Probing acoustic fields of clinically relevant transducers: the effect of hydrophone probes' finite apertures and bandwidths.
Probing acoustic fields of clinically relevant transducers: the effect of hydrophone probes' finite apertures and bandwidths.
复制标题
探测临床相关换能器的声场：水听器探头有限孔径和带宽的影响。
DOI：
10.1109/tuffc.2004.1350954
复制
发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Nowicki,Andrzej
中科院分区：
文献类型：
--
作者：
Radulescu,EmilG;Lewin,PeterA;Wójcik,Janusz;Nowicki,Andrzej
利用一个完整的声波传播模型，研究了压电超声水听器探头的有限孔径和频率响应对自由场脉冲强度积分(PII)和力学指数(MI)的影响。开发的模型能够预测该场中几乎任何点的真实压力-时间波形。模型的输入使用在所考虑的声源或换能器附近测量的压力幅度数据。模型的实验验证是使用商用的8 MHz动态聚焦的线阵和单个单元的5 MHz的聚焦矩形源进行的。验证是在低和高激发水平下进行的，分别对应于线性和非线性声波传播。使用具有不同灵敏度、频率响应、带宽和有源元件直径的压电聚合物水听器探头记录压力-时间波形。探头的标称直径从50到500个微米/米，它们的可用带宽在55到100兆赫之间变化。用来计算热指数(TI)的PII随着探头带宽的增加和有效孔径的减小而增大。另一个安全指标MI也受到了影响，但影响程度较小。使用该模型预测的修正被用来减少PII测定中高达30%的偏差。结果表明，通过考虑水听器的有限孔径和校正PII的值，所有由PII得到的强度都可以得到空间平均误差的校正。结果还指出，在比较声学输出数据时应谨慎行事。特别是，为了正确确定成像换能器产生的MI、TI和总声输出功率，需要水听器的有效直径和灵敏度的频率特性。
The influence of finite aperture and frequency response of piezoelectric ultrasonic hydrophone probes on the free-field pulse intensity integral (PII) and mechanical index (MI) was investigated using a comprehensive acoustic wave propagation model. The model developed was capable of predicting the true pressure-time waveforms at virtually any point in the field. The input to the model used pressure amplitude data measured in the immediate vicinity of the acoustic source or transducer considered. The experimental verification of the model was obtained using a commercially available, 8 MHz, dynamically focused linear array and a single element, 5 MHz, focused rectangular source. The verification was performed at low and high excitation levels, corresponding to linear and nonlinear acoustic wave propagation, respectively. The pressure-time waveforms were recorded using piezoelectric polymer hydrophone probes that had different sensitivities, frequency responses, bandwidths, and active element diameters. The nominal diameters of the probes ranged from 50 to 500 /spl mu/m, and their useable bandwidths varied between 55 and 100 MHz. The PII, used to calculate the thermal index (TI), was found to increase with increasing bandwidth and decreasing effective aperture of the probes. The MI, another safety indicator, also was affected, but to a lesser extent. The corrections predicted using the model were used to reduce discrepancies as large as 30% in the determination of PII. The results of this work indicate that, by accounting for hydrophones' finite aperture and correcting the value of PII, all intensities derived from the PII can be corrected for spatial averaging error. The results also point out that caution should be exercised when comparing acoustic output data. In particular, hydrophone's frequency characteristics of the effective diameter and sensitivity are needed to correctly determine the MI, TI, and the total acoustic output power produced by an imaging transducer.