低管电压联合迭代重建技术在脑血管CT成像中的应用

目的：探讨脑血管CT成像中管电压联合迭代重建与图像质量及剂量间的关系,以确定最优管电压和迭代重建的参数。方法：利用ATOM 701-D型成年男性仿真人头颅模型,配置碘水混合造影剂自制脑血管。采用320排容积CT以80、100、120 k V管电压分别联合自适应迭代降剂量技术（AIDR 3D）迭代重建4个等级（off、mild、standard、strong）共12种方案,按管电流等其他参数不变进行颅脑单圈扫描,记录辐射剂量。获得横断面血管CT值及噪声、血管周边脑组织CT值及噪声、信噪比（SNR）和对比噪声比（CNR）。采用单因素方差分析比较不同管电压扫描及不同迭代算法水平重建对图像质量的影响。结果：管电压100k V时较120 k V时容积CT剂量指数（CTDIvol）、剂量长度乘积（DLP）及有效剂量E分别降低39.29%、39.52%和39.42%;管电压80 k V时较120 k V时CTDIvol、DLP及E分别降低66.88%、67.02%和67.31%。管电压一定,不同迭代水平重建时：血管噪声、血管周边脑组织噪声、SNR、CNR差异均有统计学意义（均P〈0.05）;血管CT值及血管周边脑组织CT值差异均无统计学意义（均P〉0.05）。迭代重建水平一定,不同管电压扫描时：血管CT值、血管噪声差异均有统计学意义（均P〈0.05）;血管周边脑组织CT值、SNR、CNR差异均无统计学意义（均P〉0.05）;血管周边脑组织噪声在AIDR 3D off和mild水平时差异有统计学意义（P〈0.05）,在standard和strong水平时差异无统计学意义（P〉0.05）。结论：100 k V管电压扫描联合standard或strong水平的迭代重建算法会获得较高质量的脑血管成像。

An application of low tube voltage in combination with simultaneous iterative reconstruction technique in cerebrovascular CT imaging

Objective： To study the impacts of tube voltage and simultaneous iterative reconstruction tech-nique on the image quality and radiation dose in cerebrovascular imaging and determine the optimum tube volt- age and iterative reconstruction parameters. Methods： A home-made blood vessel of brain was constructed using an ATOM 701-D adult male phantom head and iodine-water mixture contrast agent. A 320-row volume CT was used to scan the home-made brain at tube voltages of 80, 100 and 120 kV in combination with off, mild, standard and strong iterative reconstruction levels （12 protocols in total）, respectively. Tube current and other parameters were not changed during scanning. CT value of the transverse blood vessels and its corresponding noise, CT value of brain tissue around blood vessels and its corresponding noise, signal-to-noise ratio （SNR） and contrast-to-noise ratio （CNR） were obtained. One-Way ANOVA analysis was applied to investigate the impacts of different tube voltages and simultaneous iterative reconstruction levels to image quality. Results： Compared with group 120 kV, the CTDIvol, dose length product （DLP）, effective dose （ED） of group 100 kV and 80 kV reduced 39.29%, 39.52%, 39.42% and 66.88%, 67.02%, 67.31% respectively. When the tube voltage was kept constant, blood ves- sel noise, noise of brain surrounding blood vessels, SNR and CNR showed statistical difference （P〈0.05）, while CT values of blood vessel and brain tissue around blood vessels had no statistical difference （P〉0.05） at different iterative reconstruction levels. When iterative reconstruction level was not changed and tube voltage was varied,both CT values of blood vessel and blood vessel noise exhibited statistical difference （P〈0.05）, CT values of brain tissue around blood vessels, SNR and CNR had no statistical difference （P〉0.05）, and noise of brain tissue around blood vessels showed statistical difference （P〈0.05） at AIDR 3D off and mild levels and no statistical dif- ference ?