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Karlsson, Mattias
Publications (5 of 5) Show all publications
Candela-Juan, C., Karlsson, M., Lundell, M., Ballester, F. & Carlsson Tedgren, Å. (2015). Dosimetric characterization of two radium sources for retrospective dosimetry studies. Medical physics (Lancaster), 42(5), 2132-2142
Open this publication in new window or tab >>Dosimetric characterization of two radium sources for retrospective dosimetry studies
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2015 (English)In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 42, no 5, p. 2132-2142Article in journal (Refereed) Published
Abstract [en]

Purpose: During the first part of the 20th century, Ra-226 was the most used radionuclide for brachytherapy. Retrospective accurate dosimetry, coupled with patient follow up, is important for advancing knowledge on long-term radiation effects. The purpose of this work was to dosimetrically characterize two Ra-226 sources, commonly used in Sweden during the first half of the 20th century, for retrospective dose-effect studies. Methods: An 8 mg Ra-226 tube and a 10 mg Ra-226 needle, used at Radiumhemmet (Karolinska University Hospital, Stockholm, Sweden), from 1925 to the 1960s, were modeled in two independent Monte Carlo (MC) radiation transport codes: GEANT4 and MCNP5. Absorbed dose and collision kerma around the two sources were obtained, from which the TG-43 parameters were derived for the secular equilibrium state. Furthermore, results from this dosimetric formalism were compared with results from a MC simulation with a superficial mould constituted by five needles inside a glass casing, placed over a water phantom, trying to mimic a typical clinical setup. Calculated absorbed doses using the TG-43 formalism were also compared with previously reported measurements and calculations based on the Sievert integral. Finally, the dose rate at large distances from a Ra-226 point-like-source placed in the center of 1 m radius water sphere was calculated with GEANT4. Results: TG-43 parameters [including gL(r), F(r,theta), Lambda, and s(K)] have been uploaded in spreadsheets as additional material, and the fitting parameters of a mathematical curve that provides the dose rate between 10 and 60 cm from the source have been provided. Results from TG-43 formalism are consistent within the treatment volume with those of a MC simulation of a typical clinical scenario. Comparisons with reported measurements made with thermoluminescent dosimeters show differences up to 13% along the transverse axis of the radium needle. It has been estimated that the uncertainty associated to the absorbed dose within the treatment volume is 10%-15%, whereas uncertainty of absorbed dose to distant organs is roughly 20%-25%. Conclusions: The results provided here facilitate retrospective dosimetry studies of Ra-226 using modern treatment planning systems, which may be used to improve knowledge on long term radiation effects. It is surely important for the epidemiologic studies to be aware of the estimated uncertainty provided here before extracting their conclusions.

Place, publisher, year, edition, pages
American Association of Physicists in Medicine: Medical Physics, 2015
Keywords
brachytherapy; retrospective dosimetry; radium; TG-43 formalism
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-119260 (URN)10.1118/1.4916685 (DOI)000354776800005 ()25979008 (PubMedID)
Note

Funding Agencies|Generalitat Valenciana [PROMETEOII/2013/010]; Spanish Government [FIS2013-42156]; European Commission [FP7-269553]; Swedish Radiation Safety Authority [SSM 2011-2499]

Available from: 2015-06-12 Created: 2015-06-12 Last updated: 2017-12-04
Lundell, M., Karlsson, M. & Carlsson Tedgren, Å. (2015). New dosimetry for childhood skin hemangioma treatments with Ra-226 needles or tubes. Radiotherapy and Oncology, 116(1), 139-142
Open this publication in new window or tab >>New dosimetry for childhood skin hemangioma treatments with Ra-226 needles or tubes
2015 (English)In: Radiotherapy and Oncology, ISSN 0167-8140, E-ISSN 1879-0887, Vol. 116, no 1, p. 139-142Article in journal (Refereed) Published
Abstract [en]

Background: The Stockholm Hemangioma Cohort is important for evaluation of late effects after exposure to ionizing radiation during childhood. Dose estimates in this cohort were based on both measurements and calculations using an old treatment planning system. Methods: We compare previously published and calculated dose estimates with new ones, obtained by Monte Carlo simulations, which mimic the hemangioma treatments with Ra-226 needles and tubes. The distances between the Ra-226 sources and the thyroid and breasts, respectively, were reassessed. Result:. The Monte Carlo calculations showed significantly lower dose values than those obtained earlier. The differences depended both on the modeling of the sources and on further individualized distances from the sources. The mean value of the new calculated doses was 25% of the old breast doses and 46% of the old thyroid doses. Conclusion: New dosimetry for hemangioma treatments gives significantly lower organ doses for the few cases receiving the highest absorbed dose values. This implies that radiation risk estimates will increase and have to be recalculated. For retrospective studies it is now possible to calculate organ doses from radium treatments using modern treatment planning systems by modeling the source geometry carefully and apply the TG-43 formalism. It is important to be aware of the large uncertainties in calculated absorbed dose values.

