Ultrasonic phased-array scanner with digital echo synthesis for Doppler echocardiography

Abstract

For the purpose of the quantitative assessment of subtle disease processes in the cardiovascular system an electronically steered sector scanner that combines echographic imaging and Doppler blood velocity measurements has been developed. The integrated operation of a fast Fourier transform (FFT) Doppler signal processor for the simultaneous blood velocity evaluation of 64 individual gates is among the specific design goals. The instrument incorporates an unusually high degree of digital signal processing, which allows for high integration density, easy manufacturing and high reliability in future designs. The complex Doppler spectra are determined for each of the 64 Doppler gates in real time, and the subsequent computation of the first moment provides a reliable estimate of the mean blood flow velocities at the respective locations. The instantaneous velocity profile along the Doppler beam is displayed together with the calculated volume flow rate and a range-selected complete frequency spectrum. Results of both in vitro and in vivo tests indicate that in the future, a higher degree of digital signal processing could be implemented in complex ultrasonic systems.

VLSI circuits for adaptive digital beamforming in ultrasound imaging

“…However, since the FIFO and adder sizes increase dramatically with the number array of elements, the scheme is not very feasible for implementation at the board level or in VLSI. Alternatively, the samples can be added recursively using partial sum registers [6]. But this technique is not particularly practical, because of the adder speed requirement.…”

“…Thus, it results in an annoying artifact called Moire pattern which is a well-defined pattern of holes in the image corresponding to the unaddressed pixels. Artifacts can be decreased by using two dimensional interpolation techniques [ 131, [6]. This significantly increases the computational cost of the scan conversion process.…”

“…Recent developments in digital integrated circuit technology motivates research on advanced digital beamforming techniques based on special purpose VLSI circuits. [3]- [6]. In the design of such circuits, it is important to examine the beamforming algorithm performance, which critically affects image resolution [7], and the feasibility of algorithm for VLSI implementation [8].…”

A VLSI receive beamformer for digital ultrasound imaging

“…and adder sizes dramatically increase with the number array of elements, the scheme is not very feasible for implementation at the board level or in VLSI. Alternatively, the samples can be added recursively using partial sum registers [7]. But this technique is not particularly easy due to the requirement of very fast additions.…”

“…Due to recent developments in integrated circuit technology, real-time digital receive beamforming techniques become attractive ( Fig. 1) [5,6,7,8,9].…”