原始数据迭代重建和70kV CT扫描对图像质量和辐射剂量的影响  

Effects of sinogram-affirmed iterative reconstruction and 70 kV CT scanning on image quality and radiation dose

作　　者：李昂[1] 沈君姝[2] 曹新志[1,3] 郭辉[1] 潘永泉[1] 

机构地区：[1]南京军区南京总医院医学影像科,南京210002 [2]南京军区南京总医院放疗科,南京210002 [3]南京航空航天大学生物医学工程系,南京210016

出　　处：《医疗卫生装备》2015年第3期99-102,共4页Chinese Medical Equipment Journal

摘　　要：目的 :探讨原始数据迭代重建(sinogram-affirmed iterative reconstruction,SAFIRE)算法对图像质量、辐射剂量的影响以及利用该算法联合70 k V CT进行扫描的可行性。方法:选用Catphan500标准剂量模体,在70 k V、150~500 m As(50 m As间隔)和120 k V、150~500 m As(50 m As间隔)条件下行CT扫描,并对图像分别采用SAFIRE算法和滤波反投影(filtered back projection,FBP)算法重建,对所得图像的对比噪声比(contrast-to-noise ratio,CNR)和噪声值的差异行统计学分析。对行SAFIRE的70 k V、150~500 m As和120 k V、200 m As的图像,比较2种图像的CNR值和低对比可探测能力(low-contrast detectability,LCD)评分之间的统计学差异。结果:70 k V、150~500 m As和120 k V、150~500 m As行SAFIRE重建的图像CNR值均高于对应的FBP重建图像(t=5.61~8.73,P<0.001),SAFIRE重建图像的噪声均低于对应的FBP重建图像(t=-6.39^-10.98,P<0.001)。同样曝光量条件下,70 k V的图像噪声比120 k V显著增加,但当曝光量增加至450或500 m As时,70 k V的CNR及LCD值与120 k V、200 m As相比差异无统计学意义(P>0.05),而70 k V、450 m As和500 m As比120 k V、200 m As条件下得到图像的CT容积剂量指数(CT dose index volume,CTDIvol)分别下降到56.62%和47.18%。结论:SAFIRE联合70 k V CT扫描在适当增加m As的情况下可以保证图像质量不变,且可显著降低辐射剂量,是一种可行的CT扫描模式。Objective To discuss the effects of sinogram affirmed iterative reconstruction（SAFIRE） on image quality, radiation dose and the feasibility of combining SAFIRE with 70 k V during CT scanning. Methods The Catphan500 standard dose model was scanned, with the parameter of 70 k V, 150-500 m As（50 m As interval） and 120 k V, 150-500 m As（50m As interval）. The raw data were reconstructed with SAFIRE and filtered back projection（FBP） reconstruction algorithm.The difference between CNR and noise of images was analyzed statistically. The CT images, under 70 k V, 150-500 m As and 120 k V, 200 m As, reconstructed by SAFIRE, were scored on the low contrast detection capabilities（LCD） by two experienced radiologists, and the difference between CNR and LCD of the images was also analyzed. Results The CNR value of images reconstructed by SAFIRE, under 70 k V, 150-500 m As and 120 k V, 150-500 m As, were higher than those by FBP（t within 5.61 and 8.73, P〈0.001）, and noise was lower（t within-6.39 and-10.98, P〈0.001）. Compared with images obtained under 120 k V, the noise increased evidently in those under 70 k V with the same exposure. But no statistical difference was found, in the CNR and LCD of the images, between 70 k V and 120 k V when the value of exposure was being raised to 450 or 500 m As. The value of CTDIvol, in 70 k V, 450 m As and 500 m As, were found decreased to56.62% and 47.18%, comparing with those in 120 k V, 200 m As. Conclusion SAFIRE combined with 70 k V and proper exposure can have the same image quality as that by traditional CT scan condition, and can have the radiation dose decreased obviously, which may be a feasible CT scan mode.

关 键 词：SAFIRE 70kV CT扫描 图像质量 辐射剂量 

分 类 号：R814.2[医药卫生—影像医学与核医学]