TomoDirect技术在鼻咽癌放疗中的剂量学研究

Dosimetric study of Tomo Direct technology in radiotherapy for nasopharyngeal carcinoma

目的:研究鼻咽癌患者应用Tomo Direct(TD)、Tomo Helical(TH)及常规加速器固定野调强技术(FF-IMRT)设计的计划的剂量学差异。方法:选取10例鼻咽癌患者,对患者CT图像分别设计TH、TD和FF-IMRT计划,评估靶区、危及器官和正常组织的剂量分布。采用单因子方差分析法比较TH、TD、FF-IMRT计划的剂量学参数差异,并用LSD法进行两两比较。结果:TD技术设计的计划,靶区剂量学与TH、FF-IMRT无明显差异;危及器官保护与TH相似,相比于FFIMRT,脊髓最大剂量降低约4 Gy(P=0.000);腮腺平均剂量降低约20%(P=0.000),D33、D50、D60显著低于FF-IMRT(P=0.000);口腔、喉的平均剂量分别比FF-IMRT降低约7 Gy(P=0.000)和20 Gy(P=0.000);颞颌关节的最大剂量比FFIMRT降低10 Gy(P=0.000);而在视神经、视交叉的保护上,TD与TH均不如FF-IMRT;靶区外正常组织受照剂量,TD计划具有一定优势。结论:鼻咽癌患者TD计划的剂量学参数与TH计划相似,整体优于FF-IMRT计划,完全满足临床剂量学要求,可以作为一种新的治疗手段。

Objective To evaluate the dosimetric differences of Tomo Direct（TD）, Tomo Helical（TH） and fixed-field intensitymodulated radiotherapy（FF-IMRT） plans for nasopharyngeal carcinoma（NPC）. Methods Ten patients with NPC were enrolled in this study, and based on their CT images, three plans were designed for each patient, namely TH, TD and FF-IMRT plans. The dose distribution in target areas, organs-at-risk and normal tissues were evaluated. Furthermore, the dosimetric differences were compared among three plans by single factor analysis of variance, and compared in pairs by LSD method. Results For dosimetric parameters in target areas, TD plans didn＇t showed any statistical differences with TH and FF-IMRT plans. TD and TH plans showed significant improvement over IMRT plans in terms of OAR protection. Compared with FF-IMRT plan, the maximum dose of spinal cord in the other two plans was reduced by about 4 Gy（P=0.000）; the mean dose of parotid gland was decreased by about 20%（P=0.000） and the D33, D50 and D60 were significantly lower（P=0.000）; the mean dose of oral cavity and larynx were reduced by about 7 Gy and 20 Gy, respectively（P=0.000, 0.000）; and the maximum dose of temporomandibular joint was lower by 10 Gy（P=0.000）. However, FF-IMRT plan was superior to TD and TH plans in the protection of optic nerve and chiasm. Besides, TD plans showed certain advantages in the irradiation dose of the normal tissues outside the target areas.Conclusion For patients with NPC, the differences in dosimetric parameters between TD and TH plans were trivial, and both TD and TH plans showed significant improvements over IMRT plans, completely meeting the clinical requirements. TD technology is feasible to treat patients with NPC.