低管电压结合低对比剂浓度对胃肠道恶性肿瘤供血动脉CT图像质量的影响

Preliminary study of improved quality of computed tomographic angiography on tumor blood supply arteries of gastrointestinal tract malignant tumors with low tube voltage and low concentration contrast medium

目的 探讨应用低管电压结合低对比剂浓度,使用50％自适应统计迭代重建（ASiR）对胃肠道恶性肿瘤供血血管图像质量的影响.方法 对大连医科大学附属第一医院2013年3-12月行全腹能谱CT扫描、体质指数（BMI）≤22 kg/m^2并经病理证实的胃肠道恶性肿瘤58例患者进行分析.按首诊日期分为A组（管电压为80 kVp联合50％ ASiR,对比剂浓度为270 mgI/ml）和B组（管电压为120 kVp,对比剂浓度为350 mgI/ml）.使用Mann-WhitneyU秩和检验比较两组年龄差异.使用Fisher确切概率比较两组男女比例差异.由两位放射科医生对肿瘤供血动脉重建图像进行主观评分,采用kappa检验比较评分一致性;使用Mann-Whitney U秩和检验进行两组重建图像主观评分比较.测量肿瘤供血动脉CT值（记为CT1）、病灶水平右侧竖脊肌CT值及前腹壁脂肪的SD值（SD值）.使用组内相关系数（ICC）比较上述数据的一致性.采用独立样本t检验比较两组CT1、SD值、对比噪声比（CNR）、图像灵敏度（FOM）及CT容积剂量指数（CTDIvol）.结果 两组年龄及性别间差异均无统计学意义（均P＞ 0.05）.肿瘤供血动脉重建图像主观评分一致性较好（kappa值分别为0.880、0.813）.A组与B组重建图像主观评分间差异无统计学意义（2.9±0.9比2.5±0.8,P=0.09）.CT1、SD值、CNR及FOM值间一致性很好（ICC值均＞0.75）.A组CT1[（459±69） HU]、CNR值（20.2±3.3）、FOM（85±37）明显高于B组CT1值[（250 ±42） HU]、CNR值（9.3±1.9）、FOM（9±4）（P=0.00）.A组SD值明显低于B组[（20.0±1.7）比（22.4±3.2）,P＜0.01].CTDIvol值A组明显低于B组[（5.2±1.2）比（13.5±4.7） mGy,P＜0.01].结论 对于BMI≤22 kg/m2的患者,低管电压及低对比剂浓度条件下,使用50％ ASiR算法,获得的胃肠道恶性肿瘤供血血管成像图像质量优于常规扫描高对比剂浓度的图像,且明显降低患者的辐射剂量.

Objective To assess the image quality of gastrointestinal tract malignant tumors arteries using low tube voltage,low contrast medium concentration and 50% adaptive statistical iterative reconstruction （ASiR） algorithm.Methods A total of 58 patients with pathologically confirmed gastrointestinal tract malignant tumors and body mass index （BMI） under 22 kg/m^2 undergoing computed tomography （CT） scanning during March-December 2013.They were randomly divided into group A （270 mgI/ml of contrast medium,80 kVp tube voltage scanning and 50% ASiR; 21 males and 11 females with an age range of 40-90 years） and group B （350 mgI/ml of contrast medium,120 kVp routine tube voltage; 22 males and 4 females with an age range of 40-76 years）.The inter-group differences of age and gender ratio were compared with Mann-Whitney U and Fisher exact tests respectively.Two independent radiologists reviewed reconstructions and separated the reconstructed image into 5 points according to image quality.The CT value of tumor blood supplying artery （CT1 value） and fat in anterior abdominal wall SD value） were measured and image noise,contrast-to-noise ratio （CNR） and figure of merit （FOM） calculated.The interobserver variation was estimated by weighted kappa statistics and intra-class correlation coefficients （ICC） test.The point of image quality of two groups was compared by Mann-Whitney U test.The paired Student t test was used to compare the inter-group differences in CT1,SD,CNR,FOM and CT dose index （CTDIvol）.Results No inter-group difference existed in patient age or gender ratio.The consistency of two radiologists was excellent （kappa value 〉 0.80 ; ICC value 〉 0.75）.The subjective image quality scores of tumor blood supplying arteries showed no inter-group difference （P =0.09）.The tumor blood supply arteries CT value,CNR and FOM of group A （459 ±69 HU,20.2 ±3.3 and 85 ±37） were significantly higher than those of group B （250±42 HU,9.3 ±1.9 and 9 ±4） （both P〈0.01）.The SD value of group A （20.0 ± 1.7） was obviously lower than that of group B （22.4 ± 3.2） （P 〈 0.01）.And the CTDIvol of group A （5.2 ± 1.2 mGy） was obviously lower than that of group B （13.5 ±4.7 mGy） （P 〈 0.01）.Conclusion For patients of BMI ≤ 22 kg/m^2,low tube voltage and low contrast medium concentration scan condition with 50% ASiR algorithm is feasible for acquiring better quality image and ensuring significant reduction in effective dose.