Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
J Acoust Soc Am. 2012 Jan;131(1):620-7. doi: 10.1121/1.3664001.
Ultrasonic transducers with a central hole are increasingly in use in high-intensity therapeutic ultrasound and similar medical applications. The hole is intended for the addition of a diagnostic device. Some fundamental properties of the fields produced by such transducers are investigated here theoretically, based on a Rayleigh integral algorithm. The approach is restricted to those cases where the Rayleigh integral can be fully solved to yield closed-formula results that can be easily used by the reader. This means a concentration on points on the field axis which, on the other hand, is most important under the aspect of the safety of the patient (maximum amplitudes). Closed-form expressions describing the influence of the central hole on the acoustic pressure, on the particle velocity and on the time-averaged intensity are presented. The relation between the true intensity and the intensity expression derived from the square of the acoustic pressure is discussed in some detail, an aspect which is important in ultrasonic measurement practice where the local intensity value is mostly assessed based on the square of a hydrophone signal.
带有中心孔的超声换能器在高强度治疗性超声及类似的医学应用中越来越多地被使用。该孔用于添加诊断设备。此处基于瑞利积分算法从理论上对这种换能器产生的场的一些基本性质进行了研究。该方法仅限于那些可以完全求解瑞利积分以给出闭式解的情况，以便读者可以轻松使用。这意味着集中于场轴上的点，而从患者安全（最大幅度）的角度来看，这一点又是最重要的。给出了描述中心孔对声压、质点速度和时均强度的影响的闭式表达式。还详细讨论了真实强度与根据声压平方得到的强度表达式之间的关系，这在超声测量实践中是很重要的，因为在该实践中通常基于水听器信号的平方来评估局部强度值。
