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In modern ultrasound imaging devices, two-dimensional probes and electronic scanning allow volumetric imaging of anatomical structures. When dealing with the design of such complex 3-D ultrasound (US) systems, as the number of transducers and channels dramatically increases, new challenges concerning the integration of electronics and the implementation of smart micro-beamforming strategies arise. Hence, the possibility to predict the behavior of the whole system is mandatory. In this paper, we propose and describe an advanced simulation tool for ultrasound system modeling and simulation, which conjugates the US propagation and scattering, signal transduction, electronic signal conditioning, and beamforming in a single environment. In particular, we present the architecture and model of an existing 16-channel integrated receiver, which includes an amplification and micro-beamforming stage, and validate it by comparison with circuit simulations. The developed model is then used in conjunction with the transducer and US field models to perform a system simulation, aimed at estimating the performance of an example 3-D US imaging system that uses a capacitive micromachined ultrasonic transducer (CMUT) 2-D phased-array coupled to the modeled reception front-end. Results of point spread function (PSF) calculations, as well as synthetic imaging of a virtual phantom, show that this tool is actually able to model the complete US image reconstruction process, and that it could be used to quickly provide valuable system-level feedback for an optimized tuning of electronic design parameters.

The present invention relates to a transducer device having a planar array of electroacoustic cells, each including a piezoelectric bilayer unit. The transducer device achieves high transmission sensitivity across a broad bandwidth. The transducer device may be designed to have a broad or a focused directivity pattern, or may be multi-frequency, depending on the particular application and has a range of applications. For example, the transducer device may be used with an implanted passive ultrasonically excitable resonating sensor, to excite the sensor and/or to interrogate the sensor, for example in conjunction with Doppler-based analysis of the resonance frequency of the sensor, and/or to locate an implanted sensor. The invention also relates to a method of manufacturing the device.

Silicon surface micromachining can be successfully used in the fabrication of ultrasonic transducers (cMUT) which exhibit promising performance improvements with respect to the PZT devices for medical applications such as echographic systems. The micro-fabrication of these transducers is still affected by a number of critical steps, among which wafer bonding, through-silicon via (TSV) interconnects, critical patterning of the vibrating membrane and bad acoustic properties of the silicon substrate. In order to address these problems a new fabrication sequence was introduced by Caliano et. al., in which the fabrication approach is top-down (“reverse technology”). Advantages of this fabrication are: no membrane patterning, low temperature processing (which avoids mechanical instability introduced by high temperature treatments), complete removal of the silicon substrate, reverse packaging with standard wire bonding (no need for TSV). This technology was developed and patented at Roma Tre University.

Capacitive micromachined ultrasonic transducers (cMUTs) are micro-electromechanical devices (MEMS) fabricated using silicon micromachining techniques. In the past decade, their use has proved to be attractive mainly in the field of medical ultrasound imaging as active elements in ultrasound probes. The interest of this novel technology relies in its full compatibility with standard integrated circuit technology that makes it possible to integrate, on the same chip, the transducers and the electronics, thus enabling the realization of extremely compact and high-performance devices.

In this chapter the basic principles, the fabrication process, and some modelling approaches of the novel micromachined ultrasonic transducers (MUTs) are described. These transducers utilize the flex-tensional vibration of an array of micro membranes. They are usually called cMUT (capacitive Micromachined Ultrasonic Transducer) or pMUT (piezoelectric Micromachined Ultrasonic Transducer) depending on the actuation principle, electrostatic or piezoelectric. For water coupling applications both these kinds of transducers offer a better matching to the load compared with the typical piezoelectric transducers and therefore they have a larger intrinsic bandwidth. Here emphasis is given to the cMUTs because they have shown good electroacoustic characteristics, which parallel, or even exceed, those of conventional piezoelectric transducers. Good echographic images of internal organs of the human body have been obtained demonstrating the possibilities of this technology to be utilized in commercial 1D and 2D probes for medical applications. At present pMUTs are in a very early stage of development and the potential advantages over the cMUTs are still to be demonstrated.

Real-time 3D ultrasound imaging is based on volumetric beam steering and sweeping. Transducer capable to perform volumetric beamforming for medical imaging are typically two dimensional arrays of thousands of active elements. Electronic multiplexing and pre-beamforming is necessary in order to interface such arrays to conventional ultrasound scanners. This paper describes an alternative approach for volumetric beamforming based on a particular two dimensional array of a reduced number of elements obtained by superimposing two linear arrays on the same area. Capacitive Micromachined Ultrasonic Transducer (cMUT) technology is mentioned as a good candidate to approach the problem due to the possibility given by micromachining to fabricate arbitrarily shaped electrode patterns which define the array elements. The beamforming strategy is illustrated and assessed by means of beampattern calculations and synthetic 3D imaging formation. The resulting array is directly connectable to a standard imaging system.

Ultrasound transducer comprising an array of electro-acoustic micro-cells, a first and a second group of transducer elements arranged substantially along two directions (x, y), each element being defined by a group of micro-cells of the array, at least part of the micro-cells of each group being electrically interconnected by a first connection pattern having shape with main orientation along one of the two directions (x, y), characterized in that each group of micro- cells defining each element comprises micro-cells interconnected by further connection pattern or patterns having shape with main orientation along the other of the two directions (y, x).