Abstract

In this methodological paper we investigate the systematic loss of MR signals due to complex flow conditions subsequent to a stenosis in comparative phantom studies with different flow optimized imaging sequences. To understand the hemodynamic effects on the MR signal's behaviour, numerical flow analysis was calculated in two dimensions referred to the incompressible Navier-Stokes equation. Based on the calculated data the experimental results could be simulated.To generate complex flow conditions in a model situation, a flow phantom was constructed with water flowing through glass pipes with strictures of different diameters. The signal of the flowing fluid was acquired using FLASH sequences either with or without flow compensation. The investigations were carried out under variation of the echo time on two tomographs with different gradient system performance.The experiments as well as the numerical simulations of the measurements show that the signal loss due to stationary and non stationary current vortices can be reduced significantly by using flow-compensated sequences. The images acquired with sequences without flow compensation show a strong dependence on the signal loss from the echo time even with constant gradient duration which is induced by instationary flow conditions.

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