Keiko Irie

Fujita Health University, Nagoya, Aichi, Japan

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Publications (62)53 Total impact

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    ABSTRACT: This paper presents a novel hybrid medical stent device. This hybrid stent device formed by fractal mesh structures provides a flow-diverting effect and stent-assisted coil embolization. Flow-diverter stents decrease blood flow into an aneurysm to prevent its rupture. In general, the mesh size of a flow-diverter stent needs to be small enough to prevent blood flow into the aneurysm. Conventional flow-diverter stents are not available for stent-assisted coil embolization, which is an effective method for aneurysm occlusion, because the mesh size is too small to insert a micro-catheter for coil embolization. The proposed hybrid stent device is capable of stent-assisted coil embolization while simultaneously providing a flow-diverting effect. The fractal stent device is composed of mesh structures with fine and rough mesh areas. The rough mesh area can be used to insert a micro-catheter for stent-assisted coil embolization. Flow-diverting effects of two fractal stent designs were composed to three commercially available stent designs. Flow-diverting effects were analyzed using computational fluid dynamics (CFD) analysis and particle image velocimetry (PIV) experiment. Based on the CFD and PIV results, the fractal stent devices reduce the flow velocity inside an aneurism just as much as the commercially available flow-diverting stents while allowing stent-assisted coil embolization.
    No preview · Article · Oct 2015 · Medical & Biological Engineering
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    ABSTRACT: The development of new diagnostic technologies for cerebrovascular diseases requires an understanding of the mechanism behind the growth and rupture of cerebral aneurysms. To provide a comprehensive diagnosis and prognosis of this disease, it is desirable to evaluate wall shear stress, pressure, deformation and strain in the aneurysm region, based on information provided by medical imaging technologies. In this research, we propose a new cyber-physical system composed of in vitro dynamic strain experimental measurements and computational fluid dynamics (CFD) simulation for the diagnosis of cerebral aneurysms. A CFD simulation and a scaled-up membranous silicone model of a cerebral aneurysm were completed, based on patient-specific data recorded in August 2008. In vitro blood flow simulation was realized with the use of a specialized pump. A vision system was also developed to measure the strain at different regions on the model by way of pulsating blood flow circulating inside the model. Experimental results show that distance and area strain maxima were larger near the aneurysm neck (0.042 and 0.052), followed by the aneurysm dome (0.023 and 0.04) and finally the main blood vessel section (0.01 and 0.014). These results were complemented by a CFD simulation for the addition of wall shear stress, oscillatory shear index and aneurysm formation index. Diagnosis results using imaging obtained in August 2008 are consistent with the monitored aneurysm growth in 2011. The presented study demonstrates a new experimental platform for measuring dynamic strain within cerebral aneurysms. This platform is also complemented by a CFD simulation for advanced diagnosis and prediction of the growth tendency of an aneurysm in endovascular surgery. Copyright
    No preview · Article · Jun 2013 · International Journal of Medical Robotics and Computer Assisted Surgery
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    ABSTRACT: Computer-based simulation is necessary to clarify the hemodynamics in brain aneurysm. Specifically for endovascular treatments, the effects of indwelling intravascular devices on blood stream need to be considered. The most recent technology used for cerebral aneurysm treatment is related to the use of flow diverters to reduce the amount of flow entering the aneurysm. To verify the differences of flow reduction, we analyzed multiple Enterprise stents and two kinds of flow diverters. In this research, we virtually modeled three kinds of commercial intracranial stents (Enterprise, Silk, and Pipeline) and mounted to fit into the vessel wall, and deployed across the neck of an IC-ophthalmic artery aneurysm. Also, we compared the differences among multiple Enterprise stents and two flow diverters in a standalone mode. From the numerical results, the values of wall shear stress and pressure are reduced in proportion to the size of mesh, especially in the inflow area. However, the reduced velocity within the aneurysm sac by the multiple stents is not as significant as the flow diverters. This is the first study analyzing the flow alterations among multiple Enterprise stents and flow diverters. The placement of small meshed stents dramatically reduced the aneurysmal fluid movement. However, compared to the flow diverters, we did not observe the reduction of flow velocity within the aneurysm by the multiple stents.
    No preview · Article · Oct 2012
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    ABSTRACT: Hemodynamic factors are thought to play important role in the initiation, growth, and rupture of cerebral aneurysms. However, hemodynamic features in the residual neck of incompletely occluded aneurysms and their influences on recanalization are rarely reported. This study characterized the hemodynamics of incompletely occluded aneurysms that had been confirmed to undergo recanalization during long-term follow-up using computational fluid dynamic analysis. A ruptured left basilar-SCA aneurysm was incompletely occluded and showed recanalization during 11 years follow-up period. We retrospectively characterized on three-dimensional MR angiography. After subtotal occlusion, the flow pattern, wall shear stress (WSS), and velocity at the remnant neck changed during long-term follow-up period. Specifically, high WSS region and high blood flow velocity were found near the neck. Interestingly, these area of the remnant neck coincided with the location of aneurysm recanalization. High WSS and blood flow velocity were consistently observed near the remnant neck of incompletely occluded aneurysm, prone to future recanalization. It will suggest that hemodynamic factors may play important roles in aneurismal recurrence after endovascular treatment.
    No preview · Article · Jul 2012
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    ABSTRACT: Computer based simulation is important for clarifying the hemodynamics in brain aneurysm. Specifically, for endovascular treatments, the effect of indwelling intravascular devices on blood stream needs to be considered. Some medical studies have reported many kinds of stents configuration in artery aneurysm. However, it is still unclear which configuration of stents is optimal for surgery. To verify the efficiency of flow reduction effect between different pattern of stents configuration, we placed stents virtually in brain aneurysm and analyzed fluid dynamics. In this study, we present the process of constructing 3D flow diverter stent from helix curve and a method for fitting them to patient specific vasculature wall. Aneurysmal fluid dynamics for three different configurations (half-Y, Y and cross-bar) by computational fluid dynamics (CFD) are carried in two kinds of commercially available stents in patient specific vessel model.
    No preview · Conference Paper · Apr 2012

