A PROPOSED METHODOLOGY TO ASSESS HDR [superscript]192Ir RADIAL DOSE WITH FRICKE DOSIMETRY

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Sidi Mohammed Benhabib (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Advisor

Campos Carlos Austerlitz

Abstract: The radial absorbed dose to water D(r theta) a quantity not yet directly measured with primary standards was assessed with the Fricke solution which has been considered as an absolute aqueous solution to perform dosimetry. To determine D(r=2 cm theta=90°) a hollow quasi-water Fricke ring device filled with Fricke solution was designed to measure the change in the optical density in the Fricke solution at 303 nm wavelength caused by the exposure from a HDR 192Ir radioactive source positioned in its center inside a 15~15~15 cm[superscript]3 PMMA water phantom. A mini-irradiator was also designed and constructed to determine the product of the molar extinction coefficient and the chemical yield value of the Fricke solution at 303 nm against an A-12 ion chamber in which its main dosimetric parameters to determine the absorbed dose to water were calculated using the PENELOPE Monte Carlo code. To enhance dosimetric accuracy a large number of measurements were performed with both the quasi-water Fricke ring device and with the mini-irradiator calibration device. The radial absorbed dose to water at r = 2 cm and theta = 90° determined with the quasi-water Fricke ring device was compared against that determined with the HDR treatment planning system Ocentra. The results have shown that if the quantity D(r = 1 cm theta = 90°) is replaced by D(r = 2 cm theta= 90°) the methodology employed in this work may be used for clinical applications to determine the absolute radial absorbed dose to water with accuracy comparable to those assessed with Farmer and well-type ion chambers. 

Additional Information

Publication

Dissertation

Date: 2011

Keywords

Physics, Biophysics, Medicine, AAPM TG43, Absorbed dose to water, Dosimetry, Fricke solution, HDR 192Ir, PENELOPE MC code

Subjects

Iridium--Isotopes

Fricke dosimeters

Ferrous sulfate

Radiation

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