[Show abstract][Hide abstract] ABSTRACT: Delayed rupture of a previously unruptured cerebral aneurysm after uneventful saccular coil packing is rare, particularly when the quality of aneurysm occlusion is appropriate (neck remnant or total occlusion). The present report describes the case of a 70-year-old woman with an incidentally detected, asymptomatic, small basilar tip non-thrombosed aneurysm who experienced rupture of the aneurysm 2years after coiling. Cerebral angiography taken on the day of rupture revealed only small recanalization of the aneurysm neck with no dome-filling. This is the first report of delayed rupture due to minor recurrence of a previously unruptured small asymptomatic cerebral aneurysm after saccular coil packing. A literature review of 26 reports of late bleeding after coil embolization of previously unruptured cerebral aneurysms showed that dome-filling after coil embolization, symptomatic aneurysms and large/giant aneurysms all increase the risk of delayed rupture in previously unruptured aneurysms after saccular coil packing.
Full-text · Article · Feb 2013 · Journal of Neuroradiology
[Show abstract][Hide abstract] ABSTRACT: This paper presents a new in-vitro simulator that can simulate the new technology of three-dimensional digital subtraction angiography (DSA) to perform a cerebral aneurysm surgery. Then, propose a new technique for the numerical evaluation of the surgical tools applied within this interventional surgery to aid in the design and selection of surgical instruments. Initially, the in-vitro intravascular simulator was constructed, followed by cerebral aneurysm models that were fabricated with highly sensitive photoelastic materials of epoxy resin. Then reconstruct virtual reality modeling of the blood vessel and catheter to record the position information and realize virtual guidance for training. Meanwhile, conduct image processing of photoelastic effects for numerical evaluations of surgical instruments such as catheter insertion and stent expansion. During the stent expansion experiment, the average stress in the selected region of interest caused by the expansion was calculated and compared with the corresponding value obtained before the expansion. The presented simulator and measurement technique can assist in improving a surgeons skills, quantifying the performance of medical mechanisms, and contribute to 3D analysis of stress distribution. This approach can also provide feedback control for robot assisted endovascular systems.
[Show abstract][Hide abstract] ABSTRACT: In the domain of endovascular neurosurgery, the measurement of tissue integrity is needed for simulator-based training and for the development of new intravascular instruments and treatment techniques. In vitro evaluation of tissue manipulation can be achieved using photoelastic stress analysis and vasculature modeling with photoelastic materials. In this research we constructed two types of vasculature models of saccular aneurysms for differentiation of embolization techniques according to the respect for tissue integrity measurements based on the stress within the blood vessel model wall. In an aneurysm model with 5 mm dome diameter, embolization using MicroPlex 10 (Complex 1D, with 4 mm diameter loops), a maximum area of 3.97 mm(2) with stress above 1 kPa was measured. This area increased to 5.50 mm(2) when the dome was touched deliberately with the release mechanism of the coil, and to 4.87 mm(2) for an embolization using Micrusphere, (Spherical 18 Platinum Coil). In a similar way trans-cell stent-assisted coil embolization was also compared to human blood pressure simulation using a model of a wide-necked saccular aneurysm with 7 mm diameter. The area with stress above 1kPa was below 1 mm(2) for the pressure simulation and maximized at 3.79 mm(2) during the trans-cell insertion of the micro-catheter and at 8.92 mm(2) during the embolization. The presented results show that this measurement system is useful for identifying techniques compromising tissue integrity, comparing and studying coils and embolization techniques for a specific vasculature morphology and comparing their natural stress variations such as that produced by blood pressure.
No preview · Article · Dec 2012 · Interventional Neuroradiology
[Show abstract][Hide abstract] ABSTRACT: Quantification of human skills is a challenge for simulator based medical training, particularly for endovascular intervention. For that purpose it is needed to measure different biometric parameters from the user and additionally measure the interaction between endovascular instruments and vasculature models membrane. For that purpose in this research we present an optical sensor for encoding linear and rotational motion of the catheter through the insertion port. Additionally we present two studies for measuring tissue integrity, time to complete a task, reaction time, and wasting motion using two populations of expert and beginner. The optical encoder showed an average error of 0.39mm and 10.78deg. In both studies the presented cyber-physical system is useful to identify the users with qualities closer to the expert among users with low performance.
