Contrast enhanced and Doppler ultrasonography in the characterization of the microcirculation. Expectancies and performances.

Normal and pathological vascularization can be examined using imaging methods. The use of contrast agents (CA), tracers or markers within the bloodstream, has gained more and more applications in the last years. The dynamics of the CA passing through a region of interest is directly correlated with the morphological and functional characteristics of the bloodstream in that particular area. Doppler ultrasonography provides information only regarding the flow within large vessels, the method having limited spatial resolution and sensitivity in the assessment of the capillary flow. Contrast-enhanced ultrasonography (CEUS) enables the detection of very slow blood flow or stagnating blood in vessels measuring as little as 40 microns. This feature is extremely valuable in the characterization of a circulatory bed and for the evaluation of the tumoral angiogenesis process. CEUS may be used both for diagnosis and for the assessment of treatment efficiency. Further on various aspects regarding this method, its advantages and limitations and arguments for its systematic use in oncology, will be presented in this review.