Subharmonic imaging with microbubble contrast agents: Initial results

The subharmonic emission from insonified contrast microbubbles was used to create a new imaging modality called Subharmonic Imaging. The subharmonic r esponse of contrast microbubbles to ultrasound pulses was first investigate d for determining adequate acoustic transmit parameters. Subharmonic A-line s and gray scale images were then obtained using a laboratory pulse-echo sy stem in vitro and a modified ultrasound scanner in vivo. Excellent suppress ion of all backscattered signals other than from contrast microbubbles was achieved for subharmonic A-lines in vitro while further optimization is req uired for in vivo gray scale subharmonic images.