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  • 1
    In: Stroke, Ovid Technologies (Wolters Kluwer Health), Vol. 51, No. 2 ( 2020-02), p. 641-643
    Abstract: Therapeutic decision making for small unruptured intracranial aneurysms ( 〈 10 mm) is difficult. We aimed to develop a rupture risk model for small intracranial aneurysms in Japanese adults, including clinical, morphological, and hemodynamic parameters. Methods— We analyzed 338 small unruptured aneurysms; 35 ruptured during the observation period, and 303 remained stable. Clinical, morphological, and hemodynamic parameters were considered. Computational fluid dynamics was used to calculate hemodynamic parameters based on computed tomography images of all aneurysms in their unruptured state. Differences between the ruptured and unruptured groups were tested by the Mann-Whitney U or Fisher exact tests. Multivariate logistic regression was applied to obtain a rupture risk model. Its predictive ability was investigated by receiver operating characteristic analysis. Results— The risk model revealed that rupture may be more likely to in younger patients (odds ratio [OR], 0.92 for each age increase of 1 year [95% CI, 0.88−0.96] P 〈 0.001) with multiple aneurysms (OR, 2.58 [95% CI, 1.07−6.19] P =0.03), located at a bifurcation (OR, 5.45 [95% CI, 1.87−15.85] P =0.002), with a bleb (OR, 4.09 [95% CI, 1.42−11.79] P =0.009), larger length (OR, 1.91 for each increase of 1 mm [95% CI, 1.42−2.57] P 〈 0.001), and lower pressure loss coefficient (OR, 0.33 for each decrease of 1 unit [95% CI, 0.14−0.77] P =0.01). The sensitivity, specificity, and area under the curve were 0.800, 0.752, and 0.826 (95% CI, 0.739−0.914) respectively. Conclusions— Younger age, presence of multiple aneurysms, location at a bifurcation, presence of a bleb, larger length, and lower pressure loss coefficient were identified as risk factors for rupture of small intracranial aneurysms. The risk model should be validated in further studies.
    Type of Medium: Online Resource
    ISSN: 0039-2499 , 1524-4628
    RVK:
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2020
    detail.hit.zdb_id: 1467823-8
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  • 2
    In: Journal of Neuroendovascular Therapy, The Japanese Society for Neuroendovascular Therapy, Vol. 11, No. 4 ( 2017), p. 186-191
    Type of Medium: Online Resource
    ISSN: 1882-4072 , 2186-2494
    Language: English
    Publisher: The Japanese Society for Neuroendovascular Therapy
    Publication Date: 2017
    detail.hit.zdb_id: 3074267-5
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  • 3
    In: Stroke: Vascular and Interventional Neurology, Ovid Technologies (Wolters Kluwer Health), Vol. 1, No. S1 ( 2021-11)
    Abstract: This meeting abstract was removed due to the OA licensing requirements of this journal. The full abstract is listed here : https://www.svin.org/files/SVIN_2021_Abstracts_for_Web.pdf
    Type of Medium: Online Resource
    ISSN: 2694-5746
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2021
    detail.hit.zdb_id: 3144224-9
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  • 4
    In: Stroke: Vascular and Interventional Neurology, Ovid Technologies (Wolters Kluwer Health), Vol. 1, No. S1 ( 2021-11)
    Abstract: This meeting abstract was removed due to the OA licensing requirements of this journal. The full abstract is listed here : https://www.svin.org/files/SVIN_2021_Abstracts_for_Web.pdf
    Type of Medium: Online Resource
    ISSN: 2694-5746
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2021
    detail.hit.zdb_id: 3144224-9
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  • 5
    In: Stroke: Vascular and Interventional Neurology, Ovid Technologies (Wolters Kluwer Health), Vol. 3, No. S1 ( 2023-03)
    Abstract: Although low volume embolization ratio is known as risk factor of aneurysmal recanalization, stable occlusion can be achieved in limited cases. Evaluation of hemodynamic parameters at the neck surface has usually been performed with a flat surface rather than a curved surface following the actual coil shape. In this study, we investigated the effect of the geometry of the neck surface on hemodynamics related to aneurysm recanalization after coil embolization in low volume embolization ratio. Methods We focused on aneurysms of 5–10 mm in size that were conducted coil embolization with 15–20% volume embolization ratio (low‐VER). Aneurysms that were recanalized after coil embolization and conducted additional coil deployment were defined as the recanalized case. We identified 25 aneurysms (7 recanalized and 18 stable). We randomly selected 3 recanalized cases and 6 stable cases. For each case, the three‐dimensional vascular geometry including aneurysm was reconstructed by preoperative angiographic images. To divide the aneurysm from the parent artery, two types of neck surfaces (flat neck surface and curved neck surface) were generated for each case. The embolized coil was modeled in the enclosed area with the neck plane and aneurysmal wall by our original virtual coiling simulation. CFD analyses were conducted with the flat neck surface and the curved neck surface. We estimated 6 morphological parameters and 35 hemodynamic parameters, and the mean values of hemodynamic parameters were compared between the flat neck surface and the curved neck surface. The change rate of each parameter in the curved neck was calculated based on that in the flat neck. Results Since the velocity and pressure were involved in recanalization factors by the previous studies, as illustrative hemodynamic parameters, the mean values and change rate of the spatially averaged velocity normal to the neck surface into the cerebral aneurysm (NVneck) and the pressure difference between the average pressure on the surface of control volume and the maximum pressure at the neck surface (PDneck) were summarized in Table 1. These parameters were higher with the curved neck surface geometry case than with the flat neck surface geometry case. Furthermore, the change rates were higher in the recanalized cases compared to those in the stable cases. Conclusions In the CFD analysis with the curved surface, the averaged inflow velocity and pressure difference at the neck surface were higher than those with the flat surface. In addition, the change rates of hemodynamic parameters in recanalized cases were higher than those of stable cases. Therefore, the hemodynamic parameters are changed depending on the geometry of the neck surface, which may affect the prediction accuracy for recanalization using CFD.
