Ultrasonic imaging using a 5-MHz multilayer/single-layer hybrid array for increased signal-to-noise ratio

Abstract

Conventional diagnostic ultrasound scanners are bulky and require significant amounts of electrical power during operation. Reducing the size, weight, and consumption of electrical power is made easier through the use of highly integrated compact transmit and receive electronics that may be incorporated in the transducer handle. This necessitates the use of low voltage transmitters and low power receive preamplifiers. Conventional scanners typically use approximately 100-V pulses during transmit; therefore, decreasing the transmit voltage to 15 V decreases the transmit sensitivity. Conventional receive electronics that are located at the scanner degrade the received signal-to-noise ratio (SNR) because the array element cannot efficiently drive the coaxial cable. Transmit sensitivity and received SNR can be radically improved using a multilayer/single-layer hybrid array making integration of electronics into the transducer handle more feasible. In this paper, we discuss the design, fabrication, and testing of a 5-MHz hybrid linear array. The hybrid array included 16 multilayer transmit elements (10 Omega impedance) and 24 single-layer receive elements at a half wavelength element pitch. Low voltage transmitters with an output resistance of 7 Omega and high impedance JFET preamplifiers using 15 V for biasing were located adjacent to the hybrid array in the transducer handle. The transmit sensitivity and received SNR of the hybrid array were compared with a conventional array using 50-Omega transmitters and receive preamplifiers at the scanner. The transmit sensitivity improved by 12.8 dB, and the received SNR improved by 7.8 dB, yielding an overall improvement of 20.6 dB, which compared well with predictions from the KLM model. Images of phantoms and in vivo images of the kidney obtained with the Siemens Model 1200 phased array system showed the increased SNR using the hybrid array. Estimates of penetration in tissue mimicking phantoms (alpha=0.5 dB/(cm MHz)) improved by 7 cm compared with the control.

Vector Doppler: spatial sampling analysis and presentation techniques for real time systems

“…This is in principle possible with a 2-D transducers array with multiple and independent electronic beamsteering systems; unfortunately this probe is not yet common in commercial echographs, though some solutions have been proposed in the literature. 11 However, the interest for 3-D imaging is still growing despite the technological difficulties and economic constraints for the fabrication of a 2-D or 1.5-D array integrated together with their interface electronics. 12 Regarding point 2, the assessment of the vector Doppler accuracy was carried out by several research groups that have employed different laboratory flow phantoms to test their Doppler systems.…”

Imaging arrays with improved transmit power capability

“…Work in this area has been reported for a variety of array configurations, materials, and processing methods [24]–[34]. Processing methods include cofiring of thick films [25], similar to the processing used for multilayer capacitors.…”

Waveguide piezoelectric micromachined ultrasonic transducer array for short-range pulse-echo imaging

“…1,2 Conventional ultrasonic transducers are made from bulk piezoelectric ceramic, which is expensive to machine into the high fill-factor 2D arrays needed for 3D imaging and makes individual pixel addressing difficult. In contrast, micromachined UTs (MUTs) have the advantages of increased bandwidth, low manufacturing cost, and the possibility to create 2D arrays that can be directly integrated with supporting electronics.…”