宝石高清CT不同重建算法对冠状动脉细小分支CTA图像质量影响的初步研究

Initial study about image quality of small branches in coronary CTA:using different reconstruction algorithm by high definition CT

目的:探讨宝石高清(HD)CT四种重建算法(Standard,Detail,HD standard,HD detail)对冠状动脉细小分支CT血管造影(CTA)图像质量的影响。方法:30例采用宝石HDCT完成CCTA检查,且结果为冠状动脉主要分支面积狭窄率<25%病例入组。采用Auto Coronary Analysis获得四种重建算法下窦房结动脉(SANA)、右圆锥支(RCB)、第一前室间隔支(FSB)的曲面重组(CPR)图像,同时自动获得各细小分支管径平均值。在75%R-R间期原始横断面图像上,分别测量并计算上述细小分支的管腔CT值、噪声、信噪比(SNR)和对比噪声比(CNR)。采用单因素方差分析比较四种重建算法上述客观指标是否存在统计学差异。对于有统计学差异的指标采用LSD进行Post Hoc组内两两比较。对各细小分支四种重建算法CPR图像质量进行评分,为4分制(1分血管边缘模糊,2分血管边缘清楚,3分血管边缘锐利,4分血管边缘十分锐利)。采用配对Wilcoxon rank sum test分析四种重建算法冠状动脉细小分支CPR图像质量评分是否存在统计学差异。结果:①冠状动脉上述3个细小分支管径均小于2 mm。②四种重建算法组间比较,管径(F=3.905,P=0.011)、噪声(F=14.956,P=0.000)具有统计学差异;而管腔CT值(F=1.067,P=0.366)、SNR(F=1.909,P=0.132)、CNR(F=2.320,P=0.079)无统计学差异。③冠状动脉细小分支管径的四种重建算法组内两两比较,Standard与Detail、Detail与HD Standard、HD Standard与HD Detail没有统计学差异(P>0.05),而其他算法间两两比较均存在统计学差异(P<0.05)。④冠状动脉细小分支图像噪声的四种重建算法组内两两比较,Standard与Detail没有统计学差异(P>0.05),而其他算法间两两比较均存在统计学差异(P<0.05)。⑤按照Standard、Detail、HD Standard和HD Detail的顺序,冠状动脉细小分支管腔CT值、噪声和CPR图像质量评分呈上升趋势,而管径、SNR、CNR呈下降趋势。⑥四种重建算法Standard、Detail、HD Standard和HD Detail冠状动脉细小分支CPR图像质量评分分别为1分、2分、3分和4分,存在统计学差异(Z=-10.583,P=0.000)。结论 :对于管径<2 mm的冠状动脉细小分支,随着重建算法空间分辨率的提高,CPR图像质量明显提高,而横轴位图像的SNR和CNR呈不显著下降趋势。宝石HDCT可以实现对冠状动脉细小分支的良好显示为不同临床需要提供影像学支持。

Objective： To access image quality of small branches of coronary computed tomography angiography（CCTA） using different reconstruction algorithm（including Standard, Detail, HD standard, HD detail） by high definition CT（HDCT）. Methods： Thirty patients underwent CCTA by HDCT, whose main branches of coronary artery area stenosis rate〈25%, were enrolled. Curved planar reconstruction（CPR） images and artery diameter of 90 small branches about four reconstruction algorithms （Standard, Detail, HD Standard and HD Detail）, each patient including sinu atrial nodal artery （SANA）, right conus branch （RCB）, first septal branch（FSB）, were obtained using Auto Coronary Analysis of GE AW4.6. CT value, noise, signal noise ratio （SNR）, and contrast-to-noise ratio （CNR） of above small branches about four reconstruction algorithms were measured and calculated on original axial image of 75%R-R interval. Above Objective indicators among four reconstruction algorithms were analyzed by one-way analysis of variance （ANOVA）. The CPR image quality with a 4-point grading scale （1： Arterial edge was fuzzy; 2： Arterial edge was clear; 3： Arterial edge was sharp; 4： Arterial edge was very sharp） was evaluated by two experienced radiologists. CPR image quality among four reconstruction algorithms were performed with paired Wileoxon rank sum test. Results： （1）The average diameter of above small branches was less than 2 mm no matter which reconstruction algorithm was selected. （2）There were statistical differences in diameter（F=3.905, P=0.011）, noise（F=14.956, P=0.000） among four reconstruction algorithms. There were no statistical differences in CT value（F=1.067, P=0.366）, SNR（F=1.909, P=0.132）, and CNR（F=2.320, P=0.079） among reconstruction algorithms. （3）Muhiple comparisons between four reconstruction algorithms on diameter of small branches of the coronary arteries and image noise were made. There were no statistical differences on diameter of small branches of the coronary arteries between Standard and Detail, Detail and HD Standard, HD Standard and HD Detail（P〉0.05）. There. were statistical differences on diameter of small branches of the coronary arteries between any other two reconstruction algorithms （P〈0.05）. （4）There were no statistical differences on image noise between Standard and Detail （P〉0.05）. There were statistical differences on image noise between any other two reconstruction algorithms （P〈0.05）. （5）According to the order of Standard, Detail, HD standard, and HD detail; diameter, SNR and CNR were decreasing successively. However CT value and noise were increasing successively. （6）There were statistical differences in CPR image quality（Z=-10.583, P=0.000） between any two groups. Conclusion： For small branches of the coronary arteries（diameter〈2 mm）, with improving of reconstruction algorithm on spatial resolution, CPR image quality is increasing successively. However, SNR and CNR of axial original image are decreasing. In short, excellent image of small branches of the coronary arteries can be obtained by HDCT to realize different clinic requirements.