【摘要】 目的通过对138例鼻咽癌病人调强放疗计划的剂量体积直方图肯关参数的研究分析,评价其靶区剂量的满意度及适形度指数和均匀性,正常组织的耐受量,并讨论如何避免小误差。方法先正向设计,对靶区确定射野数量、能量、射野方向和机架角度,并根据不同靶区的总剂量分别给出各进程的分次剂量,根据这些临床参数,设计者参与计划系统的逆向优化,并依据 DVH 的有关参数决定计划的采用与否。结果 96%以上的入选对象靶体积均能满足目标剂量要求,即100%的靶体积都能达到大于95%且小于107%的处方剂量。正常组织中,腮腺受量相比目标剂量有较大误差,56%的病人平均剂量在30～40GY 左右。垂体受量有45%的病人超出目标耐受量。晶体有16%的病人平均剂量在4～10GY 左右。其他正常组织受量相比目际耐受剂量均低10%～20%。剂量验证结果有10%的验证对象剂量有5%～10%的误差需要调整。电子射野影像系统(EPID)摆位验证结果误差在±1～3mm 左右。在计划实施时非共面角度不合适重设计划占1%。治疗时需移动治疗床的横杠和竖杠的计划占20%。结论用调强方法治疗鼻咽癌,能获得肿瘤靶区的高剂量和正常组织较低的剂量,因此要想再增加靶区的处方剂量是完全可行的。腮腺误差较大,和设计者的重视程度相关。头部非共面设野可使晶体满足目标耐受量。更多还原

【Abstract】 Objective To evaluate accurate radiation doses,conformity index(CI),homogeneity,dose to organs at risk,and minimize the deviation of plan by using dose-volume histogram(DVH)in cases 138 often encountered in the design of intensity modulated radiation therapy (IMRT)plan.Methods The amount,energy and direction of beams,and gantry angles are prearranged.The prescription dose of target volume are calculated by course,and optimized by plan system.Whether the plan would be employed is determined by the dose distribution of target vol- ume.Results Ninety-six percent of dose distribution of target volume meet the requirement of no deviation,i.e.,100% of volume meet the prescription dose between 95% and 107%.Among normal tissues,parotid is difficult to get the protocol aims tolerance dose-only 44% of pa- tients meet criteria and average aims tolerane dose of 56% subjects were 30～40GY.Larger deviation in 45% of pituitary is due to skull base in- vasion and encompasses by target.Average doses of lens were 4～10GY in 16% of subjects.Five to ten percent of deviation in 10% of dose veri- fication subjects require to be modulated.Average deviation of Electronic Portal Imaging Device(EPID)were 1～3mm in position verifica- tion.One percent of plans in noncoplanar require to be reset up.Twenty percent of plans require to be moved eouch lateral.The doses in other nor- mal tissues were 10～20% lower than aims tolerance dose.Conclusion Each step of plan should be cautious to avoid deviation.The protocol aims dose is hard to get in parotid glands perhaps due to lack of attention by designer.Noncoplanar may make lens get the protocol aims dose.It is practical to increase the prescription doses of target volume by obtaining the higher doses in tumor and lower doses in normal tissue with IMRT.更多还原