胰腺癌是我国常见的消化道恶性肿瘤，临床治疗效果差。如何早期准确诊断是提高其临床疗效的关键。本课题拟制备出GRPR受体介导的、具有长循环特性、铃蟾肽－125I标记的 PEG-CS-SPIO磁性纳米粒子，测定其理化特性，并在7，12．二甲基苯并蒽(7，12－dimethyl－l，2-benzanthracene，DMBA)可以诱导形成大鼠的胰腺导管腺癌模型及裸鼠皮下荷人胰腺癌模型上进行研究，探讨靶向增强显示微小胰腺癌灶的可能。一旦成功，将对早期胰腺癌及胰腺癌与慢性胰腺炎的鉴别提供新的途径，具有十分重要的意义。对其它肿瘤如前列腺癌与前列腺增生的鉴别也有一定的借鉴作用。

Pancreatic cancer is the third most common cause of.gastrointestinal malignancies.Despite significant improvements in surgical.and non-surgical treatment modalities , the 5-year survival rate remains poor. Early detection of panreatic cancer is crucial for the improvement of clinical treatment outcomes .It is difficult to detect the micro pancreatic tumor correctly and to distinguised benign and malignent pancreatic lesions using conventional clinical imaging methods. Novel approaches for early detection will make the most significant impact on clinical management of this disease. .Previously, we have developed a colloidal dextran-stabilized iron oxide nanocompound (SPIO) as a magnetic label . In an effort to use this magnetic label to visualize pancreatic tumor by MRI in vivo, we synthesis a new nanoparticles ,mediated by gastrin releasing peptide (GRP)receptor which is high expression biomarker on pancreastic cancer cells. In current study，we try to conjugate bombesin －125 I to PEG－Chitosan－SPIO and analysis its chemical and physical characteristics. In vitro and vivo competitive binding experiments to assess the magnetically labeled retained affinity to the GRP receptors. Two animals models ,including a rat model of pancreatic intraepithelial carcinoma induced by DMBA and red fluorescent protein orthotopic transpalntation nude mice metastasis model of pancreatic cancer, were established ，respectively.we evaluated the target-specific agents potential use in early MR imaging of micro panreatic tumors.If successful，this new approach may be valuable for other tumors targeting enhancemenc.