两种不同螺距扫描对头颈血管减影CTA成像影响的分析

目的 探讨两种不同螺距扫描对头颈血管减影CTA成像中图像质量和辐射剂量的影响，从而在不同头颈血管病变中选择合适的螺距进行扫描。方法 搜集2010年5月至2013年12月46例患者头颈血管减影CTA影像资料，按照螺距分成A、B两组各23例；A组扫描螺距为0.984，B组扫描螺距为0.516；对A、B两组图像中颈部动脉、颅底较大动脉及颅内动脉分支行主、客观分析，对容积再现（VR）、最大密度投影（MIP）图像采用主观分析进行评分，客观分析包括测量颈总动脉、颈内动脉及大脑前动脉分支CT值、本底噪声、信噪比，并统计辐射剂量。 结果 A、B组两种螺距扫描在颈部动脉及颅底较大动脉的主观评分、图像信噪比方面差异均无统计学意义（P均＞0.05），平均CT值比较有统计学差异（P均＜0.01），但CT值均＞300HU，其接近或处于血管成像合适的CT值范围，对成像不构成影响。A、B两组扫描对颈部动脉、颅底较大动脉解剖结构显示及颅底骨质去除影响不大；对颅内动脉分支主观评分、平均CT值、图像信噪比比较有统计学意义（P均＜0.05），B组图像均优于A组图像，其显示颅内动脉分支更多、更细小、管壁更光整。 A组扫描的辐射剂量明显少于B组（P＜0.01）。结论 对于病变位于颈部或颅底较大血管处可使用0.984的螺距接受较少辐射剂量获得满意的减影CTA图像；对于怀疑颅内较小血管病变可使用0.516的螺距获得高质量的减影CTA图像，但须接受较多的辐射剂量。

Impact of two different pitch scanning on head and neck vascular subtraction CTA

Objective To explore the effect of two different pitch scanning in head and neck vascular subtraction CT angiography（CTA） on imaging quality and radiation dose in order to choose a suitable pitch scanning in different head and neck vascular lesions. Methods The imaging data of head and neck vascular subtraction CTA of 46 patients were enrolled in this study. The pictures were divided into two groups（ n = 23 each） according to scanning pitch ： group A（ scanning pitch ： 0. 984） and group B （ scanning pitch： 0.516 ）. The subjective and objective analysis on the pictures of the carotid artery, basicranial main artery and internal carotid artery braches was made. The subjective analysis was used for volume rendering （VR） and maximum intensity projection（MIP） pictures. The objective analysis was used for CT value, background noise and signal-to-noise ratio of common carotid artery,internal carotid artery and anterior cerebral artery braches, and the radiation dose was counted. Results There was no statistical difference in the subjective score, signal-to-noise ratio of picture for neck arteries and basicranial main artery in two groups （ all P 〉 0.05 ）. Though the average CT value had significant difference（all P 〈0.01 ）, the CT values were all more than 300 Hu with near or at the appropriate CT value range of vascular imaging which didn＇t influence the imaging. The scanning both two groups had no obvious influence on the view of anatomic structure of cervical arteries and basicranial main artery and removing basicranial bone, while it had statistical difference in the subjective score of intracranial arterial branches, average CT value and picture signal-to-noise ratio （ all P 〈 0.05）. The imaging of group B was superior to group A with advantages of showing more and the smaller intracranial artery branches and lighter and whole vascular wall. The radiation dose in group A was smaller than that in group B （ P 〈0. 01 ）. Conclusions Using 0.984 pitch can acquire sa