POWER DOPPLER SONOGRAPHY - CLINICAL-APPLICATIONS

Objective. Color Doppler imaging (CD) has had a great impact on ultras onography (US). This technique depicts local flow by encoding an estim ate of the mean Doppler frequency shift at a particular position in co lor. However, the choice of the mean frequency shift as the parameter for representing flow in color Doppler is somewhat arbitrary. Power Do ppler ultrasound is a technique that encodes the power in the Doppler signal in color. This parameter is fundamentally different from the me an frequency shift. The frequency is determined by the velocity of the red blood cells, while the power depends on the amount of blood prese nt. Providing an image of a different property of blood flow, power Do ppler has shown several key advantages over colour Doppler, including higher sensitivity to flow, better edge definition and depiction of co ntinuity of flow. In this paper we review the results of power Doppler clinical studies. Materials and Methods. All relevant information ava ilable in the literature on the potential clinical applications of thi s technique was revised to give a detailed survey. Results. The increa sed flow sensitivity and better vascular detailing of power Doppler ha ve been used to detect flow presence and characteristics in vessels th at are poorly imaged with conventional color Doppler. The improved dep iction of tissue vasculature has shown potential advantages, especiall y in some areas, such as the cortex of native kidneys and renal allogr afts, the prepuberal testis, the infant hip and the bowel wall,. in wh ich color Doppler is not sensitive enough to detect clinically importa nt, slow and poor flow in small vessels. In inflammatory conditions, p ower Doppler was valuable in depicting increased flow in vessels that are dilated because of inflammatory response. In this field, advantage s have been reported in acute cholecystitis and in inflammatory states of musculoskeletal tissues. The higher sensitivity to slow flow and t he improved detailing of the course of tortuous and irregular vessels made power Doppler a promising technique to image intratumoral vessels and, thereby, to ameliorate the accuracy of color Doppler in predicti ng the likelihood of benign versus malignant nature of nodules. Specif ic flow patterns, missed at color Doppler studies, have been indicated with power Doppler in some tumors of the liver and breast. In differe nt settings, power Doppler also permitted to monitor serial blood flow changes after therapy and to display them as color intensity, allowin g the observer to distinguish flow changes. Conclusion. Although the a ctual role of power Doppler in changing patient management has not bee n assessed yet, this technique can depict flow which was previously un detectable, and thus permits an easier and more confident diagnosis in body regions where the ultrasound signal is weak because blood vessel s are small. (C) 1998 Elsevier Science Ireland Ltd. All rights reserve d.