双层探测器能谱CT在小肝癌显示中最佳单能量选择初步研究

Dual-layer detector computed tomography in small hepatocellular carcinoma:investigation of the optimal single energy value

目的探讨双层探测器能谱CT(dual-layer detector computedtomography,DLCT)在上腹部增强扫描的动脉期中小肝癌显示最佳的单能量值,实现在动脉期时对小肝癌的最优显示效果。方法回顾性分析本院行上腹部能谱CT增强检查,并在检查前后一周内,病理学确诊小肝癌的64例患者的能谱CT数据,应用Philips能谱工作站,将患者动脉期的120kVp混合能量图像(A组)与不同单能量的图像(40~100keV和200keV)(B组)分别进行两两比较。测量各组图像中小肝癌、同层图像的肝实质的CT值,计算对比噪声比(CNR)、信噪比(SNR)、图像背景噪声值及图像质量主观评分,进行统计学分析。结果随着单能量值升高,动脉期时相对应的CNR、SNR、图像背景噪声值及图像质量主观评分值均呈下降趋势,当能谱CT单能量水平处于40~60keV区间时,病灶的CNR值(4.09±2.34~1.75±1.16)、SNR值(9.09±4.21~7.07±2.48)、图像质量主观评分(2.90±0.25~2.78±0.42)均优于120kVp混合能量图像(0.96±0.82,5.36±1.61,2.53±0.51),而背景噪声无明显差异。在单能量处于40KeV水平时,病灶的CNR值(4.09±2.34)、SNR值(9.09±4.21)、图像的主观评分(2.90±0.25)最高,对小肝癌病灶显示最佳。结论DLCT在40keV单能量成像时小肝癌病灶具有最佳的CNR、SNR及良好的图像质量评分,能够在动脉期更好的显示小肝癌病灶。

Objective To investigate the optimal single energy value of dual-layer detector computed tomography(DLCT)for small hepatocellular carcinoma during enhanced upper abdominal scan,so as to achieve the optimal display effect on small hepatocellular carcinoma in the arterial phase.Methods We retrospectively analyzed the energy spectrum CT data of 64 patients with small hepatocellular carcinoma in our hospital,which were diagnosed by pathology within one week before or after CT examination.Using philips energy spectrum workstation,the mixed energy images of 120 kVp(group A)were compared with the single energy images(40~100 keV and 200 keV)(group B).The CT values of small hepatocellular carcinoma and liver parenchyma in the same-layer were measured.The contrast-to-noise ratio(CNR),signal-to-noise ratio(SNR),image background noise value and image quality subjective score were calculated and analyzed statistically.Results As the level of single energy increase,the CNR,SNR,image background noise and subjective score of image quality all decreased.When the single energy level was in the range of 40~60 keV,the CNR(4.09±2.34~1.75±1.16),SNR(9.09±4.21~7.07±2.48),imagequalityscores(2.90±0.25~2.78±0.42)were better than120 kVp mixed energy images(0.96±0.82,5.36±1.61,2.53±0.51),and there was no significant difference in background noise.The CNR、SNR and image quality scores values were the highest at the single energy level of 40 keV,and the small hepatocellular carcinoma lesions were best displayed.Conclusion The best CNR,SNRand image quality of small hepatocellular carcinoma were obtained at 40 keV single-energy imaging by DLCT,and the small hepatocellular carcinoma could be better displayed in arterial phase.