INFLUENCE OF IMAGING PARAMETERS, FLOW VELOCITY, AND PULSATILE FLOW ON3-DIMENSIONAL TIME-OF-FLIGHT MR-ANGIOGRAPHY - EXPERIMENTAL STUDIES

Objective: The purpose of this study is to evaluate the influence of i maging parameters (TR and flip angle), velocity and pulsatility of flo w on three-dimensional time-of-flight magnetic resonance (3D TOF MR) a ngiography by using a flow phantom. Methods: The 3D TOF MR angiography of a flow phantom was performed at 1.5-T with various TRs, flip angle s and flow velocity. The influence of pulsatile flow was also evaluate d. Results: The imaging parameters and flow velocity affected the satu ration effects of inflowing spins. Signal loss due to saturation of in flowing spins was more pronounced with a shorter TR, larger flip angle , or lower flow velocity. However signal intensity of stationary tissu e were more suppressed with a shorter TR resulting in a larger signal difference to noise ratio of the flowing fluid. Velocity of the flow a lso affected the signal loss due to intravoxel phase dispersion, which was apparently observed with a stenotic tube. Pulsatility of flow res ulted in decreased intensity of flowing fluid and in ghost artifacts a long the phase-encoding and slice-select directions. The spacing betwe en these ghosts and intensity of them were dependent on TR, flip angle and pulse rates. Conclusions: Understanding the influence of imaging parameters and flow characteristics is essential for evaluating the MR angiograms or for improving their quality. (C) 1997 Elsevier Science Ireland Ltd.