An experimental and computational investigation of the standard temperature-pressure correction factor for ion chambers in kilovoltage x rays

Medical Physics
Daniel J La RussaD W O Rogers

Abstract

For ion chambers with cavities open to the surrounding atmosphere, the response measured at a given temperature and pressure must be corrected using the standard temperature-pressure correction factor (P(TP)). A previous paper based solely on Monte Carlo simulations [D. J. La Russa and D. W. O. Rogers, Med. Phys. 33, 4590-4599 (2006)] pointed out the shortcomings of the P(TP) correction factor when used to correct the response of non-air-equivalent chambers for low-energy x-ray beams. This work presents the results of several experiments that corroborate these calculations for a number of ion chambers. Monte Carlo simulations of the experimental setup revealed additional insight into the various factors affecting the extent of the breakdown of P(TP), including the effect of impurities and the sensitivity to chamber dimensions. For an unfiltered 60 kV beam, the P(TP)-corrected response of an NE 2571 ion chamber measured at 0.7 atm was 2.5% below the response measured at reference conditions. In general, Monte Carlo simulations of the experimental setup using EGSnrc were within 0.5% of measured values. EGSnrc-calculated values of air kerma calibration coefficients (N(K)) at low x-ray energies are also provided as a means of estim...Continue Reading

References

Apr 1, 1991·Physics in Medicine and Biology·C M Ma, A E Nahum
May 1, 1995·Medical Physics·D W RogersT R Mackie
Aug 12, 1999·Physics in Medicine and Biology·F VerhaegenY Namito
Feb 28, 2003·Medical Physics·Ernesto Mainegra-HingD W O Rogers
Jul 11, 2003·Medical Physics·Lesley A BuckleyD W O Rogers
Jun 24, 2005·Physics in Medicine and Biology·J P McCaffreyM McEwen
Jun 24, 2005·Physics in Medicine and Biology·Gustaf UllmanGudrun Alm Carlsson
Sep 13, 2006·Medical Physics·Ernesto Mainegra-Hing, Iwan Kawrakow

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Citations

Mar 19, 2013·Australasian Physical & Engineering Sciences in Medicine·Robin Hill
Sep 21, 2011·Medical Physics·B R MuirD W O Rogers
Dec 17, 2010·Medical Physics·B R Muir, D W O Rogers
Jul 3, 2016·Medical Physics·V N Malkov, D W O Rogers
Dec 24, 2016·Journal of Synchrotron Radiation·Andrew W StevensonJessica E Lye
Mar 4, 2014·Physics in Medicine and Biology·Robin HillClive Baldock

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