Previous studies have revealed that hard-shelled submicron contrast agents exhibit large relative expansions and strong acoustical echoes that can be observed experimentally, and predicted by theoretical simulations. In this paper, we study harmonic imaging and pulse-pair imaging techniques designed to assist in the differentiation of these contrast agents from tissue. For harmonic imaging, we apply a high-sensitivity, narrowband strategy that differentiates the microbubble from tissue based on the generation of strong harmonic echoes. For pulse-pair imaging, we apply high spatial resolution, wideband strategies using phase inversion, which relies on the frequency differences observed in response to phase-inverted pulses, and signal subtraction, which takes advantage of the amplitude differences in response to identical pulses. The bubble-to-phantom signal amplitude ratio in the absence of motion approaches 20 dB using phase inversion and 30 dB using signal subtraction; both techniques are robust for up to 50 μm of simulated motion. With, the experience gained in these studies, we hope to advance the development of multi-pulse or shaped-pulse techniques that are optimized for specific clinical applications.
|Original language||English (US)|
|Number of pages||9|
|Journal||IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control|
|State||Published - Mar 2004|
ASJC Scopus subject areas
- Electrical and Electronic Engineering
- Acoustics and Ultrasonics