鼻咽癌常规放疗面颈联合野照射的剂量学研究  被引量:5

Dose evaluation of conventional radiotherapy using facial-cervical fields in nasopharyngeal carcinoma .

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作  者:张彦新[1] 罗京伟[1] 章众[1] 徐国镇[1] 高黎[1] 戴建荣[1] 易俊林[1] 黄晓东[1] 肖建平[1] 李素艳[1] 

机构地区:[1]中国医学科学院北京协和医学院肿瘤医院肿瘤研究所放疗科,北京100021

出  处:《中华放射肿瘤学杂志》2009年第4期308-311,共4页Chinese Journal of Radiation Oncology

基  金:中国医药卫生发展基金会资助项目(2006)

摘  要:目的利用CT模拟机定位技术及治疗计划系统分析鼻咽癌常规放疗面颈联合野照射时肿瘤靶区及颅底剂量欠量问题,并分析采用不同处方剂量点造成的靶区剂量分布差别。方法选择11例接受常规放疗的首程鼻咽癌患者,普通模拟机定位,将通过科查房的面颈野边界应用细铅丝在面罩上标记,然后在CT模拟机上采取和普通模拟机定位相同的治疗体位及固定方式进行扫描,获取的图像通过网络系统传输至治疗计划系统。由医生在数字重建图像上根据细铅丝的位置复制出面颈联合野,同时在横断面上逐层勾画鼻咽原发肿瘤GTV及照射野内的蝶骨体、斜坡等靶区。取两个处方剂量点分别位于第1颈椎前(代表鼻咽深度)和第3颈椎前(代表上颈深度)。按临床要求以处方剂量点36Gy分18次为面颈联合野的处方剂量,由计划系统分别计算原发肿瘤及颅底的剂量。结果以鼻咽深度为处方剂量点时,95%体积的GTV实际受量为33.31~35.54Gy,中位值为34.83Gy;95%体积的颅底实际受量为17.76—34.60Gy,中位值为30.28Gy。当以上颈深度为处方剂量点时,95%体积的GTV实际受量为31.43—33.36Gy,中位值为32.44Gy;95%体积的颅底实际受量为16.52~32.60Gy,中位值为28.52Gy。结论鼻咽癌常规放疗采用面颈联合野无论采用鼻咽还是上颈部为处方剂量计算深度均会造成GTV及颅底剂量低于处方剂量,后者尤为明显。提示临床实施常规放疗时应以鼻咽深度为处方剂量点,同时应结合临床情况酌情考虑对颅底受侵患者疗终给予适当补量。Objective To evaluate the dose distribution of the target volume and the cranial base in nasopharyngeal carcinoma (NPC) treated with facial-cervical fields, and to analyze the differences of dose distribution using different isocenters with the CT-simulator and treatment planning system (TPS). Methods Eleven patients with nasopharyngeal carcinoma were treated by conventional radiotherapy as their primary treatment. All patients were simulated by the conventional simulator and the field borders were marked with thin lead wires on the mask. Then the patients were scanned by the CT-sim with the same immobilization. The planning CT images were transferred to the TPS and the field borders were copied on the DRR, and then GTV and the cranial base were contoured on the coronal CT slices. Two isocenters were chosen, including one in front of the 1 st cervical vertebra to measeure the depth of the nasopharynx and the other in front of the 3rd cervical vertebra to measure the depth of the upper neck. The prescription dose of 36 Gy was given in 18 fractions. Dose distributions of GTV and the cranial base were calculated with TPS. Results The actual dose of 95% volume of GTV was 33.31 - 35.54 Gy ( median 34.83 Gy) and 31.43 - 33.36 Gy ( median 32.44 Gy) when the isocenters were set in the nasopharynx and the superior neck, respectively. The corre- sponding actual dose of 95% volume of the cranial base was 17.76 - 34.60 Gy ( median 30.28 Gy ) and 16.52 - 32.60 Gy ( median 28.52 Gy), respectively. Conclusions For NPC patients treated with conven- tional radiotherapy using facial-cervical fields, the actual dose of GTV and the cranial base is lower than the prescribed dose whenever the isocenter is set in the nasopharynx or the upper neck,which is more significant in the latter. The isoeenter should be set in the nasopharynx when the conventional radiotherapy is applied and a boost of 4 -8 Gy should be given when the cranial base is involved.

关 键 词:鼻咽肿瘤/放射疗法 放射疗法 常规 面颈联合野 剂量学 

分 类 号:R686[医药卫生—骨科学]

 

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