  • No preview · Article · Jan 2012
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    ABSTRACT: For the development of artificial intelligent diagnosis for cerebrovascular intervention, it is desirable to forecast the growth of cerebral aneurysms. In order to achieve such purpose, it is needed to evaluate wall shear stress, strain, pressure, deformation and flow velocity in the aneurysm region. In this research, we focus on in-vitro strain and deformation measurements of cerebral aneurysm models, and propose a cyber-physical system, in which a scaled-up membranous silicone model of cerebral aneurysm was built and integrated with a specialized pump for the pulsatile blood flow simulation, and a vision system was constructed to measure the strain on different regions on the model with pulsatile blood flow circulated inside. Experimental results show that both distance and area strain maxima were larger for the aneurysm neck (0.042 and 0.052), followed by the aneurysm dome (0.023 and 0.04) and then by the main blood vessel section (0.01 and 0.014), which were complemented with computer fluid dynamics simulation for the inclusion of wall shear stress, oscillatory shear index and aneurysm formation index. Medical imaging data of the cerebral aneurysm in 2008 and 2011 was obtained. Diagnosis results have concordance with the aneurysm growth in 2011. The presented measurement method offers an option for measuring strain and deformation to be complementary with computer fluid dynamics and photoelastic stress analysis for advanced diagnostic in the endovascular surgery.
    No preview · Conference Paper · Jan 2012
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    ABSTRACT: Computer based simulation is important for clarifying the hemodynamics in brain aneurysm. Specifically, for endovascular treatments, the effect of indwelling intravascular devices on blood stream needs to be considered. Most recent technology for cerebral aneurysm treatment is related with the use of flow diverters to reduce the amount of flow entering to the aneurysms. In this research, we present a new method for design of flow diverters and fitting them to patient specific vasculature models. This methodology enables to change porosity of the flow diverters as well as their location in the blood vessel. One coiling assist stent and two flow diverters were compared to estimate the effect of flow alteration in aneurysm for treatment of a cerebral aneurysm. From the numerical result, we can conclude that pore density and size of mesh affect the hemodynamics in aneurysm and high density and small size of pore produce reduction effect of pressure and wall shear stress on an aneurysm.
    No preview · Conference Paper · Jan 2012
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    ABSTRACT: Carotid cavernous fistula (CCF) is an abnormal arteriovenous communication in the cavernous sinus. Direct CCF results from a tear in the intracavernous carotid artery. Typically, it has a high flow and usually presents with oculo-orbital venous congestive features such as exophthalmos, chemosis, and sometimes oculomotor or abducens cranial nerve palsy. Indirect CCF generally occurs spontaneously with subtle signs. We report a rare case of spontaneous direct CCF in childhood who did not have the usual history of craniofacial trauma or connective tissue disorder but presented with progressive chemosis and exophthalmos of the right eye. This report aims also to describe the safety and success of transvenous embolization with coils of the superior ophthalmic vein and cavernous sinus through the inferior petrosal sinus.
    No preview · Article · Apr 2011