[Show abstract][Hide abstract] ABSTRACT: Magnetic field has been used for manipulation of micro-robots; in this research we use it for scaffold fabrication. Magnetic sugar particle (MSP) was used as porogen to control pore size, pore structure and pore density in the scaffold. We studied the influence of the strength of magnetic fields for controlling the coating thickness of unmagnetized MSPs during the fabrication of sheet-like scaffolds. The experimental relationship between magnetic flux density and the thickness of MSP layer was illustrated. Furthermore we investigated the infiltration capacity of poly(L-lactide-co-ε-caprolactone) (PLCL) which was used as scaffold material on the MSP clusters. 5% and 10% PLCL solutions were employed in the experiments. After polymer casting and removal of the sugar template, spherical pores were generated inside scaffold, the thickness evaluation of a single layer scaffold was carried out and the cytocompatibility experiment of NdFeB powder used in fabrication of MSP was confirmed with human umbilical vein endothelial cells.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: Recently, the superiority of minimally invasive treatment in endovascular surgery has been advocated. Therefore, VR simulator and silicone blood vessel model simulator have been developed, and practice environment of minimally invasive therapy gets better. However, catheter motion measurement hasn't been done during the simulations, and we couldn't know the expert's strategy and skills of inserting the catheter to the objective nidus. So, there are some difficulties for the beginner to learn the skills of inserting the catheter. For solving this problem, in this research, we proposed the reference area of catheter insertion based on the result of catheter movement inserting in a carotid artery silicone blood vessel model. Reference area of catheter insertion means the insertion success condition obtained from the measurement data of catheter movement, consists of linear and rotational movement. The measurement of catheter insertion was done, and the result show that reference area of catheter insertion of carotid artery silicone blood vessel model is the condition of 70~115deg, 70~80mm. By using this reference area of catheter insertion, beginner of catheter manipulation can insert the catheter to the objective point easily.
[Show abstract][Hide abstract] ABSTRACT: We describe a patient with subcutaneous hematoma associated with manual cervical massage during carotid artery stenting.A 73-year-old man with left cervical carotid artery stenosis presented with left amaurosis fugax. We performed carotid artery stenting using distal embolic protection with balloon occlusion. Dual antiplatelet therapy was maintained in the periprocedural period and an anticoagulant agent was administered during the procedure. Because the aspiration catheter became entrapped by the stent, it did not reach the distal side of the stenotic lesion, and manual compression of the cervical region was therefore performed. Immediately afterwards, a subcutaneous hemorrhage occurred in the cervical region. There was no postoperative dyspnea due to enlargement of the hematoma, which was absorbed spontaneously.Cervical subcutaneous hematoma can occur in the cervical region due to cervical massage in patients who are receiving adjuvant antiplatelet therapy and anticoagulation therapy.
[Show abstract][Hide abstract] ABSTRACT: The photoelastic effect is used for stress measurement during endovascular surgery simulation for quantitative evaluation of catheter trajectory in in vitro environments. By extending the capabilities of this sensing technology, its potential for intravascular tools evaluation will increase.
In this research the error introduced by stress direction on magnitude measurements was studied, then stress measurements were made in the phantom modelling of a saccular aneurysm with bleb. To visualize three-dimensionally the stress field changes produced by a guide wire in a phantom wall, a scanner and an algorithm relying on maximum likelihood-expectation maximization are proposed. Three-dimensional fields at different pressure level were compared with the stress field surrounding the guide wire.
The maximum error in stress magnitude measurements due to stress direction was 2.52%. Stress local maximum was detected in the bleb phantom before rupture. Three-dimensional visualization was obtained in vasculature phantom with average errors of 10.73%, 4.55%, 3.18% for inner pressures of 80, 120, 160 mmHg, respectively. Stress measurement in the neighbourhood of the guide wire is equivalent to applying an inner pressure of 120 mmHg.
For the presented polariscope, the weak influence of stress direction in magnitude measurements was confirmed. In vasculature phantoms, the three-dimensional visualization of stress eliminated birefringence visualization distortion and enabled more comprehensive comparison of stress produced by intravascular tools with stress produced by normal blood pressure.
No preview · Article · Mar 2011 · International Journal of Medical Robotics and Computer Assisted Surgery
[Show abstract][Hide abstract] ABSTRACT: Recent advances to develop scaffolds with controlled pore layout and porosity have great significance in tissue engineering for providing optimal cultivation conditions. Porogen leaching has been commonly used to control pore size, pore structure and porosity in the scaffold fabrication. This paper reports a magnetic steering method for controlling magnetic sugar particles as porogens in fabrication of sheet-like scaffold. A patterning device is utilized to align particles on desired positions and magnetic PVA is introduced to improve the layout of pores. After Poly(L-lactide-co-ε-caprolactone) (PLCL) casting and removal of the sugar template, spherical pores are generated inside scaffold. The surface and inner morphologies of the scaffolds are evaluated with the aid of optical microscope and scanning electron microscope, respectively. The results show controllable diameters with ranges of 150μm to 200μm and appropriate interconnection of pores, elegant pore wall morphology and high porosity are achieved in small-size scaffolds with the size of 8mm in width and 10mm in length.
[Show abstract][Hide abstract] ABSTRACT: Vascular disease is a major cause of death, therefore it is desirable to develop robots and simulation tools for catheter trajectory evaluation. Until now trajectory completion duration, catheter tip location, wall deformation, morphology and stress applied to blood vessel phantom wall were identified as evaluation parameters during endovascular surgery simulation. For that purpose image processing and photoelastic stress analysis were used to measure those parameters from five source trajectories and from them to build a reference trajectory. Then the reference trajectory was used to evaluate five trajectories; were the catheter was driven by different persons or using a catheter insertion robot. The average catheter tip detection success rate of 94.96% and the image processing module speed of 769ms enable to register and evaluate human skills abilities using the proposed reference trajectory construction method. The reference trajectory construction and error calculation could be used to apply feedback control to the catheter insertion robot with those parameters.
