Centre de Recherche Cardio-Thoracique, Université de Bordeaux, Bordeaux, France.
Ultrasound Med Biol. 2013 Aug;39(8):1388-97. doi: 10.1016/j.ultrasmedbio.2013.01.014. Epub 2013 Apr 3.
Bubble-enhanced heating (BEH) can be exploited to increase heating efficiency in treatment of liver tumors with non-invasive high-intensity focused ultrasound (HIFU). The objectives of this study were: (i) to demonstrate the feasibility of increasing the heating efficiency of sonication exploiting BEH in pig liver in vivo using a clinical platform; (ii) to determine the acoustic threshold for such effects with real-time, motion-compensated magnetic resonance-guided thermometry; and (iii) to compare the heating patterns and thermal lesion characteristics resulting from continuous sonication and sonication including a burst pulse. The threshold acoustic power for generation of BEH in pig liver in vivo was determined using sonication of 0.5-s duration ("burst pulse") under real-time magnetic resonance thermometry. In a second step, experimental sonication composed of a burst pulse followed by continuous sonication (14.5 s) was compared with conventional sonication (15 s) of identical energy (1.8 kJ). Modification of the heating pattern at the targeted region located at a liver depth between 20 and 25 mm required 600-800 acoustic watts. The experimental group exhibited near-spherical heating with 40% mean enhancement of the maximal temperature rise as compared with the conventional sonication group, a mean shift of 7 ± 3.3 mm toward the transducer and reduction of the post-focal temperature increase. Magnetic resonance thermometry can be exploited to control acoustic BEH in vivo in the liver. By use of experimental sonication, more efficient heating can be achieved while protecting tissues located beyond the focal point.
利用气泡增强加热（BEH）可以提高非侵入性高强度聚焦超声（HIFU）治疗肝肿瘤的加热效率。本研究的目的是：（i）利用临床平台在猪肝中证明利用 BEH 提高超声加热效率的可行性；（ii）利用实时、运动补偿磁共振引导测温确定产生这种效应的声阈；（iii）比较连续超声和包括脉冲爆震的超声产生的加热模式和热损伤特征。通过实时磁共振测温，确定猪肝内产生 BEH 的阈声功率。在第二步中，实验性超声由脉冲爆震后连续超声（14.5 s）组成，与相同能量（1.8 kJ）的常规超声（15 s）进行比较。位于 20 至 25 毫米肝脏深度的靶区加热模式的改变需要 600-800 瓦声功率。实验组与常规超声组相比，表现出近球形加热，最大温升的平均增强幅度为 40%，向换能器的平均位移为 7 ± 3.3 毫米，焦点后温度升高降低。磁共振测温可用于控制肝脏内的声 BEH 。通过使用实验性超声，可以在保护焦点以外组织的同时实现更有效的加热。
