摘要目的：探讨3.0T磁共振（MRI）弥散加权成像（DWI）在评价进展期胃癌新辅助化疗效果中的临床应用价值。方法对经超声胃镜及病理确诊的42例进展期胃癌患者进行3.0T MRI DWI检查，其中32例患者在新辅助化疗前后均进行了DWI检查，分析DWI对胃癌病灶、胃周淋巴结的显示能力，通过测量正常胃壁与肿瘤累及区域的表观弥散系数（ADC）值比较两者之间的差异性；对同一患者新辅助化疗前后肿瘤ADC值进行比较，并与术后病理结果进行对比。结果42例患者共进行74次DWI检查，肿瘤和胃周淋巴结在DWI上均呈明显的高信号，肿瘤平均ADC值为（1.348±0.278）×10-3 mm2／s，12例胃周肿大淋巴结平均ADC值为（1.329±0.188）×10-3 mm2／s，而正常胃壁在DWI上表现为低信号，平均ADC值为（2.081±0.189）×10-3 mm2／s，正常胃壁与肿瘤及胃周淋巴结比较差异有统计学意义（P＜0.001）；化疗后肿瘤的ADC值升高，平均（1.572±0.261）×10-3 mm2／s，与化疗前比较差异有统计学意义（P＜0.001）。16例患者新辅助化疗后进行胃癌根治术，术后病理TRG评级肿瘤均有不同程度的消退，肿瘤细胞密度（TCD）化疗前平均为4.45×10-5／px2，化疗并手术后TCD平均为2.48×10-5／px2，与DWI上测得的ADC值呈负相关。结论MRI DWI检查可有效地检测进展期胃癌肿瘤累及范围和胃周淋巴结肿大情况，比较进展期胃癌新辅助化疗前后肿瘤的形态学及ADC值的改变对疗效的评价有一定临床价值。

abstractsObjective To evaluate the clinical value of 3.0T magnetic resonance imaging (MRI) diffusion weighted imaging (DWI) on evaluation effect of neoadjuvant chemotherapy in advanced gastric cancer. Methods 3.0 T MRI DWI examination was performed in 42 cases of advanced gastric cancer diagnosed by gastroscopy and pathology, including 32 patients were examined with DWI both before and after chemotherapy. Lymph nodes of gastric cancer lesions and display ability of stomach were measured, and the area of the apparent diffusion coefficient (ADC) values in normal stomach and tumors were compared. ADC values were compared in the same patients before and after neoadjuvant chemotherapy and analyzed along with postoperative pathological examinations. Results In a total of 40 patients who received 74 DWI examinations, ADC values in tumor and lymph nodes were significantly higher than those in normal tissue. The ADC value in tumors was (1.348 ±0.278) ×10-3 mm2/s, and in 12 cases of stomach lymph node enlargement was (1.329±0.188) ×10-3 mm2/s. However, the average ADC value of normal stomach was (2.081± 0.189) ×10-3 mm2/s with significantly lower DWI than that of the former (P< 0.001). After chemotherapy, the ADC value in tumors was increased, which was (1.572 ±0.261) ×10-3 mm2/s (P< 0.001). After neoadjuvant chemotherapy, 16 patients received gastric cancer radical prostatectomy, and postoperative pathological TRG ratings of tumor were decreased with different extent. Tumor cell density (TCD) before treatment with an&nbsp;average of 4.45 ×10-5 / px2, which was downgraduated to 2.48 ×10-5 / px2 after chemotherapy and surgery. Negatively correlation between TCD values and ADC values were observed. Conclusion MRI DWI examination can effectively detect advanced stomach cancer and the associated lymph node enlargement. Comparison of tumor morphology and ADC values in advanced gastric cancer before and after neoadjuvant chemotherapy has clinical value in prognosis.