New insights in magnetic resonance imaging evaluation of aortic valve hemodynamics

主动脉瓣狭窄（AS）是指主动脉瓣的病理性狭窄。它是欧洲和北美最常见的心脏瓣膜病，也是仅次于全身性高血压和冠状动脉疾病的最常见的心血管疾病。目前，心导管检查和多普勒超声心动图是最常用的方法来确定主动脉瓣狭窄的严重程度。然而，心导管插入术具有显著的技术局限性，并且它是一种侵入性技术，可能使患者处于不必要的风险中，而多普勒超声心动图具有几个实际和理论局限性，限制了其在约20%的主动脉瓣狭窄患者中的适用性。在最近的一项体外研究中，我们开发了一种新的方法，使用粒子图像速度场（PIV），以确定主动脉瓣狭窄的严重程度从速度场。虽然非常有前途，但这种方法的适用性是有限的，因为PIV需要透明的结构在体内。然而，对于磁共振相位对比（MR PC），情况并非如此。事实上，MR PC是一种强大的非侵入性、非电离技术，能够研究通过人体心脏瓣膜的速度场。本研究的目的是，因此，在体外和体内的可行性和准确性，我们的新方法适用于MR PC测量的速度场。此外，我们将研究MR PC计算主动脉瓣狭窄下游湍流特性的能力。我们期望该项目的结果将对主动脉瓣狭窄严重程度的临床评价产生重大影响。

Aortic stenosis (AS) is defined as the pathological narrowing of the aortic valve. It is the most frequent valvular heart disease and the most frequent cardiovascular disease after systemic hypertension and coronary artery disease in Europe and North America. Currently, cardiac catheterization and Doppler echocardiography are the most frequently used methods for the determination of aortic stenosis severity. However, cardiac catheterization has significant technical limitations and it is an invasive technique that may place the patient at unnecessary risk while Doppler echocardiography has several practical and theoretical limitations that limit its applicability in around 20% of the patients with aortic stenosis. In a recent in vitro study, we developed, using particle image velocimetry (PIV), a new accurate method to determine the severity of aortic stenosis from the velocity field. Although very promising, the applicability of this method was limited in vivo because PIV requires transparent structures. However, this is not the case for magnetic resonance phase contrast (MR PC). In fact, MR PC is a powerful non-invasive, non-ionizing technique, able to investigate the velocity field through human heart valves. The objective of the present study is, therefore, to determine in vitro and in vivo the feasibility and the accuracy of our new method applied to the velocity field measured by MR PC. Furthermore, we will investigate the ability of MR PC to compute turbulence characteristics downstream of an aortic stenosis. We expect that the results of this project will have a significant impact on the clinical evaluation of the severity of aortic stenosis.