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Optimisation of an EPR dosimetry system for robust and high precision dosimetry
Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet.
Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.
Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Centrum för kirurgi, ortopedi och cancervård, Radiofysikavdelningen US.ORCID-id: 0000-0003-0209-498X
Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet. Östergötlands Läns Landsting, Diagnostikcentrum, Medicinsk teknik i Östergötland.
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2014 (Engelska)Ingår i: Radiation Measurements, ISSN 1350-4487, E-ISSN 1879-0925, Vol. 70, s. 21-28Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Clinical applications of electron paramagnetic resonance (EPR) dosimetry systems demand high accuracy causing time consuming analysis. The need for high spatial resolution dose measurements in regions with steep dose gradients demands small sized dosimeters. An optimization of the analysis was therefore needed to limit the time consumption. The aim of this work was to introduce a new smaller lithium formate dosimeter model (diameter reduced from standard diameter 4.5 mm to 3 mm and height from 4.8 mm to 3 mm). To compensate for reduced homogeneity in a batch of the smaller dosimeters, a method for individual sensitivity correction suitable for EPR dosimetry was tested. Sensitivity and repeatability was also tested for a standard EPR resonator and a super high Q (SHQE) one. The aim was also to optimize the performance of the dosimetry system for better efficiency regarding measurement time and precision. A systematic investigation of the relationship between measurement uncertainty and number of readouts per dosimeter was performed. The conclusions drawn from this work were that it is possible to decrease the dosimeter size with maintained measurement precision by using the SHQE resonator and introducing individual calibration factors for dosimeter batches. It was also shown that it is possible reduce the number of readouts per dosimeter without significantly decreasing the accuracy in measurements.

Ort, förlag, år, upplaga, sidor
Elsevier, 2014. Vol. 70, s. 21-28
Nyckelord [en]
EPR; ESR; Lithium formate; High precision dosimetry; High spatial resolution dosimetry
Nationell ämneskategori
Radiologi och bildbehandling
Identifikatorer
URN: urn:nbn:se:liu:diva-111088DOI: 10.1016/j.radmeas.2014.08.013ISI: 000345110700005OAI: oai:DiVA.org:liu-111088DiVA, id: diva2:753198
Tillgänglig från: 2014-10-07 Skapad: 2014-10-07 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
Ingår i avhandling
1. Lithium formate EPR dosimetry for accurate measurements of absorbed dose in radiotherapy
Öppna denna publikation i ny flik eller fönster >>Lithium formate EPR dosimetry for accurate measurements of absorbed dose in radiotherapy
2014 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

Ort, förlag, år, upplaga, sidor
Linköping: Linköping University Electronic Press, 2014. s. 51
Serie
Linköping University Medical Dissertations, ISSN 0345-0082 ; 1417
Nationell ämneskategori
Radiologi och bildbehandling
Identifikatorer
urn:nbn:se:liu:diva-111091 (URN)10.3384/diss.diva-111091 (DOI)978-91-7519-246-8 (ISBN)
Disputation
2014-11-06, Eken, ingång 65, plan 9, Campus US, Linköpings universitet, Linköping, 09:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2014-10-07 Skapad: 2014-10-07 Senast uppdaterad: 2019-11-18Bibliografiskt granskad

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Adolfsson, EmelieCarlsson Tedgren, ÅsaAlm Carlsson, GudrunGustafsson, HåkanLund, Eva

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Adolfsson, EmelieCarlsson Tedgren, ÅsaAlm Carlsson, GudrunGustafsson, HåkanLund, Eva
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Avdelningen för radiologiska vetenskaperHälsouniversitetetRadiofysikavdelningen USCentrum för medicinsk bildvetenskap och visualisering, CMIVMedicinsk teknik i Östergötland
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