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Adolfsson, Emelie
Publications (10 of 11) Show all publications
Adolfsson, E., White, S., Landry, G., Lund, E., Gustafsson, H., Verhaegen, F., . . . Alm Carlsson, G. (2015). Measurement of absorbed dose to water around an electronic brachytherapy source: Comparison of two dosimetry systems: lithium formate EPR dosimeters and radiochromic EBT2 film. Physics in Medicine and Biology, 60(9), 3869-3882
Open this publication in new window or tab >>Measurement of absorbed dose to water around an electronic brachytherapy source: Comparison of two dosimetry systems: lithium formate EPR dosimeters and radiochromic EBT2 film
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2015 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 60, no 9, p. 3869-3882Article in journal (Refereed) Published
Abstract [en]

Interest in high dose rate (HDR) electronic brachytherapy operating at 50 kV is increasing. For quality assurance it is important to identify dosimetry systems that can measure the absorbed doses in absolute terms which is difficult in this energy region. In this work a comparison is made between two dosimetry systems, EPR lithium formate dosimeters and radiochromic EBT2 film.

Both types of dosimeters were irradiated simultaneously in a PMMA phantom using the Axxent EBS. Absorbed dose to water was determined at distances of 10 mm, 30 mm and 50 mm from the EBS. Results were traceable to different primary standards as regards to absorbed dose to water (EPR) and air kerma (EBT2). Monte Carlo simulations were used in absolute terms as a third estimate of absorbed dose to water.

Agreement within the estimated expanded (k = 2) uncertainties (5% (EPR), 7% (EBT2)) was found between the results at 30 mm and 50 mm from the x-ray source. The same result was obtained in 4 repetitions of irradiation, indicating high precision in the measurements with both systems. At all distances, agreement between EPR and Monte Carlo simulations was shown as was also the case for the film measurements at 30mm and 50mm. At 10mm the geometry for the film measurements caused too large uncertainty in measured values depending on the exact position (within sub-mm distances) of the EBS and the 10 mm film results were exculded from comparison.

This work has demonstrated good performance of the lithium formate EPR dosimetry system in accordance with earlier experiments at higher photon energies (192Ir HDR brachytherapy). It was also highlighted that there might be issues regarding the energy dependence and intrinsic efficiency of the EBT2 film that need to be considered for measurements using low energy sources.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2015
Keywords
Electronic brachytherapy, EPR, lithium formate, radiochromic film, intrinsic efficiency
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-111090 (URN)10.1088/0031-9155/60/9/3869 (DOI)000354104700030 ()
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05Bibliographically approved
Adolfsson, E., Gustafsson, H., Lund, E., Alm Carlsson, G., Olsson, S. & Carlsson Tedgren, Å. (2014). A system for remote dosimetry audit of 3D-CRT, IMRT and VMAT based on lithium formate dosimetry. Radiotherapy and Oncology, 113(2), 279-282
Open this publication in new window or tab >>A system for remote dosimetry audit of 3D-CRT, IMRT and VMAT based on lithium formate dosimetry
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2014 (English)In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 113, no 2, p. 279-282Article in journal (Refereed) Published
Abstract [en]

The aim of this work was to develop and test a remote end-to-end audit system using lithium formate EPR dosimeters. Four clinics were included in a pilot study, absorbed doses determined in the PTV agreed with TPS calculated doses within ±5% for 3D-CRT and ±7% (k=1) for IMRT/VMAT dose plans.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Dosimetry audit; remote audit; end-to-end; EPR; ESR; lithium formate
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-111089 (URN)10.1016/j.radonc.2014.11.027 (DOI)000347657200021 ()
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05Bibliographically approved
Lund, E., Adolfsson, E., Kolbun, N. & Gustafsson, H. (2014). EPR imaging of dose distributions aiming at applications in radiation therapy. Radiation Protection Dosimetry, 159(1-4), 130-136
Open this publication in new window or tab >>EPR imaging of dose distributions aiming at applications in radiation therapy
2014 (English)In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 159, no 1-4, p. 130-136Article in journal (Refereed) Published
Abstract [en]

