多模态分子影像中，构建简单易得的分子探针十分重要。本研究构建了新型上转换纳米复合材料，利用四氧化三铁纳米粒的磁性能和优异的上转换发光性能（UCL）用于MRI/UCL显像；利用氟离子与稀土金属之间较强的配位作用，简单、快速地实现放射性核素18F的标记，用于PET显像。全面考察探针的理化特性和生物学特性。体外研究分子探针的磁共振强度变化、荧光强度、核素标记后细胞摄取动力学；活体内初步探索荷瘤裸鼠模型的PET/MRI/UCL多模态显像。目前国内外多模态分子探针的开发仍处于早期发展阶段，上转换纳米复合材料平台的建立可突破多模态分子探针构建的重重困难，将为多模态分子探针开辟新的发展道路。这一创新性研究将PET/MRI/UCL三种成像模式进行有机结合，同时满足空间/时间分辨率、灵敏度等多方面的要求，实现优势互补，完美融合结构组织与分子功能的信息，具有良好的临床发展前景。

In multimodality molecular imaging, it is still challenging to obtain a simple molecular probe with easy construction. This study builds a platform of core-shell upconversion nanocomposites with Fe3O4 nanoparticle as core for MRI imaging, upconversion nanophosphors as shell for upconversion luminescence imaging, and labeled 18F for PET imaging. The 18F labeling of upconversion nanocomposites is achieved by their strong coordination with rare earth conveniently. Then the physical, chemical and biological characteristics are overall analyzed. In vitro study, the changes of MRI signal intensity, luminescence intensity and cellular uptake kinetics are investigated. In vivo study, the capability of PET/MRI/UCL multimodality imaging is initially explored in tumor-bearing nude mice model. Nowadays multimodality probes are still in the early stage of development in China and abroad, the platform of upconversion nanocomposites will break through the barriers of constructing multimodality probes and open up a new way for development. This innovative research will integrate PET/MRI/UCL three modalities to realize advantageous complementarities. This will meet the requirements of space, time, sensitivity and quantitation, providing much more redundant anatomy and molecular information to clinic, which has good prospect for development and clinical application.