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Error Analysis of non-TLD HDR Brachytherapy Dosimetric Techniques

Amoush, Ahmad A.
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307105202

Abstract Details

2011, PhD, University of Cincinnati, Engineering and Applied Science: Nuclear and Radiological Engineering.
The American Association of Physicists in Medicine Task Group Report43 (AAPM-TG43) and its updated version TG-43U1 rely on the LiF TLD detector to determine the experimental absolute dose rate for brachytherapy. The recommended uncertainty estimates associated with TLD experimental dosimetry include 5% for statistical errors (Type A) and 7% for systematic errors (Type B). TG-43U1 protocol does not include recommendation for other experimental dosimetric techniques to calculate the absolute dose for brachytherapy. This research used two independent experimental methods and Monte Carlo simulations to investigate and analyze uncertainties and errors associated with absolute dosimetry of HDR brachytherapy for a Tandem applicator. An A16 MicroChamber and one dose MOSFET detectors were selected to meet the TG-43U1 recommendations for experimental dosimetry. Statistical and systematic uncertainty analyses associated with each experimental technique were analyzed quantitatively using MCNPX 2.6 to evaluate source positional error, Tandem positional error, the source spectrum, phantom size effect, reproducibility, temperature and pressure effects, volume averaging, stem and wall effects, and Tandem effect. Absolute dose calculations for clinical use are based on Treatment Planning System (TPS) with no corrections for the above uncertainties. Absolute dose and uncertainties along the transverse plane were predicted for the A16 microchamber. The generated overall uncertainties are 22%, 17%, 15%, 15%, 16%, 17%, and 19% at 1cm, 2cm, 3cm, 4cm, and 5cm, respectively. Predicting the dose beyond 5cm is complicated due to low signal-to-noise ratio, cable effect, and stem effect for the A16 microchamber. Since dose beyond 5cm adds no clinical information, it has been ignored in this study. The absolute dose was predicted for the MOSFET detector from 1cm to 7cm along the transverse plane. The generated overall uncertainties are 23%, 11%, 8%, 7%, 7%, 9%, and 8% at 1cm, 2cm, 3cm, and 4cm, 5cm, 6cm, and 7cm, respectively. The Nucletron Freiburg flap applicator is used with the Nucletron remote afterloader HDR machine to deliver dose to surface cancers. Dosimetric data for the Nucletron 192Ir source were generated using Monte Carlo simulation and compared with the published data. Two dimensional dosimetric data were calculated at two source positions; at the center of the sphere of the applicator and between two adjacent spheres. Unlike the TPS dose algorithm, The Monte Carlo code developed for this research accounts for the applicator material, secondary electrons and delta particles, and the air gap between the skin and the applicator.
Henry Spitz, PhD (Committee Chair)
Howard Elson, PhD (Committee Member)
Sam Glover, PhD (Committee Member)
William Kassing, PhD (Committee Member)
Michael Lamba, PhD (Committee Member)
122 p.
Nuclear Engineering
HDR Brachytherapy; MCNPX; A16 Microchamber; MOSFET

Recommended Citations

Citations

  • Amoush, A. A. (2011). Error Analysis of non-TLD HDR Brachytherapy Dosimetric Techniques [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307105202

    APA Style (7th edition)

  • Amoush, Ahmad. Error Analysis of non-TLD HDR Brachytherapy Dosimetric Techniques. 2011. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307105202.

    MLA Style (8th edition)

  • Amoush, Ahmad. "Error Analysis of non-TLD HDR Brachytherapy Dosimetric Techniques." Doctoral dissertation, University of Cincinnati, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307105202

    Chicago Manual of Style (17th edition)

ucin1307105202
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© 2011, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.