三维适形、逆向调强和旋转调强放疗技术治疗胸段食管癌的剂量学比较

Dosimetric comparison of three-dimensional conformal radiotherapy, intensity-modulated radiotherapy and RapidArc in treatment of thoracic esophageal cancer

目的比较胸段食管癌3种放疗技术（3D—CRT、IMRT、RapidArc）的剂量学特点，并分析3种技术的优劣及应用特点。方法15例胸段食管癌患者入组，依据CT图像，勾画靶区，针对患者的同一套CT图像的相同靶区分别制定3D—CRT、5野IMRT（IMRT5）、7野IMRT（IMRT7）、9野IMRT（IMRT9）、单弧Arc（Arcl）、双弧Arc（Arc2）共6套计划。PTV处方剂量为40Gy分20次4周＋19．6Gy分14次7d。结果3D—CRT计划各项靶区剂量学参数明显差于IMRT计划及RapidArc计划（t=5．77、3．52，P〈0．05），6套计划的PTV‰（％）分别为：3D-CRT（91．55±2．90），IMRT5（96．66±1．05），IMRT7（96．87±1．23），IMRT（96．81±1．16），Arcl（94．98±1．41），Arc2（95．93±1．32）。RapidArc计划的靶区适形度（CI）最好（t=3．76，10．01，P〈0．05），IMRT计划的靶区均匀性（HI）最好（t=3．93、3．37，P〈0．05）。危及器官参数RapidArc与IMRT各计划之间差异无统计学意义。3D—CRT和RapidArc计划的机器跳数明显少于IMRT计划，差异高达75％。结论对于胸段食管癌患者，采用IMRT或RapidArc技术可以在保护正常组织的同时，涵盖临床必需的治疗靶区。3D—CRT计划对降低正常组织低剂量散射区方面优势明显。RapidArc计划靶区剂量学参数与IMRT计划比较未见明显优势。

Objective To compare the dosimetric characteristics of intensity-modulated arc therapy（ IMAT ）, fixed-gantry intensity-modulated radiotherapy （ IMRT ） and 3-dimensional conformal radiotherapy （3D-CRT） for the thoracic esophageal cancer. Methods A total of 15 patients with thoracic esophageal cancer were enrolled. 3D-CRT, 5-field IMRT（ IMRTS）, 7-field IMRT（ IMRTT）, 9-field IMRT （IMRT9） , single arc（ Arc1 ） and double arc （Arc2） RapidArc plans were generated for each patient. AU plans were prescribed 40 Gy in 20 fractions and 19.6 Gy in 14 fractions to PTV at 95% isodose line. Results RapidArc and all IMRT treatment plans in dosimetric parameters of target volumes were obviously better compared to 3-dimenfional conformal treatments（ t = 5.77,3.52 ,P 〈 0. 05）. The result of Vg of PTV for 3D-CRT, IMRTS, IMRTT, IMRTg, Arcl and Arc2 plans was 91.55±2. 90, 96. 66±1.05, 96. 87 ±1.23, 96. 81 ± 1.16, 94. 98 ±1.41 and 95.93 ± 1.32, respectively. The best conformation index in PTV was observed in the RapidArc plans（ t = 3.76,10. 01 ,P 〈 0. 05 ） , and the best homogeneity index in PTV was observed in the IMRT plans（ t = 3.93,3.37 ,P 〈 0. 05 ）. In terms of organ sparing, no statistical difference was observed between IMRT and RapidArc plans（ P 〉 0. 05 ） , while 3D-CRT provided the lowest number of Vl oGyand V5 oct for total lung. Compared with the IMRT treatment plans, the number of monitor units was lower in all 3 D-CRT and RapidArc cases with differences of 75%. Conclusions All the IMRT and RapidArc plans could offer high quality treatment for patients. 3D-CRT might show advantage in low-dose region to organs at risk. Compared with IMRT, no obvious advantage in PTV dosimetric parameters could be observed in RapidArc plans.