时间减影法与双能量减影法在脑血管成像中的对比观察

目的 比较双能量减影法与时间减影法CT脑血管成像的图像质量和扫描剂量,评价两种方法的优劣及临床应用价值.方法 对60例临床怀疑颅内血管性病变患者行CT血管成像检查,包括平扫及增强扫描,增强扫描采用双能量程序,即A球管采用80 kV,B球管采用140 kV,一次性扫描采集两个不同能量的数据.数据后处理:①用平扫+80 kV增强数据行传统去骨数字减影(时间减影法);②用80 kV及140 kV两个不同能量的数据行直接去骨减影(双能量减影法).保存减影后数据,完成容积显示(VR)和最大密度投影(MIP).将MIP及VR图像质量分为4级,比较两种处理方法的图像质量和患者所接受的平均有效放射剂量.全部病变结果均经手术或介入证实.结果 ①两种方法均清晰显示所有患者的颈内动脉颅内主干及主要分支,Willis环显示清楚;两种方法总体质量评分值差异无统计学意义(P>0.05);②两种方法均清晰显示24例动脉瘤大小、形态、与载瘤动脉关系、瘤颈及瘤轴指向;4例血管畸形病例均清晰显示异常血管团的形态和范围,动静脉畸形较好显示供血动脉及引流静脉;③时间减影法CTA患者受到的平均有效放射剂量为(26.60±0.50)mSv,双能量CTA的平均有效放射剂量为(22.40±0.50)mSv.结论 时间减影法与双能量减影法CT血管成像均能清晰显示正常颅内血管及血管性病变;双能量减影法患者受到的放射剂量更低.对扫描中不配合患者,双能量减影法去骨效果更好.

A comparative observation of cerebral CT angiography with time and dual-energy subtraction

Objective To compare the image quality and scanning dose of time-subtraction and dual-energy-subtraction cerebral CT angiography, and to assess clinical application value of both methods. Methods Plain and enhanced scanning were performed on 60 patients suspected cerebral vessel diseases with dual-source CT. Dual-energy mode with tube voltages of 140 and 80 kV was used in enhanced scanning, and data of two different energy were collected in one scanning. ①Traditional removed-bone digital subtraction (time-subtraction) with plain and 80 kV enhanced scanning data were obtained. Volume render (VR) and maximum intensity projection (MIP) reconstruction were finished; ②Direct removed-bone digital subtraction (dual-energy subtraction) with 80 kV and 140 kV enhanced scanning data were obtained. VR and MIP reconstruction were finished. The image quality of VR and MIP was divided into 4 grades, and were compared as well as average effective radiological dose. All the diseases were confirmed with surgery or DSA. Average effective radiological dose was compared with time-subtraction and dual-energy subtraction. Results Internal carotid artery trunk and branch and Willis circles were displayed clearly with two methods in 60 cases. No significant difference was found (P>0.05) between total quality score of the two methods. The size, shape, neck and axis point of aneurysm in 24 cases were clearly displayed, so as the shape and extent of abnormal vessel bolus in 4 cases, while arteries and veins were also clear in artery-vein malformation; ③The average radiological dose was (26.60±0.50)mSv in time-subtraction and (22.40±0.50) mSv in dual-energy subtraction. Conclusion The normal, abnormal vessels and diseases can be clearly displayed at time-subtraction and dual-energy subtraction CTA. The effect of dual-energy-subtraction is better than that of time-subtraction CTA in no-cooperation patients, and the radiological dose is lower in dual-energy CTA.