Résumé
Objective (1) To determine the relationship between the MR signal intensity and the actual flow velocity under steady flow condition (2) to analyze the influence produced by the angle (?) between the flow direction and the velocity encoded gradient direction, and flip angle as well as section thickness on the velocity measurement under oblique flow condition (3) to develop a suitable protocol for using this method to measure volumetric flow rate in the transverse sinus system Methods Flow phantom, which simulated blood flow conditions in the transverse sinus system, consisted of a fluid filled cylinder and a bent tube with a 3 4 mm internal diameter A 1 5 T superconductive MR imager and VIGRE sequence were used for these studies A suitable protocol was based on consideration of the effects of (1) the accuracy of velocity and transverse area measurement of flow, and (2) signal to noise ratio (SNR) Results (1) Signal intensity (y) determined by MR and the actual flow velocity (x) showed straight line correlation, y=68 914x+357 206, R 2=0 998 (2) As the angle (?) increased, the transverse area of the signal determined by MR also increased, but the value of flow velocity decreased (3) As the flip angle increased, the SNR varied from 5 7 to 11 2 The maximum SNR was obtained with 30?flip angle (4) As the section thickness increased, the SNR and the transverse area of the signal determined by MR slightly increased Conclusions Phase contrast MR imaging is a practical method for measuring volumetric flow rates The angle (?) influenced the accuracy of flow velocity and the measurement of transverse area of flow whereas the flip angle and the section thickness substantially influenced the signal to noise ratio and the transverse area of flow