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.