体素内非相干运动DWI直方图表征胰腺癌异质性的作用及临床意义研究

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.

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。

磁共振扩散加权成像（DWI）是临床上广泛应用的功能成像方法之一，无需对比剂，DWI可无创地测量组织内水分子扩散，反映组织结构和功能变化。利用单e指数（mono-exponential）模型，可以定量计算表观扩散系数（ADC），利用体素内非相干运动模型（IVIM）模型，计算公式为：Sb/ S0 = f *exp(-bD*) + (1 –f) • exp(-bD)可以同时获得灌注和扩散信息。D*是快速扩散即灌注系数，D是慢速扩散系数D，以及灌注对应的比例系数f。DWI提供了常规MRI（如T1和T2加权成像）无法获得的组织微观结构信息，可用于肿瘤的良恶性鉴别、疗效评估和早期发现，其在胰腺疾病诊断中已表现出较好的应用价值。.本项目基于单指数DWI及IVIM DWI在胰腺肿瘤应用中具有临床价值，但存在数据分析及参数测量不方便及快速、正常胰腺组织与胰腺癌可重复性测量误差未明确以及DWI方法在胰腺癌病理特征预测及预后评价作用等不明确等问题。基于以上问题，本项目进行了以下几个方面研究：.①开发了磁共振IVIM-DWI直方图分析软件一套：实现包括优化的图像配准方法、IVIM-DWI模型计算算法和直方图分析工具的图像后处理软件；实现两维及三维数据直方图分析功能和测量结果Excel自动输出功能。.②纳入正常志愿者34例和胰腺癌患者50名，进行IVIM-DWI重新摆位后扫描的可重复性成像及直方图数据分析，探究三种ROI方法（“整体容积法”、“单一层面法”和“小样本法”）的直方图分析评估正常胰腺和胰腺癌定量指标的可重复性和一致性。.③分析胰腺癌患者临床和病理资料，探究IVIM-DWI直方图指标与肿瘤位置、分化程度的相关性。.④比较了重复性好的DWI直方图参数在胰腺癌与正常胰腺组织中的差异，并比较了不同参数诊断两者的效能差异。.⑤探究了IVIM-DWI直方图定量指标在预测可切除胰腺癌患者淋巴结转移状态的价值。发现ADC能量值与有无淋巴结转移相关。.项目按照原计划顺利完成，并取得了一定的成果，达到了预期目标。