Ultrasound contrast agents (USCAs) are now becoming commercially available. During the past decade, both tolerance and efficacy of microbubble USCAs increased in conjunction with the ultrasound instrumentation. Specific contrast image sequences have been developed to take advantage of the specific microbubble ultrasonic properties. USCAs are well tolerated and do not exhibit allergic reactions or renal toxicity. USCAs increase the Doppler signal intensity from vessels of deep location, small caliber, or in case of reduced and/or slow blood flow. They improve the detection of vessels with limited access due to anatomic limitations. Under certain circumstances they can alter the texture to provide tissue perfusion information. In peripheral artery disease, USCAs help identify subocclusive lesions and grade stenoses. In transcranial Doppler, they reduce the technical failure rate. In renal Doppler ultrasonography, they improve the detection and recording of the renal arteries. USCA increase the role of color Doppler sonography as the primary modality in the screening of renovascular hypertension. Contrast-enhanced color Doppler US provides additional information from cortical blood supply. In liver USCAs improve the visualization of the blood flow. In liver transplants, they improve the detection of anastomotic vessel occlusive disorders. Some studies also investigated the potentials of USCA in detecting and characterizing liver, renal, breast and prostate tumors. Quantification of USCA effect is a preliminary step towards functional imaging.
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