Three-Dimensional Dose Addition of External Beam Radiotherapy and Brachytherapy for Oropharyngeal Patients Using Nonrigid Registration

Journal Article · Fri Jul 15 04:00:00 EDT 2011 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/j.ijrobp.2010.10.006· OSTI ID:21587607

Hoogeman, Mischa S; Teguh, David N; Al-Mamgani, Abrahim; Kolkman-Deurloo, Inger-Karine K; Bondar, Luiza; Levendag, Peter C; Heijmen, Ben J.M. ^[1]

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1. Department of Radiation Oncology, Daniel den Hoed Cancer Center, Erasmus Medical Center, Rotterdam (Netherlands)

Purpose: To develop and evaluate a method for adding dose distributions of combined external beam radiotherapy (EBRT) and brachytherapy (BT) for oropharyngeal patients. 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{sub 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 {alpha}/{beta} parameter for EQD{sub 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). 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). 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 {alpha}/{beta} values.

• OSTI ID: 21587607
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 4 Vol. 80; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BODY
BRACHYTHERAPY
CAT SCANNING
COMPUTERIZED TOMOGRAPHY
DIAGNOSTIC TECHNIQUES
DOSE EQUIVALENTS
DOSES
FRACTIONATION
GLANDS
HEAD
MEDICINE
MUSCLES
NECK
NUCLEAR MEDICINE
ORGANS
RADIATION DOSE DISTRIBUTIONS
RADIATION DOSES
RADIOLOGY
RADIOTHERAPY
SALIVARY GLANDS
SEPARATION PROCESSES
THERAPY
TOMOGRAPHY