Department of Radiology, Brigham and Women's Hospital, Boston, MA, United States of America.
Department of Neuro-oncology, Dana Farber Cancer Institute, Boston, MA, United States of America.
J Control Release. 2024 Aug;372:194-208. doi: 10.1016/j.jconrel.2024.06.036. Epub 2024 Jun 21.
PURPOSE: We report our experience disrupting the blood-brain barrier (BBB) to improve drug delivery in glioblastoma patients receiving temozolomide chemotherapy. The goals of this retrospective analysis were to compare MRI-based measures of BBB disruption and vascular damage to the exposure levels, acoustic emissions data, and acoustic simulations. We also simulated the cavitation detectors. METHODS: Monthly BBB disruption (BBBD) was performed using a 220 kHz hemispherical phased array focused ultrasound system (Exablate Neuro, InSightec) and Definity microbubbles (Lantheus) over 38 sessions in nine patients. Exposure levels were actively controlled via the cavitation dose obtained by monitoring subharmonic acoustic emissions. The acoustic field and sensitivity profile of the cavitation detection system were simulated. Exposure levels and cavitation metrics were compared to the level of BBBD evident in contrast-enhanced MRI and to hypointense regions in T2*-weighted MRI. RESULTS: Our treatment strategy evolved from using a relatively high cavitation dose goal to a lower goal and longer sonication duration and ultimately resulted in BBBD across the treatment volume with minimal petechiae. Subsonication-level feedback control of the exposure using acoustic emissions also improved consistency. Simulations of the acoustic field suggest that reflections and standing waves appear when the focus is placed near the skull, but their effects can be mitigated with aberration correction. Simulating the cavitation detectors suggest variations in the sensitivity profile across the treatment volume and between patients. A correlation was observed with the cavitation dose, BBBD and petechial hemorrhage in 8/9 patients, but substantial variability was evident. Analysis of the cavitation spectra found that most bursts did not contain wideband emissions, a signature of inertial cavitation, but biggest contribution to the cavitation dose - the metric used to control the procedure - came from bursts with wideband emissions. CONCLUSION: Using a low subharmonic cavitation dose with a longer duration resulted in BBBD with minimal petechiae. The correlation between cavitation dose and outcomes demonstrates the benefits of feedback control based on acoustic emissions, although more work is needed to reduce variability. Acoustic simulations could improve focusing near the skull and inform our analysis of acoustic emissions. Monitoring additional frequency bands and improving the sensitivity of the cavitation detection could provide signatures of microbubble activity associated with BBB disruption that were undetected here and could improve our ability to achieve BBB disruption without vascular damage.
目的:我们报告了在接受替莫唑胺化疗的胶质母细胞瘤患者中破坏血脑屏障 (BBB) 以改善药物递送的经验。本回顾性分析的目的是比较基于 MRI 的 BBB 破坏和血管损伤与暴露水平、声发射数据和声学模拟的关系。我们还模拟了空化探测器。
方法:在 9 名患者的 38 次治疗中,使用 220 kHz 半球形相控阵聚焦超声系统(ExablateNeuro,InSightec)和 Definity 微泡(Lantheus)每月进行一次 BBB 破坏(BBBD)。通过监测次谐波声发射获得的空化剂量,主动控制暴露水平。模拟了声场和空化检测系统的灵敏度分布。将暴露水平和空化指标与对比增强 MRI 中明显的 BBBD 水平以及 T2*-加权 MRI 中的低信号区域进行比较。
结果:我们的治疗策略从使用相对较高的空化剂量目标演变为较低的目标和更长的超声持续时间,最终导致治疗体积内出现 BBBD,同时最小化瘀点。使用声发射对暴露进行亚声级反馈控制也提高了一致性。声场模拟表明,当焦点放置在颅骨附近时,会出现反射和驻波,但可以通过像差校正来减轻其影响。模拟空化探测器表明,在治疗体积内和患者之间,灵敏度分布存在差异。在 8/9 名患者中,观察到空化剂量、BBBD 和瘀点性出血之间存在相关性,但存在明显的变异性。对空化光谱的分析发现,大多数脉冲不包含宽带发射,这是空化的特征,但对空化剂量的贡献最大-用于控制该过程的指标-来自具有宽带发射的脉冲。
结论:使用低次谐波空化剂量和较长的持续时间可导致最小瘀点的 BBBD。空化剂量与结果之间的相关性表明,基于声发射的反馈控制具有优势,尽管需要进一步工作来减少变异性。声学模拟可以改善颅骨附近的聚焦,并为我们的声发射分析提供信息。监测附加频带并提高空化检测的灵敏度可以提供与 BBB 破坏相关的微泡活动的特征,这些特征在这里没有被检测到,并且可以提高我们在不造成血管损伤的情况下实现 BBB 破坏的能力。
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