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本文首先分析了测量声衰减的信号接收装置。在此基础上,用直径0.06、0.5和1.4cm的三种压电接收换能器,在1—6MHz的频率范围内,测量超声在猪的心、肝、肌肉和脂肪组织中的声衰减系数,以研究这类换能器的相位对消效应对声衰减值造成的假象。经过实验证明:在测得的声衰减系数值中,确实潜在着压电换能器相位对消效应造成的假象;此种效应对声衰减数据的贡献大小,与接收换能器的面积大小相对应,同理论分析相一致;当使用小面积的换能器时,衰减系数与频率之间接近为线性关系。因此,要提高测量组织声衰减的精度,应采用小面积的压电换能器,或聚焦换能器。如果选用电声换能器、辐射力法和热学方法测量,可完全避免相位对消效应造成的假象。
This paper first analyzes the signal receiving device for measuring sound attenuation. On this basis, the acoustic attenuation coefficients of ultrasound in heart, liver, muscle and adipose tissue of pigs were measured in the frequency range of 1 to 6 MHz using three types of piezoelectric receiving transducers of 0.06, 0.5 and 1.4 cm in diameter In order to study the illusion of cancellation of the effect of acoustic attenuation on the phase of such transducers. It has been experimentally shown that there is indeed the potential for artifacts caused by cancellation of the phase of the piezoelectric transducer in the measured value of the acoustic attenuation coefficient. The contribution of such an effect to the acoustic attenuation data is proportional to the size of the receiving transducer Corresponding, consistent with the theoretical analysis; When using a small area of the transducer, the attenuation coefficient and the frequency between the close linear relationship. Therefore, to increase the accuracy of measuring tissue attenuation, a small area of piezoelectric transducer or focusing transducer should be used. If the choice of electro-acoustic transducers, radiation and thermal methods of measurement, can completely avoid the illusion of phase cancellation effect.