ObjectiveTo identify the optimal rotation time and pitch of 64-slice spiral CT angiography for arterial occlusive diseases (AOD) of the lower limbs. MethodsWe performed test-bolus in eighty patients with AOD of the lower limbs (48 with intermittent claudication and 32 with ischemic rest pain or ulceration) to confirm the aortic peak time, popliteal artery peak time and aortopopliteal bolus transit time. The patients were randomly assigned to receive two sets of scan protocols for lower limb arterial 64-slice spiral CT angiography (CTA) examination (n=40): protocol A, with a gantry rotation time of 330 ms and a pitch of 1.0; protocol B, with a gantry rotation time of 500 ms and a pitch of 0.85. Two experienced radiologists independently evaluated the image quality of the lower limb artery. ResultsGreat differences in the time to peak enhancement in the aorta (14-33 s) and popliteal arteries (20-48 s) and the aortopopliteal bolus transit time (4-24 s) were found between different AOD patients. Wide overlap of the time to peak enhancement and transit time was observed between intermittent claudication patients and ischemic rest pain or ulceration patients. The qualities of segment images were rated as excellent 63.3% (152/240), good 30.0% (72/240), and poor 30.0% (72/240) for protocol A, and excellent 98.3% (234/238) and good 1.7% (4/238) for protocol B, with no poor images in protocol B. Conclusion64-slice CTA with a gantry rotation time of 500 ms, a pitch of 0.85, scan time>30 s, and with the contrast agent injection time maintained at 35 s, can obtain better image of lower limb arteries in patients with AOD of the lower limbs.