PMID: 11929025Apr 4, 2002Paper

Measurement of absorbed dose with a bone-equivalent extrapolation chamber

Medical Physics
F DeBloisE B Podgorsak

Abstract

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water and bone-equivalent material was used for determining absorbed dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain absorbed dose in bone for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chambe...Continue Reading

References

May 1, 1995·Medical Physics·D W RogersT R Mackie
Jul 1, 1993·Medical Physics·A Kosunen, D W Rogers
Apr 1, 1997·Medical Physics·C E Zankowski, E B Podgorsak
Jan 7, 2003·Medical Physics·B R B WaltersD W O Rogers
Sep 1, 1955·Radiology·S GENNA, J S LAUGHLIN

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Citations

Jun 19, 2007·Applied Radiation and Isotopes : Including Data, Instrumentation and Methods for Use in Agriculture, Industry and Medicine·M L Oliveira, L V E Caldas

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