New Method for Ultrasound Contrast Imaging Using Frequency-Modulated Transmission

Abstract

In diagnostic ultrasound imaging, microbubble-based contrast agents are currently used to enhance blood flow signals. The microbubbles in the blood vessels have various diameters and various resonant frequencies. Therefore, only some bubbles will be stimulated by a transmission pulse with a single frequency component. In this report, we propose a multiple-pulse transmission method with different frequencies to stimulate more microbubbles. We have confirmed both an increase in bubble echoes and the suppression of tissue echoes with this method. In phantom experiments, wideband bubble echoes were obtained using the proposed method, and the bubble-tissue ratio was improved by 8.3 dB as compared with the conventional second-harmonic method. In animal experiments, the tissue echoes were adequately suppressed as compared with conventional second-harmonic images.