Toroidal geometry: novel three-dimensional intracardiac imaging with a phased-array transducer

Recent advances in small, linear-array transducers have opened new avenues for three-dimensional image acquisition from an intracardiac approach. The purpose of this study was to introduce a novel method of image acquisition using toroidal geometry, explore its fidelity of reproduction of three-dimensional cardiac anatomy, and determine whether a whole-heart scan is achievable. Acquisition was accomplished through 360-degree incremental rotation of a rigid endoscope with a side-mounted ultrasound transducer. The procedure was first tested with the use of a gelatin model to define far-field slice resolution with 1.8-degree rotational increments. Comparison of three-dimensional scans of cardiac specimens with corresponding photographs confirmed that toroidal geometry can provide a high-quality display of structures from all sides. We conclude that whole-heart three-dimensional scanning from within the cardiac chambers is possible with toroidal geometry. The quality of depicted anatomy depends on transducer location within the heart, distance from the transducer, density of slices, and image resolution. The potential of intracardiac three-dimensional ultrasound imaging includes detailed spatial evaluation of cardiac morphology, determination of appropriate placement of investigative or therapeutic devices (catheters, closure devices, etc.), and assessment of cardiac function.