中文摘要：

目的：分析鼻咽癌治疗前瘤灶、复发瘤及放疗后非复发瘤的MR表观扩散系数（apparent diffusion coefficient， ADC）值差异，探讨磁共振扩散加权成像（diffusion-weighted imaging，DWI）对鼻咽癌及其复发瘤的诊断价值，并研究其ADC诊断阈值对鼻咽癌的诊断效能。方法收集鼻咽癌治疗前患者（初诊组）103例、放疗后局部复发患者（复发组）39例和放疗后非复发患者（非复发组）51例，分别行常规MR平扫、增强扫描及DWI序列（b=0、800 mm2/s）扫描检查，采用单因素方差分析3组ADC值的差异性；绘制受试者工作曲线（ROC）并对3组病例数据进行分析，确定鼻咽癌初诊组和复发组的ADC诊断阈值，分别计算其诊断鼻咽癌治疗前瘤灶、放疗后鼻咽部复发瘤和放疗后非复发瘤的敏感性、特异性以及约登指数，比较二者ADC诊断阈值的诊断效能。结果非复发组与初诊组、复发组患者的ADC值比较，差异均有统计学意义（P均约0.05）；复发组与初诊组患者ADC值的差异无统计学意义（P跃0.05）。采用常规MRI检查诊断鼻咽癌复发瘤时，其诊断的敏感性和特异性分别为71.8%和74.5%；取0.851×10-3 mm2/s作为初诊组的ADC诊断阈值时，其对治疗前瘤灶诊断的敏感性、特异性和约登指数分别为98.0%、94.9%和0.929，对复发瘤诊断的敏感性、特异性和约登指数分别为76.9%、98.0%和0.749；取0.887×10-3 mm2/s作为复发组ADC诊断阈值时，其对复发瘤诊断的敏感性、特异性和约登指数分别为87.2%、94.1%和0.813。采用Z检验对3种检查法诊断鼻咽癌复发瘤的结果进行差异性分析，显示其中MR DWI复发组ADC诊断阈值对鼻咽癌复发瘤的诊断效能最高（Z=2.044，P=0.041）。结论 DWI有助于鼻咽癌及其复发瘤的检出及诊断，且较常规MRI具有更高的诊断效能；通过鼻咽癌复发组获得的ADC诊断阈值较通过鼻咽癌初诊组获得的ADC诊断阈值对?

英文摘要：

Objective To investigate the diagnostic value of diffusion-weighted magnetic resonance imaging （MRI） and different apparent diffusion coefficients for primary and recurrent nasopharyngeal tumors. Method A total of 103 newly diagnosed patients prior to treatment,39 patients who experienced local recurrence after radiotherapy and 51 patients who experienced fibrosis after radiotherapy underwent routine,enhanced and diffusion-weighted MRI sequence scanning （b=0.800 s/mm2）.The apparent diffusion coefficient（ADC）obtained for each group of patients was compared using ANOVA,and receiver operating characteristic（ROC）curves were plotted to determine the threshold ADC value for confirming a diagnosis of nasopharyngeal carcinoma and for diagnosing recurrence. The diagnostic sensitivity,specificity and Youden index were compared for routine and diffusion-weighted MRI. Results The ADC＆amp;nbsp;value differed significantly between the fibrosis group and the two other groups（P〈0.05）,but not between the recurrence group and newly diagnosed group（P〉0.05）.Based on a diagnostic threshold of 0.851×10-3 mm2/s from the newly diagnosed group,the sensitivity, specificity and Youden index were 98.0%,94.9%,and 0.929 for the newly diagnosed group and 76.9%,98.0%,and 0.749 for the recurrence group.Based on a diagnostic threshold of 0.887×10-3 mm2/s,the sensitivity,specificity and Youden index of the recur-rence group were 87.2%,94.1% and 0.813. Conclusions Diffusion-weighted MRI shows promise for detecting and diagnosing new and recurrent nasopharyngeal carcinoma;its diagnostic efficiency was higher than that of conventional MRI in our cohort.The ADC threshold value obtained from the recurrence group showed higher performance for diagnosing recurrent tumor than did the ADC value obtained from the newly diagnosed group.