Wu W C Vincent, Mui Wing-Lun A, Fung Wing-ki W
Department of Health Technology and Informatics, Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
Med Dosim. 2010 Summer;35(2):122-7. doi: 10.1016/j.meddos.2009.04.001. Epub 2009 May 7.
Helical tomotherapy uses different planning algorithm and dose delivery method from the linear accelerator (linac)-based intensity-modulated radiotherapy (IMRT). This study compared the dosimetric outcomes between the tomotherapy plans and conventional linac-based IMRT plans in the treatment of nasopharyngeal carcinoma (NPC). Fifteen stage II-III cancer (American Joint Committee on Cancer) NPC patients treated by tomotherapy were conveniently recruited. Apart from the tomotherapy plans, a 7-field 6-MV photon conventional IMRT plan was computed for each patient with the same CT dataset and reference from the dose constraints and target dose prescriptions of the tomotherapy plans using the XiO treatment planning system. Average values of the dose parameters including the conformity index (CI), homogeneity index (HI), maximum and minimum doses of the target volumes, and the maximum and mean doses of the organs at risk (OAR) were compared between the two treatment methods. Better dose coverage of the planning target volume (PTV) was demonstrated in the tomotherapy plans, in which the differences in the maximum and mean doses reached statistical significance (p < 0.05). Besides, the CI of the tomotherapy plans were significantly higher than the conventional linac-based plans for the nasopharynx PTV (NP-PTV) and neck lymphatics PTV (LN-PTV) (p = 0.017 and 0.010, respectively). The HI was significantly smaller in both NP-PTV and LN-PTV (p = 0.024 and < 0.001, respectively). Among the OAR, the brain stem and spinal cord doses in the tomotherapy plans were lower than that of the conventional IMRT plans. However, the doses to the other OAR did not show significant dosimetric differences. In the treatment of nasopharyngeal carcinoma, tomotherapy plans were superior to the 7-field conventional IMRT plans in PTV dose conformity and homogeneity and the sparing of the brain stem and spinal cord. However, no significant advantages were observed for the rest of the OAR.
螺旋断层放射治疗使用的计划算法和剂量传递方法与基于直线加速器（直线加速器）的调强放射治疗（IMRT）不同。本研究比较了断层放射治疗计划与传统基于直线加速器的IMRT计划在鼻咽癌（NPC）治疗中的剂量学结果。方便地招募了15例接受断层放射治疗的II - III期癌症（美国癌症联合委员会）NPC患者。除了断层放射治疗计划外，使用XiO治疗计划系统，针对每位患者，根据相同的CT数据集，并参考断层放射治疗计划的剂量限制和靶区剂量处方，计算了一个7野6兆伏光子常规IMRT计划。比较了两种治疗方法之间剂量参数的平均值，包括适形指数（CI）、均匀性指数（HI）、靶区体积的最大和最小剂量，以及危及器官（OAR）的最大和平均剂量。断层放射治疗计划显示出对计划靶区（PTV）更好的剂量覆盖，其中最大和平均剂量的差异具有统计学意义（p < 0.05）。此外，断层放射治疗计划对于鼻咽PTV（NP - PTV）和颈部淋巴结PTV（LN - PTV）的CI显著高于传统基于直线加速器的计划（分别为p = 0.017和0.01）。NP - PTV和LN - PTV中的HI均显著更小（分别为p = 0.024和< 0.001）。在OAR中，断层放射治疗计划中脑干和脊髓的剂量低于传统IMRT计划。然而，其他OAR的剂量在剂量学上没有显示出显著差异。在鼻咽癌的治疗中，断层放射治疗计划在PTV剂量适形性和均匀性以及脑干和脊髓的保护方面优于7野常规IMRT计划。然而，对于其余的OAR没有观察到显著优势。
