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Evaluation of the buildup effect of an 192 Ir high dose‐rate brachytherapy source
Author(s) -
Park H. C.,
Almond P. R.
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 - 10.1118/1.596762
Subject(s) - brachytherapy , monte carlo method , dose rate , physics , dosimetry , nuclear medicine , computational physics , common emitter , ionization chamber , ionization , medical physics , mathematics , statistics , radiation therapy , medicine , ion , optoelectronics , quantum mechanics
The buildup effect of the 192 Ir radioactive source employed as a gamma emitter of the Selectron high dose‐rate (HDR) afterloader was evaluated by studying the ratio of exposure in water to exposure in air as a function of distance. In 1968, Meisberger et al . [Radiology 90 , 953‐957 (1968)] calculated a third‐order polynomial fit to a selected average between measured and calculated values. The objective of this investigation, however, is to evaluate the factor for the 192 Ir source configuration used in the HDR system, which was different from the source design used by Meisberger et al . This paper presents the measured ratio using an ionization chamber and the calculated ratio using a Monte Carlo simulation code. The experimental and theoretical results show only minor disagreement with the data of Meisberger et al .. However, the results show significant disagreement when they are compared to the model developed by van Kleffens and Star [Int. J. Radiat. Oncol. Biol. Phys. 5 557–563 (1979)], which may indicate the need to reevaluate the algorithm presently employed in HDR treatment planning system. The comparison with other published data will be discussed.