Two Dimensional Arrays for 3-D Ultrasound Imaging Stephen W. Smith, Warren Lee, Edward D. Light, Jesse T. Yen, Patrick Wolf, Salim Idriss Department of Biomedical Engineering Duke University, Durham, NC 27708 Abstract . Phased array ultrasound transducers have been fabricated in our laboratories at Duke University since 1970. In 1986, we began the development of 2-D arrays with a 20 x 20 element Mills cross array including 64 active channels operating at 1 MHz which produced the first real time 3-D ultrasound images. In our more recent arrays we have progressed to 108 x 108 = 11,664 elements in a series of transducers operating from 2.5 - 10 MHz. These were used in a commercial version of our Duke 3-D system developed by Volumetrics Medical Imaging for cardiac applications. The system scans a 65 0 3-D pyramid at up to 60 volumes/sec and features five simultaneous slice images at any desired angle and depth as well as real time 3-D rendering, 3- D pulsed and color flow Doppler. We have also modified this scanner to produce the first real time 3- D rectilinear and curvilinear images using arrays of 256 x 256 = 65,536 elements operating at 5 MHz for vascular and small parts applications. Finally, we have developed catheter 2-D arrays for intra-cardiac 3-D ultrasound including 112 channels in a 2.2 mm lumen (7 French) operating at 5-7 MHz. In animal studies, these transducers have been applied to the guidance of cardiac interventional procedures including RF ablation, ECG mapping, surgical biopsy and atrial septal puncture. I. INTRODUCTION Approximately three decades ago, the field of medical diagnosis was forever changed with the advent and clinical success of real time B-mode ultrasound. In a period of a few years technology was developed for a variety of scanners including linear arrays, mechanical sector, sectored phased arrays, and curvilinear arrays with applications in virtually every medical specialty. More recently B- mode ultrasound was combined with endoscopic and catheter technology yielding intra-luminal and intra- vascular applications. Now thirty years later, in an analogous manner to the development of real time B- mode, real time 3-D ultrasound imaging is emerging using mechanical steering as well as phased array, linear and curvilinear array scanning. Figure 1 compares the traditional 2-D scanning methods (Figs. 1A-C) versus their 3-D analogues (Figs 1D-F). Figure 1. Schematic showing traditional 2D scanning array transducers and their 3D analogs: A, sectored phased array; B, linear sequential; C, curvilenear array; D, pyramidal scan; E, rectilnear scan and F, curvilinear scan. The evidence for the enhanced clinical value of 3-D ultrasound imaging is strongest in the field of obstetrics where the 3-D scan is typically produced A B C D E F