Petrusca Lorena, Salomir Rares, Manasseh Gibran, Becker Christoph D, Terraz Sylvain
Hepatobiliary Interventional Radiology, Faculty of Medicine, University of Geneva , Geneva, Switzerland .
Int J Hyperthermia. 2015 Jun;31(4):421-32. doi: 10.3109/02656736.2015.1009501. Epub 2015 Mar 10.
The aim of this paper is to quantitatively investigate the thermal effects generated by the pre-focal interactions of a HIFU beam with a rib cage, in the context of minimally invasive transcostal therapy of liver malignancies.
HIFU sonications were produced by a phased-array MR-compatible transducer on Turkey muscle placed on a sheep thoracic cage specimen. The thoracic wall was positioned in the pre-focal zone 3.5 to 6.5 cm below the focus. Thermal monitoring was simultaneously performed using fluoroptic sensors inserted into the medullar cavity of the ribs and high resolution MR-thermometry (voxel: 1 × 1 × 5 mm3, four multi-planar slices).
MR-thermometry data indicated nearly isotropic distribution of the thermal energy at the ribs' surface. The temperature elevation at the focus was comparable with the pericostal temperature elevation around unprotected ribs, while being systematically inferior, by more than a factor of four on average, to the intra-medullar values. The spatial profiles of the pericostal and intra-medullar thermal build-up measurements could be smoothly connected using a Gaussian function. The dynamics of the post-sonication thermal relaxation as determined by fluoroptic measurements was demonstrated to be theoretically coherent with the experimental observations.
The experimental findings motivate further efforts for the transfer towards clinical routine of effective rib-sparing strategies for hepatic HIFU.
本文旨在定量研究高强度聚焦超声（HIFU）束与肋骨笼在肝脏恶性肿瘤微创经肋治疗背景下的焦前相互作用所产生的热效应。
使用相控阵磁共振兼容换能器在置于羊胸廓标本上的火鸡肌肉上进行HIFU超声处理。胸壁位于焦点下方3.5至6.5厘米的焦前区域。使用插入肋骨髓腔的荧光光纤传感器和高分辨率磁共振测温法（体素：1×1×5立方毫米，四个多平面切片）同时进行热监测。
磁共振测温数据表明肋骨表面热能分布近乎各向同性。焦点处的温度升高与未受保护肋骨周围的肋周温度升高相当，而平均而言，系统地低于髓内温度值四倍以上。肋周和髓内热积聚测量的空间分布可以用高斯函数平滑连接。荧光光纤测量确定的超声处理后热弛豫动力学在理论上与实验观察结果一致。
实验结果促使人们进一步努力将有效的肝脏HIFU肋骨保护策略转化为临床常规方法。