    Type of Medium: Online Resource
    ISSN: 2694-5746
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2023
    detail.hit.zdb_id: 3144224-9
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  • 6
    In: Stroke: Vascular and Interventional Neurology, Ovid Technologies (Wolters Kluwer Health), Vol. 3, No. S1 ( 2023-03)
    Abstract: Hemodynamic, morphological, and clinical factors have been reported to be involved in aneurysm rupture. Hemodynamic factors could be calculated by computational fluid dynamics (CFD) analysis. In addition, machine learning has been used in various medical fields in recent years, and it is expected to be applicable to the prediction of aneurysm rupture. In this study, we built a rupture prediction model for the small aneurysms (3∼10 mm) using Random Forest, which is one of the machine learning algorithms. This model included hemodynamic parameters from CFD simulations, morphological parameters of each aneurysm, and clinical information. The model was applied to the other patient dataset, and we verified the model’s prediction accuracy. Methods In this study, the ruptured case was defined as an aneurysm that ruptured during the follow‐up term. On the other hand, the unruptured case was defined as an aneurysm that remained stable during the follow‐up for more than two years (average follow‐up term is about nine years), and registered in the database of Jikei Hospital between January 1, 2003 and April 30, 2020. Only small aneurysms (3∼10 mm) were considered in the present study. Based on the criteria, we identified 507 aneurysms (ruptured: 41, unruptured: 466), in which CFD analysis has been completed. Among these aneurysms, 405 aneurysms (ruptured: 32, unruptured: 373) were used to build the rupture prediction model as Training data, and 102 aneurysms (ruptured: 9, unruptured: 93) were used to verify the prediction accuracy as Test data. We used 3‐dimensional arterial geometries that were reconstructed from computed tomography angiography images for conducting CFD simulations and morphological measurements. For the ruptured aneurysms, the image acquired before the rupture was used. We obtained 138 hemodynamic parameters, 7 morphological parameters, and 6 clinical information in each case. From the Training data, we proposed the rupture prediction model with these parameters using Random Forest. Then, we introduced the test data into the model, and its sensitivity and specificity were estimated. Results The sensitivity and specificity of this model for the Test data were 88.9% and 83.9%, respectively. In addition, aspect ratio (AR), the maximum height of the cerebral aneurysm (Hmax), and the spatially maximum values of the oscillatory shear index on the aneurysm wall (OSImax) were obtained as the top three of the important features to predict aneurysm rupture. Furthermore, the values of these parameters of ruptured aneurysms are higher than those of unruptured aneurysms. For unruptured and ruptured cases, average AR were 0.770±0.260 [‐] and 1.02±0.382 [‐] , average Hmax were 3.39±1.22 [mm] and 4.96±1.96 [mm] , and average OSImax were 0.399±0.105 [‐] and 0.460±0.0328 [‐] , respectively. These results imply that cerebral aneurysms with high Hmax, high AR, and high OSImax are more likely to rupture. Conclusions Ruptured aneurysms tend to have high AR, high Hmax, and high OSImax. The sensitivity and specificity of our prediction model were 88.9% and 83.9%, respectively. The rupture prediction model obtained from this study may predict the aneurysm rupture in advance.
