磁共振扩散加权成像ADC全容积直方图评估胃癌化疗疗效

Gastric cancer is a common gastrointestinal malignancy. Chemotherapy is the preferred method for patients with gastric cancer who have lost the opportunity of operation. CT and PET-CT, as traditional examination methods, can not show the boundary of gastric cancer clearly, it limits the evaluation of chemotherapy response in gastric cancer. Our previous studies have confirmed that gastric cancer lesions show high signal intensity in magnetic resonance diffusion weighted imaging (MRDWI) contrast to normal stomach wall, which provides the basis for the boundary outlining and volume measurement of gastric cancer. In addition, some studies have revealed that apparent diffusion coefficient (ADC) value of MRDWI could early evaluate the chemotherapy response in gastric cancer, but ADC values in those studies were measured by outlining two-dimensional region of interest, which can just reflect partial information of the entire tumor. ADC whole-volume histogram analysis can show frequency distribution and percentage of different ADC values in volume of interest, which can display the diffusion information of water molecular and tumor heterogeneity fully. To provide valuable reference for choosing accurate chemotherapy method in patients with gastric cancer, our study plans to develop and improve ADC whole-volume histogram parameters (such as percentiles, volume, entropy etc.) to evaluate the chemotherapy response in nude mice model and patients with gastric cancer, explore its inherent law, and then look for new sensitive and effective parameters to evaluate chemotherapy response in gastric cancer.

胃癌是常见的消化道恶性肿瘤。失去手术机会的胃癌，化疗是首选方法。传统检查方法CT、PET-CT对胃癌边界显示不清，评估化疗疗效存在局限性。本课题组前期研究显示胃癌病灶在磁共振扩散加权成像上呈高信号，与正常胃壁形成良好对比，为胃癌的边界勾画及体积测量提供了基础。此外有研究显示，磁共振扩散加权成像表观扩散系数（ADC）值可早期评估胃癌化疗疗效，但ADC值测量方法采用二维感兴趣区勾画取均值，只能反应肿瘤局部信息。ADC全容积直方图分析能够展示感兴趣容积内不同ADC值的频数分布及比例，全面显示肿瘤水分子扩散信息和肿瘤的异质性。本研究通过开发和完善ADC全容积直方图参数（百分位数、体积、熵值等参数），并对裸鼠胃癌化疗模型及胃癌化疗患者进行疗效评估，探索其内在规律，寻找胃癌化疗疗效评估敏感有效的新参数，为胃癌化疗患者选择准确的化疗方案提供有效的参考。

胃癌是最常见的消化道恶性肿瘤之一，其发病率高。对于失去手术机会的胃癌，姑息化疗是首选方法。如何早期准确评估胃癌患者化疗敏感性及疗效是受到广泛关注的问题。MR具有无电离辐射、软组织分辨率高的优点。MR扩散加权成像可以用ADC值量化水分子的扩散程度。全容积直方图分析能够展示感兴趣容积内不同像素灰度分布及比例，可以提供多参数，全面显示肿瘤的异质性。本项目进一步开发和完善ADC全容积直方图软件参数，并应用在胃癌ADC图上，证明了ADC一阶熵和二阶熵均与胃癌的T，N和总分期存在显著相关性，其中一阶熵相关性最高（r=0.588，0.585，0.677）。本项目建立ADC全容积直方图评估裸鼠胃癌化疗疗效模型，并发现ADC全容积直方图参数可以成为定量评估胃癌疗效的有效工具。近年来该领域技术发展迅速，主要朝着多模态参数分析的趋势发展，本项目进一步开发直方图软件功能，可以分析多模态图像。本项目研究发现，CT直方图及纹理分析可用于监测胃癌患者对化疗的早期治疗反应。在进展组和非进展组胃癌患者间，75th percentileP2, 90th percentileP2和Δinertia_12V均存在显著差异，maxA1, skewnessV1和ΔskewnessV在治疗有效组（部分缓解或完全缓解）和无效组（稳定或进展）胃癌间也存在显著差异。上述参数在预测胃癌患者化疗疗效中均表现良好（AUC=0.754-0.832），多变量模型则表现出更好的预测效能（AUC=0.882，0.781）。