DYNAMIC IMAGING OF THE DOG HEART FROM THE ESOPHAGUS USING ULTRASOUND

NEAL EDWARD FEARNOT, Purdue University

Abstract

The purpose of this research was to obtain a new ultrasonic view of the heart using the esophageal approach. More specifically it was to propose, design and build an esophageal scanner, to evaluate its performance, and to determine the clinical potential of the esophageal images. The research therefore encompasses the development of both a new device and a new method of imaging the heart. The new transesophageal ultrasonic sector scanner produces high quality, real-time images of the major cardiac structures. The device consists of an esophageal probe with rotating transducers, electronic circuitry to produce the desired image formats, and video processing circuitry to improve the quality of the image. The esophageal probe consists of four 5-MHz PZT-5 piezoelements of 6.35 mm diameter mounted at 90-degree centers on a shaft that rotates at 900 rpm. Optical position sensing is used to reduce the transducer error to less than one degree. The piezoelements are pulsed at a 5 kHz rate and the echoes are processed electronically. Sixty images per second are displayed in an 83-degree sector on the gray scale CRT and recorded on standard videotape for review. By interactive positioning of the esophageal probe, heart ventricles, atria, and valves can be visualized and their dynamics can be studied. In addition to the sector display format, A-mode and M-mode display formats are produced. The performance of the scanner was measured and is reported herein. The dog was chosen as a cardiovascular model for this research. Images were obtained from anesthetized dogs to exhibit the basic properties of transesophageal imaging. Eight anatomical cross sections of the canine heart at one-centimeter intervals measured from the apex of the heart were prepared. Images, obtained in these planes, were compared with the cross sections. Basic cardiac structures visible in the images are described. Contrast media was injected to examine wall movement and blood flow through the cardiac system. Time-sequenced images throughout the cardiac cycle are presented. We have shown the feasibility of the transesophageal approach. High quality images of major cardiac structures are obtained using this method. The restrictions, encountered when imaging from the chest, are overcome by imaging from the esophagus, and therefore, an unrestricted view of the heart is available.

Degree

Ph.D.

Subject Area

Biomedical research

COinS