腮腺分区勾画方式对鼻咽癌IMRT计划靶区及腮腺剂量的影响

Effect of Split-Parotid Delineation Approaches on Target and ParotidGland of IMRT in Patients with Nasopharyngeal Carcinoma

目的探索三种腮腺分区勾画方式对鼻咽癌调强放疗计划中靶区及腮腺剂量影响。方法选取4例鼻咽癌患者(T_2N_2M_0,III期),每例分别制作4组调强放疗计划(计划~0,计划~1,计划~2,计划~3),除腮腺以外,靶区处方剂量及其余危及器官限制剂量均相同。评估4组计划中靶区及危及器官剂量,特别是腮腺剂量。结果4组计划均符合靶区及正常组织剂量限制要求,腮腺分区勾画组(计划~1,计划~2,计划~3)两侧腮腺D_(mean)均低于腮腺整体勾画组(计划~0);计划~2两侧腮腺D_(mean)<30 Gy,D_(50)<26 Gy,均低于计划~0,且能最大程度降低左右侧腮腺D_(mean)和D_(50)。结论在满足靶区及正常组织剂量限制要求前提下,腮腺分区勾画方式2能显著降低腮腺平均剂量及50%体积剂量,此种腮腺分区勾画方式能否减轻放疗对腮腺分泌功能的损伤值得进一步研究。

Objective To explore the effect of three parotid gland zoning delineation methods on the target area and parotid gland dose in the intensity modulated radiotherapy plan for nasopharyngeal carcinoma. Methods A total of 4 patients with nasopharyngeal carcinoma (T2N2M0, stage III) were selected, and each patient was prepared with 4 groups of intensity modulated radiotherapy plan (plan 0, plan 1, plan 2, plan 3). Except for the parotid gland, the prescribed dose in the target area and the restricted dose of other organs at risk were the same. The target area and organ at risk dose, especially parotid dose, were evaluated in 4 groups. Results All the plans in the 4 groups met the dose limitation requirements of the target area and normal tissue. The Dmean of both sides of parotid gland in the parotid gland delineation group (plan 1, 2, 3) was lower than that in the parotid gland delineation group (plan 0). Plan 2 both sides of the parotid gland Dmean<30 Gy, D50<26 Gy, were lower than plan 0, and could minimize the left and right side of the parotid gland Dmean and D50. Conclusion Under the premise of meeting the dosage requirements of target and OARs, split-parotid delineation by approach 2 is likely to minimize Dmean and D50 of parotid gland significantly. Whether the delineation approach can reduce the radiation-induced parotid gland function damage is worth further research.