Contrast agent shortens the T1 value of blood, using ultra-fast and very heavily weighted T1WI. 1.5T, fat T1 value of 250ms, blood T1 value of 1200ms, T1 value of blood shortened to 100ms after dough injection of contrast agent. CE-MRA using 3D ultra-fast scrambled phase GRE T1WI sequences, flow contributes little to the image, and the contrast between blood and other tissues is made by contrast agent manufactured. Lower extremity veins, iliac veins, and inferior vena cava can be examined using a superficial dorsal foot vein approach, using a tourniquet tied around the ankle to block superficial venous flow, allowing the contrast agent to return via the deep veins. The contrast agent needs to be diluted 6-10 times with saline, preferably by pushing the diluted contrast agent from the bilateral dorsal foot arteries simultaneously. Fat suppression. Other MRA methods: i. Black blood method ii. Balance-SSFP method MRA iii. T2 preparation for rapid GRE MRA