For angiography, a thin, soft tube (catheter) is placed in a blood vessel in the groin (such as in the femoral vein). First, a doctor numbs the area with a local anesthetic. Then, a needle is placed into the blood vessel. A guide wire is put through the needle into the blood vessel and the needle is removed. The catheter is slid over the guide wire and moved into the blood vessel. The catheter is guided through the blood vessels until the tip is in the area to be studied.