Mateusz Celmer

Bio: Mateusz Celmer is an academic researcher from Wrocław University of Technology. The author has contributed to research in topics: Ultrasonic sensor & Ultrasound Tomography. The author has an hindex of 5, co-authored 6 publications receiving 38 citations.

Research and Modeling of Mechanical Crosstalk in Linear Arrays of Ultrasonic Transducers

Abstract: Linear arrays of ultrasonic transducers are commonly used as ultrasonic probes in medical diagnostics for imaging the interior of a human body in vivo . The crosstalk phenomenon occurs during the operation of transducers in which electrical voltages and mechanical vibrations are transmitted to adjacent components. As a result of such additional excitation of the transducers in the array, the directivity characteristics of the aperture used changes, and consequently there is interference with proper operation of a given array and the emergence of distortions in the obtained ultrasound image that reduce its quality. This paper studies the manner of propagation of mechanical crosstalk in the designed model of a linear array of ultrasonic transducers on the basis of unwanted signals, which appeared on elementary piezoelectric transducers when power is supplied to the selected transducer in the array. The universal model of linear array of ultrasonic transducers, which has been developed, allowed the simulation of mechanical crosstalk, taking into account the cross-coupling phenomenon in all of its structure with the use of finite elements method (FEM) implemented in COMSOL Multiphysics software. The analysis of crosstalk signals showed that they consist of aggregated pulses propagating with different speeds and frequencies. This signifies the formation of different vibration modes transmitted simultaneously via different paths. The paper is an original approach which enables to identify different vibration modes and estimate their participation in the crosstalk signal and their ways of propagation. Conclusions from the research allow predicting specific design changes which are significant due to the minimization of mechanical crosstalk in linear arrays of ultrasonic transducers.

Crosstalk Effect in Medical Ultrasound Tomography Imaging

Abstract: Ultrasound tomography (UT) is a modern method of medical imaging that has been intensively developed recently to diagnose female breasts in vivo. This method makes it possible to acquire images in various ultrasound modalities simultaneously - both transmission and reflection ones, without any focusing. Therefore, the ultrasound intensity level when scanning individual coronal breast sections is relatively low. Data for reconstruction of images is obtained by means of a multi-element array of small piezoceramic transducers spaced evenly on the inner side of the ring surrounding the breast immersed in water. The main problem with such arrangements is the occurrence of crosstalk, which introduces specific errors to measurement data. Crosstalk is a result of a deficiency in electrical or mechanical isolation between array elements. Such errors lead to distortions in the reconstructed images. In the paper, the effect of crosstalk in the ultrasound tomography ring array was examined and analyzed. The influence of crosstalk on the reconstructed images of the breast structure was shown as well. Conducted studies enabled the detection of the sources and paths of crosstalk and, as a consequence, it allowed us to improve the design of the multi-element ultrasonic transducer ring array, and to reduce crosstalk.

The effect of crosstalk in a circular transducer array on ultrasound transmission tomography of breast

Abstract: Various types of undesirable crosstalk can occur in ultrasonic arrays consisting of a number of elementary piezoelectric transducers. Crosstalk is a result of deficiency in electrical or mechanical isolation between the array's elements. It is a function of proximity between piezoelectric transducers of the array or between connections. Small piezoceramic transducers tightly located inside of a circle (cylinder or sphere in 3-D systems) are used for in vivo ultrasound tomography imaging of breast tissue. This means that correct switching of transducers makes it possible to quickly acquire tomographic transmission and reflection data. A problem with such arrangements is the occurrence of crosstalk, which introduces specific errors to measurement data. Transmission and reflection tomographic images reconstructed based on ultrasonic measurements with crosstalk are distorted in a characteristic way. This work analyses the effect of crosstalk in a circular transducer array on ultrasound transmission tomography - especially, when used for examination of breast tissue.

Array Design of Piezoelectric Micromachined Ultrasonic Transducers With Low-Crosstalk and High-Emission Performance

Abstract: This article presents a resonant cavity-based array design for piezoelectric micromachined ultrasonic transducers (PMUTs). The cavity depth is designed to ensure that its open end achieves a considerably smaller acoustic impedance than the surrounding PMUT cells. The interference acoustic wave generated between every two adjacent PMUT cells at the near surface of the array will take an easy path down to the cavity bottom. As such, the crosstalk effect among different adjacent cells in the array can be largely reduced. An equivalent circuit model of the proposed array is established for its design and optimization. In addition, the solutions for circuit parameters in the electromechanical domain are analytically derived and verified via FEM simulations. Given the low crosstalk effect achieved by the proposed array design, the output sensitivity of the proposed PMUTs can be improved by 259% compared with the traditional PMUTs with a high distribution density of the same size. The cavity-based array design and its model can be used for further advanced PMUT cell structures in other arrays to improve their performance.

Three-dimensional free vibration analysis of triclinic piezoelectric hollow cylinder

Abstract: Triclinic materials are categorized as anisotropic elastic materials with no existence of a symmetry plane. To characterize such materials, 21 elastic constants are required. The previous studies have not investigated triclinic materials due to a high number of material constants considered in the modelling. This paper presents a closed-form 3D piezoelectric model to investigate the free vibration of an arbitrary thick triclinic piezoelectric hollow cylinder. The piezoelectric cylinder is assumed to be infinitely long and short circuit boundary conditions are applied at the inner and outer surfaces of the shell. The natural frequencies of the cylinder are calculated using the transfer matrix approach along with the state space method. The effects of different anisotropic piezoelectric properties including orthotropic, monoclinic, and triclinic materials on the dispersion curve of natural frequencies are studied. The numerical results show that if the value of the axial wave number, the circumferential wave number, or natural frequency increase the resonant frequency of triclinic material deviates from other anisotropic materials such as orthotropic. Finally the validity of the proposed model is confirmed by comparing with simplified cases studied in the literature.