ABSTRACT
Objective To evaluate the value of material decomposition imaging of spectrum CT in overcoming renal cyst pseudoenhaneement.Methods Totally 80 patients with renal cysts (total 75 cysts) who underwent CT imaging with GSI mode were collected.The renal cysts were divided into 3 groups according to diameters,group A (diameters 0.5-＜1.5 cm,n=25),B (1.5-＜2.5 cm,n=25) and C (2.5-＜3.5 cm,n=25) respectively.The iodine-water density imaging was reconstructed by using the GSI Viewer analysis software.The CT value and iodine-water concentration of the cysts were recorded.The difference of CT value,iodine-water concentration in unenhanced and enhanced dual phases in each group was compared.Results The difference of CT value between plain scan and parenchyma phase among the 3 groups had statistically significant difference (F=204.128,P＜0.001),and the differences comparing any two were statistically significant (all P＜0.05).The postcontrast attenuation increased more than 10 HU in group A and B,indicating renal cyst pseudoenhancement,and less than 10 HU in group C,which had no pseudoenhancement.There were statistical difference in iodine concentration of the cysts of the 3 groups in unenhance,cortical and parenchyma phases (all P＜0.001),but the difference value in unenhance,cortical and parenchyma phases were less than 10 (100 μg/cm3),and the difference value of the 3 group was group A＞group B＞group C (all P＜0.05).The water concentration of the cysts in group A descend in renal cortical and parenchyma phase with statistical difference (P＜0.001),but the difference value was less than 10 mg/cms.Conclusion The measurements of iodine-water concentration appear to drift as well,the smaller the greater,The degree of the iodine concentration shifting is more obvious than water concentration.
ABSTRACT
OBJECTIVE: To evaluate the effect of thin overlapping reconstruction on the attenuation of small (< or = 3 cm) renal cysts in the nephrographic phase of multidetector CT (MDCT). MATERIALS AND METHODS: We scanned a phantom kidney containing spheres of various sizes (10, 20, and 30 mm) using both 4- and 16-channel MDCT scanners, and reconstructed images with various slice thickness (T, mm) and intervals (I, mm). The attenuation increase (AI) was measured for each sphere in 240-HU diluted solution of contrast material and compared with the attenuation in 35-HU solution. RESULTS: On the 4-channel MDCT, thin overlapping reconstruction (T/I = 3/1, compared with 5/5) lowered the AI as much as 17 HU in the 10 mm-sphere and 6 HU in the 20 mm-sphere (p < 0.05). Thin slicing alone was also effective; however overlapping alone was not. On the 16-channel MDCT, AI in the 10 mm-sphere was significantly lower than on the 4-channel MDCT with T/I = 5/5 (p < 0.05), however thinner slicing or overlapping did not affect the attenuation significantly in all of the spheres. CONCLUSION: The effect of thin overlapping reconstruction on minimizing falsely elevated attenuation in the nephrographic phase was significant only in cysts < or =20 mm on the 4-channel MDCT.