前列腺调强放射治疗中摆位对正常组织剂量的影响  

Dosimetric effect of setup on normal tissue with IMRT for prostate cancer

作　　者：余增荣[1] 

机构地区：[1]广东省江门市中心医院肿瘤科,广东江门529030

出　　处：《中国医学工程》2005年第1期49-51,58,共4页China Medical Engineering

摘　　要：目的量化利用计划危及器官区(PORV)对股骨头的剂量影响,同时评估虽因临床上小的摆位误差但运用计划危及器官区(PORV)却能约束正常组织的剂量。方法首先给十位前列腺癌患者用五野调强计划进行优化,然后用外扩股骨头5mm的计划危及器官区再优化。模拟治疗最差的情况下,将治疗等中心上下、左右、前后六个方面移动5mm以模拟系统摆位的不确定性,对每一计划不进行优化,剂量分布重新计算,每个病人产生六个不用计划危及器官区(PORV)的计划和六个用计划危及器官区(PORV)的计划。结果增加了计划危及器官区(PORV)及进行再优化并没有很大程度影响PTV、直肠、膀胱及股骨头的受照射剂量,相反,没移动等中心位置,用计划危及器官区(PORV)可限制股骨头的剂量升高,同时减少股骨头毗邻区域的面积。模拟移动等中心位置,对侧股骨头的剂量会因向对侧移动中心位置而提高很多,如右股骨头用计划危及器官区(PORV)其超过50Gy的剂量会从8.07%减少到5.95%。结论运用计划危及器官区(PORV)可以限制正常组织结构的体积及受照射量,如右股骨头,从而减少因摆位误差而造成剂量的改变。Objective The purpose of this study is to quantify the dosimet ric effect of employing PORV for the femur head and to evaluate the use of PORV on normal-tissue sparing in the setting of small clinical setup errors. Method s The first optimized plan was five-beam IMRT plan for ten prostate cancer pat ients. A second optimized plan was generated for each patient by adding a PORV o f 5 mm for the femur head. Systematic translational setup uncertainties were sim ulated by shifting the treatment isocenter 5 mm superiorly, inferiorly, left, ri ght, anteriorly, and posteriorly, without altering optimized beam profiles. At e ach shifted isocenter, dose distributions were recalculated, producing a total o f six shifted plans without PORV and six shifted plans with PORV for each patien t. Results The addition of the PORV and reoptimization did not significantly affect the dose to planning tumor, rectum, bladder, left femur head and right f emur head, in contrast, without any shift, the PORV did increase femur head spar ing and reduce coverage of the nodal region adjacent to the femur head. When the plans were shifted, the greatest contralateral femur head gland. With these shi fts, the average volume of contralateral femur head receiving greater then 50 Gy was reduced from 8.07% to 5.95% when PORV was used. Conclusion The use of P ORV may limit the volume of normal tissue structures, such as the right femur he ad, exceeding tolerance dose as a result of setup errors.

关 键 词：股骨头 剂量 正常组织 治疗 前列腺 摆位 器官 区域 限制 模拟系统 

分 类 号：R681[医药卫生—骨科学] R730[医药卫生—外科学]