2. Insert the catheter into thick secondary arteries, such as the contralateral common iliac artery and superior mesenteric artery, and the insertion depth is about 5cm~ 15cm. Pull out the guide wire so that the end of the guide wire is located at the bifurcation of the artery or at the beginning of the artery, and push the catheter upward while rotating. The inserted part will become a ring, exit the entering artery and return to the abdominal aorta, and the ring will be formed.