en Radiation Biology Radiation Biology تحقيق بديع Original Research <div style="text-align: justify;"><span style="font-size:10pt"><span style="text-justify:newspaper"><span style="text-kashida-space:50%"><span style="line-height:119%"><span style="font-family:Calibri"><span style="color:black"><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Background:</span></span></span></span></span></span> <span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">This study evaluates the impact of body contouring changes on delivered dose and proposes a method to identify target dose deviations exceeding 5%. </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Materials and Methods: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">Five CT datasets were created by simulating body contouring reductions of 3mm, 6mm, 9mm, 12mm, and 15mm from the original planning CT. Using the same iso-center and Volumetric Modulated Arc Therapy (VMAT) plan, new plans (P3, P6, P9, P12, P15) were generated for new five CT datasets (body contouring reductions of 3mm, 6mm, 9mm, 12mm, and 15mm) respectively. Dose distributions and changes in dosimetric parameters for the Planning Target Volume (PTV) and Organs at Risk (OARs), including the small intestine, rectum, bone marrow, femoral head, and bladder, were analyzed. </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Results: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">Progressive weight loss increased doses to PTVs and OARs. PTV D50 increased by 1.32%, 2.35%, 3.62%, 5.18%, and 6.24% for 3mm, 6mm, 9mm, 12mm, and 15mm reductions, respectively. The small intestine V45 exceeded 195cc and the rectum V50 surpassed 50% at 12mm and 15mm. Bone marrow doses remained below the V40 threshold of 37%. When reductions reached 12mm and 15mm, regions with dose deviations >5% (250cGy) covered 31.81% and 178.08% of the PTV. </span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="color:#1f497d"><span style="font-style:italic"><span style="font-weight:bold"><span style="language:en-US">Conclusion: </span></span></span></span></span></span><span lang="en-US" style="font-size:9.0pt"><span style="font-family:Calibri"><span style="language:en-US">Weight loss-induced body contouring reductions significantly affect PTV and OAR doses. Re-scanning and re-planning are recommended when contour reductions exceed 12mm or waist circumference decreases by >75mm.</span></span></span></span></span></span></span></span></span></div> Radiotherapy, volumetric modulated arc therapy, weight loss, dosimetry, cervical neoplasms. 881 887 http://ijrr.com/browse.php?a_code=A-10-1-1410&slc_lang=en&sid=1 Z. Cao 7900319475328460032180 7900319475328460032180 No Department of Oncology, Maternal and Child Health Hospital of Hubei Province, Hubei, China W. Xu 7900319475328460032181 7900319475328460032181 No Department of Radiation and Medical Oncology, Hubei Key Laboratory of Tumor Biological Behaviors, Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuhan, China J. Shen 7900319475328460032182 7900319475328460032182 No Department of Radiation and Medical Oncology, Hubei Key Laboratory of Tumor Biological Behaviors, Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuhan, China L. Li Lilinjun00417@126.com 7900319475328460032183 7900319475328460032183 Yes Department of Oncology, Maternal and Child Health Hospital of Hubei Province, Hubei, China H. Liu hbzkznyy@163.com 7900319475328460032184 7900319475328460032184 No Department of Radiation and Medical Oncology, Hubei Key Laboratory of Tumor Biological Behaviors, Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuhan, China C. Chen chenc20022002@163.com 7900319475328460032185 7900319475328460032185 No Department of Radiation and Medical Oncology, Hubei Key Laboratory of Tumor Biological Behaviors, Hubei Cancer Clinical Study Center, Zhongnan Hospital of Wuhan University, Wuhan, China