应用后过滤重组降低64层螺旋CT心脏检查X线剂量的初步研究  

Preliminary study of X-ray dosage reduction using post-processing filter in 64-slice spiral CT cardiac examination

作　　者：高建华[1] 戴汝平[2] 郑静晨[1] 王贵生[1] 李剑颖[1] 崔英[1] 赵雯[3] 

机构地区：[1]武警总医院放射科,北京100039 [2]中国医学科学院中国协和医科大学心血管病研究所阜外心血管病医院放射科 [3]武警总医院 信息科统计室,北京100039

出　　处：《中华放射学杂志》2007年第10期1014-1018,共5页Chinese Journal of Radiology

摘　　要：目的评价后过滤(C_2)重组对降低64层螺旋 CT(MSCT)心脏检查射线剂量的价值。方法试验分2步进行:(1)连续选取30例拟行64层 MSCT 冠状动脉成像的患者(A 组),采用640 mA,120 kV,0.35 s/r,层厚0.625 mm,螺距0.22～0.24,前置滤线器选用体部滤线器模式。采集图像后对同一患者分别进行使用 C_2和不使用 C_2的重组,得到 C_2组和 NC_2组图像,以双盲法对 C_2、NC_2组图像进行质量评分,测量各组图像噪声值,对2组间图像质量评分及噪声差异进行 t 检验。(2)连续选取30例(B 组)患者进行 CT 冠状动脉成像,根据预试验的结果,将 X 线管电流降为450 mA,其他技术参数不变。采集图像后均使用 C_2重组,得到2C_2组图像,以双盲法对2C_2组图像进行质量评分,测量图像噪声值,并对2C_2组和 NC_2组间图像质量评分及噪声差异进行 t 检验。(3)将2C_2、NC_2(C_2)组检查时计算机自动计算得出的平均容积 CT 剂量指数(CTDIvol)换算成有效剂量(ED),对2组 CTDIvol、ED 值进行 t 检验。结果(1)C_2组、NC_2组和2C_2组图像质量评分分别为(3.71±0.31)、(3.72±0.29)和(3.67±0.34)分,C_2、NC_2组间及2C_2、NC_2组间差异均无统计学意义(P>0.05)。C_2组、NC_2组和2C_2组噪声值分别为22±4、27±5和26±3,C_2组较 NC_2组图像噪声下降约18%,2C_2、NC_2组间差异无统计学意义(P>0.05)。(2)2C_2、NC_2(C_2)组 CTDIvol 值分别为(60±5)和(88±10)mGy;ED 值分别为(12.3±1.0)和(18.0±2.0)mSv,2C_2组 CTDIvol 和 ED 均值明显低于NC_2组(约32%),2组间差异有统计学意义(P<0.01)。结论在64层 MSCT 心脏成像时应用 C_2重组可在保证图像质量不变的前提下降低约30%的管电流,从而有效减少了检查中的射线剂量。Objective To evaluate the adaptive post-processing filter （C2 ） on reducing X-ray dosage in 64-slice CT cardiac examinations. Methods The study was divided into two steps： （ 1 ） On 30 consecutive patients （ group A ） prescribed for cardiac scans on 64-slice CT, the scan protocol was 120 kV, 640 mA, 0. 35 s/r, 0. 625 mm slice thickness, 0.22-0. 24 pitch and large body bewtie. For each patients, cardiac images were reconstructed with and without C2 filter to create two image sets （ C2 and NC2 , respectively）. The image quality was blindly evaluated between C2 and NC2. Image noises were also measured and their means and standard deviations calculated for the two sets. Statistical t-test analysis was performed on the quality scores and the noise between the two data sets. （2） On the 30 consecutive cardiac patients in another group （group B） , the protocol was kept the same as in group A except for decreasing the tube current 450 mA based on the results from group A. Images were reconstructed using post-processing filter C2 to create 2C2 image set. Statistical t-test was performed between image sets of 2C2 and NC2 in step 1. （3） CTDIvol values from the 2C2 and NC2（C2） groups were converted into effective dose （ED） and the ED values of the two groups were compared. Results （ 1 ） The image quality scores for the C2 and NC2 sets were 3.71±0. 31 and 3.72±0. 29, respectively, with t-test of P 〉 0. 05, indicating no significant statistical difference（P 〉0. 05）. The noise of C2 and NC2 sets were 22±4,27±5, respectively,indicating the difference was statistically significant（P 〈 0. 01 ）. The noise with C2 filter had 18% noise reduction compared to those without C2 filter. （ 2 ） The image quality scores for the 2C2 and NC2 sets were 3.67±0. 34, 3.72±0.29, indicating no significant statistical difference （ P 〉 0. 05 ）. The noise of 2C2 and NC2 sets were 26±3,27±5, indicating no significant statistical difference （ P 〉 0. 05 ）. （ 3 ） The average

关 键 词：体层摄影术 X线计算机 心脏 冠状血管 辐射剂量 

分 类 号：R816.2[医药卫生—放射医学]