PURPOSE: To prepare a data base for semi-quantitative measurement of blood flow velocity on MR phase imaging technique by analyzing the characteristics of flow image according to the ranges of flow velocity. MATERIALS AND METHODS: We obtained MR phase images of flow with velocity ranging from 0 to 70cm/sec. A straight flow tube with 2.09cm internal diameter and a flow tube with 75% stenosis were used as flow phantoms for this study. MR imagings were performed on a 0.35 T MR imaging system. RESULTS: At a velocity of 0-3cm/sec, the MR phase signal proceeded from an equivocal phase change to a homogeneous intraluminal signal intensity. Ata flow velocity of 3.1cm/sec, first phase wrap occurred, and there were two phase wraps up to 15cm/sec of flow velocity. In this velocity range, the MR phase image revealed an isocentric circular target appearance. At a velocity range of 15-30cm/sec, three tofour phase wraps occurred, and the MR phase image showed a multiple target appearance. At a velocity above 30cm/sec, the MR phase image showed an irregular unstructured appearance and above 50cm/sec, there were no flow signals and only noise-like signals were observed. The flow phantom of the stenosis model demonstrated the same phase image pattern as the high velocity flow in the stenotic and post-stenotic areas. In the pre-stenotic area, acharacteristic reversed laminar flow profile was observed. CONCLUSION: Flow velocity can be detected semiquantitatively as velocity ranges on MR phase imaging. The results of the experiment using a stenotic model suggest that MR phase imaging can be used as a modality for investigation of flow velocity and profiles.
Blood Flow Velocity ; Constriction, Pathologic ; Magnetic Resonance Imaging