新型造影剂在小鼠肝脏肿瘤Micro-CT活体成像中的应用

Non-invasive visualization of tumors in the mouse liver using a novel nanoparticle contrast enhanced micro-CT imaging procedure

目的利用新型纳米颗粒造影剂结合Micro-CT成像技术,建立小鼠肝脏成像方法,并用于肝脏肿瘤的活体成像。方法 6只6-8周龄雄性C57BL/6J小鼠随机分成A组和B组,分别尾静脉注射纳米颗粒造影剂Exi Tron nano 12000 50μL和100μL;在注射前、注射后3 min、24 h、7 d、14 d、28 d和56 d对所有小鼠肝脏进行Micro-CT活体扫描;分别在小鼠肝左叶和肝右叶内选取感兴趣区（ROI）进行灰度值分析,比较不同时间点肝组织对比度的变化。确定合适的造影剂剂量,尾静脉注射至3只雄性16月龄HBV转基因肝癌模型小鼠（C组）,同上进行Micro-CT活体扫描,并于第56天全部安乐死后取肝脏观察病理学改变。结果 A组和B组小鼠在注射不同浓度造影剂后,冠状位重建图像及肝脏感兴趣区的平均灰度值结果显示：肝脏实质造影后均比注射前明显增强,24 h达到峰值,注射后56 d内,小鼠肝脏感兴趣区的平均灰度值与注射前相比仍维持在较高的水平,B组显著高于A组（P〈0.01）,确定后续实验采用B组造影剂剂量（100μL）。C组注射100μL造影剂后,各时间点均能比较清楚地看到肝脏癌性结节存在,病理学观察发现肝脏出现非典型增生,肿瘤细胞核大,染色质加深和肝细胞坏死。结论利用纳米颗粒造影剂结合Micro-CT成像技术,成功建立了小鼠肝脏活体成像方法,并可应用于肝脏肿瘤的活体成像研究。

Objective To establish an in vivo imaging method of normal or tumorous liver in mice by using a new type nanoparticle contrast agent, ExiTron nano 12000, coupled with micro-CT imaging.Methods Six 6-8-week old male C57BL/6J mice were randomly divided into group A and group group B, by intravenous injection of 50μL and 100μL ExiTron nano 12000, respectively.In vivo Micro-CT scans were performed before contrast agent injection, 3 minutes, 24 hours, 7, 14, 28 and 56 days after injection.To determine which dose is suitable for long-term studies, gray scale value a-nalysis was performed on selected region of interest （ ROI） in the left lobe and right anterior lobe of the liver, and the changes of liver tissue contrast was monitored after ExiTron nano 12000 injection.Three male HBV transgenic mice bearing liver tumors （ group C） were intravenously injected with the determined dose of ExiTron nano 12000 and were monitored by mi-cro-CT scans as above described.At 56 days after ExiTron nano 12000 injection, the mice were sacrificed and liver samples were taken for histological analysis.Results Cross-sectional images taken at various time points and the average gray scale value （ AGSV） analysis in the mouse liver revealed that the AGSV peaked at 24 hours after injection of contrast rea-gent and good contrast still presented in the livers within 56 days of observation for both groups, though group B showed a significantly higher contrast than group A （P〈0.01）.Those data indicated that the dose of group B （100μL） was better to maintain ExiTron nano 12000 in the liver of mice for a long time.Contrast-enhanced by 100μL of ExiTron nano 12000, the liver tumor nodules in the mice of group C could be clearly delineated by Micro CT imaging during a 56 days observa-tion.Histological analysis revealed atypical hyperplasia, enlarged nuclei with hyperchromasia and cell necrosis in the tumors.Conclusions An in vivo imaging method was established to non-invasively visualize mouse liver using micro-CT combined with nanoparticle-based contrast agent and this technology may be applied to a live imaging of murine primary liver tumors.