能谱CT单能量技术优化头颈CTA图像质量研究

Research on Optimization of Head and Neck CTA Image Quality by Spectrum CT Optimal Monochromatic Image Technique

目的评估宝石能谱CT单能量技术对头颈CT血管造影(CT Angiography,CTA)图像质量优化价值。方法收集本院拟行头颈CTA检查病人30例,增强使用能谱扫描。扫描完成后,分别重建60、65、70、75、80 keV共5组单能量图像,将图像传入AW4.6工作站,进行MPR、VR、CPR重建。两名经验丰富的影像医师对图像质量行4分制评分,然后使用Kappa检验对比两名医师评分一致性;测量主动脉弓、双侧颈总、双侧颈内、双侧大脑中动脉、胸锁乳突肌、脑实质的CT值,以及双侧颈总、颈内、胸锁乳突肌、脑实质SD值,对称性血管求其CT、SD值均值,而后计算出血管的信噪比(Signal to Noise Ratio,SNR)和对比噪声比(Contrast to Noise Ratio,CNR)。对5组数据进行统计比较。结果5组图像SNR、CNR和主观评分,有统计差异(P<0.05)。两名影像医师评分一致性较好,Kappa值>0.800。60 keV组和65 keV组的SNR、CNR也是最高,这两组所测量血管的CT值均大于300 HU,有利于血管显示。60 keV组(3.64±0.49)分的主观评分最高。结论能谱CT单能量技术可提升头颈CTA图像质量,头颈CTA成像最优单能量水平位于60 keV。

Objective To study the use of the optimal monochromatic image technique in dual-energy Spectral imaging to optimize the image quality in head and neck CT angiography(CTA).Methods 30 patients were selected to undergo head and neck CTA using Spectral scan mode.After scanning,5 sets of monochromatic images at 60,65,70,75 and 80 keV were reconstructed.Images were transferred to AW4.6 workstation for MPR,VR and CPR reconstruction.Two experienced radiologists evaluated the subjective image quality with a 4-point scoring system.The consistency of the scores were evaluated by Kappa test.The CT values and their standard deviations of the aortic arch,common carotid artery,internal carotid artery,middle cerebral artery,cleidomastoid,and brain parenchyma were measured.The signal to noise ratio(SNR)and contrast to noise ratio(CNR)of the cervical vessels were calculated.Measurements were statistically compared between the five groups.Results The differences of SNR,CNR and subjective image scores among the 5 groups were statistically significant(P<0.05).The scores of the two radiologists were consistent with Kappa value>0.800.SNR and CNR of the 60 keV group and the 65 keV group were also the highest,and the CT values of the vessels measured in these two groups were all greater than 300 HU,which was conducive to vascular display.The 60 keV group had the highest subjective score,which was(3.64±0.49)score.Conclusion Spectrum CT Optimal Monochromatic Image Technique can improve the image quality of head and neck CTA,and the optimal energy level of head and neck CTA imaging is 60 keV.