Big steps in advances of doppler ultrasound

Abstract

Doppler Ultrasound is clinically important for evaluation of various hepatic vascular disease as well as hepatic vessel evaluation after liver transplantation. However, there are some limitations in conventional Doppler methods as follows: 1) time consuming and labor intensive and 2) limited slow flow sensitivity. There are two recently advanced Doppler signal-processing methods (i.e., UltraFast and superb microvascular imaging), which overcome those limitations. UltraFast Doppler ultrasound, which emerged with the advent of massive parallel computing (or processing) capabilities, transmits several tilted plane waves into the medium and coherently sums the backscattered echoes to reconstruct US images, leading to a marked increase in the frame rate, while conventional ultrasound imaging involves sequential medium insonification via focused beams and successive image reconstruction. A stored UltraFast Doppler clip contains information on both spectral analysis and color-coded flow imaging and could be retrospectively evaluated quantitative analysis, because UltraFast ultrasound has high spatio-temporal resolution. Superb microvascular imaging (SMI, Cannon Medical Systems Corporation, Tochigi, Japan) uses a different kind of adaptive wall filter, which could minimize the flash artifact and increased sensitivity to slow flow and improve the signal detection of flow from small vessels. Therefore, in clinical practice, UltraFast Doppler can be performed by anyone. If the exam protocol such as acquisition of clip by less experienced sonographer and evaluation by retrospective wave reconstruction by specialist can be established, efficient work force management can be possible. Superb Microvascular imaging can distinguish very slow portal flow by portal hyper tension and so forth from thrombus. Thrombus can be evaluated with almost the same resolution as CT. The weak flow of a small hepatic artery hiding by vigorous flow of portal vein after liver transplantation can be also distinguished. In conclusion, smart application of recent advanced Doppler technique will help comprehensive assessment of hepatic vascular abnormalities.