中文摘要：

目的：分析肿瘤血管内皮特异性靶向肽GX1在结肠癌与肺癌中的显像差异，探讨GX1在胃肠道肿瘤早期诊治的应用价值。方法：构建荷人结肠癌、肺癌移植瘤裸鼠模型，99 Tcm 直接法制备99 Tcm -GX1，经尾静脉分别注入荷人结肠癌、肺癌小鼠体内，SPECT显像连续追踪24h，观察99 Tcm -GX1在结肠癌与肺癌中显像差异，计算机勾划肿瘤及心脏感兴趣区，比较两组T/NT比值差异。结果：99 Tcm 直接法标记GX1，所得标记率在90%以上，无需纯化，比活度大于200Ci/mmol，满足显像要求。结肠癌组荷瘤小鼠自8h起右后肢背侧肿瘤部位即可见放射性浓聚，并高于心血池本底，T/NT比值＞1，18h显影最清晰，随时间延长T/NT比值总体呈递增趋势；肺癌组荷瘤小鼠8h右后肢背侧肿瘤部位无明显显影，自12h起肿瘤部位开始出现放射性浓聚，并高于心血池本底，18h显影最清晰，T/NT比值随时间延长亦呈递增趋势。比较两组T/NT比值，自8h至24h，结肠癌组比值持续高于肺癌组。结论：GX1可靶向到结肠癌与肺癌荷瘤小鼠的肿瘤组织，并具有肿瘤标志物的影像学特征，与肺癌相比，GX1在结肠癌成像中具有更高的灵敏度、更高的体内肿瘤组织滞留率和更高的T/NT比率。结合早期胃癌中研究结果，GX1在胃肠道肿瘤早期时相探测方面较肺癌具有更多优势。

英文摘要：

Objective：To analyze the imaging variation of tumor vasculature homing PePtide GX1 in colon cancer and lung cancer. Methods：99 Tcm -GX1 was PrePared by labeling GX1 PePtide acquired by chemosynthesis with 99 Tcm O4 -using direct labeling method. ECT imaging of nude mice bearing tumor xenografts of human colon cancer and lung cancer injected with 99 Tcm -GX1 was Performed to analyze the imaging variation. T/NT ratios were calculat-ed by comParing the radioactivity in tumor and heart. Results：99 Tcm -GX1 was acquired with high label radiolabeling efficiency exceeding 90%,high sPecific activity beyond 200Ci/mmol,which confirmed the qualification of 99 Tcm -GX1 for ECT imaging. The tumor on the right flank can be visualized from 8h in colon cancer grouP with a increasing trend including higher radioactivity than heart and T/NT ratio greater than 1 on the whole. In lung cancer grouP,there was obvious radioactivity visualized in the tumor on the right flank from 12h comPared with the imaging at 8h and the increasing trend including higher radioactivity than heart and T/NT ratio greater than 1 was showed on the whole. The most clearly visualized imaging aPPeared at 18h in both grouPs. Continuous higher T/NT ratios between tumor and heart were observed in colon cancer grouP comPared to that of lung cancer grouP from 8h to 24h. Conclusion：GX1 owned the imaging feature of tumor marker by sPecific targeting to colon cancer and lung cancer tissue in tumor-bearing nude mice. ComPared with that of lung cancer,ECT imaging in colon cancer with GX1 PePtide showed higher sensitivity,tumor retention,and T/NT ratios. Combing the former results in gastric cancer,the suPeriority of GX1 PeP-tide for early detection in gastroenteric tumor was fully confirmed.