Wideband harmonic imaging: A novel contrast ultrasound imaging technique

A novel ultrasonic imaging method, wideband harmonic imaging, for nonlinear imaging of microbubble contrast agents is evaluated. In wideband harmonic mode, two pulses of alternate phase are send out. The image is then process ed from the sum of both pulses, resulting in an image of nonlinear scattere rs such as microbubbles. A prototype ultrasound system, Siemens Elegra, was evaluated with in vitro investigations and animal trials, using convention al, harmonic and wideband harmonic settings with the galactose based ultras ound contrast agent Levovist. Wideband harmonic imaging offers superior sen sitivity for ultrasound contrast agents compared to conventional imaging an d harmonic imaging. At low transmit power settings (MI 0.1-0.5) the nonline ar response is already sufficient to generate a image of the blood pool dis tribution of Levovist in the rabbit kidney including the microvasculature, with clear delineation of vessels and perfused parenchyma. At high transmit amplitudes, nonlinear tissue response reduced the apparent image contrast between contrast agent and tissue. The results suggest that wideband harmon ic imaging is currently the most sensitive contrast imaging technique, main taining highest spatial resolution. This may add to image quality and offer new clinical potential for the use of ultrasound contrast agents such as L evovist.