摆位误差对患者剂量学的影响  

Influence to dosimetry of patient by set-up errors

作　　者：胡杰[1] 董晓庆 林清[1] 张莹[1] 张佳斐 张颖[1] 

机构地区：[1]上海市第十人民医院放疗科,上海200072

出　　处：《医疗卫生装备》2017年第7期89-92,共4页Chinese Medical Equipment Journal

摘　　要：目的 :研究摆位误差对直肠癌调强放射治疗计划剂量学的影响。方法 :对1例直肠癌术后患者设计多野静态调强放射治疗计划。计划确认执行后,共设计9个新计划:将等中心点仅向患者头、脚、背、腹、左、右方向分别平移5mm;将等中心点同时向患者头、背、左移动5 mm;将等中心点同时向患者脚、腹、右移动5 mm;按开始放疗前5次锥形束CT(cone beam CT,CBCT)扫描配准情况,选择最大误差移动等中心。模拟以上不同的等中心摆位误差,并将其与原计划进行比较,观察靶区及主要危及器官股骨头、膀胱、小肠的剂量变化。结果:以等中心同时向3个方向移动5 mm计划的计划靶区(planning target volume,PTV)和正常器官剂量影响最大;各个计划对临床靶区(clinical target volume,CTV)剂量影响不大;各个计划正常器官的高剂量D2(2%靶区体积所受照射剂量)和平均剂量对小肠、膀胱影响不大,但对股骨头影响很大。结论:摆位误差对靶区PTV剂量有较大的影响,尤其是靶区低剂量D_(98)(98%靶区体积所受照射剂量)明显降低,可能影响治疗效果。对一些摆位误差较大的患者,应增加CBCT扫描次数并予以在线实时修正,以保证放射治疗计划的精准实施。Objective To investigate the influence to dosimetry of the patient with rectum cancer by setup errors. Methods First an intensity modulated radiation treatment planning for a rectum cancer patient was designed, then the isocenter was moved 5 mm respectively to the left side, right side, abdomen side, back side, head side and foot side; and the isocenter was moved 5 mm to head side, back side and left side at the same time; and the isocenter was moved 5 mm to foot side, abdomen side and right side at the same time; and the isocenter was moved according to the largest set-up error for the first five Cone Beam CT scanning, thus nine new plans and a confirmed plan were got, the influence to dosimetry for targets and fermur head, bladder and intestine for these ten plans was analyzed. Results The influence to the dosimetry gained the maximum value in the planning target volume（PTV） with the isocenter moving 5 mm to three directions and normal organs. All the plans had little influence on clinical target volume（CTV）, which posed few effects on small intestine and bladder while big influence to femoral head in case of high dose D_2 to 2% target volume and mean dose. Conclusion The set-up error may influence dosimetry of PTV, and the reduction of low dose D_（98） to 98% target volume may affect treatment effect. For patients whose set-up errors are large, times of cone beam CT scanning have to be increased in order to ensure the precise implementation of the treatment plans.

关 键 词：直肠癌 摆位误差 剂量学 剂量分布 调强放射治疗 治疗计划系统 

分 类 号：R730.55[医药卫生—肿瘤]