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"Feasibility of gold fiducial markers as a surrogate for GTV position in image-guided radiotherapy of rectal cancer"

Roy P.J. van den Ende, Ellen M. Kerkhof, L.S. Rigter, M. van Leerdam, Femke P. Peters, B. van Triest, Marius Staring, Corrie A.M. Marijnen and Uulke A. van der Heide

Abstract

Purpose: To evaluate the feasibility of fiducial markers as a surrogate for GTV position in image-guided radiotherapy of rectal cancer.

Methods and Materials: We analyzed 35 fiducials in 19 rectal cancer patients who received short course radiotherapy or long-course chemoradiotherapy (LC-CRT). Two MRI exams and daily pre- and post-irradiation CBCT scans were acquired in the first week of radiotherapy. Weekly CBCT scans were acquired thereafter for patients that received LC-CRT. Between the two MRI exams, the fiducial displacement relative to the center of gravity of the GTV (COGGTV) and the COGGTV displacement relative to bony anatomy was determined. Using the CBCT scans, inter- and intrafraction fiducial displacement relative to bony anatomy was determined.

Results: The systematic error of the fiducial displacement relative to the COGGTV was 2.8, 2.4 and 4.2 mm in the left-right (LR), anterior-posterior (AP) and craniocaudal (CC) direction. Large interfraction systematic errors of up to 8.0 and random errors up to 4.7 mm were found for COGGTV and fiducial displacements relative to bony anatomy, mostly in the AP and CC directions. For tumors located in the mid- and upper rectum these errors were 9.4 (systematic) and 5.6 mm (random) compared to 4.9 and 2.9 mm for tumors in the lower rectum. Systematic and random errors of the intrafraction fiducial displacement relative to bony anatomy were <2.1 mm in all directions.

Conclusions: Large interfraction errors of the COGGTV and the fiducials relative to bony anatomy were found. Therefore, despite the observed fiducial displacement relative to the COGGTV, the use of fiducials as a surrogate for GTV position reduces the required margins in the AP and CC direction for a GTV boost using image-guided radiotherapy of rectal cancer. This reduction may be larger in patients with tumors located in the mid- and upper rectum compared to the lower rectum.

 

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Copyright © 2019 by the authors. Published version © 2019 by . Personal use of this material is permitted. However, permission to reprint or republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works, must be obtained from the copyright holder.

 

BibTeX entry

@inproceedings{vandenEnde:2019,
author = "{Roy P.J. van den Ende and Ellen M. Kerkhof and L.S. Rigter and M. van Leerdam and Femke P. Peters and B. van Triest and Marius Staring and Corrie A.M. Marijnen and Uulke A. van der Heide}",
title = "{Feasibility of gold fiducial markers as a surrogate for GTV position in image-guided radiotherapy of rectal cancer}",
booktitle = "{American Association of Physicists in Medicine (AAPM)}",
address = "{San Antonio, TX, USA}",
month = "{July}",
year = "{2019}",
}

last modified: 09-05-2019 |webmaster |Copyright 2004-2019 © by Marius Staring