Contrast-enhanced ultrasound

Gramiak and Shah first introduced the technique of using contrast enhanced two-dimensional echocardiography in 1968.1,2 The first contrast agents used were 'free' microbubbles that were limited by their low persistence and efficacy. Since that time, the development of contrast agents has followed several methods.2,3 Aqueous solutions, colloidal suspensions, and emulsions were studied as possible candidates for contrast agents; however, their safety and efficacy were not compatible with ultrasound. Newer contrast agents are composed of stabilized microbubbles that offer adequate safety profiles and improved efficacy. Their properties approach that of the ideal contrast agent, which is nontoxic, injectable intravenously, able to pass through the capillary pulmonary bed, and stable enough to achieve enhancement for the duration of the examination.