以抗体为探针的分子影像学检查是结直肠癌无创动态检测的新方法。免疫检测点PD-1/PD-L1是结直肠癌肿瘤耐受的重要机制。在肿瘤组织中精准监测PD-L1有助于免疫治疗选择、疗效及预后评估。课题组前期已成功制备光学显像剂NIR-PD-L1-mAb，检测到不同结直肠癌细胞及动物模型中PD-L1的表达变化。在此基础上，将采用放射性核素89Zr及131I分别制备PD-L1抗体PET与切伦科夫光学分子探针，检测结直肠癌中PD-L1的表达变化。结合肿瘤组织18F-FDG的SUV值、免疫浸润程度、淋巴细胞分布、细胞因子水平以及免疫相关基因突变频率和表达水平，研究PD-L1分子影像学指标与免疫治疗反应的相关性。基于朴素贝叶斯算法构建综合的预后和治疗反应的预测模型，并提供基于分子影像学特征筛选结直肠癌PD-L1免疫治疗相关生物学标志物的医学影像辅助诊断平台，有利于患者免疫治疗的选择和临床医生精准制定治疗策略。

Molecular imaging with antibodies as a probe is a new method for noninvasive dynamic detection of colorectal cancer. Immune checkpoint PD-1/PD-L1 is an important mechanism of tumor tolerance in colorectal cancer. Precise monitoring of PD-L1 expression level in tumor tissues is helpful for the selection of targeted immunotherapy for patients and timely evaluation of efficacy and prognosis. Our group successfully prepared optical imaging agent NIR-PD-L1-mAb and detected the expression of PD-L1 in different colorectal cancer cells and animal models. On this basis, PD-L1 antibody PET and Cerenkov optical molecular probes were prepared using radionuclide 89Zr and 131I, respectively, to detect the dynamic changes of PD-L1 expression in colorectal cancer. The correlation between PD-L1 molecular imaging and immunotherapy response was studied based on the SUV value, immune infiltration, lymphocyte distribution, cytokine levels and mutation frequencies and expression levels of immune-related genes in 18F-FDG of tumor tissues. Based on Naive Bayesian Algorithm, a comprehensive prediction model of prognosis and treatment response was built, and a medical imaging auxiliary diagnosis platform for screening biomarkers relative to colorectal cancer PD-L1 immunotherapy based on molecular imaging features, which is helpful for seletion of patients immunotherapy and clinicians to develop precise treatment strategies.