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109 IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL, VOL 38. NO 2. MARCH 1991 High-speed Ultrasound Volumetric Imaging System- Part 11: Parallel Processing and Image Display Olaf T. von Ramm, Stephen W. Smith, and Henry G. Pavy, Jr. Abstract-A real-time volumetric ultrasound imaging system has been developed for medical diagnosis. The scanner produces images analo- gous to an optical camera or the human eye and supplies more infor- mation than conventional sonograms. Potential medical applications include improved anatomic visualization, tumor localization and better assessment of cardiac function. The system uses pulse-echo phased ar- ray principles to steer a 2-D array transducer of 289 elements in a pyramidal scan format. Parallel processing in the receive mode pro- duces 4992 scan lines at a rate of approximately 8 frames /s. Echo data for the scanned volume is presented on-line as projection images with depth perspective, stereoscopic pairs, or multiple tomographic images. I. INTRODUCTION NEW ultrasound imaging system has been developed that A uses a hand-held transducer, capable of rapidly scanning a volume and enabling the three-dimensional ( 3-D ) visualization of dynamic structures in real time. We will describe the design considerations and preliminary evaluation of this high-speed, on-line volumetric ultrasound imaging system that uses the principles of pulse-echo, phased array scanning with a two-di- mensional (2-D) array transducer. In Part I, [l] we discussed the principles of phased array beam steering in two dimensions to obtain a volumetric scan. We also described the design, fab- rication and evaluation of two dimensional array transducers for volumetric scanning. The most significant challenge to the development of the high- speed volumetric ultrasound imaging system is the limited data acquisition rate of pulse-echo ultrasound scanning. For typical depths of 15 cm in tissue for cardiac or abdominal scanning, the propagation velocity of ultrasound waves in tissue, i.e., = 1540 m/s, limits pulse-echo ultrasound to a pulse repetition frequency of = 5000 transmit pulses/s in order to avoid redun- dant echoes from overlapping pulses. In conventional high speed ultrasound cross-sectional imaging, the 5000 transmit pulses are typically allocated to fewer than 160 scan lines per B-mode im- age at a rate of 30 frames s. A high speed v?olumetric pulse- echo scan that utilizes a similar field of view in both elevation and azimuth would require that approximately 160 B-scans be obtained in the time of a single conventional sonogram, i.e., an increase in data acquisition rate by a factor of 160. One solution to this problem is thk technique of parallel re- ceive mode processing. In this method, multiple image scan Manuscript received April 4, 1990; revised August 6, 1990; accepted August 7, 1990. This work was supported in part by HHS Grant #37586 and in part by NSFIERC #CDR-8622201.
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This note was uploaded on 02/27/2008 for the course BME 536 taught by Professor Shung during the Fall '07 term at USC.

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