skip to main content

Title: Multiple-estimate Monte Carlo calculation of the dose rate constant for a cesium-131 interstitial brachytherapy seed

The purpose of this study was to calculate a more accurate dose rate constant for the Cs-131 (model CS-1, IsoRay Medical, Inc., Richland, Washington) 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 percent 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 the Cs-131 seed was 1.040 cGy h^{-1} U^{-1} for an ionization chamber model and 1.032 cGy h^{-1} U^{-1} for a circular ring model. A formal value of 2.2% uncertainty was calculated for both values. The range of our multi-estimate values were from 1.032 cGy h^{-1} U^{-1} to 1.061 cGy h^{-1} U^{-1}. We also modeled three I-125 seeds with known dose rate constants to test the accuracy of this study's approach.
Authors:
;
Publication Date:
OSTI Identifier:
898096
Report Number(s):
PNNL-SA-48677
600301010; TRN: US0701563
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics, 34(1):49-54
Research Org:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; BRACHYTHERAPY; CESIUM 131; DOSE RATES; DOSIMETRY; MONTE CARLO METHOD Cesium-131 seed; dosimetry; brachytherapy; Monte Carlo; MCNP