基于双层探测器光谱CT定量参数分析直肠癌生物学特征

Analysis of biological characteristics of rectal cancer based on quantitative parameters obtained by dual-layer detector spectral CT

目的:探讨双层探测器光谱CT定量参数与直肠癌脉管神经侵犯等病理特征之间的关系,筛选诊断脉管神经侵犯的最佳双层探测器光谱CT定量参数和最佳扫描期相。方法:前瞻性将2020年6月-2021年1月在本院行双层探测器光谱CT双期扫描且经手术病理证实的70例直肠癌患者纳入本研究。分析直肠癌动脉期和静脉期的光谱CT参数,包括120 kVp图像(PI)、40 keV虚拟单能级图像(VMI)和虚拟平扫(VNC)图像上的CT值、无水碘密度、标准化碘密度(NIC)和有效原子序数(Eff-Z)。脉管神经侵犯、肿瘤分化程度及淋巴结转移情况经病理检测获得。采用独立样本t检验比较动脉期和静脉期各项光谱CT参数在直肠癌不同病理特征分组间的差异。采用受试者工作特征(ROC)曲线分析光谱CT参数对脉管神经侵犯等病理特征的诊断效能。结果:动脉期无水碘密度、NIC和Eff-Z在血管侵犯组和未侵犯组之间,以及在淋巴管侵犯组和未侵犯组之间的差异均有统计学意义(P<0.05)。血管侵犯组和淋巴管侵犯组的静脉期CT值_(40 keV-VMI)、无水碘密度、NIC和Eff-Z均分别高于血管未侵犯组和淋巴管未侵犯组,组间差异均有统计学意义(P<0.05)。静脉期Eff-Z在有和无神经侵犯组、不同分化程度组及有和无淋巴结转移组之间比较,差异均有统计学意义(P<0.05)。动脉期无水碘密度、CT值_(40 keV-VMI)、NIC和Eff-Z评价直肠癌淋巴管浸润的AUC分别为0.74、0.69、0.75和0.74,评价直肠癌血管侵犯的AUC分别为0.73、0.68、0.75和0.75;静脉期无水碘密度、CT值_(40 keV-VMI)、NIC和Eff-Z评价淋巴管浸润的AUC分别是0.68、0.68、0.75和0.74,评价直肠癌血管浸润的AUC分别是0.71、0.76、0.76、0.72。结论:光谱CT定量参数对直肠癌脉管侵犯具有较好的诊断效能,静脉期是反映直肠癌神经侵犯、分化程度及淋巴结转移的最佳期相,光谱CT可作为术前评估直肠癌生物学行为的一种无创的影像学检查方法。

Objective:To investigate the relationship between quantitative parameters of dual-layer detector spectral CT and pathological features such as vascular nerve invasion in rectal cancer,and to explore the optimal parameters and scan phase for diagnosis of vascular nerve invasion.Methods:A total of 70 patients with rectal cancer who underwent spectral CT scan from June 2020 to January 2021 were included.The spectral CT parameters including CT value on 120kVp polyenergetic image(PI),40keV virtual monoenergetic images(VMI)and virtual non-contrast(VNC)images,anhydrous iodine density,normalized iodine density(NIC)and Eff-Z at arterial and venous phases of rectal cancer were measured.Vascular nerve invasion,tumor differentiation and lymph node metastasis were obtained by pathological examination.Independent sample t-test was used to compare the diffe-rences of spectral CT parameters between arterial phase and venous phase in different pathological features of rectal cancer.Receiver operating characteristic curve(ROC)was used to analyze the diagnostic efficacy of spectral CT parameters for pathological features such as vascular nerve invasion.Results:There were significant differences(all P<0.05)in anhydrous iodine density,NIC and Eff-Z in arterial phases between the vascular invasion group and the non-vascular invasion group,as well as between the lymphatic invasion group and the non-lymphatic invasion group.The CT value on 40keV VMI(CT_(40keV-VMI)),anhydrous iodine density,NIC and Eff-Z of vascular-invasion group and lymphatic-invasion group in venous phases were significantly higher than those of non-vascular-invasion group and non-lymphatic-invasion group(all P<0.05).Eff-Z in venous phase showed significant difference in different pathological states of nerve invasion,lymph node metastasis and differentiation degree(all P<0.05).In arterial phase,the area under curve(AUC)of anhydrous iodine density,CT_(40keV-VMI),NIC and Eff-Z in evaluating lymphatic infiltration of rectal cancer was 0.74,0.69,0.75 and 0.74,respectively;and the AUC of the four parameters for evaluating vascular invasion was 0.73,0.68,0.75 and 0.75,respectively.In the venous phase,the AUC of the four parameters for diagnosis of lymphatic infiltration was 0.68,0.68,0.75 and 0.74,respectively;and in evaluating vascular invasion,the AUC was 0.71,0.76,0.76 and 0.72,respectively.Conclusion:Spectral CT has good diagnostic efficacy in the diagnosis of vascular invasion of rectal cancer.Venous phase is the optimal period phase to reflect the degree of nerve invasion,differentiation and lymph node metastasis.Spectral CT can be used as a non-invasive imaging examination method to evaluate the biological behavior of rectal cancer before surgery.