Evaluation of small bowel motion and feasibility of using the peritoneal space to replace bowel loops for dose constrain
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RESEARCH
Open Access
Evaluation of small bowel motion and feasibility of using the peritoneal space to replace bowel loops for dose constraints during intensity-modulated radiotherapy for rectal cancer Siyuan Li1,2†, Yanping Gong3†, Yongqiang Yang1, Qi Guo1, Jianjun Qian1* and Ye Tian1*
Abstract Background: The goal of this study was to assess small bowel motion and explore the feasibility of using peritoneal space (PS) to replace bowel loops (BL) via the dose constraint method to spare the small bowel during intensity-modulated radiotherapy (IMRT) for rectal cancer. Methods: A total of 24 patients with rectal cancer who underwent adjuvant or neoadjuvant radiotherapy were selected. Weekly repeat CT scans from pre-treatment to the fourth week of treatment were acquired and defined as Plan, 1 W, 2 W, 3 W, and 4 W. The 4 weekly CT scans were co-registered to the Plan CT, BL and PS contours were delineated in all of the scans, an IMRT plan was designed on Plan CT using PS constraint method, and then copied to the 4 weekly CT scans. The dose-volume, normal tissue complication probability (NTCP) of the small bowel and their variations during treatment were evaluated. Results: Overall, 109 sets of CT scans from 24 patients were acquired, and 109 plans were designed and copied. The BL and PS volumes were 250.3 cc and 1339.3 cc. The V15 of BL and PS based plan of pre-treatment were 182.6 cc and 919.0 cc, the shift% of them were 28.9 and 11.3% during treatment (p = 0.000), which was less in the prone position than in the supine position (25.2% vs 32.1%, p = 0.000; 9.9% vs 14.9%, p = 0.000). The NTCPC and NTCPA based plan of pre-treatment were 2.0 and 59.2%, the shift% during treatment were 46.1 and 14.0% respectively. Majority of BL’s Dmax and V15 were meet the safety standard during treatment using PS dose limit method except 3 times (3/109) of V15 and 5 times of Dmax (5/109). (Continued on next page)
* Correspondence: [email protected]; [email protected] † Siyuan Li and Yanping Gong are contributed equally to this study. 1 Department of Radiotherapy & Oncology, Second Affiliated Hospital of Soochow University, Institute of Radiotherapy and Oncology, Soochow University, Suzhou Key Laboratory for Radiation Oncology, Suzhou 215004, China Full list of author information is available at the end of the article © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, y
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