الفهرس 
English Cover
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Abstract
Purpose: The purpose of the present study was to quantify rectum and bladder volume changes and to assess the motion of rectum using Cone Beam Computed Tomography [CBCT] scans taken during pre-operative Concurrent Chemo-Radiation Therapy (CCRT) for rectal cancer patients being treated NEMROCK and analyze the impact of the above mentioned changes on tumor coverage and organ at risk toxicity Patients and methods: There were 10 patients in this study undergoing preoperative CRT for rectal cancer. Each GTV-rectum and bladder were contoured on all planning CTs and CBCTs (Week 1, 2, 3, 4, 5). The planning CTs and weekly CBCTs were matched to analyze the inter-fractional volumetric changes of rectum and bladder as well as rectal wall motion during the treatment course and the weekly toxicity profile was recorded. Results: Planning CTs and series of each 5 CBCTs for 10 patients were analyzed in this study. The rectal volume tended to shrink week after week. The mean rectal volumes (± SD) on planning CT and CBCTs (on W0, W1, W2, W3, W4 and W5) were 61.07 (±3.03) cc, 61.31 (±24.00) cc, 48.59 (±21.07) cc, 38.51 (±21.06) cc, 33.79 (±19.22) cc, and 28.66 (±17.82) cc, respectively. The shrinking comparisons between planning CT versus CBCTs were significant on W3 (p = 0.023), W4 (p = 0.005) and W5 (p = 0.003) .The mean bladder volumes were 167.00 (±19.76) cc,180.13 (±18.83) cc, 147.64 (±18.06) cc, 148.92 (±14.40), 150.42 (±16.83) cc, and 149.85 (±16.36) cc and for the bladder, volumetric variations were not significant