The Clinical Application Of CT Energy Spectrum Imaging In The Diagnosis Of Lymph Node Metastasis Of Primary Liver Cancer

Objective:To investigate the value of CT energy spectrum imaging in the diagnosis of lymph node metastasis of primary liver cancer.Materials and methods:1.Choose the third affiliated hospital of Guangxi Medical University from May 2018 to February 2020 to diagnose primary liver cancer（including:（1）hepatocellular carcinoma,HCC;（2）intrahepatic cholangiocarcinoma,ICC;（3）combined hepatocellular-cholangiocarcinoma,CHC）patients who met the following conditions were taken as study subjects:（1）no contrast allergic reaction;（2）no clinical anti-tumor treatment such as radiotherapy,chemotherapy or surgery related to primary liver cancer before CT enhancement examination;（3）consent and cooperate with CT gemstone spectral imaging（GSI）examination,and signe informed consent approved by the ethics committee of our hospital before examination;（4）patients who plan to be hospitalized in our hospital and undergo limited surgical resection;（5）complete medical records and pathological information.A total of 42 patients were included in this study,including 34males and 8 females,aged 37-79 years,with a median age of 52 years.All included cases were confirmed by surgical pathology.According to the pathological type of primary lesions,there were 30 cases of HCC,12 cases of ICC and 0 cases of CHC.A total of 72 lymph nodes were resected for postoperative pathological examination,including 29 metastatic lymph nodes（10HCC metastases,19 ICC metastases）and 43 non-metastatic lymph nodes.2.GE 64-row gemstone energy spectrum CT（Discovery CT 750 HD）was used to scan the upper abdomen of patients who are clinically considered for diagnosis of primary liver cancer with CT plain scan and balanced phase under conventional parameters,enhanced scanning in arterial phase and portal phase using GSI mode.Two associate chief radiologists were divided into two groups to perform image analysis under unknown pathology.The intrahepatic lesions and perihepatic lymph nodes were observed and analyzed.The lymph nodes of interest that met the inclusion criteria were marked and could undergo postoperative pathological examination were obtained,and their morphological characteristics were recorded.GSI View software of AW4.6 workstation was used to measure iodine concentration（IC）and iodine concentration of abdominal aorta at the same level of primary liver cancer lesions and interested lymph nodes in the enhanced scanning arterial phase,portal phase,and to calculate normalized iodine concentrations（NIC）=IC/iodine concentration of abdominal aorta at the same level;the energy spectrum curve of the primary liver cancer and the lymph node of interest was delineated,and calculate the slope of the energy spectrum curve(λ_HU)=（40 ke V CT value-100 ke V CT value）/60.3.According to the postoperative pathological results,the interested lymph nodes were divided into two groups:metastatic lymph nodes and non-metastatic lymph nodes.Measured IC,NIC,andλ_HUof primary liver cancer and lymph nodes in both groups,and the measurement data were recorded as"mean±standard deviation",and SPSS20.0 statistical software was used for data analysis.To test the normality and homogeneity of variance of the research data,two independent sample t-test was used to treat the homogeneity of variance data,and the approximate t-test was used to test the variance of non-homogeneity,P<0.05 was statistically significant.Receiver operating character-ristic（ROC）curve was used to analyze the spectral parameters with statistical differences between metastatic and non-metastatic lymph node groups,calculate the Youden index（YI）and used to determine the optimal cut-off value of each spectral quantitative parameter,and the corresponding sensitivity,specificity and area under the curve（AUC）of IC,NIC andλ_HUfor differentiating lymph node metastasis of primary liver cancer were obtained.Results:1.The sensitivity and specificity of diagnosing metastatic lymph nodes with the maximum short diameter of lymph nodes>10 mm were 75.86%（22/29）and53.49%（23/43）,respectively,with a coincidence rate of 62.5%（45/72）,a positive predictive value of 52.38%（22/42）,and a negative predictive value of 76.67%（23/30）.The accuracy of diagnosing metastatic lymph nodes was improved by combining the short diameter of lymph nodes with other morpholo-gical characteristics.2.The corresponding energy spectrum parameters were