A novel acoustic design for dual frequency transducers resulting in separate bandpass for color flow mapping (CFM)

Current transducers used in medical ultrasound imaging generally use a single bandpass for both echo-amplitude imaging and color flow mapping (CFM). A novel acoustic design is presented here which provides an additional bandpass at half the frequency of the image bandpass within the same acoustic device, making it possible to improve significantly the Doppler sensitivity and range. An advanced finite element method is used to analyze the behavior of this new multilayer acoustic structure. Several devices have been realized at 500 kHz for sonar application and at 5 MHz for medical application. The transducer realized for medical application features a narrow band (21% relative bandwidth) for Doppler at 2.4 MHz and a broad band (36% relative bandwidth) for echo-amplitude imaging at 4.6 MHz. Experimental results show a good agreement with finite element computation and demonstrate the advantage of this new acoustic design over conventional transducers