鼻咽癌调强放疗的剂量学研究

Dosimetric analysis of intensity modulated radiation therapy in nasopharyngeal carcinoma

目的分析鼻咽癌调强放疗(IMRT)各个靶区和周围正常组织器官的剂量学特点。方法对2005年1月至2006年6月住院的30例初治鼻咽癌患者进行IMRT,将鼻咽和颈部的靶体积勾画为鼻咽大体肿瘤体积(GTVnx)、颈部大体肿瘤体积(GTVnd)、临床靶体积1(CTV1)和临床靶体积2(CTV2),处方剂量分别为70,66,60,60Gy/30次,鼻咽和上颈部靶体积采用IMRT技术照射、下颈部靶体积采用下颈前野常规照射。研究GTV,CTV的最大、最小、平均剂量和颞叶、脑干、脊髓、视神经、晶体、眼球的最大受照剂量及腮腺、颞下颌关节的50%体积受照剂量。结果GTVnx的最大、最小、平均剂量(均值)分别为79.2,59.5,71.9Gy;GTVnd的最大、最小、平均剂量分别为77.1,63.6,72.1Gy;CTV1,CTV2的最小剂量分别为47.6,49.7Gy;颞叶、脑干、脊髓、视神经、晶体、眼球的最大受照剂量及腮腺、颞下颌关节的50%体积受照剂量63.2,48.6,44.7,59.3,6.9,25.9Gy和34.0,36.3Gy。结论IMRT可以使各个靶区得到足够的、均匀的剂量分布,周围正常组织器官得到较好的保护,但是要注意CTV的低剂量区。鼻咽癌IMRT剂量分布优于常规放疗。

Objective To analyze the dosimetric characteristic on target and surrounding organs in intensity modulated radiation therapy（IMRT） for nasopharyngeal carcinoma（NPC）, Methods From January 2005 to June 2006, 30 primary NPC cases were treated with IMRT. The prescription dose was engaged in the gross target volume（GTVnx） of nasopharyngeal to Dr 70 Gy/30F, positive neck lymph nodes （GTVnd）/to Dr 66 Gy/30F, clinical target volume 1 （CTV1） and CTV2 to 60 Gy/30F. The GTVnx, CTV1 and upper neck were irradiated by IMRT technique. The lower neck and the supra clavicular fossae were irradiated with the conventional technique using an anterior field. IMRT technique was carried out using an inverse planning system （CMS Xio4.1.1）. Treatment was delivered with the Multi-leaf Intensity Modulating Collimator through a sliceby-slice arc rotation approach. Results Maximum dose, minimum dose, average dose of GTVnx were 79.2, 59.5, 71.9 Gy respectively, and those of GTVnd was 77.1, 63.6, 72.1 Gy respectively. Minimum dose of CTV1 and CTV2 was 47.6 Gy and 49.7 Gy respectively. Maximum dose of temporal lobe, brain stem, spinal cord, optive nerve, lens and eyeball were 63.2, 48.6, 44.7, 59.3, 6.9 Gy and 25.9 Gy respectively; the mean doses received to 50 % volume of parotid gland and Temporo-mandibular joint was 34.0 Gy and 36.3 Gy respectively. Conclusions IMRT may yield enough and uniformity dose to every target volume, and toxicity to surrounding normal tissue is tolerable, more attention must be paid to low dose areas in CTV1 and CTV2. The dose distribution of IMRT patients were obviously better than that of CR patients.