Place, publisher, year, edition, pages
ELSEVIER IRELAND LTD, 2015
Keywords
Radium treatment; Hemangioma; Dosimetry; Organ doses; Children
National Category
Radiology, Nuclear Medicine and Medical Imaging
Identifiers
urn:nbn:se:liu:diva-122073 (URN)10.1016/j.radonc.2015.06.014 (DOI)000360510400024 ()26104976 (PubMedID)
Note

Funding Agencies|European Commission [FP7-269553]; Swedish Radiation Safety Authority [SSM 2011-2499]

Available from: 2015-12-18 Created: 2015-10-19 Last updated: 2017-12-01
Karlsson, M., Nilsson, J., Lundell, M. & Carlsson Tedgren, Å. (2014). Monte Carlo dosimetry of the eye plaque design used at the St. Erik Eye Hospital for I-125 brachytherapy. Brachytherapy, 13(6), 651-656
Open this publication in new window or tab >>Monte Carlo dosimetry of the eye plaque design used at the St. Erik Eye Hospital for I-125 brachytherapy
2014 (English)In: Brachytherapy, ISSN 1538-4721, E-ISSN 1873-1449, Vol. 13, no 6, p. 651-656Article in journal (Refereed) Published
Abstract [en]

PURPOSE: At St. Erik Eye Hospital in Stockholm, Sweden, ocular tumors of apical height above 6 mm are treated with brachytherapy, using iodine-125 seeds attached to a gold alloy plaque while the treatment planning is performed assuming homogeneous water surroundings. The aim of this work was to investigate the dose-modifying effects of the plaque and the seed fixating silicone rubber glue. METHODS AND MATERIALS: The impact of the gold plaque and silicone rubber glue was studied with the Monte Carlo N-particle transport code, version 5. RESULTS: For the 2 cm most proximal to the plaque surface along the plaques central axis, the eyeball received 104.6-93.0% of the dose in all-water conditions. CONCLUSIONS: The 0.3 mm thick layer of silicone rubber glue, used for seed fixation, attenuates photons little enough to allow characteristic X-rays from the gold alloy plaque to reach the eyeball. Close to the plaque, the dose rates were higher with the plaque and glue present, than in homogeneous water conditions. This is in contrast to what has been reported for more commonly used eye plaques, demonstrating the importance of investigating the dosimetry of individual treatment systems.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Eye plaque; I-125; Dosimetry; Monte Carlo simulations; Brachytherapy; Ocular melanoma
National Category
Clinical Medicine
Identifiers
urn:nbn:se:liu:diva-112619 (URN)10.1016/j.brachy.2014.05.018 (DOI)000344137000018 ()24950821 (PubMedID)
Available from: 2014-12-08 Created: 2014-12-05 Last updated: 2017-12-05Bibliographically approved
Malusek, A., Karlsson, M., Magnusson, M. & Alm Carlsson, G. (2013). The potential of dual-energy computed tomography for quantitative decomposition of soft tissues to water, protein and lipid in brachytherapy. Physics in Medicine and Biology, 58(4), 771-785
Open this publication in new window or tab >>The potential of dual-energy computed tomography for quantitative decomposition of soft tissues to water, protein and lipid in brachytherapy
2013 (English)In: Physics in Medicine and Biology, ISSN 0031-9155, E-ISSN 1361-6560, Vol. 58, no 4, p. 771-785Article in journal (Refereed) Published
Abstract [en]

Dosimetric accuracy of radiation treatment planning in brachytherapy depends on knowledge of tissue composition. It has been speculated that soft tissues can be decomposed to water, lipid and protein. The aim of our work is to evaluate the accuracy of such tissue decomposition. Selected abdominal soft tissues, whose average elemental compositions were taken from literature, were decomposed using dual energy computed tomography to water, lipid and protein via the three-material decomposition method. The quality of the decomposition was assessed using relative differences between (i) mass energy absorption and (ii) mass energy attenuation coefficients of the analyzed and approximated tissues. It was found that the relative differences were less than 2% for photon energies larger than 10 keV. The differences were notably smaller than the ones for water as the transport and dose scoring medium. The choice of the water, protein and lipid triplet resulted in negative elemental mass fractions for some analyzed tissues. As negative elemental mass fractions cannot be used in general purpose particle transport computer codes using the Monte Carlo method, other triplets should be used for the decomposition. These triplets may further improve the accuracy of the approximation as the differences were mainly caused by the lack of high-Z materials in the water, protein and lipid triplet.

Place, publisher, year, edition, pages
Institute of Physics, 2013
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-89734 (URN)10.1088/0031-9155/58/4/771 (DOI)000314396800004 ()
Note

Funding Agencies|Swedish Cancer Society (Cancerfonden)|100 512|

Available from: 2013-03-05 Created: 2013-03-05 Last updated: 2017-12-06
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
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