IEEE Trans Ultrason Ferroelectr Freq Control. 2014 Mar;61(3):441-9. doi: 10.1109/TUFFC.2014.2929.
There is interest in examining the potential of modified intravascular ultrasound (IVUS) catheters to facilitate dual diagnostic and therapeutic roles using ultrasound plus microbubbles for localized drug delivery to the vessel wall. The goal of this study was to design, prototype, and validate an IVUS transducer for microbubble-based drug delivery. A 1-D acoustic radiation force model and finite element analysis guided the design of a 1.5-MHz IVUS transducer. Using the IVUS transducer, biotinylated microbubbles were displaced in water and bovine whole blood to the streptavidin-coated wall of a flow phantom by a 1.5-MHz center frequency, peak negative pressure = 70 kPa pulse with varying pulse repetition frequency (PRF) while monitoring microbubble adhesion with ultrasound. A fit was applied to the RF data to extract a time constant (τ). As PRF was increased in water, the time constant decreased (τ = 32.6 s, 1 kHz vs. τ = 8.2 s, 6 kHz), whereas in bovine whole blood an adhesion-no adhesion transition was found for PRFs ≥ 8 kHz. Finally, a fluorophore was delivered to an ex vivo swine artery using microbubbles and the IVUS transducer, resulting in a 6.6-fold increase in fluorescence. These results indicate the importance of PRF (or duty factor) for IVUS acoustic radiation force microbubble displacement and the potential for IVUS and microbubbles to provide localized drug delivery.
人们对于利用经过改良的血管内超声（IVUS）导管，通过超声联合微泡实现双重诊断和治疗功能，以将药物递送至血管壁的局部位置这一方案很感兴趣。本研究的目的是设计、制作并验证一种用于基于微泡的药物输送的 IVUS 换能器。一维声学辐射力模型和有限元分析指导了 1.5MHz IVUS 换能器的设计。使用 IVUS 换能器，通过施加中心频率为 1.5MHz、峰值负压=70kPa 的脉冲，并改变脉冲重复频率（PRF），将生物素化的微泡在水中和牛全血中置换到流态体模的链霉亲和素涂层壁上，同时利用超声监测微泡的黏附情况。对 RF 数据进行拟合，以提取时间常数（τ）。当 PRF 在水中增加时，时间常数减小（τ=32.6s，1kHz 与 τ=8.2s，6kHz），而在牛全血中，当 PRF≥8kHz 时，发现了黏附-不黏附的转变。最后，利用微泡和 IVUS 换能器将荧光团递送至离体猪动脉，从而使荧光强度增加了 6.6 倍。这些结果表明 PRF（或占空比）对于 IVUS 声辐射力微泡置换非常重要，并且 IVUS 和微泡具有提供局部药物输送的潜力。
