宝石CT肺动脉能谱成像最佳单能量图像的选择

Optimization of Monochromatic Imaging in Energy Spectral CT Pulmonary Angiography

目的:探讨CT能谱成像(GSI)技术智能跟踪法肺动脉成像最佳单能量图像的选择;方法:44例(体质指数BMI<26)可疑肺栓塞患者行宝石CT GSI技术肺动脉成像,获取40~75 keV间距为5 keV的8组单能量图像,分别对8组图像进行同层肺动脉主干CT值和SD值、背景噪声(BN)、背阔肌CT值的测量,计算并比较各组单能量图像的信噪比(SNR)、对比噪声比(CNR)、噪声值,并对图像质量进行主观评价、评分,对结果进行统计学分析;结果:CT值(肺动脉主干)随keV减小而增大;65keV的图像噪声值(17.22±2.84)最低(P<0.05);60 keV和65 keV组图像的CNR值亦明显高于其他组(P<0.05),该两组间差异无统计意义(P=0.318);60 keV组和65 keV组图像的SNR值明显高于其他组(P<0.05),该两组间差异无统计学意义(P=0.679);60keV的图像主观评分(3.78±0.26)最高(P<0.001)。结论:60~65keV是宝石CT GSI肺动脉成像的最佳单能量图像。

Purpose： To investigate the effect of dual energy spectral CT （DEsCT） with bolus-tracking technique on the image quality of computed tomography pulmonary angiography （CTPA）, and to determine the optimal monochromatic energy level. Methods： Forty-four patients underwent CTPA on a 64-slice CT scanner （Discovery CT 750 HD, GE healthcare） with DEsCT mode. The dosage and flow rate of contrast-agent（Visipaque 270; 270 mg/mL） were adapted to the body mass index （BMI）. Eight sets of monochromatic images （40-75 keV） were reconstructed. The CT value and noise of the main pulmonary artery （PA）, latissimus dorsi （LD） and background noise （BN） of the same slice were measured. The signal-to-noise ratio （SNR） and the contrast-to-noise ratio （CNR） were calculated. The image quality of each monochromatic image set was assessed with a 4-point scale. The results were compared with one-way ANOVA and Wilcoxon signed-rank test. Results： The CT value of the main pulmonary artery increased as the monochromatic level decreased. The image of 65 keV had the lowest noise （17.22~2.84） among the 8 sets of monochromatic images （P〈 0.05）. The SNR and CNR of 60 keV and 65 keV were higher than the other monochromatic images （both P〈 0.05）. The CNR and SNR had no significant difference between images of 60 keV and 65 keV （P=0.318, P=0.679）. The subjective score of images of 60 keV （3.78~0.26） were ranked the highest among all monochromatic images （P〈0.001）. Conclusion： Monochromatic images at 60-65keV provide the best image quality for DEsCT of CTPA.