Time-domain ultrasonic blood flow estimation methods have recently rec
eived considerable attention because of their advantages over conventi
onal Doppler methods. Among them are that they may yield better spatia
l resolution and that methods based on frame-to-frame speckle tracking
do not require a knowledge of the angle between directions of blood f
low and the ultrasound beam. These methods, however, suffer from an in
trinsic problem of poor signal-to-noise ratio, since the echoes scatte
red back by blood are much weaker than those of the surrounding struct
ures. In addition, the maximal velocity that can be estimated by frame
-to-frame tracking via conventional ultrasonic scanners is limited by
the frame rate of the scanner. In this article, we will present experi
mental results to show that these problems may be alleviated by using
a high frame rate scanner in conjunction with the injection of an ultr
asonic contrast agent. In this study the contrast agent used was Albun
ex(R).