64层螺旋CT血管成像评估下肢动脉闭塞性疾病的合理旋转时间及螺距

Optimal rotation time and pitch study of CT angiography for arterial occlusive diseases of lower limbs

目的筛选64层螺旋CT血管成像评估下肢动脉闭塞性疾病（peripheral arterial occlusive disease,PAOD）的合理旋转时间及螺距。方法80例PAOD患者（包括间歇性跛行48例,缺血性静息痛或溃疡32例）全部应用小剂量团注试验分别确定主动脉峰值时间、腘动脉峰值时间及主腘动脉通过时间。患者随机均分入两组扫描参数进行下肢动脉64层螺旋CT血管造影（CTA）检查（n=40）,A组参数为X线管球旋转时间330 ms,螺距1.0;B组为X线管球旋转时间500 ms,螺距0.85。由2位血管影像诊断方面有经验的放射科医师盲法对下肢动脉成像质量进行综合评价,比较不同参数下CTA图像质量。结果不同PAOD患者主动脉峰值时间（14~33 s）、腘动脉峰值时间（20~48 s）、主腘动脉通过时间（4~24 s）及主腘动脉通过速度（29~177 mm/s）差异较大,间歇性跛行和缺血性静息痛或溃疡患者上述各指标有很大一部分相互重叠。A组成像图像质量为优、良、差的节段分别占63.3%（152/240）、30.0%（72/240）、6.7%（16/240）;B组成像图像质量为优、良的节段分别占98.3%（234/238）和1.7%（4/238）,无成像图像质量为差的节段。结论对PAOD患者行下肢动脉64层螺旋CT血管三维成像检查时,设定X线管球旋转时间为500 ms、螺距为0.85、扫描时间大于30 s、造影剂注射时间保持在35 s,可获得较好的图像质量。

Objective To identify the optimal rotation time and pitch of 64-slice spiral CT angiography for arterial occlusive diseases（AOD） of the lower limbs.Methods We 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.Results Great 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.Conclusion 64-slice CTA with a gantry rotation time of 500 ms,a pitch of 0.85,scan time30 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.