PURPOSE: The purpose of this study was to analyze the flow signal chracteristics of 3 dimensional time of flight MR angiography (3D TOF MRA) by using a flow phantom model. MATERIALS AND METHODS: Nonpulsatile flow phantom and tap water were used in this experiment. We performed FISP 3D TOF MRA with various values of parameters (repetition time ; 34-100 msec, flip angle ; 10°-50°, flow velocity ; 14.7-73.6 cm/sec, Gd-DTPA concentration ; 0.6-3.6 mmol/liter). The values of flow signal intensity (SI), signal to noise ratio (SNR) and contrast to noise ratio (CNR) were measured from base images of each MRA. The measured values were displayed graphically and analyzed statistically in relation to various parameters. RESULTS: A prolongation of repetition time resulted in a decrease of CNR of flow. As flip angles increased, SNR and CNR of flow also increased but larger flip angles of more than 40° rapidly saturated exit flow. As the flow velocities increased in a range of 14.7-73.6 cm/sec, SNR and CNR of flow decreased. This may be related to the phase dispersion effect of laminar flow, more dominat than the TOF effect. The addition of Gd-DTPA to water increased SNR and CNR of exit flow. There were however, no significant differences of SI, SNR or CNR of flow among the various concentrations of Gd-DTPA. CONCLUSION: An experimental MRA study using a flow phantom model was useful in understanding the flow signal characteristics of 3D TOF MRA within various MRA parameters. Our preliminary results can be used as basic data for refined flow experiments.