80kVp条件下低剂量对比剂分次团注双期CTU的应用研究

Abstract

目的 研究80 kVp联合迭代重建技术的条件下,使用低剂量碘对比剂行分次团注双期CT尿路成像(CTU)检查的可行性.方法 60例血尿待查患者分为2组(80 kVp组、120 kVp组各30例),行全泌尿系平扫及分2次团注对比剂后行肾实质-分泌期CTU扫描.2次团注对比剂的方案为:80 kVp组35 mL和60 mL;120 kVp组50 mL和70 mL.2组CTU重建方法为:80 kVp组自适应统计迭代重建(30％ASiR);120 kVp组滤波反投影(FBP).2名读片者对CTU重建图像进行独立盲法读片,对图像质量进行主观评分,测量图像噪声、集合系统各段CT值,计算对比噪声比(CNR).记录、计算所有病例CTU有效剂量(ED)及体型特异性剂量评估值(SSDE).对2组图像质量主观评分、噪声、CT值、CNR、ED及SSDE使用非参数秩和检验进行比较,以P<0.05为差异有统计学意义.结果 80 kVp组与120 kVp组图像质量主观评分差异无统计学意义(Z=-1.791,P=0.073).80 kVp组图像噪声高于120 kVp组,差异有统计学意义(Z=-6.299,P<0.001).80 kVp组S6段(膀胱)CT值高于120 kVp组(Z=-2.466,P=0.014),余2组CTU各尿路分段CT值差异均无统计学意义(Z=-1.204～-0.163,P=0.228～0.871);2组CTU各尿路分段CNR差异均无统计学意义(Z=-1.818～-0.202,P=0.069～0.840).80 kVp组ED和SSDE低于120 kVp组,差异有统计学意义(Z=-6.655～-6.653,P<0.001).结论 80 kVp联合迭代重建技术的条件下,使用低剂量碘对比剂行分次团注双期CTU检查是可行的,可明显降低辐射剂量,且图像质量满足临床诊断要求.

Objective To evaluate the feasibility of 80 kVp tube voltage combined with adaptive statistical iterative reconstruction (ASiR)in low dose contrast media split-bolus 2-phase CTU.Methods Sixty patients with hematuria were recruited in this study.All the patients (80 kVp Group,n=30;120 kVp Group,n=30)underwent split-bolus 2-phase CTU (80 kVp Group:35 mL and 60 mL;120 kVp Group:50 mL and 70 mL).CTU images were reconstructed with 30％ ASiR in 80 kVp Group and with filtered back projection (FBP)in 120 kVp Group.Subjective and objective analysis of CTU images were accomplished by two qualified and independent readers.The radiation dose was evaluated by ED and SSDE.The image score,noise,attenuation value and CNR of urinary tract,and radiation dose were compared by Mann-Whitney rank sum test.Results There was no significant difference in the image quality between two groups (Z =-1.791,P =0.073).The noise of 80 kVp Group were higher than that of 120 kVp Group (Z =-6.299,P <0.001 ), while there was no significant difference of attenuation value between the two groups (Z =-1.204 --0.163,P =0.228 -0.871,except bladder),as well as the CNRs (Z =- 1.818 --0.202,P =0.069 -0.840).The ED and SSDE of 80kVp Group were significantly lower than those of 120 kVp Group (Z =-6.655--6.653,P <0.001).Conclusion The protocol of 80 kVp tube voltage combined with iterative reconstruction in low dose contrast media split-bolus 2-phase CTU is feasible for clinical application,with reduction of radiation dose and acceptable diagnostic image quality.