磁共振扩散加权成像ADC直方图评估胃癌异质性及其淋巴结转移

Gastric cancer is one of the most common malignant tumor of digestive tract all over the world, accounting for the second cause of cancer-related death. Preoperative diagnosis and assessment of gastric cancer mainly rely on barium meal, endoscopic ultrasonography and CT examination. Magnetic resonance imaging shows high resolution of soft tissues, without radiation, and can provide plenty of diagnostic information. Diffusion weighted magnetic resonance imaging (DWI) could detect the Brownian motion of water molecule in vivo and noninvasively. DWI has been widely used in detection and assessment of various body tumors. DWI of the stomach, a hollow viscera, is somewhat challenging. Domestic and international preliminary studies show that DWI has a unique value in detection and assessment of gastric cancer. Quantitative analysis method in DWI is to draw a region of interest (ROI) and obtain the mean apparent diffusion coefficient (ADC) value. It was reported that the ADC value of gastric cancer was significantly lower than that of normal gastric wall. However, mean ADC value based on ROI measurement can not reflect the heterogeneity of gastric lesion. The ADC histogram can characterize the internal structures of the lesions more comprehensively. This method is mainly used in brain lesions without any report on gastric cancers. Our team has accumulated rich experience in DWI of gastric cancers, and got some achievement. The aim of this study is to analyze the heterogeneity of gastric cancer with ADC histogram analysis, and try to identify and predict the lymph node metastasis.

胃癌是全球最常见的消化道恶性肿瘤之一，占癌症相关死亡原因的第2位。胃癌的术前诊断和评估目前主要依赖钡餐造影、超声内镜和CT检查。磁共振软组织分辨率高，无辐射，能够提供更加丰富的诊断信息。磁共振扩散加权成像（DWI）能够在活体内无创检测水分子的扩散运动，目前已被广泛运用于全身各种肿瘤的检测和评估。胃为空腔脏器，DWI成像存在一定的困难。国内外初步研究表明，DWI在胃癌的检测、评估方面具有独特的价值。DWI定量分析方法是在病灶内画感兴趣区（ROI），获取平均表观扩散系数（ADC）值。研究发现，胃癌的ADC值显著低于正常胃壁。但是基于ROI的平均ADC值无法反映胃癌病灶的异质性。ADC直方图能够更加全面地刻画病灶内部的结构特征。该方法目前主要应用于颅脑病变，胃癌方面未见报道。本研究拟采用ADC直方图分析胃癌病灶的异质性，并尝试鉴别和预测其淋巴结转移。

胃癌是全球最常见的消化道恶性肿瘤之一。磁共振检查无辐射，软组织分辨率高，目前已越来越多地用于胃癌的术前评估。磁共振扩散加权成像（DWI）在其他肿瘤中已证实可以反映肿瘤的微结构和微环境信息，但在胃癌中还未见系统研究。本项目对胃癌患者行3.0T磁共振DWI成像（b=0、1000 sec/mm^2）获得ADC图，并获得一系列直方图参数。除ADCmax外的所有直方图参数均显示出优良的观察者间一致性，其组间相关系数高于0.800。研究发现低分化和高分化胃癌的第5，第10，第25和第50百分位数，偏度和峰度存在显著性差异。胃癌分化程度与直方图参数之间存在显著相关性。不同T和N分期胃癌的所有ADC直方图参数均存在显着差异。大多数直方图参数（除ADCmax外）区分胃癌不同T、N分期表现良好，特别是第10百分位数预测有无淋巴结转移的AUC达到0.794（95％置信区间，0.677-0.911）。偏度预测有无淋巴结转移的AUC达到0.802。反映病灶异质性和混乱度的熵相关参数与T，N和总分期显著相关，尤其是一阶熵（r = 0.588,0.585和0.677，均P <0.05）。所有熵相关参数均显示胃癌在不同T，N和总分期以及不同血管侵犯状态下的显著差异（P <0.001-0.027）。包括熵，熵（H）0，熵（H）45和熵（H）90在内的四个参数显示有和没有神经侵袭的胃癌之间的显著差异（P = 0.006-0.040）。总之，基于整个肿瘤体积的ADC直方图分析可用于预测胃癌的组织学分级、T期和N期，其中熵值相关参数可以定量分析肿瘤内异质性，尤其一级熵可用于评估胃癌的侵袭性（包括血管侵犯和神经侵犯），从而有助于在术前对胃癌的生物学行为进行精准评估，从而优化治疗方案并改善预后。