直肠癌术前三维适形和五野及容积弧形调强放疗剂量学比较

目的：比较三维适形放射治疗（3-dimensionconformalradiotherapy，3D-CRT）和五野调强放射治疗（5-fieldin—tensitymodulatedradiotherapy，5F—IMRT）以及容积弧形调强放射治疗（volumetricmodulatedarctherapy，VMAT）计划的剂量学特点，探讨直肠癌术前适形放疗理想的计划模式。方法：收集中山大学肿瘤防治中心2012—01—17—2012—07—23收治的12例接受术前新辅助放化疗的直肠癌患者，对12例患者统一规定直肠癌术后辅助性放疗的·临床肿瘤体积（clini—caltargetvolume，CTV）范围，设定计划靶体积（planningtargetvolume，PTV）为CTV外放：头脚方向0．9cm，侧方0．8cm，前后方0．7cm。分别进行3D-CRT、5F-IMRT及VMAT计划设计，比较3者靶区剂量分布特点以及小肠、膀胱和双侧股骨头的受照射剂量及体积。结果：3D-CRT计划PTV2的适形指数（conformityindex，CI）为0．623±0．074，5F-IMRT计划为0．699±0．059，VMAT计划为0．710±0．060，5F—IMRT及VMAT计划PTV2剂量分布的适形性优于3D-CRT计划，F=6．103，P=0．006；3D-CRT计划PTVl的均匀性指数（homogeneityindex，HI）为1．063_4-0．012，5F—IMRT计划为1．046±0．011，VMAT计划为1．047±0．010，5F-IMRT及VMAT计划PTVl剂量的均匀性亦优于3D-CRT计划，F=5．980，P=0．006。VMAT中小肠接受剂量〉35Gy照射体积（V35）为（8．61±6．43）％，优于3D-CRT的（11．94±9．22）％及5F-IMRT的（10．43±6．81）％，F=0．602，P=0．008；VMAT中小肠接受剂量〉40Gy照射体积（V40）为（5．63±4．68）％，优于3D-CRT的（7．64±6．18）％及5F-IMRT的（6．65±5．42）％，F=0．437，P=0．049；VMAT中小肠接受剂量〉45Gy照射体积（V45）为（2．79±2．69）％，优于3D-CRT的（5．09±4．50）％及5F-IMRT的（3．40±3．36）％，F=1．127，P=0．036。3D-CRT膀胱5％体积所受最低剂量（D5）、接受剂量〉30Gy照射的体积（V30）均小于5F-IMRT及VMAT，F值分?

Volumetric modulated arc therapy vs. 5F intensity modulated radiotherapy and 3D conformal radi6therapy in preoperative rectal cancer.dosimetric comparison

OBJECTIVE： To investigate the better mode of radiotherapy through comparing the dosimetry of Volu- metric modulated arc therapy （VMAT） vs. 5F intensity modulated radiotherapy （IMRT） and 3D eonformal radiotherapy （3D-CRT） in the patients of rectal cancer with preoperative radiation. METHODS： Twelve patients with rectal cancerreceived neoadjuvant chemoradiotherapy between January 17th and July 23rd,2012 at Sun Yat-sen University Cancer Center were enrolled. 3D-CRT, 5F-IMRT and VMAT plan were designed to these patients with preoperative radiotherapy. With definition of clinical target volume （CTV） identical in all three techniques, the planning target volume （PTV） was defined as PTV= CTV ＋0.9 cm at head and feet direction,0.8 cm at around,0.7 cm at front and rear. The conformity index （CI） and homogeneity index （Hi） in target volume,and the dose and volume radiated of the organs at risk （OAR）, such as small bowel, bladder and bilateral femoral were compared in three plans. RESULTS： The CI for PTV2 of 5F-IMRT and VMRT were superior to 3D-CRT,F= 6. 103,P= 0. 006 ;The HI for PTV1 of 5F-IMRT and VMRT were superior to 3D-CRT,F=5. 980,P=0. 006;CI for the PTV2 was 0. 623±0. 074 （3D-CRT） ,0. 699±0. 059 （SF-IMRT） ,and 0. 710±0. 060 （VMAT）. HI for PTV1 was 1. 063±0. 012 （3D-CRT） ,1. 046±0. 011 （5F-IMRT） ,and 1. 047±0. 010 （VMAT）. The volume accepted more than 35 Gy （V35） of small bowel in VMAT was （8.61±6.43）%, and less than that in 3D-CRT（11.94 4- 9.22） M and 5F-IMRT（10.43 ± 6.81） %, F = 0. 602, P = 0. 008 ; The volume accepted more than 40 Gy （V40） of small bowel in VMAT was （5.63±4.68）%, and less than that in 3D-CRT （7.64 ± 6.18）% and 5F-IMRT （6.65±5.42） % ,F = 0.437, P = 0. 049; The volume accepted more than 45 Gy （V45） of small bowel in VMAT was （2.79±2.69） % ,and less than that in 3D-CRT（5. 09±4. 50） % and 5F-IMRT（3. 40±3. 36） % ,F= 1. 127 ,P=0. 036. The lowest dose of 5 % volume （D5） and vol