4K-3 A Combined Array for Localized Harmonic Imaging: A Simulation Study of Feasibility of Motion Detection

In this study, feasibility of different pulse-echo fields to detect ultrasound radiation force induced displacements in soft tissue have been investigated. We used a linear phased array that consisted of 128 geometrically focused elements having the focal depth of 40 mm. The vibration distributions caused by an amplitude-modulated radiation force field induced in a homogeneous soft tissue block by the focused ultrasound beam from the phased array were simulated. Then part of the array was used to emit ultrasound pulses to detect the tissue motion. Properties of the emitted pulses were considered at the geometric focal depth using 2-32 elements. The elements used in the pulse-echo mode were driven at frequencies 5.5 MHz or 7.7 MHz. The vibration distribution was pulse-echo imaged using 2-16 elements so that the place of the tracking elements in the transducer was moved across the centre axis of the transducer. The simulated echo signals were computed using FIELD II program and the cross-correlation of these rf-signals was used in the displacement analyze. The results indicate that the displacement amplitude and distribution can be detected using pulse-echo imaging. As a conclusion it was shown that it should be possible to use a linear phased array for both induction of the tissue motion and its detection