  • No preview · Article · Oct 2009

  • No preview · Article · Jan 2009
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    ABSTRACT: Giant aneurysms have a dismal natural history, thus necessitating early management. These pose a great challenge to the vascular neurosurgeon. The complexity of their anatomy, parent vessels or branches and perforators warrants additional measures for maintaining distal perfusion. Here we try to define the minimally invasive management of these aneurysms. This study compares reconstruction and bypass. This study covers 40 large and 5 giant cases of aneurysms treated in our institute. Giant aneurysms are those with a dome diameter 25 mm or more. 3D CT scan and DSA were the primary investigative procedures, and 3D CT scan was especially useful in thrombosed aneurysms. Aneurysms that had involved a major portion of the parent wall were reconstructed, thus avoiding bypass. Based on our experience, not only basic technique of trapping and evacuation and clipping of the aneurysm neck but also reconstruction of the artery bearing the aneurysm is vital for good postoperative results. Different clipping methods are also used to reconstruct the parent artery. Bypass techniques are also gaining importance in the management of giant aneurysms in difficult cases. However, we feel that bypass procedures are too extensive and are associated with attendant complications. Acute graft occlusion is one of the commonest complications. Aneurysmal rupture is one more complication of bypass procedures. Prolonged occlusion can also cause neurological deficits. Considering the difficulties with bypass and our experience in parent vessel reconstruction with multiple clipping, we feel bypass should be considered only in exceptional cases.
    No preview · Article · Jan 2009 · Surgery for Cerebral Stroke
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    ABSTRACT: Our objective was to set up a management-oriented classification for paraclinoid aneurysms, and then design and apply a simplified management scheme according to each group defined by this classification. Paraclinoid aneurysms were classified as group I (supraophthalmic artery), group II (ophthalmic artery) and group III (infraophthalmic artery) aneurysms intradurally. Between January 2005 and December 2006, 86 cases with 89 paraclinoid aneurysms were treated. There were 35 (40.2%) aneurysms in group I (20 in group Ia, 15 in group Ib), 32 (36.8%) in group II and 20 (23%) in group III. In group I aneurysms, 20 (57.1%) were treated by clipping or/and wrapping, while 15 (42.9%) were managed by coiling. In group II aneurysms, 20 (62.5%) were treated by clipping and 12 (37.5%) by coiling. The contralateral approach was performed for 4 (6%) aneurysms in groups I and II. All 20 group III aneurysms were treated by coiling. The overall rate of permanent complications was 4.6%. The rate of complete occlusion was 92.5% in surgical cases and 55.6% in endovascular ones. The overall outcomes in the treatment of paraclinoid aneurysms were excellent (GOS = 5, 95.4%). Based on our modified classification of paraclinoid aneurysms, a simplified management scheme was designed and applied. For group I (supraophthalmic artery) and group II (ophthalmic artery) aneurysms, surgical clipping or/and wrapping should be the first choice of treatment, while for group III (infraophthalmic artery) aneurysms, endovascular coiling should be the best modality. Additionally, individualizing the treatment planning might contribute to better results.
    No preview · Article · Sep 2008 · Cerebrovascular Diseases
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    ABSTRACT: A 0.010 inch diameter ED coil (Kaneka medics, Kanagawa, Japan) was newly developed and came to market recently. Early experiences using this detachable coil are reported. Fifteen intracranial saccular aneurysms were treated at our institution since Oct. 2006. There are soft and extrasoft type-10 ED coils and the both types were used. Fifty-one coils were deployed for 15 aneurysms. As the coil part and junction with the delivery wire is very soft, type-10 ED coils are easy to advance even in a very tortuous vessels and less likely to unintentionally move a microcatheter due to friction than other available detachable coils. There were no premature detachments, no coils unraveled, and no failures to detach. As for case complications, there was no intraprocedural aneurysmal ruptures and no thromboembolisms. There was one instance of coil migration with the smallest and shortest coil. It resulted in a small asymptomatic infarction. As the coil is itself very soft, smaller ones should be more carefully deployed within the coil basket to avoid coil migration. The device was considered to be effective and safe for endosaccular embolization of cerebral aneurysms.
    No preview · Article · Dec 2007
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    ABSTRACT: Extracranial vertebral artery aneurysm associated with neurofibromatosis (NF1) is very rare. The aneurysm was successfully treated by endovascular trapping of the aneurysm and proximal vertebral artery with coils.
    Full-text · Article · Mar 2007 · Interventional Neuroradiology
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    ABSTRACT: A limited series of patients with aneurysm were reviewed retrospectively to analyze strategies for integrating microsurgical and endovascular techniques in the management of complex, surgically intractable aneurysms. Four patients were managed in Fujita Health University with a multimodality approach: intentional reconstruction of the aneurysm neck followed by endovascular coiling. A total of 5 aneurysms were treated, of which 3 were large or giant in size, and 3 were fusiform or multilobulated. Complete angiographic obliteration was confirmed in 4 aneurysms (80%). All patients had a good outcome (Glasgow Outcome Scale score 5; mean follow-up, 64 months). As for complex, surgically intractable aneurysms, the intentional reconstruction of the aneurysm neck followed by endovascular coiling should be considered more often.
