超声微泡造影剂的低频动力学行为

低频超声联合微泡造影剂有可能用于治疗肿瘤,因此开展造影剂低频的动力学特性研究是十分重要的。将低频声场(26.2kHz)中有壳和无壳的微泡造影剂视为以流体为负载的非线性振子,由带耗散函数的拉格朗日方程导出在不可压缩的粘滞流体中造影剂球对称振动的运动方程,利用球谐振腔和Mie散射技术对CO2微泡和带人白蛋白壳的全氟丙烷造影剂微泡进行了气泡散射光强I(t)曲线的实验测定,结果与数值模拟曲线相一致。表明:有壳和无壳的造影剂微泡在低频稳态空化时同样呈现大幅膨胀、迅速塌缩和回弹的非线性振荡;如处于内径较小的微血管中,微泡周期性大幅度(>血管内径)膨胀收缩将会引起血管轴向破裂,形成微血管栓塞;而在塌缩相,微泡内的气体被急剧压缩,泡内压强急剧增大,易在泡壁不稳定处形成高速微射流,诱发内皮细胞损伤而形成血栓。

Low frequency dynamic behavior of ultrasound microbubble contrast agent

The ultrasonic contrast agents(UCA) may be used in tumor therapy when UCA is irradiated by a low frequency ultrasound based on bubble cavitation and other nonlinear effects.Therefore study of UCA dynamic characteristics at low frequencies is necessary.The motion equa-tion describing spherical oscillation of a coated microbubble in an incompressible and weak viscosity liquid is derived from the Lagrangian equation with dissipation function when the microbubble is considered as loaded nonlinear vibrator with its incompressible shell in liquid at low frequencies.The scatterred light I(t) curves of CO2 microbubble and perfluoropropane(C3F8) microbubble with an albumine shell are measured with spherical resonant cell and laser Mie scattering technique,in good agreement with simulation results.It shows that coated UCA micro-bubbles undergo expanding collapsing and rebounding three phases in stable cavitation,such as free microbubbles.In transient cavitation,two kinds of bubble will expand to dozens,even hund-reds,of their original sizes,and break into fragments in few cycles under not very high acoustic pressure.In either case,micro blood vessels in tumors will be injured,which will lead to blood-clot formation.