ECHO CONTRAST AGENTS AND ULTRASOUND IN VASCULAR MEDICINE

Intravenously applied, transpulmonary echo contrast agents lead to imp roved detection of blood flow in arteries and veins due to enhancement of the Doppler signal by 20-25 dB. This echo enhancement improves the visualization of vessel sections that are otherwise difficult to exam ine due to postoperative oedema, scarring, obesity to deep vessel loca tion. Under these difficult exam conditions, the echo contrast agents help clarify a ''low flow, slow flow deep flow or no flow state''. For transpulmonary passage the bubble diameter has to be less than 8 mu m . Furthermore, the contrast agents allow the generation of densitometr ic wash-in and wash-out curves from the vessels and tissues aiding in the investigation of tissue perfusion. Echo contrast agents induce som e technical side effects that have to be known in order to avoid annoy ing diagnostic pitfalls: spectral bubble noise, colour blooming, acous tic shadowing and changes in doppler frequency shifts. The lung passin g echo contrast agents open new application fields in the investigatio n of blood flow.