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The importance of applicator design for intraluminal brachytherapy of rectal cancer
Author(s) -
Hansen Johnny Witterseh,
Jakobsen Anders
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 - 10.1118/1.2207143
Subject(s) - electromagnetic shielding , shield , shields , brachytherapy , homogeneity (statistics) , materials science , dose rate , optics , bent molecular geometry , dosimetry , cylinder , biomedical engineering , nuclear medicine , radiation therapy , composite material , medicine , geometry , medical physics , physics , geology , radiology , mathematics , petrology , statistics
An important aspect of designing an applicator for radiation treatment of rectal cancer is the ability to minimize dose to the mucosa and noninvolved parts of the rectum wall. For this reason we investigated a construction of a flexible multichannel applicator with several channels placed along the periphery of a cylinder and a construction of a rigid cylinder with a central channel and interchangeable shields. Calculations of the dose gradient, dose homogeneity in the tumor, and shielding ability were performed for the two applicators in question. Furthermore, the influence on dose distribution around a flexible multichannel applicator from an unintended off‐axis positioning of the source inside a bent channel was investigated by film measurements on a single bent catheter. Calculations showed that a single‐channel applicator with interchangeable shields yields a higher degree of shielding and has a better dose homogeneity in the tumor volume than that of a multichannel applicator. A single‐channel applicator with interchangeable shields was manufactured, and the influence of different size of shield angle on dose rate in front of and behind the shields was measured. While dose rate in front of the shield and shielding ability are closely independent of the size of the shield angle when measured 1 cm from the applicator surface, dose rate in more distant volumes will to some extent be influenced by shield angle due to volume scatter conditions.