A simple method for measuring complex acoustic impedance of biological tissues using a used quartz rod as a transmission line

The authors have developed a simple method of measuring the complex acoustic impedance of small biological materials for use as a tactile sensor in the field of endoscopic ultrasonography. Previous methods are too bulky for use in endoscopy. The reflection coefficient was measured by varying the distance between the end face of the transmission line and the surface of the sample. The real part of the impedance was calculated form the maximum and minimum values of the reflected signal and the imaginary part of the impedance was calculated for the distance. An experiment was conducted at 5 MHz using a 10-cm 2-mm diameter fused quartz rod. The experiment results show that the impedance can be measured with an accuracy of 5%