A one-dimensional electron paramagnetic resonance (EPR) imaging method for visualisation of dose distributions in photon fields has been developed. Pressed pellets of potassium dithionate were homogeneously irradiated in a Co-60 radiation field to 600 Gy. The EPR analysis was performed with an X-Band (9.6 GHz) Bruker E540 EPR and EPR imaging spectrometer equipped with an E540 GC2X two-axis X-band gradient coil set with gradients along the y axis (along the sample tube) and z axis (along B-0) and an ER 4108TMHS resonator. Image reconstruction, including deconvolution, baseline corrections and corrections for the resonator sensitivity, was performed using an in-house-developed Matlab code for the purpose to have a transparent and complete algorithm for image reconstruction. With this method, it is possible to visualise a dose distribution with an accuracy of similar to 5 % within +/- 5 mm from the centre of the resonator.

Place, publisher, year, edition, pages
Oxford University Press, 2014
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-109275 (URN)10.1093/rpd/ncu142 (DOI)000338829100018 ()24757173 (PubMedID)
Available from: 2014-08-12 Created: 2014-08-11 Last updated: 2017-12-05Bibliographically approved
Kolbun, N., Adolfsson, E., Gustafsson, H. & Lund, E. (2014). High-resolution mapping of 1D and 2D dose distributions using X-band electron paramagnetic resonance imaging. Radiation Protection Dosimetry, 159(1-4), 182-187
Open this publication in new window or tab >>High-resolution mapping of 1D and 2D dose distributions using X-band electron paramagnetic resonance imaging
2014 (English)In: Radiation Protection Dosimetry, ISSN 0144-8420, E-ISSN 1742-3406, Vol. 159, no 1-4, p. 182-187Article in journal (Refereed) Published
Abstract [en]

Electron paramagnetic resonance imaging (EPRI) was performed to visualise 2D dose distributions of homogenously irradiated potassium dithionate tablets and to demonstrate determination of 1D dose profiles along the height of the tablets. Mathematical correction was applied for each relative dose profile in order to take into account the inhomogeneous response of the resonator using X-band EPRI. The dose profiles are presented with the spatial resolution of 0.6 mm from the acquired 2D images; this value is limited by pixel size, and 1D dose profiles from 1D imaging with spatial resolution of 0.3 mm limited by the intrinsic line-width of potassium dithionate. In this paper, dose profiles from 2D reconstructed electron paramagnetic resonance (EPR) images using the Xepr software package by Bruker are focussed. The conclusion is that using potassium dithionate, the resolution 0.3 mm is sufficient for mapping steep dose gradients if the dosemeters are covering only +/- 2 mm around the centre of the resonator.

Place, publisher, year, edition, pages
Oxford University Press, 2014
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-109276 (URN)10.1093/rpd/ncu134 (DOI)000338829100025 ()24748487 (PubMedID)
Available from: 2014-08-12 Created: 2014-08-11 Last updated: 2017-12-05Bibliographically approved
Adolfsson, E. (2014). Lithium formate EPR dosimetry for accurate measurements of absorbed dose in radiotherapy. (Doctoral dissertation). Linköping: Linköping University Electronic Press
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. p. 51
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)
Opponent
Supervisors
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2019-11-18Bibliographically approved
Adolfsson, E., Carlsson Tedgren, Å., Alm Carlsson, G., Gustafsson, H. & Lund, E. (2014). Optimisation of an EPR dosimetry system for robust and high precision dosimetry. Radiation Measurements, 70, 21-28
Open this publication in new window or tab >>Optimisation of an EPR dosimetry system for robust and high precision dosimetry
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2014 (English)In: Radiation Measurements, ISSN 1350-4487, E-ISSN 1879-0925, Vol. 70, p. 21-28Article in journal (Refereed) 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.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
EPR; ESR; Lithium formate; High precision dosimetry; High spatial resolution dosimetry
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-111088 (URN)10.1016/j.radmeas.2014.08.013 (DOI)000345110700005 ()
Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2017-12-05Bibliographically approved
Adolfsson, E., Karlsson, M., Alm Carlsson, G., Carlsson Tedgren, Å., Lund, E., Olsson, S. & Gustafsson, H. (2012). Investigation of signal fading in lithium formate EPR dosimeters using a new sensitive method. Physics in Medicine and Biology, 57(8), 2209-2217
Open this publication in new window or tab >>Investigation of signal fading in lithium formate EPR dosimeters using a new sensitive method
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2012 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 57, no 8, p. 2209-2217Article 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
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-77095 (URN)10.1088/0031-9155/57/8/2209 (DOI)000302567100008 ()22456424 (PubMedID)
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
Fattibene, P., Wieser, A., Adolfsson, E., Benevides, L. A., Brai, M., Callens, F., . . . Zhumadilov, K. (2011). The 4th international comparison on EPR dosimetry with tooth enamel Part 1: Report on the results. Radiation Measurements, 46(9), 765-771
Open this publication in new window or tab >>The 4th international comparison on EPR dosimetry with tooth enamel Part 1: Report on the results
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2011 (English)In: Radiation Measurements, ISSN 1350-4487, E-ISSN 1879-0925, Vol. 46, no 9, p. 765-771Article in journal (Refereed) Published
Abstract [en]

