B-mode enhancement at phase-inversion US with air-based microbubble contrast agent: Initial experience in humans

Pulse- or phase-inversion ultrasonography (US) sums the signals returned fr om two 180 degrees ultrasound pulses. Linear scattering from tissue results in a signal void while nonlinear signals from microbubbles stand out. The technique was applied with a US contrast agent in 39 human subjects. B-mode enhancement of vessels and organ parenchyma was seen in all cases. Enhance ment occurred from flowing and stationary microbubbles. The flow-independen t enhancement of normal and abnormal tissue represents a major advance in c ontrast material-enhanced US with many potential applications especially in tumor imaging.