摘要
目的 探讨双层探测器光谱 CT 联合半量对比剂在门静脉期检测肝转移瘤的临床应用价值.资料与方法 前瞻性收集2021年11月—2022年6月于福建医科大学附属第一医院行肝脏增强CT检查确诊肝转移瘤的96例患者,采用基于体表面积的给药计算方法平均分为两组:常规对比剂剂量组48例,给予碘量为18.6 gI/m2体表面积,在门静脉期重建生成常规混合能量图像(CI);半对比剂剂量组48例,给予碘量为9.3 gI/m2体表面积,在门静脉期重建生成40～70 keV(间隔5 keV)虚拟单能级图像(VMI).比较两组的图像噪声、CT值、对比噪声比,采用5分法对图像质量评分,并评价2名医师间主观评分的一致性.结果 40～70 keV VMI噪声分别为(10.26±1.38)Hu、(9.59±1.35)Hu、(9.15±1.31)Hu、(8.80±1.32)Hu、(8.58±1.31)Hu、(8.40±1.31)Hu、(8.27±1.33)Hu,CI噪声为(10.86±1.13)Hu,45～70 keV VMI均低于CI(t=-3.885、-5.343、-6.449、-7.180、-7.756、-8.132,P均<0.001),40 keV VMI与CI差异无统计学意义(t=-1.800,P>0.05).随着能级降低,正常肝实质CT值及正常肝实质、肝转移瘤对比噪声比逐渐增加,40 keV 时最高,为(148.31±21.34)Hu、8.81±2.83、8.18±2.85;45 keV 时为(130.10±16.95)Hu、7.66±2.46、7.48±2.55;50 keV时为(116.19±13.55)Hu、6.60±2.08、55.40±13.77;CI为(118.02±7.02)Hu、5.69±1.11、5.77±1.41;40 keV、45 keV VMI均显著高于CI(t=3.804、4.883、4.462,P均<0.05;t=2.854、3.465、3.378,P均<0.05),50 keV VMI与CI差异无统计学意义(t=-0.612、1.739、2.208,P>0.05).40～50 keV VMI整体图像质量主观评分均高于CI(t=9.628、7.508、3.514,P<0.05).2名医师对两组患者在图像对比、图像噪声、整体图像质量间主观评分一致性较好(Kappa=0.766、0.749、0.661,P<0.05).结论 在减少50%对比剂剂量门静脉期图像上,40～50 keV VMI比CI图像能够提供更好的图像质量,肝转移瘤的显示能力更强.
Abstract
Purpose To explore the clinical application value of dual-layer detector spectral CT combined with half volume contrast agent in detecting the liver metastases in portal vein phase.Materials and Methods Ninety-six patients with liver metastases diagnosed by liver enhanced CT in the First Affiliated Hospital of Fujian Medical University from November 2021 to June 2022 were prospectively studied.They were randomly divided into two groups by using the contrast agent administration calculation method based on body surface area.The conventional polyenergetic image(CI)of patients in the conventional contrast agent group(48 cases with 18.6 gI/m2 body surface area iodine contrast agent)was constructed in the portal vein phase,and the 40-70 keV(5 kiloelectron voltage)virtual monoenergetic imaging(VMI)was reconstructed for patients in the semi contrast agent dose group(48 case with 9.3 gI/m2 body surface area iodine contrast agent).The image noise,CT value and contrast noise ratio in the two groups were measured and compared.Besides,the image quality was scored with a 5-point method,and the consistency of subjective scores between two radiologists were evaluated.Results The VMI noise at 40-70 keV was(10.26±1.38)Hu,(9.59±1.35)Hu,(9.15±1.31)Hu,(8.80±1.32)Hu,(8.58±1.31)Hu,(8.40±1.31)Hu and(8.27±1.33)Hu;while the CI noise was(10.86±1.13)Hu.It revealed that the VMI noise at 45-70 keV was lower than the CI noise(t=-3.885,-5.343,-6.449,-7.180,-7.756 and-8.132,P<0.001).There was no significant difference between VMI and CI noises at 40 keV(t=-1.800,P>0.05).With the decrease of energy level,CT value of normal liver parenchyma,and contrast noise ratio values of liver parenchyma and liver metastases gradually increased,at the 40 keV level,the values of which were(148.31±21.34)Hu,8.81±2.83 and 8.18±2.85;at the 45 keV level,the values were(130.10±16.95)Hu,7.66±2.46 and 7.48±2.55;at the 50 keV level,the values were(116.19±13.55)Hu,6.60±2.08 and 55.40±13.77,reaching the highest at 40 keV level,while the CI values were(118.02±7.02)Hu,5.69±1.11 and 5.77±1.41.Therefore,the value of 40 keV and 45 keV VMI was significantly higher than CI(t=3.804,4.883,4.462,all P<0.05;t=2.854,3.465,3.378,all P<0.05),respectively.There was no significant difference between 50 keV VMI and CI(t=-0.612,1.739,2.208,P>0.05).The subjective score in the overall quality of VMI images was higher than that of CI at 40-50 keV(t=9.628,7.508,3.514,P<0.05).The subjective scores of the two physicians were good consistent among image contrast,image noise and overall image quality(Kappa=0.766,0.749 and 0.661,P<0.05),respectively.Conclusion VMI at 40-50 keV can provide better image quality and display ability of liver metastases than CI images at portal vein phase with a 50%reduction in contrast agent dose.
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