Title

A DSP-based real-time optical Doppler tomography system beamforming study of a 10 x 128 1.75D ultrasound array

Date of Completion

January 2005

Keywords

Engineering, Biomedical|Engineering, Electronics and Electrical

Degree

Ph.D.

Abstract

Topic 1: Beamforming study of a 10x128-element, 1.75D ultrasound array. 1.75D arrays allow beam steering in elevation, which is valuable for three-dimensional (3D) imaging within a certain field of view. 3D imaging has important advantage in detecting and visualizing small lesions from multiple viewing angles. Tetrad Co. has manufactured a 1.75D array using the state-of-the-art technology. This array consists of 10 rows in elevation and 128 elements in azimuth, 1280 elements in total. We have constructed 1280-channel transmission (TX) circuitry, 1280-to-40 multiplexing (MUX) circuitry and 40-channel parallel receiving (RX) circuitry. In addition to the conventional ultrasound beamforming in azimuth direction, the elevation scanning and focusing can be performed and image quality can be improved. With the array and the electronics, 20° scanning in elevation is archived with acceptable grating lobe performance. An unequal-size element technique is introduced to further suppress the grating lobe in elevation by breaking the array periodicity. Numerical simulations and experiments demonstrate that this method has an optimal reception pattern. ^ Topic 2: A DSP-based real-time optical Doppler tomography system . Clinical application of Optical Doppler Tomography System (ODT) requires real-time data acquisition and signal processing. In this study, we present a real-time signal processing ODT unit based on a custom designed digital signal processing (DSP) module. The DSP is incorporated into a conventional ODT system using a grating-based scanning optical delay line. The newly developed flow velocity algorithms are integrated into the DSP and real-time data processing can be readily achieved. Phantom and animal experiments have been conducted to demonstrate the real-time imaging capability of this system. ^