摘要
探讨不同单能量及权重多模型的自适应统计迭代重组(ASiR-V)在头颅能谱CTA中对图像质量和辐射剂量的影响,获取显示头颅血管的最佳单能量及迭代重组参数.方法(1)体模研究:对置入模拟脑血管的头颅仿真体模进行80、140 kV瞬时切换能谱扫描,将其分为A体模组,采用低管电流(280 mA),分别进行反滤波投影(FBP)及ASiR-V 20%、40%、60%、80%重组,得到40、45、50、55、60、65、70 keV的单能量图像;B体模组采用常规管电流(445 mA)和FBP算法,自动输出70 keV图像.测量各组图像模拟脑血管CT值及背景噪声,计算信噪比(SNR)及对比噪声比(CNR).(2)临床研究:前瞻性纳入2018年1月至6月四川大学华西医院需行头颅增强CTA检查的40例患者,采用数字表法随机分为A患者组和B患者组,A患者组的扫描参数与A体模组一致,B患者组的扫描参数和B体模组一致.采用5分法对图像进行主观评分.记录体模研究和临床研究各组扫描的剂量长度乘积(DLP).采用独立样本t检验比较A患者组和B患者组间DLP的差异,采用ANOVA单因素方差或Mann-Whitney U秩和检验比较各组图像的质量.结果(1)体模研究:不同单能量图像上,模拟脑血管噪声、CNR差异有统计学意义(P<0.05),40~55 keV图像CNR高于70 keV,差异有统计学意义(P<0.05);不同迭代重组比例图像上,模拟脑血管噪声、SNR及CNR差异均有统计学意义(P<0.05);ASiR-V 60%及80%图像的SNR、CNR高于其余组(P<0.05),但二者间差异无统计学意义(P>0.05);ASiR-V 80%图像噪声较低(P<0.05).(2)临床研究:A患者组中55 keV及60 keV图像质量主观评分高于其他组,且随着迭代重组比例增加,40~50 keV图像的主观评分增高,差异有统计学意义(P<0.05).低管电流(280 mA)、55 keV、ASiR-V 60%及ASiR-V 80%组患者模拟脑血管图像的SNR、CNR及主观评分高于B组患者,A患者组的DLP为(131.42±8.68)mGy·cm,低于B患者组的(212.18±11.56)mGy·cm(t=23.974,P<0.05).结论使用低管电流(280 mA)进行头颅CTA能谱扫描结合单能量及ASiR-V迭代算法可在保证较好图像质量的同时显著降低辐射剂量,55 keV结合ASiR-V 60%~80%可以获得较高的图像质量,满足诊断需求.
Objective To analyze the value of combining the virtual monochromatic spectral(VMS)image and adaptive statistical iterative reconstruction V(ASiR-V)in low tube current dual-energy spectral imaging in head CTA,and to explore the optimal VMS and ASiR-V level while reducing the radiation dose.Method(1)Phantom study:an Anthropomorphic PBU-60 angiographic head phantom was examined on a Revolution CT with spectral imaging mode at two different tube current.Images of different energy levels(at 40,45,50,55,60,65 and 70 keV)in A group[the low tube current group(with 280 mA)]were reconstructed with the combination of filtered back projection(FBP),20%,40%,60% and 80% ASiR-V.VMS images at 70 keV in B group[the routine tube current group(with 445 mA)]were reconstructed with FBP only.The standard deviation(SD),signal to noise ratio(SNR)and contrast to noise ratio(CNR)of phantom study were measured and examined by ANOVA variance analysis.(2)Clinical study:to prospectively select 40 patients(randomly divided into A and B groups with 20 patients in each group),the subjective scores of patients were assessed with a 5-point scale system and compared by the Mann-Whitney U test.The radiation dose was recorded and analyzed by t test.Results(1)Phantom study:there were significant differences in the image noise,CNR of the simulated cerebral vessels at different energy levels of VMS image(P<0.05).VMS images at 40 to 55 keV yielded a higher CNR compared with 70 keV(P<0.05).The SNR and CNR in the low tube current group with ASiR-V 60% and ASiR-V 80% were higher than that of the FBP,ASiR-V 20% and ASiR-V 40% images in the same group(P<0.05).(2)Clinical study:the subjective scores at 55 keV and 60 keV were higher than others(P<0.05).The subject scores of 40,50 and 55 keV were increased as the proportion of ASiR-V increased.(3)The SNR and CNR of the simulated cerebral vessels and subjective scores in of the 55 keV VMS images with ASiR-V 60% and ASiR-V 80% in the low tube current patient group was higher than that of the 70 keV FBP images in the routine tube current group(P<0.05).The radiation dose of A group was lower than B group(t=23.974,P<0.05).Conclusions VMS images in low tube current spectral imaging combined with ASiR-V can significantly reduce radiation dose and ensure image quality in head CTA.The 55 keV VMS images with ASiR-V60% and 80% provide higher image quality.
作者
宋婷妮
李真林
赵俐红
李万江
李磊
赵飞
李玉明
夏春潮
Song Tingni;Li Zhenlin;Zhao Lihong;Li Wanjiang;Li Lei;Zhao Fei;Li Yuming;Xia Chunchao(Department of Radiology,West China Hospital,Sichuan University,Chengdu 610041,China)
出处
《中华放射学杂志》
CAS
CSCD
北大核心
2019年第11期998-1004,共7页
Chinese Journal of Radiology
基金
四川省科技厅重点研发项目(2017SZ0016)
四川大学华西医院学科卓越发展"1·3·5"工程项目(ZYGD18019)。
关键词
体层摄影术
X线计算机
辐射剂量
单能量图像
迭代重组
Tomography,X-ray computed
Radiation dosage
Virtual monochromatic spectral image
Iterative reconstruction
