Ultrasound contrast agents and their use in urogenital radiology: status and prospects.

Ultrasound contrast agents (USCAs) for intravenous use are usually microbubbles with a mean diameter less than that of a red blood corpuscle and filled with gas. The USCAs may improve information about tissue characteristics and physiology by enhancing B-mode imaging, all Doppler modalities and by means of contrast-specific imaging, e.g. harmonic and stimulated acoustic imaging. Results from preclinical experiments have been promising, and several of these have been reproduced in clinical studies. This includes improved evaluation of renal vasculature and parenchyma, assessment of vesicoureteral reflux in children, assessment of tubal patency in women, and evaluation of prostate diseases and erectile dysfunction in men. Some of the physical limits of the ultrasound technology, as well as the operator-dependent factors, can probably never be overcome by the use of USCAs; however, the development of USCAs is now about to provide uroradiologists with potentially efficacious products for the benefit of the patient.