头颈部肿瘤ART-IMRT四种方案剂量学评估

Dosimetric evaluation of four adaptive IMRT strategies for head-neck cancer

目的 研究头颈部肿瘤ART-IMRT分次放疗中采用不同频次再计划方案时,靶区与OAR解剖结构变化规律,以及对其剂量影响.方法 选取山东省肿瘤医院28例头颈部肿瘤患者入组研究,其中鼻咽癌19例、喉癌4例、上颌窦肿瘤5例,患者均接受常规分割治疗.每周第1天进行1次CBCT扫描作为参考图像,共采集6次.将CBCT与计划CT配准得到＂伪CT＂图像.实施4种再计划方案,无再计划作为参考,分别得到实际剂量与计划预测剂量,并评估两种剂量差异.多组间比较采用非参数Friedman检验,两组间比较采用配对t检验.结果 PTV、CTV、左右腮腺6周中每周体积差异均有统计学意义（P=0.041、0.046、0.024、0.017）.4种再计划方案中两腮腺的实际剂量与计划预测剂量比较P值均〈0.05,且4种方案中两腮腺的两种剂量之间差异与参考方案相比分别下降5.02%、11.17%、12.08%、13.19%.结论 再计划可确保靶区足够剂量,使OAR受量控制在安全范围内;再计划频次越高,实际剂量越接近计划预测剂量,2次再计划方案效率最高.

Objective To investigate the effects of numerous re-planning strategies on the anatomic and dosimetric outcomes of target volume and organs at risk （OARs） in patients with head and neck cancer receiving fractionated radiotherapy.Methods From 2015 to 2016,28 patients with head and neck cancer were enrolled in this study with Shandong Cancer Hospital,consisting of 19 patients with nasopharyngeal carcinoma, 4 patients with laryngocarcinoma, and 5 patients with carcinoma of the maxillary sinus.All of them received conventionally fractionated radiotherapy.Each patient had six weekly cone-beam CT （CBCT） scans, which were performed on the first day of every week, to obtain reference images.A virtual CT image was generated by registration of planning CT and each weekly CBCT image.The four re-planning strategies were used for the reconstruction of re-planned dose, while the initial planning was used as a reference.The weekly doses calculated using virtual CT were summed together to obtain the actual dose.The actual and initial planned doses were evaluated.The nonparametric Friedman test was used to evaluate the differences between multiple groups, and the differences between any two groups were analyzed by paired t test.Results The sizes of planning target volume, clinical target volume, and left/right parotid glands （PGs） changed significantly within the six weeks （P=0.041, 0.046, 0.024, and 0.017, respectively）.For these four re-planning strategies, there were significant differences between the actual dose and the initial planned dose to the PGs （all P〈0.05）, with average values decreased by 5.02%, 11.17%, 12.08%, and 13.19%, respectively, compared with that in the reference strategy.Conclusions Re-planning during treatment course could ensure the sparing of OARs and allow for sufficient dose to the target volume.The higher the number of re-planning strategies, the more the actual dose is close to the initial planed dose;the efficiency of two re-planning strategies is the highest.