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[Usefulness of lower extremity magnetic resonance venography with two-dimensional spiral gradient echo sequence and effect of patient positioning during the visualization of lower extremity veins].

PURPOSE
We examined the two-dimensional-spiral-gradient-echo (2D-spiral-GRE) for magnetic resonance venography (MRV). In addition, five variations in patient positioning of the MRV were investigated to determine the best method of visualizing.


METHODS
First, flow phantom experiments were performed on a 1.5 T scanner. Using a flow phantom, the authors aimed to (1) measure the optimal TR (40, 60, 140, 190 ms), (2) measure the flip angle (20-60 degrees) and (3) determine the optimal combination of saturation pulse (S, I, A, P, R, L) and half acquisition method for MRV. Secondly, ten volunteers without vessel disease were imaged by phase contrast sequence for measured mean value of the venous area and velocity of the femoral and popliteal vein. The volunteers' MRV images were compared qualitatively on visualization.


RESULTS
There is better demonstration of the veins under the longer repetition time (TR), resulting in a setting of 2-3 acquisitions ordering. Because the fluid or blood has been irradiated with pulsed radiofrequency multiple times, optimal FA was about 40 degrees. Combination of saturation pulse was slightly effective and the best saturation effect was seen in the half acquisition method. Volunteer study patient positioning, which involves the slight lifting up of the upper half of the body and continuous warming of the feet, has brought about a larger area and a slower velocity in the lower extremity veins. The greater veins and peripheral veins were demonstrated more accurately.


CONCLUSION
2D-spiral-GRE sequence was a useful method for lower extremity MRV. Furthermore, the most effective patient positioning for the lower extremity MRV was slightly lifting up the upper half of the body and continuously warming the feet. These enabled the best results to be obtained in the lower extremity MRV.