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Title: SU-F-J-145: MRI-Guided Interventional Boost Radiotherapy for Rectal Cancer: Investigating the Feasibility of Adapting the Anatomy

Abstract

Purpose: The recent development of an MRI-linac allows adaptation of treatments to the anatomy of the moment. This anatomy, in turn, could be altered into a more favorable situation for radiotherapy purposes. The purpose of this study is to investigate the potential dosimetric benefits of manipulating rectal anatomy in MRI-guided interventional external-beam radiotherapy for rectal cancer. Methods: For this retrospective analysis, four patients (1M/3F) diagnosed with rectal cancer were included. These underwent MR-imaging using sonography transmission gel as endorectal contrast at time of diagnosis and standard, non-contrast, MR-imaging prior to radiotherapy planning. In the contrast scan, the rectum is inflated by the inserted contrast gel, thereby potentially increasing the distance between tumor and the organs-at-risk (OAR). Both anatomies were delineated and 7- beam IMRT-plans were calculated for both situations (RT-standard and RT-inflated), using in-house developed treatment planning software. Each plan was aimed to deliver 15Gy to the planning target volume (PTV; tumor+3mm margin) with a D99>95% and Dmax<120% of the planned dose. The D2cc dose to the OAR were then compared for both situations. Results: At equal (or better) target coverage, we found a mean reduction in D2cc of 4.1Gy/237% [range 2.6Gy–6.3Gy/70%–621%] for the bladder and of 2.0Gy/145% [range −0.7Gy–7.9Gy/−73%–442%]more » for the small-bowel, for the RT-inflated compared to the RT-standard plans. For the three female patients, a reduction in D2cc of 5.2Gy/191% [range 3.2Gy–9.2Gy/44%–475%] for the gynecological organs was found. We found all D2cc doses to be better for the RT-inflated plans, except for one patient for whom the bladder D2cc dose was slightly increased. Conclusion: Reduction of OAR dose by manipulation of anatomy is feasible. Inflation of the rectum results in more distance between OAR and PTV. This leads to a substantial reduction in dose to OAR at equal or better target coverage.« less

Authors:
; ; ; ; ;  [1]
  1. University Medical Center Utrecht, Utrecht, Utrecht (Netherlands)
Publication Date:
OSTI Identifier:
22634748
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; ANATOMY; BEAMS; BIOMEDICAL RADIOGRAPHY; BLADDER; COMPUTER CODES; DIAGNOSIS; LINEAR ACCELERATORS; NEOPLASMS; NMR IMAGING; PATIENTS; PLANNING; RADIATION DOSES; RADIOTHERAPY; RECTUM

Citation Formats

Kleijnen, J J E, Couwenberg, A M, Asselen, B van, Lagendijk, J J W, Intven, M, and Raaymakers, B W. SU-F-J-145: MRI-Guided Interventional Boost Radiotherapy for Rectal Cancer: Investigating the Feasibility of Adapting the Anatomy. United States: N. p., 2016. Web. doi:10.1118/1.4956053.
Kleijnen, J J E, Couwenberg, A M, Asselen, B van, Lagendijk, J J W, Intven, M, & Raaymakers, B W. SU-F-J-145: MRI-Guided Interventional Boost Radiotherapy for Rectal Cancer: Investigating the Feasibility of Adapting the Anatomy. United States. doi:10.1118/1.4956053.
Kleijnen, J J E, Couwenberg, A M, Asselen, B van, Lagendijk, J J W, Intven, M, and Raaymakers, B W. Wed . "SU-F-J-145: MRI-Guided Interventional Boost Radiotherapy for Rectal Cancer: Investigating the Feasibility of Adapting the Anatomy". United States. doi:10.1118/1.4956053.
@article{osti_22634748,
title = {SU-F-J-145: MRI-Guided Interventional Boost Radiotherapy for Rectal Cancer: Investigating the Feasibility of Adapting the Anatomy},
author = {Kleijnen, J J E and Couwenberg, A M and Asselen, B van and Lagendijk, J J W and Intven, M and Raaymakers, B W},
abstractNote = {Purpose: The recent development of an MRI-linac allows adaptation of treatments to the anatomy of the moment. This anatomy, in turn, could be altered into a more favorable situation for radiotherapy purposes. The purpose of this study is to investigate the potential dosimetric benefits of manipulating rectal anatomy in MRI-guided interventional external-beam radiotherapy for rectal cancer. Methods: For this retrospective analysis, four patients (1M/3F) diagnosed with rectal cancer were included. These underwent MR-imaging using sonography transmission gel as endorectal contrast at time of diagnosis and standard, non-contrast, MR-imaging prior to radiotherapy planning. In the contrast scan, the rectum is inflated by the inserted contrast gel, thereby potentially increasing the distance between tumor and the organs-at-risk (OAR). Both anatomies were delineated and 7- beam IMRT-plans were calculated for both situations (RT-standard and RT-inflated), using in-house developed treatment planning software. Each plan was aimed to deliver 15Gy to the planning target volume (PTV; tumor+3mm margin) with a D99>95% and Dmax<120% of the planned dose. The D2cc dose to the OAR were then compared for both situations. Results: At equal (or better) target coverage, we found a mean reduction in D2cc of 4.1Gy/237% [range 2.6Gy–6.3Gy/70%–621%] for the bladder and of 2.0Gy/145% [range −0.7Gy–7.9Gy/−73%–442%] for the small-bowel, for the RT-inflated compared to the RT-standard plans. For the three female patients, a reduction in D2cc of 5.2Gy/191% [range 3.2Gy–9.2Gy/44%–475%] for the gynecological organs was found. We found all D2cc doses to be better for the RT-inflated plans, except for one patient for whom the bladder D2cc dose was slightly increased. Conclusion: Reduction of OAR dose by manipulation of anatomy is feasible. Inflation of the rectum results in more distance between OAR and PTV. This leads to a substantial reduction in dose to OAR at equal or better target coverage.},
doi = {10.1118/1.4956053},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}