Abstract: Objective To explore the diagnostic value of synchrotron radiation X-ray phase contrast imaging compared with magnetic resonance imaging (MRI) in early diagnosis of pancreatic cancer with an orthotopic xenograft nude mice model of pancreatic cancer. Methods Thirty-two female nude mice were divided into 2 groups of 4 subgroups randomly, subgroups were labeled A1, A2, A3, A4 (n=6) and B1, B2, B3, B4 (n=2) as the different intervals at 1, 2, 3, and 4 weeks postoperatively, respectively. 10⁸ cells/mL×20μL PANC-1 cell suspension was injected into pancreatic capsula of group A but 20μL sterile saline was injected in the group B. MRI scans were performed at 1, 2, 3, and 4 weeks postoperatively and the specimens were excised from nude mice and fixed in 10% formalin immediately. Synchrotron radiation X-ray phase contrast imaging was performed followed by histopathological examination. Results ①Low grade adenocarcinoma was confirmed with pathology, and the average rate of tumorigenesis in group A was 73% (16/22), and the rate was the highest after 4 weeks, which was 100%. With the time passing, the rate of tumorigenesis increased with the linear trend test (χ²=4.718, P=0.030). ②The image of tumor with a diameter of 0.5 mm in pancreas was observed with synchrotron radiation phase contrast imaging. The sensitivity and specificity of the early (two weeks) reached 100%, significantly higher than that of magnetic resonance imaging (P=0.029). Conclusion PANC-1 cells injected into pancreatic capsula was a reliable method for establishment of pancreatic cancer model. Compared with MRI, synchrotron radiation contrast imaging could detect tiny lesions of pancreatic cancer, which may provide a new method for early diagnosis of pancreatic cancer.

Key words: pancreatic cancer, animal model, orthotopic transplantation, synchrotron radiation X-ray phase contrast imaging, magnetic resonance imaging