【作者】 吴丹玲；

【导师】 王石； 陈甲信；

【作者基本信息】 清华大学 ， 生物医学工程， 2010， 硕士

【摘要】 研究宫颈癌调强放射治疗计划的最佳参数。利用图像引导设备测量宫颈癌放射治疗的摆位误差。研究治疗过程中的反馈信息对计划剂量分布的影响,讨论自适应放射治疗的必要性和可行性。16例术后宫颈癌,以95%PTV体积获得5000cGy处方剂量进行归一,进行不同参数的IMRT计划设计,讨论其对计划质量的影响。不同野数的计划中,7野计划在靶区、危及器官参数及治疗时间等方面的综合优势优于5野及9野计划;5野计划中,同心圆结构的设置改善靶区适形度,减少照射体积,非均匀布野减少照射体积的同时增加了小肠低剂量的照射体积;优化强度级数为8的计划质量最接近原计划,且子野数减少19.32%。使用加速器自带的千伏级锥形束断层扫描系统扫描16例宫颈癌患者共305次,对患者左右(X)方向、头脚(Y)方向和前后(Z)方向的误差进行测量和统计。将结果应用到原始计划(PLAN1),通过改变射野中心模拟实际治疗,而射野角度、形状、权重、MU数等条件不变,重新计算,得到新计划(PLAN2及PLAN3)。将原计划中的PTV分别回缩成CTVx10-CTVx3,找出满足处方剂量条件的CTVx,则CTVx和PTV之间的距离即CTVx到PTV的外扩是足够的。再从所找到的外扩中取最小值,即为PTV回缩法得出CTV外扩范围。(1)16例患者在X、Y、Z方向的系统误差和随机误差分别为(1.13±2.94) mm、(-1.63±7.13)mm、(-0.65±2.25)mm。(2)根据公式2.5∑_总+0.7σ_总计算X、Y、Z三个方向上CTV到PTV的外放应分别为5、9、3mm。(3)摆位误差不明显增加直肠、小肠、股骨头的受量,但影响膀胱的受量。(4)剂量回归结果显示, CTVx10- CTVx7均满足临床99%的CTV接受95%处方剂量的要求,为更好地保护正常组织,在CTVx10- CTVx7中,选择保证靶区剂量的最小外放即7mm。(5)根据公式计算和剂量回归两种方法得到从CTV到PTV的外放差异比较大,相对而言,根据剂量回归结果所得出的外放值更能反应具体医院患者实际情况,故选择均匀7mm为我院从CTV到PTV的外放值。更多还原

【Abstract】 The article is to investigate optimized IMRT plan of cervical cancer;to measure setup errors for patient of cervical cancer in radiotherapy. It was investigated the feedback in treatment effects and the dose distribution for IMRT plan.And to discuss the feasibility of adaptive radiation therapy.Sixteen patients with postoperative cervical cancer were investigated. All the plans were normalized so that 95% of planning target volume (PTV) at least received 50 Gy. Different IMRT plans were generated for each patient and the parameters of plans were discussed for the quality of plans. A seven-field technique was best for dose of PTV and protection of organ at risks (OARs), moreover reduced treatment time than a five-field technique and a nine-field technique.Concentric ring technique improved comfortable of PTV and reduced irradiation volume.And no uniform set up of beams technique reduced irradiation volume but to increases the volume of low dose for intestine.The quality of the plan for the intension level 8 was to get close the intension level 10,and to further reduced the number of segments by 19.32%.The 16 patients of cervical cancer were received a total of 305 kilo-volt cone-beam computed tomography (kv-CBCT) scans, which evaluated the setup errors in left-to-right (X), in superior-to-inferir (Y) and in anterior-to-posterior (Z) .The isocenter of the initial plan (PLAN1) was changed according to the setup errors to simulate radiotherapy and then recalculated the dose distribution without changing the direction, shape and weight of fields,we would had the new plans (PLAN2 and PLAN3) .Then retracted the PTV from the original plan to get CTVx10, CTVx9, CTVx8, CTVx7, CTVx6, CTVx5, CTVx4, CTVx3, selected CTVx that agree with prescription dose , confirm the distance between CTVx and PTV, the minimum value was the margin from CTV to PTV. (1)The setup errors of 16 patients in X, Y and Z directions were(1.13±2.94) mm (,-1.63±7.13) mm(,-0.65±2.25) mm.(2) The distance between CTVx and PTV was 5,9 and 3mm in X, Y and Z directions According to 2.5∑+0.7σ.(3)Setup errors was not to increase obviously dose of rectum, intestine and femoral head, but bladder.(4) Transplantation plans displayed 99% of CTVx10- CTVx7 and received 95% of prescription dose, departed from standard of clinic.In order to protect normal tissues,we selected 7mm that was the minimum value of the margin from CTV to PTV.(5) The margin from CTV to PTV, that be to calculated by formula and Transplantation plans was difference.In fact, the margin from the result of transplantating plans would be confidence,because it represented practice of treatment.So that we selected the margin of 7mm for CTV to PTV.更多还原