Amauri Amorin Assef

A programmable FPGA-based 8-channel arbitrary waveform generator for medical ultrasound research activities

In modern ultrasound imaging systems, digital transmit beamformer module typically generates accurate control of the amplitude of individual elements in a multielement array probe, as well as of the time delays and phase between them, to enable the acoustic beam to be focused and/or steered electronically. However, these systems do not provide the ultrasound researchers access to transmit front-end module. This paper presents the development of a digital transmit beamformer system for generating simultaneous arbitrary waveforms, specifically designed for research purposes. The proposed architecture has 8 independent excitation channels and uses an FPGA (Field Programmable Gated Array) device for electronic steering and focusing of ultrasound beam. The system allows operation in pulse-echo mode, with pulse repetition rate of excitation from 62.5 Hz to 8 kHz, center frequency from 500 kHz to 20 MHz, excitation voltage over 100 Vpp, and individual control of amplitude apodization, phase angle and time delay trigger. Experimental results show that this technique is suitable for generating the excitation waveforms needed for medical ultrasound imaging researches.

Design of a 128-channel FPGA-based ultrasound imaging beamformer for research activities

Medical ultrasound scanners are amongst the most sophisticated signal processing machines in use today. To support the complex analog and digital functions, multiple customized application-specific integrated circuits (ASIC) are typically used for the front-end and back-end processing, with limited programmability. Even with the recent advances in electronic technology, most of these systems do not provide the ultrasound researchers to have access to raw ultrasound radio-frequency (RF) data and several other important transmission and reception functions, which are available only to systems engineers. In this paper, we present the design and progresses of a 128-channel programmable, reconfigurable and modular FPGA-based ultrasound beamformer system specifically designed for medical imaging research. The transmitter beamformer can excite simultaneously 128-channel with arbitrary waveform, with individual enable control, amplitude apodization, phase angle and time delay for dynamic focusing on transmission. The receiver beamformer can handle simultaneous 128-channels acquisition with programmable sampling rate up to 50 MHz and 12-bit resolution. The proposed platform allows connection to linear and convex transducers array, up to 256 elements, or phased array transducers, up to 128 elements, and center frequency between 500 kHz and 20 MHz.

Eigenspace generalized sidelobe canceller combined with SNR dependent coherence factor for plane wave imaging

BackgroundThe eigenspace generalized sidelobe canceller (EGSC) beamformer combined with a signal-to-noise ratio (SNR) dependent coherence factor (CF) is suggested for coherent plane wave compounding (PW) imaging. Conventional CF based methods such as generalized CF and subarray CF can improve the image quality, however, they are not suitable for low SNR. On the other hand, the EGSC CF based approach can introduce improvements in image quality, however, in PW imaging is susceptible to suffer from degradation due to low SNR which leads to a poor image quality. To overcome this limitation, the SNR dependent CF method is suggested for application in such situations due to its ability to control the SNR levels.MethodsThe Field II and the Verasonics ultrasound imaging system with a L11-4v array transducer with a contrast resolution phantom were used to capture the plane wave sequences of simulation and experimental data, respectively. The performance evaluation using full width at half maximum (FWHM), contrast (CR and CNR) and the speckle statistics by using the signal to noise ratio (SNR) complemented by the Rayleigh distribution analysis was performed. In order to evaluate the performance of the

Beamformer de transmissão multicanal de forma de onda arbitrária para atividades de pesquisa experimental do ultrassom

\text {EGSC}_{3}

Joint Adaptive Beamforming to Enhance Noise Suppression for Medical Ultrasound Imaging

EGSC3 (the SNR CF) beamformer, the comparison is done with particular importance to other CF-based approaches such as

Initial experiments of a 128-channel FPGA and PC-based ultrasound imaging system for teaching and research activities

\text {EGSC}_{1}