Injectable contrast agents in ultrasonography

Contrast agents have been used in ultrasonography for about 30 years, but the risk of toxicity and the inefficiency of certain agents has long limited their use. The recent development of well-tolerated agents which cross the pulmonary capillary barrier after peripheral intravenous injection has made the use of contrast agents possible in routine clinical practice. The half life of these agents is now measured in minutes. These agents increase Doppler signal intensity and, in certain cases, allow parenchymal enhancement in B mode. They have helped improve Doppler performance, in particular for studying small or deep vessels with minimal flow. Concomitant adaptation of equipment has led to the introduction of ultrasound sequential imaging and announces the development of indispensable tools specifically adapted to contrast agents. The advent of directed bio-distribution and the contribution of pharmacologically active agents widens the field of application of ultrasounds to echo-guided therapeutic imaging designed for selective in situ delivery of active substances such as anticoagulants and cytotoxic drugs. (authors)