Clinical Assessment Of Spectrum CT With Material Decomposition Technique And Virtual Monochromatic Imaging In Overcoming Renal Cyst Pseudoenhancement

Object:To evaluate the effect of material decomposition technique and virtual monochromatic imaging(VMS)of spectrum CT in overcoming renal cyst pseudoenhancement.Materials and Methods:Totally 75 patients with renal cysts were collected in our hospital underwent CT imaging with GSI mode from September 2014 to March2015.There were 41 male cases and 34 female cases;age 18~70 years old,average age 46.4±14.4 years old;BMI: 18.5~25.2Kg/m2,average BMI 23.91±1.83 kg/m2;abdominal girth: 70~90cm,average abdominal girth:84.73±3.14 cm.The iodine-water density imaging was reconstructed by using the GSI Viewer analysis software on an advantage workstation 4.5(GE Healthcare USA).The CT number and iodine-water density value of the cyst were recorded.The spectrum curve(X axis asthe single energy value,Y axis for CT number)of the unenhanced phase and parenchyma phase were reconstructed by using gemstone imaging Viewer,the corresponding ke V value of the closest point of the two curves was recorded,namely the optimal monochromatic energy level,defined as the energy setting needed to achieve the minimum postcontrast attenuation increase.Paired t test was applied in comparing iodine-water density value between unenhanced and enhanced phase on each group.One-way ANOVA test was used to analyze CT value difference and iodine-water density value difference between unenhanced and enhanced phase on each group.One-way ANOVA test was used to analyze the BMI and abdominal girth of patients,optimal monochromatic energy values in each group.P<0.05 was considered statistically significant.Results:Five patients did not conform to the requirements had be ruled out.Renal cysts of two patients became bigger and higher density in the follow-up,3 midway to terminate the follow-up for personal reasons.The renal cysts were divided into 3 groups according to diameter,the renal cysts diameter of group A,B and C were 0.5 ~ <1.5 cm(n=30),1.5 ~<2.5 cm(n=30),and 2.5 ~ <3.5 cm(n=30)respectively.There was no significant difference in BMI index and abdominal girth among the 3groups(P > 0.05).The overall difference of CT number difference between the unenhanced phase and parenchyma phase among the 3groups was statistically significant(P<0.001),comparing any two had the statistical significance(P < 0.05).The postcontrast attenuation increase surpassed 10 HU in group A and B,appearing renal cyst pseudoenhancement,and less than 10 HU in group C,did not appearing renal cyst pseudoenhancement.There were statistical difference in iodine density value of the cysts of the 3 groups between unenhanced and parenchyma phase(P <0.001),but the difference value in unenhanced and parenchyma phase were less than 10(100 ? g/cm 3),the overall difference between the 3 groups was statistically significant(P<0.001).There were statistical difference in water density value of the cysts of the group A and B between unenhanced and parenchyma phase(P<0.001),but the difference value in unenhanced and parenchyma phase were less than 10(mg/cm 3).The average optimal monochromatic energy level:group A: 90 ke V,group B: 85 ke V,group C: 80 ke V.The difference of the average optimal monochromatic energy value among the 3 groups was statistically significant(P<0.05).Conclusion:The measurements of iodine-water concentration appear to drift as well,the smaller of renal cyst was,the greater it measurement drifted,the degree of the iodine concentration shifting was more obvious than water concentration.Virtual monochromatic images at an optimal energy level couldovercome renal cyst pseudoenhancement.The choice of the optimal monochromatic energy value was related to the size of renal cyst.The smaller the renal cysts,the higher the optimal monochromatic energy value required to overcome the pseudoenhancement of renal cysts.