High-speed data acquisition in a diffraction tomography system employing large-scale toroidal arrays

This report describes the development of an experimental system for ultrasound computed tomography and its application to breast imaging. Details of the system design and methods of highspeed data acquisition are presented. The method uses low-power discrete frequency sound in the range of 0.3-1.2 MHz, two cylindrical arrays of 512 and 1024 PZT transducers, high spatial sampling of the wavefront, and unique diffraction tomographic reconstruction methods. One transducer at a time is activated and allowed to reach steady state at which point the remaining measure phase and amplitude of the ultrasound signal. A total of 64 MB of data are acquired in <1 s for the 512-element array and 128 MB in <3 s for the 1024 array. Several algorithms have been developed to produce the diffraction tomogram which is reconstructed as either a 512 x 512 or 1024 x 1024 matrix of the scattering potential of the object dependent on speed of sound and attenuation. The effects of aberration are greatly diminished by a hybrid iterative algorithm. To date, human images have been made of the female breast which show good depiction of glandular structures and differentiation of gland and fat, and the coronal format provides a novel of the entire breast in life-size display. The results demonstrate that the technique provides a unique quantitative ultrasound image with high resolution over a very large global field of view of the breast. The method shows promise for improved imaging of the breast. (C) 1997 John Wiley & Sons, Inc.