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目的利用三维治疗计划系统对早期鼻咽癌常规和三维适形放疗(3DCRT)计划作剂量学比较,评估不同照射方法剂量分布的差异,为今后指导临床治疗提供剂量学的依据。方法选择22例早期鼻咽癌患者,用三维治疗计划系统对每例患者分别作出常规和3DCRT计划设计,然后根据靶区覆盖率(V95)、正常组织受量(D50,D33和D5等)和正常组织并发症发生率(NTCP)比较这两种计划。结果剂量学比较表明,常规和3DCRT的PTVnx70、PTVnd60、PTVnx60、PTVnx50的V95分别为98.22%和99.98%(P=0.06)、98.41%和99.63%(P=1.00)、98.22%和99.98%(P=0.03)、98.85%和99.63%(P=0.02)。保护正常组织方面:在3DCRT和常规计划中,单侧腮腺的D50分别为51.91Gy和64.30Gy(P=0.00),单侧颞颌关节D50,49.98Gy和64.47Gy(P=0.00),脊髓D1cc,44.98Gy和48.09Gy(P=0.00)。结论3DCRT在亚临床靶区比常规方法有稍好的靶区覆盖率,3DCRT治疗早期鼻咽癌的优势在于给予靶区相似剂量分布的前提下,可以比常规方法减少某些正常组织器官如腮腺、颞颌关节等照射剂量,减少它们的NTCP。
OBJECTIVE: To compare the dosimetry of conventional and three-dimensional conformal radiotherapy (3DCRT) plans for nasopharyngeal carcinoma with three-dimensional treatment planning system to evaluate the difference of dose distribution among different irradiation methods and to provide basis for the future clinical therapy. Methods Twenty-two patients with early-stage nasopharyngeal carcinoma (NPC) were enrolled in this study. Conventional and 3DCRT plans were designed for each patient with three-dimensional treatment planning system. Based on the target area coverage (V95), normal tissue exposure (D50, D33 and D5, etc.) The normal tissue complication rate (NTCP) compares these two plans. Results The comparison of dosimetry showed that the V95 of PTVnx70, PTVnd60, PTVnx60 and PTVnx50 were 98.22% and 99.98% (P = 0.06), 98.41% and 99.63% (P = 1.00), 98.22% and 99.98% = 0.03), 98.85% and 99.63% (P = 0.02). Protection of Normal Tissue: In 3DCRT and routine planning, the unilateral parotid D50 were 51.91 Gy and 64.30 Gy, respectively (P = 0.00), unilateral temporomandibular joint D50, 49.98 Gy and 64.47 Gy (P = 0.00), spinal D1cc , 44.98Gy and 48.09Gy (P = 0.00). Conclusions 3DCRT has a slightly better target area coverage in subclinical target area than conventional methods. The advantage of 3DCRT in treating early stage nasopharyngeal carcinoma is that it can reduce some normal tissues and organs such as parotid gland , Temporomandibular joint irradiation dose, reduce their NTCP.