    Type of Medium: Online Resource
    ISSN: 2694-5746
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2023
    detail.hit.zdb_id: 3144224-9
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  • 7
    In: Technology and Health Care, IOS Press, Vol. 24, No. 5 ( 2016-09-14), p. 673-679
    Type of Medium: Online Resource
    ISSN: 0928-7329 , 1878-7401
    Language: Unknown
    Publisher: IOS Press
    Publication Date: 2016
    detail.hit.zdb_id: 2043772-9
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  • 8
    In: Journal of Neurosurgery, Journal of Neurosurgery Publishing Group (JNSPG), ( 2023-09-01), p. 1-9
    Abstract: Although it has been proposed that aneurysm morphology is different after rupture, detailed research of the morphological changes using 3D imaging acquired before and after rupture has not been conducted because of the difficulty of data collection. Similarly, hemodynamic changes due to morphological alterations after rupture have not been analyzed. The aim of this study was to investigate the changes in morphology and hemodynamics observed after aneurysm rupture. METHODS For 21 cerebral aneurysms (21 patients) that ruptured during observation, 3D geometry of the aneurysms and parent arteries were reconstructed based on the angiographic images before and after their rupture. In addition, using the reconstructed geometry, blood flow was simulated by computational fluid dynamics (CFD) analysis. Morphological and hemodynamic parameters were calculated both before and after rupture, and their changes from before to after were compared. RESULTS In the morphological parameters, statistically significantly higher values were observed after rupture in height (before: 5.5 ± 2.1 mm, after: 6.1 ± 2.0 mm; p 〈 0.0001), aspect ratio (p = 0.002), aneurysm volume (p = 0.04), and undulation index (p = 0.005). In terms of hemodynamic changes, the mean normalized wall shear stress (NWSS) decreased significantly (before: 5.4 × 10 −1 ± 2.9 × 10 −1 , after: 4.4 × 10 −1 ± 2.8 × 10 −1 ; p 〈 0.001) as well as the other NWSS parameters, including maximum and minimum NWSS, which were associated with stagnant flow due to the morphological changes after rupture. CONCLUSIONS Aneurysm morphology was found to change after rupture into an elongated and irregular geometry, accompanied by an increase in aneurysm volume. These morphological changes were also associated with statistically significant hemodynamic alterations that produced low wall sheer stress by stagnant flow. The authors’ results also provide the opportunity to explore and develop a risk evaluation method for aneurysm rupture based on prerupture morphology and hemodynamics by further exploration in this direction.
    Type of Medium: Online Resource
    ISSN: 0022-3085 , 1933-0693
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    RVK:
    Language: Unknown
    Publisher: Journal of Neurosurgery Publishing Group (JNSPG)
    Publication Date: 2023
    detail.hit.zdb_id: 2026156-1
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  • 9
    In: Journal of NeuroInterventional Surgery, BMJ, Vol. 10, No. 8 ( 2018-08), p. 797-801
    Abstract: The purpose of this study was to investigate hemodynamics and coil distribution with changing coil stiffness and length using the finite element method (FEM) and computational fluid dynamics (CFD) analysis. Methods Basic side-wall and bifurcation type aneurysm models were used. Six types of coil models were generated by changing the coil stiffness and length, based on commercially available embolic coils. Coil embolization was simulated using FEM. CFD was performed to characterize the hemodynamics in the aneurysms after embolization. Coil distribution and velocity reduction in the aneurysms were evaluated. Results The median value of radial coil distribution was shifted from the center to the outer side of the aneurysmal dome by changing coil stiffness: harder coils entered the outer side of the aneurysmal dome more easily. Short coils were more distributed at the neck region, since their small size made it easy for them to enter the tighter area. CFD results also indicated that velocity in the aneurysm was effectively reduced when the coils were more distributed at the neck region and the outer side of the aneurysmal dome because of the disturbance in blood inflow. Conclusions It is easier for coils to enter the outer side of the aneurysmal sphere when they are harder. If coils are short, they can enter tighter areas more easily. In addition, high coil density at the outer side of the aneurysmal dome and at the neck region is important to achieve effective velocity reduction.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    Language: English
    Publisher: BMJ
    Publication Date: 2018
    detail.hit.zdb_id: 2506028-4
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  • 10
    In: Journal of NeuroInterventional Surgery, BMJ, Vol. 9, No. 10 ( 2017-10), p. 999-1005
    Abstract: Although flow diversion is a promising procedure for the treatment of aneurysms, complications have been reported and it remains poorly understood. The occurrence of adverse outcomes is known to depend on both the mechanical properties and flow reduction effects of the flow diverter stent. Objective To clarify the possibility of designing a flow diverter stent considering both hemodynamic performance and mechanical properties. Materials and methods Computational fluid dynamics (CFD) simulations were conducted based on an ideal aneurysm model with flow diverters. Structural analyses of two flow diverter models exhibiting similar flow reduction effects were performed, and the radial stiffness and longitudinal flexibility were compared. Results In CFD simulations, two stents–Pore2-d35 (26.77° weave angle when fully expanded, 35 μm wire thickness) and Pore3-d50 (36.65°, 50 μm respectively)–demonstrated similar flow reduction rates (68.5% spatial-averaged velocity reduction rate, 85.0% area-averaged wall shear stress reduction rate for Pore2-d35, and 68.6%, 85.4%, respectively, for Pore3-d50). However, Pore3-d50 exhibited greater radial stiffness than Pore2-d35 (40.0 vs 21.0 mN/m at a 3.5 mm outer diameter) and less longitudinal flexibility (0.903 vs 0.104 N·mm bending moments at 90°). These measurements indicate that changing the wire thickness and weave angle allows adjustment of the mechanical properties while maintaining the same degree of flow reduction effects. Conclusions The combination of CFD and structural analysis can provide promising solutions for an optimized stent. Stents exhibiting different mechanical properties but the same flow reduction effects could be designed by varying both the weave angle and wire thickness.
    Type of Medium: Online Resource
    ISSN: 1759-8478 , 1759-8486
    Language: English
    Publisher: BMJ
    Publication Date: 2017
    detail.hit.zdb_id: 2506028-4
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