Single- PZT- Fiber Transducers for 3D Ultrasound Computed Tomography: Characterization and Modeling

In this work we present the characterization and modeling of ultrasound transducer arrays based on single-PZT-fiber transducers. The arrays were designed for a new generation of 3D ultrasound computed tomography (USCT) devices for breast cancer imaging. At the heart of the new arrays is a piezocomposite disk that features pseudo-random positioning of 18 individual transducers. Several hundred arrays were produced using semi-automated production processes and batch processing techniques. The acoustic characteristics of 54 single transducers were measured in an ultrasound testing setup. The transducers exhibit isotropic ultrasound emission, a large bandwidth (134%), and a wide opening angle (43°). This makes them well-suited for 3D USCT. A finite element model is presented for design analysis and further optimization. Initial differences between measured and modeled characteristics were reduced by adjusting piezoelectric constants, elastic properties of the passive materials and by including realistic damping in the model. As a result, the adjusted model predicts the acoustic performance over a wide range of emission angles and frequencies with good accuracy. Hence, the presented transducer arrays and the corresponding model provide a promising technology for current and future 3D USCT imaging systems.

I. Introduction

A new and promising imaging method for breast cancer screening is Ultrasound Computed Tomography (USCT) [1]. In comparison with mammography and magnetic resonance imaging, ultrasound is essentially harmless, cost-effective and does not require the use of potentially harmful contrast agents [2], [3]. The general idea of USCT for breast imaging is to surround the breast by many ultrasound transducers in a fixed setup. Typically, unfocused ultrasound waves are used for the scanning. Focusing is achieved by the applied image reconstruction algorithms.