This paper presents the results of the 4th International Comparison of in vitro electron paramagnetic resonance dosimetry with tooth enamel, where the performance parameters of tooth enamel dosimetry methods were compared among sixteen laboratories from all over the world. The participating laboratories were asked to determine a calibration curve with a set of tooth enamel powder samples provided by the organizers. Nine molar teeth extracted following medical indication from German donors and collected between 1997 and 2007 were prepared and irradiated at the Helmholtz Zentrum Munchen. Five out of six samples were irradiated at 0.1, 0.2, 0.5, 1.0 and 1.5 Gy air kerma; and one unirradiated sample was kept as control. The doses delivered to the individual samples were unknown to the participants, who were asked to measure each sample nine times, and to report the EPR signal response, the mass of aliquots measured, and the parameters of EPR signal acquisition and signal evaluation. Critical dose and detection limit were calculated by the organizers on the basis of the calibration-curve parameters obtained at every laboratory. For calibration curves obtained by measuring every calibration sample three times, the mean value of the detection limit was 205 mGy, ranging from 56 to 649 mGy. The participants were also invited to provide the signal response and the nominal dose of their current dose calibration curve (wherever available), the critical dose and detection limit of which were also calculated by the organizers.

Place, publisher, year, edition, pages
Elsevier, 2011
Keywords
Electron paramagnetic resonance (EPR), Tooth enamel, Detection limit, Retrospective dosimetry
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-72666 (URN)10.1016/j.radmeas.2011.05.001 (DOI)000296039300007 ()
Note
Funding Agencies|EC project SOUL|FIP6R-516478|Available from: 2011-12-02 Created: 2011-12-02 Last updated: 2017-12-08
Adolfsson, E., Alm Carlsson, G., Grindborg, J.-E., Gustafsson, H., Lund, E. & Carlsson Tedgren, Å. (2010). Response of lithium formate EPR dosimeters at photon energies relevant to the dosimetry of brachytherapy. Medical physics (Lancaster), 37(9), 4946-4959
Open this publication in new window or tab >>Response of lithium formate EPR dosimeters at photon energies relevant to the dosimetry of brachytherapy
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2010 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 37, no 9, p. 4946-4959Article in journal (Refereed) Published
Abstract [en]

PURPOSE:

To investigate experimentally the energy dependence of the detector response of lithium formate EPR dosimeters for photon energies below 1 MeV relative to that at 60Co energies. High energy photon beams are used in calibrating dosimeters for use in brachytherapy since the absorbed dose to water can be determined with high accuracy in such beams using calibrated ion chambers and standard dosimetry protocols. In addition to any differences in mass-energy absorption properties between water and detector, variations in radiation yield (detector response) with radiation quality, caused by differences in the density of ionization in the energy imparted (LET), may exist. Knowledge of an eventual deviation in detector response with photon energy is important for attaining high accuracy in measured brachytherapy dose distributions.

