomes of the WEB has not been thoroughly investigated. Methods This was a retrospective, multicenter study involving 30 academic institutions in North America, South America, and Europe. Data from 1492 patients treated with the WEB device were included. Patients were categorized into two groups based on their postoperative use of aspirin (aspirin group: n=1124, non-aspirin group: n=368). Data points included patient demographics, aneurysm characteristics, procedural details, complications, and angiographic and functional outcomes. Propensity score matching (PSM) was applied to balance variables between the two groups. Results Prior to PSM, the aspirin group exhibited significantly higher rates of modified Rankin scale (mRS) mRS 0–1 and mRS 0–2 (89.8% vs 73.4% and 94.1% vs 79.8%, p 〈 0.001), lower rates of mortality (1.6% vs 8.6%, p 〈 0.001), and higher major compaction rates (13.4% vs 7%, p 〈 0.001). Post-PSM, the aspirin group showed significantly higher rates of retreatment (p=0.026) and major compaction (p=0.037) while maintaining its higher rates of good functional outcomes and lower mortality rates. In the multivariable regression, aspirin was associated with higher rates of mRS 0–1 (OR 2.166; 95% CI 1.16 to 4, p=0.016) and mRS 0–2 (OR 2.817; 95% CI 1.36 to 5.88, p=0.005) and lower rates of mortality (OR 0.228; 95% CI 0.06 to 0.83, p=0.025). However, it was associated with higher rates of retreatment (OR 2.471; 95% CI 1.11 to 5.51, p=0.027). Conclusions Aspirin use post-WEB treatment may lead to better functional outcomes and lower mortality but with higher retreatment rates. These insights are crucial for postoperative management after WEB procedures, but further studies are necessary for validation.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    URL: Article
    DOI: 10.1136/jnis-2023-021082
    Language: English
    Publisher: BMJ
    Publication Date: 2024
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  • 10
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    Towards the Clinical utility of CFD for assessment of intracranial aneurysm rupture – a systematic review and novel parameter-ranking tool
    BMJ ; 2019
    In:  Journal of NeuroInterventional Surgery Vol. 11, No. 2 ( 2019-02), p. 153-158
    Details
    In: Journal of NeuroInterventional Surgery, BMJ, Vol. 11, No. 2 ( 2019-02), p. 153-158
    Abstract: Intracranial aneurysms (IAs) are vascular dilations on cerebral vessels that affect between 1%–5% of the general population, and can cause life-threatening intracranial hemorrhage when ruptured. Computational fluid dynamics (CFD) has emerged as a promising tool to study IAs in recent years, particularly for rupture risk assessment. However, despite dozens of studies, CFD is still far from clinical use due to large variations and frequent contradictions in hemodynamic results between studies. Purpose To identify key gaps in the field of CFD for the study of IA rupture, and to devise a novel tool to rank parameters based on potential clinical utility. Methods A Pubmed search identified 231 CFD studies for IAs. Forty-six studies fit our inclusion criteria, with a total of 2791 aneurysms. For included studies, study type, boundary conditions, solver resolutions, parameter definitions, geometric and hemodynamic parameters used, and results found were recorded. Data synthesis Aspect ratio, aneurysm size, low wall shear stress area, average wall shear stress, and size ratio were the parameters that correlate most strongly with IA rupture. Limitations Significant differences in parameter definitions, solver spatial and temporal resolutions, number of cycles between studies as well as frequently missing information such as inlet flow rates were identified. A greater emphasis on prospective studies is also needed. Conclusions Our recommendations will help increase standardization and bridge the gaps in the CFD community, and expedite the process of making CFD clinically useful in guiding the treatment of IAs.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    URL: Article
    URL: Article
    DOI: 10.1136/neurintsurg-2018-014246
    DOI: 10.1136/neurintsurg-2018-014246.supp1
    Language: English
    Publisher: BMJ
    Publication Date: 2019
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