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We developed prototype real-time 3-D intracardiac echocardiography catheters with integrated micromotors, allowing internal oscillation of a low-profile 64-element, 6.2-MHz phased-array transducer in the elevation direction. Components were designed to facilitate rotation of the array, including a low-torque flexible transducer interconnect and miniature fixtures for the transducer and micromotor. The catheter tip prototypes were integrated with two-way deflectable 10-Fr catheters and used in in vivo animal testing at multiple facilities. The 4-D ICE catheters were capable of imaging a 90° azimuth by up to 180° elevation field of view. Volume rates ranged from 1 vol/sec (180° elevation) to approximately 10 vol/sec (60° elevation). We successfully imaged electrophysiology catheters, atrial septal puncture procedures, and detailed cardiac anatomy. The elevation oscillation enabled 3-D visualization of devices and anatomy, providing new clinical information and perspective not possible with current 2-D imaging catheters.

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.