摘要
目的：探讨低浓度对比剂双能量CT最佳单能量成像对提高肝静脉成像质量的应用价值。方法：前瞻性研究151例行双能量CT全腹增强扫描的且体质量指数（BMI）＞25 kg/m2的患者，按照首诊时间将患者随机分为低浓度对比剂能谱扫描单能量成像组（A组，管电压140 kVp和80 kVp瞬时切换，对比剂浓度为270 mgI/mL）和高浓度对比剂常规扫描组（B组，管电压120 kVp，对比剂浓度为350 mgI/mL），将A组静脉期薄层图像应用最佳对比噪声比（Optimal CNR）技术获得最佳单能量图像。对A组最佳单能量图像和B组图像分别进行肝静脉重建（MIP，VR），分别测量两组图像肝左、中、右静脉和肝实质的CT值、肝实质的背景噪声（SD值），计算肝左、中、右静脉的CNR，对两组图像的肝静脉CNR进行独立样本t检验；由2名观察者盲法对两组图像肝静脉显示情况进行主观质量评分，采用Kappa检验评价两观察者评估一致性，并以Mann-Whitney U检验比较两组肝静脉评分差异。记录两组病例的CTDIvol，以独立样本t检验进行比较；计算并比较两组对比剂总碘量。结果：A组肝静脉最佳单能图像能量水平集中在49～51 keV。两组肝左静脉、肝中静脉、肝右静脉、肝实质的CT值分别为（335.29±68.45） HU、（343.16±73.95） HU、（327.80±76.22） HU、（187.74±31.98） HU，（194.82±33.60） HU、（196.62±36.11） HU、（190.60±33.61） HU、（115.89±16.94） HU；肝左、中、右静脉与肝实质的CT值差值、肝实质的背景噪声值分别为（147.39±48.91） HU、（155.26±56.68） HU、（139.90±55.19） HU、（39.12±10.04） HU，（78.93±27.92） HU、（80.73±28.44） HU、（74.71±26.03） HU、（33.82±8.94） HU；两组图像的肝左、中、右静脉CNR值分别为3.93±1.80、4.35±2.29、3.91±2.08，2.40±0.85、2.44±0.82、2.26±0.75，以上数据A组均明显高于B组，且差异均具有统计学意义（P值均<0.05）。2名观察者对两组图像肝静脉评分的一致性良好（Kappa值均＞0.80），两组肝静脉评分为（3.43±0.58）分和（3.48±0.68）分，差异无统计学意义（P＝0.683）。A、B两组CTDIvol分别为（16.87±0.00） mGy和（15.74±5.26） mGy，二者无统计学差异（P＞0.05）；A组和B组的总碘量分别为27 000 mg和35 000 mg，A组较B组降低22.86%。结论：对BMI＞25 kg/m2者，通过双能量CT最佳CNR技术，应用低浓度浓度对比剂在降低总碘含量的同时，可以获得更高质量的肝静脉图像，且不增加辐射剂量。
Abstract
Objective: To investigate the effect of spectral CT monochromatic images with low concentration contrast media for improving imaging quality of the hepatic veins. Methods: One hundred and fifty-one patients from March 2013 to January 2014 in our hospital underwent spectral CT examination of the full abdomen. According to the first scan time, patients(BMI＞25 kg/m2) were randomly divided into group A with spectral CT optimal monochromatic imaging and low concentration contrast media(270 mgI/mL) and group B with conventional imaging and high concentration contrast media(350 mgI/mL). During portal phase, conventional images and optimal monochromatic images with slice thickness of 1.25 mm were obtained, and volume rendering(VR) and maximum intensity projection(MIP) were created to show the hepatic venography. Independent t-test was used to compare the hepatic venography. And the liver parenchyma, image noise, vein-to-liver contrast-to-noise ratio(CNR) between the two image data sets were compared. The overall imaging quality was evaluated on a five-point scale by two radiologists. Inter-observer agreement in subjective image quality grading was assessed by Kapppa statistics. Mann-Whitney U test was used to compare the image quality score of the hepatic venography between the two groups. The CTDIvol of the two groups were recorded, and the difference between group A and group B was compared by independent t-test. The total amount of iodine was calculated and compared. Result: The monochromatic images at 49～51 keV were found to demonstrate the optimal CNR for the hepatic venography. In group A, CT values of the left hepatic vein, the middle hepatic vein, the right hepatic vein, liver parenchyma, the difference between hepatic veins and liver parenchyma, and the image noise were (335.29±68.45) HU, (343.16±73.95) HU, (327.80±76.22) HU, (187.74±31.98) HU, (147.39±48.91) HU, (155.26±56.68) HU, (139.90±55.19) HU and (39.12±10.04) HU, respectively. Those in group B were (194.82±33.60) HU, (196.62±36.11) HU, (190.60±33.61) HU, (115.89±16.94) HU, (78.93±27.92) HU, (80.73±28.44) HU, (74.71±26.03) HU and (33.82±8.94) HU, respectively. The vein-to-liver CNRs for group A and group B were 3.93±1.80, 4.35±2.29, 3.91±2.08, 2.40±0.85, 2.44±0.82 and 2.26±0.75, respectively. The data of group A were all significantly higher than group B(P＜0.05). Kappa statistics demonstrated a good inter-observer agreement(Kappa values＞0.8). The image quality scores of the hepatic venography of the two groups were 3.43±0.58 and 3.48±0.68. There was no significant difference between the two groups. The CTDIvol of the two groups were (16.87±0.00) mGy and (15.74±5.26) mGy, respectively, and there was no significant difference between the two groups. The total amount of iodine of the two groups were 27 000 mg and 35 000 mg. Group A was 22.86% lower than group B. Conclusion: For patients with BMI＞25 kg/m2, in the premise of reducing the concentration of contrast agent, spectral CT monochromatic imaging can improve the imaging quality of the hepatic veins without significant increase of radiation exposure.
关键词
肝静脉 /
体层摄影术 /
螺旋计算机
Key words
Hepatic veins /
Tomography /
spiral computed
佟梓滨;刘爱连;刘义军;田士峰;张龙敏;刘静红;浦仁旺.
低浓度对比剂单能量成像对提高肝静脉成像质量的研究[J]. 中国临床医学影像杂志. 2015, 26(2): 95-98
TONG Zi-bin;LIU Ai-lian;LIU Yi-jun;TIAN Shi-feng;ZHANG Long-min;LIU Jing-hong;PU Ren-wang.
Selecting optimal monochromatic level of spectral CT imaging with low concentration contrast media for improving imaging quality of hepatic veins[J]. Journal of China Clinic Medical Imaging. 2015, 26(2): 95-98
中图分类号：
Ｒ333.4
Ｒ331.34
Ｒ814.42
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