Guillaume Ferin

3F-6 Ultra-Wide Bandwidth Array for New Imaging Modalities

A dual frequency probe composed of two outer low frequency arrays and one inner high frequency array is designed through a simulation stage, manufactured and fully characterized. Electroacoustical, acoustical and electrical properties suited the imaging modalities requiring an ultra wide bandwidth. The presented array transducer is a 128 elements linear array for superficial imaging with targeted frequency range from 2 MHz to 10 MHz. Electroacoustic and acoustic performances measured are close to those simulated. The device provides an ultra wide bandwidth of 130% improving superharmonic imaging.

Improving ultrasound imaging with integrated electronics

This paper presents an integrated electronic preamplifier design based on discrete components and evaluates its impact on image performances. The electronic, located close to the transducer, incorporates all useful functions to ensure compatible direct connection with most ultrasound scanners available on the market today. People who has worked on this subject know that numerous challenges and problems have to be overcome: high voltage bypass, preamplifier protection cells, miniaturization, power dissipation, electronic stability and many other constraints. We will discuss different unavoidable tradeoffs, starting with electrical performances and then with practical aspects. Our electronic solution has been evaluated with different probe configurations, namely a 5 MHz Phased Array and a 9.5 MHz Linear Array probe. Images have been acquired and analysis of signal to noise ratio (SNR) performed to quantify the gain in image quality.

P4M-5 Accurate Assessment of CMUT Devices Through Precise Electrical Impedance Measurement in Air

This paper reports a technique to exploit results from electrical impedance measurement of cMUT devices in air. An analytical ID model has been used as a fitting function. The accuracy of this model has been theoretically analysed.

Specific Ultrasound Data Acquisition for Tissue Motion and Strain Estimation: Initial Results

Ultrasound applications such as elastography can benefit from 3-D data acquisition and processing. In this article, we describe a specific ultrasound probe, designed to acquire series of three adjacent imaging planes over time. This data acquisition makes it possible to consider the out-of-plane motion that can occur at the central plane during medium scanning, and is proposed with the aim of improving the results of strain imaging. In this first study, experiments were conducted on phantoms, and controlled axial and elevational displacements were applied to the probe using a motorized system. Radiofrequency ultrasound data were acquired at a 40-MHz sampling frequency with an Ultrasonix ultrasound scanner, and processed using a 3-D motion estimation method. For each of the 2-D regions of interest of the central plane in pre-compression data, a 3-D search was run to determine its corresponding version in post-compression data, with this search taking into account the region-of-interest deformation model chosen. The results obtained with the proposed ultrasound data acquisition and strain estimation were compared with results from a classic approach and illustrate the improvement produced by considering the mediums local displacements in elevation, with notably an increase in the mean correlation coefficients achieved.

Powering autonomous wireless sensors with miniaturized piezoelectric based energy harvesting devices for NDT applications

IoT (Internet of Things) is driving an intense research activity targeting novel consumer applications. It has also an industrial counterpart, where thousands of sensors can be connected together into a proprietary network, i.e. into a Wireless Sensor Network (WSN). Such Industrial WSN may exhibit various shapes for different kind of applications. It can indeed be used for Structure Health Monitoring (SHM) to survey bridges, railways, avionic or automotive structures, rotating machine maintenance prediction, it can also serve security purposes like fire forest detection, border security, etc. In this paper we presents the architecture of a miniaturized and low-frequency piezoelectric-based vibrational-energy harvesting device (PEH) and its advanced manufacturing process flow. This harvesting technique uses direct piezoelectric effect to transform mechanical vibrations into electrical power. Over the past decade, several MEMS architectures have been built and assessed to harvest such low frequency (50-75Hz) vibrations. MEMS based PEH use thin (<;5μm) and thick (<;50μm) piezoelectric films allowing a high degree of integration and miniaturization, but at low frequencies the amount of harvested energy is not enough to power sensing electronics which typically consumes 100μW in average during 200ms. To overcome this limitation, we have developed and optimized a thinning process that enable us to use ultra-thin bulk PZT material (<;20μm) and propose a performant and miniaturized PEH.

