基于轮廓优化技术在鼻咽癌调强放疗计划设计中的应用

The application of contour-based optimization technique in the intensity-modulated radiation therapy for nasopharyngeal carcinoma

目的:研究鼻咽癌根治性放疗采用正向调强计划的方法和规律。方法:总结2005年3月～2010年8月共92例鼻咽癌患者行根治性调强放疗的计划设计方案,均采用基于轮廓优化技术,根据靶体积和危及器官预设不同射束的主野形状,手工补野,正向优化设计完成调强计划。结果:剂量分布及剂量体积直方图满足临床要求,PGTVnx(92/92)的D95≥70 Gy,PTV1(85/92)的D95≥60 Gy,PTV2(82/92)的D95≥54 Gy,脊髓最大剂量≤45 Gy(90/92);子野数29～65,平均值39,中位数41;总跳数586.9～1 050.7,平均值720.5,中位数758.6;2006年10月之后的65例患者单次治疗时间为11.6～23.5 min,平均值15.7 min,中位数16.5 min。结论:调强放疗技术给鼻咽癌的放疗带来了全新的解决方案和理念,基于轮廓正向优化技术运用得当可以得到与逆向优化相当的剂量分布,并且有效地降低了总跳数和治疗时间,提高了治疗效率。

Objective：To study the application of forward optimization technique in the intensity-modulated radiation therapy for nasopharyngeal carcinoma.Methods：From March 2003 to August 2010,92 patients with nasopharyngeal carcinoma underwent in-tensity-modulated radiation therapy and were considered in this retrospective study.All treatment plans were designed according to contour-based optimization technique based on the patient’s anatomy,i.e.,on the outlined structures like planning target volume and organs at risk,or the apertures can be defined according to certain isodose-lines achieved with an open field.Results：The dose dis-tributions and dose-volume histograms met the demand of treatment in all patients.The doses of 95 percent（D95）of planning gross tumor volume of nasopharyn（PGTVnx）were greater than or equal to 70 Gy for all patients（92 /92）.The D95s of planning target vol-ume of high risk region（PTV1）were greater than or equal to 60 Gy for 85 patients（85 /92）,and the D95s of planning target volume of low risk region（PTV2）were greater than or equal to 54 Gy for 82 patients（82 /92）.The maximum doses of cord were 45 Gy for all patients（92 /92）.The mean number of segments was 39（range,29～65）and the median was 41.The mean total monitor units（MU）were 720.5（range,586.9～1 050.7）and the median was 758.6.The mean treatment time was 15.7 min（range,11.6～23.5 min）and the median was 16.5 min for 65 patients underwent after October 2006.Conclusion：This study suggests that intensity-mod-ulated radiation therapy appears to be a new effective option for nasopharyngeal carcinoma.The satisfactory dose distributions can be obtained using reasonable contour-based optimization technique.The superiorities of contour-based optimization such as deep de-creased segments can reduce total MU and shorten treatment,get more efficient treatment outcomes.