Corrias Giuseppe, Cocco Daniele, Suri Jasjit S, Meloni Luigi, Cademartiri Filippo, Saba Luca
Department of Radiology, University of Cagliari, Cagliari, Italy.
Department of Cardiology, University of Cagliari, Cagliari, Italy.
Cardiovasc Diagn Ther. 2020 Aug;10(4):1140-1149. doi: 10.21037/cdt.2020.02.08.
Four-dimensional (4D) flow sequences are an innovative type of MR sequences based upon phase contrast (PC) sequences which are a type of application of Angio-MRI together with the Time of Flight (TOF) sequences and Contrast-Enhanced Magnetic Resonance Acquisition (CE-MRA). They share the basic principles of PC, but unlike PC sequences, 4D flow has velocity encoding along all three flow directions and three-dimensional (3D) anatomic coverage. They guarantee the analysis of flow with multiplanarity on a post-processing level, which is a unique feature among MR sequences. Furthermore, this technique provides a completely new level to the flow analysis as it allows measurements in never studied districts such as intracranial applications or some parts of the heart never studied with echo-color-doppler, which is its sonographic equivalent. Furthermore, this technique provides a completely new level to the flow analysis as it allows accurate measurement of the flows in different districts (e.g., intracranial, cardiac) that are usually studied with echo-color-doppler, which is its sonographic equivalent. Of note, the technique has proved to be affected by less inter and intra-observer variability in several application. 4D-flow basic principles, advantages, limitations, common pitfalls and artefacts are described. This review will outline the basis of the formation of PC image, the construction of a 4D-flow and the huge impact the technique is having on the cardiovascular non-invasive examination. It will be then studied how this technique has had a huge impact on cardiovascular examinations especially on a central heart level.
四维（4D）血流序列是一种基于相位对比（PC）序列的创新型磁共振序列，PC序列是血管磁共振成像的一种应用类型，与飞行时间（TOF）序列和对比增强磁共振血管造影（CE-MRA）一样。它们共享PC的基本原理，但与PC序列不同的是，4D血流在所有三个血流方向上都有速度编码以及三维（3D）解剖覆盖范围。它们保证了在处理后层面上进行多平面血流分析，这是磁共振序列中独有的特征。此外，这项技术为血流分析提供了一个全新的水平，因为它允许在从未研究过的区域进行测量，如颅内应用或心脏某些从未用超声彩色多普勒研究过的部分，超声彩色多普勒是其超声等效技术。此外，这项技术为血流分析提供了一个全新的水平，因为它允许准确测量通常用超声彩色多普勒研究的不同区域（如颅内、心脏）的血流，超声彩色多普勒是其超声等效技术。值得注意的是，在一些应用中，该技术已被证明受观察者间和观察者内变异性的影响较小。本文描述了4D血流的基本原理、优点、局限性、常见陷阱和伪影。本综述将概述PC图像的形成基础、4D血流的构建以及该技术对心血管无创检查的巨大影响。然后将研究该技术如何对心血管检查，尤其是对心脏中心层面产生了巨大影响。
