SURF imaging for contrast agent detection.

A contrast agent detection method is presented that potentially can improve the diagnostic significance of ultrasound contrast agents. Second order ultrasound field (SURF) contrast imaging is achieved by processing the received signals from transmitted dual frequency band pulse complexes with overlapping high-frequency (HF) and low-frequency (LF) pulses. The transmitted HF pulses are used for image reconstruction, whereas the transmitted LF pulses are used to manipulate the scattering properties of the contrast agent. In the present paper, we discuss how SURF contrast imaging potentially can overcome problems and limitations encountered with available contrast agent detection methods, and we give a few initial examples of in vitro measurements. With SURF contrast imaging, the resonant properties of the contrast agent may be decoupled from the HF imaging pulses. This technique is thus especially interesting for imaging contrast bubbles above their resonance frequency. However, to obtain adequate specificity, it is typically necessary to estimate and correct for accumulative nonlinear effects in the forward wave propagation.