Influence of Segment Number on the Planning of Intensity-modulated Radiotherapy for Postoperative Adjuvant Radiotherapy for Rectal Cancer_West China Medical Journal

Authors：

JIANG Xiaoqin ¹ , WANG Wu ² , SHEN Yali ³ , XU Feng ³ ,  BAI Sen ¹

1. Division of Physics Center, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, P.R. China; 2. Department of Oncology, the First People’s Hospital of Chengdu, Chengdu, Sichuan 610041, P. R. China; 3. Department of Abdominal Tumor, West China Hospital, Sichuan University, Chengdu, Sichuan 610041, P.R. China;

Corresponding author：

BAI Sen, Email: jiangkx@yahoo.com.cn

Keywords：

直肠癌术后; 调强放射治疗; 子野数目; 治疗计划

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【摘要】　目的　调强放射治疗（IMRT）能较好的保护危及器官并给予肿瘤足够的致死剂量，基于多叶准直器（MLC）分步照射的IMRT技术对复杂病例需要更多子野。研究对直肠癌术后放射治疗使用不同子野数目的IMRT计划进行比对，选择合理的子野数。　方法　选取2010年4-8月入院的直肠癌术后患者10例，保持射野入射角度及优化目标参数相同，仅改变MLC子野数目，设计不同IMRT对每一患者治疗计划的靶区适形指数（CI）、均匀性指数、最大剂量、最小剂量、平均剂量，危及器官关注体积的受照剂量，机器跳数及治疗时间进行分析。　结果　所有治疗计划中靶区及危及器官的剂量学评估指标无统计学意义（P gt;0.05），只有亚临床计划靶区（PTV）CI在15个子野的方案中（0.74±0.06）明显差于25个子野方案（0.82±0.03）、40个子野方案（0.81±0.06）及60个子野方案（0.84±0.03），有统计学意义（P lt;0.05）；治疗机器跳数（MU）随子野数目增多明显增大，15、20、40及60个子野方案所需MU分别为（458±56）、（559±62）、（614±74）、（622±82），有统计学意义（P lt;0.05），但40个子野方案与60个子野方案间无统计学意义。治疗时间明显随子野数增加而增大。　结论　直肠癌术后IMRT计划使用25个子野能满足临床剂量要求，同时能有效降低治疗时间，可作为临床应用参考值。
【Abstract】　Objective　 The intensity modulated radiotherapy (IMRT) can deliver tumor enough doses and protect risk organs as much as possible at the same time. The MLC-based step and shoot IMRT(sIMRT) plan needs much more segment member to meet clinical aims. In this study, several sIMRT plans using different segment number for postoperative rectal cancer were compared to find out the most reasonable segment number setting.　Methods　 Ten patients with rectal carcinoma underwent postoperative adjuvant radiotherapy for rectal cancer from April to August 2010 were selected. For each patient, the angle of field, the prescription expected and the physical parameters optimized were kept the same, while only the number of segments was changed in sIMRT plans. The dose volume histogram-based parameters [conformity index (CI) and homogeneous index (HI)]　 and other parameters concerned were compared and analyzed.　Results　 The indexes of dosimetry associated with the targets and risk organs showed no significant statistical difference among the 4 sIMRT plans with different segment numbers. The index CI of PTV in the sIMRT plan with 15 segments (CI 0.74±0.06) was less than that in the sIMRT plan with 25 segments (CI 0.82±0.03), the sIMRT plan with 40 segments plan (CI 0.81±0.06), and the sIMRT plan with 60 segments (CI 0.84±0.03) (P lt;0.05). There were significant differences in MU among the sIMRT plans with 15 segments (average MU: 458±56) , with 25 segments (average MU: 559±62 ), and with 40 segments (average MU: 614±74)or with the 60 segments (average MU: 622±82 (P lt;0.05). The more segments meant more MU and more irradiation time.　Conclusion　 The sIMRT plan for patients of rectal cancer to receive postoperative adjuvant radiotherapy may require at least 25 segments to balance the accepted dose results and efficient delivering.