METHODS:

Lithium formate EPR dosimeters were irradiated to known levels of air kerma in 25-250 kV x-ray beams and in 137Cs and 60Co beams at the Swedish Secondary Standards Dosimetry Laboratory. Conversions from air kerma free in air into values of mean absorbed dose to the detectors were made using EGSnrc MC simulations and x-ray energy spectra measured or calculated for the actual beams. The signals from the detectors were measured using EPR spectrometry. Detector response (the EPR signal per mean absorbed dose to the detector) relative to that for 60Co was determined for each beam quality.

RESULTS:

Significant decreases in the relative response ranging from 5% to 6% were seen for x-ray beams at tube voltages < or = 180 kV. No significant reduction in the relative response was seen for 137Cs and 250 kV x rays.

CONCLUSIONS:

When calibrated in 60Co or MV photon beams, corrections for the photon energy dependence of detector response are needed to achieve the highest accuracy when using lithium formate EPR dosimeters for measuring absorbed doses around brachytherapy sources emitting photons in the energy range of 20-150 keV such as 169Yb and electronic sources.

Place, publisher, year, edition, pages
American Association of Physicists in Medicine, 2010
Keywords
lithium formate EPR, brachytherapy, dosimetry, detector response, kV x rays
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-59955 (URN)10.1118/1.3475938 (DOI)000281906000046 ()20964214 (PubMedID)
Available from: 2010-10-01 Created: 2010-10-01 Last updated: 2017-12-12Bibliographically approved
Adolfsson, E., Alm Carlsson, G., Grindborg, J.-E., Gustafsson, H., Lund, E. & Carlsson Tedgren, Å. (2009). Response of Lithium Formate EPR Dosimeters at Photon Energies Relelvant to Brachytherapy. In: IFMBE Proceedings: . Paper presented at World Congress on Medical Physics and Biomedical Engineering, September 7 - 12, 2009, Munich, Germany (pp. 236-239). Heidelberg: Springer Berlin Heidelberg
Open this publication in new window or tab >>Response of Lithium Formate EPR Dosimeters at Photon Energies Relelvant to Brachytherapy
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2009 (English)In: IFMBE Proceedings, Heidelberg: Springer Berlin Heidelberg , 2009, p. 236-239Conference paper, Published paper (Other academic)
Abstract [en]

After development of sensitive dosimeter materials Electron Paramagnetic Resonance EPR dosimetry has been successfully used also in radiation therapy. The intensity of the EPR-signal is a measure of the amount of free radicals created by ionizing radiation which is proportional to the absorbed dose in the dosimeter. Lithium formate monohydrate is a dosimeter material with 2-6 times higher sensitivity than alanine, a linear dose response over a wide dose range and mass-energy absorption properties similar to water. These properties make lithium formate promising for verification of absorbed doses around high dose rate brachytherapy sources where the dose gradient is steep and the photon energy distribution changing with distance from the source. Calibration of the dosimeters is performed in 60Co or MV photon beams where high dosimetric accuracy is feasible. The use in brachytherapy field relies on the assumption that the production of free radicals per mean absorbed dose in the dosimeter is similar at the lower photon energies present there. The aim of this work was to test that assumption. The response of the dosimeters as a function of photon energy was determined by irradiations with four x-ray qualities in the range 100-250 kV and 137Cs, relative to the response when irradiated with 60Co, all photon beams with well-known air kerma rates at the Swedish Secondary Standards Dosimetry Laboratory. Monte Carlo simulations were used to convert air kerma free in air to mean absorbed dose to the dosimeter. The measured response relative 60Co as a function of photon energy was below unity for all qualities. The maximum deviation from unity was 2.5% (100 kV, 135 kV) with a relative standard deviation of 1.5% (k = 1).

Place, publisher, year, edition, pages
Heidelberg: Springer Berlin Heidelberg, 2009
Series
IFMBE Proceedings, ISSN 1680-0737 ; 25/1
Keywords
HDR brachytherapy, dosimeter, EPR, lithium formate, energy response
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-59711 (URN)10.1007/978-3-642-03474-9_67 (DOI)978-3-642-03472-5 (ISBN)978-3-642-03474-9 (ISBN)
Conference
World Congress on Medical Physics and Biomedical Engineering, September 7 - 12, 2009, Munich, Germany
Available from: 2010-09-23 Created: 2010-09-23 Last updated: 2015-03-20
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