Two dimensional arrays for real time volumetric and intracardiac imaging with simultaneous electrocardiogram

Abstract

The authors have previously described 2D arrays operating up to 7.0 MHz consisting of several thousand elements for transthoracic cardiac imaging and up to 200 elements for intracardiac imaging. Most recently, the authors have constructed a 10.0 MHz array that includes 120/spl times/120=14,400 elements for real time transthoracic volumetric imaging. The resulting bandwidth is 27% and the 50 Ohm insertion loss is -68 dB. Real time volumetric images in phantoms have been made. There is interest in developing catheter based intracardiac imaging systems to aid in the precise tracking of anatomical features and interventional devices for improved diagnoses and therapies. Potential clinical applications include guidance of cardiac electrophysiological mapping and ablation procedures, long term monitoring of ventricular volumes in intensive care units and guidance of cardiac revascularization procedures using laser and drug angiogenic agents. The authors have constructed catheter array transducers with ECG electrodes for collecting electrophysiological data simultaneously with their images. There are 5 ring electrodes and 1 tip electrode for each transducer. The transducers consist of a 13/spl times/11=143 element array operating at 5.0 MHz and fits into a 12 French catheter (OD=3.8 mm). The first transducer array design is for side scanning applications. The second transducer layout has been inclined to a 20/spl deg/ bevel to improve image acquisition. The -6 dB fractional bandwidths for the different arrays varied from 40% to 63%, and the 50 Ohm insertion loss for the transducers was approximately -64 dB. Both the transducers were constructed on a 6 layer flexible polyimide interconnect Real time phantom images and intracardiac volumetric images in animal models have been obtained using the Duke University real time volumetric imaging system, which is capable of generating multiple planes at any desired angle and depth within a pyramidal volume. The authors obtained in vivo images of the ventricles and atria as well as simultaneous acquisition of 3 bipolar intracardiac ECG signals. With the real time volumetric scanner, the authors also guided and monitored the RF ablation of an excised sheep left ventricle. Cross section and face on images show excellent contrast between ablated versus normal myocardium.