重建算法对肺部磨玻璃密度结节体模CT低剂量扫描的影响  

Impact of reconstruction parameters on chest phantom with ground glass nodules using CT scan

作　　者：杨振悦 刘士远[1] 范丽[1] 周莹[1] 

机构地区：[1]第二军医大学附属长征医院影像诊断科,上海200003

出　　处：《实用放射学杂志》2015年第11期1856-1859,1882,共5页Journal of Practical Radiology

基　　金：国家自然科学基金面上项目（81230030）;上海市科学委员会重点项目（13411950100）.

摘　　要：目的 探讨适合纯磨玻璃密度结节（pGGN）评估的低剂量CT重建层厚和重建重叠率的优化组合方案及迭代重建对图像质量的影响.方法在5种不同的层厚（1 mm、2 mm、3 mm、4 mm、5 mm）、2种重建重叠率（50％和0％）下对含有9个pGGN的仿真胸部体模进行扫描;分别采用传统的滤波反投影（FBP）和迭代重建算法iDose4对图像进行数据重建.测量不同层厚、不同重叠率及不同重建算法下pGGN的CT值、计算图像的对比噪声比（CNR）,并进行统计学分析.结果 不同层厚的条件下结节的CT值及图像CNR值有显著统计学差异（P值均＜0.05）;随着层厚的增加,结节CT值逐渐减小,图像的CNR值逐渐增大.且图像CNR值在层厚为4 mm、重建重叠率为50％时达到峰值.在相同层厚,不同重建重叠率的条件下结节的CT值及图像CNR值有显著统计学差异（P值均＜0.05）.重建重叠率为层厚的50％时,结节CT值和图像CNR值均较重叠率为0％时增大.2种重建算法的图像CNR值有显著统计学差异（P值均＜0.05）.结论 在低剂量扫描条件下,重建重叠率为50％有利于结节CT值的测量和提高图像质量.iDose4迭代重建技术可以改善图像噪声,有利于结节外部形态的显示.Objective To optimize the slice thickness and overlap parameters for image reconstruction and to study the effect of iterative reconstruction on detectability and characterization of pure ground glass nodules during low-dose thoracic CT. Methods CT scans were performed on chest phantom with 9 pGGNs with 5 different slice thickness（1 mm,2 ram,3 mm,4 mm,5 mm） and 2 different overlap （50%,0%）. All data were reconstructed with filtered back projection （FBP） and iterative reconstructions（iDose4 ）. The CT values obtained and the contrast to noise ratio （CNR） was measured. Results Significant differences were found on the CT values obtained and CNR using different slice thickness （P〈0. 05 ）. CT values obtained were found to be decreased with increasing slice thickness. CNR increased with increasing slice thickness and reached to peak at 4.0/2.0 mm. Significant differences were found on the CT values obtained and CNR using different overlap （P〈0.05）. The CT values obtained and CNR were larger on 50% overlap than continue（0%）. Significant differences were found on the CNR using different algorithms （P〈0. 05）. Conclusion 50% overlap and iDose4 improves conspicuity of ground glass nodules through a significant increase in the CT values obtained and CNR.

关 键 词：磨玻璃密度结节 重建算法 体模 

分 类 号：R563[医药卫生—呼吸系统] R814.42[医药卫生—内科学]