双层探测器光谱CT增强扫描中70 keV单能量图像与常规图像的质量对比

Quality comparison between 70 keV virtual monoenergetic image and conventional image in dual-layer spectral detector CT enhanced scanning with double layer detector

目的:对比分析双层探测器光谱CT增强扫描中70 keV单能量图像(VMI)与常规图像(CI)的质量差异。方法:回顾性分析2021年10月—2022年1月在中山大学肿瘤防治中心飞利浦双层探测器光谱CT上行胸腹部增强扫描患者的动脉期影像资料35例。利用动脉期能谱数据(SBI)重建出常规图像(CI)及70 keV单能量图像(VMI),分别测量并记录CI及VMI图像气管隆突水平层面降主动脉、肺组织、竖脊肌、脂肪、空气的平均CT值及标准差(SD),计算图像的信噪比(SNR)、对比噪声比(CNR)。结果:VMI组降主动脉CT值显著高于CI组(P<0.05);VMI组肺组织、竖脊肌、脂肪CT值显著低于CI组(P<0.05);VMI组与CI组空气CT值无显著差异(P>0.05);VMI组SD除空气外都比CI组低,差异具有统计学意义(P<0.05);VMI组空气SD显著高于CI组(P<0.05);VMI组SNR除空气外都比CI组高,差异具有统计学意义(P<0.05);VMI组空气SNR显著低于CI组(P<0.05);70 keV VMI组CNR均显著高于CI组(P<0.05)。结论:双层探测器光谱CT胸部增强扫描中,70 keV单能量能降低图像噪声,提高SNR、CNR,70 keV单能量图像质量优于常规图像。

Objective To compare and analyze the quality difference between 70 keV virtual monoenergetic image(VMI)and conventional image(CI)in the dual-layer spectral detector CT enhanced scan.Methods A retrospective analysis was performed on the arterial phase images of 35 patients who underwent chest and abdominal enhancement with Philips dual-layer spectral detector CT in Sun Yat-Sen University Cancer Center from October 2021 to January 2022.Conventional images(CI)and 70 keV virtual monoenergetic image(VMI)were reconstructed using arterial phase spectral based image(SBI),Mean CT values and standard deviation(SD)of descending aorta,lung tissue,erector spinae,fat and air at the level of tracheal carina were measured and recorded on CI and VMI images,respectively,To calculate the signal-to-noise ratio(SNR)and contrast-to-noise ratio(CNR)of an image.IBM SPSS24.0 software was used for comparative analysis.Results The CT value of descending aorta in VMI group was significantly higher than that in CI group(P<0.05);The CT values of lung tissue,erector spinalis muscle and fat in VMI group were significantly lower than those in CI group(P<0.05);There was no statistical difference in air CT values between VMI group and CI group(P>0.05);The VMI group SD is lower than the CI group except air,the difference was statistically significant(P<0.05);The air SD of the VMI group is significantly higher than that of the CI group(P<0.05).The SNR of VMI group was higher than that of CI group except air,the difference was statistically significant(P<0.05);The air SNR of the VMI group is significantly lower than that of the CI group(P<0.05);The 70 keV CNR of the VMI group is significantly higher than the CI group(P<0.05).Conclusion In dual-layer spectral detector CT chest enhancement scan,70 keV virtual monoenergetic can reduce image noise,improve SNR,CNR.70 keV virtual monoenergetic image quality is better than conventional images.