| Abstract [eng] |
1. Introduction. Ultrasound imaging is a wide research field, covering areas from wave propagation physics, sensors and front-end electronics to image reconstruction algorithms and software. All these topics are highly related, and it is very common that a novelty in one of them leads to advances in others. It is, indeed, a multidisciplinary field, which gives the opportunity for sharing knowledge and experience between different scientific and technical disciplines, such as physics, materials science, electronics, programming, etc. A typical ultrasound imaging system is composed of a set of sensors which are excited to generate an acoustic wave in the medium of interest and record the interaction of that wave with matter. This interaction can be based on different physical principles such as scattering, dispersion, absorption, radiation force, etc., and different propagation modes such as bulk, surface or Lamb waves, giving rise to very different types of sensors, imaging modes and techniques. A second key component of an ultrasound system is the front-end electronics, which should be able to independently excite the transducers (usually a large number of them), as well as condition and digitalize the signals received from the medium. Once in the digital domain, the electronic front end is responsible for implementing the beamforming process, which is needed to obtain an image from the raw input data. The requirements for this stage are strongly dependent on the type and configuration of the sensors, the inspected medium’s characteristics, the imaging method used and the real-time demands of the application. Finally, high-level algorithms are usually implemented to display and analyze the obtained images, a topic in which deep learning methods have acquired great relevance in recent times. This Special Issue entitled Ultrasonic Imaging and Sensors compiles 13 high-quality papers covering most of the research topics in this field. New sensors are proposed, both for direct contact and airborne applications and very different fields, such as medical imaging, concrete structures, molding manufacturing, wind turbines and agriculture, as are new means for testing their integrity. Front-end analog electronics for efficient sensor excitation is also addressed, as well as the optimized design of digital processing architectures for 2D arrays. Furthermore, new imaging methods are presented for improving image quality and inspection velocity, as well as new approaches for image generation and analysis based on deep learning techniques. A classification and short review of the papers in this Special Issue follow. |
