Abstract
Harmonic imaging is a prosperous technique to obtain a high quality ultrasonic image using harmonics in echoes from microbubbles, i.e., the collapse of microbubbles and subsequent harmonic emission are used for some imaging techniques, such as flash echo imaging. The mechanism of subharmonic generation is not figured out enough however it is considered that there are some relationships between the resonance and collapse of microbubble. On the other hand, subharmonic in echoes from microbubbles is expected to obtain higher contrast between tissue and blood flow than conventional harmonic imaging because it can be hardly detected from tissue. We observed echo signals and images of microbubbles through a microscope simultaneously and investigated the relationship between time-variation of each harmonics component and bubble's behavior. Our results showed clear inverse correlation between decrease of number of bubbles and subharmonic generation.
