State Key Laboratory of Ultrasound Engineering in Medicine Co-founded by Chongqing and the Ministry of Science and Technology, Chongqing Medical University, Chongqing 400016, China.
Ultrasonics. 2011 Apr;51(3):369-75. doi: 10.1016/j.ultras.2010.11.002. Epub 2010 Nov 19.
High intensity focused ultrasound (HIFU) has become a new noninvasive surgical modality in medicine. A portion of tissue seated inside a patient's body may experience coagulative necrosis after a few seconds of insonification by high intensity focused ultrasound (US) generated by an extracorporeal focusing US transducer. The region of tissue affected by coagulative necrosis (CN) usually has an ellipsoidal shape when the thermal effect due to US absorption plays the dominant role. Its long and short axes are parallel and perpendicular to the US propagation direction respectively. It was shown by numerical computations using a nonlinear Gaussian beams model to describe the sound field in a focal zone and ex vivo experiments that the dimension of the short and long axes of the tissue which experiences CN can be as small as 50μm and 250μm respectively after one second exposure of US pulse (the spatial and pulse average acoustic power is on the order of tens of Watts and the local acoustic spatial and temporal pulse averaged intensity is on the order of 3×10(4)W/cm(2)) generated by a 1.6MHz HIFU transducer of 12cm diameter and 11cm geometric focal length (f-number=0.92). The concept of thermal dose of cumulative equivalent minutes was used to describe the possible tissue coagulative necrosis generated by HIFU. The numbers of cells which suffered CN were estimated to be on the order of 40. This result suggests that HIFU is able to interact with tens of cells at/near its focal zone while keeping the neighboring cells minimally affected, and thus the targeted cell surgery may be achievable.
高强度聚焦超声（HIFU）已成为医学领域一种新的非侵入性手术方式。当高强度聚焦超声（US）通过体外聚焦 US 换能器产生的几秒钟内，位于患者体内的一部分组织可能会经历凝固性坏死。当 US 吸收引起的热效应起主导作用时，受凝固性坏死（CN）影响的组织区域通常呈椭圆形。其长轴和短轴分别与 US 传播方向平行和垂直。数值计算表明，使用非线性高斯束模型来描述焦区中的声场，并进行离体实验，在 1.6MHz 的 HIFU 换能器（直径 12cm，几何焦距 11cm（f-number=0.92））产生的 US 脉冲（空间和脉冲平均声功率约为数十瓦，局部声时空脉冲平均强度约为 3×10(4)W/cm(2)）持续 1 秒后，经历 CN 的组织的短轴和长轴尺寸可分别小至 50μm 和 250μm。累积等效分钟热剂量的概念用于描述 HIFU 可能产生的组织凝固性坏死。估计经历 CN 的细胞数量约为 40 个。这一结果表明，HIFU 能够在其焦区附近与数十个细胞相互作用，同时使邻近细胞受到最小影响，从而实现靶向细胞手术。
