新辅助化疗可增大进展期胃癌患者获得根治性切除的机会。目前影像学缺乏有效评价胃癌新辅助化疗疗效的客观手段。本项目拟优化胃癌磁共振多b值扩散加权成像序列参数设置，完善成像技术流程，在此基础上构建反映胃癌组织水分子扩散变化的高斯模型（单指数模型）与非高斯模型（双指数模型和FROC模型）。通过影像病理对照研究，明确各模型参数与微血管密度、细胞密度和组织均匀度的相关性，探索其变化的病理组织学机制，提取能够有效反映胃癌生物学行为特征及新辅助化疗疗效的定量参数。进而通过与术后病理退缩分级及无瘤生存期和生存时间的对照分析，确定磁共振扩散加权成像各模型参数评价胃癌新辅助化疗疗效的阈值和早期敏感时间窗。本项目的目标在于探索一种无创、定量、经济及可重复的早期预测胃癌新辅助化疗效果的方法，为胃癌新辅助化疗个体化的实现提供理论和实践依据。

Neoadjuvant chemotherapy (NACT) can improve the opportunity for radical resection in patients with advanced gastric cancer. There is still lack of effectively radiological method in the response evaluation of gastric cancer to NACT. In this project, we plan to optimize the imaging sequences and parameters of diffusion-weighted MR imaging (DWI) for gastric cancer. On this basis, the Gaussian model (mono-exponential model) and non-Gaussian model (bi-exponential model and FROC model) will be built to reflect the change of water molecular movement in gastric cancer tissue. Then the correlation between parameters generated by non-Gaussian model and microvessel density (MVD), cell density and tissue homogeneity generated by pathology will be investigated through the radiological-pathological comparison; and the histopathological mechanism of the parameter variation will be studied, the quantitative indicators which can reflect the biological behavior of gastric cancer and its change pattern after NACT will be extracted. Finally we want to define the thresholds and time-window of various non-Gaussian models to evaluate the response of NACT through the comparison with tumor regression grading, relapse-free survival time and overall survival time. The goal of this projection is to explore non-invasive, quantitative, economical and repeatable early response evaluation biomarkers for the NACT of gastric cancer, through which to provide theoretical and practice basis for the achievement of personalized medicine.