Journal Article

DKFZ-2017-06239

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Ion recombination correction factor in scanned light-ion beams for absolute dose measurement using plane-parallel ionisation chambers.

Rossomme, S. ; Horn, J. ; Brons, S. ; Jäkel, O.DKFZ* ; Mairani, A.Extern* ; Ciocca, M. ; Floquet, V. ; Romano, F. ; Rodriguez Garcia, D. ; Vynckier, S. ; Palmans, H.

2017
IOP Publ. Bristol

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Please use a persistent id in citations: doi:10.1088/1361-6560/aa730f

Abstract: Based on international reference dosimetry protocols for light-ion beams, a correction factor (k s) has to be applied to the response of a plane-parallel ionisation chamber, to account for recombination of negative and positive charges in its air cavity before these charges can be collected on the electrodes. In this work, k s for IBA PPC40 Roos-type chambers is investigated in four scanned light-ion beams (proton, helium, carbon and oxygen). To take into account the high dose-rates used with scanned beams and LET-values, experimental results are compared to a model combining two theories. One theory, developed by Jaffé, describes the variation of k s with the ionization density within the ion track (initial recombination) and the other theory, developed by Boag, describes the variation of k s with the dose rate (volume recombination). Excellent agreement is found between experimental and theoretical k s-values. All results confirm that k s cannot be neglected. The solution to minimise k s is to use the ionisation chamber at high voltage. However, one must be aware that charge multiplication may complicate the interpretation of the measurement. For the chamber tested, it was found that a voltage of 300 V can be used without further complication. As the initial recombination has a logarithmic variation as a function of 1/V, the two-voltage method is not applicable to these scanned beams.

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Contributing Institute(s):

1. E040 Med. Physik in der Strahlentherapie (E040)

Research Program(s):

1. 315 - Imaging and radiooncology (POF3-315) (POF3-315)

Appears in the scientific report 2017

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Database coverage:
; BIOSIS Previews ; Current Contents - Life Sciences ; Ebsco Academic Search ; IF < 5 ; JCR ; National-Konsortium ; Nationallizenz ; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection

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