Citation： JIANG Xiaoqin,WANG Wu,SHEN Yali,XU Feng,BAI Sen. Influence of Segment Number on the Planning of Intensity-modulated Radiotherapy for Postoperative Adjuvant Radiotherapy for Rectal Cancer. West China Medical Journal, 2010, 25(12): 2138-2142. doi: Copy

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10.	伍志红, 张九堂, 曾彪, 等. 鼻咽癌三种子野方案对调强放疗剂量分布的影响[J]. 医学临床研究, 2009, 26(2): 241-244.
11.	陈真云, 马悦冰, 盛修贵, 等. 32例妇科恶性肿瘤术后调强适形放射治疗分析[J]. 中华肿瘤杂志, 2007, 29(4): 3058-308.
12.	房辉, 李晔雄, 余子豪, 等. 前列腺癌三维适形和调强放疗的初步结果[J]. 中华放射肿瘤学杂志, 2006, 15(3): 197-200.
13.	袁智勇, 高黎, 徐国镇, 等. 初治鼻咽癌调强放疗的初步结果[J]. 中华放射肿瘤学杂志, 2006, 15(4): 237-243.
14.	蔡勇, 何玉香, 韩树奎, 等. 直肠癌盆腔常规放疗与三维适形放疗的剂量学研究[J]. 中华放射肿瘤学杂志, 2007, 16(3): 201-205.
15.	Urbano MTG, Henrys AJ, Adams EJ, et al. Intensity-Modulated radiotherapy in patients with locally advanced rectal cancer reduces volume of bowel treated to high dose levels[J]. Int J Radiat Oncol Biol Phys, 2006, 65(3): 907-916.
16.	耿辉, 戴建荣, 李晔雄, 等. 一种简单调强放疗技术应用的初步研究[J]. 中华放射肿瘤学杂志, 2006, 15(1): 411-415.

1. 　Greard JP, Chapet O, Nemoz C, et al. Improved sphincter preservation in low rectal cancer with high-dose preoperative radiotherapy: the lyon R96-02 randomized trial[J]. J Clin Oncol, 2004, 22(12): 2404-2409.
2. 　Glimelins B, Cronberg H, Jarhule J, et al. A systematic overview of radiation therapy effects in rectal cancer[J]. Aeta Oncol, 2003, 42(5-6): 477-492.
3. 　姚波, 郑明民, 王平, 等. 直肠癌五野调强放疗与传统适形放疗剂量学研究[J]. 临床肿瘤学杂志, 2005, 14(6): 483-486.
4. 　钱立庭, 金大伟, 刘新, 等. 直肠癌术后辅助性放疗不同照射技术的剂量学研究[J]. 中华放射肿瘤学杂志, 2006, 15(1): 411-415.
5. 　姚波, 郑明民, 张艳, 等. 低位直肠术前调强同步加量并同步口服卡培他滨化疗的初步研究[J]. 癌症进展杂志, 2009, 7(4): 442-447.
6. 　胡逸民. 调强适形放射治疗. 肿瘤放射物理学[M]. 北京: 原子能出版社，1999: 538-572.
7. 　Samuel Hellman. Treatment planning consideration in IMRT. A practical guide to intensity-modulated radiation therapy[M]. WI: Medical Physics publishing Madison, 2003: 103-122.
8. 　Luan S, Saia J, Young M. Approximation algorithm for minimizaing segments in radiation therapy[J]. Inf Proc Lett, 2007, 101(6): 239-244.
9. 　Engel K. A new algorithm for multileaf collimator field segmentation[J]. Discrete Applied Mathematics, 2005, 152(1-3): 35-51.
10. 　伍志红, 张九堂, 曾彪, 等. 鼻咽癌三种子野方案对调强放疗剂量分布的影响[J]. 医学临床研究, 2009, 26(2): 241-244.
11. 　陈真云, 马悦冰, 盛修贵, 等. 32例妇科恶性肿瘤术后调强适形放射治疗分析[J]. 中华肿瘤杂志, 2007, 29(4): 3058-308.
12. 　房辉, 李晔雄, 余子豪, 等. 前列腺癌三维适形和调强放疗的初步结果[J]. 中华放射肿瘤学杂志, 2006, 15(3): 197-200.
13. 　袁智勇, 高黎, 徐国镇, 等. 初治鼻咽癌调强放疗的初步结果[J]. 中华放射肿瘤学杂志, 2006, 15(4): 237-243.
14. 　蔡勇, 何玉香, 韩树奎, 等. 直肠癌盆腔常规放疗与三维适形放疗的剂量学研究[J]. 中华放射肿瘤学杂志, 2007, 16(3): 201-205.
15. 　Urbano MTG, Henrys AJ, Adams EJ, et al. Intensity-Modulated radiotherapy in patients with locally advanced rectal cancer reduces volume of bowel treated to high dose levels[J]. Int J Radiat Oncol Biol Phys, 2006, 65(3): 907-916.
16. 　耿辉, 戴建荣, 李晔雄, 等. 一种简单调强放疗技术应用的初步研究[J]. 中华放射肿瘤学杂志, 2006, 15(1): 411-415.

West China Medical Journal

Influence of Segment Number on the Planning of Intensity-modulated Radiotherapy for Postoperative Adjuvant Radiotherapy for Rectal Cancer

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