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Principles of Doppler ultrasound
Published in Joseph A. Zygmunt, Venous Ultrasound, 2020
Recently, some ultrasound manufacturers have started producing transducers using a newer technology called capacitive micromachined ultrasonic transducer (CMUT). These transducers no longer use the piezoelectric effect but instead utilize changes in capacitance to transmit and receive signals. Since these transducers are manufactured by bonding together machined silicon wafers, the cost is significantly lower than conventional transducers. Besides lower cost, there are many other benefits including the ability to make large and customized arrays, broad bandwidth, and easy integration with required supporting electronics. The biggest disadvantage to date has been decreased sensitivity, which has been improving with design modifications.
Transducers and beam forming
Published in Peter R Hoskins, Kevin Martin, Abigail Thrush, Diagnostic Ultrasound, 2019
Tony Whittingham, Kevin Martin
The basic CMUT element is similar in structure to a small drum, with a fixed base above which is a thin flexible membrane separated by a vacuum gap (Figure 3.11). The membrane and the fixed base contain electrodes which form a capacitor. When a steady bias voltage is applied between the electrodes, electrostatic attraction causes the flexible membrane to be drawn towards the base. The attraction is opposed by the elastic restoring force in the membrane. An alternating voltage applied between the electrodes causes the membrane to vibrate. This mechanism can be used to generate an ultrasound wave in a medium in acoustic contact with the membrane. In reception, movement of the membrane due to the pressure changes of the incoming wave causes changes in the capacitance of the device. Under a steady bias voltage, the changes in capacitance give rise to a corresponding electrical current into the device, whose amplitude is related to the bias voltage and the frequency of the wave. This current may be detected and processed as an ultrasound echo signal.
Portable High-Frequency Ultrasound Imaging System Design and Hardware Considerations
Published in Iniewski Krzysztof, Integrated Microsystems, 2017
Insoo Kim, Hyunsoo Kim, Flavio Griggio, Richard L. Tutwiler, Thomas N. Jackson, Susan Trolier-McKinstry, Kyusun Choi
During the past 20 years or so, many researchers have tried to produce miniaturized and integrated ultrasound imaging systems [4–10]. The reason is because integrating all electronic components into a single integrated circuit (IC) chip will afford a smaller system size, higher speed, and lower power consumption than building the system with discrete chipsets. The earliest ultrasound application-specific integrated circuit (ASIC) chips were reported by Black et al. and Hatfield et al. in 1994. The ASIC chips contained 16 channels of transmitters and current amplifiers with integrated transducers [4] and digital transmitters [5]. Since 2000, with the rapid development of mixed-signal IC design technology, closed-coupled ultrasound front-end electronics have emerged for high-frequency ultrasound imaging systems. Wygant et al. [6] developed a Capacitive Micromachined Ultrasound Transducer (CMUT) with closed-coupled electronics, which contain 16 receive–transmit channels. Johansson et al. [7] introduced a portable ultrasound system using a battery-operated voltage-boosting scheme. The Sonic Window, developed by Fuller et al. [8] in 2005, included one of the most integrated ultrasound front-end IC chip concepts to date. Developed for guiding needle and catheter insertion, biopsies, and other invasive procedures for which only a basic aid to diagnosis is necessary, the sonic window can also be used for C-mode ultrasound imaging.
Towards a novel small animal proton irradiation platform: the SIRMIO project
Published in Acta Oncologica, 2019
Katia Parodi, Walter Assmann, Claus Belka, Jonathan Bortfeldt, Dirk-André Clevert, George Dedes, Ronaldo Kalunga, Sonja Kundel, Neeraj Kurichiyanil, Paulina Lämmer, Julie Lascaud, Kirsten Lauber, Giulio Lovatti, Sebastian Meyer, Munetaka Nitta, Marco Pinto, Mohammad J. Safari, Katrin Schnürle, Jörg Schreiber, Peter G. Thirolf, Hans-Peter Wieser, Matthias Würl
Integration of ionoacoustics/US imaging entails the development of dedicated instrumentation able to handle the different frequency ranges of ionoacoustics (reception only) and US imaging (emission/reception). From the experiments performed so far, customized sensors based on Capacitive Micromachined Ultrasonic Transducers (CMUT) developed at the Department of Engineering Roma Tre University (Rome, Italy), along with dedicated low-noise amplifier electronics, have been identified as promising candidate for the development of bi-modality ultrasound systems for ionoacoustic/US co-registration [19]. Additional data acquired with special phantoms including tissue heterogeneities and microbubble ultrasound contrast agents are being analyzed to assess their influence on the ionoacoustic signal and to optimize the range verification accuracy, along with first tests of ionoacoustics/US co-registration.