    No preview · Article · Feb 2007 · Cerebrovascular Diseases
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    ABSTRACT: In this paper, we propose an in vitro patient-specific anatomical model of human cerebral artery, a hardware platform for simulating endovascular intervention for making diagnosis and surgical trainings. Proposed vessel model hollowly reproduces 3-dimensional configuration of vascular lumens with elastic membranous configuration as a transparent silicone structure, using fluoroscopic information, which is obtained with CT (Computed Tomography), MRI (Magnetic Resonance Imaging) and other imaging modalities. This vessel model also reproduces the physical characteristics of artery tissue, such as elastic modulus, Poisson's ratio and friction coefficient, within respectively 10% of errors. Consequently, it allows practically simulating procedures, which is accompanied by realistic vascular deformation, realistic feel of operating catheters and realistic behavior of surgical instruments (e.g. slip/stick motion and unwinding motion). Presented vasculature model should provide a helpful platform for interventionalists to make preliminary simulation, for young trainees to practice surgical procedures and for developers to evaluate surgical robots, device and other various medical instruments.
    No preview · Article · Aug 2006
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    ABSTRACT: An in vitro patient-specific vascular model, for simulating endovascular intervention is presented. Proposed vascular model reproduces the 3-dimensional vessel lumen structure using CT/MRI information with 13 mum resolution, and it also reproduce the physical characteristics of arterial tissue (elastic modulus and friction coefficient). Furthermore, in this paper, we propose a novel method to evaluate the stress on vasculature which is applied by surgical operations. This method allows quantitatively evaluating 3-dimensional stress conditions in real-time during surgical simulation. Finally, we constructed a comprehensive surgical simulation system, which reproduces whole human aorta structure (with more than Imm inside diameter), reproduce patient-specific pulsatile blood streaming, allowed to evaluate the stress applied to the aorta structure by surgical operations with almost same manner and environment as the practical endovascular intervention. Consequently proposed model, evaluation method and resultant system provides a very valuable platform for evaluating the performance of surgical robots and instruments developed by developers and researchers, and surgical procedures
    Full-text · Conference Paper · Feb 2006
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    ABSTRACT: An in vitro patient-specific vascular model, for simulating endovascular intervention is presented. Proposed vascular model reproduces the 3-dimensional vessel lumen structure using CT/MRI information with 13 μm resolution, and it also reproduces the physical characteristics of arterial tissue (elastic modulus and friction coefficient). Furthermore, in this paper, we propose a novel method to evaluate the stress on vasculature which is applied by surgical operations. This method allows quantitatively evaluating 3-dimensional stress condition in real-time during surgical simulation. With these techniques, we finally constructed a comprehensive surgical simulation system, which reproduces whole human aorta structure (with more than 1 mm inside diameter), reproduce patient-specific pulsatile blood streaming, allowing interventionalists and developers to evaluate the stress on arterial wall applied by surgical operations with almost the same manner as the practical endovascular intervention. Consequently, the proposed model, stress analysis method and resultant system provides a valuable platform for evaluating the performance of surgical robots and instruments developed by developers and researchers, in addition to surgical procedures.
    No preview · Conference Paper · Dec 2005
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    ABSTRACT: In this paper, we propose an in vitro patient-tailored biological model of human cerebral artery, an innovative platform for simulating intravascular neurosurgery to evaluate medical robots and devices. This anatomically accurate model reproduces 3-dimensional configuration of individual arteries with an artery-like thin membranous structure made of silicone elastomer. Its modeling resolution is 13 μm. Presented modeling methodology also allows constructing any hollow structure, which is suitable for robot evaluations, making use of CAD. Presented model also reproduces the physical properties of arterial tissue with errors less than 5% (that include elastic modulus, poisson's ratio and frictional coefficient). Thus the cerebral arterial model reproduces not only the behavior of arteries caused by surgical operations, but also the dynamic behavior of surgical robots and devices (e.g. elastic deformation and slip/stick motion). Furthermore, we also propose a novel method that allows developers to evaluate 3-dimensional stress condition on arterial wall, which is caused by surgical operations, by making use of the photoelastic effect. As there are almost no realistic hardware platform enough to fairly evaluate medical robots and devices, it should provide an advanced testing environment for developing robots and other various medical equipments, especially for intravascular neurosurgery.
    No preview · Conference Paper · Sep 2005

Publication Stats

460 Citations
53.00 Total Impact Points

Institutions

  • 2003-2013
    • Fujita Health University
      • Department of Neurosurgery
      Nagoya, Aichi, Japan
  • 2005-2006
    • Nagoya University
      • Department of Micro-Nano Systems Engineering
      Nagoya, Aichi, Japan
  • 1998-2003
    • Kagawa University
      • Department of Neurological Surgery
      Takamatu, Kagawa, Japan
  • 1997
    • Kyoto University
      • Department of Neurosurgery
      Kyoto, Kyoto-fu, Japan