Absorbed dose-to-water protocol applied to synchrotron-generated x-rays at very high dose rates

Fournier, P, Crosbie, J, Cornelius, I, Berkvens, P, Donzelli, M, Clavel, A, Rozenfeld, A, Petasecca, M, Lerch, M and Brauer-Krisch, E 2016, 'Absorbed dose-to-water protocol applied to synchrotron-generated x-rays at very high dose rates', Physics in Medicine and Biology, vol. 61, no. 14, N349-N361, pp. 349-361.

Document type: Journal Article
Collection: Journal Articles

Title Absorbed dose-to-water protocol applied to synchrotron-generated x-rays at very high dose rates
Author(s) Fournier, P
Crosbie, J
Cornelius, I
Berkvens, P
Donzelli, M
Clavel, A
Rozenfeld, A
Petasecca, M
Lerch, M
Brauer-Krisch, E
Year 2016
Journal name Physics in Medicine and Biology
Volume number 61
Issue number 14
Article Number N349-N361
Start page 349
End page 361
Total pages 13
Publisher Institute of Physics Publishing
Abstract Microbeam radiation therapy (MRT) is a new radiation treatment modality in the pre-clinical stage of development at the ID17 Biomedical Beamline of the European synchrotron radiation facility (ESRF) in Grenoble, France. MRT exploits the dose volume effect that is made possible through the spatial fractionation of the high dose rate synchrotron-generated x-ray beam into an array of microbeams. As an important step towards the development of a dosimetry protocol for MRT, we have applied the International Atomic Energy Agency's TRS 398 absorbed dose-to-water protocol to the synchrotron x-ray beam in the case of the broad beam irradiation geometry (i.e. prior to spatial fractionation into microbeams). The very high dose rates observed here mean the ion recombination correction factor, k s, is the most challenging to quantify of all the necessary corrections to apply for ionization chamber based absolute dosimetry. In the course of this study, we have developed a new method, the so called 'current ramping' method, to determine k s for the specific irradiation and filtering conditions typically utilized throughout the development of MRT. Using the new approach we deduced an ion recombination correction factor of 1.047 for the maximum ESRF storage ring current (200 mA) under typical beam spectral filtering conditions in MRT. MRT trials are currently underway with veterinary patients at the ESRF that require additional filtering, and we have estimated a correction factor of 1.025 for these filtration conditions for the same ESRF storage ring current. The protocol described herein provides reference dosimetry data for the associated Treatment Planning System utilized in the current veterinary trials and anticipated future human clinical trials.
Subject Medical Physics
Synchrotrons; Accelerators; Instruments and Techniques
Keyword(s) ion recombination
ionization chamber
microbeam radiation therapy
reference dosimetry
synchrotron radiation
DOI - identifier 10.1088/0031-9155/61/14/N349
Copyright notice © 2016 Institute of Physics and Engineering in Medicine.
ISSN 0031-9155
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