Characterization of PTW-31015 PinPoint ionization chambers in photon and proton beams

Physics in Medicine and Biology
A CarlinoH Palmans

Abstract

The increased use of complex forms of radiotherapy using small-field photon and proton beams has invoked a growing interest in the use of micro-ionization chambers. In this study, 48 PTW-TM31015 PinPoint-type micro-ionization chambers that are used in the commissioning and patient specific QA of a proton pencil beam scanning (PBS) delivery system have been characterized in proton and high-energy photon beams. In both beam modalities, the entire set of PinPoint chambers was characterized by imaging them, by evaluating their stability using check source measurements, by experimentally determining the ion recombination, polarity effect and by cross calibrating them in terms of absorbed dose to water against Farmer-type ionization chambers. Beam quality correction factors were theoretically derived for both beam modalities. None of the chambers' check source readings drifted by more than 0.5% over a one year period. Beam quality correction factors for the 6 MV photon with reference to 60Co were on average 1.0  ±  0.5% lower than the theoretical values calculated according to the data and procedures outlined in IAEA TRS-398. While this difference is within the overall dosimetric uncertainty, it is significant considering only uncorr...Continue Reading

References

Apr 4, 2003·Medical Physics·Wolfram U Laub, Tony Wong
Jul 28, 2007·Medical Physics·Otto A Sauer, Jürgen Wilbert
Jul 7, 2015·Physics in Medicine and Biology·Bernard GottschalkMiles S Wagner
May 6, 2016·Medical Physics·Jessica R MillerLarry A DeWerd
Nov 4, 2016·Medical Physics·Hugo Palmans, Stanislav M Vatnitsky
Nov 7, 2017·Zeitschrift für medizinische Physik·Markus StockStanislav Vatnitsky

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Citations

Aug 1, 2019·Physics in Medicine and Biology·S RossommeH Palmans
Dec 8, 2020·Medical Physics·Hermann FuchsDietmar Georg

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