Experimental Investigation of Inter-element Isolation in a Medical Array Transducer at Various Manufacturing Stages

Abstract

This work presents the experimental investigation of vibration maps of a linear array transducer with 192 piezoelements by means of a laser Doppler vibrometer at various manufacturing finishing steps in air and in water. Over the years, many researchers have investigated cross-coupling in fabricated prototypes but not in arrays at various manufacturing stages. Only the central element of the array was driven at its working frequency of 5 MHz. The experimental results showed that the contributions of cross-coupling depend on the elements of the acoustic stack: Lead Zirconate Titanate (PZT), kerf, filler, matching layer, and lens. The oscillation amplitudes spanned from (6 ± 38%) nm to (110 ± 40%) nm when the energized element was tested in air and from (6 ± 57%) nm to (80 ± 67%) nm when measurements were obtained under water. The best inter-element isolation of -22 dB was measured in air after cutting the kerfs, whereas the poorest isolation was -2 dB under water with an acoustic lens (complete acoustic stack). The vibration pattern in water showed a higher standard deviation on the displacement measurements than the one obtained in air, due to the influence of acousto-optic interactions. The amount increased to 30% in water, as estimated by a comparison with the measurements in air. This work describes a valuable method for manufacturers to investigate the correspondence between the manufacturing process and the quantitative evaluations of the resulting effects.

The Core of Medical Imaging: State of the Art and Perspectives on the Detectors

“…Despite many medical applications, such as ultrasound elastometry [5], which could be better understood using 3D information, ultrasonic imaging is still based on twodimensional image acquisition and processing. Going from 2D to 3D ultrasound imaging, a 2D matrix transducer is required, entailing fabrication and implementation problems [6]. This is the reason why 3D ultrasound imaging methods based on 2-D array probes are continuing to improve in terms of fabrication and processing [7,8], and synthetic aperture ultrasound imaging [9,10].…”

“…where B is the −3 dB coil bandwidth. Equation ( 8) can be used to measure both loaded and unloaded coil quality factors and, successively, for r ratio estimation, according to Equation (6).…”