不同出血速率联合低剂量多层螺旋CT诊断消化道出血的实验研究

Study on different Iodine flow rate combined with low dose MDCT scanning technique in diagnosis of gastrointestinal hemorrhage

目的比较3种不同出血速率在不同管电压条件下,多层螺旋CT(MDCT)显示消化道活动性出血的敏感性。方法复制消化道出血模型,以测得的30例消化道出血患者(均经病理证实)出血点CT平均值(212.13±64.54)HU为参考值,将浓度为320 mg I/ml碘佛醇与0.9%生理盐水配比成浓度为6.4 mg I/ml的碘溶液,120 k V对应CT值(214.73±1.63)HU,在相同对比剂浓度下(6.4 mg I/ml),通过微量注射泵模拟出血速率,分别以0.3、0.4和0.5 ml/min的注射速率注射,并对消化道出血模型行MDCT扫描。对照组:120 kV,300 mAs;实验A组:100 k V,300 m As;实验B组:100 k V,400 m As;实验C组:80 k V,465 m As。由2位放射医师采用双盲法读片,比较4组辐射剂量、客观噪声值、信噪比,记录每组MDCT对模型出血的检出情况,并测量出血点CT值。结果对照组、实验A、B、C组CT容积剂量指数(CTDIvol)、有效剂量(ED)比较,差异有统计学意义(P <0.05);实验B组图像噪声、信噪比、图像质量主观评分与对照组比较,差异无统计学意义(P>0.05);对照组和实验各组在出血速率为0.5和0.4 ml/min时对模型出血的检出率为100%;对照组、实验A、B组未能检出出血速率为0.3 mgI/min的出血;实验C组在出血率为0.3 ml/min时对模型出血检出率为28.6%(2/7),但检出率与对照组(-0.5 ml/min)比较差异有统计学意义(P<0.05)。结论常规扫描条件下,MDCT能够显示出血速率>0.4 ml/min的出血点;降低管电压能够有效增加出血点CT值。

Objective To compare the sensitivity of MDCT combined with different tube voltages in diagnosis of gastrointestinal bleeding.Methods The average CT value of the 30 patients with alimentary tract bleeding (all confirmed by pathology) was (212.13±64.54) HU,which served as the reference value.A concentration of 6.4 mgI/ ml was prepared with Iodine fo alcohol (320 mgI/ml) and 0.9% normal saline;120 kV corresponds to CT value of (214.73±1.63) HU.Under the same contrast concentration (6.4 mgI/ml),the injection rate of 0.3 ml/min,0.4 ml/min,and 0.5 ml/min was performed with microinjection pump.MDCT scan was carried out on the gastrointestinal bleeding model.Control group:120 kV,300 mAs;Experimental group A:100 kV,300 mAs;Experimental group B:100 kV,400 mAs;Experimental group C:80 kV,465 mAs Radiation dose,objective noise value and SNR,recognition rate of hemorrhage,CT value of the bleeding point were recorded by two double-blind radiologists.Results CT volume dose index (CTDIvol) and effective dose (ED) were significant different among 4 groups (P<0.05).There was no statistically significant difference between the group B and control group in image noise,SNR,image quality subjective score (P>0.05).Detection rate of the model hemorrhage was 100% in all 4 groups when the bleeding rate was 0.5 and 0.4 ml/min.Control group,group A and group B failed to detect bleeding when bleeding rate was 0.3 ml/min.The detection rate of hemorrhage of 0.3 ml/min was (2/7) in group C,which was increased significantly when compared with control group (P<0.05).Conclusions Under normal scanning conditions,MDCT is able to identify bleeding point (0.4 ml/min);reduction of the tube voltage effectively increases the CT value of the bleeding point.