Pulse inversion Doppler for blood flow detection in the macro- and microcirculation

Current techniques for imaging ultrasound contrast agents make no distinction between low velocity microbubbles in the microcirculation and higher velocity microbubbles in the larger vasculature. A combination of RF and Doppler filtering on a low-MI pulse inversion acquisition is presented that differentiates low velocity microbubbles, perfusion, from the higher velocity microbubbles in larger vessels. Both fundamental and harmonic Doppler signals from microbubbles are compared against conventional color Doppler signals. Due to the lower transmit amplitude and enhanced backscatter from microbubbles, the signal to clutter ratios for both the fundamental (-11 dB) and harmonic (-4 dB) vascular flow signals were greater than conventional power Doppler (-51 dB) without contrast agent. Clinical results demonstrated the feasibility and potential utility of displaying in real-time both perfusion and vascular flow using ultrasound contrast agents.