[Differences of Energy Spectrum CT Findings between Small Cell Lung Cancer with Mediastinal Lymph Node Metastasis and Mediastinal Sarcoidosis].

Objective To compare the differences of energy spectrum CT between small cell lung cancer(SCLC)with mediastinal lymph node metastasis and mediastinal sarcoidosis.Methods Twenty-five SCLC patients with mediastinal lymph node metastasis(SCLC group)and 26 patients with mediastinal sarcoidosis(sarcoidosis group)confirmed by bronchoscopy and biopsy in Tangshan People's Hospital from January 2018 to June 2019 were selected as the research objects.The CT value,iodine concentration,water concentration and energy spectrum curve slope under different single energy levels were compared between SCLC group and sarcoidosis group.Results The single-energy CT values of 40-80 keV segments in the arterial phase of the SCLC group were significantly higher than those in the sarcoidosis group(all P <0.05).The single-energy CT values of 90-140 keV segments were not significantly different from those in the sarcoidosis group(all P >0.05).The single-energy CT values of 40-90 keV segments in venous phase of the SCLC group were significantly higher than those of the sarcoidosis group(all P <0.05),and the single-energy CT values of 100-140 keV segments were not significantly different from those of the sarcoidosis group(all P >0.05).The concentrations of iodine in the arterial phase and venous phase of the SCLC group were(11.56±4.06)µg/cm 3 and(13.39±0.87)µg/cm 3,respectively,which were significantly higher than those [(4.43±3.85)µg/cm 3,t=11.564,P=0.026;(7.23±2.71)µg/cm 3,t=13.653,P=0.021] in the sarcoidosis group.The concentrations of water in the arterial and venous phases of the SCLC group were(1040.67±5.62)mg/cm 3 and(1035.23±8.57)mg/cm 3,respectively,which showed no statistically significant difference compared with those [(1028.87±6.94)mg/cm 3,t=3.155,P=1.861;(1021.53±4.68)mg/cm 3,t=3.265,P=1.687] in the sarcoidosis group.The slopes of energy spectrum curve at 40-70 keV,70-100 keV and 100-140 keV in venous phase of the SCLC group were significantly higher than those of the sarcoidosis group(all P <0.05),whereas they showed no significant difference between the two groups in arterial phase(all P >0.05).Conclusion The differences between SCLC with mediastinal lymph node metastasis and mediastinal sarcoidosis can be shown on the single-energy CT values of 40-80 keV in arterial phase and 40-90 keV in venous phase,iodine concentrations in arterial phase and venous phase,and the slope of energy spectrum curve in venous phase.