The value of ultrasound contrast agents (USCA) in clinical practice depends on the pharmacokinetics, the signal processing, and the contrast-specific imaging modalities. USCA are exogenous non-toxic substances smaller than red blood cells,which after intravenous administration must be stable enough to pass through the pulmonary capillary bed and enter the blood pool producing the necessary contrast enhancement for the duration of the examination. Recently, second-generation agents, such as SonoVue (Bracco Imaging SpA,Milan,Italy),have been introduced into the market. These agents,taking advantage of the stability of their microbubbles,withstand the acoustic pressure of insonation much better than previous USCA,resulting in an increased half-life of the agent and thus in a prolonged diagnostic window. These agents are blood pool agents that remain in the intravascular compartment and do not leak into the organ tissue. Therefore,they are used to – crease the Doppler signal amplitude during their dynamic vascular phase. Concomitant with the improvement of contrast agents,d- ferent contrast-specific imaging modalities have been developed which,used in combination with USCA and a low mechanical – dex (MI),allow continuous real-time grey-scale imaging. These – cent technical improvements have opened new possibilities in the use of USCA in a variety of indications,as shown in the contributions contained in this book. In the following chapters,some of the most distinguished users of second-generation USCA will share their knowledge and experience. The first contributor is Dr. Thomas Albrecht,Department of – diology, University Hospital of Berlin, Germany.