On MRI turbulence quantification

Abstract

Turbulent flow, characterized by velocity fluctuations, accompanies many forms of cardiovascular disease and may contribute to their progression and hemodynamic consequences. Several studies have investigated the effects of turbulence on the magnetic resonance imaging (MRI) signal. Quantitative MRI turbulence measurements have recently been shown to have great potential for application both in human cardiovascular flow and in engineering flow. In this article, potential pitfalls and sources of error in MRI turbulence measurements are theoretically and numerically investigated. Data acquisition strategies suitable for turbulence quantification are outlined. The results show that the sensitivity of MRI turbulence measurements to intravoxel mean velocity variations is negligible, but that noise may degrade the estimates if the turbulence encoding parameter is set improperly. Different approaches for utilizing a given amount of scan time were shown to influence the dynamic range and the uncertainty in the turbulence estimates due to noise. The findings reported in this work may be valuable for both in vitro and in vivo studies employing MRI methods for turbulence quantification.

Assessment of turbulent flow effects on the vessel wall using four-dimensional flow MRI

“…The Swedish National Infrastructure for Computing (SNIC) is acknowledged for computational resources provided by the National Supercomputer Centre (SNIC2014- [11][12][13][14][15][16][17][18][19][20][21][22] …”

“…Moreover, experimental assessment of the effects of turbulent flow on the vessel wall using non-invasive imaging has not been reported. However, recent developments have extended 4D Flow MRI to permit estimation of velocity fluctuation intensity and turbulent kinetic energy (TKE) (12,19,20). This approach has been validated and demonstrated in a variety of applications (21)(22)(23)(24)(25).…”

Left Ventricular Fluid Mechanics: The Long Way from Theoretical Models to Clinical Applications

“…This means that the increase in terms of accuracy has the drawback that flow results are averaged over a large number of heartbeats, and therefore that the small scale fluctuations responsible for blood mixing or intermittent acute phenomena may be hidden. However, advanced methods that allows decoding the fluctuating part of the signal, in addition to its average, are under development 23,24 and mitigate this limitation.…”

A novel MRI framework for the quantification of any moment of arbitrary velocity distributions

“…In spite of the distribution being clearly non-gaussian, good accuracy was obtained for Dk v < 1. Previously described guidelines for the choice of Dk v in IVSD mapping indicate that best IVSD sensitivity is obtained when Dk v ¼ 1/s opt , where s opt is an IVSD value of interest such as the maximum expected (14). For this value of Dk v , the error caused by the gaussian assumption is less than 3% in the cases included here.…”