Hemodynamic Aspects of Vessel Wall Imaging: 4D Flow

Abstract

Magnetic resonance imaging (MRI) has become an important tool for the clinical evaluation of patients with vascular disease. Two-dimensional phase contrast MRI (2D PC-MRI) has become a routine part of standard-of-care MRI for the assessment of regional blood flow in the heart and vessels. More recently, time-resolved PC-MRI with velocity encoding along all three flow directions and three-dimensional (3D) anatomic coverage – 4D flow MRI – has been developed and applied for the evaluation of vascular hemodynamics throughout the human body. 4D flow MRI allows for the comprehensive evaluation of complex blood flow patterns by 3D blood flow visualization and flexible retrospective quantification of flow parameters as well as advanced hemodynamic metrics such as wall shear stress or pulse wave velocity. Recent technical developments, including the utilization of rapid imaging techniques, have made the application of 4D flow MRI in a clinical setting more feasible. A number of studies have demonstrated the potential of 4D flow MRI to provide an improved assessment of measures of vascular hemodynamics and their relationship to vessel wall remodeling which might aid in the diagnosis and therapeutic management of common vascular diseases such as vessel dilation, aneurysms, or atherosclerosis. The purpose of this review is to describe the methods used for 4D flow MRI acquisition, post-processing, and data analysis. In addition, the article provides an overview of the applications of 4D flow MRI for the assessment of hemodynamic aspects of vessel wall imaging in the head, neck, thorax, and peripheral vessels.