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Title: SU-E-T-270: Quality Control of Source Strength and Indexer Length in HDR Brachytherapy Using Sun Nuclear Mapcheck2

Abstract

Purpose: The goal of this work was to evaluate Sun Nuclear MapCheck2 capability for quantitative determination of both HDR source strength and position. Predictive power of Mapcheck2 dose matrix, originated by a microSelectron-v2 source from 22mm distance, was investigated. Methods: A Mick MultiDoc phantom with the 1400mm indexer length mark aligned over MapCheck2 central detector plus two additional 5cm plastic slabs were used as a composite phantom. Dose readings were transformed by applying published source anisotropy corrections and experimentally established radial dose and relative sensitivity factors. Angular dependence was not considered. Only readings from diodes located 2cm around the central detector were evaluated. The reproducibility of a fit between transformed dose readings and the ratio of virtual source strength and the square of source-detector distance was investigated. Four parameters were considered in the model: virtual source strength, lateral, longitudinal and vertical source positions. Final source strength calibration factor was calculated from the ratio of reference measurements and results from the fit. Results: Original lateral and longitudinal source position estimations had systematic errors of 0.39mm and 0.75mm. After subtracting these errors, both source positions were predicted with a standard deviation of 0.15mm. Results for vertical positions were reproducible with a standardmore » deviation of 0.05mm. The difference between calculated and reference source strengths from 34 independent measurement setups had a standard deviation of 0.3%. The coefficient of determination for the linear regression between known indexer lengths and results from the fit in the range 1400mm ± 5mm was 0.985. Conclusions: ource strength can be estimated with MapCheck2 at appropriate accuracy levels for quality control. Verification of indexer length with present implementation is more accurate than visual alternatives. Results can be improved by designing a coupling catheter phantom and refining relative diode calibration. Diode angular dependence in MapCheck2 does not play significant role.« less

Authors:
 [1]
  1. 21st Century Oncology, Bel Air, MD (United States)
Publication Date:
OSTI Identifier:
22351092
Resource Type:
Journal Article
Journal Name:
Medical Physics
Additional Journal Information:
Journal Volume: 41; Journal Issue: 6; Other Information: (c) 2014 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-2405
Country of Publication:
United States
Language:
English
Subject:
07 ISOTOPES AND RADIATION SOURCES; 60 APPLIED LIFE SCIENCES; ACCURACY; ANISOTROPY; BRACHYTHERAPY; CALIBRATION; CORRECTIONS; PHANTOMS; QUALITY CONTROL; RADIATION DOSES; VERIFICATION

Citation Formats

Morales, J. SU-E-T-270: Quality Control of Source Strength and Indexer Length in HDR Brachytherapy Using Sun Nuclear Mapcheck2. United States: N. p., 2014. Web. doi:10.1118/1.4888601.
Morales, J. SU-E-T-270: Quality Control of Source Strength and Indexer Length in HDR Brachytherapy Using Sun Nuclear Mapcheck2. United States. https://doi.org/10.1118/1.4888601
Morales, J. 2014. "SU-E-T-270: Quality Control of Source Strength and Indexer Length in HDR Brachytherapy Using Sun Nuclear Mapcheck2". United States. https://doi.org/10.1118/1.4888601.
@article{osti_22351092,
title = {SU-E-T-270: Quality Control of Source Strength and Indexer Length in HDR Brachytherapy Using Sun Nuclear Mapcheck2},
author = {Morales, J},
abstractNote = {Purpose: The goal of this work was to evaluate Sun Nuclear MapCheck2 capability for quantitative determination of both HDR source strength and position. Predictive power of Mapcheck2 dose matrix, originated by a microSelectron-v2 source from 22mm distance, was investigated. Methods: A Mick MultiDoc phantom with the 1400mm indexer length mark aligned over MapCheck2 central detector plus two additional 5cm plastic slabs were used as a composite phantom. Dose readings were transformed by applying published source anisotropy corrections and experimentally established radial dose and relative sensitivity factors. Angular dependence was not considered. Only readings from diodes located 2cm around the central detector were evaluated. The reproducibility of a fit between transformed dose readings and the ratio of virtual source strength and the square of source-detector distance was investigated. Four parameters were considered in the model: virtual source strength, lateral, longitudinal and vertical source positions. Final source strength calibration factor was calculated from the ratio of reference measurements and results from the fit. Results: Original lateral and longitudinal source position estimations had systematic errors of 0.39mm and 0.75mm. After subtracting these errors, both source positions were predicted with a standard deviation of 0.15mm. Results for vertical positions were reproducible with a standard deviation of 0.05mm. The difference between calculated and reference source strengths from 34 independent measurement setups had a standard deviation of 0.3%. The coefficient of determination for the linear regression between known indexer lengths and results from the fit in the range 1400mm ± 5mm was 0.985. Conclusions: ource strength can be estimated with MapCheck2 at appropriate accuracy levels for quality control. Verification of indexer length with present implementation is more accurate than visual alternatives. Results can be improved by designing a coupling catheter phantom and refining relative diode calibration. Diode angular dependence in MapCheck2 does not play significant role.},
doi = {10.1118/1.4888601},
url = {https://www.osti.gov/biblio/22351092}, journal = {Medical Physics},
issn = {0094-2405},
number = 6,
volume = 41,
place = {United States},
year = {Sun Jun 01 00:00:00 EDT 2014},
month = {Sun Jun 01 00:00:00 EDT 2014}
}