高强度聚焦超声辐照离体牛肝组织后B超声像图出现强回声的原因

摘要

目的 研究B超监控高强度聚焦超声(HIFU)治疗后声像图中强回声出现的原因.方法 HIFU定点辐照离体牛肝组织,深度为15mm,辐照功率分别采用50、100、150、200、250和300w,通过MR测温仪得到不同功率下组织最高温度达到55℃时所需辐照时间.将结果用于B超监控HIFU中,并通过被动空化检测(PCD)实时观察辐照过程中声信号的频域特性.结果 辐照功率50w时虽有组织凝固性坏死,但B超声像图中无强回声出现,且通过PCD在频域信号中未观察到二分之一次谐波;功率≥100w时出现凝固性坏死,且声像图中有强回声出现,频域信号中可明显观察到二分之一次谐波.结论 无沸腾气泡产生时,HIFU辐照离体牛肝组织后,空化效应产生的空化泡致使B超声像图中出现强回声.%Objective To investigate the causes of the appearance of hyperechoic regions of ex vivo bovine liver on B-mode ultrasonography after high intensity focused ultrasound (HIFU) therapy. Methods HIFU with power of 50, 100, 150,200, 250 and 300 W was used separately to irradiate the fresh ex vivo ox liver with the focal depth of 15 mm. Then the irradiation time of the different powers were obtained through MR, with the highest temperature in the focal region getting to 55℃, and were used for B-mode ultrasonography monitoring HIFU, while the passive cavitation detection (PCD) was used to reflect the cavitation activity during irradiation. Results When the radiation power was 50 W, no echo enhancement was found, though coagulative necrosis was observed, and the half harmonic emission was not observed through PCD. When power was not less than 100 W, the coagulative necrosis, echo enhancement and the half harmonic emissions could be observed. Conclusion When no boiling bubbles arise, the appearance of hyperechoic regions on B-mode ultrasonography after HIFU is caused by acoustic cavitation bubbles.