Dual mode cMUTs fabricated with LPCVD sacrificial release process

This paper aims to develop an integrated dual mode ultrasonic transducers (based on cMUTs technology) for applications of targeted drug delivery dedicated to small animal experiments. Two functions are designed on the same transducer: one for high frequency imaging and the other for thermal activation of liposomes. Tests and performances evaluation are reported.

Focused 20 MHz single-crystal piezocomposite ultrasound array

Lead-based piezoelectric single crystals such as PZN-PT and PMN-PT have been first developed for under water applications by the U.S. Navy. Their outstanding piezoelectric properties (d33 as high as 2000 pC/N and k33 > 90%) make them valuable for high-end ultrasound transducers. Thus, they have been successfully used and commercialized in medical field mainly for cardiac imaging (2-5 MHz) but manufacturing such a probe is critical since single crystal structures are more sensitive to thermal and mechanical stresses induced by standard micromachining process. We propose in this paper to manufacture a high frequency ultrasound probe (15-20 MHz) based on very thin 1-3 single crystal composite materials (<70 ¿m thick) using low-stressing machining process and exhibiting improved electroacoustical performances. This paper presents the acoustical design, fabrication and evaluation of an ultrasound array based on single crystal piezocomposite. The array specifications were a 3 mm elevation, 100 ¿m pitch, 20 MHz center frequency. We demonstrate the feasibility to produce a PMN-PT single crystal probe with suitable performances for high resolution imaging. A complete electro-acoustical characterization has been done: bandwidth, directivity and pressure performances are then discussed and compared to classical PZT probes with the same specifications. Performances are compared to those obtained with state-of-the-art piezocomposite transducers, achieving competitive bandwidth and an improvement of +6 dB in sensitivity.

Micromachined probe performance assessment

In recent years, Capacitive Micromachined Ultrasound Transducer (CMUT) technology was widely investigated and functional prototypes have been released by several R&D teams. CMUT technology offers outstanding characteristics in acoustic, interconnect packaging capabilities or in integration features that are exciting criteria for new medical applications. We propose a full acoustic characterization report of a CMUT probe. A linear array was fully packaged with electronic preamplifier boards integrated. A complete acoustic characterization of the probe is then performed and presented. In a second phase, a linear probe with piezocomposite technology is realized. The conception is done in regard to the geometric characteristics and to the acoustic response of the micromachined probe. Then an electro‐acoustical benchmark CMUT / piezocomposite is realized in the closest conditions. Using a commercial ultrasound imaging platform, an image assessment is performed. The images are first analysed in a quantitative w...

Two-dimensional electroacoustic model of transducer array based on 1-3 piezocomposite materials

An analytical model is presented to achieve simultaneous prediction of the elementary electroacoustic response and directivity pattern of a one-dimensional (1D) piezocomposite array. The theoretical approach was based on guided wave theory in a multilayered structure in which the 1-3 piezocomposite material is considered as a homogeneous piezoelectric plate. A matrix method was applied to simulate the displacement fields generated at the surface of the array when one element was excited with an electrical pulse. A test device was manufactured, then characterized through measurements of displacement performed with an interferometric laser probe when the array vibrated in air and in water. The experimental results are presented and compared with theory

High frequency row column addressed matrix array for volumetric ultrafast ultrasound imaging

Volumetric “ultrafast” imaging is one of the major trends in ultrasound imaging techniques. It indeed paves the way for novel modalities when combined with Doppler, elastography and contrast imaging [1]. Unfortunately, due to the complexity and the inherently unaffordable costs, fully populated matrix-based systems are facing to pricing problems that limit their commercial development. Recently, row-column addressed (RCA) matrix transducer approaches have been proposed to overcome both complexity and costs issues but in a limited frequency range, i.e. below 10MHz. However, there is also a tremendous need to deploy this solution to higher frequencies, typically 15MHz and above, mainly for brain functional ultrasound imaging investigation.