快速旋转调强与固定射野动态调强在直肠癌术前放疗中的剂量学比较

目的 比较快速旋转调强(RapidArc)与固定射野动态调强(dIMRT)两种放射治疗技术在直肠癌术前放疗中的剂量学差异.方法 采用两种治疗技术对10例Ⅱ、Ⅲ期直肠癌术前患者设计同步加量治疗计划.处方剂量为GTV 50.6 Gy,分22次;PTV41.8 Gy,分22次,危及器官限量参考临床常规要求.在95%体积的PTV达到处方剂量前提下,比较两种计划的剂量体积直方(DVH)图、靶区和危及器官剂量、靶区剂量适形度、剂量分布均匀性、机器跳数以及治疗时间.结果 RapidArc计划中,GTV和PTV的靶区剂量适形度较高(t=7.643、8.226,P＜0.05);而靶区剂量均匀性略低于dIMRT(t=-10.065、-4.235,P＜0.05).RapidArc计划中大、小肠的平均受量显著低于dIMRT计划(t=2.781,P＜0.05).膀胱平均受照剂量略低于dIMRT,股骨头的平均受量略高于dIMRT,但差异无统计学意义.RapidArc计划机器跳数减少48.5%,平均治疗时间节省79.5%.结论 RapidArc与dIMRT计划在直肠癌术前放射治疗的剂量学上无明显差异.RapidArc每次治疗时间明显缩短,减少了治疗期间患者非主观运动引起的误差,总的机器跳数降低,减少了正常组织照射.

Abstract：

Objective To compare the dosimetric difference between RapidArc and fixed gantry angle dynamic intensity modulated radiotherapy (dIMRT) in developing the pre-operative radiotherapy for rectal cancer patients.Methods Two techniques,RapidArc and dIMRT,were used respectively to develop the synchronous intensity modulated plans for 10 stage Ⅱ and Ⅲ rectal cancer patients at the dose of gross tumor volume (GTV) of 50.6 Gy divided into 22 fractions and planning target volume (PTV) of 41.8 Gy divided into 22 fractions.Both plans satisfied the condition of 95% of PTV covered by 41.8 Gy.The dose-volume histogram data,isodose distribution,monitor units,and treatment time were compared.Results The two kinds of dose volume histogram (DVH) developed by these two techniques were almost the same.The conformal indexes of GTV and PTV by RapidArc were better than those by dIMRT (t =7.643,8.226 ,P < 0.05),while the homogeneity of target volume by dIMRT was better (t =-10.065,-4.235 ,P <0.05).The dose of rectum and small bowel planned by RapidArc was significantly lower than that by dIMRT (t =2.781 ,P <0.05).There were no significant differences in the mean doses of bladder and femoral head between these two techniques.The mean monitor units of RapidArc was 475.5,fewer by 48.5% in comparison with that by the dIMRT (924.6).The treatment mean time by RapidArc was 1.2min,shorter by 79.5% in comparison with that by dIMRT (5.58 min).Conclusions There is no significant dosimetric difference between the two plans of RapidArc and dIMRT.Compared with dIMRT,RapidArc achieves equal target coverage and organs at risk(OAR) sparing while using fewer monitor units and less time during radiotherapy for patient with rectal cancer.

Dosimetric comparison of volumetric modulated Arc therapy with conventional intensity-modulated radiotherapy for preoperative radiotherapy of rectal cancer

Objective To compare the dosimetric difference between RapidArc and fixed gantry angle dynamic intensity modulated radiotherapy (dIMRT) in developing the pre-operative radiotherapy for rectal cancer patients.Methods Two techniques,RapidArc and dIMRT,were used respectively to develop the synchronous intensity modulated plans for 10 stage Ⅱ and Ⅲ rectal cancer patients at the dose of gross tumor volume (GTV) of 50.6 Gy divided into 22 fractions and planning target volume (PTV) of 41.8 Gy divided into 22 fractions.Both plans satisfied the condition of 95% of PTV covered by 41.8 Gy.The dose-volume histogram data,isodose distribution,monitor units,and treatment time were compared.Results The two kinds of dose volume histogram (DVH) developed by these two techniques were almost the same.The conformal indexes of GTV and PTV by RapidArc were better than those by dIMRT (t =7.643,8.226 ,P < 0.05),while the homogeneity of target volume by dIMRT was better (t =-10.065,-4.235 ,P <0.05).The dose of rectum and small bowel planned by RapidArc was significantly lower than that by dIMRT (t =2.781 ,P <0.05).There were no significant differences in the mean doses of bladder and femoral head between these two techniques.The mean monitor units of RapidArc was 475.5,fewer by 48.5% in comparison with that by the dIMRT (924.6).The treatment mean time by RapidArc was 1.2min,shorter by 79.5% in comparison with that by dIMRT (5.58 min).Conclusions There is no significant dosimetric difference between the two plans of RapidArc and dIMRT.Compared with dIMRT,RapidArc achieves equal target coverage and organs at risk(OAR) sparing while using fewer monitor units and less time during radiotherapy for patient with rectal cancer.