Mr. Takuya Natsume Profile

Takuya Natsume

at Tokyo City Univ

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Publications (3)

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Proceedings Article | 26 March 2023 Paper

Micelle behavior analysis using dissipative particle dynamics method

Nobuhiko Mukai, Takuya Natsume, Masamichi Oishi, Marie Oshima

Proceedings Volume 12592, 1259227 (2023) https://doi.org/10.1117/12.2666531

KEYWORDS: Particles, Plasma, Blood, Aneurysms, Blood circulation, Therapeutics, Surgery, Computer simulations, X-ray computed tomography, Visibility

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One of the most dangerous diseases is an aneurysm because if it ruptures the person will die unless urgent and appropriate treatment is performed. There are mainly two types of aneurysms: cerebral aneurysm (CA) and abdominal aortic aneurysm (AAA). CA needs surgical operations that are selected depending on the symptoms, while medical treatments can be applied to a small AAA to prevent it from expanding, although surgeries are operated for a hypertrophied AAA to prevent it from rupturing. The medical treatments employ micelle which is a colloidal sphere-shaped medicine, which size is too small and about 4 [nm]. The micelle is conveyed to AAA and invades from the vascular lumen to the vascular wall, where little blood flow exists and random force such as Brownian movement is dominant. On the slow flow in the small area, a general governing equation called the Navier-Stokes equation is not used and dissipative particle dynamics (DPD) is employed to solve the flow behavior. Then we performed a micelle behavior simulation in the vascular lumen using DPD. As a result, the micelle was not able to move only with random force and moved by some external force.

Proceedings Article | 13 March 2021 Paper

Wettability method based on surface free energy between solid and liquid

Takuya Natsume, Masamichi Oishi, Marie Oshima, Nobuhiko Mukai

Proceedings Volume 11766, 1176613 (2021) https://doi.org/10.1117/12.2590715

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It is one of the important issues to represent wettability that decides a liquid shape on a solid surface. There are some previous methods related to wettability using FEM (Finite Element Method), FVM (Finite Volume Method), and particle method. In these methods, particle method has a merit of robustness for topological change such as a droplet that comes out of a tube and reaches on a surface after being broken by gravity. In particle method, a liquid shape is decided by specifying the contact angle between the liquid and the solid, and by modifying the angle using CSF (Continuum Surface Tension) model or potential model. However, these methods have to specify the contact angle in advance, and the angle is not decided with the physical properties of the liquid and the solid. Therefore, this paper proposes a method to represent wettability not by specifying the contact angle, but by calculating the interfacial tension with the surface free energy between the liquid and the solid. As the result of the simulations with some liquid and solid, we have confirmed that wettability can be represented without specifying the contact angles.

Proceedings Article | 22 March 2019 Paper

Droplet simulation for cerebral aneurysm embolization

Takuya Natsume, Masamichi Oishi, Nobuhiko Mukai, Marie Oshima

Proceedings Volume 11049, 110492R (2019) https://doi.org/10.1117/12.2521428

KEYWORDS: Particles, Liquids, Cerebral aneurysms, Computer simulations, Aneurysms, Surgery, Kinematics, Safety, Computational fluid dynamics, Diffusion

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To prevent subarachnoid hemorrhage that causes serious damage to the brain, clipping and coil embolization are used in Japan, while liquid embolization is also used in overseas. Liquid embolization is an effective technique that can treat with a distorted and enormous cerebral aneurysm. However, it is not authorized yet in Japan because the embolic material flows out of the aneurysm, and embolizes normal blood vessels too. Then, as a preliminary simulation to verify the safety of liquid embolization surgery, we have been developing a particle-based high precision liquid injection simulation with CFD (Computational Fluid Dynamics), and have verified the accuracy by comparison between the simulation results with the corresponding physical experiments. The simulation size, however, was smaller than the physical experiment, since larger size simulation needs huge amount of memory, which cannot be treated with a normal PC. As the result of the simulation, a droplet was formed, but contacted the side surface of the water tank that imitated an aneurysm, and the quantitative assessment could not be performed. Therefore, this paper describes the simulation result with a larger size of environment, and the quantitative assessment by comparison of the aspect ratio of the droplet between the simulation and the physical experiment. In the assessment, we have confirmed that the shape of the droplet formed in the simulation is similar to the one of the physical experiment.

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