Objective: To investigate the value of conventional MRI plane scan/enhancement and diffusion weighted imaging (DWI) in the diagnosis of nasopharyngeal carcinoma (NPC) after radiotherapy. Materials and Methods: Three hundred and eighty patients proved nasopharyngeal carcinoma by biopsy were collected in our hospital. All patients were treated with radiation therapy and received a regular follow up ranging from 6 months to 3 years and MRI scan for no less than one time. Conventional MRI examinations including plan scan and Gd-DTPA enhancement, and 168 patients were scanned with DWI. Results: During the follow up, 32 patients were confirmed NPC recurrence after radiotherapy. New occurred tumors showed irregular shapes, iso-or slightly low signal on T1WI, iso-or slightly higher signal on T2WI, and moderate to obvious enhanced after contrast medium administrated. Nineteen cases were found newly occurred bone destruction in the skull base, and 12 cases were found lymph node enlargement. On DWI, recurred tumors showed moderate or high signals, and the ADC value was (0.96±0.08)×10-3 mm2/s. While most none recurrence cases showed iso-or slightly high signal while some showed slightly low signal on DWI, and the ADC value was (1.31±0.16)×10-3 mm2/s, and the difference of ADC value between two groups has statistical significance (P<0.05). Conclusion: MRI enhancement and DWI have great value in the diagnosis of recurrence of nasopharyngeal carcinoma after radiotherapy.%目的：探讨磁共振平扫和增强扫描及弥散加权成像(diffusion weighted imaging, DWI)对鼻咽癌放疗后复发的诊断价值。材料与方法收集惠州市中心人民医院经病理证实为鼻咽癌并接受放射治疗的病例共380例，所有患者在放疗结束后进行6月至3年的随访复查并接受至少1次以上磁共振检查，常规进行MRI平扫和增强扫描，其中168例行DWI扫描。结果在复查过程中，共有32例证实为放疗后复发，复发的肿块形态不规则，T1WI呈等、稍低信号，T2WI呈等或稍高信号，增强后呈中等-明显强化，其中19例伴有新发颅底骨质破坏，12例伴有新增淋巴结肿大。复发肿块DWI呈高或稍高信号，其表观弥散系数(apparent diffusion coefficient, ADC)值为(0.96±0.08)×10-3 mm2/s；无复发者DWI大部分呈等、稍高信号，部分呈稍低信号，其ADC值为(1.31±0.16)×10-3 mm2/s，二者ADC值组间差异有统计学意义(P＜0.05)。结论 MRI增强和DWI成像对鼻咽癌放疗后复发诊断具有重要价值。
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