能谱CT单能量技术联合ASIR及ASIR-V改善胸部增强CT图像质量的研究

目的探讨应用能谱CT最佳单能量成像联合ASIR及ASIR-V重建技术对胸部CT增强扫描动脉期图像质量的优化。方法搜集行胸部增强能谱CT检查的62例患者资料,使用能谱GSI模式进行扫描并重建,在传统重建模式(FBP)重建下,以间隔10 keV为一组重建出40~140 keV的11组单能量(MONO)图像,与140 kVp混合能量(QC)图像共组成12组图像。对12组图像的CNR、BHA采用单因素方差分析进行统计,并采用秩和检验分析其主观评分。得出能谱CT成像中伪影较小且图像质量较高的单能量图像。将其单能量图像分别与30%、50%、70%水平的ASIR及ASIR-V进行重建,得到6组新重建模式下的单能量图像,将其与FBP重建下QC及此单能量图像共组成8组图像并使用较前相同的统计学方法对其主观及客观评价进行分析比较。结果在FBP重建下,80 keV图像的CNR值为7.7±2.0,与QC图像无统计学差异(P>0.05);血管处的BHA值为44.4±22.0,低于QC图像(P<0.05);图像质量主观评分为4.50±0.62,与QC图像无差异(P>0.05);伪影主观评分为2.45±0.62,低于QC图像(P<0.05);具有较低的伪影水平并保持了较好的图像质量。因此选取80 keV做为最佳单能量值进行下一步研究。80 keV联合50%ASIR-V的CNR值为13.9±4.3,高于QC图像(P<0.05);BHA值与其他组差异无统计学意义;图像质量主观评分为4.90±0.298,高于其他组(P<0.05)。结论与常规胸部增强扫描动脉期图像相比,能谱CT 80 keV单能量联合50%ASIR-V图像能够减低对比剂硬化伪影,同时提高图像质量,可常规应用于胸部CT增强扫描。

The Application of Spectral CT Monochromatic Imaging Combined with ASIR and ASIR-V to Optimize the Image Quality in Chest Enhanced CT Scan

Objective To explore the application of spectral CT optimal monochromatic imaging combined with adaptive iterative reconstruction(ASIR)and adaptive iterative reconstruction-V(ASIR-V)to optimize the image quality in the arterial phase of chest enhanced CT scan.Methods 12 sets of the arterial phase Images were acquired using gemstone spectral imaging(GSI)mode in 62 adult patients who underwent chest enhanced CT scan.They included 1 set of 140 kVp polychromatic images(QC)and 11 sets of monochromatic images in 40-140 keV.The CNR and BHA of 12 sets of images were statistically analyzed with ANOVA and subjective scores were statistically analyzed with Rank Sum Test.Then the optimal monochromatic images with smaller artifacts and higher image quality were obtained.The optimal monochromatic images were reconstructed with ASIR and ASIR-V at 30%,50%and 70%levels respectively.6 sets of images were obtained and compared with QC and that monochromatic image under traditional reconstructed modes(FBP)with the same statistical methods as before.Results In FBP mode,The CNR of 80 keV images was 7.7±2.0,and it had no significant difference with QC images(P>0.05).The BHA in blood vessels was 44.4±22.0,which was lower than QC images(P<0.05).The subjective image quality score of 80 keV images was 4.50±0.621.There was no significant difference with QC images(P>0.05),and subjective score of artifact was 2.45±0.619,which was lower than QC images(P<0.05).80 keV group had lower artifact level and higher image quality.So 80 keV was chosen as the optimal monochromatic energy to be reconstructed with ASIR and ASIR-V.The CNR of 80 keV+50%ASIR-V groups was 13.9±4.3,which was higher than those of 140 kVp and 80 keV images in FBP(P<0.05).And their BHA in soft tissue and blood vessels had no significant a difference with QC images(P>0.05).The subjective score was 4.90±0.298,which was higher than that of the other groups(P<0.05).Conclusion Comparing with conventional chest contrast-enhanced CT images in arterial phase,80 keV+50%ASIR-V images can effectively eliminate the beam-hardening artifact and improve image quality.This mode can be used in routine enhanced CT examination.