The Value Of Dual-source CT In Differential Diagnosis Of Adrenal Lipid-poor Adenomas And Small Metastasis

Objective: To explore the value of the third-generation dual-source CT energy spectrum curves and quantitative analysis of iodine concentration in the differential diagnosis of adrenal lipid-poor adenoma and small metastasis.Materials and Method: We retrospectively analyzed 53 patients with 57 lesions(29 pathologically proven,CT value >10HU,and 24 metastases proven by follow-up for more than 6 months or pathology)performed with third-generation dual-source CT examination in our hospital from June 2017 to March 2018.Adrenal lipid-poor adenoma total of 29 cases with 30 lesions.A total of 24 metastasis tumors with 27 lesions.All patients underwent plain and enhanced scans,except for 6 of 27 Metastatic tumors without enhanced.All cases adopted the third-generation dual-source CT dual-energy scan mode.Images were analyzed and processed at the Siemens workstation Syngo via:(1)CT value of the lesions on mixed energy images of adrenal lipid-poor adenoma and metastases on plain and enhanced scan(in arterial phases and venous phases)were measured.(2)Applying the Mono+(Monoenergetic plus)program,CT values of each energy from 40 to 190 ke V were measured and the energy spectrum curves were obtained.The slope(K)of the spectrum curve was calculated.(3)Using Liver VNC(Virtual non-contrast)post-processing program,iodine concentration of arterial phase and venous phase were measured and Calculate normalized iodine concentrations.Results:1.CT value of the two groups on mixed energy There were no statistical difference of CT values between adrenal lipid-poor adenoma and metastases on plain scans(p=0.062).Mean CT values of adrenal lipid-poor adenoma and metastases were(28.64±5.55)Hu and(31.84±5.79)Hu.Mean CT values of adrenal lipid-poor adenoma and metastases during arterial phase were(60.54±17.75)Hu,(57.48±11.99)Hu,while in venous phase,CT values were(54.48±10.20)Hu,(63.93±14.17)Hu.There were no statistical difference of CT values between the two groups in arterial phases statistically(P =0.555).The CT value of metastases was significantly higher than that of adipose adenomas in venous phase(P =0.017).2.CT values,energy spectrum curve,and the slope of spectrum curve of different lesions in both groups There were significant difference statistically in single-energy CT values of lesions at the level of 40 to 120 ke V between two groups(P <0.05).It showed no significant difference in the single-energy CT values at the level of 130 to 190 ke V(P >0.05).The CT value of adrenal metastases was higher than that of adrenal lipid-poor adenoma.The lower the ke V,the greater the difference in CT values between the two groups.The single-energy diagnostic efficiency of 40 ke V is the best.The CT values of the two groups coincided with the increase of ke V.The spectrum curve of adrenal lipid-poor adenoma were increment curve(K ? 0.1)and straight curve(-0.1 <K <0.1),with a total of 27(90%);All of the metastases spectrum curve showed a decrement curve,mainly with rapid changes(K?-0.1),a total of 23 cases(85.2%).There was statistically significant difference between the slopes of the spectrum curves of the two groups were(0.08±0.12)and(-0.23±0.12)in non-contrast scans(t=9.458,P <0.001).When the slope cut point was-0.105 as the threshold,the area under the curve of the ROC was 0.960,and the sensitivity was 90% and specificity was 85%.The single-energy CT value of adrenal lipid-poor adenoma at the energy level from 40 to 190 ke V in arterial phase and venous phase was lower than that of metastases.There were no significant difference in CT values between adrenal lipid-poor adenoma and metastases at the energy level of 40 ke V and 50 ke V in the arterial phase(P >0.05).The CT values in arterial and venous phase under other different single energy were statistically different(P <0.05).There was no statistical difference significantly of the slopes of the spectral curves between the two groups in arterial phase.The slopes of the spectral curves were(-1.03±0.48),(-1.23±0.49)(P =0.225>0.05).The slopes of the spectral curves in Arterial phase were(-0.85±0.28)and(-1.24±0.34),which showed significant difference(P =0.01<0.05).The area under the ROC curve was 0.819,with a sensitivity was 80% and specificity was 82.4%,when the cut-off point of the venous phase spectrum curve was-0.9850 3.Iodine concentration Of Enhanced scanning The iodine concentration(IC)and normalized iodine concentration(NIC)in the arterial and venous phases of adrenal lipid-poor adenomas were lower than those in metastases,and there was no significant difference of IC in arterial phase(P =0.104>0.05).The differences between the arterial phases NIC and venous phases IC and NIC of two groups of lesions were statistically significant(P <0.05).ROC curve showed that the sensitivity and specificity of venous phases iodine concentration and normalized iodine concentration were better than those of arterial phase.Conclusion: The third-generation dual-source CT energy spectrum curve and quantitative analysis of iodine concentration help to better distinguish adrenal lipid-poor adenomas and small metastases,which is difficult to identify by conventional CT scans and multi-phase enhanced scans.A new effective method are provided to clinical diagnosis.