1. A method for detection and imaging of ultrasound contrast agent in a region of soft tissue, where, at least one ultrasound pulse containing frequency components in separated low and high frequency bands, is transmitted toward said region, the time signals of said low and high frequency components are overlapping in time, so that said transmitted low frequency components are used to manipulate the acoustic scattering properties of the contrast agent for the incident frequency components in said high frequency band, where the scattered signal from said transmitted high frequency components is used for ultrasound contrast image reconstruction of said region.