computed tomographic angiography was performed with a Philips 256i CT scanner (Brilliance iCT, Philips Healthcare, Cleveland, OH), and the patient was in the supine position. Scanning was performed from the thoracic entrance to the costal diaphragm. The contrast agent was injected with a high-pressure syringe at a speed of 4 mL/seconds, dosage of 30 to 50 mL, and nonionic contrast agent iodohydrin. CT scanning was conducted at the end of a single exhalation, with a breath-holding time of 4 to 7 seconds. noncardiac gating and automatic triggering scanning technologies were used. The scanning parameters were a tube current of 200 to 300 mas/ revolution, tube voltage of 120kv, collimation of 128 × 625, pitch of 0.16 to 0.2, rotation time of 270 to 330 ms, matrix of 512 × 512, and display field of 350 mm.