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Investigation of signal fading in lithium formate EPR dosimeters using a new sensitive method
Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medical and Health Sciences, Division of Radiological Sciences. Linköping University, Faculty of Health Sciences.
Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics.ORCID iD: 0000-0003-0209-498X
Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Surgery, Orthopaedics and Cancer Treatment, Department of Radiation Physics. Swedish Radiation Safety Authority, Stockholm, Sweden .
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2012 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 57, no 8, 2209-2217 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to investigate signal fading in lithium formate electron paramagnetic resonance (EPR) dosimeters used for clinical applications in radiotherapy. A new experimental method for determination of signal fading, designed to resolve small changes in signal from slowly decaying unstable radicals, was used. Possible signal fading in lithium formate due to different storage temperatures was also tested. Air humidity was kept at a constant level of 33% throughout the experiments. The conclusion drawn from the investigations was that the EPR signal from lithium formate is stable during at least 1 month after irradiation and is not sensitive to variations in storage temperature andlt;40 degrees C when kept at a relative air humidity of 33%. This makes lithium formate a suitable dosimeter for transfer dosimetry in clinical audits.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2012. Vol. 57, no 8, 2209-2217 p.
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-77095DOI: 10.1088/0031-9155/57/8/2209ISI: 000302567100008PubMedID: 22456424OAI: oai:DiVA.org:liu-77095DiVA: diva2:524959
Note

Funding Agencies|Swedish Cancer foundation (CF)|100443|FORSS|86231|

Available from: 2012-05-04 Created: 2012-05-04 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Lithium formate EPR dosimetry for accurate measurements of absorbed dose in radiotherapy
Open this publication in new window or tab >>Lithium formate EPR dosimetry for accurate measurements of absorbed dose in radiotherapy
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Lithium formate has shown to be a material with properties suitable for electron paramagnetic resonance (EPR) dosimetry, among them up to 7 times higher sensitivity compared to alanine, which is a well-established EPR detector material for dose determinations in radiotherapy.

The aim of this thesis was to further investigate the properties of lithium formate and develop the dosimetry system towards applications in radiotherapy. The intrinsic efficiency for energies of relevance to brachytherapy and the signal stability were investigated. The dosimetry system was expanded to include a smaller dosimeter model, suitable for measurements in dose gradient regions. An individual sensitivity correction method was applied to the smaller dosimeters to be able to perform dose determinations with the same precision as for the larger ones. EPR dosimetry in general is time consuming and effort was spent to optimize the signal readout procedure regarding measurement time and measurement precision.

The system was applied in two clinical applications chosen for their high demands on the dosimetry system: 1) a dosimetry audit for external photon beam therapy and 2) dose verification measurements around a low energy HDR brachytherapy source.

The conclusions drawn from this thesis were: dose determinations can be performed with a standard uncertainty of 1.8-2.5% using both the original size dosimeters and the new developed smaller ones. The dosimetry system is robust and useful for applications when high measurement precision and accuracy is prioritized. It is a good candidate for dosimetry audits, both in external beam therapy and brachytherapy.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 51 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1417
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-111091 (URN)10.3384/diss.diva-111091 (DOI)978-91-7519-246-8 (ISBN)
Public defence
2014-11-06, Eken, ingång 65, plan 9, Campus US, Linköpings universitet, Linköping, 09:00 (English)
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Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2015-03-20Bibliographically approved

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