[Ultrasound contrast agents--newly developed agents and their clinical utility]

Recently many ultrasound contrast agents have been developed. Vascular and parenchymal enhancement of the organs such as liver and myocardium is obtained by intravenous injection of microbubble agents. They can survive after recirculation through the pulmonary capillary beds and under changes in vascular pressure. Several modalities of ultrasound imaging have been developed for effective enhancement. The harmonic imaging system is the most effective to depict contrast enhancement because of subtraction effect using retrieval of harmonic components from interaction microbubbles and ultrasound transmission. This is originated from resonance and destruction of microbubbles under ultrasound exposure.