管电流对肾囊肿假性强化的影响

Effect of Tube Current on the Pseudo-enhancement of Renal Cyst

目的通过模拟单纯性肾囊肿的体模模型,评估管电流对肾囊肿假性强化的影响。材料与方法使用10%葡萄糖液及一定浓度的含碘溶液,分别模拟平扫、中等强化及最大强化程度肾实质背景浓度。囊肿直径分别为6 mm、10 mm、15 mm,依据管电流不同分为A组119 m As、B组178 m As、C组297 m As,管电压均为120 k V。以CT增加值10 HU为临界值,评估不同条件下囊肿有无假性强化。结果 A组仅在240 HU背景浓度下出现假性强化,且直径6 mm的囊肿最显著,为21 HU。B组直径10 mm和6 mm的囊肿在180 HU和240 HU背景下均出现假性强化,差值最大为240 HU直径6 mm的囊肿,为20.4 HU。C组仅直径6 mm的囊肿在125 HU和240 HU背景浓度下有假性强化。囊肿假性强化受背景浓度(F=17.587,P<0.01)和囊肿直径(F=4.214,P<0.05)较大,背景浓度越高,直径越小,假性强化越明显。随着管电流增加,CT容积剂量指数增加,假性强化值越来越小,但各组中不同背景浓度及不同直径的囊肿假性强化出现几率无明显规律。结论增加CT扫描管电流不能完全消除囊肿假性强化的产生。较高的背景浓度和较小的囊肿直径是产生假性强化的重要因素。但增加管电流可以在一定程度上减少假性强化发生的几率。对于体重较重者,适当增加管电流以改善图像质量、减少肾囊肿假性强化发生的可能是必要的。

Purpose To 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,pseudoenhancement 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 pseudoenhancement,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 pseudoenhancement 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.