[Show abstract][Hide abstract] ABSTRACT: It is desirable for endovascular surgery simulation to describe with quantitative data the interaction between the catheter and the blood vessel model wall to make an objective evaluation of the procedure. Photoelastic stress analysis in straight segments of multi-layered models was used for that purpose. In this research we study the error introduced by stress direction on the magnitude measurements, for photoelastic stress analysis. And we propose a scanner for three dimensional visualization of photoelastic stress analysis. As result, we quantified that the maximum contribution of error from stress direction in the first half of the fringe is 2.52% for the stress magnitude measurements. Three-dimensional stress visualization was obtained in segment of straight vasculature with an average error in sample slices of 10.73%, 4.55% and 3.18% for inner pressures of 80, 120 and 160mmHg respectively.
[Show abstract][Hide abstract] ABSTRACT: Fluid-structure interaction analysis in Internal Carotid Artery(ICA) are carried out as preparation for validation between the result of numerical simulation and photoelastic stress analysis. In this work, we assume blood vessel as an isotropic elastic medium and the wall's Poisson ratio is 0.45 and Young's modulus is 3.0Mpa. Our study shows various parameter on fluid dynamics of blood flow, such as the velocity profile, wall shear stress distribution, displacement of vessel wall and Mises stress. Blood flow after bifurcation generate vortex flow and decreases flow speed and wall shear stress nearly to 0Pa. This low wall shear stress can accelerate the accumulation of plaque and eventually causes vessel narrowing. Moreover, the maximum wall shear stress and Mises stress is focused on the bifurcation of ICA. These high stress may lead to aneurysm initiation.
[Show abstract][Hide abstract] ABSTRACT: The development of a numerical criterion to evaluate the stress on models of vasculature has applications in evaluation of human skills, robots and medical tools. This criterion will enable better medical training for endovascular surgery and the development of better medical techniques and tools. We propose to use the stress produced by human blood pressure simulation in the wall of the model of vasculature as this criterion; and to measure the principal component of stress magnitude using photoelastic effect. For that we simulated human blood pressure with a 5.6% of average error, we developed a shielded urethane model of vasculature enabling water circulation and avoiding plastic deformation with pressures below 182 mmHg. We developed software to calculate the stress of the model wall. Stress produced by human blood pressure simulation and a guide wire were compared numerically in four ranges.
[Show abstract][Hide abstract] ABSTRACT: We proposed a fabrication method for multiscale transparent arteriole and capillary vessel models and demonstrated the fabrication of microchannels with circular cross sections Â¿10 - 500 Â¿m. First, we demonstrated fabrication of Â¿10 - 500 Â¿m arteriole and capillary vessel block models using photolithography. The circularity of fabricated Â¿10, 50, and 500 Â¿m microchannels were 84.0%, 61.5%, and 82.3%, respectively. Flow experiments demonstrated that these channels had no leakage. Next, we proposed a fabrication method for Â¿100 - 500 Â¿m arteriole membrane models, which connect larger membrane models and smaller block models. These models were prepared with grayscale lithography and a wax and PVA (polyvinyl alcohol) mixture material. The proposed approach overcame the brittleness of a previous sacrificial model fabricated by ink jet rapid prototyping. The membrane model had a circular cross section with a channel circularity of 90%. Finally, we succeeded in making transparent membranous and block arteriole model with which we can simulate blood circulation.
[Show abstract][Hide abstract] ABSTRACT: Technologies to develop scaffolds with controlled diameter and high porosity have great significance in tissue engineering. We have fabricated biodegradable 2D and 3D scaffolds with ordered array of pores by casting polymer on self-assembled d-fructose (sugar) microspheres. First, ferrite microparticles were encapsulated in sugar spheres to make them become magnetized. After sieving magnetic sugar particles, those diameter-controlled particles were attracted by a magnet to form a self-assembled template for polymer casting. After removal of sugar particles, ordered array of pores were generated on the surface of sheet-like scaffolds. Ordered pores are also generated in 3D tubular scaffolds by using magnetic force and viscoelasticity of PVA solution. It was confirmed that MSPs leaching method makes it possible to make high porous scaffolds in spite of the thickness of scaffold and the porosity is homogeneous. Finally, the biocompatibility of the developed scaffold was confirmed by the viability of human umbilical vein endothelial cells.
[Show abstract][Hide abstract] ABSTRACT: Surgical simulators are used in practice and rehearsal for intravascular neurosurgery and for development of new medical instruments . However circulation type blood vessel models with multiscale network channels have not been realized. We have developed three-dimensional elastic membranous blood vessel models by using ink-jet rapid prototyping. The diameter of the blood vessels is larger than 500 μm. Then, we have developed φ10 - 500 μm arteriole and capillary vessel models with circular cross-section by photolithography. The circularity of fabricated φ10, 50, 500 μm microchannels is 84.0%, 61.5%, 82.3% respectively . We connected these different models to realize circulation type blood vessel models simulating arteriole network. We proposed two connecting methods, and succeeded in making circulation type models by both methods.