compared between the primary liver cancer,metastatic lymph node group and non-metastatic lymph node group.The IC,NIC,andλ_HUof primary liver cancer in arterial phase and portal phase were 13.17±3.28,0.16±0.06,1.43±0.15,20.31±4.16,0.41±0.08 and1.94±0.23,respectively.The corresponding energy spectrum parameters in the metastatic lymph node group were 12.90±3.24,0.15±0.04,1.45±0.16,19.98±3.52,0.41±0.08 and 1.94±0.22,respectively;those in the non-metastatic lymph node group were 19.32±3.78,0.24±0.06,1.98±0.45,28.11±5.40,0.54±0.13 and 2.19±0.24,respectively.The energy spectrum parameters of non-metastatic lymph node group were larger than those of primary liver cancer and metastatic lymph node group,and the differences between non-metastatic lymph node group and primary liver cancer,non-metastatic lymph node group and metastatic lymph node group were statistically significant（P<0.05）.There was no significant difference in energy spectrum parameters between metastatic lymph node group and primary liver cancer（P>0.05）.3.Compared with IC,NIC andλ_HUin arterial phase and portal phase,the energy spectrum parameters of HCC were 13.91±3.29,0.17±0.07,1.47±0.13,18.79±3.58,0.38±0.06 and 1.85±0.19;the energy spectrum parameters of ICC were 11.32±2.49,0.14±0.02,1.32±0.13,24.11±2.98,0.49±0.06 and 2.14±0.19,respectively;The energy spectrum parameters of HCC metastatic lymph node group were 14.59±3.43,0.16±0.04,1.53±0.17,17.71±2.99,0.35±0.04,1.83±0.20;those of ICC metastatic lymph node group were 12.01±2.83,0.14±0.03,1.40±0.14,21.12±3.24,0.44±0.08,2.00±0.21.The energy spectrum parameters of HCC in arterial phase were larger than those of ICC,and the energy spectrum parameters of ICC in portal phase were larger than those of HCC.The same characteristics were also observed in the comparison of energy spectrum parameters of metastatic lymph nodes in HCC and ICC.The corresponding energy spectrum parameters between HCC and ICC,HCC metastatic lymph node group and ICC metastatic lymph node group were compared,and the difference was statistically significant（P<0.05）.4.The parameters of HCC energy spectrum in the arterial phase were larger than those in the normal liver parenchyma,while those in the portal phase were smaller than those in the normal liver parenchyma,and the comparison of the energy spectrum parameters was statistically significant（P<0.05）.The ICC spectral parameters in arterial phase and portal phase were smaller than those in normal liver parenchyma.There was no significant difference between IC and NIC in arterial phase（P>0.05）,and there was significant difference between the energy spectral parameters in arterial phase and portal phase（P<0.05）.5.The energy spectrum parameters(IC,NIC andλ_HU)with statistical difference in arterial phase and portal phase were analyzed by ROC curve,which indicated that the diagnostic efficiency of NIC in arterial phase was the highest,and the corresponding YI was 0.746.When the NIC in arterial phase was less than 0.175,the sensitivity,specificity and AUC for judging lymph node metastasis in primary liver cancer were 88.4%,86.2%and 0.898,respectively.Conclusion:1.CT-GSI images can well balance image quality and lesion display at 70ke V single energy level;the accuracy of CT morphology in the diagnosis of metastatic lymph nodes is not high.2.The energy spectrum quantitative parameters(IC,NIC andλ_HU)between HCC and ICC,between HCC metastatic lymph nodes and ICC metastatic lymph nodes,between primary liver cancer and non-metastatic lymph nodes group,and between metastatic and non-metastatic lymph nodes were significantly different（P<0.05）,suggesting that there was no homology among the groups.There was no significant difference in the quantitative parameters of energy spectrum(IC,NIC andλ_HU)between primary liver cancer and metastatic lymph nodes group（P>0.05）,suggesting that the two have homology.CT-GSI can provide important reference value for the identification of the source of lesions and the difference of blood supply between lesions.3.Quantitative parameters of energy spectrum(IC,NIC andλ_HU)in arterial phase and portal phase are helpful for the diagnosis of lymph node metastasis of primary liver cancer.Among them,NIC in arterial phase has the greatest diagnostic value,with AUC=0.898,YI=0.746 and diagnostic threshold of NIC<0.175.The sensitivity and specificity of this threshold for the diagnosis of lymph node metastasis of hepatocellular carcinoma are high（88.4%and 86.2%,respectively）.