双能CT与MDCT多期增强扫描对肾囊肿CT值的影响

Effect of dual-energy CT and MSCT contrast-enhanced scanning on the CT value of renal cyst

目的:对比研究双能CT和多排螺旋CT多期增强扫描肾囊肿CT值的变化,观察肾囊肿假性强化现象。方法:43例肾囊肿患者(46个肾囊肿)纳入本次研究,均采用CT多期增强扫描,所有病灶均被诊断为单纯肾囊肿(BosniakⅠ型)。患者行常规平扫后,经肘静脉团注非离子型对比剂,分别采集25s皮质期、70s皮髓质期及120s均衡期图像。23位患者的26个囊肿采用GE MDCT腹部多期扫描,20位患者的20个囊肿采用Siemens双能CT腹部多期扫描。结果:46个肾囊肿中直径最小5mm,最大57mm。双能CT检出20例肾囊肿,6例出现假性强化,MDCT检出26例肾囊肿,13例出现假性强化,双能CT和MDCT的假性强化发生率差异无统计学意义(P=0.177)。双能CT扫描增强前后囊肿的CT值最大相差(8.74±7.09)HU;MDCT扫描增强前后囊肿的CT值最大相差(11.64±7.37)HU。直径<1cm的囊肿在重建层厚5mm时假性强化的概率明显高于重建层厚1mm时假性强化的概率。结论:肾囊肿假性强化的现象是客观存在的,部分容积效应和硬射线效应是其中的两个重要因素。另外,MDCT机型、病变大小、肾脏背景浓度及肾囊肿位置都是影响囊肿CT值测量的因素。

Objective：To compare the changes of CT value of renal cyst using dual-energy CT and MSCT with multi-phase contrast-enhanced scanning and to observe the phenomenon of preudo-enhancement of renal cyst.Methods：43 cases（46 cysts） with renal cyst were recruited in this study,all of the patients underwent multi-phase MSCT and were diagnosed as simple renal cysts（BosniakⅠtype）.After routine plain CT scanning,bolus of non-ionic contrast agent was injected via elbow vein.The delayed time were 25s（cortical phase）,70s（cortico-medullary phase） and 120s（equilibrium phase）.23 cases（26 cysts） were scanned with GE MSCT and 20 cases（20 cysts） were scanned with Siemens dual-energy CT dual-energy mode.Results：Of the 46 renal cysts measured,the smallest one was 5mm and the largest one was 57mm in diameter.Six（30%） of the 20 cysts detected by dual-energy CT showed pseudo-ehancement and 13（50%） of the 26 cysts showed pseudo-enhancement on MSCT.No significant statistical difference was existed between the incidence of dual-energy CT and MSCT in detecting pseudo-enhancement（P=0.177）.The mean maximum CT value difference of cyst before and after contrast enhancement was（8.74±7.09）HU on dual-energy CT and was（11.64±7.37）HU on MSCT.The incidence rate of pseudo-enhancement with the cyst 1cm in diameter and reconstructed on 5mm slice thickness was markedly higher than that reconstructed on 1mm slice thickness.Conclusion：The pseudo-enhancement phenomenon of renal cyst was objectively existed,the main causing factors were partial volume effect and hard-ray effect.The type of MSCT equipment,size of cyst,renal background attenuation of kidney and the relative position of cyst were the factors affecting the measurement of CT value.