对于长期生存的鼻咽癌患者，放射诱发肿瘤（radiation-induced malignancy,RIM）的发生是一个不容忽视的问题。与常规放疗相比，调强适形放射治疗（intensity-modulated radiotherapy,IMRT）可显著提高鼻咽癌疗效、延长生存，但由于散射漏射的增多和正常组织低剂量受照体积的显著增加，有可能会增加RIM的发生风险。由于IMRT应用时间尚短，我们无法通过流行病学调查得到IMRT对RIM发病风险影响的确切答案。本研究拟通过蒙特卡罗计算法和热释光剂量探测系统综合分析常规放疗、IMRT治疗鼻咽癌时正常器官的等效剂量；将常规放疗时各器官的剂量数据与本课题组前期研究中RIM的临床资料相结合，建立RIM发病风险的预测模型，并分析放射物理因素对风险的影响，为鼻咽癌临床诊治过程中放疗方案和随访策略的选择提供理论基础，从物理方向对RIM进行有效的一级和二级预防。

The increasing incidence of radiation-induced malignancies (RIM) has become a major concern among long-term nasopharyngeal carcinoma (NPC) survivors. Compared with conventional radiotherapy (CRT), intensity-modulated radiotherapy (IMRT) has significantly improved the efficacy and prolonged the survival in NPC patients. However, IMRT may increase the risk of RIM with regard to the more leakage, scatter radiation and a much greaterer volume of normal tissues to low doses of irradiation. Due to the short-term application, we can not determine whether IMRT indeed increases the incidence of RIM through epidemiological investigation. This study was designed to determine the equivalent dose of normal organs using Monte Carlo calculations and thermoluminescent dosimeter measurements for CRT and IMRT. Based on the organ doses for CRT and the clinical data in preliminary study of our group, we will establish a risk prediction model for RIM following NPC and analyze the potential physical factors that influence the risk. The objectives of our research were to determine the theoretical basis for the selection of radiotherapy modalities and follow-up strategy and to provide an opportunity for effective primary and secondary prevention from physical direction.