低管电压低碘含量对比剂在胸部CT强化检查中的初步应用研究

Utility of low kVp technique and contrast agent with reduced iodine content in enhanced chest CT: a preliminary study

目的：评价胸部强化CT检查中低碘含量对比剂在管电压100 kVp时的辐射剂量、强化效果、图像质量以及对影像诊断的影响.方法：200例初次行胸部强化检查住院患者,体质量指数（Body mass index,BMI）＜28,随机分为4个观察组,每组50例.A组采用管电压120 kVp,碘对比剂使用碘海醇（欧乃派克300 mgI/mL）;B组采用管电压120 kVp,碘对比剂使用碘克沙醇（威视派克270 mgI/mL）;C组100 kVp,碘海醇（欧乃派克300mgI/mL）;D组100kVp,碘克沙醇（威视派克270 mgI/mL）.分别记录每例容积CT剂量指数（Volume CT dose index,CTDIvol）、剂量长度乘积（Dose length product,DLP）,并计算出有效放射剂量（Effective dose,ED）.主观图像质量分别由1名低年资和1名高年资影像医师进行评定.客观图像质量通过测量增强后肺动脉的CT值、噪声并通过计算对比噪声比（Contrast to noise ratio,CNR）来评价,并对4组中有明确组织病理学结果的病例进行符合率分析.结果：管电压100kVp时使用碘海醇（300 mgI/mL）的C组肺动脉CT值（204.9±32.4） HU要比120 kVp时的A组（172.1±24.4） HU高19.1％;在管电压100kVp时使用碘克沙醇（270 mgI/mL）的D组肺动脉CT值（188.7±26.0） HU要比120 kVp时的B组（154.9±21.4） HU高21.8％.100kVp条件辐射剂量C组（3.9±0.6）mSv和D组（3.9±0.8）mSv低于120 kVp条件的A组（4.8±1.3） mSv与B组（5.1±1.3）mSv（P＜0.01）.A组和B组图像评价要略好于C组与D组图像,4组图像质量均可满足诊断要求,2名医师对4组图像评分的一致性较好（kappa值=0.76±0.05）.与病理诊断随访结果显示,200例中有明确病理诊断的137例,占68.5％,4组病理诊断符合率均在82.1％～86.8％之间,无统计学差异（P=0.964）.结论：管电压在100 kVp时使用低碘含量对比剂碘克沙醇（270 mgI/mL）进行强化胸部CT检查,强化效果及影像质量能够满足临床诊断要求,且有效辐射剂量比常规检查能减少18.8％.

Objective：To evaluate the utility of low kVp technique and reduced iodine contrast agent in enhanced chest CT by comparison of radiation dose,enhancement,image quality and diagnostic accuracy.Methods：200 patients with BMI＜28 underwent enhanced chest CT examination,and were randomly divided into four groups （n=50 for each group）：group A with 120kVp and iohexol（Omnipaque,300mgI/mL）,group B with 120kVp and iodixanol（Visipaque,270mgI/mL）,group C with 100kVp and iohexol （Omnipaque,300 mgI/mL） and group D with 100 kVp and iodixanol （Visipaque,270 mgI/mL）.The volume CT dose index（CTDIvol）,the dose length product（DLP） were recorded and the effective rediation dose（ED） was calculated.Two radiologists evaluated subjective image quality with 4-points score.CT value and SD value for pulmonary artery were measured and the contrast to noise ratio （CNR） was calculated.The diagnostic accuracy was compared with pathological results for each group.Results：For 300 mgI/mL iohexol,the CT value of pulmonary artery in group A （（204.9±32.4）HU） was 19.1％ higher than that in group C （（172.1±24.4）HU）,for 270mgI/mL iodixanol,the CT value of pulmonary artery in group A （（188.7±26.0）HU） was 21.8％ higher than that in group C（（154.9±21.4）HU）.The effective radiation doses for 100 kVp（group C （3.9±0.6）mSv and group D （3.9±0.8）mSv） were lower than 120 kVp （group A （4.8±1.3）mSv and group B （5.1±1.3）mSv）（P＜0.01）.Subjective image qualities for four groups all achieved the standards for diagnostics,and the scores for group A and group B were a little better than group C and group D.The scores of two radiologists were highly consistent （kappa=0.76±0.05）.Compared with pathological results,the consistent rates for four groups ranged from 82.1％ to 86.8％ and had no significant difference.Conclusion：Combination of 100 kVp and 270 mgI/mL iodixanol in enhanced chest CT examination met the requirement of clinical diagnosis,and reduced 18.8％ radiation dose.