Translational Research in Ultrasound Theranostics Laboratory, School of Biomedical Engineering, ShanghaiTech University, Shanghai, China; State Key Laboratory of Advanced Medical Materials and Devices, ShanghaiTech University, Shanghai, China.
Department of Radiology, University of Calgary, Calgary, Canada; Department of Clinical Neurosciences, University of Calgary, Calgary, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Canada.
Ultrason Sonochem. 2024 Jul;107:106889. doi: 10.1016/j.ultsonch.2024.106889. Epub 2024 Apr 27.
Recently, our group developed a synergistic brain drug delivery method to achieve simultaneous transcranial hyperthermia and localized blood-brain barrier opening via MR-guided focused ultrasound (MRgFUS). In a rodent model, we demonstrated that the ultrasound power required for transcranial MRgFUS hyperthermia was significantly reduced by injecting microbubbles (MBs). However, the specific mechanisms underlying the power reduction caused by MBs remain unclear. The present study aims to elucidate the mechanisms of MB-enhanced transcranial MRgFUS hyperthermia through numerical studies using the finite element method. The microbubble acoustic emission (MAE) and the viscous dissipation (VD) were hypothesized to be the specific mechanisms. Acoustic wave propagation was used to model the FUS propagation in the brain tissue, and a bubble dynamics equation for describing the dynamics of MBs with small shell thickness was used to model the MB oscillation under FUS exposures. A modified bioheat transfer equation was used to model the temperature in the rodent brain with different heat sources. A theoretical model was used to estimate the bubble shell's surface tension, elasticity, and viscosity losses. The simulation reveals that MAE and VD caused a 40.5% and 52.3% additional temperature rise, respectively. Compared with FUS only, MBs caused a 64.0% temperature increase, which is consistent with our previous animal experiments. Our investigation showed that MAE and VD are the main mechanisms of MB-enhanced transcranial MRgFUS hyperthermia.
最近，我们小组开发了一种协同的脑内药物输送方法，通过磁共振引导聚焦超声（MRgFUS）实现经颅热疗和局部血脑屏障开放的同步。在啮齿动物模型中，我们证明通过注射微泡（MBs）可以显著降低经颅 MRgFUS 热疗所需的超声功率。然而，MB 引起的功率降低的具体机制尚不清楚。本研究旨在通过有限元方法的数值研究阐明 MB 增强经颅 MRgFUS 热疗的机制。假设微泡声致发光（MAE）和粘性耗散（VD）是特定的机制。声传播用于模拟 FUS 在脑组织中的传播，并且使用描述在 FUS 暴露下 MB 振动的小壳厚度的 MB 动力学方程来模拟 MB 振动。使用改进的生物传热方程来模拟具有不同热源的啮齿动物大脑中的温度。理论模型用于估计气泡壳的表面张力、弹性和粘性损失。模拟表明，MAE 和 VD 分别导致 40.5%和 52.3%的额外温升。与仅 FUS 相比，MB 导致 64.0%的温升，这与我们之前的动物实验一致。我们的研究表明，MAE 和 VD 是 MB 增强经颅 MRgFUS 热疗的主要机制。
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