| Intracardiac echocardiography (ICE) is a minimally invasive imaging technique in which a miniaturized ultrasound transducer is mounted in the tip of a catheter, enabling image acquisition from within the heart. To date, many applications of ICE involve the guidance of cardiac interventional procedures, such as ablation treatment of atrial fibrillation, guidance of atrial septal puncture. Current commercially available ICE systems offer monoplanar imaging, i.e. imaging in a 2-D plane, acquired using a mechanically rotating single transducer element, or with a linear phased array of elements. With these 2-D imaging configurations, it is often difficult to orient the imaging catheter in such a way that both the cardiac anatomy and interventional device are aligned in the same imaging plane.;The development of a real-time three-dimensional (RT3-D) ICE system addresses these shortfalls. This work describes the design, simulation, fabrication and testing of miniaturized, 2-D phased array transducers mounted in the tips of catheters to enable RT3-D ICE. The transducers are constructed on multi-layer polyimide interconnect circuits and incorporate high density cabling interconnections within the catheter lumen. Advances in interconnection and cabling technology are described which have enabled up to a 5X increase in channel density over previous designs. These advances have facilitated both the miniaturization of the devices and image quality improvements necessary for the devices to become clinically useful. Several designs are discussed, including a 9 Fr (3.0 mm O.D.), 70 element 7 MHz side-viewing 2-D catheter array on a silicon substrate, and a 7 Fr (2.3 mm O.D.), 112 element 5 MHz side-viewing 2-D catheter array. RT3-D images of cardiac anatomy are presented, obtained during in vitro and in vivo studies with a sheep model.;The design, fabrication and testing of forward-viewing RT3-D ICE probes is also described. The forward-viewing probes contain an additional working lumen through which interventional devices are delivered. The forward viewing probes contain 112 elements operating at 5 MHz. Combining the imaging catheter with a working lumen in a single device may simplify cardiac interventional procedures by allowing clinicians to easily visualize cardiac structures and simultaneously direct interventional tools in a RT3-D image. |
