A dual frequency ultrasonic probe for medical applications

摘要

A dual frequency probe using a multilayer ceramic is proposed fornsimultaneously obtaining a high resolution B mode and a high sensitivitynDoppler mode image. This ceramic consists of two layers in which thenpoling directions are opposite and the individual thicknesses arendifferent. It is possible to control the values of relativenelectromechanical coupling factors in the fundamental and the secondnharmonic by changing the thickness ratio. A thickness ratio of 1:0.7 wasndecided from computer simulation based on the Mason's model. Ansufficient resolution has been shown from the fact that the intima ofnthe carotid artery could be distinguished by an actually fabricatednprobe with dual frequencies of 3.75 and 7.5 MHz. Also, the sensitivitynof this probe in the Doppler mode at 5 cm depth from the surface hasnbeen improved as much as 5 dB over that of a conventional one