胰腺癌5年生存率不足5%，早期发现、有效评估及采取恰当的治疗十分关键。体素内非相干运动（IVIM） MR扩散加权成像（DWI）能无创地测量组织内水分子扩散和血流灌注，其诊断胰腺癌准确性优于单指数DWI。DWI定量参数的测量常规基于感兴趣区（ROI）平均值的方法，已广泛应用于各类肿瘤的检测和评估。但基于ROI平均值完全丢弃了肿瘤异质性信息，而肿瘤异质性的有效评估有利于观测肿瘤的发生、发展、转归及生物学行为。直方图分析能获得除均值外参数分布的峰度、偏度及均一性等定量指标，可用于肿瘤异质性评价，该方法目前主要应用于颅内病变，IVIM-DWI直方图分析在胰腺癌方面未见报道。本项目拟在前期工作基础上，利用IVIM-DWI参数的直方图分析探究胰腺癌异质性，并尝试预测可切除性胰腺癌患者淋巴结转移和生存期。项目的完成将为胰腺癌诊断和评估提供新型影像手段，并为腹部其他器官IVIM-DWI研究提供方法学参考。

Pancreatic cancer is one of the most common malignant tumors of the digestive system, with a 5-year survival rate of less than 5%. Early diagnosis, effective assessment and proper treatment of pancreatic cancer is the key to improve survival rate of the diseases. Intravoxel Incoherent Motion (IVIM) MR diffusion weighted imaging (DWI) can noninvasively measure the molecular movement of water (diffusion) and microcirculation of blood in the capillaries (perfusion), and has higher diagnostic accuracy than conventional monoexponential DWI in the diagnosis of pancreatic cancer. The conventional method for the quantitative measurements of the DWI derived parameters was drawing region of interest (ROI) within the tumor to measure mean values, which have been widely used in the detection and evaluation of various tumors. However, the mean values based on the ROI cannot reflect the tumor heterogeneity, which are able to observe the occurrence, development and biological behaviors of tumors. Histogram analysis can obtain the mean values, kurtosis, skewness, uniformity, et al, and can be used to assess the tumor heterogeneity. Histogram analysis is mainly used in the studies of intracranial lesions. IVIM-DWI with histogram analysis has not been used to investigate pancreatic cancer. Based on previous work, IVIM-DWI with histogram analysis will be performed to explore the heterogeneity of pancreatic cancer in this project, and will be used to predict the lymph node metastasis status and survival for the resectable pancreatic cancer patients. The project will provide new imaging method for the diagnosis and evaluation of pancreatic cancer, and provide methodology reference for future studies of other abdominal organs by using IVIM-DWI.