鼻咽癌调强放射治疗的剂量学特点

Dosimetric Characteristic of Intensity Modulated Radiotherapy(IMRT) in Nasopharyngeal Carcinoma

[目的]分析鼻咽癌调强放疗各个靶区和周围正常器官的剂量学特点。[方法]2004年7月至10月入院的10例初治鼻咽癌调强放疗病人,用前7野方案,每野的照射范围从颅底到锁骨上淋巴预防区。剂量处方是:GTV1为2.18Gy/次,32次,GTV2为2.03Gy/次,32次,CTV1为1.88Gy/次,32次,CTV2为1.80Gy/次,28次。研究GTV的最大、最小和平均剂量,CTV的最小剂量,脊髓、脑干和晶状体的最大剂量,腮腺的50%体积受照剂量。[结果]10例病人GTV1的最大、最小和平均剂量(均值)分别是72.01Gy、68.65Gy、70.48Gy,GTV2的最大、最小和平均剂量(均值)分别是68.66y、65.50Gy、66.98Gy,CTV1的最小剂量为60.10Gy,CTV2的最小剂量为51.18Gy,脊髓、脑干和晶体状的最大剂量分别为44.7Gy、51.7Gy和6.8Gy,高剂量侧和低剂量侧,腮腺的50%体积的受照剂量分别为44.39Gy和39.36Gy。[结论]调强放疗可以使各个靶区得到足够的、均匀的剂量分布,周围的正常组织受到比较好的保护,腮腺50%体积受照剂量控制在40Gy～45Gy,显示已有较好的保护作用。

[Purpose] To investigate the dosimetric characteristic on target and surrounding organs in intensity modulated radiotherapy （IMRT） for nasopharyngeal carcinoma （NPC）. [Methods] From June to October 2004,10 primary NPC cases were treated with IMRT using anterior 7 fields. The area of each field was from skull base to supraclavicular lymph node area. The prescribed dose was 2.18Gy in 32 fractions（f） for gross tumor volumel （GTV1）; 2.03Gy in 32f for GTV2; 1.88Gy in 32f for clinical tumor volume 1 （CTV1）;1.80Gy in 28f for CTV2. Maximum dose, minimum dose, average dose of GTV, minimum dose of CTV, and maximum dose on spinal cord, brain stem, lens, and dose delivered to 50% the parotids were examined.[Resuhs]Maxinum dose, minimum dose, average dose of GTV1 in 10 patients were 72.01Gy, 68.65Gy,70.48Gy respectively; and those of GTV2 was 68.66Gy,65.50Gy,66.98Gy respectively. Minumum dose of GTV1 ang GTV2 was 60.10Gy and 51.18Gy respectively. Maximum dose of spinal cord, brain stem and lens was 44.7Gy, 51.7Gy and 6.8Gy respectively.High or low dose to 50% of parotid gland was 44.39Gy and 39.36Gy respectively. [Conclusions] IMRT may yield enough and uniformity dose to every target volume, and toxicity to surrounding normal tissue is tolerable. A dose of 40Gy-45Gy delivered to half volum of parotid gland reveals protecting function for salivery gland.