全腹腔常规放射治疗技术的剂量学三维评价

Research on the dosage of technique of whole abdomen radiotherapy

目的:通过在三维治疗计划系统中模拟常规全腹照射来观察靶区和正常组织的剂量学分布,寻求较佳的常规放疗方法。方法:在三维治疗计划系统中模拟常规全腹照射,全腹放疗野分上腹野和盆腔野,两野间衔接方法分为常规和转床转臂架,上腹侧野后界分为椎体前1/4和PTV后缘,采用6MV高能X射线模拟照射,全腹照射总剂量30Gy/20次。结果:上腹野和盆腔野常规野间衔接处最大、最小剂量分别为36.2、26.9Gy,转床转臂架后野间衔接处最大、最小剂量分别为34.1、28.3Gy。衔接点每周移动1次,衔接处剂量分布更均匀。射野后界在椎体前1/4时95%等剂量曲线包括的PTV体积仅有82.3%,大部分脾脏在射野外,射野后界在PTV后缘时95%等剂量曲线包括的PTV体积为98.4%。射野后界应根据病变的侵犯范围而定,可以挡铅保护肾脏,漏照部分可用小野补量照射。结论:全腹放疗时,野间衔接可通过常规衔接和转床转臂架衔接实现,射野后界应个体化。

OBJECTIVE： To simulate conventional radiation technique to calculating the distribution of targets-dosages or normal-organs received doses by three-dimensional radiation planning, and explore better common whole abdomen radiotherapy. METHODS： Epigastric field and pelvis field consisted of all the fields of whole abdomen radiotherapy. The conjunctional way between the two kinds of the fields was as following： one was implemented by conventional radiation technique, the other by rotation the couch or the gantry. A quarter posterior pyramid or posterior border of PTV was post-margln of the epigastric lateral field with 6 MV X ray, and the total dose was 30 Gy with 20 fractions. RESULTS.. The maximum or minimum dose was 36.2 or 26.9 Gy in middle of epigastric field and pelvis field by conventional technique, and the dose was changed to 34. 1 or 28. 3 Gy after the rotation of the couch or gantry. The dose uniformity was better with one or more change of the linked field-border. When the post-margin of epigastric field was located at 1/4 vertebral body, 82.3% volume of PTV was comprised in 95% isodosecurve, the most of the spleen out of the field; if the field post-margin was moved to the fringle of PTV, 95% isodose-curve included 98.4% volume of PTV. The posterior borders of fields were determined according to the tissue matching and infiltrating extent of tumor. The kidney was protected by lead brick, and the small field was used to redeem the insufficient-dose target. CONCLUSIONS： Epigastric field and pelvis field are linked by conventional technique and by rotation the couch or the gantry. The post-margin is determined with individualization in the epigastric field.