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Dose distributions produced by shielded applicators using 241 Am for intracavitary irradiation of tumors in the vagina
Author(s) -
Muench Philip James,
Nath Ravinder
Publication year - 1992
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 - 10.1118/1.596763
Subject(s) - shielded cable , irradiation , photon , brachytherapy , shields , dosimetry , materials science , fluence , optics , photoelectric effect , nuclear medicine , absorption (acoustics) , electromagnetic shielding , physics , radiation therapy , medicine , nuclear physics , radiology , electrical engineering , engineering , composite material
Dosimetric characteristics of shielded vaginal applicators containing encapsulated 241 Am sources are investigated in this work. Encapsulated 241 Am sources emit primarily 60‐keV photons which are more effectively shielded by thin layers of high atomic number materials than the 662‐keV photons from 137 Cs sources. With 241 Am, it is possible to achieve almost unidirectional irradiation of localized vaginal tumors. The drastic decrease in irradiation volume on the contralateral side (uninvolved with tumor) is observed to decrease dose by up to 20%, even in the forward direction (unshielded side toward the tumor) of the applicator. A possible explanation for the observed effects of shields in both the forward and backward directions is the reduction of scattered photon fluence due to absorption of photons in the lead shield via photoelectric effect. Current theoretical models do not include this perturbation effect caused by shields on brachytherapy applicators.