双源CT单能谱成像技术减低颅内动脉瘤夹伪影的研究

目的:探讨颅内动脉瘤夹植入术后,双源CT头部血管双能量成像中单能谱成像技术在降低伪影方面的临床应用价值,寻求图像质量最佳的单能量成像点。方法:对48例颅内动脉瘤颈夹闭术后患者行双能量头部血管扫描,获得双能量扫描数据后,采用双能量软件内的单能谱技术(Monoenergetic)进行后处理。对40~120keV的单能量数据每隔10keV进行重建,共9组单能量图像,对每组图像选取4个点(a^d)进行CT值测量。a点位于动脉瘤夹伪影最重的脑组织即动脉瘤夹长轴的尾部;b点为a点的对称点,位于无动脉瘤夹伪影的脑组织内;c点位于受动脉瘤夹伪影影响最重的血管;d点为c点的对称点,位于无动脉瘤夹伪影影响的血管内。测量CT值分别记录为CTa、CTb、CTc、CTd,计算a、b两点CT值的差值即|CTa-CTb|以及c、d两点CT值的差值即|CTc-CTd|。采用配对t检验比较CTa、CTb之间,CTc、CTd之间,以及|CTa-CTb|、|CTc-CTd|的差异。结果:9组单能量图像上,a与b点、c与d点的CT值差异均有统计学意义(P<0.05);|CTa-CTb|和|CTc-CTd|在9组单能量图像间差异均有统计学意义(P<0.05)。随能量的升高|CTa-CTb|逐渐降低,而|CTc-CTd|除70keV组(为最低)外呈逐渐增加,其中40keV组|CTa-CTb|和|CTc-CTd|分别为(270.54±9.08)和(9.64±2.46)HU,70keV组|CTa-CTb|和|CTc-CTd|分别为(65.85±1.99)和(1.03±0.24)HU,120keV组|CTa-CTb|和|CTc-CTd|分别为(10.51±2.79)和(8.32±0.84)HU。结论:颅内动脉瘤夹闭术后患者复查头部血管增强扫描,CT单能谱成像技术可明显降低颅内动脉瘤夹的伪影,采用70keV进行图像重建可获得较好的图像质量。

Optimal monoenergetie imaging for reducing titanium clip metal artifacts in dual-energy computed tomography angiography

Objective：To study the application of monoenergetic imaging in reducing the metal artifacts of titanium clip by dual energy computed tomography angiograpby imaging,and to find the optimal monoenergetic imaging protocol for optimal image quality. Methods： Forty eight patients with metal implants of brain underwent dual energy computed tomo graphy angiograpby. The monoenergetic analysis was used to obtain the monoenergetic images by special dual energy ima ging postprocessing software. Nine groups of monoenergetic images were obtained from 40 to 140keV. For each patient, ima ges with heaviest artifacts level nearby titanium clip in brain tissue （A）,no or less artifacts level nearby titanium clip in brain tissue （B）,heaviest artifacts level nearby titanium clip in blood vessel （C）, no or less artifacts level nearby titanium clip blood vessel （D） were selected in every group. CT value of ROIs were measured and analyzed （named CTa ,CTb ,CTc and CTd） with paired t-test. Results：On the monoenergetic images of nine groups,there were significant differences （P〈0. 05） of CT values between point a and b,point c and d.｜CTa-CTb ｜ and ｜CTc-CTd｜ in nine groups were significantly dif- ferent （P〈0.05）. With the increase of energy, ｜CTa-CTb｜ was gradually decreased,while ｜CTc-CTd｜ was gradually in creased, except the group of 70keV （with the minimum value）. At 40keV, ｜Ca-CTb｜ and ｜CTc- CTd｜ were （270.54 ± 9. 08） and （9.64±2.46）HU;At 70keV, ｜CTa-CTb ｜ and ｜CTc-CTd｜ were （65. 85±1. 99） and （1. 03±0. 24）HU;At 120keV, ｜CTa- CTb｜and ｜CTc-CTd ｜ were （10.51±2.79）HU and （8.32±70.84）HU. Conclusion： Monoenergetic tech nique of dual energy CT can effectively reduce artifacts of titanium clip implants. 70keV was the point for optimal quality of monoenergetic imaging.