Department of Imaging Research, Sunnybrook Research Institute, Toronto, Canada.
Phys Med Biol. 2010 Sep 21;55(18):5251-67. doi: 10.1088/0031-9155/55/18/001. Epub 2010 Aug 18.
Microbubble-mediated disruption of the blood-brain barrier (BBB) for targeted drug delivery using focused ultrasound shows great potential as a therapy for a wide range of brain disorders. This technique is currently at the pre-clinical stage and important work is being conducted in animal models. Measurements of standing waves in ex vivo rat skulls were conducted using an optical hydrophone and a geometry dependence was identified. Standing waves could not be eliminated through the use of swept frequencies, which have been suggested to eliminate standing waves. Definitive standing wave patterns were detected in over 25% of animals used in a single study. Standing waves were successfully eliminated using a wideband composite sharply focused transducer and a reduced duty cycle. The modified pulse parameters were used in vivo to disrupt the BBB in a rat indicating that, unlike some other bioeffects, BBB disruption is not dependent on standing wave conditions. Due to the high variability of standing waves and the inability to correctly estimate in situ pressures given standing wave conditions, attempts to minimize standing waves should be made in all future work in this field to ensure that results are clinically translatable.
微泡介导的血脑屏障（BBB）破坏用于靶向药物递送的聚焦超声显示出作为治疗广泛的脑疾病的治疗方法的巨大潜力。该技术目前处于临床前阶段，正在动物模型中进行重要的工作。使用光学水听器对离体大鼠颅骨中的驻波进行了测量，并确定了其存在几何依赖性。虽然已经有人建议使用扫频来消除驻波，但实际上并不能消除驻波。在一项研究中使用的超过 25%的动物中都检测到了明确的驻波模式。使用宽带复合锐聚焦换能器和降低的占空比成功地消除了驻波。修改后的脉冲参数用于体内破坏大鼠的 BBB，表明与其他一些生物效应不同，BBB 破坏不依赖于驻波条件。由于驻波的高度可变性以及无法根据驻波条件正确估计原位压力，因此应在该领域的所有未来工作中尽量减少驻波的产生，以确保结果具有临床可转化性。
