Effect of Tube Current on the Pseudo-enhancement of Renal Cyst / 中国医学影像学杂志

ABSTRACT

PurposeTo evaluate the effect of tube current on the pseudo-enhancement of renal cyst by simulating the phantom model of simple renal cyst.Materials and Methods 10% glucose and iodine solution with a certain concentration was used to simulate the renal parenchymal background concentration in plain scan, moderate enhancement and maximum enhancement respectively. The diameters of the cysts were 6 mm, 10 mm and 15 mm, respectively, and the cysts were divided into three groups according to different tube current 119 mAs (group A), 178 mAs (group B) and 297 mAs (group C) while the tube voltage were all 120 kV. Whether pseudo-enhancement exists in cyst under different conditions was determined using an increase of CT value of 10 HU as the critical value. Results In group A, there was pseudo enhancement at the 240 HU background, and it was most significant with the diameter of 6 mm, which was 21 HU. In group B, pseudo-enhancement occurred in cysts with diameter of both 10 mm and 6 mm under the background of 180 HU and 240 HU, moreover, the biggest difference was 20.4 HU and it occurred in cyst with diameter of 6 mm under the background of 240 HU. In group C, pseudo-enhancement only occurred in cyst with diameter of 6 mm under the condition of 125 HU and 240 HU background concentration. Background concentration (F=17.587, P<0.01) and cyst diameter (F=4.214,P<0.05) had greater impact on cyst pseudo-enhancement, the higher the background concentration and smaller the diameter, more significantly the pseudo-enhancement would occur. With the increase of the tube current, the CT volume dose index increased, and the pseudo enhancement value was smaller, but there was no obvious regularity of pseudo-enhancement occurrence rate in cysts with different background concentration and diameter in each group.Conclusion The increase of tube current cannot completely eliminate cyst pseudo-enhancement. High background concentration and small diameter cyst are important factors in pseudo-enhancement. However, increasing the tube current can reduce the probability of occurrence of pseudo-enhancement to some extent. For those with heavier body weight, it might be necessary to increase the tube current to improve image quality and reduce the occurrence of renal cyst pseudo-enhancement.