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SU‐FF‐T‐252: HDR Endorectal Brachytherapy: Quality Assurance
Author(s) -
Devic S,
Vuong T,
Evans M,
Podgorsak E,
Poon E,
Verhaegen F
Publication year - 2006
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.2241173
Subject(s) - brachytherapy , quality assurance , nuclear medicine , medical physics , dosimetry , medicine , radiation therapy , radiology , pathology , external quality assessment
Purpose: Fractionated high‐dose rate endorectal brachytherapy has been developed in our institution as a pre‐operative down‐staging modality. Since the treatment is fractionated (26 Gy/4) it is essential to reproduce the treatment planning dose distribution on a daily basis. In this paper we present the Quality Assurance (QA) steps developed to ensure patient based daily dose reproducibility. Method and Materials: The applicator used has a cylindrical symmetry. In addition to the applicator auto‐radiographs used for the catheter physical length determination, there are two additional steps that have to be performed in order to reproduce a treatment planning dose distribution on a daily basis. Another correction has to be performed on a daily basis for rotation of the catheter channels. For this purpose, we use uniquely coded “dummy” source inserts that show themselves on a daily radiograph. The applicator is rotated and radiograph repeated until perfect alignment is achieved. Results: Since the applicator might not be placed to the same depth inside the rectal lumen, there is a shift along the catheter axis that has to be performed on a daily basis. The amount of shift is determined by comparison of a daily radiograph and treatment planning DRR. Conclusions: Reproduction of the treatment planning dose distribution on a daily basis is crucial for the success of the fractionated 3D based brachytherapy treatments. Due to the cylindrical symmetry, two types of adjustments are necessary: applicator rotation and dose distribution shift along the applicator axis.