Chirped‐excitation contrast imaging

Abstract

Ultrasound contrast agent oscillation and echoes are investigated optically and acoustically following insonation with a high time‐frequency bandwidth pulse. Results of a numerical evaluation of the modified Rayleigh–Plesset equation are used to predict the dynamics of a microbubble and compared with experimental observations. Two confocally aligned transducers transmitting at 10 MHz and receiving at 5 MHz are used, and a chirp waveform is transmitted with −6‐dB bandwidth from 7.5 to 12.5 MHz. With a simple bandpass filter, subharmonic echo components can be detected using the return from a single pulse, as the power ratio of subharmonic components to fundamental components ranges up to −7 dB. A high‐speed camera system, which provides 2D frame images and streak images, is used in optical experiments. From the optical observations of a single microbubble, nonlinear oscillation, destruction, and radiation force are observed. For an initial diameter ranging from 1.5 to 5 μm, a maximum diameter below 8 μm is...