鼻咽癌调强放疗中治疗摆位床高临床意义的研究

Research on the treatment couch-height on the positioning for nasopharyngeal carcinoma in intensity modulated radiation therapy

目的:探讨治疗床高读数在鼻咽癌调强放射治疗摆位过程中是否有参考价值,分析其是否有助于提高摆位的精确性。方法:随机选取20例在我院实施调强放射治疗的鼻咽癌患者。每次治疗时以"十"字标记线为标准摆位,并记录治疗床高的读数和零位源皮距的读数。每周分别以"十"字标记线为标准摆位(A组)和以治疗验证时零位源皮距为标准摆位(B组)用电子射野影像装置(EPID)拍摄正侧位验证片,共获得480张,所获得的图像与计划系统的数字重建射线影像(DRR)通过MOSAIQ系统进行骨性标志并计算摆位误差。结果:A和B组的图像误差在左右、头脚和前后方向分别为(1.58±0.70)、(2.26±1.20)和(1.19±0.75)mm以及(1.50±0.81)、(2.39±1.12)和(2.56±1.06)mm。A和B组在左右(t=0.56)、头脚(t=0.41)方向差异无统计学意义(P>0.05),但在前后方向的摆位误差差异有统计学意义,t=6.52,P<0.05。结论:在鼻咽癌调强治疗摆位时,治疗床高读数有重要的参考价值,有助于提高摆位的精确性。

OBJECTIVE： To study the value of the treatment couch height data in intensity modulated radiation therapy （IMRT） for nasopharyngeal carcinoma （NPC） and analyze whether the couch height helps to improve the positioning accuracy. METHODS： Twenty randomly-selected NPC patients received IMRT in Sun Yat- sen University Cancer Center. Technicians set up with the ＂＋＂ signs and recorded the couch-height and the source surface distance （SSD） in every treatment. As the standard by the ＂＋＂ signs （Group A） and by the SSD of the first treatment （Group B） took electronic portal images （EPIs） every week, total 480 anterior and lateral EPIs. The EPIs were compared with the digitally reconstructed radiographs （DRRs） which were from the treatment planning system （TPS） by the bone signs in the MOSAIQ system. The sys tern would calculate the setup errors. RESULTS： The setup errors were：（1. 58±0. 70） mm in left-right direction, （2.26±1.20） mm in cranial-caudal direction, （1.19±0.75） mm in anterioFposterior direction for the GroupA;（1. 50±0. 81） mm,（2. 39± 1. 12） mm,（2. 56±1.06） mm for the Group B. The t-test was：（t=0.56,P〉0.05） in leftright direction, （t= 0. 41, P2〉 0. 05） in cranial caudal direction. Both were pointless in statistics. In anterior-posterior direction （t= 6.52,P〈 0.05） the data was valuable in statistics. CONCLUSION： When the technicians setup the IMRT patient of NPC, the data of the couch-height should be referred to improve the positioning accuracy.