Sema Ghislain, Zamani Shaun, Touris Thanasis, Norpetlian Frederique, Whitney Lauren, Zhao Annie, Zhou Celina, Konangi Santosh, Sami Muhammad
Medtronic Brain Therapies, Irvine CA 92617, USA.
Medtronic Brain Therapies, Irvine CA 92617, USA.
Med Eng Phys. 2025 Oct;144:104394. doi: 10.1016/j.medengphy.2025.104394. Epub 2025 Jul 10.
Benchtop and animal models have traditionally been used to study the propagation of Onyx Liquid Embolic Systems (Onyx) used in the treatment of brain arteriovenous malformations (AVM). However, such models are costly, do not provide sufficient detail to elucidate how variations in Onyx viscosity alter flow dynamics, and rely on some trial-and-error, resulting in elongated timelines for product development.
The goal of this study was to leverage Computational Fluid Dynamics (CFD) simulations to predict the behavior of different Onyx formulations. The key objectives were to: 1) validate the distal penetration results from CFD simulations with existing data from bench experiments, 2) compare the flow characteristics of Onyx formulations with differing viscosities in a blood vessel, 3) elucidate the impact of viscosity on distal penetration, and 4) understand how injection location affects distal penetration.
Using two-dimensional (2D) CFD simulations, we evaluated the propagation of two Onyx formulations (Onyx 18 and Onyx 34) inside a virtual neurovasculature filled with flowing water to mimic the presence of blood in blood vessels. Onyx was assumed to be a mixture of DMSO and EVOH. A physics-based model was developed to account for the change in viscosity of Onyx resulting from migration of DMSO in Onyx to the surrounding fluid (water). Navier-Stokes equations were solved using the commercially-available, finite-volume CFD code, Ansys Fluent. The mixture multiphase model in Fluent was used to track the evolution of the two fluids (Onyx and water), and a species transport equation was solved to account for mass transfer of DMSO from Onyx to water.
The multiphase, multispecies flow simulations were validated by comparing the distal penetration after reflux with available experimental results from bench tests. The predictions from the simulation capture the lava-like flow behavior of Onyx and closely match the experimental data of distal penetration. As expected, lower viscosity Onyx 18 penetrated more distally than Onyx 34 when evaluated with the same degree of reflux. Next, from the simulation results, the impact of viscosity change and the impact of injection location were analyzed.
Computational modeling and simulation can be used to create and analyze in-silico models representing physical systems and rapidly perform large numbers of tests to evaluate the different resulting outcomes without the need to build analogous physical prototypes. To the best of our knowledge, this is the first study to provide validation of multiphase CFD simulations against benchtop experimental data for Onyx embolization.
传统上，台式模型和动物模型一直被用于研究用于治疗脑动静脉畸形（AVM）的Onyx液体栓塞系统（Onyx）的扩散情况。然而，此类模型成本高昂，无法提供足够详细的信息来阐明Onyx粘度变化如何改变流动动力学，并且依赖一些反复试验，导致产品开发时间线拉长。
本研究的目标是利用计算流体动力学（CFD）模拟来预测不同Onyx配方的行为。关键目标是：1）用台式实验的现有数据验证CFD模拟的远端穿透结果；2）比较不同粘度的Onyx配方在血管中的流动特性；3）阐明粘度对远端穿透的影响；4）了解注射位置如何影响远端穿透。
我们使用二维（2D）CFD模拟，评估了两种Onyx配方（Onyx 18和Onyx 34）在充满流动水的虚拟神经血管系统内的扩散情况，以模拟血管中血液的存在。假设Onyx是二甲基亚砜（DMSO）和乙烯醇（EVOH）的混合物。开发了一个基于物理的模型，以解释由于Onyx中的DMSO向周围流体（水）迁移而导致的Onyx粘度变化。使用商业有限体积CFD代码Ansys Fluent求解纳维-斯托克斯方程。Fluent中的混合物多相模型用于跟踪两种流体（Onyx和水）的演变，并求解一个组分传输方程以解释DMSO从Onyx到水的传质过程。
通过将回流后的远端穿透与台式试验的现有实验结果进行比较，验证了多相、多组分流动模拟。模拟预测捕捉到了Onyx的熔岩状流动行为，并与远端穿透的实验数据紧密匹配。正如预期的那样，在相同回流程度下评估时，粘度较低的Onyx 18比Onyx 34向更远端穿透。接下来，从模拟结果中分析了粘度变化的影响和注射位置的影响。
计算建模和模拟可用于创建和分析代表物理系统的计算机模型，并快速进行大量测试以评估不同的最终结果，而无需构建类似的物理原型。据我们所知，这是第一项针对Onyx栓塞的多相CFD模拟与台式实验数据进行验证的研究。
