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Multiple‐estimate Monte Carlo calculation of the dose rate constant for a cesium‐131 interstitial brachytherapy seed
Author(s) -
Wittman Richard S.,
Fisher Darrell R.
Publication year - 2007
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 - 10.1118/1.2401653
Subject(s) - monte carlo method , brachytherapy , dosimetry , nuclear medicine , dose rate , ionization chamber , thermoluminescence , computational physics , consistency (knowledge bases) , constant (computer programming) , physics , mathematics , ionization , statistics , nuclear physics , medical physics , irradiation , medicine , radiation therapy , radiology , computer science , geometry , ion , quantum mechanics , programming language
The purpose of this study was to calculate a more accurate dose rate constant for theCs131(model CS‐1, IsoRay Medical, Inc., Richland, WA) interstitial brachytherapy seed. Previous measurements of the dose rate constant for this seed have been reported by others with incongruity. Recent direct measurements by thermoluminescence dosimetry and by gamma‐ray spectroscopy were about 15% greater than earlier thermoluminescence dosimetry measurements. Therefore, we set about to calculate independent values by a Monte Carlo approach that combined three estimates as a consistency check, and to quantify the computational uncertainty. The calculated dose rate constant for theCs131seed was 1.040 cGyh − 1U − 1for an ionization chamber model and 1.032 cGyh − 1U − 1for a circular ring model. A formal value of 2.2% uncertainty was calculated for both values. The range of our multiestimate values were from 1.032 to 1.061 cGyh − 1U − 1. We also modeled threeI125seeds with known dose rate constants to test the accuracy of this study's approach.