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Three-dimensional dose addition of external beam radiotherapy and brachytherapy for oropharyngeal patients using nonrigid registration.

Authors :
Vásquez Osorio EM
Hoogeman MS
Teguh DN
Al-Mamgani A
Kolkman-Deurloo IK
Bondar L
Levendag PC
Heijmen BJ
Source :
International journal of radiation oncology, biology, physics [Int J Radiat Oncol Biol Phys] 2011 Jul 15; Vol. 80 (4), pp. 1268-77. Date of Electronic Publication: 2010 Dec 02.
Publication Year :
2011

Abstract

Purpose: To develop and evaluate a method for adding dose distributions of combined external beam radiotherapy (EBRT) and brachytherapy (BT) for oropharyngeal patients.<br />Methods and Materials: Two computed tomography (CT) scans were used for 5 patients: the EBRT CT, used for EBRT planning, and the BT CT, acquired after catheter implantation. For each scan, the salivary glands and the chewing and swallowing muscles were contoured, and a dose distribution was calculated. A nonrigid transformation was obtained by registering the organs' surfaces. Then the BT dose distribution was mapped onto the EBRT dose distribution by applying the transformation obtained. To account for differences in fractionation, the physical doses were converted to equivalent dose in 2 Gy (EQD(2)), and the total dose was found by adding dose voxel by voxel. The robustness of the dose addition was investigated by varying delineations and input parameters of the registration method and by varying the α/β parameter for EQD(2). The effect of the perturbations was quantified using dose-volume histograms (DVH) and gamma analyses (distance-to-agreement/dose-difference = 1 mm/1 Gy).<br />Results: The variations in input parameters and delineations caused only small perturbations in the DVH of the added dose distributions. For most organs the gamma index was low, and it was moderately elevated for organs lying in areas with a steep gradient (median gamma index ≤ 2.3 for constrictor muscles, ≤ 0.7 for all other organs).<br />Conclusions: The presented method allows adding dose distributions of combined EBRT and BT for oropharyngeal patients. In general, the method is reliable and robust with respect to uncertainties in organ delineation, perturbations in input parameters of the method, and α/β values.<br /> (Copyright © 2011 Elsevier Inc. All rights reserved.)

Details

Language :
English
ISSN :
1879-355X
Volume :
80
Issue :
4
Database :
MEDLINE
Journal :
International journal of radiation oncology, biology, physics
Publication Type :
Academic Journal
Accession number :
21129854
Full Text :
https://doi.org/10.1016/j.ijrobp.2010.10.006