The initial clinical evaluation of a transesophageal system with pulsed Doppler, continuous wave Doppler, and color flow imaging based on an annular array technology

The application of transesophageal echocardiography (TEE) offers access to a great deal of important clinical information regarding cardiovascular anatomy and physiology. Two applications which have not been reported and would appear to be of interest are continuous wave Doppler capabilities and the implementation of higher frequency transducers. A TEE system designed at the Institute of Biomedical Engineering in Trondheim, which is based on an annular array technology, offers these capabilities. We evaluated this instrument in the clinical setting in a series of 30 patients to test the probe function in terms of the tissue and flow imaging quality with a 7.5 MHz carrier frequency, and to report on the implementation of a continuous wave Doppler modality in a TEE probe. We found that the annular array method permitted the use of high frequency probes for tissue and flow imaging which resulted in excellent image resolution, and that shifting the carrier frequency of the transducer to a lower frequency permitted the optimization of the Doppler sensitivity. The continuous wave Doppler was used to measure abnormal blood flow velocities in excess of 5.0 m/s, and was particularly useful in the operating room as velocity measurements could be obtained without compromising the sterile field. The results of our evaluation indicate that high imaging frequencies and continuous wave Doppler can be applied by an annular array TEE transducer.